JP5886738B2 - Base station apparatus, radio communication method, and radio communication system - Google Patents

Description

  The present invention relates to a base station apparatus, a radio communication method, and a radio communication system.

  Currently, with the explosive spread of smartphones, highly convenient microwave band frequency resources are in danger of being exhausted. There is a transition from so-called third-generation mobile phones to fourth-generation mobile phones and new allocation of new frequency bands, but since there are many operators who want services, they are assigned to one operator. Frequency resources are limited. Multi-user MIMO technology has attracted attention as a technology for eliminating the tight state of frequency resources.

[About multi-user MIMO technology]
(Outline of multi-user MIMO)
Coherent transmission and phased array antenna technology are basically technologies that improve channel gain, and in order to increase the channel capacity when covering a wide service area with one base station device, another wireless communication Technology is required. On the other hand, since frequency resources are limited, here, for example, a multi-user MIMO technique studied in Non-Patent Document 1 will be described as a technique for using limited resources with high frequency utilization efficiency.
FIG. 20 is a schematic diagram illustrating a configuration example of a multi-user MIMO system. As shown in the figure, the multi-user MIMO system includes a base station device 801 and terminal devices 802-1, 802-2, and 802-3 (terminal devices # 1 to # 3). There are actually a large number of terminal devices 802 accommodated in one base station device 801, but several of these are selected (terminal devices 802-1 to 802-3 in the figure) to perform communication. Each terminal device 802 generally has a smaller number of transmission / reception antennas than the base station device 801. Below, the case where communication (downlink) from the base station apparatus 801 to the terminal device 802 is demonstrated.

  Base station apparatus 801 forms a plurality of directional beams using a large number of antenna elements. For example, consider a case where three MIMO channels are allocated to each of the terminal devices 802-1 to 803 and nine signal sequences are transmitted as a whole. At that time, the signal transmitted to the terminal device 802-1 is adjusted so that the directivity gain becomes extremely low in the direction of the terminal device 802-2 and the terminal device 802-3. As a result, the terminal device 802 2 and the terminal device 802-3. Similarly, the signal transmitted to the terminal device 802-2 is adjusted so that the directivity gain becomes extremely low in the direction of the terminal device 802-1 and the terminal device 802-3. The same processing is performed on the terminal device 802-3. The reason for performing the directivity control in this way is that, for example, in the terminal device 802-1, there is no way of knowing information of signals received by the terminal device 802-2 and the terminal device 802-3. A cooperative reception process is not possible. That is, in the reception process of only the terminal device 802-1 having only three antennas, it is very strict to separate all nine signal sequences. Therefore, interference separation is performed in advance on the transmission side so that each terminal device 802-1 to 802-3 does not receive signals from other terminal devices 802. The above is the outline of the existing multi-user MIMO system.

Next, a method for forming a directional beam will be described below. Here, a case will be described in which base station apparatus 801 includes nine antenna elements, and each terminal apparatus 802-1 to 802-3 includes three antenna elements. For example, in FIG. 20, channel information between the j-th (j = 1,..., 9) antenna element of the base station apparatus 801 and the first antenna element of the terminal apparatus 802-1 is denoted as h _1j . . Each antenna element of the base station apparatus 801 (j = 1, ..., 9) and, the first row vectors _{h 1} using the channel information of the antenna element _{(h 11} of the terminal apparatus _{802-1, h} 12, h ₁₃ ,..., H ₁₈ , h ₁₉ ). Similarly, channel information between the j-th antenna element of the base station apparatus 801 and the second antenna element and the third antenna element of the terminal apparatus 802-1 is denoted as h _2j and h _3j and corresponds. The row vectors h ₂ and h ₃ are denoted as (h ₂₁ , h ₂₂ , h ₂₃ ,..., H ₂₈ , h ₂₉ ) and (h ₃₁ , h ₃₂ , h ₃₃ ,..., H ₃₈ , h ₃₉ ). Pretend similar serial number to the antenna elements of the terminal apparatus 802-2 and the terminal device 802-3, the row vector _{h 4 ~h 9 (h 41,} h 42, h 43, ..., h 48, h 49) To (h ₉₁ , h ₉₂ , h ₉₃ ,..., H ₉₈ , h ₉₉ ).

In addition, nine systems of signals transmitted by the base station apparatus 801 are expressed as t ₁ to t ₉ , and a column vector having these components as T x ^[all] = (t ₁ , t ₂ , t ₃ ,..., T ₈ , t ₉ ) ^T Here, the letter T on the right shoulder indicates transposition of a vector or a matrix. Similarly, received signals at the nine antenna elements of the terminal devices 802-1 to 80-3 are denoted as r ₁ to r ₉ , and a column vector having these components as components Rx ^[all] = (r ₁ , r ₂ , r ₃ ,..., r ₈ , r ₉ ) ^T Finally, a matrix having the row vectors h _{1 to} h ₉ as the first to ninth row components is denoted as an overall channel information matrix H ^[all] . In addition, noise is expressed as n.
In this case, the relationship of the following formula (1) is established for the entire multiuser MIMO system.

  On the other hand, in order to perform transmission directivity control, a transmission weight matrix W of 9 rows and 9 columns is introduced, and the equation (1) is rewritten as the following equation (2).

Furthermore, the transmission weight matrix W is decomposed into column vectors _{w 1 ~w 9, W = (} w 1, w 2, w 3, ..., w 8, w 9) If the denoted ^"H in the formula (2) ^{[ all]} · W ”can be expressed as the following equation (3).

Here, for example, the multiplication of the six row vectors h _{4 to} h ₉ and the three column vectors w _{1 to} w ₃ (the sum of the multiplication of each component, which is different from the inner product in the case of a complex vector) is all zero. Consider that the values of w ₁ to w ₃ are selected. At the same time, the multiplication of the row vector _h 1 to h ₃ and _h 7 to h ₉ column vector _w 4 to w _6, multiplication becomes all zero row vector _h 1 to h ₆ column vector _w 7 to w ₉ Thus, the values of w ₄ to w ₉ are selected.
Then, the 9 × 9 matrix H ^[all] · W shown in Equation (3) can be expressed as the following Equation (4) using a 3 × 3 partial matrix.

In Equation (4), H ^[1] , H ^[2] , and H ^[3] are 3-by-3 matrices, and “0” is a 3-by-3 matrix with all components zero. By selecting a transformation matrix that satisfies such conditions as the transmission weight matrix W, the equation (4) can be decomposed into three relational expressions represented by the following equations (5-1) to (5-3).

^{_{Here, Tx [1] = (t}} 1, t 2, t 3) T, Tx [2] = (t 4, t 5, t 6) T, Tx [3] = (t 7, t 8, t ^{_{9) T, Rx [1]}} = (r 1, r 2, r 3) T, Rx [2] = (r 4, r 5, r 6) T, Rx [3] = (r 7, r 8, r ₉ ) ^T In this way, it can be considered that one base station apparatus performs MIMO communication on a one-to-one basis, that is, so-called single-user MIMO communication is communicating in three systems simultaneously in parallel.

Next, an example of a method for determining the transmission weight vectors w _{1 to} w ₉ will be described below. As a procedure, transmission weight vectors w _{1 to} w ₃ for the terminal device 802-1 are determined, and transmission weight vectors w _{4 to} w _{6 for} the terminal device 802-2 and transmission weight vectors w ₇ for the terminal device 802-3 are sequentially set. to determine the ~w _9.
First, as a first step, six basis vectors e _{4 to} e ₉ in a six-dimensional subspace spanned by six row vectors h _{4 to} h ₉ for the terminal devices 802-2 and 802-3 are obtained. There are various methods other than the Gram Schmidt orthogonalization method. The Gram Schmidt orthogonalization method will be described as an example here.
First, paying attention to one row vector h ₄ , a vector having an absolute value of 1 in this direction is set as a base vector e ₄ . The basis vector e ₄ is expressed as the following equation (6).

( ^H ₄ h ₄ ^H ) in Equation (6) is a scalar quantity that means the square of the absolute value of the same vector, and division by the square root of this value means normalization of the row vector h ₄ . “H ₄ ^H ” is a Hermitian conjugate vector for the row vector h ₄ , and is a vector obtained by transposing the row and column and taking the complex conjugate of each component.
Next, focusing on the row vector h _5, after obtaining the row vector h _{5 'canceling} the basis vectors e ₄ direction component from among the row vectors further normalized. The row vector h ₅ ′ and the basis vector e ₅ are expressed by the following expressions (7-1) and (7-2).

( ^H ₅ e ₄ ^H ) in Equation (7-1) means the projection of the row vector h _{5 in} the direction of the base vector e ₄ . The same processing is performed as in the following equation (8-1) and the following equation (8-2).

Here, the range of the summation of Σ in the equation (8-1) is the summation for the integer i of 4 ≦ i ≦ (j−1) (j is an integer of 5 to 9). That is, it means that the component in the defined vector direction that has already been determined is canceled. In this way, six basis vectors e _{4 to} e ₉ can be obtained.
Next, as a second step, transmission weight vectors w _{1 to} w ₃ for the terminal device 802-1 are obtained. First, the components of the 6-dimensional subspace spanned by the base vectors e _{4 to} e ₉ are canceled from the row vectors h _{1 to} h ₃ . Specifically, it is represented by the following formula (9).

Here, j in the formula (9) is an integer of 1 to 3, and the range of the sum of Σ is the sum for the integer i of 4 ≦ i ≦ 9. The three-dimensional space spanned by the three vectors of the row vectors h ₁ ′ to h ₃ ′ thus obtained is orthogonal to any of the above-described row vectors h _{4 to} h ₉ . If three vectors in this three-dimensional space (not necessarily an orthogonal vector) are selected and the complex conjugate vector of the vector is set as transmission weight vectors w _{1 to} w ₃ , another terminal device 802-2, Interference with 802-3 can be suppressed.

Note that any method may be used for selecting the three vectors. For example, if three orthogonal vectors that form a unitary matrix obtained by performing singular value decomposition are used, the sub-spaces that do not interfere with other terminal devices 802 are used. The eigenmode transmission limited to 1 is possible, and efficient transmission becomes possible.
Finally, as a third step, if the same processing is performed for the terminal device 802-2 and the terminal device 802-3, finally the entire transmission weight vectors w _{1 to} w ₉ can be obtained. .
The above is how to obtain the transmission weight matrix W.

FIG. 21 is a flowchart showing a procedure for calculating a transmission weight matrix W in the multiuser MIMO system. First, in calculating the transmission weight matrix W, channel information matrices H for all the terminal devices 802 are acquired (step S801). When a serial number is assigned to the destination terminal device 802 and the variable indicating the serial number is k, k is first initialized (step S802). Further, k is counted up (step S803), and partial channel information (herein expressed as H ^main for convenience) corresponding to the terminal device 802 (# 1) corresponding to the current value indicated by k is extracted (step S804). ), And a partial channel information matrix (indicated here as H ^sub for convenience) for the other terminal device 802 is extracted (step S805).

Further, an orthogonal basis vector of a subspace spanned by each row vector of the partial channel matrix H ^sub is calculated, and this is set as a basis vector {e _j } (step S806). Next, as processing corresponding to Equation (9), the component related to the basis vector {e _j } obtained in step S806 from the partial channel information matrix H ^main for the terminal device 802 (# 1) of interest is canceled, Is a matrix to H ^main (step S807). Here, in step S807, H with “˜ (tilde)” added thereto is denoted as “˜H”. Hereinafter, similarly, in a mathematical expression or the like, when a character such as “^ (hat)” is written on the character, the symbol is written before the character.

Further, an arbitrary orthogonal basis vector of the subspace spanned by the row vectors of the matrix to H ^main is calculated, and this is set as the basis vector {e _i } (step S808). Here, as the arbitrary base vector, for example, a vector constituting the right singular matrix when the matrix ~ H ^main is subjected to singular value decomposition may be selected. Thereafter, a transmission weight vector {w _j } relating to the signal of the terminal device 802 (# 1) is determined as a Hermitian conjugate vector (a column vector obtained by transposing the complex conjugate vector) of each vector of the basis vector {e _i } (step S809). ).

Here, it is determined whether or not the transmission weight vectors of all destination terminal devices 802 have been determined (step S810), and if there are remaining terminal devices 802, the processing from step S803 to step S809 is repeated. If the transmission weight vectors of all the terminal devices 802 have been determined, the transmission weight matrix W is determined as a matrix having the transmission weight vector {w _j } as each column vector (step S811), and the process ends.

Since channel information generally differs for each frequency component, if a wideband signal, for example, a signal using the OFDM modulation method, a similar transmission weight is calculated for each frequency component, that is, for each subcarrier. Become. Here, since the case where each of the terminal devices 802-1 to 802-3 includes three antennas has been described, in step S808, the orthogonal basis vector of the subspace spanned by each row vector of the matrix to H ^main is calculated. In the case where the terminal device includes only one antenna, step S808 simply corresponds to normalizing a row vector corresponding to the matrix ~ H ^main .

  The above is a general multi-user MIMO transmission / reception weight calculation method. Assuming that a plurality of antennas are provided on the terminal device side, the entire channel matrix is expressed as shown in equation (4). It is a method of keratinization. However, there are several other variations of similar transmission / reception weight calculation methods. These variations do not necessarily require a single antenna for the terminal device, but for the sake of simplicity, the following description will be given assuming that N terminal devices with a single antenna are spatially multiplexed simultaneously. A method for calculating other transmission / reception weights will be described below.

First, regarding the transmission / reception weights of the base station apparatus 801, ZF (10-1) and (10-2) represented by the following equations (10-1) and (10-2) with respect to the entire channel matrix H ^[all] shown in equation (1) and the like A pseudo inverse matrix of the “Zero Forcing” type may be calculated and used as a transmission weight and a reception weight.

Here, assuming that the number of terminal devices to be spatially multiplexed is N and the number of antenna elements of the base station device 801 is K (N <K), for example, the size of the channel matrix H ^[all] is as follows for the downlink. N × K (N rows and K columns). If the rank of H ^[all] is N, the matrix H ^[all] · H ^{[all] H has} a size of N × N and an inverse matrix exists, and a pseudo inverse matrix is obtained using equation (10-1). be able to. In general, if the value of K is sufficiently redundant with respect to N, the rank of this N × N matrix is stably N, and the inverse matrix exists stably. Similarly, for the uplink reception weight corresponding to reception by the base station apparatus 801, the size of the channel matrix H ^[all] is K × N (K rows and N columns), and the matrix H ^{[all] H} · H ^{[ all]} also becomes N × N, and generally there is an inverse matrix. A ZF type pseudo inverse matrix expressed by the following equation (10-2) may be calculated and used as a reception weight. .
In the MMSE weight known as a similar transmission / reception weight, if the noise power is σ ² , the following expressions (11-1) and (11-2) are converted into expressions (10-1) and (10): -2) may be used instead. Note that “I” in Equations (11-1) and (11-2) is an N × N (N rows and N columns) unit matrix.

(Multi-user MIMO device configuration example)
FIG. 22 is a schematic block diagram illustrating an example of the configuration of the base station device 80 in the multiuser MIMO system. As shown in the figure, the base station apparatus 80 includes a transmission unit 81, a reception unit 85, an interface circuit 87, a MAC layer processing circuit 88, and a communication control circuit 820. The MAC layer processing circuit 88 has a scheduling processing circuit 881.
The base station apparatus 80 inputs / outputs data to / from an external device or network via the interface circuit 87. The interface circuit 87 detects data to be transferred on the wireless line among the input data, and outputs the detected data to the MAC layer processing circuit 88. The MAC layer processing circuit 88 performs processing related to the MAC layer in accordance with an instruction from the communication control circuit 820 that performs management control of the operation of the entire base station apparatus 80. Here, the processing related to the MAC layer includes conversion of data input / output by the interface circuit 87 and data transmitted / received on the wireless line, addition of header information of the MAC layer, and the like. In this process, the scheduling processing circuit 881 performs various scheduling processes including a combination of terminal devices that simultaneously perform spatial multiplexing in multiuser MIMO transmission. The scheduling processing circuit 881 outputs the scheduling result to the communication control circuit 820. In multi-user MIMO, signals are transmitted to a plurality of terminal devices at a time, so that a plurality of signal sequences are output from the MAC layer processing circuit 88 to the transmission unit 81.

  FIG. 23 is a schematic block diagram illustrating an example of the configuration of the transmission unit 81 in the base station apparatus 80 in the multiuser MIMO system. As shown in the figure, the transmission unit 81 includes transmission signal processing circuits 811-1 to 811-L (L is an integer of 2 or more) and addition synthesis circuits 812-1 to 812-K (K is an integer of 2 or more). ), IFFT (Inverse Fast Fourier Transform) & GI (Guard Interval) assigning circuits 813-1 to 813 -K, and D / A (digital / analog) converters 814-1 to 814- K, local oscillator 815, mixers 816-1 to 816-K, filters 817-1 to 817-K, high power amplifiers (HPA) 818-1 to 818-K, and antenna elements 819-1 to 819. -K and a transmission weight processing unit 830. Transmission signal processing circuits 811-1 to 811-L and transmission weight processing unit 830 are connected to communication control circuit 820 shown in FIG.

  The transmission weight processing unit 830 includes a channel information acquisition circuit 831, a channel information storage circuit 832, and a multiuser MIMO (MU-MIMO) transmission weight calculation circuit 833. Here, the subscript L of the transmission signal processing circuits 811-1 to 811-L in FIG. The subscript K of the circuits from the adder / synthesizer circuit 812-1 to 812-K to the antenna elements 819-1 to 819-K represents the number of antenna elements included in the base station apparatus 80.

  In multi-user MIMO, in order to transmit signals to a plurality of terminal devices at a time, a plurality of signal sequences are input from the MAC layer processing circuit 88 to the transmission unit 81, and the input plurality of signal sequences are transmitted signal processing. Input to the circuits 811-1 to 811-L. The transmission signal processing circuits 811-1 to 811-L, when data to be transmitted to each destination terminal device (data input # 1 to #L) are input from the MAC layer processing circuit 88, wireless transmission is performed via a wireless line. A packet is generated and modulated. Here, for example, if the OFDM modulation method is used, the signal of each signal series is subjected to modulation processing for each frequency component. Further, the baseband signal subjected to modulation processing is multiplied by a transmission weight for each frequency component. The signal multiplied by the transmission weight corresponding to each of the antenna elements 819-1 to 819 -K is subjected to the remaining signal processing as necessary, and is added and synthesized as a sampling signal of the transmission signal in the baseband 812-1. 812-K.

  The signals input to the adder / synthesizers 812-1 to 812-K are synthesized for each frequency component. The synthesized signal is converted from a signal on the frequency axis into a signal on the time axis by IFFT & GI adding circuits 83-1 to 813-K, and further, a guard interval is inserted or between OFDM symbols (block for SC-FDE). (Between transmission blocks) is processed, and for each antenna element 819-1 to 819-K, a D / A converter 814-1 to 814-K converts a digital sampling data into a baseband analog signal. Is converted to Further, each analog signal is multiplied by the local oscillation signal input from the local oscillator 815 by the mixers 816-1 to 816-K and up-converted to a radio frequency signal. Here, since the signal is included in the frequency component outside the band of the channel to be transmitted in the up-converted signal, the frequency component outside the band is removed by the filters 817-1 to 817-K, and the electrical signal to be transmitted is transmitted. A typical signal. The generated signals are amplified by the high power amplifiers 818-1 to 818 -K and transmitted from the antenna elements 819-1 to 819 -K.

  In FIG. 23, after adding and synthesizing the signals of the respective frequency components by the adding and synthesizing circuits 812-1 to 812-K, processing such as IFFT processing, insertion of guard intervals, waveform shaping, and the like is performed. The signal processing circuits 811-1 to 811-L may perform these processes, and the IFFT & GI giving circuits 83-1 to 813-K may be omitted. In this case, the remaining signal processing as necessary after transmission weight multiplication in the transmission signal processing circuits 811-1 to 811-L refers to IFFT processing, insertion of guard intervals, waveform shaping, and the like.

  Further, the transmission weights multiplied by the transmission signal processing circuits 811-1 to 811-L are acquired from the multiuser MIMO transmission weight calculation circuit 833 provided in the transmission weight processing unit 830 at the time of signal transmission processing. In the transmission weight processing unit 830, channel information is separately acquired by the channel information acquisition circuit 831 and stored in the channel information storage circuit 832 while being updated sequentially. At the time of signal transmission, the multiuser MIMO transmission weight calculation circuit 833 reads channel information corresponding to the destination station from the channel information storage circuit 832 and calculates a transmission weight based on the read channel information. Multi-user MIMO transmission weight calculation circuit 833 outputs the calculated transmission weight to transmission signal processing circuits 811-1 to 811-L.

  Further, the communication control circuit 820 manages control related to the entire communication such as management of the destination station and overall timing control. The communication control circuit 820 outputs information indicating the destination station and the like to the transmission weight processing unit 830 that performs signal processing related to the calculation of the transmission weight described above.

  FIG. 24 is a schematic block diagram illustrating an example of the configuration of the reception unit 85 in the base station apparatus 80 in the multiuser MIMO system. As shown in the figure, the receiving unit 85 includes antenna elements 851-1 to 851-K, low noise amplifiers (LNA) 852-1 to 852-K, a local oscillator 853, and mixers 854-1 to 854-K. Filters 855-1 to 855-K, A / D (analog / digital) converters 856-1 to 856-K, and FFT (Fast Fourier Transform) circuits 857-1 to 857-K. Reception signal processing circuits 858-1 to 858 -L and a reception weight processing unit 860. Reception signal processing circuits 858-1 to 858 -L and reception weight processing unit 860 are connected to communication control circuit 820 shown in FIG. 22. Reception weight processing section 860 includes channel information estimation circuit 861 and multiuser MIMO (MU-MIMO) reception weight calculation circuit 862.

  Signals received by the antenna elements 851-1 to 851-K are amplified by the low noise amplifiers 852-1 to 852-K. The amplified signal and the local oscillation signal output from the local oscillator 853 are multiplied by mixers 854-1 to 854-K, and the amplified signal is down-converted from a radio frequency signal to a baseband signal. Since the down-converted signal includes frequency components outside the frequency band to be received, the out-of-band components are removed by the filters 855-1 to 855-K. The signal from which the out-of-band component is removed is converted into a digital baseband signal by the A / D converters 856-1 to 856-K. All digital baseband signals are input to FFT circuits 857-1 to 857 -K, and signals on the time axis are converted into signals on the frequency axis (separated into signals of each frequency component) at a predetermined symbol timing. The signals separated into the frequency components are input to the reception signal processing circuits 858-1 to 858 -L and also input to the channel information estimation circuit 861.

  In the channel information estimation circuit 861, the antenna element of each terminal device and the base station device 80 based on a known signal for channel estimation separated into each frequency component (such as a preamble signal added to the head of the radio packet). Channel information between each of the antenna elements 851-1 to 851-K is estimated for each frequency component, and the estimation result is output to the multiuser MIMO reception weight calculation circuit 862. Multi-user MIMO reception weight calculation circuit 862 calculates reception weights to be multiplied for each frequency component based on the input channel information. At this time, reception weights for synthesizing signals received by the antenna elements 851-1 to 851-K are different for each signal series, and reception signal processing circuits 858-1 to 858-L corresponding to the signal series to be extracted. Input to each.

  In the reception signal processing circuits 858-1 to 858 -L, the signal for each frequency component input from the FFT circuits 857-1 to 847 -K is multiplied by the reception weight input from the multiuser MIMO reception weight calculation circuit 862. Then, the signals received by the antenna elements 851-1 to 851-K are added and synthesized for each frequency component. The reception signal processing circuits 858-1 to 858 -L perform demodulation processing on the added and combined signals and output the reproduced data to the MAC layer processing circuit 88.

  Here, different received signal processing circuits 858-1 to 858 -L perform signal processing of different signal sequences. The MAC layer processing circuit 88 performs processing related to the MAC layer (for example, conversion between data input / output to / from the interface circuit 87 and data transmitted / received on the wireless line, termination of header information of the MAC layer, etc.). Do. In this process, the scheduling processing circuit 881 performs various scheduling processes including a combination of terminal apparatuses that simultaneously perform spatial multiplexing in multiuser MIMO transmission, and outputs a scheduling result to the communication control circuit 820. The received data processed by the MAC layer processing circuit 88 is output to an external device or network via the interface circuit 87.

In addition, the communication control circuit 820 manages control related to overall communication such as management of a transmission source terminal device and overall timing control. In addition, information indicating a transmission source terminal device or the like is input from the communication control circuit 820 to the reception weight processing unit 860 that performs signal processing related to the calculation of the reception weight described above.
As for signal reception, as in the case of transmission, in the wideband system using the OFDM modulation scheme or SC-FDE scheme, the above-described reception weight multiplication is performed for each frequency component. That is, the signals output from the A / D converters 856-1 to 856-K are subjected to FFT in the FFT circuits 857-1 to 857-K and separated into frequency components, and channel information is obtained for each separated frequency component. The signal processing in the estimation circuit 861 and the reception signal processing in the reception signal processing circuits 858-1 to 858 -L are performed.

(Multi-user MIMO transmission processing)
FIG. 25 is a flowchart showing a transmission process of the base station apparatus 80 in multiuser MIMO. In multi-user MIMO, feedback of downlink channel information, which is performed separately from data transmission, is periodically performed. When the channel information acquisition circuit 831 acquires channel information in the downlink (step S831), the channel information storage circuit 832 stores the channel information of each frequency component for each terminal device (step S832). The processes in step S831 and step S832 are performed sequentially.

When signal transmission processing from the base station apparatus 80 is started (step S821), the multiuser MIMO transmission weight calculation circuit 833 obtains channel information of each frequency component corresponding to the terminal apparatus that is the destination from the channel information storage circuit 832. Read (step S822).
Based on the read channel information, the multiuser MIMO transmission weight calculation circuit 833 calculates a transmission weight for multiuser MIMO for each frequency component by the processing described above (step S823). Separately from the processing of step S822 and step S823, the transmission signal processing circuits 811-1 to 811-L perform each frequency for each destination station by performing transmission signal processing such as various modulation processing on the data to be transmitted for each destination. A component transmission signal is generated (step S824).

  The transmission signal processing circuits 811-1 to 811-L multiply the generated transmission signal by the transmission weight calculated by the multiuser MIMO transmission weight calculation circuit 833 in step S823 (step S825). The transmission signal processing circuits 811-1 to 811-L perform a series of signal processing, and the adder / synthesizing circuits 812-1 to 812-L each terminal device of each frequency component for each of the antenna elements 819-1 to 819-L. Addition synthesis is performed on the transmission signal addressed to the signal, and the IFFT & GI adding circuits 83-1 to 813-K convert the signal on the frequency axis to the signal on the time axis, and further insert a guard interval or between OFDM symbols (SC- If it is FDE, it performs processing such as waveform shaping between the blocks in the block transmission) and outputs it to the D / A converters 814-1 to 814-K (steps S826-1 to S826-K).

The signals output from the IFFT & GI adding circuits 813-1 to 813 -K are subjected to signal processing in the high power amplifiers 818-1 to 818 -K from the D / A converters 814-1 to 814 -K, and the antenna element 819. -1 to 819-K (steps S827-1 to S827-K), and the process ends (steps S828-1 to S828-K).
Note that the processing in steps S827-1 to S827-K includes up-conversion processing from a baseband signal to a radio frequency, removal of frequency components of a band by a filter, signal amplification by a high power amplifier, and the like.

(Multi-user MIMO reception processing)
FIG. 26 is a flowchart showing reception processing of the base station apparatus 80 in multiuser MIMO. First, when reception processing is started (step S840), signals are received by the first to Kth antenna elements 851-1 to 851-K (steps S841-1 to S841-K). Here, reception includes processing for performing analog / digital conversion on a received signal or a signal obtained by down-converting the received signal. Subsequent signal processing means processing on a digitized received signal.

  Subsequently, the received signals corresponding to the antenna elements 851-1 to 851-K are subjected to signal processing such as separation into frequency components by the FFT circuits 857-1 to 857-K (steps S842-1 to S842). -K). Furthermore, the channel information estimation circuit 861 performs channel estimation of each frequency component based on the reception state of the preamble signal having a known pattern attached to the wireless packet (steps S843-1 to S843-K). Here, the attenuation of the signal on the propagation path and the rotation state of the complex phase are grasped. In the channel estimation performed in steps S843-1 to S843-K, channel estimation is individually performed for each spatially multiplexed signal sequence, as shown in steps S843-1, S843-2,. Need to do. This individual channel estimation needs to be performed in a state in which the signals transmitted from the respective transmission source terminal devices can be separated. Taking the OFDM modulation method as an example, generally, a preamble signal for channel estimation having the same number of symbols as the number of spatial multiplexing is required. Each terminal apparatus performs signal transmission with the same number of symbols as the number of spatial multiplexing (or more) and assigns a different pattern of preamble signals, and the base station apparatus 80 uses the difference in pattern to perform step transmission. Individual channel estimation is performed in S843-1 to S843-K.

  The multiuser MIMO reception weight calculation circuit 862 uses the channel information estimated by the channel information estimation circuit 861 to calculate individual appropriate reception weights for each spatially multiplexed signal sequence and each frequency component (step S844). Further, the reception signal processing circuits 858-1 to 858 -L multiply the reception signal calculated for each signal series and each frequency component by the reception signal of each antenna element separated for each frequency component (step S <b> 845-). 1-S845-K).

  Here, since reception weights are prepared for each spatially multiplexed signal sequence, the multiplication results in steps S845-1 to S845-K are different results for each spatially multiplexed signal sequence. The signals of the respective signal sequences are obtained by adding and synthesizing the signals of the antenna elements 851-1 to 851-K for each frequency component (steps S846-1 to S846-L). Processing from signal sequence signal processing (step S847-1) to signal processing of the Lth signal sequence (step S847-L) is performed, and the processing ends (steps S848-1 to S848-L).

  Here, for the sake of simplicity, an example in which a linear reception weight is used is shown, but in general, nonlinear signal processing such as MLD (Maximum Likelihood Detection) may be performed for MIMO. In this case, the processes in steps S845-1 to S845-L, steps S846-1 to S846-L, and steps S847-1 to S847-L are integrally performed with nonlinear signal detection processing. Further, the linear reception weight can be calculated by a method similar to the transmission weight calculation process shown in FIG. In addition, it is also possible to use a reception weight using a pseudo inverse matrix or an MMSE weight. Here, the number of spatially multiplexed signal sequences is described as L for the number K of antenna elements 851-1 to 851-K used for reception, but in general, K and L need to match. If the value of L is equal to or less than the value of K, a number of signal series signals can be spatially multiplexed.

Yasushi Takatori et al., "Application of downlink multi-user MIMO technology to next-generation high-speed wireless access systems" IEICE Transactions B, Communication J93-B (9), pp 1127-1139, September 2010

In the above description of multi-user MIMO, the description has been focused on the case where the number of spatial multiplexing is the same as the number of antennas of the base station apparatus. There is no. Actually, in equations (10-1) and (10-2) and equations (11-1) and (11-2), the number of antennas is K and the number of spatial multiplexing (the same number as the number of terminal devices with one antenna). ) Was described as L. In this case, the matrix size of the entire channel matrix H ^[ALL] is L × K or K × L. In this case, if the Gram Schmitt orthogonalization process as described above is performed, the weight is calculated. Requires K × L × (L + 1) multiplication operations. If the values of L and K are L = 2 and K = 32, the number of multiplications is 192. Looking at the number of multiplications per se, it does not matter so much as the circuit scale that can be mounted in the LSI.

  However, Gram Schmidt's orthogonalization processing is not deterministic because the amount of computation changes depending on the size of the target matrix, and it is not a problem if it is a software processing, but in real time in a short time If the hardware is used to complete the matrix operation, the construction becomes difficult as the number of antennas K increases. On the other hand, in the case where the transmission / reception weight is calculated in a format such as formulas (10-1), (10-2) and formulas (11-1), (11-2) with deterministic processing, By implementing the inverse matrix formula as it is, it can be realized in hardware. However, in this case, the number of multiplications increases as compared to the Gram Schmidt orthogonalization.

Specifically, taking equation (10-1) as an example, the matrix size of the channel matrix H ^[ALL] is L × K, and therefore L ² × K in the operation (H ^[ALL] · H ^{[ALL] H} ). Multiple “multiplications” are required. In order to calculate the inverse matrix of the L × L square matrix obtained after this, “multiplication” of the order of L ³ times is generally required. Finally, L ² × K times “multiplication” is required for the operation of H ^{[ALL] H} and the above inverse matrix. When these are summed, the number of multiplications is 2 × L ² × K + L ³ . If the values of L and K are L = 2 and K = 32, the number of multiplications is 264.

  In general, the circuit scale of a multiplication circuit is larger than that of an addition circuit or the like, and the circuit scale greatly increases when an arithmetic process requiring a large number of multiplication circuits is involved. For this reason, in order to suppress the circuit scale of the arithmetic processing related to the transmission / reception weight calculation, it has been necessary to operate so as not to make the number of antennas excessively redundant with respect to the number of spatial multiplexing. However, this increase in the number of antennas has the effect of reducing the correlation of channel vectors between each terminal apparatus and the base station apparatus. Generally, if the number of antennas is redundant, it is said that the characteristics are good as long as it is redundant. Yes.

  The present invention has been made in view of such a situation, and provides a base station apparatus, a wireless communication method, and a wireless communication system that can suppress an increase in computation load caused by an increase in the number of antenna elements. is there.

  In order to solve the above problem, the present invention comprises a base station apparatus having a plurality of antenna elements and a plurality of terminal apparatuses, and the base station apparatus and the terminal apparatus are at the same time on the same frequency. A base station apparatus in a radio communication system capable of performing spatial multiplexing transmission, wherein the radio signal receiver is provided for each antenna element and separates a received signal received by the antenna element into a signal for each frequency component; Receiving weight for each frequency component for acquiring uplink channel information based on the training signal transmitted from the terminal device and combining the signals received by the plurality of antenna elements based on the channel information in phase A vector is calculated for each combination of the antenna element of the terminal device and the plurality of antenna elements of the base station device, and the reception weight vector A reception weight vector calculation unit to store, and for each of the terminal devices performing spatial multiplexing transmission, the reception weight vector of each frequency component corresponding to the terminal device among the reception weight vectors calculated by the reception weight vector calculation unit, A plurality of first reception signal processing units that multiply the signals separated into each frequency component by the radio signal reception unit and add and combine the multiplication results, and a plurality of the first reception signal processing units are added and combined. A base station apparatus comprising: a second received signal processing unit that suppresses an interference component included in a signal using a received weight matrix calculated based on the calculated signal of each frequency component. .

  In the present invention described above, the second received signal processing unit may convert the signal of each frequency component calculated by addition synthesis by the plurality of first received signal processing units to a spatial multiplexing number. Considering a signal received by a virtual antenna element, channel information between the virtual antenna element and the antenna element of the terminal device performing spatial multiplexing transmission is calculated, and the reception weight matrix is calculated based on the calculated channel information. Is calculated.

  In the invention described above, the present invention provides a transmission signal generation unit that separates each signal transmitted to the plurality of terminal devices into signals for each frequency component, and a training signal received from the terminal device or the terminal Each frequency for acquiring downlink channel information based on any of the information fed back from the device and combining the signals transmitted from the plurality of antenna elements based on the channel information in the terminal device A component transmission weight vector is calculated for each combination of the antenna element of the terminal device and a plurality of antenna elements of the base station device, and a transmission weight vector calculation unit that stores the transmission weight vector, and a plurality of the terminal devices Mutual interference components are suppressed in the terminal device to which each of the transmission signals to be spatially multiplexed is destined A second transmission signal processing unit that multiplies the signal for each frequency component separated by the transmission signal generation unit by the transmission weight matrix determined to be transmitted, and for each terminal device that is a destination in spatial multiplexing transmission, Of the frequency component signals calculated by multiplication by the second transmission signal processing unit, each frequency component signal destined for the terminal device is duplicated corresponding to the antenna element, and the terminal is copied to the duplicated signal. A first transmission signal processing unit that multiplies a transmission weight vector of each frequency component corresponding to a combination of an antenna element of the apparatus and a plurality of antenna elements of the base station apparatus, and is provided for each of the antenna elements. The signal of each frequency component calculated by multiplication by the transmission signal processing unit is a signal corresponding to the antenna element, and the destination terminal device in the spatial multiplexing transmission The issue synthesized and characterized a radio signal transmitter for transmitting as said transmission signal from said antenna elements, further comprising.

  Further, the present invention is the above-described invention, wherein the second transmission signal processing unit uses a matrix obtained by transposing the reception weight matrix calculated by the second reception signal processing unit as the transmission weight matrix. It is characterized by using.

  Further, the present invention provides the transmission weight for calculating the transmission weight matrix based on a value obtained by multiplying the transmission weight vector by the vector configured by the downlink channel information in the above-described invention. A matrix calculation unit is further provided.

  In addition, the present invention includes a base station apparatus including a plurality of antenna elements and a plurality of terminal apparatuses, and the base station apparatus and the terminal apparatus perform spatial multiplexing transmission at the same time on the same frequency. A radio communication method performed by a base station apparatus in a radio communication system capable of receiving a radio signal, the radio signal receiving step being provided for each antenna element and separating a received signal received by the antenna element into a signal for each frequency component; Receive weight vectors for each frequency component for acquiring uplink channel information based on the training signal transmitted from the terminal apparatus and synthesizing signals received by the plurality of antenna elements based on the channel information. Is calculated for each combination of the antenna element of the terminal device and the plurality of antenna elements of the base station device, and the reception weight vector is calculated. For each terminal device that performs spatial multiplexing transmission, a reception weight vector for each frequency component corresponding to the terminal device among the reception weight vectors calculated in the reception weight vector calculation step is stored for each terminal device that performs spatial multiplexing transmission. A first received signal processing step of multiplying the signal separated into each frequency component in the radio signal receiving step, and adding and combining the multiplication results, and calculating by addition combining in the first received signal processing step And a second received signal processing step of suppressing an interference component included in the signal using a reception weight matrix calculated based on a signal of each frequency component.

  In addition, the present invention includes a base station apparatus including a plurality of antenna elements and a plurality of terminal apparatuses, and the base station apparatus and the terminal apparatus perform spatial multiplexing transmission at the same time on the same frequency. The base station apparatus is provided for each antenna element and separates a received signal received by the antenna element into a signal for each frequency component, and the terminal apparatus The terminal obtains a reception weight vector for each frequency component for acquiring uplink channel information based on the training signal transmitted from the base station and combining the signals received by the plurality of antenna elements based on the channel information in phase. A reception weight that is calculated for each combination of an antenna element of the apparatus and a plurality of antenna elements of the base station apparatus and stores the reception weight vector For each of the terminal devices that perform spatial multiplexing transmission, a vector calculation unit, and a reception weight vector of each frequency component corresponding to the terminal device among the reception weight vectors calculated by the reception weight vector calculation unit, the radio signal reception unit A plurality of first received signal processing units that multiply the signals separated into frequency components by the above and add and combine the multiplication results, and each frequency calculated by the plurality of first received signal processing units by addition synthesis A radio communication system comprising: a second received signal processing unit that suppresses an interference component included in a signal using a received weight matrix calculated based on the component signal.

According to the present invention, the first reception signal processing unit extracts a spatially multiplexed signal using a reception weight vector calculated in advance, and an interference component included in the signal based on the extracted signal Are suppressed in the second received signal processing unit. Thereby, even when the number of antenna elements provided in the base station apparatus is increased, it is possible to suppress an increase in calculation load in accordance with the increase in the number of antenna elements.
As a result, the channel vector correlation between the terminal devices is reduced by increasing the number of antenna elements of the base station device. As a result, even if a plurality of terminal devices are spatially multiplexed, the orthogonalization loss at that time is greatly increased. It is possible to achieve a stable spatial multiplexing characteristic. On the other hand, the calculation load of receiving weight vector calculation is the same as in the case of non-redundant number of antennas, that is, it is possible to stably expect desired characteristics while suppressing the circuit scale and reducing hardware impact. It is possible to provide a base station apparatus that can be used. At this time, even when there is some channel time variation in channel information between the base station device and the terminal device, by using a reception weight matrix that follows the time variation, stable multiuser MIMO can be obtained even in an environment with time variation. Spatial multiplexing processing is possible.

It is a schematic block diagram which shows the structure of the base station apparatus 10 in one Embodiment which concerns on this invention. It is a schematic block diagram which shows an example of a structure of the receiving part 100 with which the base station apparatus 10 in the embodiment is provided. It is a schematic block diagram which shows the structural example of the average transmission / reception weight calculation part 120 in the embodiment. It is a schematic block diagram which shows the structural example of the 1st received signal processing circuit 191-j in the embodiment. It is a schematic block diagram which shows the structural example of the 2nd received signal processing circuit 192 in the embodiment. It is a flowchart which shows the reception process of the base station apparatus 10 in the embodiment. It is a schematic block diagram which shows the structural example of the transmission part 140 with which the base station apparatus 10 in the embodiment is provided. It is a schematic block diagram which shows the structural example of the 2nd transmission signal processing circuit 194 in the embodiment. It is a schematic block diagram which shows the structure of the 1st transmission signal processing circuit 193-j (1 <= j <= L) in the embodiment. It is a flowchart which shows the transmission process which the base station apparatus 10 in the embodiment performs. 4 is a flowchart showing a relative component acquisition process for acquiring a relative component of uplink channel information in the embodiment. 6 is a flowchart showing another relative component acquisition process for acquiring a relative component of uplink channel information in the embodiment. 6 is a flowchart showing an averaging process of uplink channel information in the embodiment. It is a flowchart which shows the process which acquires the channel information of the downlink in the embodiment. It is a flowchart which shows the process which calculates the average reception weight vector in the base station apparatus 10 of the embodiment. It is a schematic block diagram which shows the structure as the modification 1 of the base station apparatus 10 of embodiment which concerns on this invention. It is a schematic block diagram which shows the structure of the average transmission / reception weight calculation part 120a in the modification 2 of embodiment which concerns on this invention. 10 is a flowchart showing a process of calculating an average transmission weight vector in Modification 2. It is a figure which shows another example of the training signal used for the average transmission / reception weight calculation in this invention. It is the schematic which shows the structural example of a multiuser MIMO system. It is a flowchart which shows the procedure which calculates the transmission weight matrix W in a multiuser MIMO system. It is a schematic block diagram which shows an example of a structure of the base station apparatus 80 in a multiuser MIMO system. It is a schematic block diagram which shows an example of a structure of the transmission part 81 in the base station apparatus 80 in a multiuser MIMO system. It is a schematic block diagram which shows an example of a structure of the receiving part 85 in the base station apparatus 80 in a multiuser MIMO system. It is a flowchart which shows the transmission process of the base station apparatus 80 in multiuser MIMO. It is a flowchart which shows the reception process of the base station apparatus 80 in multiuser MIMO. It is a figure which shows the example of installation of the base station apparatus with which the radio | wireless communications system which concerns on this invention comprises. It is a figure which shows the operation example of the signal synthesis | combination which the base station apparatus which concerns on this invention performs. It is a figure which shows the asymmetry of the channel information of an uplink and a downlink. It is a figure which shows the outline | summary of calibration.

[Operational principle of the present invention]
In the present invention, a base station device that is fixedly installed at a high place and includes a plurality of antenna elements and a system that includes a large number of terminal devices that are fixedly installed at a relatively high place are assumed. The channel information between the antennas of the station apparatus and the terminal apparatus is premised on that there is a strong temporal correlation to some extent, although temporal fluctuations are involved. However, if this time correlation condition is satisfied, that is, if the speed of time fluctuation of channel information is relatively slow with respect to the feedback period of channel information, the terminal device does not necessarily have to be fixedly installed at a high place. The present invention can also be applied to general terminal devices.

FIG. 27 is a diagram illustrating an installation example of the base station apparatus included in the wireless communication system according to the present invention. In the same figure, the code | symbol 11 shows the building in which the base station apparatus is installed, the code | symbols 12-1 to 12-2 shows a terminal device, and the code | symbols 13-1 to 13-4 are equipped with the base station apparatus. An antenna element is shown, the code | symbol 14-1 to 14-3 shows the mobile body on the ground, and the code | symbols 15-1 to 15-2 have shown the large sized building (naturally a stationary state).
Here, the antenna elements 13-1 to 13-4 of the base station apparatus are installed in a very high place such as the roof of the building 11. The terminal devices 12-1 to 12-2 may be relatively lower than the antenna elements 13-1 to 13-4 of the base station device such as a telephone pole or a general building rooftop. However, it is installed at a relatively high place. On the other hand, the mobile units 14-1 to 14-3 on the ground are located in places relatively lower than the antenna elements 13-1 to 13-4 and the terminal devices 12-1 to 12-2 of the base station apparatus. In addition to cars, there are many starting points (reflective points) of reflected waves that fluctuate randomly, such as people and trees swaying in the wind.

  For example, the terminal device 12-1 and the antenna elements 13-1 to 13-4 of the base station device are in a line-of-sight environment (direct waves are indicated by thick solid arrows in the figure). On the other hand, although the terminal device 12-2 and the antenna elements 13-1 to 13-4 of the base station device are not in the line-of-sight environment due to the shielding of the large building 15-2, the large building 15-1 or the like And a stable reflected wave (indicated by a thick solid arrow in the figure) has reached. In addition, for the terminal device 12-1 in the line-of-sight environment, there may be a situation where a stable reflected wave due to a large building exists in addition to the line-of-sight wave, and these signals are always combined to reach the signal. A signal represented by such a thick solid arrow is regarded as a stable incident wave. On the other hand, the reflected waves from the mobile bodies 14-1 to 14-3 on the ground have many signals that arrive as many random multiple reflections, and the level of the signal received is relatively low, and the complex phase component And the amplitude varies randomly with time.

  When a number of weak and random waves are combined, the resulting signal has a relatively low signal strength relative to a stable incident wave. Therefore, the “time-varying incident wave” obtained by combining the “stable incident wave” with the “random multiple reflected wave” is a signal in which a minute error is added around the “stable incident wave”. Can see.

Next, signal synthesis performed by the base station apparatus in such a situation will be described.
FIG. 28 is a diagram illustrating an operation example of signal synthesis performed by the base station apparatus according to the present invention. Here, as an example, when signals transmitted from terminal apparatus 12-1 in FIG. 27 are received by antenna elements 13-1 to 13-4 of the base station apparatus, they are combined using appropriate reception weights. Shows the case.

  The antenna elements 13-1 to 13-4 of the base station apparatus receive the “incident wave that varies with time”. The reception weight used when combining these signals is determined so that the signals at the respective antenna elements are combined in phase with the “stable incident wave” as a reference. The signal indicated by the dotted line in FIG. 28 is a signal in which the “stable incident wave” is multiplied by the reception weight, and the phase is made the same by the antenna elements 13-1 to 13-4 of the base station apparatus. is there.

  The actual “time-varying incident wave” multiplied by the reception weight, that is, the “time-varying incident wave” indicated by a thin solid line in FIG. 28 is slightly shifted from the “stable incident wave” indicated by the dotted line. Strictly speaking, each antenna element does not have the same phase composition, but the “time-varying incident wave” behaves close to a “stable incident wave”. When combined using the reception weight set with “stable incident wave” as a reference, a combined signal having a large amplitude indicated by a thick solid line is obtained. In other words, if the number of antenna elements used in the base station apparatus is increased to an enormous number, the “stable incident wave” component of each antenna element is in-phase synthesized as a statistical effect, and the “random multiple reflected wave” is In order to cancel each other, the time-varying component with respect to the “stable incident wave” is relatively suppressed to a very small level.

Here, in the description of FIG. 27 and FIG. 28, the case where the base station apparatus is provided with four antenna elements has been described for the sake of simplicity. A statistical effect can be obtained by providing the antenna element.
Here, when the number of antenna elements provided in the base station apparatus is K, the amplitude of a signal to be combined in phase is K times and the received power is K ² times. That is, when there are two terminal devices A and B, if the reception weight that realizes the same phase synthesis of the terminal device A is applied to the signal transmitted by the terminal device A, the received power per one is K ² times the received power. At the same time, when the terminal apparatus B is transmitting signals by spatial multiplexing, the signal from the terminal apparatus B can only be random phase combining even if the reception weight for realizing the same phase combining of the terminal apparatus A is applied. In addition, the received power is only K times the received power per line. If K = 100, since the desired signal is 10,000 times and the interference signal is 100 times, the relative power difference is 100 times, and a SIR of 20 dB can be realized. However, in practice, in order to increase the number of antenna elements, RF circuits, A / D converters, D / A converters, and digital signal processing units such as FFTs connected to the antenna circuit are arranged by the number of antenna elements. Therefore, it is anticipated that the number of antenna elements must be kept low due to business profitability. In this case, since sufficient SIR characteristics cannot be ensured, it is necessary to apply a transmission / reception weight for null control for removing mutual interference signals similar to the case of multi-user MIMO here.

  However, since the time variation of channel information between the plurality of antenna elements of the base station device and each terminal device is limited, the transmission / reception weight itself for in-phase synthesis does not change greatly. Therefore, the following processing is performed with the number of antenna elements being K and the number of spatial multiplexing being L systems. In general, a relationship of L << K (L is sufficiently small with respect to K) is established.

First, taking the reception process as an example, the K dimension for synthesizing in-phase signals from each terminal device calculated based on channel information acquired before transmission / reception of actual signals (communication data) Are multiplied by the K signal series received via all antenna elements, and then added and synthesized. At this time, the multiplication of the K-dimensional weight vector with respect to the K-system signal sequence is performed for each terminal apparatus as a transmission source. As a result, L signal series are generated. This means that a signal sequence corresponding to a signal received by virtual L antenna elements is generated.
This weight vector may be a weight vector for in-phase synthesis generated based on the channel information acquired from the terminal device corresponding to the last, and if considering the effect of time fluctuation, A weight vector generated based on channel information averaged over a period may be used.

  In the present invention, a (transmission) reception weight for performing in-phase synthesis on antenna elements that are significantly more redundant than the number of signal systems that are actually spatially multiplexed, and spatial multiplexing on the premise of in-phase synthesis. There are two concepts of (transmission / reception weight), which will be described later (transmission / reception weight) in a relatively small dimension narrowed down to the number of signal systems. In the following description, in order to distinguish these two for convenience, it is a transmission / reception weight for performing in-phase synthesis for a large number of antenna elements. Generally, channel information obtained by averaging in time. The (transmission) reception weight obtained based on the above will be described as an “averaged (transmission) reception weight vector”. However, for convenience, the term “averaging” is used, but the averaging processing is not necessarily required in the present invention. The main intention of “averaging” here is that the normal MIMO transmission signal processing requires a transmission / reception weight matrix that is updated in real time using the latest channel information. The reception weight vector does not require real-time characteristics, which means that it is possible to tolerate errors due to channel time variations. For this reason, as a general embodiment, it is assumed that an averaged (transmission / reception) reception weight vector is used for the purpose of suppressing a random minute displacement.

Here, since the average received weight vector is a weight vector for maximizing the gain of each terminal device, the leakage of mutual interference signals remains between the virtual antennas defined by the average received weight vector. Has been. Accordingly, virtual channel information between the L signal series and the virtual antenna can be represented by a matrix of size L × L corresponding to this leakage. However, since the desired signal has a high gain by the in-phase synthesis and the other interference signals have a low gain by the random phase synthesis, there is a relative difference between the diagonal component and the non-diagonal component in the L × L matrix. A gain difference of about ₁₀ Log ₁₀ (K) [dB] can be expected. That is, since the L L-dimensional channel vectors have a small correlation with each other and are generally orthogonal, the L × L square matrix has a stable inverse matrix. Since it is further L << K, the inverse matrix operation can be calculated with a relatively small amount of calculation (the order of L ^3).

  If L = 2, if the inverse matrix formula is used, the multiplication of the determinant is performed twice, and further, the division of the four matrix components is divided by the determinant when the division is performed four times. The processing is completed by a total of 6 multiplications (or the same for division). This is a reduction in the amount of computation that cannot be compared with the orthogonalization of Gramschmitt or computations in the forms such as equations (10-1), (10-2), and equations (11-1), (11-2). is there. As a result, by performing the process of multiplying the averaged reception weight vector in advance, a reception weight matrix for performing L-system signal separation in real time at the time of signal reception can be obtained by a very simple process. . Hereinafter, this (transmission) reception weight matrix for performing L-system signal separation in real time will be referred to as a “real-time (transmission) reception weight matrix”, and the above described average (transmission) reception weight vector will be described. Distinguish.

The calculation of the real-time reception weight matrix can be acquired by the following process, for example. First, a virtual channel matrix L × L acquired averaging receiving weight vector after multiplying the H _v. Since this matrix is a square matrix, the simplest ZF in the case of (Zero-Forcing) signal processing of real-time reception weight matrix W _R is given by the following equation.

In the case of treatment of MMSE-type in consideration of the noise, real-time reception weight matrix W _R may be given by the following equation.

In Expression (13), σ ² represents noise power, and the matrix I represents a unit matrix having a size of L × L.
The above is the processing on the receiving side, but this processing can be similarly applied to transmission. Specifically, if appropriate averaged reception weight vector and averaged transmission weight vector are applied, the reception characteristics of the low-noise amplifier on the reception side in the uplink and the transmission side high-frequency in the downlink are included in these weights. Includes calibration factors described below to compensate for asymmetry between uplink and downlink due to power amplifier transmission characteristics, and this asymmetry between uplink and downlink should be canceled . Therefore, the real-time virtual channel matrix indicating the characteristics of the virtual channel when a virtual antenna is assumed is symmetric between the uplink and the downlink, and each has a relationship in which the respective matrices are transposed. That is, the downlink virtual channel matrix H ^(DL) matches {H _v } ^T obtained by transposing the uplink virtual channel matrix H _v . Therefore, the real-time transmission weight matrix used at the time of transmission is given by the following equation (14).

Similarly, real-time transmission weight matrix W _T corresponding to formula (13) can be modified as the following equation (15).

That is, in the case of obtaining the real-time reception weight matrix W _R using any form of Equation (12) through (13) also corresponding real-time transmission weight matrix W _T is by transposing the real-time reception weight matrix W _R Can be obtained.
Therefore, if the reception weight matrix generated at the time of reception as described above is stored together with the combination of the terminal devices combined by spatial multiplexing at that time, when the spatial weight multiplexing is performed and transmitted to the terminal device of the same combination The same effect can be obtained by using a transposition of the latest real-time reception weight matrix for the combination as a real-time transmission weight matrix.

In this way, transmission and reception weight multiplication is performed in two stages on both the transmission side and the reception side, and one of them uses an average transmission / reception weight vector that allows errors due to channel time fluctuations, and follows channel time fluctuations. The matrix calculation for suppressing the interference can be performed by calculating the L × L size real-time transmission / reception weight matrix for the spatially multiplexed L signal series.
In the following, a calibration process will be described as a related technique of the present invention before the embodiment of the present invention is described.

[Effects of individual amplifier differences (calibration)]
In an actual wireless communication apparatus, in signal processing on the transmission side, signal amplification is often performed by a high power amplifier immediately before transmission. In this case, there is an error in the amplification factor due to the individual difference of the high power amplifier, and the complex phase may rotate at a different value for each high power amplifier in the high power amplifier. Similarly, in signal processing on the reception side, signal amplification is often performed by a low noise amplifier immediately after reception. In this case, there is an error in the amplification factor due to individual differences of the low noise amplifiers, and the complex phase may rotate with a different value for each low noise amplifier in the low noise amplifier.

  In particular, the amplification factor and phase rotation amount of the high power amplifier and the low noise amplifier have frequency dependency. If the individual difference in the amplification factor with frequency dependency and the amount of rotation of the complex phase is so large that it cannot be ignored, it is necessary to perform calibration processing when estimating the downlink channel information from the uplink channel information. is there. Since the error of the amplification factor and the amount of phase rotation is almost stable in time, measure the error of the amplification factor and the amount of phase rotation in advance, and use a coefficient to cancel the influence of the error. Converts link channel information to downlink channel information.

  In a wireless communication apparatus according to the following related technology, an average transmission weight vector and an average reception weight vector are calculated using uplink channel estimation results. Also in the above description, the amplitude and the complex phase may actually be changed by a high power amplifier or a low noise amplifier (strictly speaking, a transmission system and a reception system circuit including other circuits such as a filter). In this case, it has been described that a calibration coefficient for correcting in accordance with a change in amplitude or complex phase is acquired in advance and used for correction. Although a known technique may be used for the calibration process, an example of the calibration process will be described below.

FIG. 29 is a diagram illustrating asymmetry of channel information between the uplink and the downlink. In the figure, reference numerals 25-1 to 25-3 denote wireless modules, reference numerals 21-1 to 21-3 denote high power amplifiers (HPA), and reference numerals 22-1 to 22-3 denote low noise amplifiers (LNA). Reference numerals 23-1 to 23-3 denote time division switches (TDD-SW), and reference numerals 24-1 to 24-3 denote antenna elements.
Here, since only functions that affect channel information are extracted in the wireless communication apparatus, configurations other than those illustrated are omitted, but the wireless modules 25-1 to 25-3 include other functions. Further, when the signal passes through each of the high power amplifiers 21-1 to 21-3, the amplitude and the complex phase are Z _{HPA # 1} (f _k ), Z _{HPA # 2} (f _k ), Z _{HPA # 3} (f _k ). Further, when the signal passes through each of the low noise amplifiers 22-1 to 22-3, the amplitude and the complex phase are Z _{LNA # 1} (f _k ), Z _{LNA # 2} (f _k ), and Z _{LNA # 3} (f _k ). Here, it is assumed that there is a frequency dependency as a general condition, and the frequency “(f _k )” for the k-th frequency component is described.

Here, for example, channel information when signals are transmitted from the wireless module 25-1 and the wireless module 25-2 to the test wireless module 25-3 will be described. Here, spatial channel information between the antenna element 24-1 of the wireless module 25-1 and the antenna element 24-3 of the wireless module 25-3 is represented by h ₁ (f _k ). In addition, channel information in the space between the antenna element 24-2 of the wireless module 25-2 and the antenna element 24-3 of the wireless module 25-3 is represented by h ₂ (f _k ).

At this time, the channel information when the signal is actually transmitted from the wireless module 25-1 to the wireless module 25-3 indicates a change accompanying the passage of the high power amplifier 21-1 at h ₁ (f _k ) in space. A coefficient Z _{HPA # 1} (f _k ) and a coefficient Z _{LNA # 3} (f _k ) indicating a change accompanying the passage through the low noise amplifier 22-3 are observed as multiplied values.
Similarly, the channel information when transmitting a signal from the wireless module 25-2 to the wireless module 25-3 is a coefficient Z indicating a change accompanying passage of the high power amplifier 21-2 at h ₂ (f _k ) in space. _{HPA # 2} (f _k ) and a coefficient Z _{LNA # 3} (f _k ) indicating a change accompanying passage through the low noise amplifier 22-3 are observed as multiplied values.

Therefore, the channel from the wireless module 25-1 to the wireless module 25-3 is represented by Z _{HPA # 1} (f _k ) · h ₁ (f _k ) · Z _{LNA # 3} (f _k ). A channel from the wireless module 25-2 to the wireless module 25-3 is represented by Z _{HPA # 2} (f _k ) · h ₂ (f _k ) · Z _{LNA # 3} (f _k ). Therefore, in addition to the difference between the channel information h ₁ (f _k ) and h ₂ (f _k ), the wireless module 25-1 and the wireless module 25-2 have relatively Z _{HPA # 2} (f _k ) / Z _{HPA # 1} (f _k ) difference occurs.

This situation is the same on the receiving side. When the signal transmitted from the wireless module 25-3 is received by the wireless module 25-1, the channel information is stored in the high power amplifier 21 in h ₁ (f _k ) in space. Observed as a value obtained by multiplying the coefficient Z _{HPA # 3} (f _k ) indicating the change accompanying the passage of −3 and the coefficient Z _{LNA # 1} (f _k ) indicating the change accompanying the passing of the low noise amplifier 22-1 Is done.
Similarly, when the signal transmitted from the wireless module 25-3 is received by the wireless module 25-2, the channel information changes in space h ₂ (f _k ) due to the passage of the high power amplifier 21-3. It is observed as a value obtained by multiplying the indicated coefficient Z _{HPA # 3} (f _k ) by the coefficient Z _{LNA # 2} (f _k ) indicating the change accompanying the passage of the low noise amplifier 22-2.

Therefore, the channel from the wireless module 25-3 to the wireless module 25-1 is represented by Z _{HPA # 3} (f _k ) · h ₁ (f _k ) · Z _{LNA # 1} (f _k ). A channel from the wireless module 25-3 to the wireless module 25-2 is represented by Z _{HPA # 3} (f _k ) · h ₂ (f _k ) · Z _{LNA # 2} (f _k ). Therefore, in addition to the difference between the channel information h ₁ (f _k ) and h ₂ (f _k ), the wireless module 25-1 and the wireless module 25-2 have relatively Z _{LNA # 2} (f _k ) / Z _{LNA # 1} (f _k ) difference occurs.
As described above, the wireless communication device according to the related art takes a long-time average with respect to the received training signal, thereby including a channel including a change caused by the low noise amplifiers 22-1 to 22-3 connected to each antenna element. Information can be acquired on the uplink.

However, the wireless communication apparatus cannot directly obtain channel information in the downlink. Therefore, downlink channel information is obtained by conversion from uplink channel information. For this conversion, the influence of individual differences between the low-noise amplifiers 22-1 to 22-3 and the high-power amplifiers 21-1 to 21-3 connected to the antenna elements 24-1 to 24-3 is canceled. There is a need.
Therefore, in the manufacturing stage of the wireless communication device, a test wireless module 25-3 serving as a reference is prepared, and the antenna terminal of the test wireless module 25-3 and the antenna terminals of the wireless modules 25-1 and 25-2 are prepared. And channel information including changes by the high power amplifiers 21-1 to 21-3 and the low noise amplifiers 22-1 to 22-3 are measured in an environment where the channel information on the propagation path is a common value. Then, correction is performed using the measured channel information.

FIG. 30 is a diagram showing an outline of calibration. In the figure, reference numerals 26-1 to 26-3 indicate antenna terminals, and reference numeral 27 indicates a coaxial cable. In addition, the same code | symbol is attached | subjected to the function part same as the function part shown in FIG.
FIG. 30A illustrates a configuration in which the wireless module 25-3 and the wireless module 25-1 are connected by a coaxial cable. FIG. 30B illustrates a configuration in which the wireless module 25-3 and the wireless module 25-2 are connected by a coaxial cable. FIG. 29 shows a state in which a signal propagates in an actual space, whereas FIG. 30 shows a state in which a signal propagates on a coaxial cable without passing through an antenna element.

The channel information of the coaxial cable 27 serving as a propagation path connecting the wireless modules 25-1 and 25-2 and the wireless module 25-3 is h ₀ (f _k ).
At this time, the channel information from the wireless module 25-1 to the wireless module 25-3 is expressed by Z _{HPA # 1} (f _k ) · h ₀ (f _k ) · Z _{LNA # 3} (f _k ). The channel information from the wireless module 25-2 to the wireless module 25-3 is expressed by Z _{HPA # 2} (f _k ) · h ₀ (f _k ) · Z _{LNA # 3} (f _k ).
Further, the channel information from the wireless module 25-3 to the wireless module 25-1 is represented by Z _{HPA # 3} (f _k ) · h ₀ (f _k ) · Z _{LNA # 1} (f _k ), and the wireless module 25 -3 to the wireless module 25-2 is represented by Z _{HPA # 3} (f _k ) · h ₀ (f _k ) · Z _{LNA # 2} (f _k ).
Therefore, after measuring these channel information, calibration coefficients C ₁ (f _k ) and C ₂ (f _k ) represented by the following equations (16) and (17) are calculated.

The channel information from the wireless module 25-3 to the wireless module 25-1 is represented by Z _{HPA # 3} (f _k ) · h ₁ (f _k ) · Z _{LNA # 1} (f _k ), and the wireless module 25- It has been described that the channel information from 3 to the wireless module 25-2 is represented by Z _{HPA # 3} · (f _k ) · h ₂ (f _k ) · Z _{LNA # 2} (f _k ). When these are multiplied by the calibration coefficients C ₁ (f _k ) and C ₂ (f _k ) of the equations (16) and (17), the following equations (18) and (19) are obtained.

The right sides of Expression (18) and Expression (19) are the channel information from the wireless module 25-1 to the wireless module 25-3 and the channel information from the wireless module 25-2 to the wireless module 25-3 described above. It matches.
As described above, the calibration coefficients corresponding to the equations (16) and (17) are acquired in the manufacturing stage of the wireless communication device, and stored in the wireless communication device, thereby calibrating them. The downlink channel information can be calculated from the uplink channel information using the coefficient.

  In the following embodiment, these calibration coefficients are acquired in advance, and the description will be made mainly on the case where the values are used in digital signal processing.Naturally, these calibration coefficients are displayed on an analog circuit. If all adjustments are made within the wireless communication device so that all values are almost constant (the absolute value itself may be different if the complex phase is constant), all calibration coefficients are It can also be read as a process regarded as 1. Similarly, even when the complex phases of the uplink and downlink are adjusted to be constant values, as a result, the complex phases of the calibration coefficients expressed by the equations (16) and (17) are all Since the antenna element has a substantially constant value, the same effect can be obtained.

[Specific Embodiment of the Present Invention]
Hereinafter, specific embodiments according to the present invention will be described with reference to FIGS. 1 to 19.

(Configuration of base station apparatus in one embodiment)
FIG. 1 is a schematic block diagram illustrating a configuration of a base station apparatus 10 according to an embodiment of the present invention. As shown in the figure, the base station apparatus 10 includes a receiving unit 100, a transmitting unit 140, an averaged transmission / reception weight calculation unit 120, a real-time transmission weight matrix storage unit 130, an interface circuit 170, a MAC layer processing circuit 180, and a communication control circuit. 110 and a memory circuit 115. The MAC layer processing circuit 180 has a scheduling processing circuit 181.
The base station apparatus 10 inputs and outputs data with an external device or a network via the interface circuit 170. The interface circuit 170 detects data to be transferred on the wireless line among the input data, and outputs the detected data to the MAC layer processing circuit 180. The MAC layer processing circuit 180 performs processing related to the MAC layer in accordance with an instruction from the communication control circuit 110 that performs management control of the operation of the entire base station apparatus 10. Here, the processing related to the MAC layer includes conversion of the format and the like for the data input / output by the interface circuit 170 and the data transmitted / received on the wireless line, and the addition of the MAC layer header information. In this process, the scheduling processing circuit 181 performs various scheduling processes including a combination of terminal apparatuses that simultaneously perform spatial multiplexing. The scheduling processing circuit 181 outputs the scheduling result to the communication control circuit 110.

  In the spatial multiplexing transmission, a signal is transmitted to a plurality of terminal devices at a time at the time of transmission, so that a plurality of signal sequences are output from the MAC layer processing circuit 180 to the transmission unit 140. In reception, a plurality of signal sequences transmitted from a plurality of terminal devices are output from the receiving unit 100 to the MAC layer processing circuit 180. The averaged transmission / reception weight calculation unit 120 manages an averaged reception weight vector and an averaged transmission weight vector used when the reception unit 100 and the transmission unit 140 perform spatial multiplexing and transmission / reception of data. The real-time transmission weight matrix storage unit 130 stores and manages a real-time transmission weight matrix used when the transmission unit 140 transmits data by spatial multiplexing.

The storage circuit 115 stores in advance various information (for example, SNR information, information on the degree of time variation, information on the optimum transmission mode, etc.) of each terminal device in the wireless communication system. Information such as the SNR information and optimum transmission mode of the terminal device stored in the storage circuit 115 is used when scheduling is performed. Note that the memory circuit 115 is not necessarily required in both the present embodiment and the related technology, and may be omitted in some cases.
Hereinafter, the configuration (reception unit 100) related to reception (uplink) in the base station apparatus 10 and the configuration (transmission unit 140) related to transmission (downlink) will be described separately.

(Configuration of receiving unit of base station apparatus in this embodiment)
FIG. 2 is a schematic block diagram illustrating an example of a configuration of the receiving unit 100 included in the base station device 10 according to the present embodiment. As shown in the figure, the receiving unit 100 includes antenna elements 101-1 to 101-K, TDD switches 102-1 to 102-K, low noise amplifiers (LNA) 103-1 to 103-K, a local oscillator 104, a mixer. 105-1 to 105-K, filters 106-1 to 106-K, A / D converters 107-1 to 107-K, FFT circuits 108-1 to 108-K, and first received signal processing circuits 191-1 to 191-1. 191-L and a second received signal processing circuit 192 are provided.

  The second received signal processing circuit 192 and the TDD switches 102-1 to 102-K are connected to the communication control circuit 110 shown in FIG. Further, the FFT circuits 108-1 to 108-K and the first reception signal processing circuits 191-1 to 191-L are connected to the averaged transmission / reception weight calculation unit 120 shown in FIG. The second received signal processing circuit 192 is connected to the real-time transmission weight matrix storage unit 130 shown in FIG. Antenna elements 101-1 to 101-K correspond to antenna elements 13-1 to 13-4 of the base station apparatus in FIG. In this embodiment, the description is made on the premise of the TDD system, but in principle, the present invention can be extended to the FDD system.

  The base station apparatus 10 of this embodiment includes A / D converters 107-1 to 107-K from TDD switches 102-1 to 102-K corresponding to the K antenna elements 101-1 to 101-K, respectively. The circuits up to are provided in parallel. FFT circuits 108-1 to 108-K are connected to the outputs of the A / D converters 107-1 to 107-K. In order to estimate downlink channel information from uplink channel information, the same antenna elements 101-1 to 101-K are used for transmission and reception. The TDD switches 102-1 to 102-K switch the flow of transmission signals and reception signals.

  The TDD switches 102-1 to 102-K output the signals received via the antenna elements 101-1 to 102-K to the low noise amplifiers 103-1 to 103-K. The low noise amplifiers 103-1 to 103-K amplify the signals output from the TDD switches 102-1 to 102-K and output the amplified signals to the mixers 105-1 to 105-K. The local oscillator 104 generates a local oscillation signal having a predetermined frequency, and outputs the generated local oscillation signal to each of the mixers 105-1 to 105-K. Here, the local oscillation signals input to the mixers 105-1 to 105-K are the same signal, and the local oscillation signals having the same frequency and phase are input to the mixers 105-1 to 105-K.

  The mixers 105-1 to 105-K multiply the signals input from the low noise amplifiers 103-1 to 103-K by the local oscillation signal input from the local oscillator 104, down-convert them, and perform filters 106-1. 106-K. Filters 106-1 to 106-K remove signals outside the band of the channel to be received, included in the signals down-converted by mixers 105-1 to 105-K, and A / D converters 107-1 to 107-. Output to K. The A / D converters 107-1 to 107-K digitize the baseband signals input from the filters 106-1 to 106-K.

  When input from the A / D converters 107-1 to 107-K, the FFT circuits 108-1 to 108-K separate the digital baseband signal into signals for each frequency component. At this time, the FFT circuits 108-1 to 108-K remove the guard interval for each OFDM signal (or block transmission block) for each frequency component signal, and perform FFT processing on the remaining sampling data. The signal on the time axis is converted into a signal on the frequency axis, and the signal is output to the first reception signal processing circuits 191-1 to 191-L. Further, the FFT circuits 108-1 to 108-K also output the signals to the average transmission / reception weight calculation unit 120.

  The averaged transmission / reception weight calculation unit 120 receives an instruction from the communication control circuit 110 as to whether or not the digital baseband signal input from the FFT circuits 108-1 to 108-K has a timing corresponding to the training signal. If it is a training signal, processing such as acquisition, averaging, and storage of an average transmission / reception weight vector with the terminal device designated by the communication control circuit 110 is performed. Details of the training signal for channel estimation will be described later. The processes in the first received signal processing circuits 191-1 to 191-L and the second received signal processing circuit 192 shown below are all calculated, processed, recorded, and managed for each frequency component.

  Each of the first received signal processing circuits 191-1 to 191-L is associated with a terminal device or a spatially multiplexed signal sequence that transmits a signal using spatial multiplexing. The first reception signal processing circuits 191-1 to 191-L calculate signals for each terminal device corresponding to the L system from reception signals corresponding to K antennas with L << K.

  Specifically, the first reception signal processing circuits 191-1 to 191-L input averaged reception weight vectors corresponding to the transmission source terminal devices assigned thereto from the average transmission / reception weight calculation unit 120, respectively. The first reception signal processing circuits 191-1 to 191-L obtain the input average reception weight vector for each frequency component with respect to the signals separated into the frequency components by the FFT circuits 108-1 to 108-K. Multiply. The first received signal processing circuits 191-1 to 191-L are signals corresponding to the antenna elements 101-1 to 101-K, which are signals obtained by addition and synthesis, and signals obtained by addition synthesis. Is output to the second received signal processing circuit 192.

  However, the signal sequences calculated by the first reception signal processing circuits 191-1 to 191-L are not in a state in which the mutual interference signals can be completely suppressed, but in a state in which the mutual residual interference remains. 2 The received signal processing circuit 192 performs further signal processing for signal separation, and performs signal detection processing in a state where residual interference is sufficiently suppressed.

  In the second reception signal processing circuit 192, the reception timing of the training signal arranged at the head portion of the signal input from the first reception signal processing circuits 191-1 to 191-L is grasped by an instruction from the communication control circuit 110. . The second received signal processing circuit 192 uses this training signal to acquire channel information of each frequency component related to the L-system signal sequence after addition synthesis. Each of the L system signal sequences generated using the averaged reception weight vector corresponds to a signal sequence received by one virtual antenna corresponding to the averaged reception weight vector. In other words, by acquiring channel information between the antenna of the terminal device of the L station and the virtual L antennas, a channel matrix of each frequency component having a size of L × L can be acquired. On the other hand, signal separation is possible by using a matrix having a relatively small size.

  Signal separation processing in the second received signal processing circuit 192 is a ZF-type inverse matrix using Equation (12), an MMSE-type signal processing similarly using Equation (13), or non-linear. Signal processing such as MLD (Maximum Likelihood Detection) may be used. Hereinafter, for the sake of simplicity, a case where a ZF-type inverse matrix is used will be described.

First, the second received signal processing circuit 192 obtains an inverse matrix of an L × L square matrix by using Equation (12) for each frequency component, and uses this as a real-time received weight matrix. The second received signal processing circuit 192 performs signal separation by multiplying an L system signal sequence (processing as an L-dimensional vector having L components) of each frequency component following the training signal by an inverse matrix. . The second received signal processing circuit 192 performs signal detection processing on the separated signal series and outputs the obtained data outputs # 1 to #L to the MAC layer processing circuit 180.
Note that the real-time reception weight matrix obtained using equation (12) or the like can also be used as a real-time transmission weight matrix in the transmission processing, and therefore, this is output to the real-time transmission weight matrix storage unit 130, Record it. At this time, combination information of the terminal devices simultaneously spatially multiplexed is also recorded.

Specifically, the signal detection processing performed by the second received signal processing circuit 192 performs demodulation processing for each subcarrier when the OFDM (A) modulation method is used, and SC-FDE is used. Is subjected to signal equalization processing on the frequency axis, and demodulation processing is performed on a signal obtained by synthesizing the signal by IFFT processing. In this demodulation processing, temporary signal detection is performed by hard decision processing or soft decision processing based on the constellation corresponding to the applied modulation method, and further, error correction decoding processing is performed as necessary, and data is output. To do.
The signal processing on the MAC layer in the MAC layer processing circuit 180 is the same as the processing using a known technique, and the description is omitted here.

  When the first reception signal processing circuits 191-1 to 191-L perform signal processing in the above processing, it is necessary to use different average reception weight vectors for each transmission source terminal device. The communication control circuit 110 manages overall control related to a series of communications. In particular, the communication control circuit 110 manages which terminal device receives a signal at which timing and which average received weight vector is used. Therefore, the access control between the base station apparatus 10 and the terminal apparatus in the present embodiment is basically managed by the base station apparatus 10 under centralized control.

  As a supplement, the communication control circuit 110 uses absolute time / timing synchronization using GPS or the like for timing synchronization between its own device (base station device 10) and the terminal device. May be. In addition to absolute time synchronization, if a rough distance between the base station apparatus 10 and the terminal apparatus is known, a propagation delay corresponding to the distance is set in the terminal apparatus in advance. The terminal device may start transmission of the uplink signal at a time obtained by subtracting the propagation delay as a predetermined offset from the reception time of the signal serving as a timing reference of the base station device 10.

  Specifically, if an example of access control using time division multiple access (Time Division Multiple Access (TDMA)) is used, the terminal device is based on the frame timing obtained by timing detection such as a preamble at the beginning of the TDMA frame, The contents of slot assignment in the frame are grasped and communication operation is performed. Normally, a signal is transmitted at the timing of the uplink time slot. However, in the so-called time alignment control, the terminal is ahead of the timing that the terminal recognizes by considering the propagation delay. The transmission of the signal is started at the timing of the time, and as a result, the time at which the signal arrives at the base station apparatus 10 is adjusted so as to match the timing recognized by the base station apparatus 10.

  The amount of adjustment required at this time is that the actual signal is reciprocated from the base station device 10 to the terminal device and then to the base station device 10, so the terminal device transmits it ahead of time by twice the propagation delay. Will start. Note that this timing adjustment does not necessarily have to be performed by the terminal device. If the base station device 10 can grasp the distance between the own device and the terminal device or the propagation delay corresponding to the distance, the base station device 10 It is also possible to adjust the timing by adjusting the time at which the signal is received backward by that amount (twice the propagation delay). Alternatively, the base station apparatus may directly instruct the terminal apparatus that the time advanced by that time is the transmission timing.

  In this way, the base station apparatus 10 can start reception processing at a timing grasped by any means such as absolute time synchronization or time alignment control using GPS, and can perform processing with a known symbol timing. It is. The communication control circuit 110 controls and manages all of these timing control, access control, switching of the TDD switches 102-1 to 102-K, provision of terminal device information that is a transmission source when reading the reception weight, and the like. I do.

Next, the configuration of the average transmission / reception weight calculation unit 120 included in the base station apparatus 10 in the present embodiment will be described.
FIG. 3 is a schematic block diagram illustrating a configuration example of the averaged transmission / reception weight calculation unit 120 in the present embodiment. As shown in the figure, the averaged transmission / reception weight calculation unit 120 includes a channel information averaging circuit 121, a reception weight calculation circuit 122, a reception weight storage circuit 123, a calibration coefficient storage circuit 124, a calibration circuit 125, and a transmission weight calculation. A circuit 126 and a transmission weight storage circuit 127 are provided. The channel information, averaged transmission / reception weight vector, calibration coefficient, etc. in the following description are all different for each frequency component, and are calculated, processed, recorded, and managed for each frequency component individually. .

  The channel information averaging circuit 121 performs training signal averaging processing on signals input from the FFT circuits 108-1 to 108-K in accordance with instructions from the communication control circuit 110. The channel information averaging circuit 121 acquires, for each terminal device, uplink averaged channel information between the terminal device and each of the antenna elements 101-1 to 101-K for each frequency component. The averaging here is intended to extract channel information components that do not fluctuate over time, such as a line-of-sight wave or a stable reflected wave from a giant structure, assuming the use form shown in FIG. It is not always necessary to perform averaging for a long time, and the channel information acquired last may be used as it is. In this case, the averaging is not actually performed. However, for the convenience of explanation, it is assumed that the measurement value of one time is averaged, and the explanation is given by using the word “average”. I do. Details of this averaging will be described later.

The channel information averaging circuit 121 uses the channel information for each of the antenna elements 101-1 to 101-K for a plurality of times acquired at discrete times for each terminal device, and An average value of channel information is calculated, and the calculated average value is output as channel information.
Based on the channel information output from the channel information averaging circuit 121, the reception weight calculation circuit 122 calculates an average reception weight corresponding to each combination of antenna element and frequency component for each terminal device, and calculates the average reception The weight is output to the reception weight storage circuit 123. The reception weight storage circuit 123 stores the averaged reception weight output from the reception weight calculation circuit 122 and the combination of the terminal device, the antenna element, and the frequency in association with each other.

  The calibration coefficient storage circuit 124 stores in advance the calibration coefficient of each frequency component corresponding to each of the antenna elements 101-1 to 101 -K. This calibration coefficient is a coefficient used when calculating downlink channel information from uplink channel information. The calibration circuit 125 acquires downlink channel information by multiplying the channel information output from the channel information averaging circuit 121 by the calibration coefficient stored in the calibration coefficient storage circuit 124.

  Based on the downlink channel information acquired by the calibration circuit 125, the transmission weight calculation circuit 126 averages transmission weights corresponding to each combination of the antenna elements 101-1 to 101-K and frequency components for each terminal device. And the calculated average transmission weight is output to the transmission weight storage circuit 127. The transmission weight storage circuit 127 stores the averaged transmission weight output from the transmission weight calculation circuit 126 in association with the combination of the terminal device, the antenna element, and the frequency. Note that the transmission weight storage circuit 127 is also a part of the configuration related to the uplink included in the base station apparatus 10.

  A series of processes related to channel information estimation by each circuit in the averaged transmission / reception weight calculation unit 120, and subsequent calculation and storage of averaged transmission / reception weights are all performed for each frequency component.

Next, details of the first received signal processing circuits 191-1 to 191-L and the second received signal processing circuit 192 will be described.
As shown in FIG. 2, the receiving unit 100 includes first reception signal processing circuits 191-1 to 191-L of L plane, and here, one of them (for convenience, jth (1 ≦ j ≦ L) plane) will be described. FIG. 4 is a schematic block diagram illustrating a configuration example of the first reception signal processing circuit 191-j in the present embodiment. The first reception signal processing circuit 191-j includes multipliers 201-1 to 201 -K, an adder 202, and an average reception weight vector component distributor 203.

  The averaged reception weight vector component distributor 203 is connected to the averaged transmission / reception weight calculation unit 120 shown in FIG. The averaged reception weight vector component distributor 203 divides the average reception weight vector of each frequency component in the K-dimensional vector format input from the average transmission / reception weight calculation unit 120 into K components, and each component is divided into K components. The corresponding multipliers 201-1 to 201-K are input. The multipliers 201-1 to 201-K are connected to the corresponding FFT circuits 108-1 to 108-K, and receive signals # 1 to ## for the respective frequency components from the FFT circuits 108-1 to 108-K. Enter K. Multipliers 201-1 to 201-K multiply the components of the average reception weight vector and the reception signal for each frequency component, and output the multiplication result to adder 202. The adder 202 adds and synthesizes the signals input from the multipliers 201-1 to 201-K for each frequency component in units of symbols, and outputs the result to the second received signal processing circuit 192 as an intermediate signal #j. . As shown in FIG. 2, the L-system signal series that are signals from the first reception signal processing circuits 191-j (1 ≦ j ≦ L) are input to the subsequent second reception signal processing circuit 192. . As described above, the above processing is similarly performed for all frequency components.

FIG. 5 is a schematic block diagram showing a configuration example of the second received signal processing circuit 192 in the present embodiment. As shown in the figure, the second received signal processing circuit 192 includes a real-time transmission / reception weight calculation unit 204, a matrix multiplication unit 205, and signal detection circuits 206-1 to 206-L.
The real-time transmission / reception weight calculation unit 204 is connected to the real-time transmission weight matrix storage unit 130 and the first reception signal processing circuits 191-1 to 191-L shown in FIG. The matrix multiplication unit 205 is connected to the first reception signal processing circuits 191-1 to 191-L. The signal detection circuits 206-1 to 206-L are connected to the MAC layer processing circuit 180 shown in FIG. The second received signal processing circuit 192 is also connected to the communication control circuit 110, and various timings and control information related to communication are input from the communication control circuit 110.

The real-time transmission / reception weight calculation unit 204 and the matrix multiplication unit 205 receive L system signal sequences (intermediate signal # 1 to intermediate signal #L) from the first reception signal processing circuits 191-1 to 191-L. When it is determined in the instruction from the communication control circuit 110 that the leading portion of each intermediate signal is a training signal for channel estimation, the real-time transmission / reception weight calculation unit 204 determines the frequency based on the training signal included in the intermediate signal. Channel estimation is performed for each component, and an L × L channel matrix is obtained for each frequency component. Real-time transmission and reception weight calculating section 204, obtained by calculating the real-time reception weight matrix W _R based on the channel matrix by equation (12) or formula (13), input the calculated real-time reception weight matrix W _R the matrix multiplication unit 205 To do. Real-time reception weight matrix W _R of each frequency component calculated are therefore available as a real-time transmission weight matrix W _T by symmetry, real-time transmission and reception weight calculating unit 204 of the real-time reception weight matrix W _R and spatial multiplexing to a terminal device The combination is output to and stored in the real-time transmission weight matrix storage unit 130.

The matrix multiplication unit 205 handles each frequency component of the signal following the training signal among the intermediate signals # 1 to #L input from the first reception signal processing circuits 191-1 to 191-L as an L-dimensional vector. . Matrix multiplication unit 205 multiplies the real-time reception weight matrix W _R that is input from the real-time transmission and reception weight calculating section 204, an L-dimensional vector for each frequency component. Thereby, the mutual interference between the intermediate signals # 1 to #L is suppressed. The matrix multiplication unit 205 inputs the intermediate signals # 1 to #L whose mutual interference is suppressed by multiplication to the signal detection circuits 206-1 to 206-L.
The signal detection circuits 206-1 to 206-L individually perform signal detection processing, and output the reproduced bit strings to the MAC layer processing circuit 180 as data outputs # 1 to #L. The specific signal processing here is to perform demodulation processing for each subcarrier when the OFDM (A) modulation method is used, and to perform signal processing on the frequency axis when SC-FDE is used. This is a demodulation process for a signal obtained by performing equalization processing and synthesizing the signal by IFFT processing.

(Reception processing of this embodiment)
FIG. 6 is a flowchart showing a reception process performed by the base station apparatus 10 in the present embodiment. The signal transmitted by the terminal device is transmitted as a signal in communication using normal multi-user MIMO without being aware of various signal processing performed by the base station device 10 in the present embodiment. Here, although details of a method for selecting a terminal device that performs spatial multiplexing simultaneously, that is, a scheduling method, are omitted, the MAC layer processing circuit 180 selects a terminal device that performs spatial multiplexing and transmits data using a known technique.

  When the reception process is started in the base station apparatus 10 (step S101), the communication control circuit 110 selects a combination of terminal apparatuses that perform spatial multiplexing and transmit data (step S102), and sets scheduling contents related to the uplink. Notification is made to the selected terminal device (step S103). For example, if the notification method here is a system such as WiMAX (registered trademark) that employs base station centralized control using TDMA frames, UL-MAP (uplink allocation map) at the head of the frame is used. The assigned subcarrier number, time slot (OFDM symbol position), and duration (number of OFDM symbols) are reported. Of course, the allocation may be notified to the terminal device by another method, and depending on the access control method, the scheduling process and the process of notifying the terminal device may be omitted.

  In accordance with the processing of step S103, the first reception signal processing circuits 191-1 to 191-L correspond to the terminal devices assigned to the own circuit among the averaged reception weight vectors corresponding to the transmission source terminal devices. The average received weight vector for each frequency component of the antenna elements 101-1 to 101-K is read from the received weight storage circuit 123 (step S106).

In parallel with this, the A / D converters 107-1 to 107-K from the low noise amplifiers 103-1 to 103-K are signals transmitted from the terminal device that has received an uplink assignment instruction, and each antenna Processing is performed on signals received via the elements 101-1 to 101-K (steps S104-1 to S104-K). The processing here is amplification, down-conversion, unnecessary wave removal, and conversion from an analog signal to a digital signal for the received signal.
Thereafter, the FFT circuits 108-1 to 108-K extract signals in symbol units from the digital signals output from the A / D converters 107-1 to 107-K, and remove the guard interval from the extracted signals. By performing the FFT process, various received signal processes such as converting a signal on the time axis into a signal on the frequency axis are performed (steps S105-1 to S105-K).

The first reception signal processing circuits 191-1 to 191-L are separated for each frequency component by the averaged reception weight vector read from the reception weight storage circuit 123 in step S106 and the FFT circuits 108-1 to 108-K. The received signal is multiplied (steps S107-1 to S107-K).
The first received signal processing circuits 191-1 to 191-L add and synthesize signals weighted by multiplication with the average received weight vector corresponding to the terminal device assigned to the own circuit (steps S108-1 to S108). -L). The processes in steps S107-1 to S107-K and steps S108-1 to S108-L correspond to individual operations that multiply the received signal vector by the average received weight vector as a whole.

  The first reception signal processing circuits 191-1 to 191-L output the signal series (intermediate signals # 1 to #L) thus signal-separated to the second reception signal processing circuit 192. In the second received signal processing circuit 192, the real-time transmission / reception weight calculating unit 204 extracts training signals included in the intermediate signals # 1 to #L output from the first received signal processing circuits 191-1 to 191-L. This training signal is a channel estimation signal given to the head portion of the radio packet of the signal transmitted from each terminal device. The real-time transmission / reception weight calculation unit 204 acquires uplink channel information (information corresponding to each component of the channel matrix of size L × L) based on the extracted training signal (step S112).

Real-time transmission and reception weight calculating unit 204, the acquired channel information uplink, formula (12) or formula (13) and real-time reception weight matrix W _R matrix to calculate the real-time reception weight matrix W _R, which is calculated using the The result is output to the multiplication unit 205. Also, real-time transmission and reception weight calculating unit 204, calculates the real time transmission weight matrix W _T from the real-time reception weight matrix W _R (substantially the matrix transpose), and the calculated real-time transmission weight matrix W _T realtime transmission weight matrix storage The data is output to and stored in the unit 130 (step S113).

Matrix multiplication unit 205, a real-time reception weight matrix _{W R} that is output from the real-time transmission and reception weight calculating section 204, an intermediate signal of L lines output from the first received signal processing circuit 191-1~191-L # 1~ # The L-dimensional received vector composed of L is multiplied (step S114). By this matrix operation, the interference signal leaking into each signal series as residual interference is suppressed, and a signal closer to the signal series transmitted from each terminal apparatus is obtained.
Signal detection circuit 206-1 through 206-L performs predetermined received signal processing on the signal sequence obtained by the multiplication of the real-time reception weight matrix W _R in matrix multiplication unit 205, the results obtained the data output Output as # 1 to #L (steps S115-1 to S115-L), and the series of processing ends (steps S116-1 to S116-L).

  Here, the predetermined reception signal processing in the signal detection circuits 206-1 to 206-L is processing after signal separation of the spatially multiplexed signals. Therefore, the signal processing is the same as that of normal SISO communication. The received signal processing includes demodulation processing for each subcarrier when the OFDM (A) modulation method is used, and when SC-FDE is used, the frequency axis for the received signal of each frequency component It includes a single carrier demodulation process for a signal obtained by performing the above signal equalization process and synthesizing the signal by IFFT process. Furthermore, a decoding process for error correction may be performed as necessary. Naturally, signal processing such as a MAC layer is also performed after the above processing, but it is omitted here because it is the same as the processing by a known technique.

  Regarding the symbol timing, if the reception level of the received signal at each of the antenna elements 101-1 to 101-K is at a sufficient level, timing detection may be performed based on the received signal. If the level is very weak, it may be difficult to detect timing from the received signal. In this case, for example, in addition to absolute time synchronization using GPS, a subsequent frame using a periodic frame configuration with reference to the timing obtained from the immediately preceding frame timing detection signal, etc. The reception timing and symbol timing of the received signal may be determined using any synchronization means such as estimating the reception timing of the received signal. At this time, when determining the transmission timing, the terminal apparatus may transmit a signal at a predetermined timing in accordance with an instruction from the base station apparatus 10 based on the synchronized reception timing.

  Further, the signal of each frequency component of each antenna element obtained by the processing of steps S105-1 to S105-K performed by the FFT circuits 108-1 to 108-K is also output to the averaged transmission / reception weight calculation unit 120. . When this signal is a training signal for channel estimation arranged at the head of the radio packet, the average transmission / reception weight calculation unit 120 (strictly, the channel information averaging circuit 121) uses this information to Uplink channel information between the terminal apparatus and each antenna of the base station apparatus is acquired (step S109). Here, in general, not only channel information acquisition but also channel information extraction processing using stable components centered on line-of-sight waves is performed through averaging processing with past channel information and the like.

  Subsequently, the averaged transmission / reception weight calculation unit 120 calculates and updates the averaged reception weight vector and the averaged transmission weight vector based on the extracted channel information (step S110), and ends a series of processes (step S110). S111). The calculation and update of the average reception weight vector and the average transmission weight vector are specifically performed as follows. In the average transmission / reception weight calculation unit 120, the reception weight calculation circuit 122 calculates an average reception weight vector based on the acquired channel information, and stores the calculated average reception weight vector in the reception weight storage circuit 123. Further, the transmission weight calculation circuit 126 calculates an average transmission weight vector based on the acquired channel information, and stores the calculated average transmission weight vector in the transmission weight storage circuit 127.

  In principle, the average reception weight vector to be read in step S106 can be given by the average reception weight vector calculated in step S110. In this case, the processing of steps S105-1 to S105-K is performed on the channel estimation training signal attached to the head of the wireless packet, and steps S109 and S105 are performed on the signal obtained by the processing. The process of S110 is performed. In steps S107-1 to S107-K, the average reception weight vector calculated in step S110 may be used. In this case, however, the processes in steps S107-1 to S107-K are made to wait while the processes in steps S109 and S110 are executed, and steps S107-1 to S107 are traced back after the processes in steps S109 and S110 are completed. -K processing will be performed. However, the amount of time variation of the channel here is slight, and the signal separation processing between the signal sequences is calculated using the latest real-time channel matrix, so that there is almost no difference in characteristics. Therefore, from the viewpoint of signal processing delay time, it is preferable to use a value calculated based on channel information acquired in advance as the averaged reception weight vector.

(Configuration of transmission unit of this embodiment)
FIG. 7 is a schematic block diagram illustrating a configuration example of the transmission unit 140 included in the base station device 10 according to the present embodiment. As shown in the figure, the transmission unit 140 includes a first transmission signal processing circuit 193-1 to 193-L, a second transmission signal processing circuit 194, an addition / synthesis circuit 142-1 to 142-K, and an IFFT & GI adding circuit 143- 1 to 143-K, D / A converters 144-1 to 144-K, a local oscillator 145, mixers 146-1 to 146-K, filters 147-1 to 147-K, and a high power amplifier (HPA) 148 -1 to 148-K. The second transmission signal processing circuit 194 and the TDD switches 102-1 to 102-K are connected to the communication control circuit 110 shown in FIG. The first transmission signal processing circuits 193-1 to 193-L are connected to the averaged transmission / reception weight calculation unit 120 shown in FIG. The second transmission signal processing circuit 194 is connected to the real-time transmission weight matrix storage unit 130 shown in FIG. The antenna elements 101-1 to 101-K and the TDD switches 102-1 to 102-K are used in common with the configuration related to the uplink (reception unit 100). Actually, in the base station apparatus 10, the configuration related to the uplink and the configuration related to the downlink operate integrally, but for the convenience of description, they are described separately. Further, the processes in the second transmission signal processing circuit 194 and the first transmission signal processing circuits 193-1 to 193 -L shown below are all individually processed for each frequency component.

  When an L-system signal sequence (data input # 1 to #L) that simultaneously performs spatial multiplexing is input from the MAC layer processing circuit 180, the second transmission signal processing circuit 194 first performs a predetermined modulation process on the bit string. To implement. Specifically, when the OFDM (A) modulation method is used, the second transmission signal processing circuit 194 needs data inputs # 1 to #L to be transmitted input from the MAC layer processing circuit 180. Accordingly, after error correction coding, the data is distributed to each subcarrier for each terminal device, and the data distributed to each subcarrier is converted into phase / amplitude information in a predetermined modulation method for each symbol. In addition, when SC-FDE is used, in the second transmission signal processing circuit 194, data inputs # 1 to #L to be transmitted input from the MAC layer processing circuit 180 are error-correction encoded as necessary. After that, for each terminal apparatus, a series of bit strings is converted from single-carrier transmission unit bits to phase / amplitude information in a predetermined modulation method and single carrier over one symbol (SC-FDE block transmission unit). A signal is generated and replaced with a frequency component signal by FFT.

  Further, in the second transmission signal processing circuit 194, the L system signal series of the real time transmission weight matrix stored in the real time transmission weight matrix storage unit 130 is transmitted as the L system signal series for each frequency component. The real-time transmission weight matrix of each frequency component corresponding to the combination of destination terminal devices is multiplied. Each terminal after multiplying the L-system signal sequence by the real-time transmission weight matrix and the average transmission weight vector for in-phase synthesis performed by the subsequent first transmission signal processing circuits 193-1 to 193-L Interference signals between devices are suppressed. A signal obtained by this multiplication is output to each first transmission signal processing circuit 193-1 to 193-L.

  The first transmission signal processing circuits 193-1 to 193 -L average the transmission weights of the frequency components corresponding to the combinations of the destination terminal device assigned to the circuit and the antenna elements 101-1 to 101 -K. The vector is read from the averaged transmission / reception weight calculation unit 120. The first transmission signal processing circuits 193-1 to 193 -L transmit the signals for each subcarrier subjected to the modulation processing in the second transmission signal processing circuit 194 to K systems for each of the antenna elements 101-1 to 101 -K. The signal is distributed to the signal, and the averaged transmission weight vector read for the distributed signal is multiplied for each subcarrier. The first transmission signal processing circuits 193-1 to 193 -L add the signals of the respective frequency components for the antenna elements 101-1 to 101 -K and connected to the corresponding antenna elements 101-1 to 101 -K. The data is output to the synthesis circuits 142-1 to 142-K.

Addition synthesis circuits 142-1 to 142-K add and synthesize the signals generated by first transmission signal processing circuits 193-1 to 193-L for each frequency component, and output them to IFFT & GI adding circuits 143-1 to 143-K. To do.
IFFT & GI adding circuits 143-1 to 143-K perform IFFT processing on the signals added and synthesized by the adder / synthesizers 142-1 to 142-K, and convert the signals from the frequency axis to the signals on the time axis. Further, the IFFT & GI adding circuits 143-1 to 143-K add a guard interval to the signal on the time axis obtained by the conversion, perform waveform shaping as necessary, and transmit a digital baseband signal to be transmitted. And output to the D / A converters 144-1 to 144-K. The digital baseband signal corresponds to each of the antenna elements 101-1 to 101 -K and is individually signal processed.

The D / A converters 144-1 to 144-K convert the signals input from the IFFT & GI adding circuits 143-1 to 143-K into analog signals and output the analog signals to the mixers 146-1 to 146-K.
The local oscillator 145 outputs a local oscillation signal used for up-conversion and having a predetermined frequency to the mixers 146-1 to 146-K.
The mixers 146-1 to 146-K multiply the analog signals input from the D / A converters 144-1 to 144-K by the local oscillation signals input from the local oscillator 145 and up-convert them to radio frequencies. The signal is output to the filters 147-1 to 147-K. The local oscillation signals input to the mixers 146-1 to 146-K are the same signal, and local oscillation signals having the same frequency and phase are input to the mixers 146-1 to 146-K.

Filters 147-1 to 147-K remove signals outside the frequency band of the channel to be transmitted that are included in the signals input from mixers 146-1 to 146-K, and perform high power amplifiers 148-1 to 148-K. Output to.
The high power amplifiers 148-1 to 148-K amplify the signals input from the filters 147-1 to 147-K, and the antenna elements 101-1 to 101-K via the TDD switches 102-1 to 102-K. Send more.
The communication control circuit 110 further controls transmission timing, destination terminal device management, and switching of the TDD switches 102-1 to 102-K.

  In the above description, the case where the signal processing performed in the IFFT & GI adding circuits 143-1 to 143-K is processed in the subsequent stage of the adding / combining circuits 142-1 to 142-K has been described. However, the first transmission signal processing circuits 193-1 to 193 -L perform signal processing for converting the frequency component information performed in the IFFT & GI adding circuits 143-1 to 143 -K into time-axis components. In addition, the sampling data at each sampling time may be replaced with a process of adding and synthesizing all the destination terminal stations by the adding and synthesizing circuits 142-1 to 142-K. Even in this way, equivalent signal processing is possible, and either configuration may be selected. However, in this case, a circuit that performs IFFT is required in each of the first transmission signal processing circuits 193-1 to 193-L, and the circuit scale becomes larger than the configuration described above. Therefore, the configuration of FIG. 7 seems to be preferable from the viewpoint of overall circuit scale suppression. However, any of these may be used for realizing the base station apparatus 10.

Next, the structure of the 2nd transmission signal processing circuit 194 with which the base station apparatus 10 in this embodiment is provided is demonstrated.
FIG. 8 is a schematic block diagram illustrating a configuration example of the second transmission signal processing circuit 194 in the present embodiment. As shown in the figure, the second transmission signal processing circuit 194 includes modulation circuits 215-1 to 215-L and a matrix multiplication unit 214. The modulation circuits 215-1 to 215-L are connected to the MAC layer processing circuit 180 shown in FIG. The matrix multiplication unit 214 is connected to the first transmission signal processing circuits 193-1 to 193-L and the real-time transmission weight matrix storage unit 130.

  The modulation circuits 215-1 to 215-L, when L data inputs # 1 to #L, which are simultaneously spatially multiplexed, are input from the MAC layer processing circuit 180, the data inputs # 1 to #L are predetermined. Modulation processing is performed. Specifically, when the OFDM (A) modulation method is used, after data inputs # 1 to #L are subjected to error correction coding as necessary in the modulation circuits 215-1 to 215-L, The data distributed to each subcarrier is converted into a signal having phase / amplitude information by a predetermined modulation method for each symbol bit. When SC-FDE is used, in the modulation circuits 215-1 to 215-L, the data inputs # 1 to #L are subjected to error correction coding as necessary, and then transmitted for each bit of a transmission unit in a single carrier. Then, a single carrier signal that is converted into a signal having phase / amplitude information by a predetermined modulation method and covers one symbol (unit of block transmission of SC-FDE) is generated, and is replaced by a frequency component signal by FFT.

  In the modulation circuits 215-1 to 215-L, the L system signals of the respective frequency components subjected to predetermined modulation processing are input to the matrix multiplication unit 214. The matrix multiplication unit 214 handles L-system signals input from the modulation circuits 215-1 to 215-L as L-dimensional vectors. The matrix multiplication unit 214 reads the real-time transmission weight matrix corresponding to the combination to be spatially multiplexed from the real-time transmission weight matrix storage unit 130. The matrix multiplication unit 214 multiplies the read real-time transmission weight matrix by the L-dimensional vector, and outputs the multiplication result to the first transmission signal processing circuits 193-1 to 193-L as intermediate signals # 1 to #L.

Next, the configuration of the first transmission signal processing circuits 193-1 to 193 -L included in the base station apparatus in the present embodiment will be described. As illustrated in FIG. 7, the transmission unit 140 includes first transmission signal processing circuits 193-1 to 193-L on the L plane. In the following description, the description will be given focusing on one of the first transmission signal processing circuits 193-1 to 193-L on the L plane (for convenience, the jth plane (1 ≦ j ≦ L)).
FIG. 9 is a schematic block diagram showing the configuration of the first transmission signal processing circuit 193-j (1 ≦ j ≦ L) in the present embodiment. As shown in the figure, the first transmission signal processing circuit 193-j includes multipliers 211-1 to 211 -K, a signal duplicator 212, and an averaged transmission weight vector component distributor 213.

  The averaged transmission weight vector component distributor 213 is connected to the averaged transmission / reception weight calculation unit 120 shown in FIG. The averaged transmission weight vector component distributor 213 reads the K-dimensional averaged transmission weight vector of each frequency component from the transmission weight storage circuit 127 of the averaged transmission / reception weight calculation unit 120, and includes K included in the averaged transmission weight vector. The components are input to multipliers 211-1 to 211 -K corresponding to the respective components.

  The signal duplicator 212 is connected to the second transmission signal processing circuit 194. When the intermediate signal #j for each frequency component is input from the second transmission signal processing circuit 194, the signal duplicator 212 duplicates the digital signal identical to the intermediate signal #j into an intermediate signal for K systems, and duplicates it. The K system intermediate signals are input to the multipliers 211-1 to 211 -K.

  Each of the multipliers 211-1 to 211 -K is associated with the antenna elements 101-1 to 101 -K, and is connected to the corresponding adder / synthesizer circuit 142-1 to 142 -K. Multipliers 211-1 to 211 -K apply each component of the averaged transmission weight vector of each frequency component input from averaged transmission weight vector component distributor 213 to the signal input from signal duplicator 212. Multiply by symbol unit. The multipliers 211-1 to 211 -K output the multiplication results to the subsequent adder / synthesizers 142-1 to 142-K.

As described above, in the receiving system, the first received signal processing circuits 191-1 to 191-L shown in FIG. Is input to the second received signal processing circuit 192 shown in FIG. The second received signal processing circuit 192 performs residual interference suppression processing that reflects real-time channel information, and can achieve good reception characteristics in a state where the signals are clearly separated.
Similarly, in the transmission system, in the second transmission signal processing circuit 194 shown in FIG. 8, virtual L antenna elements whose orthogonality is enhanced by the first transmission signal processing circuits 193-1 to 193-L. On the other hand, a signal in which mutual residual interference is suppressed is generated by reflecting real-time channel information. Thereby, signal transmission can be performed with the relative SIR characteristics improved, and as a result, stable communication can be performed while performing spatial multiplexing.

(About transmission processing of this embodiment)
Next, transmission processing performed by the base station apparatus 10 in the present embodiment will be described with reference to the drawings.
FIG. 10 is a flowchart showing a transmission process performed by the base station apparatus 10 in the present embodiment. As described above, here, a case where the OFDM (A) modulation method or SC-FDE is used will be described.

When the base station apparatus 10 starts transmission processing (step S161), the communication control circuit 110 or the scheduling processing circuit 181 selects a terminal apparatus to be subjected to spatial multiplexing using a known technique (step S162). It should be noted that here, a detailed description of a method for selecting a terminal device that performs spatial multiplexing simultaneously, that is, a scheduling method is omitted.
Modulation circuits 215-1 to 215-L in second transmission signal processing circuit 194 generate transmission signals of each frequency component from data inputs # 1 to #L input from MAC layer processing circuit 180 (step S163). ).

  When the OFDM (A) modulation method is used, when the modulation circuits 215-1 to 215-L generate a transmission signal in step S163, for example, a bit string that configures a wireless packet subjected to MAC layer signal processing If necessary, encoding processing for error correction, addition of overhead information (preamble signal) composed of timing detection signals, channel estimation signals, etc., and a predetermined modulation scheme (for example, BPSK) by dividing bits for each subcarrier , QPSK, 16QAM, etc.) signal point mapping processing is performed. In addition, when SC-FDE is used, when the modulation circuits 215-1 to 215-L generate transmission signals in step S163, the MAC layer signal processing is performed as in the OFDM (A) modulation method. If necessary, encoding processing for error correction, addition of overhead information (preamble signal) including a timing detection signal and a channel estimation signal, a predetermined modulation scheme (for example, BPSK, In order to perform single carrier transmission signal processing such as signal point mapping processing in QPSK, 16QAM, etc., or transmission weight multiplication processing on the frequency axis, FFT processing in units of blocks is performed.

  On the other hand, in the processing on the reception side shown in FIG. 6, the average transmission / reception weight calculation unit 120 sequentially acquires downlink channel information after acquiring uplink channel information in step S109 (step S164). An average transmission weight vector is calculated and stored in the average transmission / reception weight calculation unit 120, and after the real-time transmission / reception weight calculation unit 204 acquires an uplink real-time reception weight matrix in step S113, this is used as a downlink real-time transmission weight matrix. The data is stored in the real-time transmission weight matrix storage unit 130 (step S165). The processes in steps S164 and S165 described above correspond to processes that are sequentially performed regardless of the data transmission process (steps S161 to S163).

Here, following the processing in step S163, the matrix multiplication unit 214 in the second transmission signal processing circuit 194 performs real-time transmission of L × L size of each frequency component corresponding to the combination of terminal devices selected by the communication control circuit 110. The weight matrix is read from the real-time transmission weight matrix storage unit 130 (step S166).
The matrix multiplying unit 214 multiplies the read L × L size real-time transmission weight matrix by the L-dimensional vector having the L system signal sequences generated in the modulation circuits 215-1 to 215-L as components ( Step S168). The multiplication result is output to the corresponding first transmission signal processing circuits 193-1 to 193-L.

In the first transmission signal processing circuits 193-1 to 193-L, the average transmission weight vector of the terminal device corresponding to the own circuit is read from the transmission weight storage circuit 127 in the average transmission / reception weight calculation unit 120 (step S167).
The first transmission signal processing circuits 193-1 to 193 -L respectively transmit L frequency transmission signals of each frequency component generated in step S 168 for each transmission signal transmitted by each antenna element 101-1 to 101 -K. And the average transmission weight vector of each frequency component read out in step S167. Each of the first transmission signal processing circuits 193-1 to 193 -L outputs the multiplication result to the addition / synthesis circuits 142-1 to 142 -K (steps S <b> 169-1 to S <b> 169 -K).

  Each of the adder / synthesizers 142-1 to 142-K adds and synthesizes the signals input from the first transmission signal processing circuits 193-1 to 193-L. The IFFT & GI adding circuits 143-1 to 143-K convert the signals obtained by the addition synthesis in the addition synthesis circuits 142-1 to 142-K from signals on the frequency axis to signals on the time axis and guard the signals. An interval is given, a series of processing such as waveform shaping is performed as necessary, and the result is output to the D / A converters 144-1 to 144-K (steps S170-1 to S170-K).

  The D / A converters 144-1 to 144-K convert the signals output from the IFFT & GI adding circuits 143-1 to 143-K into analog signals by digital / analog conversion. The mixers 146-1 to 146-K up-convert the signals converted into analog signals by the D / A converters 144-1 to 144-K to radio frequencies. Filters 147-1 to 147-K remove out-of-band signals included in the upconverted signal and output the signals to high power amplifiers 148-1 to 148-K. The high power amplifiers 148-1 to 148 -K amplify the signals output from the filters 147-1 to 147 -K and transmit the signals from the antenna elements 101-1 to 101 -K (steps S 171-1 to 171 -1). K). Thus, the transmission process ends (steps S172-1 to 172-K).

These series of processes (processes from step S163 and step S168 to steps S171-1 to S171-K) are performed in units of OFDM symbols or SC-FDE blocks when the wireless packet covers a plurality of symbols or a plurality of blocks. This processing is continuously performed for the number of symbols or the number of blocks, whereby transmission signal processing for the entire wireless packet is performed.
As a feature of the transmission processing of the base station apparatus 10 in the present embodiment, the real-time transmission weight matrix stored in the real-time transmission weight matrix storage unit 130 is read in step S166, and further stored in the transmission weight storage circuit 127 in step S167. The average transmission weight vector corresponding to the terminal device being read is read out, and the processing is divided into operations for two-stage directivity control. Averaging calculated and stored in advance for each terminal device The transmission weight vector and the real-time transmission weight matrix are used. Thus, each time transmission is performed, transmission processing can be performed without calculating a large-scale transmission weight matrix depending on the number of antenna elements.

In addition, the signals transmitted in this manner are received at the antenna elements of the respective terminal apparatuses, with the signals transmitted from the antenna elements 101-1 to 101-K of the base station apparatus 10 being approximately in phase for each frequency component. Will be. The signal received at each terminal device can be processed as a normal signal that can be received without being conscious of various signal processing performed by the base station device 10 in particular.
In addition, overhead information (preamble signal) such as channel estimation signals performed by the modulation circuits 215-1 to 215-L in step S163 has a pattern common to a plurality of terminal apparatuses unlike the uplink. A signal can be used. This can be received in a state where signals destined for other terminal devices are sufficiently suppressed in each terminal device by multiplication of the real-time transmission weight matrix and the averaged transmission weight vector performed in steps S168 and S169-1 to S169-K. This is because it is not necessary to assign a separate preamble signal to each terminal device. As a result, it is not necessary to assign a preamble signal having the number of symbols depending on the number of spatial multiplexing while performing spatial multiplexing, and it is possible to suppress a decrease in the efficiency of the MAC layer.

(About channel estimation processing and average transmission / reception weight vector calculation)
In the averaged transmission / reception weight calculation unit 120 shown in FIG. 3 and the real-time transmission / reception weight calculation unit 204 shown in FIG. 5, it is necessary to acquire channel information used when calculating reception weights and transmission weights. The channel information may be acquired by any method, but an example of the acquisition method is shown below.

  In general, the channel information basically has an asymmetric relationship between the uplink and the downlink, as shown in the description related to the previous calibration. For this reason, it is also possible for the terminal device to receive a signal transmitted by the base station device on the downlink, and to feed back channel information acquired by the terminal device to the base station device using the control line. In this case, the terminal device receives signals transmitted by the uplink using the K antennas of the base station device, and acquires downlink channel information through processing such as calibration using the channel information acquired by the base station device. Will be described.

First, calculation of the average transmission / reception weight vector will be described.
First, when spatial multiplexing is not performed, a training signal for normal channel estimation is transmitted by the terminal device in advance of the data area of the wireless packet, received by the base station device, and a series of received signal processing is performed. Later, it is decomposed into each frequency component by FFT processing, and channel information of each frequency component is obtained by comparing it with a transmission signal for each frequency component. For example, in general, in the OFDM modulation scheme, each frequency component of the training signal for channel estimation is modulated by BPSK or the like so that the peak-to-average power ratio (PAPR) can be reduced. Therefore, channel estimation is possible by performing this inverse process on the received signal.

  The above is a simple case where spatial multiplexing is not performed. However, when performing spatial multiplexing, a plurality of symbols are used in order to grasp channel information between antennas that perform spatial multiplexing. For example, consider a case where the terminal device # 1 and the terminal device # 2 transmit signals. In the simplest example, only the terminal device # 1 transmits the pattern P for the first symbol, and only the terminal device # 2 transmits the pattern P for the second symbol. In this case, the channel estimation of the terminal device # 1 may be performed at the first symbol, and the channel estimation of the terminal device # 2 may be performed at the second symbol. In consideration of performing channel estimation of all frequency components, only the terminal device # 1 transmits the first symbol on the even-numbered subcarrier, and only the terminal device # 2 transmits the second symbol on the even-numbered subcarrier. If only the device # 2 and only the terminal device # 1 transmits with odd subcarriers, the transmission power per frequency component can be doubled and the SNR of each subcarrier can be improved.

  In another example, in all subcarriers, terminal device # 1 transmits pattern “P” and terminal device # 2 also transmits pattern “P” for the first symbol, and terminal device # 1 transmits pattern “P” for the second symbol. The terminal device # 2 transmits the pattern “-P”. In this case, when the first symbol and the second symbol of the received signal are added, a received signal similar to that obtained when terminal device # 1 transmits a “2P” signal is obtained. Further, when the second symbol is subtracted from the first symbol of the received signal, a received signal similar to the case where terminal device # 2 transmits a “2P” signal is obtained. With these processes, when the signals transmitted by each terminal apparatus are received by the K antennas of the base station apparatus, it is possible to obtain what value the channel information between the respective antennas has. .

  As described above, in providing an uplink channel estimation training signal for acquiring a channel matrix, the training signal transmitted by the terminal device that simultaneously performs spatial multiplexing is not the same pattern including each frequency component. Attention is required. This is a general condition in the case of multi-user MIMO. Therefore, each terminal apparatus is instructed from the base station apparatus which pattern of the transmission signal to transmit.

As described above, even in the case where training signals are transmitted from a plurality of terminal devices at the frequency component of interest and the symbol of interest, channel estimation for each terminal is performed using the above-described procedure or existing channel estimation means. Although it is possible to implement, for the sake of simplicity in the following description, at least the frequency component of interest and the symbol of interest will be described as an example in which signals are transmitted from only one terminal device.
By performing the above reception signal processing on the channel estimation signal given to the head of the wireless packet, the reception signals separated into the frequency components by the FFT circuits 108-1 to 108-K are averaged transmission / reception. It is input to the weight calculation unit 120. As described above, since the training signal is subjected to predetermined modulation processing for PAPR suppression, channel information can be acquired by performing the reverse processing. By following the instruction from the communication control circuit 110, it is possible to grasp the terminal device that is the transmission source of the training signal, and thereby grasp the channel information of the corresponding antenna by the frequency component.

Next, when channel information acquired at a certain number of times is averaged at a predetermined time and number of times, if the channel information is simply used for averaging as it is, it becomes channel information different from the original value. Need attention. The following points should be noted in the averaging process. In general, the channel estimation phase information of the channel information obtained by channel estimation is not always subject to channel timing fluctuations due to errors in symbol timing detection or the initial phase uncertainty of the local oscillator on the transmission side. It is not a constant value. However, unlike the phase uncertainty due to the terminal device, since the uncertainty is affected in the same way in all antenna elements in the base station apparatus, the relative relationship between any two antenna elements Will be preserved. For example, if the phase information of the channel information of the antenna # 1 is used as a reference and the phase of the channel information of the other antenna elements is re-converted into a relative phase relationship with respect to the antenna # 1, each time there is no channel fluctuation, The same value will be estimated. In the following description, channel information obtained by correcting the reference phase offset will be referred to as “relative component of channel information”. For the sake of convenience, the estimated channel information regarding the j-th antenna of the k-th frequency component is represented as ^ h _j ^(k) , and the channel information corrected as its relative component is represented as ~ h _j ^(k) . Here, h with “^ (hat)” appended is denoted as “^ h”, and h with “˜ (tilde)” appended is denoted as “˜h”. Hereinafter, similarly, in a mathematical expression or the like, when a character such as “⌒” is written on a character, the symbol is written before the character.

FIG. 11 is a flowchart showing a relative component acquisition process for acquiring a relative component of uplink channel information in the present embodiment. This process shows a part of the process performed by the channel information averaging circuit 121.
When channel information corresponding to each of the first antenna element 101-1 to the Kth antenna element 101-K is acquired from the FFT circuits 108-1 to 108-K (Step S121-). 1 to S121-K), and the k-th frequency component of the signal received by the j-th antenna element 101-j (1 ≦ j ≦ K) is “^ h _j ^(k) ” (steps S122-1 to S122-). K).
The channel information averaging circuit 121 calculates the offset value e ^{−jφ (} ) from the channel information (^ h ₁ ^(k) ) in the first antenna element 101-1 and its complex conjugate (^ h ₁ ^(k) ) ^{*. k)} (= (^ h ₁ ^(k) ) ^* / ‖ ^ h ₁ ^(k) ‖) is calculated (step S123). Here, “‖x‖” represents the absolute value of x. This offset value is obtained individually for each frequency component.

The channel information averaging circuit 121 uses the calculated offset value e ^{−jφ (k)} for the k-th frequency component as the k-th frequency component ^ h ₁ ^(k) corresponding to the antenna elements 101-1 to 101 -K,. ^ by multiplying the _h ^{K (k),} the relative complex phase relationships channel information _{to h} ¹ indicating (k), ..., and calculates the _~h ^{K (k) (step} S124-1~S124-K) The process is terminated (steps S125-1 to S125-K).
As described above, the channel information averaging circuit 121 uses the channel information of the first antenna element 101-1 as a reference, and the relative channel information of the antenna elements 101-1 to 101-K to h ₁ ^(k). ,... ˜h _K ^(k) are calculated. The channel information averaging circuit 121 performs the processing from step S121-1 to step S125-K for all frequency components for each terminal device, and short-term average channel information for all frequency components for each terminal device. relative component _~h ¹ (k), ..., and calculates the _~h ^{K (k).}

FIG. 12 is a flowchart showing another relative component acquisition process for acquiring the relative component of the uplink channel information in the present embodiment. The difference between the process shown in FIG. 11 and the process shown in FIG. 11 is based on the complex phase offset value φ ^(k) used when acquiring the relative component with reference to the complex phase of the specific antenna element 101-1. Instead, the average value of the complex phases (that is, the angles represented by 0 to 2π) of all the antenna elements 101-1 to 101-K is used in step S126.
In step S126, the following equation (20) is used based on the k-th frequency components ^ h ₁ ^(k) ,..., ^ H _K ^(k) in the channel information corresponding to the antenna elements 101-1 to 101-K. Thus, the average value φ ^(k) of the complex phases of all antennas for the k-th frequency component is obtained and used in steps S124-1 to S124-K, thereby obtaining the relative component.

This offset value is obtained individually for each frequency component. Even when the complex phase component of each of the antenna elements 101-1 to 101-K includes an error, the equation (20) averages the error. As a result, a highly accurate relative component is obtained. Can do.
Although performs processing for extracting the complex phase of the formula (20) channel information ^ h i ^_(k), the angle information of the channel information ^ h i real and complex phase from the ratio of the imaginary part of ^_(k) Can be obtained and a value equivalent to the equation (20) can be calculated based on the angle information. Although this appears to be mathematically different, it is mathematically equivalent, and of course it is possible to substitute processing with such mathematically equivalent alternatives for all arithmetic operations. It is.
When performing the channel information averaging process, the relative component of the channel information is extracted by the above process, and then the relative component averaging process is performed.

FIG. 13 is a flowchart showing an averaging process of uplink channel information in the present embodiment. The channel information averaging circuit 121 performs the above-described processing of FIG. 11 or 12 a plurality of times at continuous or discrete times, and is averaged by averaging processing based on the relative components of the obtained channel information. Calculate channel information.
When the channel information averaging circuit 121 completes the first to Q-th channel information relative component acquisition processing (steps S131-1 to S131-Q), the channel information relative component to h ₁ ^{(k) [q]} , ... ˜h _K ^{(k) [q]} (q = 1,..., Q) are collected (steps S132-1 to S132-Q). Here, the relative component of channel information to h ₁ ^{(k) [q]} is a relative component of the channel information with respect to the k-th frequency component of the first antenna element 101-1 calculated for the q-th time. Therefore, steps S132-1 to S132-Q correspond to processing performed at different timings. Note that the number Q of times subject to averaging processing is determined in advance based on the environment in which the wireless communication system is operated. This may be a fixed number, or the number of times collected within a predetermined time may be set as Q, and averaging may be performed at different times each time averaging is performed.

Further, the channel information averaging circuit 121 calculates the average channel information h _i ^(k) (i = 1,..., K) using the following equation (21) (step S133). Since steps S132-1 to S132-Q are completed at different timings, the relative component of this channel information is temporarily stored in the memory until step S133, which is an averaging process, is performed. In addition, step S133 may be performed at a time. Alternatively, the individual summation processing by Σ in step S133 is performed every time the individual processing in steps S132-1 to S132-Q is completed, and is stored in the memory until the next processing. You may read them each time and may implement step S133.

When the channel information averaging circuit 121 calculates the average channel information h _i ^{(k) obtained} by averaging the channel information of each frequency component for each of the antenna elements 101-1 to 101 -K, the averaging process ends. (Step S134).
The calculation of the average received weight vector, which will be described later, is performed using the uplink channel information acquired here, but when performing these processes, it may be temporarily stored in the memory. I do not care.

Through the above processing, uplink channel information can be acquired directly. In this embodiment, since the relative component acquisition process (FIGS. 11 and 12) is performed, the long-time average is not affected by the phase shift in each short-time average process from the first time to the Q-th time. Channel information can be calculated. Note that the superscript k on the right shoulder of the channel information h _i ^(k) described above represents a number for identifying a frequency component.
In FIG. 13, as an example of the channel information averaging process, a case where channel information acquired over a plurality of times is simply averaged is shown as an example, but a forgetting factor μ (0 <μ <1) is set to Multiplying the channel information acquired by the ratio μ, and further multiplying the averaged channel information so far by the ratio (1-μ), combining them, and averaging, etc. You may implement | achieve by a digitization process.

FIG. 14 is a flowchart showing processing for acquiring downlink channel information in the present embodiment. Since it is difficult for the base station apparatus 10 to obtain channel information directly as in the uplink for the downlink from the base station apparatus 10 to the terminal apparatus, the downlink channel is based on the uplink channel information. Estimate information.
In the base station apparatus 10, the calibration circuit 125 receives the uplink channel information h _i ^(k) from the channel information averaging circuit 121 (step S 142), and the calibration circuit 125 performs the _{i th operation on} the input channel information h _i ^(k) . The calibration coefficient C _i ^(k) corresponding to the k-th frequency component in the antenna element 101-i is read from the calibration coefficient storage circuit 124 (step S143).

The calibration circuit 125 multiplies the input channel information h _i ^(k) by the read calibration coefficient C _i ^(k) (step S144), and uses the multiplication result as downlink channel information to transmit a weight calculation circuit. The information is output to 126, and the process is terminated (step S145).
The calculation of the transmission weight, which will be described later, is performed using the downlink channel information acquired here, but it may be temporarily stored in the memory when performing these processes. The calibration circuit 125 performs the processing from step S142 to step S144 described above for each frequency component for each of the antenna elements 101-1 to 101 -K.

  The calculation process of the average reception weight vector for the channel information in the uplink and the calculation process of the average transmission weight vector for the channel information in the downlink are basically the same. Therefore, here, the process of calculating the average reception weight vector in the uplink will be described, and a specific description of the process of calculating the average transmission weight vector in the downlink will be omitted. The following description specifically shows calculation of vector components of the average received weight vector, and the vector is a combination of these components.

FIG. 15 is a flowchart showing a process for calculating an average reception weight vector in the base station apparatus 10 of the present embodiment.
When the process is started (step S451), the channel information h _i ^{(k) in the} uplink of the k-th frequency component related to a certain terminal device of interest in the i-th antenna element 101-i is stored in the reception weight calculation circuit 122 as channel information. Input from the averaging circuit 121 (step S452).
The reception weight calculation circuit 122 calculates the complex conjugate (h _i ^(k) ) ^* of the channel information h _i ^(k) input from the channel information averaging circuit 121 and calculates the calculated complex conjugate (h _i ^(k) ). ^A value obtained by dividing ^* by the absolute value of the channel information h _i ^{(k) is used} as the component w _i ^(k) of the average reception weight vector (step S453). That is, the reception weight calculation circuit 122 calculates the component w _i ^(k) of the average reception weight vector using the following equation (22) (step S453).

The reception weight calculation circuit 122 stores each component w _i ^(k) of the calculated average reception weight vector in the reception weight storage circuit 123 (step S454), and ends the process (step S455).
The reception weight calculation circuit 122 performs the above-described processing from step S452 to step S454 for all the terminal devices for each frequency component for each of the antenna elements 101-1 to 101 -K.
The transmission weight calculating circuit 126, the same operation as the reception weight calculating circuit 122 calculates the average transmission weight vector from the channel information is input from the calibration circuit 125 h _{i ^(k),} calculated averaged transmission The weight vector is stored in the transmission weight storage circuit 127.

  In general, as a weight for signal synthesis when signals are received by a plurality of antennas, there may be a large difference in the signal reception level for each antenna due to the influence of fading or the like. In this case, the reception level is low. In order to suppress the influence of noise of the received signal of the antenna element, the maximum ratio combining weight shown below is often used. Therefore, in the present embodiment, the following equation (23) can be used instead of the equation (22).

  The difference between the two weights of Equation (22) and Equation (23) is the difference in the magnitude (absolute value) of the coefficient of the i-th antenna element for each antenna element or the same. 23) incorporates an effect of reducing the weight of a signal having a relatively high noise level (that is, a low reception level). However, both are common in that the complex phase is adjusted to be zero or constant after multiplication with the averaged channel information. In a broad sense, equation (23) can also be said to be a kind of weight for in-phase synthesis. In the present embodiment, the same effect can be obtained even if other weights are used as long as the complex phase is zero or a constant value after multiplication with the averaged channel information.

  In general, it is preferable to use the weight of Expression (22) as the average transmission weight vector and the weight of Expression (23) as the average reception weight vector. In this embodiment, it is recommended to install the base station device and the terminal device so that a line of sight can be secured. Unlike a multipath environment in which a large number of multiple reflected waves exist, a line-of-sight wave is generated. Since this is a dominant environment, the difference in reception level for each antenna element is relatively difficult. As a result, the weight obtained by equation (23) is effectively a weight equivalent to equation (22).

  Note that the average transmission weight vector and the average reception weight vector have directions (relative relations between the components) indicated by vectors (weight vectors) each having a weight value for each antenna element as a component of each element. Has an effective meaning. For example, if two vectors are orthogonal (that is, the inner product is zero), even if all the components of one vector are multiplied by a constant c, the inner product remains zero and the orthogonal relationship does not change. For this reason, since a vector obtained by multiplying a certain weight vector by a predetermined coefficient can be considered to be the same in the direction, the weight vector multiplied by a constant coefficient for each antenna element does not depend on the coefficient to be multiplied. Is equivalent. That is, the weights obtained by multiplying all the components of the vectors given by Expression (22) and Expression (23) by the common coefficient are all rewritten into weight vectors having these weights as the components and interpreted as weights in the embodiment. Is equivalent to

(Calculation of real-time transmission / reception weight matrix)
In the above-described calculation of the average transmission weight vector and the average reception weight vector, the weight that is the same phase composition is calculated for the channel information between the terminal device and each antenna element. If the number of antennas is K, the average transmission weight vector and the average reception weight vector to be obtained are K-dimensional vectors. On the other hand, the real-time transmission weight matrix and the real-time reception weight matrix use channel estimation results after passing through the first reception signal processing circuits 191-1 to 191-L. This specific process will be described below.

  In order to simplify the description, in the following description, a case where two terminal apparatuses are spatially multiplexed on the uplink (that is, L = 2) will be described. Further, as described in the above description, at least the frequency component of interest and the symbol of interest will be described by taking as an example a case where a signal is transmitted from only one terminal device. For example, when focusing on a certain frequency component, a training signal from the first terminal device is transmitted in the first symbol, and a training signal from the second terminal device is transmitted in the second symbol. . At this time, the first reception signal processing circuits 191-1 to 191-2 respectively perform multiplication of the average reception weight vector of the first terminal device and multiplication of the average reception weight vector of the second terminal device, respectively. As a signal received by the virtual two antennas obtained by adding and synthesizing signals, signals of two signal series are input to the second received signal processing circuit 192. These training signals are obtained by performing some modulation processing for each frequency component for PAPR reduction on the transmission side. Therefore, the real-time transmission / reception weight calculation unit 204 in the second received signal processing circuit 192 first obtains a state indicating channel information directly by performing inverse processing of modulation for each frequency component on the received signal.

The signal input from the first received signal processing circuit 191-1 and subjected to this conversion is the virtual channel information “h _v11 regarding the first symbol signal between the first terminal device and the first virtual antenna. The second symbol signal indicates virtual channel information “h _v12 ” between the second terminal apparatus and the first virtual antenna.
Similarly, the signal input from the first received signal processing circuit 191-2 and subjected to this conversion is the virtual channel information relating to the first symbol signal between the first terminal apparatus and the second virtual antenna. the "h _v21", the second symbol of the signal indicates "h _v22" virtual channel information about between the second terminal device and the second virtual antenna. If a virtual channel matrix having “h _vij ” as an (i, j) component is expressed as “H _v ”, a real-time transmission / reception weight matrix is calculated using equations (12) to (15). Is possible.

In the above description regarding “channel estimation processing and calculation of average transmission / reception weight vector”, as a training signal, terminal device # 1 has pattern “P” for the first symbol, and terminal device # 2 has pattern “P”. The second symbol shows an example in which the terminal device # 1 transmits the pattern “P” and the terminal device # 2 transmits the pattern “-P”. Even if the training signal for channel estimation to be used is replaced with another pattern like this, the method of obtaining each component of the virtual channel matrix “H _v ” is simply changed, and the other processes are exactly the same. Can be done. The same applies when other training signals are used.

(About another calculation method of real-time transmission weight matrix)
In the above description, the case has been described where transmission is performed by a combination of terminal devices capable of acquiring a real-time reception weight matrix. However, in this case, the combination of terminal devices that can perform spatial multiplexing at the time of transmission is limited to the combination of terminal devices that have acquired a real-time reception weight matrix relatively recently, so the degree of freedom of scheduling Is restrained to some extent.
Therefore, hereinafter, another method for calculating the real-time transmission weight will be briefly described. First, for the sake of simplicity, consider a case where two terminal apparatuses simultaneously perform spatial multiplexing transmission on a certain frequency component. First, channel information vectors of the k-th frequency component configured by the latest channel information for the terminal device # 1 and the terminal device # 2 are set to h ₁ ^(k) and h ₂ ^(k) . Similarly, the average transmission weight vectors of the k-th frequency component for the terminal device # 1 and the terminal device # 2 are w ₁ ^(k) and w ₂ ^(k) . Terminal devices # 1 and # 2 after the first transmission signal processing circuits 193-1 to 193-L (here, the case of L = 2 is illustrated) when viewed from the second transmission signal processing circuit 194 The effective 2 × 2 channel matrix H _eff can be expressed as follows.

Here, the real time transmission weight matrix _{W T} is the form of the following equation (25), calculates a condition that non-diagonal elements of the matrix product _H eff · _{W T} of the above-mentioned _{H eff} becomes zero.

Here, the vector “⌒h _j ^(k) ” is defined by the following equation (27).

  If this is used, since the off-diagonal term component is zero in equation (26), the following equation (28) and equation (29) can be obtained.

Here, if the vector “⌒h _j ^(k) ” is obtained in advance, the calculation of α and β to be calculated in real time at the time of transmission requires only K multiplications. That is, if a total of 2 × K multiplication operations are allowed, the combination can be expanded to any combination of terminal devices. Hereinafter, a configuration in which the above-described change related to the real-time transmission weight matrix is reflected in the circuit configuration will be described as a modification of the present embodiment.

(Variation 1: Another configuration related to real-time transmission weight matrix calculation)
FIG. 16 is a schematic block diagram illustrating a configuration of the base station apparatus 10 according to the present embodiment as the first modification. The difference from the base station apparatus 10 shown in FIG. 1 is that the real-time transmission weight matrix storage unit 130 is replaced with a real-time transmission weight matrix calculation unit 131. Unlike the real-time transmission weight matrix storage unit 130, the real-time transmission weight matrix calculation unit 131 is connected to the averaged transmission / reception weight calculation unit 120, but is not connected to the reception unit 100.

The real-time transmission weight matrix calculation unit 131 obtains the latest downlink channel information vector h _j ^(k) and updates the average transmission weight vector w _j ^{(k) in} the average transmission / reception weight calculation unit 120. The latest downlink channel information vector h _j ^(k) and the average transmission weight vector w _j ^(k) are input. In addition to the configuration described in the above embodiment, the average transmission / reception weight calculation unit 120 according to the first modification outputs a configuration to the real-time transmission weight matrix calculation unit 131 when the channel information and the average transmission weight vector are updated. Have Except for this output function, there is no explicit change to the configuration of the averaged transmission / reception weight calculation unit 120 shown in FIG. However, in this case, the channel information averaging circuit 121 notifies the calibration circuit 125 of the latest channel information vector as well as the averaged channel information vector, and calibration processing is performed on both of them. become. It should be noted that when averaging is not performed, both of them are the same, so this point is not changed.

The real-time transmission weight matrix calculation unit 131 performs the calculation of Expression (27) every time the channel information vector and the average transmission weight vector are input, and stores the result in the memory together with the average transmission weight vector w _j ^(k). Record it. When the communication control circuit 110 gives an instruction to start transmission processing and a notification of a combination of terminal stations that perform spatial multiplexing, “⌒h _j ^(k) given by Expression (27) related to the corresponding terminal device. ”And the averaged transmission weight vector w _i ^(k) , α and β are calculated by Equation (28) and Equation (29), and are input to the second transmission signal processing circuit 194 of the transmission unit. With the above changes, it is possible to deal with spatial multiplexing of any combination of terminal devices without changing the others.

  When the spatial multiplexing number is 3 or more, Equation (25) is a matrix with a diagonal component of 1 and an off-diagonal component of an unconstant, and the conditions for each unconstant are set by the same processing as in Equation (26). If derived, the same extension is possible. However, in this case, since the amount of calculation increases significantly, the impact on the circuit scale increases, and the advantages of the base station apparatus 10 in this modification gradually diminish. However, the calculation amount can be sufficiently suppressed as compared with the case where the equations (10-1) and (10-2) are used.

As described above, the modification example in the present embodiment regarding the calculation of the real-time transmission weight matrix has been described. The explanation is added below.
(Variation 2: Another configuration of the average transmission / reception weight calculation unit)
In the above-described embodiment, the configuration of the averaged transmission / reception weight calculation unit 120 illustrated in FIG. 3 can be realized as another configuration that is substantially equivalent. A configuration example as a modification of the averaged transmission / reception weight calculation unit 120 in the above embodiment will be described.
FIG. 17 is a schematic block diagram showing the configuration of the averaged transmission / reception weight calculation unit 120a in the modification of the above embodiment. The averaged transmission / reception weight calculation unit 120a includes a channel information averaging circuit 121, a reception weight calculation circuit 122, a reception weight storage circuit 123, a calibration coefficient storage circuit 124, a transmission weight calculation circuit 126a, and a transmission weight storage circuit 127. doing. The difference between the averaged transmission / reception weight calculation unit 120a and the averaged transmission / reception weight calculation unit 120 (FIG. 3) is that the calibration circuit 125 is not included (more precisely, the transmission weight calculation circuit 126a is similar to this). And the transmission weight calculation circuit 126a is provided instead of the transmission weight calculation circuit 126. Also, the function of the transmission weight calculation circuit 126a is to perform averaging by dividing each component of the averaged reception weight calculated by the reception weight calculation circuit 122 by the calibration coefficient stored in the calibration coefficient storage circuit 124. The processing is changed to the calculation of the transmission weight.

In the average transmission / reception weight calculation unit 120, when calculating the average transmission weight corresponding to each component of the average transmission weight vector, the uplink channel information acquired by the channel information averaging circuit 121 is expressed by the formula ( 16), the downlink channel information is obtained by multiplying by the calibration coefficient given by the equation (17), and the average transmission weight is calculated. On the other hand, in the averaged transmission / reception weight calculation unit 120a, each component of the averaged reception weight calculated by the reception weight calculation circuit 122 is stored in the calibration coefficient storage circuit 124 as shown in the following equation (30). The average transmission weight is calculated by dividing by the calibration coefficient c _j ^(k) . That is, the average transmission / reception weight calculation unit 120a calculates the average transmission weight directly without acquiring downlink channel information.

Note that in Equation (30), the average transmission weight for the j-th antenna of the k-th frequency component is expressed as w _{T, j} ^(k) , in order to explicitly distinguish and explain the average reception weight and the average transmission weight. The average reception weight is expressed as w _{R, j} ^(k) . In addition, when Expression (23) is used as the average reception weight, the average transmission weight may be set as follows.

  This is because, with respect to the average reception weight, when the reception level fluctuates for each antenna element, the average reception weight is used in order to maximize the SNR of the signal after being multiplied and combined by the average reception weight vector. Although the absolute value of each component of the vector has been varied, it is not necessary to consider this effect when transmitting in the downlink, and the absolute value of each component of the averaged transmission weight vector is kept constant as in equation (22). In this sense, equation (31) multiplies equation (30) by the inverse coefficient of the absolute value.

FIG. 18 is a flowchart illustrating a process of calculating an average transmission weight in the second modification. The process of calculating the average transmission weight is a process performed after the process of calculating the average reception weight based on the uplink channel information shown in FIG.
When the average transmission / reception weight calculation unit 120a starts the process of calculating the average transmission weight (step S151), the transmission weight calculation circuit 126a receives the average reception weight w _{R, j} ^{(k )} And the calibration coefficient c _j ^(k) is acquired from the calibration coefficient storage circuit 124 (step S152).

The transmission weight calculation circuit 126a divides the average reception weight w _{R, j} ^(k) by the calibration coefficient c _j ^(k) to calculate the average transmission weight w _{T, j} ^(k) (step S153). The calculated average transmission weight w _{T, j} ^(k) is output and stored in the transmission weight storage circuit 127 (step S154), and the process is terminated (step S155). When equation (31) is used, a normalization process for dividing the average reception weight w _{R, j} ^(k) by the calibration coefficient c _j ^(k) and then dividing by the absolute value is added. You may do it.

In the base station apparatus 10 in the above-described embodiment and the first modification, the second received signal processing circuit 192 performs real-time according to the combination of L station terminal apparatuses that simultaneously transmit a signal sequence to the base station apparatus 10 by spatial multiplexing transmission. by using the transmission weight matrix W _T, and generates a signal sequence of L lines. As the averaged transmission weight vector, for example, a value calculated in advance based on channel information between each antenna element 101-1 to 101 -K and each terminal device is used.
Further, the base station apparatus 10 regards the L-system signal sequence generated by the first reception signal processing circuits 191-1 to 191-L as a signal received by virtual L antenna elements, and performs the second reception. Based on a known signal (such as a training signal or a preamble signal) included in the L system signal sequence, the signal processing circuit 192 generates channel information between the terminal device of the L station and the virtual L antenna elements. get. The second received signal processing circuit 192 calculates the real-time reception weight matrix W _R based on the acquired channel information, multiplies the real-time reception weight matrix W _R into a signal sequence of L lines. Thereby, it is possible to suppress the interference existing between the L signal series. The amount of processing in the second received signal processing circuit 192 depends on the spatial multiplexing number (L) and does not depend on the number of antenna elements (K) provided in the base station apparatus 10.

Thereby, in the base station apparatus 10 of the present embodiment, the signal sequence in the second received signal processing circuit 192 is also achieved when the channel vector correlation between the terminal apparatuses is reduced by increasing the number of antenna elements (K). It is possible to keep the amount of computation required for orthogonalization of the number of computations depending on the spatial multiplexing number (L). In other words, signal sequences can be orthogonalized with a load according to the usage status of wireless communication, and stable spatial multiplexing can be realized.
The average reception weight vector used in the first reception signal processing circuits 191-1 to 191-L may be calculated based on channel information that varies with time, and can be acquired in advance. Therefore, since it is not always necessary to acquire it during wireless communication by spatial multiplexing transmission, it is possible to reduce the load when performing wireless communication. Note that the L signal series obtained by the first reception signal processing circuits 191-1 to 191-L include an interference component between the signal series due to an error in channel information such as time variation. However, the interference component can be sufficiently suppressed by the processing in the second received signal processing circuit 192 using real-time information.

That is, the first reception signal processing circuits 191-1 to 191-L perform multiplication of K-dimensional averaged reception weight vectors that allow channel information errors due to channel time variations, and the second reception signal processing circuit 192 performs spatial processing. Multiply by an L × L real-time reception weight matrix for interference suppression that follows the time variation of the channel used in multiplex transmission. As a result, it is possible to increase the number of antenna elements of the base station apparatus 10 while suppressing an increase in calculation load for calculating the average reception weight vector, and to realize stable spatial multiplexing characteristics with a small calculation load. .
Further, in the base station apparatus 10, the first transmission signal processing circuits 193-1 to 193-L and the second transmission signal processing circuit 194 are replaced with the first reception signal processing circuits 191-1 to 191-L and the second reception signal. Since the operation is similar to that of the processing circuit 192, the same effect can be obtained in the transmission processing.

  In other words, by increasing the number of antennas of the base station apparatus, the correlation of channel vectors between the terminal apparatuses is reduced. As a result, even if a plurality of terminal apparatuses are spatially multiplexed, the orthogonalization loss at that time is greatly increased. Therefore, stable spatial multiplexing characteristics can be realized. On the other hand, the computation load for calculating the transmission / reception weight is the same as that for the non-redundant number of antennas, that is, it is possible to stably expect the desired characteristics while suppressing the circuit scale and reducing the hardware impact. A base station apparatus can be provided. At this time, even if there is some channel time variation in the channel information between the base station device and the terminal device, it is possible to realize transmission and reception weights that follow the time variation with a simple calculation at a level that allows real-time processing by hardware. In addition, stable multi-user MIMO spatial multiplexing processing is possible even in an environment with slight time fluctuations. In general, the signal detection processing of MIMO transmission has poor characteristics in linear signal processing using a (pseudo) inverse matrix or the like, and non-linear signal processing such as an MLD (Most Likelihood Detection) method that requires a large amount of calculation is required. In many cases, in the real-time transmission / reception weight matrix compressed to L × L size by the signal processing of the present invention, the correlation of each row (or column) vector is very small, and the characteristic deterioration due to linear processing is suppressed to a very limited level. Therefore, stable characteristics can be expected.

[Other supplementary items of the embodiment of the present invention]
Below, some supplementary matters regarding the embodiment according to the present invention are summarized.
In uplink channel estimation used for averaging transmission / reception weight calculation in the present invention, basically, a channel estimation training signal used for normal communication is used, but the base station apparatus and terminal apparatus are fixedly installed. In some cases, it is also possible to acquire a stable incident wave channel before the service is started. In this case, it is not always necessary to use a training signal for channel estimation used for normal communication as the training signal. For example, a training signal as shown in FIG. 19 may be used.

  FIG. 19 is a diagram showing another example of the training signal used for calculating the average transmission / reception weight in the present invention. In the figure, reference numerals 1-1 to 1-3 denote general OFDM symbols, reference numerals 2-1 to 2-3 denote effective signal areas not including guard intervals, and reference numerals 3-1 to 3-3 denote In the present invention, training signals are shown. Reference numerals 4-1 to 4-3 denote end regions of the signals, reference numerals 5-1 to 5-3 denote guard intervals, and reference numerals 6-1 to 6-3 denote actual channels. The signal period used for estimation is shown. The OFDM signal includes a plurality of subcarrier components, but in the figure, one subcarrier is extracted and illustrated as a sine wave.

  In the case of a conventional OFDM signal, a signal having a period of OFDM symbols (1-1 to 1-3) generates a signal region (2-1 to 2-3) effective as actual data, and the tail region of this signal. (4-1 to 4-3) are copied and pasted as guard intervals (5-1 to 5-3) in the head area of the signal to generate the entire OFDM symbols (1-1 to 1-3). It was. In normal communication, information on the amplitude and complex phase when the timing of the leading portion of the effective signal area (2-1 to 2-3) from which the guard interval is removed is extracted by timing detection and the timing is used as a starting point. Are obtained in the channel estimation.

  However, since it is sufficient to obtain the relative phase relationship of each antenna element in the calculation of the transmission / reception weight according to the present invention, it is not necessary to accurately grasp the initial complex phase, and an appropriate value such as the head of the OFDM symbol is not necessary. There is no need to start from a specific timing. Therefore, it is not necessary to be an OFDM signal in which a guard interval is set, and training signals (3-1 to 3-3) which are signals obtained by extracting effective signal regions (2-1 to 2-3) of OFDM symbols and continuing them. ) May be repeated many times. Here, since the sections are continuously connected, the symbol timing does not substantially make sense in the training signal over a plurality of periods. When the averaging process is performed, the reception side receives an arbitrary start timing different from the delimiter position with respect to the received training signals (3-1 to 3-3), for example, a signal cycle (6 -1 to 6-3), the signal is cut out, and the addition processing may be performed on the signals in the sections 6-1, 6-2, and 6-3.

  The circuit change at this time is that when the FFT circuits 108-1 to 108-K have received the above training signal in response to an instruction from the communication control circuit 110, the A / D converter 107-1 is used. The removal of the guard interval is omitted from the signal input from ˜107-K, the FFT processing is applied to the training signals (3-1 to 3-3) cut out at a predetermined timing, and the digital baseband The signal is separated into signals for each frequency component, and the signal is output to the average transmission / reception weight calculation unit 120. In normal operation, the signal is also output to the first reception signal processing circuits 191-1 to 191-L. However, since the training signal does not include transmission data, the first reception signal processing circuits 191-1 to 191-L are included. The output to the side becomes unnecessary.

  In the case of normal channel estimation, the averaging process is performed for individual sections 3-1, 3-2, 3-3 or 6-1 and 6-2 of the received training signals (3-1 to 3-3). , 6-3 is subjected to FFT and channel estimation, and then averaged. When this training signal is used, individual sections 3-1, 3-3-1 that are signals on the time axis are used. It is also possible to perform the same averaging process by averaging the sampling data in 2, 3-3 or 6-1, 6-2, 6-3 after addition at corresponding sample points. At this time, if there is a frequency error on the transmission side and the reception side, if the error is large enough to cause a problem in the averaging process, an existing frequency error correction technique is additionally applied as necessary. It doesn't matter.

  In the base station apparatus 10 in the above embodiment, a configuration is described in which the calibration coefficients shown in Expression (16) and Expression (17) are used when calculating downlink channel information from uplink channel information. did. However, as described above, the frequencies in the low noise amplifiers 103-1 to 103-K, the filters 106-1 to 106-K, the high power amplifiers 148-1 to 148-K, the filters 147-1 to 147-K, and the like. Adjust by analog signal processing so that the relative value (angle difference of complex phase) between the uplink and downlink of the amount of complex phase rotation for each component becomes a constant value in the circuit corresponding to all antenna elements. (For example, the complex phase of the uplink and downlink may be adjusted to be a constant value), it is not necessary to perform the process using the calibration coefficient. In this case, the process of acquiring the downlink channel information (FIG. 14) can be omitted, and the uplink channel information and the downlink channel information are equivalent, so the average transmission weight and the average reception The weight is a common value. In this case, the circuit related to the calculation of the average transmission weight in the downlink and the circuit related to the calculation of the average reception weight in the uplink can be shared.

Specifically, in the base station apparatus 10 in the first and second embodiments, the reception weight calculation circuit 122 and the reception weight storage circuit 123 perform both the calculation and storage of the average transmission weight and the average reception weight. It becomes composition. As a result, the calibration circuit 125, the transmission weight calculation circuit 126, the transmission weight storage circuit 127, and the calibration coefficient storage circuit 124 are omitted. However, the present invention is not limited to this, and the transmission weight is calculated by regarding the calibration coefficient as “1” in all combinations of antenna elements and frequency components, with the same configuration as the base station apparatus 10 in each embodiment. May be.
Furthermore, in this case, the rotation amount of the complex phase does not necessarily have to be the same (or the calibration coefficient is 1) in all the antenna elements of each frequency component, and this condition is exceptional in some small number of antenna elements. Even in a situation that is not satisfied, as long as at least half of the antenna elements satisfy this condition, the operation intended by the present invention can be realized as a whole.

  Further, for example, the configuration of the first reception signal processing circuits 191-1 to 191-L shown in FIG. 4, the configuration of the second reception signal processing circuit 192 shown in FIG. 5, and the second transmission signal processing circuit 194 shown in FIG. In the configuration diagram represented by the configuration, the configuration of the first transmission signal processing circuits 193-1 to 193-L shown in FIG. 9, the configuration of the average transmission / reception weight calculation units 121 and 121a shown in FIGS. Although processing for a plurality of frequency components has not been explicitly described, as described in the description of the individual processing, these signal processing is similarly performed for all frequency components. However, in an actual circuit configuration, the processing circuit may be individually mounted for each frequency component, or a single processing circuit may be used sequentially for each frequency component to reduce the circuit scale. An intermediate processing circuit may be used.

  Also, since all subcarriers are used for communication with the same terminal apparatus in the OFDM modulation scheme, the transmission / reception weights (average transmission / reception weight vector and real-time transmission / reception weight matrix) at that time are common combinations for all subcarriers. The transmission / reception weight for the terminal device is used. However, in OFDMA, since allocations to different combinations of terminal devices in a patchwork pattern on the time axis and the frequency axis are gathered together, terminals allocated for each time (OFDM symbol) and frequency (subcarrier) It is necessary to use transmission / reception weights for the device. In this case, the first reception signal processing circuits 191-1 to 191-L, the second reception signal processing circuit 192, the first transmission signal processing circuits 193-1 to 193-L, and the second transmission signal processing circuit 194 are: It does not correspond to terminal devices that are the same communication partner regardless of frequency and time (symbol), but is a terminal device that is a communication partner when attention is paid to each frequency component or each time (OFDM symbol). It should be understood that However, except for the difference, OFDM and OFDMA can be processed in exactly the same way. In this specification, the description has been focused on OFDM. However, the present invention can be applied to OFDMA as well. it can.

  In addition, there are various operational variations for SC-FDE, but the received signal processing after the signals transmitted from the antenna elements are combined in space by multiplying the average transmission weight on the transmission side, In each of the above configuration examples, the processing performed in the conventional SC-FDE is applied as it is in any of the received signal processing after the reception side multiplies the average reception weight and the signals of the respective antenna elements are added and synthesized. Therefore, the present invention is applicable to all variations of SC-FDE.

  Further, when the signals multiplied by the average reception weight are added and combined over a plurality of antenna elements, it is not always necessary to add and combine over all the antenna elements. Even if addition synthesis is performed, the operation intended by the present invention can be realized as a whole, and as a result, similar effects can be obtained. Similarly, when adding and combining signals addressed to a plurality of terminal devices multiplied by the average transmission weight for each antenna element, the addition and combining are not performed for all the antenna elements, but in some antenna elements. Even if addition synthesis is performed, the operation intended by the present invention can be realized as a whole.

  Also, as a method for acquiring downlink channel information, in addition to the method using uplink channel information shown in this specification, a training signal is transmitted directly from each antenna of the base station apparatus in downlink. A method is also conceivable in which channel information acquired by the terminal device that has received the training signal is fed back to the base station device using a control line. However, in the present invention, since channel information is exchanged relatively frequently due to the necessity of acquiring a real-time transmission / reception weight matrix, such a method of feeding back downlink channel information using a control line reduces MAC efficiency. This is not a preferred embodiment. However, if any contrivance can be made, the downlink channel information acquired in this way is directly input from the communication control circuit 110 to the transmission weight calculation circuit 126 in the average transmission / reception weight calculation unit 120 and used. Thus, the same effect can be obtained even when the transmission weight is calculated. However, even in this case, transmission of a training signal from each terminal device is indispensable for acquiring uplink channel information, and this point is exactly the same as the above-described present invention.

  Similarly, the base station apparatus 10 according to the embodiment performs the averaging process shown in FIG. 13 as the process after obtaining the relative components of the uplink channel information shown in FIGS. Downlink channel information is acquired by the calibration process, and the average transmission / reception weight calculation process shown in FIG. 15 is subsequently performed. However, since the weights shown in the equations (22) to (23) correspond to simple complex phase component extraction, the weight calculation processing shown in FIG. 15 is performed after the relative components shown in FIG. By replacing steps S131-1 to S131-Q in FIG. 13 with acquisition of individual reception weights and replacing the averaging target shown in step S133 with this reception weight, an approximately equivalent average reception weight is acquired. It is possible. That is, in the configuration example of each embodiment, the physical quantity to be averaged is the relative component of the channel information. However, the reception weight calculated from the relative component of the channel information can be replaced with the physical quantity to be averaged. It is.

Further, in the installation example of the base station apparatus included in the wireless communication system illustrated in FIG. 27, the terminal apparatuses 12-1 to 12-2 are illustrated as including one antenna, but the terminal apparatus includes a plurality of antennas. Even if it is provided, it is possible to perform the same processing. In principle, if the terminal apparatuses 12-1 to 12-2 are provided with a plurality of antennas, a plurality of signal sequences can be spatially multiplexed in one terminal station. In this case, the present invention can be similarly implemented by regarding each antenna of the terminal devices 12-1 to 12-2 as an antenna element of each terminal station. However, in the embodiment, since it is assumed that the terminal devices 12-1 to 12-2 and the antenna elements 13-1 to 13-4 of the base station device are in a line-of-sight environment, generally, the base station device It is often difficult to perform MIMO transmission between a single terminal device (after the second eigenvalue approaches zero).
Therefore, when the terminal station is provided with a plurality of antennas, it is practical to operate transmission / reception of a single signal sequence as a diversity configuration of a plurality of antennas. In this case, by combining a plurality of antennas with appropriate weights, it can be regarded as a virtual one antenna, and the same processing is realized with this virtual one antenna. Then, the embodiment can be applied in exactly the same manner.

  Furthermore, in the above description of the operation principle and each embodiment, the channel information and transmission / reception weight corresponding to each antenna element have been described. However, the vector configured with the channel information or transmission / reception weight of each antenna element as a component. Has an effective meaning in the direction indicated by the vector. For this reason, the vector obtained by multiplying a certain vector by a predetermined coefficient is the same in direction, so that a vector obtained by multiplying a certain coefficient for each antenna element has all equivalent meanings without depending on the coefficient to be multiplied. Will have.

  On the other hand, as shown in FIG. 27, since the antennas of the base station device and the terminal device are each assumed to be a line-of-sight environment or an environment close to the line-of-sight environment, the intensity and amplitude of the signal received by each antenna element is approximately Expected to be a constant value. For this reason, for example, the vector of channel information of each antenna element is effectively not so significant in the absolute value of each component of the vector, and the channel information value is normalized (the channel information is the absolute value). (Complex number obtained by dividing by) is significant information. Therefore, the processing in which the “channel information” used in the description of the above-described operation principle and description is approximately regarded as “value obtained by standardizing the value of the channel information” is the related technology of each embodiment and the present invention. In this sense, the above-mentioned “channel information” includes up to “a value obtained by standardizing the value of channel information” in a broad sense.

Furthermore, in the present specification, for convenience of explanation, “row vector” and “column vector” are dealt with without much distinction. For example, the channel information vector h _i in the expression (3) is a row vector, the transmission weight vector w _j is a column vector, and “transpose” or the like if it is a strict mathematical notation that unifies the direction of vector arrangement. Should be written using the symbol etc. However, the information required in the practice of the present invention is the value of each component of the vector, and it does not make much sense whether the vector is a row vector or a column vector. The description does not distinguish between “vector” and “column vector”.

  Note that a program for realizing the functions of the base station apparatus in each embodiment is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read by a computer system and executed to transmit the program. Processing for calculating weights, reception weights, and transmission / reception weights may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

1-1, 1-2, 1-3 OFDM symbol 2-1, 2-2, 2-3 Effective signal region 3-1, 3-2, 3-3 Training signal 4-1, 4-2, 4 -3 Trailing area 5-1, 5-2, 5-3 Guard interval 6-1, 6-2, 6-3 Signal period 10 Base station device 11 Building 12-1, 12-2 Terminal device 13-1, 13-2, 13-3, 13-4 Antenna elements of base station apparatus 14-1, 14-2, 14-3 Ground moving body 15-1, 15-2 Building 21-1, 21-2, 21 -3 High power amplifier (HPA)
22-1, 22-2, 22-3 Low noise amplifier (LNA)
23-1, 23-2, 23-3 Time division switch (TDD-SW)
24-1, 24-2, 24-3 Antenna elements 25-1, 25-2, 25-3 Radio module 26-1, 26-2, 26-3 Antenna terminal 27 Coaxial cable 80 Base station device 81 Transmitter 85 Receiving unit 87 Interface circuit 88 MAC layer processing circuit 100 Receiving unit 101-1, 101-2, 101-K, 101-j Antenna element 102-1, 102-2, 102-K TDD switch 103-1, 103-2 , 103-K Low noise amplifier (LNA)
104 local oscillators 105-1, 105-2, 105-K mixers 106-1, 106-2, 106-K filters 107-1, 107-2, 107-K A / D converters 108-1, 108-2 108-K FFT circuit 110 Communication control circuit 115 Storage circuit 120 120a Average transmission / reception weight calculation unit 121 Channel information averaging circuit 122 Reception weight calculation circuit 123 Reception weight storage circuit 124 Calibration coefficient storage circuit 125 Calibration circuit 126 126a Transmission Weight Calculation Circuit 127 Transmission Weight Storage Circuit 130 Real Time Transmission Weight Matrix Storage Unit 131 Real Time Transmission Weight Matrix Calculation Unit 140 Transmission Units 142-1, 142-2, 142-K Addition / Synthesis Circuits 143-1, 143-2, 143 K IFFT & GI adding circuit 144-1, 144-2, 144-K D / A converter 145 Local oscillator 146-1, 146-2, 146-K mixer 147-1, 144-2, 147-K filter 148-1 148-2, 148-K High Power Amplifier (HPA)
170 Interface circuit 180 MAC layer processing circuit 181 Scheduling processing circuit 191-1, 191-2, 191-L, 191-j First reception signal processing circuit 192 Second reception signal processing circuit 193-1, 193-2, 193 L, 193-j first transmission signal processing circuit 194 second transmission signal processing circuit 201-1, 201-2, 201-K multiplier 202 adder 203 averaged reception weight vector component distributor 204 real-time transmission / reception weight calculation unit 205 Matrix multipliers 206-1, 206-2, 206-L Signal detection circuit 211-1, 211-2, 211-K Multiplier 212 Signal replicator 213 Averaged transmission weight vector component distributor 214 Matrix multiplier 215-1 215-2, 215-L Modulation circuit 801 Base station apparatus 802, 802 1, 802-2, 802-3 Terminal devices 811, 811-1, 811-2, 811-L Transmission signal processing circuit 812-1, 812-2, 812-K Addition / synthesis circuit 813-1, 813-2, 813-K IFFT & GI adding circuit 814-1, 814-2, 814 -K D / A converter 815 Local oscillator 816-1, 816-2, 816 -K mixer 817-1, 817-2, 817 -K filter 818 -1,818-2,818-K High power amplifier (HPA)
819-1, 819-2, 819-K Antenna element 820 Communication control circuit 830 Transmission weight processing unit 831 Channel information acquisition circuit 832 Channel information storage circuit 833 Multi-user MIMO transmission weight calculation circuit 851-1, 851-2, 851- K antenna element 852-1, 852-2, 852-K Low noise amplifier (LNA)
853 Local oscillators 854-1, 854-2, 854-K mixers 855-1, 855-2, 855-K filters 856-1, 856-2, 856-K A / D converters 857-1, 857-2 857-K FFT circuit 858-1, 858-2, 858-L received signal processing circuit 860 received weight processing unit 861 channel information estimation circuit 862 multiuser MIMO received weight calculation circuit 881 scheduling processing circuit

Claims (11)

A wireless communication system comprising a base station device having a plurality of antenna elements and a plurality of terminal devices, wherein the base station device and the terminal devices can perform spatial multiplexing transmission at the same time on the same frequency A base station apparatus in which
A radio signal receiving unit that is provided for each antenna element and separates a received signal received by the antenna element into a signal for each frequency component;
Receive weight vectors for each frequency component for acquiring uplink channel information based on the training signal transmitted from the terminal apparatus and synthesizing signals received by the plurality of antenna elements based on the channel information. For each combination of the antenna element of the terminal device and a plurality of antenna elements of the base station apparatus, a reception weight vector calculation unit for storing the reception weight vector,
For each terminal device that performs spatial multiplexing transmission, the reception weight vector of each frequency component corresponding to the terminal device among the reception weight vectors calculated by the reception weight vector calculation unit is converted into each frequency component by the radio signal reception unit. A plurality of first received signal processing units for multiplying the separated signals and adding and combining the multiplication results;
A second received signal processing unit that suppresses an interference component included in the signal by using a reception weight matrix calculated based on the signal of each frequency component calculated by addition synthesis by the plurality of first received signal processing units. When,
A base station apparatus comprising: The base station apparatus according to claim 1,
The second received signal processor is
The signals of the respective frequency components calculated by the addition and synthesis by the plurality of first received signal processing units are regarded as signals received by the number of spatially multiplexed virtual antenna elements, and spatial multiplexing transmission is performed with the virtual antenna elements. Channel information between the terminal device and an antenna element is calculated, and the reception weight matrix is calculated based on the calculated channel information. The base station apparatus according to claim 1 or 2, wherein
A transmission signal generation unit that separates each of the signals transmitted to the plurality of terminal devices into signals for each frequency component;
Obtaining downlink channel information based on either a training signal received from the terminal device or information fed back from the terminal device, and signals transmitted from the plurality of antenna elements based on the channel information A transmission weight vector for each frequency component for in-phase synthesis in the terminal device is calculated for each combination of the antenna element of the terminal device and a plurality of antenna elements of the base station device, and the transmission weight vector is stored. A vector calculation unit;
Frequency components obtained by separating transmission weight matrices determined so that mutual interference components are suppressed in the destination terminal device for each of the transmission signals spatially multiplexed to the plurality of terminal devices by the transmission signal generation unit A second transmission signal processing unit that multiplies the signal for each signal;
For each terminal device that is the destination in spatial multiplexing transmission, among the frequency component signals calculated by multiplication by the second transmission signal processing unit, each frequency component signal that is destined for the terminal device corresponds to the antenna element. A first transmission signal processing unit that duplicates the copied signal by a transmission weight vector of each frequency component corresponding to the combination of the antenna element of the terminal device and the plurality of antenna elements of the base station device When,
A signal of each frequency component provided for each antenna element and calculated by multiplication by the first transmission signal processing unit is combined with a signal corresponding to the antenna element and a signal of the destination terminal device in spatial multiplexing transmission A radio signal transmission unit that transmits the transmission signal from the antenna element;
The base station apparatus further comprising: The base station apparatus according to claim 3, wherein
The second transmission signal processor is
A base station apparatus, wherein a matrix obtained by transposing a reception weight matrix calculated by the second reception signal processing unit is used as the transmission weight matrix. The base station apparatus according to claim 3, wherein
A base station further comprising: a transmission weight matrix calculating unit that calculates the transmission weight matrix based on a value obtained by multiplying the vector configured by the downlink channel information and the transmission weight vector. apparatus. A wireless communication system comprising a base station device having a plurality of antenna elements and a plurality of terminal devices, wherein the base station device and the terminal devices can perform spatial multiplexing transmission at the same time on the same frequency A wireless communication method performed by a base station apparatus in
A radio signal receiving step that is provided for each antenna element and separates a received signal received by the antenna element into a signal for each frequency component;
Receive weight vectors for each frequency component for acquiring uplink channel information based on the training signal transmitted from the terminal apparatus and synthesizing signals received by the plurality of antenna elements based on the channel information. For each combination of the antenna element of the terminal device and the plurality of antenna elements of the base station apparatus, and a reception weight vector calculation step of storing the reception weight vector,
For each terminal apparatus that performs spatial multiplexing transmission, the reception weight vector of each frequency component corresponding to the terminal apparatus among the reception weight vectors calculated in the reception weight vector calculation step is converted into each frequency component in the radio signal reception step. A first received signal processing step of multiplying the separated signals and adding and combining the multiplication results;
A second received signal processing step of suppressing an interference component included in the signal using a reception weight matrix calculated based on the signal of each frequency component calculated by addition synthesis in the first received signal processing step;
A wireless communication method comprising: The wireless communication method according to claim 6 , comprising:
In the second received signal processing step ,
Wherein the signal before Symbol each frequency component calculated by additive synthesis in the first received signal processing step, is regarded as a signal received at the virtual antenna elements of the number of spatial multiplexing, it performs the virtual antenna elements and spatial multiplexing transmission A wireless communication method , comprising: calculating channel information with an antenna element of a terminal device, and calculating the reception weight matrix based on the calculated channel information. A wireless communication method according to claim 6 or 7 , wherein
A transmission signal generation step of separating each of the signals transmitted to the plurality of terminal devices into signals for each frequency component;
Obtaining downlink channel information based on either a training signal received from the terminal device or information fed back from the terminal device, and signals transmitted from the plurality of antenna elements based on the channel information A transmission weight vector for each frequency component for in-phase synthesis in the terminal device is calculated for each combination of the antenna element of the terminal device and a plurality of antenna elements of the base station device, and the transmission weight vector is stored. A vector calculation step ;
Frequency components obtained by separating the transmission weight matrix determined so that mutual interference components are suppressed in the destination terminal device for each of the transmission signals spatially multiplexed to the plurality of terminal devices by the transmission signal generation step A second transmission signal processing step of multiplying each signal;
For each terminal device that is the destination in spatial multiplexing transmission, among the frequency component signals calculated by multiplication in the second transmission signal processing step, each frequency component signal that is destined for the terminal device corresponds to the antenna element. A first transmission signal processing step of multiplying the duplicated signal by a transmission weight vector of each frequency component corresponding to the combination of the antenna element of the terminal device and the plurality of antenna elements of the base station device When,
The signal of each frequency component, which is performed for each antenna element and is calculated by multiplication in the first transmission signal processing step, is a signal corresponding to the antenna element and a signal of the terminal device as a destination in spatial multiplexing transmission. A radio signal transmitting step of combining and transmitting as the transmission signal from the antenna element;
A wireless communication method , further comprising : A wireless communication system comprising a base station device having a plurality of antenna elements and a plurality of terminal devices, wherein the base station device and the terminal devices can perform spatial multiplexing transmission at the same time on the same frequency Because
The base station device
A radio signal receiving unit that is provided for each antenna element and separates a received signal received by the antenna element into a signal for each frequency component;
Receive weight vectors for each frequency component for acquiring uplink channel information based on the training signal transmitted from the terminal apparatus and synthesizing signals received by the plurality of antenna elements based on the channel information. For each combination of the antenna element of the terminal device and a plurality of antenna elements of the base station apparatus, a reception weight vector calculation unit for storing the reception weight vector,
For each terminal device that performs spatial multiplexing transmission, the reception weight vector of each frequency component corresponding to the terminal device among the reception weight vectors calculated by the reception weight vector calculation unit is converted into each frequency component by the radio signal reception unit. A plurality of first received signal processing units for multiplying the separated signals and adding and combining the multiplication results;
A second received signal processing unit that suppresses an interference component included in the signal by using a reception weight matrix calculated based on the signal of each frequency component calculated by addition synthesis by the plurality of first received signal processing units. When,
A wireless communication system comprising: The wireless communication system according to claim 9 , wherein
The second received signal processor is
The signals of the respective frequency components calculated by the addition and synthesis by the plurality of first received signal processing units are regarded as signals received by the number of spatially multiplexed virtual antenna elements, and spatial multiplexing transmission is performed with the virtual antenna elements. A wireless communication system , wherein channel information between the terminal device and an antenna element is calculated, and the reception weight matrix is calculated based on the calculated channel information. A wireless communication system according to claim 9 or 10 , wherein
The base station device
A transmission signal generation unit that separates each of the signals transmitted to the plurality of terminal devices into signals for each frequency component;
Obtaining downlink channel information based on either a training signal received from the terminal device or information fed back from the terminal device, and signals transmitted from the plurality of antenna elements based on the channel information A transmission weight vector for each frequency component for in-phase synthesis in the terminal device is calculated for each combination of the antenna element of the terminal device and a plurality of antenna elements of the base station device, and the transmission weight vector is stored. A vector calculation unit;
Frequency components obtained by separating transmission weight matrices determined so that mutual interference components are suppressed in the destination terminal device for each of the transmission signals spatially multiplexed to the plurality of terminal devices by the transmission signal generation unit A second transmission signal processing unit that multiplies the signal for each signal;
For each terminal device that is the destination in spatial multiplexing transmission, among the frequency component signals calculated by multiplication by the second transmission signal processing unit, each frequency component signal that is destined for the terminal device corresponds to the antenna element. A first transmission signal processing unit that duplicates the copied signal by a transmission weight vector of each frequency component corresponding to the combination of the antenna element of the terminal device and the plurality of antenna elements of the base station device When,
A signal of each frequency component provided for each antenna element and calculated by multiplication by the first transmission signal processing unit is combined with a signal corresponding to the antenna element and a signal of the destination terminal device in spatial multiplexing transmission A radio signal transmission unit that transmits the transmission signal from the antenna element;
A wireless communication system , further comprising:

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