JP2012248968A - Radio communication device and communication control method - Google Patents

Abstract

A wireless communication apparatus and a communication control method capable of performing appropriate multi-antenna control while reducing a processing load.
When UE1 receives a downlink radio signal using four downlink resource blocks from eNB2, if a difference in received power values of the downlink radio signal is equal to or greater than a threshold value, UE1 A reception weight is calculated, and if the difference between the reception power values of the downlink radio signals is less than the threshold, one reception weight corresponding to four resource blocks is calculated. Furthermore, UE1 performs AAS using the calculated reception weight and channel equalization processing.
[Selection] Figure 2

Description

  The present invention relates to a multicarrier radio communication apparatus that receives a radio signal using a plurality of antennas, and a communication control method in the radio communication apparatus.

  Conventionally, a multicarrier wireless communication apparatus that receives a wireless signal using a plurality of antennas employs an interference suppression technique. For example, in Patent Document 1, the wireless communication device sets an antenna weight for each antenna for adaptive array control (beamforming and null steering) based on the reception state of a known signal (pilot signal) that is a wireless signal. calculate.

Japanese Patent No. 3497672

  In consideration of frequency selective fading, it is desirable that the above-described wireless communication apparatus calculates an antenna weight for each frequency band as narrow as possible. However, the calculation of the antenna weight for each narrow frequency band by the wireless communication device leads to an increase in processing load on the wireless communication device. On the other hand, when the wireless communication apparatus calculates an antenna weight corresponding to a wide frequency band, the processing load is reduced. However, when the frequency selective fading is large, even if the wireless communication apparatus applies the calculated antenna weight, beam forming or null steering may not be performed appropriately.

  In view of the above problems, an object of the present invention is to provide a wireless communication apparatus and a communication control method that enable appropriate multi-antenna control while reducing the processing load.

  In order to solve the above-described problems, the present invention has the following features. A first feature of the present invention is a multi-carrier wireless communication apparatus (a multi-carrier wireless communication apparatus) that uses a plurality of antennas (adaptive array antenna 108A, adaptive array antenna 108B, adaptive array antenna 108C, and adaptive array antenna 108D) to receive wireless signals. UE1), where the radio communication apparatus performs multi-antenna control using each of a plurality of frequency bands as a unit of control when the frequency selective fading is considered to be large, and the frequency selective fading is small When considered, the gist is to perform multi-antenna control using the plurality of frequency bands as a unit of control.

  Such a radio communication apparatus performs multi-antenna control using each of a plurality of frequency bands as a unit of control when the frequency selective fading is considered to be large, and when the frequency selective fading is considered to be small. Performs multi-antenna control using the plurality of frequency bands as a unit of control. Therefore, when frequency selective fading is considered to be large, multi-antenna control is performed for each narrow frequency band, thereby enabling appropriate multi-antenna control, and when frequency selective fading is considered to be small. By performing multi-antenna control over a wide frequency band, it is possible to perform appropriate multi-antenna control while reducing the processing load.

  A feature of the present invention is that the wireless communication apparatus calculates an antenna weight for each unit of control.

  The gist of the present invention is that the wireless communication apparatus calculates at least one of a beamforming antenna weight and a null steering antenna weight.

  A feature of the present invention is that the wireless communication apparatus applies the antenna weight to a frequency band to be estimated.

  The gist of the present invention is that the wireless communication apparatus determines that frequency selective fading is large when a difference in received power between known signals distributed in the frequency direction is equal to or greater than a threshold value. .

  A feature of the present invention is a communication control method in a multi-carrier wireless communication apparatus that receives a wireless signal using a plurality of antennas, and the wireless communication apparatus is considered to have large frequency selective fading Performing multi-antenna control with each of a plurality of frequency bands as a unit of control, and when the frequency selective fading is considered to be small, performing the multi-antenna control with the plurality of frequency bands as a unit of control It is made to include.

  According to the present invention, it is possible to perform appropriate multi-antenna control while reducing the processing load.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a block diagram of the radio | wireless terminal which concerns on embodiment of this invention. It is a figure which shows the format of PDSCH based on embodiment of this invention. It is a figure which shows arrangement | positioning of the known signal based on embodiment of this invention. It is a figure which shows an example of frequency selective fading based on embodiment of this invention. It is a flowchart which shows operation | movement of the radio | wireless terminal based on embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, the configuration of the wireless communication system, the operation of the wireless terminal, the operation / effect, and other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Configuration of Radio Communication System (1.1) Overall Schematic Configuration of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system 10 according to an embodiment of the present invention.

  A wireless communication system 10 shown in FIG. 1 is a wireless communication system compatible with LTE (Long Term Evolution) for which a standard has been established in 3GPP (Third Generation Partnership Project). The radio communication system 10 includes radio terminals (UE1 and radio base station (eNB) 2).

  In FIG. 1, eNB2 comprises E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) with the other eNB which is not illustrated. UE1 exists in the cell 3 which is a communicable area which eNB2 provides. In FIG. 1, only one UE 1 is shown, but a plurality of UEs 1 actually exist in the cell 3.

  OFDMA (Orthogonal Frequency Division Multiplexing Access) is used for downlink radio communication between the eNB 2 and the UE 1, and SC-FDMA (Single Carrier Frequency Division Multiple Access) is adopted for uplink radio communication. Here, “downlink” means a direction from eNB2 toward UE1, and “uplink” means a direction from UE1 toward eNB2.

  The eNB 2 allocates a resource block (RB: Resource Block) as a radio resource to the UE 1 in the cell 3.

  Resource blocks include a downlink resource block (downlink RB) used for downlink radio communication and an uplink resource block (uplink RB) used for uplink radio communication. A plurality of downlink resource blocks are arranged in the frequency direction. Similarly, a plurality of uplink resource blocks are arranged in the frequency direction.

  The downlink resource block is divided into a control information channel (PDCCH: Physical Downlink Control CHannel) for downlink control information transmission and a shared data channel (PDSCH: Physical Downlink Shared CHannel) for downlink user data transmission in the time direction. Composed.

  On the other hand, in the uplink resource block, control information channels (PUCCH: Physical Uplink Control CHannel) for uplink control information transmission are configured at both ends of all frequency bands that can be used for uplink radio communication. A shared data channel (PUSCH: Physical Uplink Shared CHannel) for user data transmission is configured.

  Hereinafter, the case where radio | wireless communication is performed between eNB2 and UE1 is demonstrated. In the following, it is assumed that a downlink resource block and an uplink resource block are allocated to UE1 in the initial state.

(1.2) Configuration of Radio Terminal FIG. 2 is a configuration diagram of UE1. As shown in FIG. 2, UE1 is an adaptive array radio terminal, and includes a control unit 102, a storage unit 103, a radio frequency (RF) reception processing unit 104, and a base band (BB) processing unit. 106, an adaptive array antenna 108A, an adaptive array antenna 108B, an adaptive array antenna 108C, and an adaptive array antenna 108D. In addition, UE1 shown in FIG. 2 has shown only the structure required in this embodiment.

  The control part 102 is comprised by CPU, for example, and controls the various functions which UE1 comprises. The memory | storage part 103 is comprised by memory, for example, and memorize | stores the various information used for control etc. in UE1.

  The RF reception processing unit 104 receives a downlink radio signal in the radio frequency band from the eNB 2 via the adaptive array antenna 108A to the adaptive array antenna 108D. The RF reception processing unit 104 includes a low noise amplifier (LNA) and a mixer (not shown). The RF reception processing unit 104 amplifies the received downlink radio signal in the radio frequency band, and converts (down-converts) it into a baseband signal. Further, the RF reception processing unit 104 outputs the baseband signal to the BB processing unit 106.

  The BB processing unit 106 includes a CP (Cyclic Prefix) removal unit 122, an FFT (Fast Fourier Transform) processing unit 124, an AAS (Adaptive Array System) processing unit 126, a channel equalization unit 128, and a demodulation decoding unit 130.

  CP removing section 122 removes CP (Cyclic Prefix) from the input baseband signal. The CP is a copy of the end portion of the OFDM symbol and is included in a guard interval period provided to suppress intersymbol interference caused by multipath. The FFT processing unit 124 performs a fast Fourier transform on the baseband signal from which the CP has been removed to obtain a frequency domain signal.

  The AAS processing unit 126 is an antenna that has a maximum signal-to-interference noise ratio (SINR) when receiving a downlink radio signal from the eNB 2 for each adaptive array antenna 108A to adaptive array antenna 108D based on the frequency domain signal. The weight (reception weight) is calculated.

  FIG. 3 is a diagram illustrating a PDCCH format corresponding to one resource block (RB). As shown in FIG. 3, the PDCCH is configured by one subframe having a time length of 1 [ms] in the time direction. The subframe includes time zones S1 to S14. Of these time zones S1 to S14, time zones S1 to S7 constitute the first half slot (slot 1), and time zones S8 to S14 constitute the second half slot (slot 2). . The central time zone S4 in the slot 1 is used for transmission of a pilot signal which is a known signal. Similarly, the central time zone S11 in the slot 2 is used for transmission of a pilot signal which is a known signal.

  Further, as shown in FIG. 3, the PDCCH has a frequency width of 180 [kHz] in the frequency direction. The PDCCH is composed of 12 subcarriers F1 to F12 having a frequency width of 15 [kHz].

  FIG. 4 is a diagram showing an arrangement of pilot signals. As shown in FIG. 4, in this embodiment, subcarriers used for pilot signal transmission are arranged at three subcarrier intervals. Focusing on one downlink resource block, subcarriers F3, F7, and F11 are subcarriers used for transmission of pilot signals.

  The AAS processing unit 126 calculates the reception weight as follows. In the following, it is assumed that four downlink resource blocks having continuous frequencies are allocated to UE1.

  Specifically, the AAS processing unit 126 detects a pilot signal included in a frequency domain signal corresponding to four downlink resource blocks. As described above, one pilot resource block includes three pilot signals. Therefore, the AAS processing unit 126 detects 12 pilot signals included in the frequency domain signal corresponding to the four downlink resource blocks.

  The AAS processing unit 126 measures the received power of the 12 detected pilot signals. Next, the AAS processing unit 126 acquires a difference (received power difference) between the maximum received power and the minimum received power among the measured received powers.

  The AAS processing unit 126 considers that frequency selective fading is large when the received power difference is equal to or greater than a predetermined threshold value α. In this case, the AAS processing unit 126 determines to calculate a reception weight for each downlink resource block. On the other hand, if the received power difference is less than the predetermined threshold value α, the AAS processing unit 126 considers that the frequency selective fading is small. In this case, the AAS processing unit 126 determines to calculate one reception weight corresponding to four downlink resource blocks.

  FIG. 5 is a diagram illustrating an example of frequency selective fading. FIG. 5A shows a large received power difference d, and FIG. 5B shows a small received power difference d. The AAS processing unit 126 determines to calculate the reception weight for each downlink resource block when the received power difference d in FIG. In addition, when the reception power difference d in FIG. 5B is less than the threshold value α, the AAS processing unit 126 determines to calculate one reception weight corresponding to four downlink resource blocks.

  When calculating the reception weight for each downlink resource block, the AAS processing unit 126 derives one reception power value for each downlink resource block from the reception power values of three pilot signals included in the downlink resource block. To do. For example, the AAS processing unit 126 calculates an average value of received power values of three pilot signals. Alternatively, the AAS processing unit 126 acquires an intermediate value that is the second largest value among the received power values of the three pilot signals.

  Next, AAS processing section 126 calculates a reception weight corresponding to the PUSCH frequency band in one downlink resource block, based on one derived reception power value.

  The above processing is performed for each of the four downlink resource blocks and for each adaptive array antenna 108A to adaptive array antenna 108D, whereby 16 reception weights are calculated.

  On the other hand, when calculating one reception weight corresponding to four downlink resource blocks, the AAS processing unit 126 determines one reception power value from reception power values of twelve pilot signals included in the four downlink resource blocks. Is derived. For example, the AAS processing unit 126 calculates an average value of received power values of 12 pilot signals. Alternatively, the AAS processing unit 126 acquires an intermediate value that is the sixth or seventh largest value among the received power values of the twelve pilot signals.

  Next, AAS processing section 126 calculates reception weights corresponding to the frequency bands of PUSCH in the four downlink resource blocks based on one derived reception power value.

  The above processing is performed for each adaptive array antenna 108A to adaptive array antenna 108D, whereby four reception weights are calculated.

  After that, the AAS processing unit 126 applies the reception weight to the corresponding channel estimation target frequency band. Specifically, the AAS processing unit 126 performs weighting processing for combining the calculated reception weights and the frequency domain signals that are sequentially input. Further, the AAS processing unit 126 outputs the frequency domain signal from the FFT processing unit 124 to the channel equalization unit 128.

  The channel equalization unit 128 performs channel equalization processing on the input frequency domain signal.

  The demodulation and decoding unit 130 performs demodulation and decoding processing on the signal that has been subjected to channel equalization processing. Thereby, data transmitted by the eNB 2 is obtained. Data is output to the control unit 102.

(2) Operation of Radio Terminal FIG. 6 is a flowchart showing the operation of UE1.

  In step S101, eNB2 transmits a downlink radio signal in a radio frequency band using four downlink resource blocks having continuous frequencies. UE1 receives a downlink radio signal in a radio frequency band.

  In step S102, UE1 measures the received power of the pilot signal included in the downlink radio signal corresponding to the received four downlink resource blocks.

  In step S103, UE1 determines whether or not the difference (reception power difference) d between the maximum received power value and the minimum received power value among the received power values of the pilot signal is greater than or equal to a threshold value α.

  When the received power difference d is greater than or equal to the threshold value α, in step S104, the UE1 calculates an antenna weight (reception weight) for each downlink resource block. On the other hand, when the received power difference d is less than the threshold value α, in step S105, UE1 calculates one antenna weight (reception weight) corresponding to four downlink resource blocks.

  After the reception weight is calculated in step S104 or step S105, in step S106, the UE 1 performs a process (AAS process) for applying the reception weight to the corresponding channel estimation target frequency band.

  In step S107, UE1 performs a channel equalization process.

(3) Action / Effect As described above, according to the present embodiment, when UE1 receives a downlink radio signal using four downlink resource blocks from eNB2, the received power value of the downlink radio signal is determined. If the difference is greater than or equal to the threshold, a reception weight is calculated for each downlink resource block. If the difference in received power value of the downlink radio signal is less than the threshold, one reception corresponding to four resource blocks is received. Calculate the weight. Furthermore, UE1 performs AAS using the calculated reception weight and channel equalization processing.

  Therefore, when the frequency selective fading is considered to be large, the UE 1 can perform appropriate multi-antenna control by performing multi-antenna control for each narrow frequency band, and the frequency selective fading is considered to be small. In, by performing multi-antenna control in a wide frequency band, it is possible to perform appropriate multi-antenna control while reducing the processing load.

(4) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment described above, the UE 1 calculates the reception weight for each downlink resource block based on the difference in the reception power value of the pilot signal included in the downlink radio signal, and one reception weight corresponding to four downlink resource blocks. The calculation was switched. However, the UE 1 calculates a reception weight for each downlink resource block based on a difference in received power of other known signals included in the downlink radio signal and calculates one reception weight corresponding to four downlink resource blocks. May be switched.

  In the above-described embodiment, when the difference in the received power value of the pilot signal included in the downlink radio signal is equal to or greater than the threshold, the UE 1 calculates the reception weight for each downlink resource block and is less than the threshold. In this case, one reception weight corresponding to four downlink resource blocks was calculated. However, the reception weight calculation method is not limited to this. UE1 calculates one reception weight corresponding to the first predetermined number of downlink resource blocks when the difference between the received power values of the pilot signals included in the downlink radio signal is equal to or greater than the threshold, and less than the threshold In some cases, one reception weight corresponding to more downlink resource blocks than the first predetermined number may be calculated.

  In the above-described embodiment, the UE 1 that is an LTE radio terminal has been described. However, the present invention can be similarly applied to any multi-carrier radio communication apparatus that receives a radio signal using a plurality of antennas.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  UE1 ... Radio terminal, eNB2 ... Radio base station, 3 ... Cell, 10 ... Radio communication system, 102 ... Control unit, 103 ... Storage unit, 104 ... RF reception processing unit, 106 ... BB processing unit, 107 ... RF transmission processing unit 108A, 108B, 108C, 108D ... adaptive array antenna, 120 ... RB allocation unit, 122 ... CP removal unit, 124 ... FFT processing unit, 126 ... AAS processing unit, 128 ... channel equalization unit, 130 ... demodulation decoding unit

Claims (6)

A multi-carrier wireless communication apparatus that receives a wireless signal using a plurality of antennas,
The wireless communication device performs multi-antenna control using each of a plurality of frequency bands as a unit of control when frequency selective fading is regarded as large, and when the frequency selective fading is regarded as small, A wireless communication apparatus that performs multi-antenna control using the plurality of frequency bands as a unit of control.   The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus calculates an antenna weight for each unit of control.   The wireless communication apparatus according to claim 2, wherein the wireless communication apparatus calculates at least one of an antenna weight for beam forming and an antenna weight for null steering.   The wireless communication apparatus according to claim 2, wherein the wireless communication apparatus applies the antenna weight to a frequency band to be estimated.   The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus determines that the frequency selective fading is large when a difference in received power between known signals distributed in the frequency direction is equal to or greater than a threshold value. A communication control method in a multi-carrier wireless communication apparatus that receives a wireless signal using a plurality of antennas,
When the radio communication device is considered to have a large frequency selective fading, multi-antenna control is performed with each of a plurality of frequency bands as a unit of control, and when the frequency selective fading is considered to be small, A communication control method including a step of performing multi-antenna control using the plurality of frequency bands as a unit of control.

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