JP7582913B2 - Single-carrier MIMO transmitter and single-carrier MIMO receiver - Google Patents

Description

The present invention relates to a single-carrier MIMO (Multiple Input Multiple Output) transmitter and single-carrier MIMO receiver that can be used in wireless transmission systems such as broadcasting and communications, and in particular to improving transmission efficiency in the MIMO SC-FDE (Single Carrier-Frequency Domain Equalization) method that performs channel equalization in the frequency domain.

Conventionally, single-carrier systems using one carrier have been widely used in fixed-transmission wireless transmission systems such as broadcasting and communications. On the other hand, wireless transmission systems in mobile environments generally use multi-carrier OFDM (Orthogonal Frequency Division Multiplexing) systems using multiple carriers, which can track high-speed channel fluctuations by performing channel equalization in the frequency domain on a symbol-by-symbol basis.

Although OFDM is suitable for mobile transmission, compared to single-carrier systems, it generally has a high PAPR (Peak to Average Power Ratio), which is the ratio of the peak power to the average power of the transmission signal, making it vulnerable to nonlinear distortion of the power amplifier and requiring the power amplifier to be used at an operating point in a highly linear region. As a result, it is often operated with a large output back-off from the output level (P1dB) at which the gain drops by 1 dB compared to the ideal linear gain, which results in low power efficiency.

In recent years, among single-carrier methods, the SC-FDE method, which performs channel equalization in the frequency domain (a process to restore amplitude and phase changes that occur in the propagation path), has been proposed (see, for example, Non-Patent Document 1 and Patent Document 1).

The SC-FDE method performs channel estimation and channel equalization in the frequency domain in units of a certain number of consecutive symbols (block units), making it possible to keep up with rapid channel fluctuations in mobile transmission. For this reason, the SC-FDE method is more suitable for mobile transmission than the conventional single-carrier method, which performs channel equalization in the time domain.

In general, in the SC-FDE method, like the OFDM method, by providing a guard interval (GI), it is possible to prevent interference between blocks in a multipath environment. A receiving device that applies the SC-FDE method performs block synchronization to detect the beginning of a block, and extracts a unique word (UW) (a signal with a fixed pattern known to the transmitting device and receiving device) and data, which are pilot signals for channel estimation. The receiving device then converts the UW and data into the frequency domain using a Fourier transform, and performs channel estimation and channel equalization processing. After that, the receiving device converts the data back into a time domain signal using an inverse Fourier transform, and performs processing such as symbol determination.

Since the SC-FDE method generally has a smaller PAPR than the OFDM method, it is possible to reduce the output back-off of the power amplifier, enabling highly efficient operation of the power amplifier and enabling the miniaturization of power amplifiers for mobile transmission.

Furthermore, a MIMO SC-FDE method has been proposed that supports MIMO, which uses multiple antennas to wirelessly transmit large amounts of information at high speeds (see, for example, Patent Document 2). In MIMO, multiple signals are transmitted according to the number of transmissions (multiplexing number), and these signals are received in a mixed state.

Therefore, in the receiving device, MIMO detection (frequency domain MIMO channel estimation and equalization) is required to detect the original transmitted signal from the received signal. In order to distinguish between multiple transmitted signals, the UWs are arranged so that their positional relationships differ across multiple blocks, and the transmitted signals are designed to be orthogonal between the transmission systems.

10 is a diagram showing a symbol block configuration of a null structure in a MIMO SC-FDE method in the prior art, showing a case where the number of transmissions is 2. A transmission signal _x1 indicates a signal transmitted from a first transmission system in a transmitting device, and a transmission signal _x2 indicates a signal transmitted from a second transmission system.

The transmission signals _x1 and _x2 are each formed of two blocks, a MIMO odd block and a MIMO even block. When the number of transmissions is two, MIMO detection is performed in the receiving device for each of these two blocks.

Each block of the transmission signals x ₁ and x ₂ is made up of two consecutive UWs or null data, a GI with the end of the data inserted as a CP (Cyclic Prefix), a MIMO block number, and data.

The UW and null data are pilot signals used for channel estimation. The UW consists of a fixed pattern known between the transmitter and receiver, and uses a CAZAC (Constant Amplitude Zero Auto-Correlation) sequence with excellent periodic autocorrelation properties, such as a Zadoff-Chu sequence with constant amplitude in the time domain and frequency domain. The CP is information that copies the latter part of the data.

The MIMO block number is information for identifying where each of the multiple blocks begins so that the receiving device can perform correct MIMO detection. The MIMO block number identifies the first MIMO odd block and the second MIMO even block before MIMO signal separation is performed.

For the MIMO odd block, a symbol sequence obtained by differentially modulating a value corresponding to 1 is set as the MIMO block number, and for the MIMO even block, a symbol sequence obtained by differentially modulating a value corresponding to 2 is set as the MIMO block number. As the differential modulation, a method capable of delay detection, such as DBPSK (Differential Binary Phase Shift Keying) or DQPSK (Differential Quadrature Phase Shift Keying), is used.

The MIMO block number is generated using the above-mentioned differential modulation method and placed in the symbol sequence to be equalized. This makes it possible to improve the accuracy of identifying the positional relationship of UWs and the transmission efficiency (see, for example, Patent Document 3).

Figure 11 shows the symbol block configuration of the WH structure of the MIMO SC-FDE method in the conventional technology, and shows the case where the number of transmissions is 2, as in Figure 10.

Each block of the transmission signals _x1 and _x2 is composed of two consecutive UWs or -UWs, a GI with the latter part of the data inserted as a CP, a MIMO block number, and data. Comparing this symbol block with the symbol block shown in Figure 10, both symbol blocks are the same in that they contain a GI, a MIMO block number, and data, but the symbol block in Figure 11 differs from the symbol block in Figure 10, which contains two consecutive UWs or -UWs, in that it contains two consecutive UWs or null data.

As shown in FIG. 10, in two consecutive blocks, the UW and null data are set alternately in the two transmission systems. Also, as shown in FIG. 11, in one of the two consecutive blocks, the UW is set in the two transmission systems, and in the other block, the UW is set in one transmission system and -UW is set in the other transmission system.

As a result, the MIMO SC-FDE method can improve the transmission rate more than the SISO (Single Input Single Output) (SISO SC-FDE method) that uses the SC-FDE method of the aforementioned Patent Document 1.

Patent No. 5624527 Patent No. 6612106 JP 2019-140590 A

D. Falconer, et al., “Frequency domain equalization for single-carrier broadband wireless systems”, IEEE Commun. Mag., Vol. 40, pp. 58-66, April 2002.

However, in the MIMO SC-FDE method of Patent Document 2, a CP is added individually to the signal to be equalized, whereas in the SISO SC-FDE method of Patent Document 1, a CP is not added.

As a result, the MIMO SC-FDE system has a lower data ratio (data efficiency) to the transmitted signal compared to the SISO SC-FDE system. There was a demand for improving the transmission efficiency of the MIMO SC-FDE system.

The present invention has been made to solve the above problems, and its purpose is to provide a single-carrier MIMO transmitter and a single-carrier MIMO receiver that can improve transmission efficiency when performing MIMO transmission using the SC-FDE method.

In order to solve the above problem, the single carrier MIMO transmission device of claim 1 is provided with a plurality of transmission antennas, and for each of a plurality of transmission systems corresponding to the plurality of transmission antennas, a MIMO a signal processing unit for processing the signal processing unit for performing a signal processing operation for ... a signal insertion unit, the number of symbols of the MIMO block number being a MIMO block number symbol number a, the number of symbols of the data to be transmitted being a data symbol number b, the number of symbols of the pilot signal being a pilot signal symbol number c, the number of the plurality of transmitting antennas being a MIMO transmission number d, the number of symbols of a MIMO detection range in which equalization is performed in the frequency domain being a MIMO detection range symbol number SS, and the MIMO detection range being expanded from the MIMO block number included in a first block in the detection target block to a detection target block next to the detection target block. The pilot signal insertion unit inserts the pilot signal at a predetermined position and generates a symbol sequence for the detection target block so that the following conditions are satisfied: (A) the number of pilot signal symbols c is a power of 2, (B) the number of MIMO detection range symbols SS is a power of 2 and is expressed by the formula SS = (a + b) x d + c x (2 x d-1), and (C) the two consecutive pilot signals included in the first block in the detection target block are the same.

Furthermore, the single carrier MIMO receiving device of claim 2 is equipped with a single or multiple receiving antennas, and receives modulated waves transmitted from multiple transmitting antennas equipped in the single carrier MIMO transmitting device in a corresponding single or multiple receiving system via the single or multiple receiving antennas, estimates a MIMO channel based on a received pilot signal included in a received signal multiplexed with a block of the MIMO SC-FDE method, and performs equalization in the frequency domain. In this single carrier MIMO receiving device, the block is composed of two consecutive pilot signals, a MIMO block number, and data, the number of symbols of the MIMO block number is the MIMO block number symbol number a, the number of symbols of the data is the data symbol number b, the number of symbols of the pilot signal is the pilot signal symbol number c, and the number of the multiple transmitting antennas is the MIMO transmission number d, the number of symbols in the MIMO detection range in which equalization is performed in the frequency domain is denoted by the MIMO detection range symbol number SS, a detection target block is configured from the blocks in the same number as the MIMO transmission number d, the MIMO detection range is set to a range from the MIMO block number included in the first block in the detection target block to the first pilot signal included in the first block in the detection target block next to the detection target block, the number of pilot signal symbols c is a power of 2 (A), and the number of MIMO detection range symbols SS is a power of 2, Assuming that (B) the number of consecutive pilot signals included in the first block of the detection target blocks is the same as (C), a MIMO channel estimation unit for each reception system performs a Fourier transform on the pilot signal, estimates the MIMO channel, and upsamples the MIMO channel so that it coincides with the number of MIMO detection range symbols SS set in advance, and outputs the MIMO channel after upsampling; and and a Fourier transform unit for each receiving system that performs a Fourier transform on the MIMO detection range corresponding to the number of symbols SS and outputs a frequency domain signal, and a frequency domain MIMO channel equalization unit that inputs the upsampled MIMO channel output by the MIMO channel estimation unit and the frequency domain signal output by the Fourier transform unit, and performs MIMO channel equalization in the frequency domain using the upsampled MIMO channel and the frequency domain signal corresponding to the preset MIMO detection range symbol number SS.

As described above, according to the present invention, it is possible to improve transmission efficiency when performing MIMO transmission using the SC-FDE method.

1 is a block diagram showing a schematic configuration of a single-carrier MIMO transmission device according to an embodiment of the present invention. FIG. 1 is a diagram showing a symbol block configuration of a null structure in a MIMO SC-FDE system according to an embodiment of the present invention. FIG. 2 is a diagram showing a symbol block configuration of a WH structure of a MIMO SC-FDE system in an embodiment of the present invention. 1 is a block diagram showing a schematic configuration of a single-carrier MIMO receiving device according to an embodiment of the present invention. 3 is a block diagram showing a schematic configuration of a reception processing unit. FIG. FIG. 1 is a diagram for explaining an overview of channel estimation in a symbol block configuration with a null structure. FIG. 1 is a diagram for explaining an overview of channel estimation in a symbol block configuration of a WH structure. FIG. 1 is a diagram comparing the symbol block configurations of null structures in the prior art and an embodiment of the present invention. 1 is a diagram comparing the symbol block configurations of the WH structure in the conventional technology and an embodiment of the present invention. FIG. 1 is a diagram showing a symbol block configuration of a null structure in a MIMO SC-FDE method in the prior art. FIG. 1 is a diagram showing a symbol block configuration of a WH structure of a MIMO SC-FDE method in the prior art.

The following describes in detail the embodiments of the present invention with reference to the drawings. The single-carrier MIMO transmitter of the present invention is characterized in that, when performing MIMO allocation on the coded bit sequence of data to be transmitted and configuring blocks so that the arrangement of pilot signals between transmission systems is orthogonal, the blocks are configured so that the pilot signals satisfy the conditions (A) and (C) described below and the MIMO detection range satisfies the condition (B) described below.

The single-carrier MIMO receiving device of the present invention is also characterized in that it estimates the MIMO channel by utilizing the orthogonal relationship of pilot signals contained in the received signal, and performs MIMO detection for a MIMO detection range that satisfies the condition (B) described below.

This allows the UW to be used as a CP in each block of the transmission signal, and eliminates the need to insert the latter part of the data as a CP, improving data efficiency compared to conventional technology. Therefore, transmission efficiency can be improved when performing MIMO transmission using the SC-FDE method.

The following describes an embodiment of the present invention using an example of a MIMO SC-FDE method with two transmissions and two receptions, where the number of transmissions and the number of receptions are each two, but it is possible to increase the number of transmissions and receptions.

[Single-carrier MIMO transmitter]
First, a single-carrier MIMO transmission apparatus according to an embodiment of the present invention will be described below. Fig. 1 is a block diagram showing a schematic configuration of a single-carrier MIMO transmission apparatus according to an embodiment of the present invention.

This transmitting device (single-carrier MIMO transmitting device) 1 is configured as a single-carrier type transmission device that generates a signal that can be MIMO detected in the frequency domain by the receiving device shown in Figure 4 described later, and transmits information wirelessly using multiple antennas (transmitting antennas 20-1, 20-2).

This transmitting device 1 includes a pre-transmission processing unit 10, an inter-system allocation unit 11, internal interleaving units 12-1, 12-2, mapping units 13-1, 13-2, MIMO block number insertion units 14-1, 14-2, pilot signal insertion units 15-1, 15-2, band-limiting filter units 16-1, 16-2, digital quadrature modulation units 17-1, 17-2, DA conversion units 18-1, 18-2, high-frequency transmission units 19-1, 19-2, and transmitting antennas 20-1, 20-2.

The transmission pre-processing unit 10 performs pre-processing such as energy diffusion processing, error correction coding processing, and interleaving processing on the information bit sequence to be transmitted (data to be transmitted), generates a coded bit sequence, and outputs the coded bit sequence to the system allocation unit 11. This pre-processing can be any of energy diffusion processing, error correction coding processing, and interleaving processing.

The inter-system allocation unit 11 inputs the coded bit sequence from the transmission pre-processing unit 10, allocates bits of the coded bit sequence to two transmission systems, and outputs the coded bit sequence after bit allocation to the internal interleaving units 12-1 and 12-2. This bit allocation is performed according to the number of transmissions, and can be allocated in any pattern as long as it corresponds to the reverse allocation on the receiving side.

The following describes the internal interleaving unit 12-1, mapping unit 13-1, MIMO block number insertion unit 14-1, pilot signal insertion unit 15-1, band-limiting filter unit 16-1, digital quadrature modulation unit 17-1, DA conversion unit 18-1, high frequency transmission unit 19-1, and transmission antenna 20-1 of the first transmission system, but the same is true for the internal interleaving unit 12-2, mapping unit 13-2, MIMO block number insertion unit 14-2, pilot signal insertion unit 15-2, band-limiting filter unit 16-2, digital quadrature modulation unit 17-2, DA conversion unit 18-2, high frequency transmission unit 19-2, and transmission antenna 20-2 of the second transmission system.

The inner interleaving unit 12-1 inputs the coded bit sequence after bit allocation from the inter-system allocation unit 11, and performs inner interleaving processes such as bit interleaving and time interleaving on the coded bit sequence after bit allocation. The inner interleaving unit 12-1 then outputs the coded bit sequence after inner interleaving to the mapping unit 13-1.

The mapping unit 13-1 inputs the coded bit sequence after inner interleaving from the inner interleaving unit 12-1, and performs mapping on the coded bit sequence after inner interleaving using a predetermined modulation method such as QPSK, 16QAM, or 16APSK. The mapping unit 13-1 then outputs the mapped bit sequence to the MIMO block number insertion unit 14-1.

The MIMO block number insertion unit 14-1 inputs the mapped bit sequence from the mapping unit 13-1 and inserts the MIMO block number (MIMO block number symbol) into a predetermined position in the mapped bit sequence. The MIMO block number insertion unit 14-1 then outputs the symbol sequence into which the MIMO block number has been inserted to the pilot signal insertion unit 15-1.

Here, the MIMO block number insertion unit 14-1 generates the value identifying the MIMO block number as a MIMO block number symbol through modulation processing in order to place a value for identifying the MIMO block number in the bit sequence after mapping. Specifically, the MIMO block number insertion unit 14-1 modulates the value identifying the MIMO block number by a differential modulation method such as DBPSK or DQPSK to generate a MIMO block number symbol.

As an example, the MIMO block numbers are 0 and 1 when the number of transmissions is 2. Also, when the number of transmissions is 4, the numbers are 00, 01, 10 and 11. Note that the MIMO block number insertion unit 14-1 may perform coding processing on the MIMO block numbers that enables error correction coding or error detection.

The pilot signal inserter 15-1 inputs the symbol sequence into which the MIMO block number has been inserted from the MIMO block number inserter 14-1. The pilot signal inserter 15-1 then inserts a predetermined pilot signal that is orthogonal between the transmission systems into a predetermined position in the symbol sequence into which the MIMO block number has been inserted, so that the symbol sequence becomes, for example, a null structure block configuration as shown in FIG. 2 (described later) or a WH structure block configuration as shown in FIG. 3 (described later).

The pilot signal insertion unit 15-1 generates a symbol sequence with the pilot signal inserted as a symbol sequence for the MIMO SC-FDE block, and outputs this to the band-limiting filter unit 16-1.

Here, the predetermined pilot signal is a pilot signal that is set in advance so as to satisfy the following conditions (A), (B), and (C).
(A) The number of pilot signal symbols (number of pilot signal symbols c) is a power of two.
(B) The number of MIMO detection range symbols (the number of symbols to be equalized) SS for which MIMO channel equalization is performed in the frequency domain is a power of 2 and is expressed by the following equation.
[Equation 1]
SS=(a+b)×d+c×(2×d-1)...(1)
Let a be the number of MIMO block number symbols, b be the number of data symbols, c be the number of pilot signal symbols, and d be the number of MIMO transmissions (the number of transmission antennas, the number of transmission systems).

Here, the MIMO SC-FDE block is composed of two consecutive pilot signal sequences, a MIMO block number symbol sequence, and a data symbol sequence, and the detection target block (α in Figs. 2 and 3 described later) is composed of the same number of MIMO SC-FDE blocks as the number of MIMO transmissions d. In other words, the pilot signal insertion unit 15-1 generates detection target blocks in units of MIMO SC-FDE blocks.

The MIMO detection range is the range from the MIMO block number included in the first block in the detection target block to the first pilot signal included in the first block in the detection target block next to the detection target block. In other words, the MIMO detection range is the MIMO block number symbol sequence, data symbol sequence, pilot signal sequence, pilot signal sequence, MIMO block number symbol sequence, data symbol sequence, ..., MIMO block number symbol sequence, data symbol sequence, and pilot signal sequence.

(C) The two consecutive pilot signals contained in the first block in the detection target block are the same. For example, in Figs. 2(1) and (2) and Figs. 3(1) and (2) described below, the first block contains two consecutive UWs.

By satisfying the above-mentioned condition (A), the pilot signal can be subjected to Fourier transform, and the MIMO channel can be estimated. Also, by satisfying the above-mentioned condition (B), the signal in the MIMO detection range can be subjected to Fourier transform and inverse Fourier transform, and the MIMO channel can be equalized and the data can be decoded.

Furthermore, by satisfying the above-mentioned condition (C), the latter (second) of the two consecutive UWs in the first block also serves as a CP, so there is no need to insert a CP into the block. This improves transmission efficiency and reduces the processing load because there is no need to handle a CP.

Figure 2 shows the symbol block configuration of a null structure in the MIMO SC-FDE system in an embodiment of the present invention, and Figure 3 shows the symbol block configuration of a WH structure in the MIMO SC-FDE system in an embodiment of the present invention.

As shown in Figures 2 and 3, the pilot signal is composed of UW, null data, and -UW, which is the inverse of UW multiplied by a negative number. As explained in Figures 10 and 11, UW is a CAZAC sequence with excellent periodic autocorrelation properties, such as a Zadoff-Chu sequence with constant amplitude in the time domain and frequency domain.

2(1) and 3(1) show the case where the number of transmissions is 2, and Fig. 2(2) and 3(2) show the case where the number of transmissions is 4. For example, transmission signals _x1 , _x2 , _x3 , and _x4 represent signals transmitted from the first, second, third, and fourth transmission systems in the transmitting device 1, respectively.

2(1) and 3(1), the transmission signals _x1 and _x2 are composed of two blocks, the first block being a MIMO odd block and the second block being a MIMO even block. These two blocks are detection target blocks α, and the receiving side performs MIMO detection on this unit.

The first blocks of the transmission signals x ₁ and x ₂ are composed of two consecutive UWs, a MIMO block number, and data (DATA1 _t0 , DATA2 _t0 ).

The second block of the transmission signal _x1 is composed of two consecutive UWs, a MIMO block number, and data (DATA1 _t1 ). Also, in Fig. 2 (1), the second block of the transmission signal _x2 is composed of two consecutive UWs, null data of the same number of symbols as the number of symbols, a MIMO block number, and data (DATA2 _t1 ). In Fig. 3 (1), the second block of the transmission signal _x2 is composed of two consecutive -UWs, a MIMO block number, and data (DATA2 _t1 ).

2(2) and 3(2), the transmission signals _x1 , _x2 , _x3 , and _x4 are composed of four blocks, numbered 1 to 4. These four blocks are detection target blocks α, and the receiving side performs MIMO detection on these blocks.

The first blocks of the transmission signals x ₁ , x ₂ , x ₃ , and x ₄ are composed of two consecutive UWs, a MIMO block number, and data (DATA1 _t0 , DATA2 _t0 , DATA3 _t0 , and DATA4 _t0 ).

In Fig. 2 (2), the second block of the transmission signals x ₁ and x ₃ is composed of two consecutive UWs, a MIMO block number, and data (DATA1 _t1 , DATA3 _t1 ). The second block of the transmission signals x ₂ and x ₄ is composed of null data of the same number of symbols as the two consecutive UWs, a MIMO block number, and data (DATA2 _t1 , DATA4 _t1 ). In Fig. 3 (2), -UW is used instead of null data.

The third block of the transmission signals _x1 and _x2 is composed of two consecutive UWs, a MIMO block number, and data (DATA1 _t2 , DATA2 _t2 ). The third block of the transmission signals _x3 and _x4 is composed of null data of the same number of symbols as the two consecutive UWs, a MIMO block number, and data (DATA3 _t2 , DATA4 _t2 ). In FIG. 3(2), -UW is used instead of null data.

The fourth block of the transmission signals _x1 and _x4 is composed of two consecutive UWs, a MIMO block number, and data (DATA1 _t3 , DATA4 _t3 ). The fourth block of the transmission signals _x2 and _x3 is composed of null data of the same number of symbols as the two consecutive UWs, a MIMO block number, and data (DATA2 _t3 , DATA3 _t3 ). In FIG. 3(2), -UW is used instead of null data.

For each transmission system, the latter (second) of two consecutive UWs in the first block included in the first detection target block is the same as the first (first) of two consecutive UWs in the first block included in the second detection target block, and also serves as a CP in the MIMO detection range. In other words, for each transmission system, the first block includes two consecutive UWs, and the latter of the two consecutive UWs can be said to be a GI with the latter part of the MIMO detection range inserted as a CP.

This eliminates the need to insert a CP behind the MIMO detection range in each transmission system, improving transmission efficiency and reducing processing load.

In Figures 2 (1) and 3 (1), based on the conditions (A), (B), and (C) above, if the number of MIMO transmissions d = 2, the number of MIMO block number symbols a = 2, and the number of pilot signal symbols c = ² = 256, then the number of data symbols b = 1662, and the MIMO detection range is ² = 4096.

Also, in Figures 2 (2) and 3 (2), based on the conditions (A) and (B) above, if the number of MIMO transmissions d = 4, the number of MIMO block number symbols a = 2, and the number of pilot signal symbols c = ² = 256, then the number of data symbols b = 1598, and the MIMO detection range is ² = 8192.

The number of pilot signal symbols c is actually the number of symbols equivalent to the GI length in the OFDM system, which is set according to the maximum delay time for the delayed wave to arrive. The symbol length of the pilot signal is calculated from the number of symbols and the symbol rate, and is set so as not to exceed the maximum delay time.

Returning to FIG. 1, the band-limiting filter unit 16-1 inputs the symbol sequence of the MIMO SC-FDE block from the pilot signal insertion unit 15-1. The band-limiting filter unit 16-1 then performs 2x upsampling on the symbol sequence of the MIMO SC-FDE block and performs waveform shaping by band-limiting filter processing. The band-limiting filter unit 16-1 outputs the symbol sequence of the MIMO SC-FDE block after waveform shaping to the digital orthogonal modulation unit 17-1. A root roll-off filter is generally used as the band-limiting filter.

The digital orthogonal modulation unit 17-1 inputs the symbol sequence of the MIMO SC-FDE block after waveform shaping from the band-limiting filter unit 16-1. The digital orthogonal modulation unit 17-1 then performs digital orthogonal modulation processing on the symbol sequence of the MIMO SC-FDE block after waveform shaping.

The digital quadrature modulation unit 17-1 also performs aperture correction to correct the aperture effect caused by the digital-to-analog conversion in the DA conversion unit 18-1. The digital quadrature modulation unit 17-1 outputs the signal after quadrature modulation to the DA conversion unit 18-1.

The DA conversion unit 18-1 inputs the quadrature modulated signal from the digital quadrature modulation unit 17-1, converts the quadrature modulated digital signal into an analog signal, and outputs the analog signal to the transmission radio frequency unit 19-1.

The transmitting high frequency unit 19-1 receives an analog signal from the DA conversion unit 18-1, converts the frequency of the analog signal to a radio frequency, amplifies it to a specified power level using a power amplifier, and transmits the modulated wave from the transmitting antenna 20-1.

As described above, according to the transmitting device 1 of the embodiment of the present invention, the pilot signal inserting unit 15-1 inserts a preset pilot signal that satisfies the above-mentioned conditions (A), (B), and (C) into the symbol sequence so as to obtain the block configuration shown in, for example, FIG. 2 or FIG. 3, and generates a MIMO SC-FDE block.

Then, a modulated wave including a pilot signal that satisfies the above-mentioned conditions (A), (B), and (C) is transmitted from the transmitting device 1.

Figure 8 is a diagram comparing the symbol block configurations of a null structure in the conventional technology and an embodiment of the present invention, and Figure 9 is a diagram comparing the symbol block configurations of a WH structure in the conventional technology and an embodiment of the present invention. Figure 8 (1) shows the same symbol block configuration as the conventional technology shown in Figure 10, and Figure 9 (1) shows the same symbol block configuration as the conventional technology shown in Figure 11. Figures 8 (2) and 9 (2) show the symbol block configurations of an embodiment of the present invention.

From Figures 8 (1) and (2) and Figures 9 (1) and (2), it can be seen that in the conventional technology, a CP is inserted into the MIMO SC-FDE block, whereas in the embodiment of the present invention, the UW also serves as a CP, and a CP is not inserted into the MIMO SC-FDE block.

In this way, in an embodiment of the present invention, the latter (second) of two consecutive UWs in the first block also serves as a CP, so there is no need to insert a CP as in conventional technology into the MIMO SC-FDE block.

In other words, in each transmission system, there is no need to insert the part behind the MIMO detection range as a CP, which improves transmission efficiency and reduces the processing load.

As a result, when MIMO transmission is performed using the SC-FDE method, the proportion of valid data increases relative to the total transmitted signal, making it possible to achieve a higher transmission rate than conventional technology when compared at the same symbol rate, thereby improving transmission efficiency.

[Single-carrier MIMO receiver]
Next, a single carrier MIMO receiving apparatus according to an embodiment of the present invention will be described below. Fig. 4 is a block diagram showing a schematic configuration of a single carrier MIMO receiving apparatus according to an embodiment of the present invention.

This receiving device (single-carrier MIMO receiving device) 2 receives modulated waves transmitted from the multiple transmitting antennas 20-1, 20-2 of the transmitting device 1 shown in Figure 1 using multiple antennas (receiving antennas 30-1, 30-2) and performs MIMO detection (MIMO channel estimation and equalization in the frequency domain).

The receiving device 2 includes receiving antennas 30-1, 30-2, receiving processing units 40-1, 40-2, MIMO block number detection units 41-1, 41-2, MIMO block number comparison units 42-1, 42-2, noise power detection units 43-1, 43-2, MIMO channel estimation units 44-1, 44-2, Fourier transform units 45-1, 45-2, frequency domain MIMO channel equalization unit 46, inverse Fourier transform units 47-1, 47-2, symbol decision/likelihood calculation units 48-1, 48-2, post-equalization MIMO block number decoding units 49-1, 49-2, post-equalization MIMO block number decision unit 50, internal deinterleaving units 51-1, 51-2, and a decoding unit 52.

The following describes the receiving antenna 30-1 of the first receiving system, the receiving processing unit 40-1, the MIMO block number detection unit 41-1, the MIMO block number comparison unit 42-1, the noise power detection unit 43-1, the MIMO channel estimation unit 44-1, the Fourier transform unit 45-1, the inverse Fourier transform unit 47-1, the symbol decision/likelihood calculation unit 48-1, the equalized MIMO block number decoding unit 49-1, and the internal deinterleaving unit 51-1. The same is true for the receiving antenna 30-2 of the second receiving system, the receiving processing unit 40-2, the MIMO block number detection unit 41-2, the MIMO block number comparison unit 42-2, the noise power detection unit 43-2, the MIMO channel estimation unit 44-2, the Fourier transform unit 45-2, the inverse Fourier transform unit 47-2, the symbol decision/likelihood calculation unit 48-2, the post-equalization MIMO block number decoding unit 49-2, and the inner deinterleaving unit 51-2.

Figure 5 is a block diagram showing the schematic configuration of the reception processing unit 40-1. This reception processing unit 40-1 includes a reception high frequency unit 60, an AD conversion unit 61, a digital quadrature demodulation unit 62, a band-limiting filter unit 63, and a block synchronization unit 64. The configuration of the reception processing unit 40-2 is also similar to that shown in Figure 5.

The high-frequency receiving unit 60 amplifies the radio-frequency signal received via the receiving antenna 30-1 to the desired power using a low-phase noise amplifier, and then converts the radio frequency to an intermediate frequency. The high-frequency receiving unit 60 then outputs the intermediate-frequency signal to the AD conversion unit 61.

The AD conversion unit 61 inputs an intermediate frequency signal from the high frequency receiving unit 60, converts the intermediate frequency analog signal into a digital signal, and outputs the digital signal to the digital orthogonal demodulation unit 62.

The digital orthogonal demodulation unit 62 receives the digital signal from the AD conversion unit 61, performs automatic frequency control on the digital signal, and generates an orthogonally demodulated complex baseband signal while correcting the frequency shift. The digital orthogonal demodulation unit 62 then outputs the frequency-corrected complex baseband signal to the band-limiting filter unit 63.

The band-limiting filter unit 63 inputs the frequency-corrected complex baseband signal from the digital orthogonal demodulation unit 62, and performs band-limiting by filter processing on the frequency-corrected complex baseband signal. The band-limiting filter unit 63 then outputs the band-limited complex baseband signal to the block synchronization unit 64. A root roll-off filter is generally used as the band-limiting filter.

The block synchronization unit 64 inputs the band-limited complex baseband signal from the band-limiting filter unit 63, and detects the synchronization timing of the MIMO SC-FDE block for the band-limited complex baseband signal using the IQ signal of the UW portion as a reference. The block synchronization unit 64 then outputs the MIMO SC-FDE block for which synchronization timing has been detected to the MIMO block number detection unit 41-1.

Returning to FIG. 4, the MIMO block number detection unit 41-1 inputs the MIMO SC-FDE block for which synchronization timing has been detected by the block synchronization unit 64 of the reception processing unit 40-1. The MIMO block number detection unit 41-1 then detects the MIMO block number by performing differential demodulation using delay detection on the MIMO SC-FDE block based on the position of the synchronization timing (synchronization position) detected by the block synchronization unit 64.

The MIMO block number detection unit 41-1 outputs the MIMO block number to the MIMO block number comparison unit 42-1 and the MIMO channel estimation unit 44-1. The MIMO block number detection unit 41-1 also outputs the MIMO SC-FDE block to the noise power detection unit 43-1, the MIMO channel estimation unit 44-1, and the Fourier transform unit 45-1.

The MIMO block number comparison unit 42-1 inputs the MIMO block number from the MIMO block number detection unit 41-1, and also inputs the equalized MIMO block number from the equalized MIMO block number determination unit 50 described below. The MIMO block number comparison unit 42-1 then compares the MIMO block number with the equalized MIMO block number.

When the MIMO block number comparison unit 42-1 determines that the MIMO block number and the equalized MIMO block number match based on the comparison result, it outputs the comparison result indicating the match and the MIMO block number to the MIMO channel estimation unit 44-1. On the other hand, when the MIMO block number comparison unit 42-1 determines that the MIMO block number and the equalized MIMO block number are different, it outputs the comparison result indicating the difference and the equalized MIMO block number to the MIMO channel estimation unit 44-1.

As a result, when the MIMO block number and the equalized MIMO block number are different, the MIMO channel estimation unit 44-1 is controlled so that MIMO detection is performed in the frequency domain MIMO channel equalization unit 46 described later based on the equalized MIMO block number input from the equalized MIMO block number determination unit 50.

The noise power detection unit 43-1 receives the MIMO SC-FDE block from the MIMO block number detection unit 41-1, measures the noise power n ₁ of the received signal using the MIMO SC-FDE block, and outputs the noise power n ₁ to the frequency domain MIMO channel equalization unit .

The MIMO channel estimation unit 44-1 inputs the MIMO SC-FDE block and the MIMO block number from the MIMO block number detection unit 41-1, and also inputs the comparison result and the MIMO block number or the equalized MIMO block number from the MIMO block number comparison unit 42-1.

The MIMO channel estimation unit 44-1 extracts the time domain pilot signals contained in a series of MIMO SC-FDE blocks according to the MIMO block number or equalized MIMO block number according to the comparison result, based on the position of the synchronization timing detected by the block synchronization unit 64, and performs a Fourier transform to estimate the MIMO channel.

After estimating the MIMO channel, the MIMO channel estimation unit 44-1 upsamples the MIMO channel so that the number of symbols (preset number of MIMO detection range symbols SS) for frequency domain equalization is performed in the downstream frequency domain MIMO channel equalization unit 46. Then, the MIMO channel estimation unit 44-1 outputs the upsampled MIMO channel (for example, when the number of transmissions is 2, channel responses h ₁₁ , h ₁₂ ) to the frequency domain MIMO channel equalization unit 46. The upsampled MIMO channel becomes a MIMO channel corresponding to the number of symbols (preset number of MIMO detection range symbols SS) for frequency domain equalization.

Here, the number of symbols for which frequency domain equalization is performed is the number of MIMO detection range symbols SS in the above formula (1) under the condition (B) above. For example, when the number of transmissions is 2, the number of MIMO block number symbols a=2 and the number of pilot signal symbols c= ² =256, then the number of MIMO detection range symbols SS= ² =4096.

For example, when the number of transmissions is two as shown in Figures 2 (1) and 3 (1), the MIMO channel estimation unit 44-1 performs a Fourier transform on two time-domain pilot signals (pilot signal of the first block and pilot signal of the second block) in the received signal _y1 of the first receiving system (signal of the receiving system of the receiving antenna 30-1) to estimate channel responses _h11 , _h12 .

The MIMO channel H when the number of transmissions is 2 is expressed by the following equation.
[Equation 2]

Fig. 6 is a diagram for explaining an overview of channel estimation in a symbol block configuration with a null structure, and corresponds to Fig. 2(1). As described above, the received signal _y1 is a signal of the receiving system of the receiving antenna 30-1, and the received signal _y2 is a signal of the receiving system of the receiving antenna 30-2. The same applies to Fig. 7 described later.

The MIMO channel estimation unit 44-1 extracts a received pilot signal h ₁₁ UW _t +h ₁₂ UW _t of the first block and a received pilot signal h ₁₁ UW _t of the second block from the received signal y ₁ , based on a position shifted by an FFT window offset, where UW _t indicates a pilot signal in the time domain.

The MIMO channel estimation unit 44-1 then Fourier transforms the extracted received pilot signal h ₁₁ UW _t +h ₁₂ UW _t , and also Fourier transforms the received pilot signal h ₁₁ UW _t . The MIMO channel estimation unit 44-1 subtracts the latter result from the former result, and divides the result by the Fourier transform result UW _f of the pilot signal UW _t to estimate the channel response h _12. The MIMO channel estimation unit 44-1 also divides the latter result by the Fourier transform result UW _f of the pilot signal UW _t to estimate the channel response h ₁₁ .

Similarly, the MIMO channel estimation unit 44-2 extracts received pilot signal h ₂₁ UW _t +h ₂₂ UW _t of the first block and received pilot signal h 21 UW _t of the second block from received signal _{y 2} , based on a position shifted by the FFT window offset.

The MIMO channel estimation unit 44-2 then Fourier transforms _the extracted received pilot _{signal h21UWt} + _h22UWt and also Fourier transforms the received pilot signal _h21UWt . The MIMO channel estimation unit 44-2 subtracts the latter result from the former result and divides the result by the Fourier transform _{result UWf} of the pilot signal _UWt to estimate the channel response _h22 . The MIMO channel estimation unit 44-2 also divides the latter result _by the Fourier transform result _UWf of the pilot signal UWt to estimate the channel response _h21 .

Figure 7 is a diagram explaining an overview of channel estimation in a symbol block configuration of a WH structure, and corresponds to Figure 3 (1).

The MIMO channel estimation unit 44-1 extracts the received pilot signal h ₁₁ UW _t +h ₁₂ UW _t of the first block and the received pilot signal h ₁₁ UW _t -h ₁₂ UW _t of the second block from the received signal y ₁ , based on a position shifted by the FFT window offset.

The MIMO channel estimation unit 44-1 then performs a Fourier transform on _the extracted received pilot _{signal h11UWt} + _h12UWt , and _also performs a Fourier transform on the received pilot signal _h11UWt - _h12UWt . The MIMO channel estimation unit 44-1 adds the former result to the latter result, and divides the result by twice the Fourier transform result _UWf of the pilot signal _UWt , to estimate the channel response _h11 . The MIMO channel estimation unit 44-1 also subtracts the latter result of the Fourier transform from the former result, and divides the result by twice _{the Fourier transform result UWf of} the pilot signal _UWt , to estimate the channel response _h12 .

Similarly, the MIMO channel estimation unit 44-2 extracts the received pilot signal h ₂₁ UW _t +h ₂₂ UW _t of the first block and the received pilot signal h ₂₁ UW _t -h ₂₂ UW _t of the second block from the received signal y ₂ , based on a position shifted by the FFT window offset.

The MIMO channel estimation unit 44-2 performs a Fourier transform on _the extracted received pilot _{signal h21UWt} + _h22UWt , and _also performs a Fourier transform on the received pilot signal _h21UWt - _h22UWt . The MIMO channel estimation unit 44-2 adds the former result to the latter result, and divides the result by twice the Fourier transform result _UWf of the pilot signal _{UWt ,} to estimate the channel response _h21 . The MIMO channel estimation unit 44-2 also subtracts the latter result of the Fourier transform from the former result, and divides the result by twice the Fourier transform result _UWf of the pilot signal _UWt , to estimate the channel response _h22 .

In addition, the MIMO channel estimation units 44-1 and 44-2 perform addition and subtraction processing after performing a Fourier transform, but may perform a Fourier transform after performing addition and subtraction processing.

Returning to FIG. 4, the Fourier transform unit 45-1 inputs the MIMO SC-FDE block from the MIMO block number detection unit 41-1. The Fourier transform unit 45-1 then extracts the time domain MIMO block number symbol sequence, data symbol sequence, pilot signal sequence, pilot signal sequence, MIMO block number symbol sequence, data symbol sequence, ..., MIMO block number symbol sequence, data symbol sequence, and pilot signal sequence, which correspond to the number of symbols (preset MIMO detection range symbol number SS) to be frequency domain equalized in the subsequent frequency domain MIMO channel equalization unit 46, contained in the series of MIMO SC-FDE blocks, and performs a Fourier transform on these symbol sequences into the frequency domain.

The Fourier transform unit 45-1 outputs a frequency domain signal (for example, when the number of transmissions is 2, the frequency domain signal r ₁ (f)) to the frequency domain MIMO channel equalization unit .

Here, the number of symbols to be subjected to frequency domain equalization is the number of MIMO detection range symbols SS in the above formula (1) under the above condition (B).

For example, when the number of transmissions shown in Figures 2 (1) and 3 (1) is 2, the Fourier transform unit 45-1 performs a Fourier transform into the frequency domain in the received signal _y1 of the first reception system, using as units the MIMO block number symbol sequence, data symbol sequence, pilot signal sequence, pilot signal sequence, MIMO block number symbol sequence, data symbol sequence, and pilot signal sequence in the time domain corresponding to the MIMO detection range symbol number SS = 4096, which is the number of symbols for which frequency domain equalization is performed.

Here, for example, when the number of transmissions is 2, the noise power detector 43-2 outputs noise power n ₂ to the frequency domain MIMO channel equalizer 46, the MIMO channel estimator 44-2 outputs channel responses h ₂₁ and h ₂₂ , and the Fourier transformer 45-2 outputs frequency domain signal r ₂ (f).

For example, when the number of transmissions is 2, the frequency domain MIMO channel equalization unit 46 inputs the noise power n ₁ from the noise power detection unit 43-1, the channel responses h ₁₁ and h ₁₂ from the MIMO channel estimation unit 44-1, and the frequency domain signal r ₁ (f) from the Fourier transform unit 45-1. The frequency domain MIMO channel equalization unit 46 also inputs the noise power n ₂ from the noise power detection unit 43-2, the channel responses h ₂₁ and h ₂₂ from the MIMO channel estimation unit 44-2, and the frequency domain signal r ₂ (f) from the Fourier transform unit 45-2.

The frequency domain MIMO channel equalization unit 46 equalizes (separates) the transmission signals x1 and x2 mixed into the frequency domain signals _r1 (f) and _r2 (f) based on the noise _{powers n1} and _n2 , the channel responses _h11 , _h12 , _h21 , and _h22 , and the frequency domain signals _r1 (f) and _r2 (f), using a _zero forcing (ZF) criterion, a minimum mean square error (MMSE) criterion, or the like.

That is, the frequency domain MIMO channel equalization unit 46 equalizes the mixed transmission signals x1 and x2 using the MIMO channel H corresponding to the number of symbols for frequency domain equalization (a preset number of MIMO detection range symbols SS), and the MIMO block number symbol sequence, data symbol sequence, pilot signal sequence, pilot signal sequence, MIMO block number symbol sequence, data symbol sequence, ..., MIMO block number symbol sequence, data symbol sequence and pilot signal sequence (and noise power) in the frequency domain corresponding to the number of symbols for frequency domain equalization (a preset number of MIMO detection range symbols _{SS )} .

The frequency domain MIMO channel equalization unit 46 outputs the equalized frequency domain signal x ₁ ^(f) corresponding to the transmission signal x ₁ to the inverse Fourier transform unit 47-1, and outputs the equalized frequency domain signal x ₂ ^(f) corresponding to the transmission signal x ₂ to the inverse Fourier transform unit 47-2.

For example, when the zero-forcing criterion is used, the frequency domain MIMO channel equalization unit 46 performs MIMO channel equalization based on the MIMO channel H (channel responses _h11 , _h12 , _h21 , _h22 ) and the frequency domain signal r(f) ( _r1 (f), _r2 (f)) using the following formula, and obtains the equalized frequency domain signal x^(f) ( _x1 ^(f), _x2 ^(f)).
[Equation 3]

Furthermore, when the minimum mean square error criterion is used, the frequency domain MIMO channel equalization unit 46 performs MIMO channel equalization using the following formula based on the noise power ^σ2 , the MIMO channel H (channel responses _h11 , _h12 , _h21 , _h22 ) and the frequency domain signal r(f) ( _r1 (f), _r2 (f)), and obtains the equalized frequency domain signal x^(f) ( _x1 ^(f), _x2 ^(f)). The noise power ^σ2 is calculated based on the noise powers _n1 and _n2 .
[Equation 4]

Here, the frequency domain signal r(f) is expressed by the following equation.
[Equation 5]

送信数をＮ_t、受信数をＮ_r、Ｎ_r次単位行列をＩ_Nrとする。 Moreover, the equalized frequency domain signal x^(f) is expressed by the following equation.
[Equation 6]

The number of transmissions is N _t , the number of receptions is N _r , and the _Nr -th order unit matrix is I _Nr .

The inverse Fourier transform unit 47-1 inputs the equalized frequency domain signal x ₁ ^(f) corresponding to the transmission signal x ₁ from the frequency domain MIMO channel equalization unit 46, transforms the equalized frequency domain signal x ₁ ^(f) into the time domain, and outputs the time domain signal corresponding to the transmission signal x ₁ to the symbol decision/likelihood calculation unit 48-1.

The equalized frequency domain signal corresponding to the transmission signal _x1 is a MIMO block number symbol sequence, a data symbol sequence, a pilot signal sequence, a pilot signal sequence, a MIMO block number symbol sequence, a data symbol sequence, ..., a MIMO block number symbol sequence, a data symbol sequence, and a pilot signal sequence in the frequency domain corresponding to the number of symbols (the predetermined MIMO detection range symbol number SS) on which frequency domain equalization has been performed.

Moreover, the time domain signal corresponding to the transmission signal _x1 is a time domain MIMO block number symbol sequence, a data symbol sequence, a pilot signal sequence, a pilot signal sequence, a MIMO block number symbol sequence, a data symbol sequence, ..., a MIMO block number symbol sequence, a data symbol sequence, and a pilot signal sequence corresponding to the number of symbols subjected to frequency domain equalization (a preset MIMO detection range symbol number SS).

The symbol decision/likelihood calculation unit 48-1 inputs the time domain signal corresponding to the transmission signal _x1 from the inverse Fourier transform unit 47-1, extracts the MIMO block number symbol sequence and the data symbol sequence from the time domain signal, and performs demapping and likelihood calculation on these sequences.

The symbol decision/likelihood calculation unit 48-1 outputs a metric sequence of the transmission signal x ₁ corresponding to the MIMO block number symbol sequence to the equalized MIMO block number decoding unit 49-1. Also, the symbol decision/likelihood calculation unit 48-1 outputs a metric sequence of the transmission signal x ₁ corresponding to the information bit sequence (data that has been subjected to error correction coding) that constitutes the data symbol sequence to the inner deinterleaving unit 51-1. The metric sequence can be a bit sequence after hard decision, a likelihood, a quantized likelihood, etc.

The equalized MIMO block number decoding unit 49-1 receives the metric sequence of the transmission signal _x1 corresponding to the MIMO block number symbol sequence from the symbol decision/likelihood calculation unit 48-1, extracts a value corresponding to the MIMO block number from the metric sequence, and outputs this to a equalized MIMO block number decision unit 50 as the equalized MIMO block number corresponding to the transmission signal _x1 .

The equalization MIMO block number determination unit 50 inputs the equalization MIMO block number corresponding to the transmission signal x ₁ from the equalization MIMO block number decoding unit 49-1, and also inputs the equalization MIMO block number corresponding to the transmission signal x ₂ from the equalization MIMO block number decoding unit 49-2.

The equalized MIMO block number determination unit 50 compares these equalized MIMO block numbers, and if these equalized MIMO block numbers match, outputs the equalized MIMO block numbers to the MIMO block number comparison units 42-1 and 42-2. On the other hand, if these equalized MIMO block numbers do not match, the equalized MIMO block number determination unit 50 moves the synchronization position of the block numbers forward or backward, and then causes the MIMO block number detection units 41-1, 41-2, etc. to redo the processing following MIMO block number detection.

Here, it is assumed that the MIMO block number input from the MIMO block number detection units 41-1 and 41-2 in the MIMO block number comparison units 42-1 and 42-2 does not match the equalized MIMO block number input from the equalized MIMO block number determination unit 50. The MIMO channel estimated by the MIMO channel estimation units 44-1 and 44-2 in this case will be described below.

If the MIMO block number and the equalized MIMO block number do not match, the elements of the MIMO channel H estimated by the MIMO channel estimation units 44-1 and 44-2 will be swapped or inverted.

In the case of the null structure shown in FIG. 6, the estimation accuracy of the channel response h ₁₁ is deteriorated, the positive and negative of the value of the channel response h ₁₂ is reversed, and the estimation accuracy of the channel response h ₂₁ is deteriorated, and the positive and negative of the value of the channel response h ₂₂ is reversed. Therefore, when the MIMO block number and the equalized MIMO block number do not match, the MIMO channel estimation units 44-1 and 44-2 respectively multiply the values of the channel response h ₁₂ and the channel response h ₂₂ by a negative number, thereby reversing the positive and negative of the values of the channel response h ₁₂ and the channel response h _22. Furthermore, by reversing the subtraction direction from backward to forward, the values of the channel responses h ₁₁ and h ₂₁ are output. This makes it possible to estimate the MIMO channel normally.

In the case of the WH structure shown in Fig. 7, the positive and negative values of the channel responses _h12 and _h22 are reversed. Therefore, when the MIMO block number and the equalized MIMO block number do not match, the MIMO channel estimation units 44-1 and 44-2 estimate the channel responses _h12 and _{h22 by using a UW multiplied by a negative number as the UW to be divided when estimating the channel responses h12 and h22 ,} respectively, or by multiplying the obtained channel responses h12 and _h22 by a negative number, thereby reversing the positive and negative values of the channel responses _h12 and _h22 . This makes it possible to estimate a normal MIMO channel.

In addition, the MIMO block number detection units 41-1 and 41-2 may suspend and restart the detection process for one block so as to detect a normal MIMO block number.

The inner deinterleaving unit 51-1 receives the metric sequence of the transmission signal x ₁ corresponding to the information bit sequence constituting the data symbol sequence from the symbol decision/likelihood calculation unit 48-1, performs the inverse process of the inner interleaving unit 12-1 shown in FIG. 1 on the metric sequence, and outputs the metric sequence of the transmission signal x ₁ after inner deinterleaving to the decoding unit 52.

The decoder 52 receives the metric sequence of the transmission signal _x1 after the inner deinterleaving from the inner deinterleaving unit 51-1, and receives the metric sequence of the transmission signal _x2 after the inner deinterleaving from the inner deinterleaving unit 51-2. The decoder 52 then performs a process of returning these metric sequences to one sequence in a manner corresponding to the inter-system allocation unit 11 shown in Fig. 1. The decoder 52 then performs a deinterleaving process, an error correction decoding process, an energy despreading process, and the like corresponding to the transmission pre-processing unit 10 shown in Fig. 1, decodes the metric sequence after these processes, and outputs the original information bit sequence.

As described above, the receiving device 2 according to an embodiment of the present invention receives the modulated wave transmitted from the transmitting device 1 shown in FIG. 1. After estimating the MIMO channel, the MIMO channel estimation units 44-1 and 44-2 upsample the MIMO channel so that it matches the number of symbols for frequency domain equalization (the number of symbols SS in the MIMO detection range that is preset under the condition (B) above).

The Fourier transform units 45-1 and 45-2 Fourier transform the time domain MIMO block number symbol sequence, data symbol sequence, etc., corresponding to the number of symbols to be frequency domain equalized (the number of MIMO detection range symbols SS set in advance under the condition (B) above) into the frequency domain.

The frequency domain MIMO channel equalization unit 46 equalizes the mixed transmission signals x1, x2 using the MIMO channel H and the frequency domain MIMO block number symbol sequence, data symbol sequence, etc. (and noise power) corresponding to the number of symbols to be subjected to frequency domain equalization (the predetermined number of MIMO detection range symbols SS under the above-mentioned condition ( _{B )} ).

The inverse Fourier transform units 47-1 and 47-2 perform an inverse Fourier transform on signals such as the MIMO block number symbol sequence and data symbol sequence in the frequency domain corresponding to the number of symbols that have been frequency domain equalized (the preset number of MIMO detection range symbols SS) into the time domain.

Here, because the number of pilot signal symbols c is a power of 2, the pilot signal can be Fourier transformed. Also, because the number of MIMO detection range symbols SS is a power of 2, the MIMO detection range can be Fourier transformed and inverse Fourier transformed.

Furthermore, even if the MIMO detection range shifts forward or there is a delayed wave, as shown in Figures 8(2) and 9(2), the latter (second) of two consecutive UWs in the first block also serves as a CP, so there is no effect from these factors. In other words, the MIMO channel can be estimated with high accuracy, and the MIMO channel equalization can be performed with high accuracy.

As a result, when MIMO transmission is performed using the SC-FDE method, the proportion of valid data increases relative to the total transmitted signal, making it possible to achieve a higher transmission rate than conventional technology when compared at the same symbol rate, thereby improving transmission efficiency.

The present invention has been described above using embodiments, but the present invention is not limited to the above embodiments and can be modified in various ways without departing from the technical concept thereof.

For example, in the above embodiment, the number of transmissions is described as 2 and 4, but the number of transmissions may be a number other than 2 or 4. Also, in the above embodiment, the number of receptions is described as 2, but the number of receptions may be a single number or a number other than 2.

In addition, in the above embodiment, examples of symbol block configurations of null structure and WH structure are described, but the symbol block configuration may be other than the null structure and WH structure.

In addition, in Fig. 2(1), the pilot signal of null data is inserted into the transmission signal _x2 , but it may be inserted into the transmission signal _x1 . The same applies to the pilot signal of -UW shown in Fig. 3(1). The pilot signals of null data and -UW shown in Fig. 2(2) and Fig. 3(2) may also be inserted into the transmission signal _x1 as long as the pilot signals are orthogonal between the transmission systems.

The transmitting device 1 and receiving device 2 of the embodiment of the present invention are useful for wireless transmission systems such as broadcasting or communication that perform MIMO transmission using the SC-FDE method.

1. Transmitter (single-carrier MIMO transmitter)
2. Receiver (single-carrier MIMO receiver)
10 Transmission pre-processing unit 11 System allocation unit 12 Internal interleaving unit 13 Mapping unit 14 MIMO block number insertion unit 15 Pilot signal insertion unit 16, 63 Band-limiting filter unit 17 Digital orthogonal modulation unit 18 DA conversion unit 19 Transmission high frequency unit 20 Transmission antenna 30 Reception antenna 40 Reception processing unit 41 MIMO block number detection unit 42 MIMO block number comparison unit 43 Noise power detection unit 44 MIMO channel estimation unit 45 Fourier transform unit 46 Frequency domain MIMO channel equalization unit 47 Inverse Fourier transform unit 48 Symbol decision/likelihood calculation unit 49 Equalized MIMO block number decoding unit 50 Equalized MIMO block number decision unit 51 Internal deinterleaving unit 52 Decoding unit 60 Reception high frequency unit 61 AD conversion unit 62 Digital orthogonal demodulation unit 64 Block synchronization unit a MIMO block number, number of symbols b, number of data symbols c, number of pilot signal symbols d, number of MIMO transmissions SS, number of MIMO detection range symbols

Claims (2)

A single carrier MIMO transmission device is provided with a plurality of transmitting antennas, generates a MIMO SC-FDE block for each of a plurality of transmission systems corresponding to the plurality of transmitting antennas, and transmits a modulated wave of the block for each transmission system via the transmitting antennas,
an inter-system allocation unit that allocates an encoded bit sequence of data to be transmitted to the plurality of transmission systems;
a mapping unit for each transmission system that performs mapping on the coded bit sequence of the data to be transmitted, which has been allocated by the system allocation unit, using a predetermined modulation method, and outputs the mapped bit sequence;
a MIMO block number insertion unit for each transmission system that inserts a MIMO block number into a predetermined position of the mapped bit sequence output by the mapping unit, and outputs a symbol sequence into which the MIMO block number is inserted;
a pilot signal insertion unit for each transmission system that inserts two consecutive pilot signals having an orthogonal relationship between transmission systems into a predetermined position in the symbol sequence into which the MIMO block number is inserted output by the MIMO block number insertion unit, and generates a symbol sequence of a detection target block consisting of the same number of blocks as the number of transmission systems, with the block consisting of the two consecutive pilot signals, the MIMO block number, and the data to be transmitted as a unit,
The number of symbols of the MIMO block number is defined as a MIMO block number symbol number a, the number of symbols of the data to be transmitted is defined as a data symbol number b, the number of symbols of the pilot signal is defined as a pilot signal symbol number c, the number of the multiple transmitting antennas is defined as a MIMO transmission number d, and the number of symbols of the MIMO detection range in which equalization is performed in the frequency domain is defined as a MIMO detection range symbol number SS,
The MIMO detection range is set to a range from the MIMO block number included in a first block in the detection target block to a first pilot signal included in a first block in the detection target block next to the detection target block,
The pilot signal insertion unit
a pilot signal inserted at a predetermined position so as to satisfy the following conditions: (A) the number of pilot signal symbols c is a power of 2; (B) the number of MIMO detection range symbols SS is a power of 2 and is expressed by the formula: SS = (a + b) x d + c x (2 x d - 1); and (C) the two consecutive pilot signals included in a first block in the detection target block are the same, thereby generating a symbol sequence for the detection target block. A single carrier MIMO receiving device is provided with one or more receiving antennas, and receives modulated waves transmitted from a plurality of transmitting antennas provided in the single carrier MIMO transmitting device at a corresponding one or more receiving systems via the single or more receiving antennas, estimates a MIMO channel based on a received pilot signal included in a received signal multiplexed with a block of a MIMO SC-FDE system, and performs equalization in the frequency domain,
The block is composed of two consecutive pilot signals, a MIMO block number, and data;
The number of symbols of the MIMO block number is defined as a MIMO block number symbol number a, the number of symbols of the data is defined as a data symbol number b, the number of symbols of the pilot signal is defined as a pilot signal symbol number c, the number of the multiple transmitting antennas is defined as a MIMO transmission number d, and the number of symbols of the MIMO detection range in which equalization is performed in the frequency domain is defined as a MIMO detection range symbol number SS,
A detection target block is configured from the blocks in the number equal to the number d of MIMO transmissions, and the MIMO detection range is set to a range from the MIMO block number included in a first block in the detection target block to a leading pilot signal included in a first block in the detection target block next to the detection target block,
The number of pilot signal symbols c is a power of 2 (A), the number of MIMO detection range symbols SS is a power of 2 and is expressed by the formula: SS = (a + b) × d + c × (2 × d-1) (B), and the two consecutive pilot signals included in a first block in the detection target block are the same (C).
a MIMO channel estimator for each reception system that performs a Fourier transform on the pilot signal, estimates the MIMO channel, upsamples the MIMO channel so that the MIMO channel coincides with a preset number of symbols SS of the MIMO detection range, and outputs the upsampled MIMO channel;
a Fourier transform unit for each reception system that performs a Fourier transform on the MIMO detection range corresponding to a preset number SS of MIMO detection range symbols and outputs a frequency domain signal;
a frequency domain MIMO channel equalization unit that receives the upsampled MIMO channel output by the MIMO channel estimation unit and the frequency domain signal output by the Fourier transform unit, and performs MIMO channel equalization in the frequency domain using the upsampled MIMO channel and the frequency domain signal corresponding to a predetermined MIMO detection range symbol number SS;
A single carrier MIMO receiving device comprising:

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