JP2008035442A - Multi-antenna receiver, multi-antenna transmitter, and multi-antenna communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-antenna receiver capable of establishing the compatibility between the improvement of an error rate characteristic and the simplicity of the receiver configuration. <P>SOLUTION: The multi-antenna receiver includes: soft output sections 506_A, 506_B for applying soft decision to a modulation signal on the basis of a signal output point distance between a plurality of candidate signal points and a receiving point; decoding sections 508_A, 508_B for obtaining digital data of the modulation signal by using a result of the soft decision; and signal point reduction sections 510_A, 511_A, 510_B, 511_B, for reducing the number of the candidate signal points used by the soft output sections by recursively using the digital data obtained by the decoding sections, and the soft output sections discriminate the modulation signal on the basis of a first signal point distance between the signal point of the received signal and each candidate signal point reduced by the signal point reduction sections and a second signal point distance between each candidate signal point reduced by the signal point reduction sections and a tentative determined signal point tentatively determined by recursively using the digital data obtained by the decoding sections. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-antenna reception apparatus, a multi-antenna transmission apparatus, and a multi-antenna communication system, and in particular, receives different modulation signals simultaneously transmitted from a plurality of antennas on the transmission side by a plurality of antennas, The present invention relates to a technique for restoring transmission data corresponding to each modulation signal from received signals.

  Conventionally, as in a communication method called MIMO (Multiple-Input Multiple-Output), a plurality of series of transmission data is modulated, and each modulation data is simultaneously transmitted from a plurality of antennas, thereby increasing the data communication speed. There is what I did. On the receiving side, transmission signals from a plurality of antennas are received by a plurality of antennas.

  Here, since the received signal obtained by each receiving antenna is a mixture of a plurality of modulated signals in the propagation space, in order to restore the data corresponding to each modulated signal, the propagation path of each modulated signal is used. Must be estimated (hereinafter referred to as channel fluctuation). For this reason, the transmitting apparatus inserts a known signal such as a pilot symbol in the modulated signal in advance, and the receiving apparatus performs channel fluctuation in the propagation space between each transmitting antenna and each receiving antenna based on the known signal inserted in the modulated signal. presume. Then, each modulation signal is demodulated using this channel fluctuation estimated value.

  As one of the methods, there is a method of separating each modulated signal by performing an inverse matrix operation of a matrix having a channel fluctuation estimated value as an element. As another method, a candidate signal point position is obtained using a channel fluctuation estimated value, and maximum likelihood determination (MLD: Maximum Likelihood Detection) is performed between the candidate signal point position and the received signal point position. There is a method for restoring data transmitted by a modulated signal.

  A communication technique using such a multi-antenna is disclosed in Non-Patent Document 1, for example. Hereinafter, the contents disclosed in Non-Patent Document 1 will be briefly described with reference to FIG. The multi-antenna transmission apparatus 30 inputs the transmission signal A and the transmission signal B to the modulation signal generation unit 3. The modulation signal generation unit 3 performs digital modulation processing such as QPSK (Quadrature Phase Shift Keying) and 16QAM (Quadrature Amplitude Modulation) on the transmission signals A and B, and the baseband signals 4 and 5 obtained thereby are transmitted to the radio unit. 6 to send. The radio unit 6 performs radio processing such as up-conversion and amplification on the baseband signals 4 and 5, and sends the modulated signals 7 and 8 obtained thereby to the antennas 9 and 10. In this way, the multi-antenna transmission apparatus 30 transmits the modulated signal 7 of the transmission signal A from the antenna 9 and simultaneously transmits the modulated signal 8 of the transmission signal B from the antenna 10.

  The multi-antenna reception apparatus 40 inputs the reception signal 12 received by the antenna 11 to the wireless unit 13 and inputs the reception signal 16 received by the antenna 15 to the wireless unit 17. Radio units 13 and 17 perform radio processing such as down-conversion on received signals 12 and 16, and send baseband signals 14 and 18 obtained thereby to demodulation unit 19.

  The demodulator 19 detects the baseband signals 14 and 18 to obtain a reception digital signal 20 of the transmission signal A and a reception digital signal 21 of the transmission signal B. At this time, in Non-Patent Document 1, the demodulator 19 performs inverse matrix calculation of the channel estimation matrix to obtain the received digital signals 20 and 21, and performs maximum likelihood determination (MLD) to obtain the received digital signals 20 and 21. The method of obtaining is described.

Further, Non-Patent Document 2 describes a method for improving error rate characteristics by performing iterative decoding when reducing the amount of calculation by reducing candidate signal points in the demodulator. Specifically, a technique is described in which re-decoding is performed using received signal points and reduced candidate signal points.
“Multiple-antenna diversity techniques for transmission over fading channels” IEEE WCNC 1999, pp.1038-1042, Sep. 1999. "A study on interleaved application of iterative decoding using signal point reduction in MIMO system -BER characteristics in Rayleigh fading environment-" IEICE, IEICE Technical Report, RCS 2004-8, April 2004

  By the way, in the system using the multi-antenna as described above, although the data communication speed is increased, there is a problem that the configuration of the receiving apparatus is particularly complicated. In particular, in the method of obtaining data corresponding to each modulation signal by performing maximum likelihood determination (MLD), the number of operations required for maximum likelihood determination between candidate signal points and reception points increases, so that the circuit scale increases. End up.

  Specifically, considering the case where the number of transmitting antennas is 2 and the number of receiving antennas is 2, when 4Q4 = 16 candidate signal points exist when a modulated signal subjected to QPSK is transmitted from each antenna become. Further, when a modulated signal subjected to 16QAM is transmitted from each antenna, there are 16 × 16 = 256 candidate signal points. When maximum likelihood determination (MLD) is performed, it is necessary to calculate the distance between an actual reception point and all these candidate signals, which requires enormous calculation and leads to an increase in circuit scale.

  On the other hand, in the method of performing determination after separating each modulated signal from the received signal using the inverse matrix of the channel estimation matrix, the number of operations is smaller than the method of performing maximum likelihood determination (MLD). Although the circuit scale is small, the error rate characteristic is lowered depending on the radio wave propagation environment. As a result, there is a drawback that the error rate characteristic of the received data is deteriorated. When the error rate characteristic is lowered, the substantial data communication speed is lowered.

  Further, the technique described in Non-Patent Document 2 can certainly improve the error rate characteristics, but a configuration that can further improve the error rate characteristics without complicating the apparatus configuration is desired. Yes.

  The present invention has been made in view of such points, and an object thereof is to provide a multi-antenna receiving apparatus, a multi-antenna transmitting apparatus, and a multi-antenna communication system capable of achieving both improvement in error rate characteristics and simplification of the apparatus configuration. And

  In order to solve such a problem, the multi-antenna receiving apparatus of the present invention receives a plurality of modulated signals transmitted simultaneously from a plurality of antennas by a plurality of antennas, and restores a data sequence corresponding to each of the plurality of modulated signals from the received signal. A multi-antenna receiving apparatus that determines the modulation signal based on signal point distances between a plurality of candidate signal points for a signal obtained by multiplexing the plurality of modulation signals and a signal point of the reception signal A decoding unit that obtains digital data of the modulated signal using the determination result obtained by the determination unit, and the digital data obtained by the decoding unit is used recursively and the determination unit uses the digital data obtained by the decoding unit. A signal point reduction unit that reduces the number of candidate signal points, and the determination unit includes signal points of each candidate signal point and the received signal that are reduced by the signal point reduction unit. The first signal point distance and the second of the candidate signal points reduced by the signal point reduction unit and the provisionally determined signal points that are provisionally determined using the digital data obtained by the decoding unit recursively. The modulation signal is determined based on the signal point distance.

  According to this configuration, since the determination unit determines the modulation signal based on the signal point distance between the candidate signal point and the reception point reduced by the signal point reduction unit, the signal of all candidate signal points and the reception point is determined. Compared with the case of calculating the point distance, the operation scale can be remarkably reduced. In addition, the determination unit includes not only the first signal point distance between each candidate signal point and reception point reduced by the signal point reduction unit, but also each candidate signal point and decoding unit reduced by the signal point reduction unit. Since the modulation signal is determined using the second signal point distance to the provisionally determined signal point that is provisionally determined using the obtained digital data recursively, the modulation signal is determined only by the first signal point distance. Compared to the case, determination errors can be reduced.

  Also, the multi-antenna reception apparatus of the present invention receives a plurality of modulated signals transmitted simultaneously from a plurality of antennas by a plurality of antennas, and multi-antenna reception for restoring a data sequence corresponding to each of the plurality of modulated signals from the received signal. An apparatus for determining the modulation signal based on a signal point distance between a plurality of candidate signal points for a signal obtained by multiplexing the plurality of modulation signals and a signal point of the reception signal; Using the determination result obtained by the determination unit, a decoding unit that obtains the digital data of the modulated signal, and the digital data obtained by the decoding unit are used recursively, and the candidate signal points used in the determination unit A signal point reduction unit that reduces the number of signal points, and the determination unit includes a first signal point distance between each candidate signal point reduced by the signal point reduction unit and the signal point of the received signal. And determining the modulation signal based on a second signal point distance between a tentatively determined signal point temporarily determined using the digital data obtained by the decoding unit and a signal point of the received signal. Take the configuration.

  According to this configuration, since the determination unit determines the modulation signal based on the signal point distance between the candidate signal point and the reception point reduced by the signal point reduction unit, the signal of all candidate signal points and the reception point is determined. Compared with the case of calculating the point distance, the operation scale can be remarkably reduced. In addition, the determination unit tentatively determines not only the first signal point distance between each candidate signal point and the reception point reduced by the signal point reduction unit but also the digital data obtained by the decoding unit recursively. Since the modulation signal is determined using the second signal point distance between the tentatively determined signal point and the reception point, the determination error is reduced as compared with the case where the modulation signal is determined only by the first signal point distance. it can.

  The multi-antenna transmission apparatus of the present invention includes a plurality of turbo encoders provided in each antenna branch, each including an interleaver having the same interleave pattern, and modulation for modulating encoded data obtained by the turbo encoder. And a plurality of reordering units that are provided in each antenna branch and reorder the encoded data obtained by each turbo encoder or each encoded data after modulation in different reordering patterns. Take.

  Further, the multi-antenna communication system of the present invention provides the modulated signal based on a signal point distance between a plurality of candidate signal points for a received signal obtained by spatially multiplexing a plurality of modulated signals and a signal point of the received signal. Using a determination result obtained by the determination unit, recursively digital data other than the self-modulated signal obtained by the decoding unit, and a decoding unit that obtains digital data of the modulated signal. A multi-antenna receiving apparatus having a signal point reducing unit that reduces the number of candidate signal points used in the determination unit, and a plurality of turbo codes provided in each antenna branch, each including an interleaver having the same interleave pattern , A modulation unit that modulates the encoded data obtained by the turbo encoder, and each turbo encoder provided in each antenna branch A configuration having a, a multi-antenna transmission apparatus having a plurality of rearrangement unit for rearranging in each different rearrangement patterns more coded data obtained or each coded data after modulation.

  According to these configurations, the rearrangement unit makes the order of the encoded data or the modulation symbol of the modulation signal transmitted from each antenna different between the antenna branches (modulation signals). This signal point reduction error occurs discretely. As a result, the error rate characteristic of the digital data finally obtained by the decoding unit is improved. Moreover, since the interleave pattern of the interleaver built in the turbo encoder is the same, the error rate characteristic can be improved without complicating the configuration of the decoding unit.

  As described above, according to the present invention, it is possible to realize a multi-antenna receiving apparatus, a multi-antenna transmitting apparatus, and a multi-antenna communication system capable of improving both error rate characteristics and simplifying the apparatus configuration.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a configuration example of multi-antenna transmission apparatus 100 of the present embodiment. In this embodiment, in order to simplify the description, a case in which there are two transmission antennas and two reception antennas will be described. However, the present invention relates to M (M ≧ 2) transmission antennas, N The present invention can also be applied to a multi-antenna system having (N ≧ 2) reception antennas.

  Encoding section 102_A receives transmission data 101_A of modulated signal A and frame configuration signal 110 as input, and encodes the frame configuration signal 110 (for example, convolutional encoding, turbo encoding, LDPC (Low Density Parity Check)). Encoding data 103_A of the modulated signal A after encoding is obtained. Similarly, encoding section 102_B receives transmission data 101_B of modulated signal B and frame configuration signal 110 as input, and encodes modulated signal B after encoding by performing encoding indicated by frame configuration signal 110. Data 103_B is obtained.

  The modulation unit 104_A receives the encoded data 103_A of the modulated signal A and the frame configuration signal 110 as input, and performs mapping based on the modulation scheme indicated by the frame configuration signal 110, thereby performing the baseband signal 105_A of the modulation signal A. Get. Similarly, the modulation unit 104_B receives the encoded data 103_B of the modulation signal B and the frame configuration signal 110 as input, and performs mapping based on the modulation scheme indicated by the frame configuration signal 110, whereby the base of the modulation signal B is obtained. A band signal 105_B is obtained.

  Radio section 106_A receives baseband signal 105_A of modulated signal A, performs frequency conversion and amplification, and obtains transmission signal 107_A of modulated signal A. The transmission signal 107_A is output as a radio wave from the antenna 108_A. Similarly, the radio unit 106_B receives the baseband signal 105_B of the modulated signal B, performs frequency conversion and amplification, and obtains a transmission signal 107_B of the modulated signal B. The transmission signal 107_B is output as a radio wave from the antenna 108_B.

  The frame configuration signal generation unit 109 outputs a frame configuration signal 110 that is information regarding the frame configuration.

  FIG. 2 shows a frame configuration example of a modulated signal transmitted from each antenna 108 </ b> _A and 108 </ b> _B of multi-antenna transmission apparatus 100. The modulated signal A (FIG. 2 (a)) transmitted from the antenna 108_A and the modulated signal B (FIG. 2 (b)) transmitted from the antenna 108_B are channel fluctuation estimation symbols 201_A and 201_B and data symbols 202_A and 202_B, respectively. And have. Multi-antenna transmission apparatus 100 transmits modulated signal A and modulated signal B having the frame structure shown in FIG. 2 at substantially the same time. Note that the symbols 201_A and 201_B for channel fluctuation estimation are, for example, symbols with known signal point arrangements in the in-phase I-orthogonal Q plane in transmission / reception (generally called pilot symbols, preambles, etc., but are not limited thereto). ), And is a symbol used to estimate channel fluctuations on the receiving side. The data symbol is a symbol for transmitting data.

  The symbol of modulated signal A and the symbol of modulated signal B at the same time are transmitted using the same frequency.

  FIG. 3 shows a configuration example of multi-antenna reception apparatus 300 according to the present embodiment. Radio section 303_X receives reception signal 302_X received by antenna 301_X, performs predetermined radio reception processing such as frequency conversion on reception signal 302_X, and outputs baseband signal 304_X. Radio section 303_Y receives reception signal 302_Y received by antenna 301_Y, performs predetermined radio reception processing such as frequency conversion on reception signal 302_Y, and outputs baseband signal 304_Y.

  The channel fluctuation estimation unit 305_A of the modulation signal A receives the baseband signal 304_X, detects the channel fluctuation estimation symbol of the modulation signal A in FIG. 2, and based on the channel fluctuation estimation symbol of the modulation signal A, the channel of the modulation signal A The fluctuation is estimated, and a channel fluctuation estimation signal 306_A of the modulated signal A is output.

  The channel fluctuation estimation unit 305_B of the modulation signal B receives the baseband signal 304_X, detects the channel fluctuation estimation symbol of the modulation signal B in FIG. 2, and detects the channel fluctuation of the modulation signal B based on the channel fluctuation symbol of the modulation signal B. And a channel fluctuation estimation signal 306_B of the modulation signal B is output.

  Accordingly, channel fluctuation between the transmission antennas 108_A and 108_B and the reception antenna 301_X is estimated by the channel fluctuation estimation units 305_A and 305_B.

  The multi-antenna receiving apparatus 300 performs the same processing on the branch of the receiving antenna 301_Y. This will be specifically described. Radio section 303_Y receives reception signal 302_Y received by antenna 301_Y, performs predetermined radio reception processing such as frequency conversion on reception signal 302_Y, and outputs baseband signal 304_Y.

  The channel fluctuation estimation unit 307_A of the modulation signal A receives the baseband signal 304_Y, detects the channel fluctuation estimation symbol of the modulation signal A in FIG. 2, and based on the channel fluctuation estimation symbol of the modulation signal A, the channel of the modulation signal A The fluctuation is estimated, and a channel fluctuation estimation signal 308_A of the modulated signal A is output.

  The channel fluctuation estimation unit 307_B of the modulation signal B receives the baseband signal 304_Y, detects the channel fluctuation estimation symbol of the modulation signal B in FIG. 2, and detects the channel fluctuation of the modulation signal B based on the channel fluctuation symbol of the modulation signal B. And a channel fluctuation estimation signal 308_B of the modulated signal B is output.

  Accordingly, channel fluctuations between the transmission antennas 108_A and 108_B and the reception antenna 301_Y are estimated by the channel fluctuation estimation units 307_A and 307_B.

  The signal processing unit 309 receives the channel fluctuation estimation signals 306_A and 308_A of the modulation signal A, the channel fluctuation estimation signals 306_B and 308_B of the modulation signal B, and the baseband signals 304_X and 304_Y, and is included in the baseband signals 304_X and 304_Y. The baseband signal components of the modulated signal A and the modulated signal B are separated, and the modulated signal A and the modulated signal B are subjected to decoding processing, whereby the received data 310_A of the decoded modulated signal A and the decoded modulated signal are decoded. B received data 310_B is obtained.

FIG. 4 shows the relationship between the transmitting and receiving apparatuses in the present embodiment. The modulation signal A transmitted from the antenna 108_A of the multi-antenna transmission apparatus 100 is Ta (t), and the modulation signal B transmitted from the antenna 108_B is Tb (t). Further, a received signal received by the antenna 301_X of the multi-antenna receiving apparatus 300 is R1 (t), and a received signal received by the antenna 301_Y is R2 (t). Further, the channel fluctuation between the antennas 108_A and 301_X is h11 (t), the channel fluctuation between the antennas 108_A and 301_Y is h12 (t), the channel fluctuation between the antennas 108_B and 301_X is h21 (t), and between the antennas 108_B and 301_Y. Let channel fluctuation be h22 (t) (where t is time). Then, the following relational expression is established.

  The channel fluctuations h11 (t), h12 (t), h21 (t), and h22 (t) are estimated by the channel fluctuation estimation units 305_A, 305_B, 307_A, and 307_B in FIG.

  FIG. 5 shows a configuration example of the signal processing unit 309. The signal processing unit 309 includes a separation unit 504, a storage unit 520, signal point reduction units 510_A, 511_A, 510_B, and 511_B, soft output units 506_A and 506_B, and decoding units 508_A and 508_B. Here, a case where the modulation method of the modulation signals A and B is QPSK will be described as an example.

  The demultiplexing unit 504 includes channel fluctuation estimation signals 501_A (306_A in FIG. 3) and 502_A (308_A in FIG. 3) of the modulation signal A, channel fluctuation estimation signals 501_B (306_B in FIG. 3) and 502_B (FIG. 3) of the modulation signal B. 308_B), baseband signal 503_X (304_X in FIG. 3), and baseband signal 503_Y (304_Y in FIG. 3) as inputs, and from the relational expression of Expression (1), ZF (Zero Forcing) or MMSE (Minimum Mean Square Error) By performing detection using an algorithm, an estimated baseband signal 505_A of the modulated signal A and an estimated baseband signal 505_B of the modulated signal B are obtained.

  The storage unit 520 stores channel fluctuation signals 501_A, 501_B, 502_A, 502_B, and baseband signals 503_X, 503_Y in order to absorb a delay of time required for iterative decoding, and outputs these when necessary. To do.

  The signal point reduction unit 510_A receives the channel fluctuation estimation signal 501_A of the modulation signal A from the storage unit 520 (that is, h11 (t) in Expression (1)) and the channel fluctuation estimation signal 501_B of the modulation signal B (that is, Expression (1)). H12 (t)) and the decoded data 509_B of the modulated signal B from the decoding unit 508_B. Actually, when the i-th iterative operation is currently being performed, the data 509_B after decoding of the modulation signal B is used as the data 509_B of the modulation signal B at time t obtained by the decoding unit 508_B in the i-1th decoding. The decrypted data is used as input. The other signal point reduction units 511_A, 510_B, and 511_B also perform basically the same processing as the signal point reduction unit 510_A, except that the input signals are different as shown in FIG. Therefore, in the following, the processing of the signal point reduction unit 510_A will be mainly described on behalf of these.

  FIG. 6 shows the positions of the candidate signal points in the in-phase I-quadrature Q plane and the positions of the reception signal points that can be obtained from the channel fluctuation estimation signal 501_A of the modulation signal A and the channel fluctuation estimation signal 501_B of the modulation signal B. As shown in FIG. 6, when the modulation method of modulated signal A and modulated signal B is QPSK, 16 candidate signal points 601 to 616 exist. In the figure, 600 indicates a received signal point, that is, a baseband signal 503_X. In FIG. 6, the bit arrangement corresponding to the signal point is also shown. Assuming that the 2 bits transmitted by the modulated signal A are a0 and a1, and the 2 bits transmitted by the modulated signal B are b0 and b1, in FIG. 6, the corresponding relationship is (modulated signal A, modulated signal B) = (a0, a1 , B0, b1).

  Here, as shown in FIG. 6, when the square of the Euclidean distance between all candidate signal points (16 points) and the received signal point 600 is obtained, and the candidate signal point with the shortest distance is detected, the computation scale is large. Increase. Here, the case where the modulation method is QPSK is described, but the increase in the operation scale becomes more remarkable as the number of modulation multi-levels of the modulation method becomes larger or as the number of modulation signals to be transmitted increases by increasing the number of transmission antennas. It becomes. The signal point reduction units 510_A, 511_A, 510_B, and 511_B all the candidate signal points (16 points) 601 while suppressing a decrease in error rate characteristics by accurately reducing substantially unnecessary candidate signal points. This makes it possible to eliminate the square of the Euclidean distance between ˜616 and the received signal point 600. That is, the signal point reduction units 510_A, 511_A, 510_B, and 511_B perform candidate signal point reduction processing that achieves both a reduction in computation scale and an improvement in error rate characteristics.

  Specifically, the signal point reduction processing of the signal point reduction unit 510_A will be described.

  Here, it is assumed that the decoded data (b0, b1) = (0, 0) of the modulated signal B at time t obtained by the i−1th decoding in the decoding unit 508_B. Based on the data of (b0, b1) = (0, 0), the signal point reduction unit 510_A, as shown in FIG. 7, (b0, b1) of the 16 candidate signal points in FIG. Four signal points with = (0, 0) are obtained.

  This processing is performed using data already determined for a modulation signal (modulation signal B in the above description) other than the self modulation signal (modulation signal A in the above description), and a candidate signal for the self modulation signal. It can be said that the points are reduced. Incidentally, an important feature in the signal point reduction processing in the present embodiment is that 16 signal points are obtained and then not limited to 4 signal points, but data of other already determined modulation signals are used. Thus, four signal points are directly obtained. As a result, it is possible to realize accurate signal point reduction processing while reducing the computation scale required for signal point reduction processing.

  The signal point reduction unit 510_A outputs information on the four candidate signal points as a candidate signal point signal 512_A.

  Next, the soft output units 506_A and 506_B will be described. Note that the configurations and operations of the soft output unit 506_A and the soft output unit 506_B are the same except that the signals to be processed are different. Therefore, the configuration and operation of the soft output unit 506_A will be mainly described below.

  The soft output unit 506_A (506_B) is a signal point between the candidate signal points 512_A and 513_A (512_B and 513_B) reduced by the signal point reduction units 510_A and 511_A (510_B and 511_B) and the reception signal points of the reception signals 503_X and 503_Y. The distance is obtained as the first signal point distance, and the signals of the determination result signal points obtained by using the results determined by the decoding units 508_A and 508_B and the reduced candidate signal points 512_A, 513_A (512_B, 513_B) A point distance is obtained as a second signal point distance, and digital data for the self-modulated signal point is obtained based on the first signal point distance and the second signal point distance.

  FIG. 8 shows a specific configuration example of the soft output unit 506_A. The soft output unit 506_A includes an iterative decoding soft decision unit 801, an initial decoding soft decision unit 802, and a signal selection unit 803. The iterative decoding soft decision unit 801 receives candidate signal point signals 512_A and 513_A, baseband signals 503_X and 503_Y, decoded data 509_A of the modulated signal A, and decoded data 509_B of the modulated signal B. The branch metric 804 of the modulated signal A is output.

  Initial decoding soft decision section 802 receives estimated baseband signal 505_A of modulated signal A as input, and outputs branch metric 805 of modulated signal A at the time of initial decoding.

  The signal selection unit 803 receives the branch metric 804 of the modulation signal A at the time of iterative decoding and the branch metric 805 of the modulation signal A at the time of initial decoding, selects one of them, and selects it as a branch metric 507_A of the modulation signal A. Output as.

  FIG. 9 shows a specific configuration example of the iterative decoding soft decision unit 801. A square Euclidean distance calculation unit 901_X, 901_Y between the reception signal point and the candidate signal point, a square Euclidean distance calculation unit 903_X, 903_Y between the temporarily determined signal point and the candidate signal point, and an addition unit 905 are included.

  Next, detailed operations of the soft output units 506_A and 506_B will be described. Here, the soft output operation of the modulation signal A, that is, the operation of the soft output unit 506_A will be described. Note that the operation of the modulation signal B, that is, the operation of the soft output unit 506_B is the same as the operation of the soft output unit 506_A, and thus description thereof is omitted.

(First soft output)
The soft output unit 506_A performs the first soft output processing in the initial decoding soft decision unit 802 (FIG. 8). That is, soft output section 506_A inputs estimated baseband signal 505_A of modulated signal A to initial decoding soft decision section 802 at the first soft output. FIG. 10 shows a state example of the estimated baseband signal 505_A in the in-phase I-quadrature Q plane. In FIG. 10, reference numeral 1001 denotes a received signal point, that is, an estimated baseband signal 505_A of the modulated signal A. Reference numeral 1002 indicates the relationship between QPSK signal points and bit arrangement, and the coordinates of the signal points 1002 are known in the receiving apparatus.

  The initial decoding soft decision section 802 calculates the square of the Euclidean distance between the received signal point 1001 and each signal point 1002 of QPSK, that is, Da [0,0], Da [0,1], Da [ 1,0], Da [1,1] are obtained. Then, initial decoding soft decision section 802 outputs these four values as branch metrics 805 of modulated signal A at the time of initial decoding. Then, the branch metric 805 of the modulated signal A is output from the signal selection unit 803 as the soft decision value 507_A of the modulated signal A.

(Soft output after the second time)
The soft output unit 506_A performs the second soft output processing by the iterative decoding soft decision unit 801 (FIG. 8). As shown in FIG. 9, iterative decoding soft decision section 801 inputs baseband signal 503_X and candidate signal point signal 512_A to squared Euclidean distance calculation section 901_X between the received signal point and the candidate signal point.

  As shown in FIG. 7, the square Euclidean distance calculation unit 901_X between the reception signal point and the candidate signal point is a candidate signal point and reception signal when the bit (a0, a1) = (0, 0) of the modulation signal A. The square Euclidean distance Xa [0,0] between the point and the square Euclidean distance Xa [0,0] between the candidate signal point and the reception signal point when the bit (a0, a1) = (0,1) of the modulation signal A 1], square Euclidean distance Xa [1, 0] between the candidate signal point and the received signal point when bit (a0, a1) = (1, 0) of modulated signal A, bit (a0, The square Euclidean distance Xa [1,1] between the candidate signal point and the received signal point when a1) = (1,1) is obtained, and this is output as the first branch metric signal 902_X.

  The square Euclidean distance calculation unit 903_X between the tentatively determined signal point and the candidate signal point receives the candidate signal point signal 512_A, the demodulated data 509_A, and the demodulated data 509_B of the modulated signal B. FIG. 11 shows the relationship between candidate signal points and provisionally determined signal points on the in-phase I-orthogonal Q plane. It is assumed that the decoding result (b0, b1) = (0, 0) of the modulation signal B at time i−1 and time t. In this case, 601, 606, 611 and 616 are candidate signal points. In addition, the decoding result (a0, a1) = (1, 0) of the modulation signal A at time i−1, time t. In this case, the provisional decision signal point is determined as one point 606.

  The square Euclidean distance calculation unit 903_X between the tentatively determined signal point and the candidate signal point determines the tentatively determined signal point 606 in this way, and the tentatively determined signal point 606 and each candidate signal point 601, 606, 611, The square Euclidean distance from 616 is obtained. That is, the square Euclidean distance calculation unit 903_X between the tentatively determined signal point and the candidate signal point is the candidate signal point 601 and tentatively determined signal point when the bit (a0, a1) = (0, 0) of the modulation signal A The square Euclidean distance Ya between the candidate signal point 611 and the provisional decision signal point 606 when the square Euclidean distance Ya [0, 0] to 606 and the bits (a0, a1) of the modulation signal A = (0, 1). [0, 1], square Euclidean distance Ya [1, 0] between candidate signal point 606 and provisionally determined signal point 606 when bit (a0, a1) = (1, 0) of modulated signal A, modulated signal The square Euclidean distance Ya [1, 1] between the candidate signal point 616 and the provisionally determined signal point 606 when the bit (a0, a1) of A is (1, 1) is obtained, and this is obtained as the second branch metric signal. Output as 904_X.

  The square Euclidean distance calculation unit 901_Y between the reception signal point and the candidate signal point receives the baseband signal 503_Y and the candidate signal point signal 513_A, and the square Euclidean distance calculation unit 901_X between the reception signal point and the candidate signal point described above. The first branch metric signal 902_Y is obtained by the same operation as.

  The square Euclidean distance calculation unit 903_Y between the tentative decision signal point and the candidate signal point receives the candidate signal point signal 513_A, the demodulated data 509_A of the modulation signal A, and the demodulated data 509_B of the modulation signal B as described above. The second branch metric signal 904_Y is obtained by the same operation as the square Euclidean distance calculation unit 903_X between the provisional decision signal point and the candidate signal point.

  The adder 905 receives the first branch metrics 902_X and 902_Y and the second branch metrics 904_X and 904_Y, and inputs the modulated signal A in the first branch metrics 902_X and 902_Y and the second branch metrics 904_X and 904_Y. A branch metric corresponding to bit (a0, a1) = (0, 0) is extracted and added to obtain a branch metric of bit (a0, a1) = (0, 0) of modulated signal A. Similarly, the addition unit 905 obtains branch metrics of bits (a0, a1) = (0, 1), (1, 0), (1, 1) of the modulation signal A. Then, the adding unit 905 outputs these branch metrics as the branch metric signal 804 of the modulation signal A at the time t of the number of iterations i.

  The soft output unit 506_A for the modulation signal A has been described above, but the soft output unit 506_B for the modulation signal B performs the same configuration and operation to obtain the branch metric of the modulation signal B.

  Decoding section 508_A receives soft decision value 507_A of modulated signal A as input, for example, calculates a log likelihood ratio and performs decoding, thereby outputting decoded data 509_A of modulated signal A. Similarly, decoding section 508_B receives soft decision value 507_B of modulated signal B as input, calculates log likelihood ratio, for example, and outputs decoded data 509_B of modulated signal B.

  Here, what is important is not only the signal point distance between each of the reduced candidate signal points and the reception point, but also the result of the i−1th iteration decoding in each of the reduced candidate signal points in the soft output units 506_A and 506_B. The branch metric is obtained by using the signal point distance to the temporarily determined signal point temporarily determined using Thereby, the error rate characteristics of the decoded data 509_A and 509_B finally obtained by the decoding units 508_A and 508_B can be improved.

  As described above, according to the present embodiment, a modulation signal is determined based on signal point distances between a plurality of candidate signal points for a signal obtained by multiplexing a plurality of modulation signals and a signal point of a received signal. A determination unit (soft output units 506_A, 506_B), a decoding unit (508_A, 508_B) that obtains digital data of a modulation signal using the determination result obtained by the determination unit (soft output units 506_A, 506_B), and a decoding Signal point reduction units (510_A, 511_A, 510_B, 510B) that reduce the number of candidate signal points used in the determination unit (soft output units 506_A, 506_B) by recursively using the digital data obtained by the unit (508_A, 508_B). 511_B), and in the determination units (soft output units 506_A, 506_B), signal point reduction units (510_A, 511_A, 10_B, 511_B), the first signal point distance between each candidate signal point and the signal point of the received signal, and each candidate signal point reduced by the signal point reduction unit (510_A, 511_A, 510_B, 511_B) The modulation signal is determined on the basis of the second signal point distance from the provisionally determined signal point that is provisionally determined by recursively using the digital data obtained by the decoding units (508_A, 508_B).

  Thereby, the determination unit (soft output units 506_A and 506_B) determines the modulation signal based on the signal point distance between the candidate signal point and the reception point reduced by the signal point reduction unit (510_A, 511_A, 510_B, and 511_B). Therefore, the calculation scale can be remarkably reduced as compared with the case of calculating signal point distances between all candidate signal points and reception points. In addition, the determination unit (soft output unit 506_A, 506_B) is not only the first signal point distance between each candidate signal point and the reception point reduced by the signal point reduction unit (510_A, 511_A, 510_B, 511_B). Tentatively determined signal points that are provisionally determined by recursively using each candidate signal point reduced by the signal point reducing unit (510_A, 511_A, 510_B, 511_B) and the digital data obtained by the decoding unit (508_A, 508_B), Since the modulation signal is determined using the second signal point distance, determination errors can be reduced as compared with the case where the modulation signal is determined only by the first signal point distance.

  In the above-described embodiment, the case where iterative decoding soft decision section 801 is configured as shown in FIG. 9 has been described. However, the configuration of iterative decoding soft decision section is not limited to that shown in FIG. . FIG. 12 in which the same reference numerals are assigned to corresponding parts as in FIG. 9 shows another example of the configuration of the iterative decoding soft decision unit 801. The iterative decoding soft decision unit of FIG. 12 differs from the iterative decoding soft decision unit of FIG. 9 in the branch metric calculation method.

  This will be specifically described. Compared to the iterative decoding soft decision unit 801 in FIG. 9, the iterative decoding soft decision unit 801 in FIG. 12 is replaced with the square Euclidean distance calculation units 903_X and 903_Y between the tentatively determined signal points and the candidate signal points. , Square Euclidean distance calculation units 1101_X and 1101_Y between the reception signal points and the provisionally determined signal points are provided.

  The square Euclidean distance calculation unit 1101_X between the reception signal point and the provisionally determined signal point inputs the baseband signal 503_X, the candidate signal point 512_X, the decoded data 509_A of the modulated signal A, and the decoded data 509_B of the modulated signal B. And

  FIG. 13 shows the positional relationship among candidate signal points, provisionally determined signal points, and received signal points on the in-phase I-orthogonal Q plane. The decoding result (b0, b1) = (0, 0) of the modulated signal B at time i−1 and time t is set to (b0, b1) = (0, 0), and the decoding result (a0, a1) = (1, 0), the provisional decision signal point is 606.

The square Euclidean distance calculation unit 1101_X between the reception signal point and the provisional decision signal point determines the provisional decision signal point 606 in this way, and the square Euclidean distance σ ² between the provisional decision signal point 606 and the reception signal point 600. Ask for. At this time, σ ² can be approximated with an estimated value of noise variance. Therefore, the square Euclidean distance calculation unit 1101_X between the reception signal point and the provisionally determined signal point outputs σ ² as the noise variance estimation signal 1102_X.

The division unit 1103_X receives the first branch metric signal 902_X and the noise variance estimation signal 1102_X, and divides each branch metric by the noise variance. That is, the division unit 1103_X obtains Xa [0,0] / σ ² , Xa [0,1] / σ ² , Xa [1,0] / σ ² , Xa [1,1] / σ ² , and Is output as a first branch metric signal 1104_X after division.

  Similarly, the division unit 1103_Y outputs a first branch metric signal 1104_Y after division.

  The addition unit 1105 receives the first branch metric signals 1104_X and 1104_Y after division, and the branch metric corresponding to (a0, a1) = (0, 0) of the first branch metric signal 1104_X after division; A branch metric corresponding to (a0, a1) = (0, 0) is obtained by adding the branch metric corresponding to (a0, a1) = (0, 0) of the first branch metric signal 1104_Y after division. . Similarly, branch metrics of (a0, a1) = (0, 1), (1, 0), (1, 1) are obtained. Then, the adding unit 1105 outputs these branch metrics as the branch metric signal 804 of the modulation signal A at the time t at the i-th iteration.

  FIG. 14 shows still another configuration example of the iterative decoding soft decision unit 801. The iterative decoding soft decision section 801 shown in FIG. 14 with the same reference numerals assigned to the parts corresponding to those in FIG. 9 has an integrator 1401. The integrator 1401 receives the first branch metrics 902_X and 902_Y as inputs.

here,
The square Euclidean distance between the candidate signal point and the received signal point when the bit (a0, a1) = (0, 0) of the modulation signal A is represented by Xa [0, 0],
The square Euclidean distance between the candidate signal point and the received signal point when the bit (a0, a1) = (0, 1) of the modulation signal A is Xa [0, 1],
The square Euclidean distance between the candidate signal point and the received signal point when the bit (a0, a1) = (1, 0) of the modulation signal A is Xa [1, 0],
The square Euclidean distance between the candidate signal point and the received signal point when the bit (a0, a1) = (1, 1) of the modulation signal A is Xa [1, 1].

  The integrator 1401 calculates the square Euclidean distance Xa [0, 0] between the candidate signal point and the received signal point when the bit (a0, a1) = (0, 0) of the modulation signal A from the 0th iteration. By integrating until the first time, an integration value when the bit (a0, a1) = (0, 0) of the modulation signal A is obtained. The integrator 1401 performs the same integration process on the bits (a0, a1) = (0, 1), (1, 0), (1, 1) of the modulation signal A, and obtains the obtained integration value. , And output as the first branch metric 1402. Adder 905 adds the corresponding branch metrics and outputs the addition result as branch metric signal 804 of modulated signal A.

  In this embodiment, the case of a multi-antenna system having two transmission antennas and two reception antennas has been described. However, the present invention is not limited to this, and the number of transmission antennas is two or more and the number of reception antennas is two. As described above, the present invention can be widely applied when the transmission modulation signal is 2 or more.

  In the present invention, any code can be applied as long as it can be decoded using soft decision.

  In the above-described embodiment, the separation unit 504 performs detection using a ZF (Zero Forcing) or MMSE (Minimum Mean Square Error) algorithm, so that the estimated baseband signal 505_A of the modulation signal A and the modulation signal B are detected. The case where the estimated baseband signal 505_B is obtained has been described. That is, a case has been described in which a modulation signal used for initial decoding is obtained by performing ZF (Zero Forcing) or MMSE (Minimum Mean Square Error) algorithm. However, the present invention is not limited to this, and the separation unit 504 may detect a modulation signal used for initial decoding by, for example, inverse matrix calculation, MLD (Maximum Likelihood Detection), and simplified MLD. .

  In the embodiment described above, QPSK has been described as an example of the modulation method. However, the present invention is not limited to this, and even when other modulation methods such as 16QAM and 64QAM are used, the same processing as described above is performed. By performing the above, the same effect can be obtained. Incidentally, the present invention has the advantage that the larger the modulation multi-level number, the greater the effect of reducing the computation scale.

  In the above-described embodiment, the case of the single carrier system has been described as an example. However, the present invention is not limited to this, and the basic configuration similar to the above is applied even when applied to the spread spectrum communication system and the OFDM system. Thus, the same effect can be obtained.

  In the above-described embodiment, the case where there are two encoding units and two decoding units has been described. However, the present invention is not limited to this, and the number of encoding units and decoding units is not limited to the basic configuration and basic configuration of the present invention. It has no effect on the overall effect. Furthermore, even if interleaving, deinterleaving, puncturing, and depuncturing are performed in the encoding unit and decoding unit, the basic configuration and the basic effect of the present invention are not affected at all.

(Embodiment 2)
In the present embodiment, when the turbo code is used, the multi-antenna apparatus presented in the first embodiment is improved to a more preferable configuration.

  FIG. 15 shows a configuration example of multi-antenna transmission apparatus 1500 according to the present embodiment. Turbo encoder 1502_A receives transmission data 1501_A of modulated signal A as input, and turbo-codes transmission data 1501_A to obtain encoded data 1503_A of modulated signal A. Similarly, turbo encoder 1502_B receives transmission data 1501_B of modulated signal B as input, and encodes transmission data 1501_B to obtain encoded data 1503_B of modulated signal B.

  Rearranger 1504_A receives encoded data 1503_A of modulated signal A as input, and outputs encoded data 1505_A after rearrangement of modulated signal A. Similarly, rearrangement section 1504_B receives encoded data 1503_B of modulated signal B as input, and outputs encoded data 1505_B after rearrangement of modulated signal B.

  Mapping section 1506_A receives encoded data 1505_A and frame configuration signal 1516 after rearrangement of modulated signal A, and modulates encoded data 1505_A using a modulation scheme such as QPSK, 16QAM, or 64QAM according to frame configuration signal 1516. Thus, the baseband signal 1507_A of the modulation signal A is obtained. Similarly, mapping section 1506_B receives encoded data 1505_B after rearrangement of modulated signal B and frame configuration signal 1516 as input, and encodes data 1505_B in accordance with a modulation scheme such as QPSK, 16QAM, or 64QAM according to frame configuration signal 1516. By modulating, a baseband signal 1507_B of the modulated signal B is obtained.

  The serial / parallel conversion unit 1508_A receives the baseband signal 1507_A of the modulation signal A and performs serial / parallel conversion to obtain a baseband signal 1509_A of the parallelized modulation signal A. Similarly, the serial / parallel conversion unit 1508_B receives the baseband signal 1507_B of the modulation signal B and performs serial / parallel conversion to obtain a baseband signal 1509_B of the parallelized modulation signal B.

  The inverse Fourier transform unit 1510_A receives the parallel baseband signal 1509_A of the modulated signal A and performs inverse Fourier transform to obtain a signal (ie, OFDM signal) 1511_A after the inverse Fourier transform of the modulated signal A. Similarly, the inverse Fourier transform unit 1510_B receives the baseband signal 1509_B of the parallelized modulation signal B as input, and performs inverse Fourier transform to thereby obtain a signal (ie, OFDM signal) 1511_B after the inverse Fourier transform of the modulation signal B. Get.

  Radio section 1512_A receives signal 1511_A after inverse Fourier transform as input, and performs processing such as frequency conversion and amplification to obtain transmission signal 1513_A of modulated signal A. The transmission signal 1513_A of the modulation signal A is output from the antenna 1514_A as a radio wave. Similarly, the radio unit 1512_B receives the signal 1511_B after the inverse Fourier transform and performs processing such as frequency conversion and amplification to obtain a transmission signal 1513_B of the modulated signal B. The transmission signal 1513_B of the modulation signal B is output from the antenna 1514_B as a radio wave.

  FIG. 16 shows a configuration example of the turbo encoders 1502_A and 1502_B. Element encoder # 1 receives transmission data 1501_A (1501_B) as input, and outputs encoded data 1603. Interleaver 1604 receives transmission data 1501_A (1501_B) as input, and performs interleaving to output data 1605 after interleaving. Element encoding section # 2 receives interleaved data 1605 and outputs encoded data 1607. Puncturing / multiplexing section 1608 receives encoded data 1603 and 1607 as input, and outputs punctured and multiplexed encoded data 1609. Multiplexer 1610 receives transmission data 1501_A (1501_B) and punctured and multiplexed encoded data 1609, and multiplexes them to obtain encoded data 1503_A (1503_B).

  Here, the turbo encoders 1502_A and 1503_B in FIG. 15 are considered. As shown in Non-Patent Document 2, when the interleave patterns of the turbo encoders 1502_A and 1502_B are made different and iterative decoding as described in Embodiment 1 is performed, the reception quality is improved. However, the turbo code has the following disadvantages if the interleave patterns of the turbo encoders 1502_A and 1502_B are made different.

  <1> In the turbo code, the design of the interleaver in the encoder is important for ensuring the reception quality. However, it is difficult to prepare a plurality of interleave patterns with good performance as codes.

  <2> Even if a plurality of high-performance interleave patterns can be prepared, it is difficult to design a decoder corresponding to each of them on the receiving side, and if a different decoder is provided, the circuit scale of the receiving apparatus Becomes larger. Incidentally, if the same code is used, the decoder can be easily shared, and the circuit scale of the receiving apparatus can be reduced.

  In consideration of the above two points, in this embodiment, turbo encoders 1502_A and 1502_B in FIG. 15 perform the same encoding, and the interleaving pattern of internal interleaver 1604 is set to be the same. . In addition, in multi-antenna transmission apparatus 1500 of the present embodiment, rearrangement sections 1504_A and 1504_B are provided on the subsequent stage side of turbo encoders 1502_A and 1502_B.

  In general, when a turbo code is used, an interleaver attached to the turbo encoder is taken into consideration, and thereafter, a configuration for rearranging (interleaving) is not added again. This is because this will only increase the circuit scale and not improve the reception quality.

  However, in multi-antenna transmission apparatus 1500 of the present embodiment, rearrangement units (interleavers) 1504_A and 1504_B are added to the subsequent stage of turbo encoders 1502_A and 1502_B, as shown in FIG. This is because the reception quality of the multi-antenna reception apparatus as described in Embodiment 1 can be improved by adopting such a configuration.

  Hereinafter, this point will be described in detail.

  FIG. 17 illustrates an example of a method of rearranging the rearranging units 1504_A and 1504_B in FIG.

  In FIG. 17, reference numeral 1701 denotes a pilot symbol, which is a symbol for estimating channel fluctuation and frequency offset on the receiving side. Reference numeral 1702 denotes a data symbol.

  FIG. 17A shows the frame configuration of the modulation signal A on the time-frequency axis after the rearrangement processing by the rearrangement unit 1504_A. Specifically, the rearrangement unit 1504_A converts the data in the order of “A1, A2, A3, A4, A5, A6, A7, A8, A9, A10...” In the encoded data 1503_A, As a result of the rearrangement, they are arranged as shown in FIG.

  Similarly, FIG. 17B shows a frame configuration of the modulation signal B on the time-frequency axis after the rearrangement processing by the rearrangement unit 1504_B. Specifically, the rearrangement unit 1504_B converts the data in the encoded data 1503_B in the order of “B1, B2, B3, B4, B5, B6, B7, B8, B9, B10. As a result of the rearrangement, they are arranged as shown in FIG.

  As is clear from comparison between FIG. 17A and FIG. 17B, the rearrangement unit 1504_A and the rearrangement unit 1504_B perform different rearrangement processes, and the data of the modulation signal A within the same time range. And the order of the data of the modulation signal B are made different. In FIG. 17, only the times 2 and 3 are described, but the rearrangement process is also performed after time 4 so that the data order of the modulation signal A and the modulation signal B is different. ing.

  FIG. 18, in which the same reference numerals are assigned to corresponding parts as in FIG. 3, shows a configuration example of the multi-antenna reception apparatus of this embodiment. The multi-antenna reception apparatus 1800 has Fourier transform / parallel serial conversion units 1801_X and 1801_Y, and the configuration of the signal processing unit 1803 is different from that of the signal processing unit 309 (FIG. 3). The configuration is almost the same as that of the receiving apparatus 300.

  The Fourier transform / parallel serial conversion unit 1801_X receives the baseband signal (OFDM signal) 304_X and performs Fourier transform and parallel serial conversion processing to obtain a baseband signal 1802_X after signal processing. Similarly, the Fourier transform / parallel serial conversion unit 1801_Y receives the baseband signal (OFDM signal) 304_Y as input and performs Fourier transform and parallel serial conversion processing to obtain a baseband signal 1802_Y after signal processing.

  FIG. 19 in which the same reference numerals are assigned to corresponding parts to FIG. 5 shows the detailed configuration of the signal processing unit 1803. The signal processing unit 1803 has the same configuration as the signal processing unit 309 in FIG. 5 except that it includes reverse rearrangement units 1901_A and 1901_B, rearrangement units 1903_A and 1903_B, and reverse rearrangement units 1905_A and 1905_B. Incidentally, the signal processing unit 1803 actually receives the channel fluctuation signals 501_A, 501_B, 502_A, 502_B, and the baseband signals 503_X, 503_Y in order to absorb the delay of the time required for iterative decoding, as in FIG. Although a storage unit is provided for storage, this storage unit is omitted in FIG. 19 in order to simplify the drawing.

  It should be noted that, of course, the decoding units 508_A and 508_B incorporate a turbo code deinterleaver, and the rearrangement pattern of the deinterleaver is the decoding unit 508_A and the decoding unit 508_B. This is the same point. Therefore, in some cases, the decoding unit can be shared to be one, and the modulation signal A and the modulation signal B can be decoded by one decoding unit. In this way, the circuit scale can be reduced.

  The reverse rearrangement unit 1901_A receives the estimated baseband signal 505_A of the modulated signal A, and performs a rearrangement process opposite to the rearrangement in FIG. 17A to return the signal order to the original order, An estimated baseband signal 1902_A of the modulated signal A after reverse rearrangement is output.

  Similarly, the reverse rearrangement unit 1901_B receives the estimated baseband signal 505_B of the modulated signal B, and performs a rearrangement process opposite to the rearrangement in FIG. 17B, thereby changing the signal order to the original order. Then, the estimated baseband signal 1902_B of the modulated signal B after reverse rearrangement is output.

  The reverse rearrangement unit 1905_A receives the signals 512_A, 513_A, 503_X, and 503_Y, and performs a rearrangement process that is the reverse of the rearrangement in FIG. 17A, thereby returning the signal order to the original order. The rearranged signals 512_A ′, 513_A ′, 503_X ′, and 503_Y ′ are output.

  Similarly, the reverse rearrangement unit 1905_B receives the signals 512_B, 513_B, 503_X, and 503_Y, and performs the rearrangement process opposite to the rearrangement in FIG. 17B, thereby changing the signal order to the original order. The signals 512_B ′, 513_B ′, 503_X ′, and 503_Y ′ after the return and reverse rearrangement are output.

  By the reverse rearrangement described above, the signals are rearranged in an order that can be decoded.

  The rearrangement unit 1903_A receives the decoded data 509_A of the modulated signal A and performs rearrangement similar to that in FIG. As a result, the arrangement order of the signals input to the signal point reduction units 510_B and 511_B becomes the same, so that correct signal point reduction processing is possible.

  Similarly, rearrangement section 1903_B receives data 509_B after decoding modulated signal B as input, and performs rearrangement similar to that in FIG. As a result, the arrangement order of the signals input to the signal point reduction units 510_A and 511_A is the same, which enables correct signal point reduction processing.

  FIG. 20 shows an image of effects obtained by making the modulation signal A rearrangement and reverse rearrangement methods different from the modulation signal B rearrangement and reverse rearrangement methods.

  For example, as shown in FIG. 20A, it is assumed that an error occurs in a burst manner in the k−1th decoding in the modulation signal A (generally an error occurs in a burst manner). However, since the rearrangement of the modulation signal A and the modulation signal B is different, when signal point reduction and reverse rearrangement are performed in the decoding of the kth modulation signal B, as shown in FIG. In addition, the signal point reduction error does not occur in bursts but occurs discretely. Incidentally, unlike the present embodiment, when the modulation signal A rearrangement and reverse rearrangement methods are the same as the modulation signal B rearrangement and reverse rearrangement methods, the signal point reduction error is It occurs in bursts.

  In the present embodiment, decoding is performed in a state where signal point reduction errors occur discretely, so compared with a case where decoding is performed in a state where signal point reduction errors occur in bursts. Thus, the error rate characteristic of the decoded data is improved. Further, when viewed from another viewpoint, it is possible to reduce the number of iterations until the limit performance is obtained.

  As described above, according to the present embodiment, a plurality of turbo encoders (1502_A, 1502_B) provided in each antenna branch, each including an interleaver having the same interleave pattern, and turbo encoders (1502_A, 1502_B). ) And modulation units (1506_A, 1508_A, 1510_A, 1506_B, 1508_B, 1510_B) that modulate the encoded data obtained by (1)) and codes obtained by the respective turbo encoders (1502_A, 1502_B) And a plurality of rearrangement units (1504_A, 1504_B) for rearranging the encoded data or the encoded data after modulation in different rearrangement patterns.

  As a result, the rearrangers (1504_A, 1504_B) change the order of the encoded data or the modulation symbols of the modulated signals transmitted from the respective antennas between the antenna branches (modulated signals). Signal point reduction errors at (510_A, 511_A, 510_B, 511_B) occur discretely. As a result, the error rate characteristics of the digital data finally obtained by the decoding units (508_A, 508_B) are improved. Further, since the interleave patterns of the interleavers built in the turbo encoders (1502_A, 1502_B) are the same, the error rate characteristics can be improved without complicating the configuration of the decoding units (508_A, 508_B). Become.

  In the present embodiment, as shown in FIG. 17, a case has been described in which a rearrangement method is used in which rearrangement is performed in the frequency axis direction and then the time axis direction is changed, but the present invention is not limited to this. First, as shown in FIG. 21, the rearrangement method in which the rearrangement is performed in the time axis direction and then the transition is made in the frequency axis direction, and the rearrangement method is performed in both the time axis direction and the frequency axis direction as shown in FIG. Even if is used, the same effect can be obtained. Incidentally, as shown in FIG. 17, when a rearrangement method is used in which rearrangement is performed in the frequency axis direction and then the time axis direction is changed, the transition in the time axis direction is advanced in time order in FIG. This is not the only one. Similarly, as shown in FIG. 21, when a rearrangement method is used in which rearrangement is performed in the time axis direction and then the frequency axis direction is changed, in FIG. 21, the transition in the frequency axis direction is advanced in order of frequency. However, it is not limited to this.

  In addition, as a method of making the rearrangement different between the modulated signals, for example, the following method (i), (ii), or (iii) is preferably used.

(I) Method for Differentiating Data Arrangement of Symbols of Each Modulation Signal A specific example of this method is shown in FIG. In the modulation signal A, as shown in FIG. 23A, by rearranging the data arranged in the order of data 1, data 2,..., Data 200 before rearrangement, for example, every fifth data,
Data 1, data 6, ... data 196,
Data 2, data 7, ... data 197,
Data 3, data 8, ... data 198,
Data 4, data 9, ... data 199,
Data 5, data 10,... Data 200
In order. On the other hand, in the modulation signal B, as shown in FIG. 23B, the data arranged in the order of data 1, data 2,... ,
Data 1, data 9, ... data 193,
Data 2, data 10, ... data 194,
Data 3, data 11, ... data 195,
Data 4, data 12, ... data 196,
Data 5, data 13, ... data 197,
Data 6, data 14, ... data 198,
Data 7, data 15, ... data 199,
Data 8, data 16, ... data 200
In order. In this way, by making the data arrangement different between the modulation signal A and the modulation signal B, the data arrangement constituting the symbols of each modulation signal can be made different.

(Ii) A method in which symbols and data are arranged in the same manner among modulated signals, but the symbols and data are arranged differently when symbols and data are arranged in the frequency direction and time direction of the subcarrier. An example is shown in FIG. As shown in FIG. 24 (a), by interleaving the data that has been aligned with data 1, data 2,..., Data 200 before the rearrangement, for example, every five data are rearranged.
Data 1, data 6, ... data 196,
Data 2, data 7, ... data 197,
Data 3, data 8, ... data 198,
Data 4, data 9, ... data 199,
Data 5, data 10,... Data 200
Sort by. This process is performed for each of the modulation signals A and B. That is, the arrangement order between the modulated signals at this time is the same. Then, as shown in FIGS. 24B and 24C, the arrangement patterns of the modulated signals A and B on the subcarriers are made different. FIGS. 24B and 24C show the case where the number of subcarriers of the OFDM signal is 200. With respect to the frequency axis, the modulation signal A is
Data 1, data 6, ... data 196,
Data 2, data 7, ... data 197,
Data 3, data 8, ... data 198,
Data 4, data 9, ... data 199,
Data 5, data 10,... Data 200
To line up. On the other hand, the modulation signal B is offset by 5 carriers with respect to the arrangement of the modulation signal A, and data 185, data 190, data 195, data 200, data 1, data 6,. , Aligned with data 180. Such an operation may be performed on the time axis. In this way, even when one modulation signal is offset from the other modulation signal by several carriers or by a certain time, the interleaving can be made different between the modulation signals. Further, for example, the modulation signal A is arranged in the direction of the carrier 1 to 200, and the modulation signal B is arranged in the direction of the carrier 200 to 1, so that the modulation signals are arranged in the reverse direction on the frequency axis and the time axis. Also good.

(Iii) A method of using the above methods (i) and (ii) in combination

  Further, in addition to the regular rearrangement method as described above, a (pseudo) random rearrangement method may be used.

  That is, in the present invention, the different rearrangement between the modulation signals does not only indicate the case where the arrangement of symbols and data itself is different, but the arrangement of symbols and data in the frequency direction and / or the time direction. This includes making the arrangements themselves different.

  Here, interleave and rearrangement in symbol units have been described as examples. However, the present invention is not limited to this, and the same effect can be obtained by performing interleaving and rearrangement in bit units.

  In this embodiment, the case of a multi-antenna system having two transmission antennas and two reception antennas has been described. However, the present invention is not limited to this, and the number of transmission antennas is two or more and the number of reception antennas is two. As described above, the present invention can be widely applied when the transmission modulation signal is 2 or more.

  Furthermore, in the present embodiment, the case of the single carrier method has been described as an example. However, the present invention is not limited to this, and even when applied to a spread spectrum communication method or an OFDM method, the basic configuration similar to that described above is used. The same effect can be obtained.

  The present invention is suitable for application to a multi-antenna communication system in which high-speed data communication is performed using OFDM-MIMO (Multiple-Input Multiple-Output) technology or the like.

The block diagram which shows the structure of the multi-antenna transmission apparatus which concerns on Embodiment 1 of this invention. The figure which shows the example of a frame structure of the baseband signal of the modulation signals A and B FIG. 2 is a block diagram showing an overall configuration of a multi-antenna reception apparatus according to Embodiment 1 The figure which shows the relationship between the transmission / reception apparatuses in this Embodiment Block diagram showing the configuration of the signal processor The figure which shows the candidate signal point and receiving point of the multiplexed modulated signal A and the modulated signal B Diagram showing reduced candidate signal points and reception points Block diagram showing the configuration of the soft output section The block diagram which shows the structure of the soft decision part at the time of iterative decoding Diagram showing candidate signal points and received signal points Diagram showing reduced candidate signal points and provisionally determined signal points Block diagram showing the configuration of the soft output section Diagram showing reduced candidate signal points, reception points, and provisionally determined signal points The block diagram which shows the structure of the soft decision part at the time of iterative decoding Block diagram showing a configuration of a multi-antenna transmission apparatus according to a second embodiment Block diagram showing the configuration of a turbo encoder The figure which shows the rearrangement example about the modulation signals A and B FIG. 2 is a block diagram showing an overall configuration of a multi-antenna reception apparatus according to a second embodiment Block diagram showing the configuration of the signal processor Figure showing error propagation status by rearrangement The figure which shows the rearrangement example about the modulation signals A and B The figure which shows the rearrangement example about the modulation signals A and B The figure which shows the rearrangement example about the modulation signals A and B The figure which shows the rearrangement example about the modulation signals A and B The figure which shows schematic structure of a general multi-antenna communication system

Explanation of symbols

100, 1500 Multi-antenna transmission apparatus 300, 1800 Multi-antenna reception apparatus 309, 1803 Signal processing unit 504 Separation unit 510_A, 511_A, 510_B, 511_B Signal point reduction unit 506_A, 506_B Soft output unit 508_A, 508_B Decoding unit 801 Soft during iterative decoding Determining unit 802 Initial decoding soft decision unit 901_X, 901_Y Squared Euclidean distance calculation unit between received signal point and candidate signal point 903_X, 903_Y Squared Euclidean distance calculation unit between temporary decision signal point and candidate signal point 905, 1105 Addition Unit 1101_X, 1101_Y square Euclidean distance calculation unit between received signal point and provisionally determined signal point 1103_X, 1103_Y division unit 1502_A, 1502_B turbo encoder 1504_A, 1504_B rearrangement unit

Claims (4)

A multi-antenna receiving apparatus that receives a plurality of modulated signals transmitted simultaneously from a plurality of antennas by a plurality of antennas and restores a data sequence corresponding to each of the plurality of modulated signals from a received signal,
A determination unit that determines the modulation signal based on a signal point distance between a plurality of candidate signal points for a signal obtained by multiplexing the plurality of modulation signals and a signal point of the reception signal;
Using the determination result obtained by the determination unit, a decoding unit for obtaining digital data of the modulated signal;
Recursively using the digital data obtained by the decoding unit, a signal point reduction unit for reducing the number of candidate signal points used in the determination unit,
Comprising
The determination unit includes a first signal point distance between each candidate signal point reduced by the signal point reduction unit and a signal point of the received signal, and each candidate signal point reduced by the signal point reduction unit. A multi-antenna receiving apparatus that determines the modulated signal based on a second signal point distance to a provisionally determined signal point that is provisionally determined by recursively using digital data obtained by the decoding unit. A multi-antenna receiving apparatus that receives a plurality of modulated signals transmitted simultaneously from a plurality of antennas by a plurality of antennas and restores a data sequence corresponding to each of the plurality of modulated signals from a received signal,
A determination unit that determines the modulation signal based on a signal point distance between a plurality of candidate signal points for a signal obtained by multiplexing the plurality of modulation signals and a signal point of the reception signal;
Using the determination result obtained by the determination unit, a decoding unit for obtaining digital data of the modulated signal;
Recursively using the digital data obtained by the decoding unit, a signal point reduction unit for reducing the number of candidate signal points used in the determination unit,
Comprising
The determination unit recursively uses the first signal point distance between each candidate signal point reduced by the signal point reduction unit and the signal point of the reception signal, and the digital data obtained by the decoding unit. A multi-antenna reception apparatus that determines the modulation signal based on a provisionally determined signal point temporarily determined and a second signal point distance between the signal point of the received signal. A plurality of turbo encoders provided in each antenna branch, each including an interleaver of the same interleave pattern;
A modulator for modulating the encoded data obtained by the turbo encoder;
A plurality of rearrangement units provided in each antenna branch, for rearranging the encoded data obtained by each turbo encoder or each encoded data after modulation according to a different rearrangement pattern;
A multi-antenna transmission apparatus comprising: A determination unit that determines the modulation signal based on a signal point distance between a plurality of candidate signal points for a reception signal in which a plurality of modulation signals are spatially multiplexed and a signal point of the reception signal, and the determination unit Using the obtained determination result, a decoding unit that obtains digital data of the modulation signal, and the candidate signal used in the determination unit by recursively using digital data other than the self-modulation signal obtained by the decoding unit A multi-antenna reception device having a signal point reduction unit for reducing the number of points;
A plurality of turbo encoders provided in each antenna branch, each including an interleaver of the same interleave pattern, a modulation unit that modulates encoded data obtained by the turbo encoder, and provided in each antenna branch, A multi-antenna transmission apparatus comprising: a plurality of rearrangement units that rearrange the encoded data obtained by the turbo encoder or each encoded data after modulation according to different different rearrangement patterns;
A multi-antenna communication system comprising:

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