JP2009171155A - Multi-antenna transmission method, and multi-antenna transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain precoding capable of raising receiving quality by a comparatively small operation amount. <P>SOLUTION: A plurality of models for precoding are prepared beforehand, one of the plurality of prepared models for precoding is selected based on feedback information from a communication partner, amplitudes and phases of baseband signals for each stream are controlled so as to adapt to the selected model for precoding (namely, the precoding is performed so as to adapt to the model for precoding), and the baseband signals for each stream after the precoding are transmitted from different antennas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multi-antenna transmission method and a multi-antenna transmission apparatus capable of controlling a modulation scheme of a signal transmitted from each antenna for each antenna, as represented by a spatial-multiplex MIMO (Multiple-Input Multiple-Output) system.

  Conventionally, in multi-antenna communication typified by MIMO communication, data transmission speed is increased by modulating a plurality of series of transmission data and transmitting each modulated signal simultaneously from different antennas.

  MIMO communication will be briefly described with reference to FIGS. 17 and 18. FIG. 17 shows a relationship between transmitting and receiving antennas when a transmitting apparatus (for example, a base station) has two transmitting antennas AN1 and AN2 and a receiving apparatus (for example, a terminal) has two receiving antennas AN3 and AN4. It is. FIG. 18 shows a frame configuration on the time axis of a modulated signal (referred to as modulated signal A) transmitted from the transmitting antenna AN1 and a modulated signal (referred to as modulated signal B) transmitted from the transmitted antenna AN2. .

  From the transmission antenna AN1, data symbols 2 and 3 are transmitted as the modulated signal A following the known symbol 1 for estimating the channel fluctuation. Similarly, data symbols 5 and 6 are transmitted from the transmission antenna AN2 as a modulated signal B following the known symbol 4 for estimating the channel fluctuation. The modulated signal A and the modulated signal B are transmitted from different antennas AN1 and AN2 at the same time using the same frequency.

On the receiving side, using the known symbols 1 and 4 received by the antennas AN3 and AN4, channel fluctuation values h ₁₁ (t), h ₁₂ (t), h ₂₁ between the respective antennas of each modulated signal at time t. (T) and h ₂₂ (t) are estimated. Here, at time t, the received signal R ₁ (t) received by the antenna AN3, the received signal R ₂ (i) received by the antenna AN4, and the modulated signal T _a (t) transmitted from the antenna AN1 and The relationship with the modulation signal T _b (t) transmitted from the antenna AN2 is expressed by the following equation using channel fluctuation values h ₁₁ (t), h ₁₂ (t), h ₂₁ (t), and h ₂₂ (t). Can be expressed as

  By the way, there are a line-of-sight environment (LOS) and a non-line-of-sight environment (NLOS) as radio wave propagation environments between transmitting and receiving antennas. The line-of-sight environment is an environment where a direct wave component exists, and the non-line-of-sight environment is an environment where no direct wave component exists.

なお、式（２）において、ｎ_１、ｎ_２は受信機雑音を示す。式（２）では、時間のパラメータｔは省略して表した。 Here, in the line-of-sight (LOS) environment, the channel variation matrix in the equation (1) is the direct wave component channel elements h _{11, d} , h _{12, d} , h _{21, d} , h _{22, d} and the scattered wave component. Channel elements h _{11, s} , h _{12, s} , h _{21, s} , h _{22, and s} can be considered separately. Therefore, in the LOS environment, the expression (1) can be expressed as the following expression.

In Equation (2), n ₁ and n ₂ indicate receiver noise. In the equation (2), the time parameter t is omitted.

  It is known that, when a direct wave channel element falls into a steady state, even if the received electric field intensity is the same, the channel component of the direct wave exhibits completely different reception qualities depending on the state (see, for example, Non-Patent Document 1). Even in a LOS environment, particularly in an environment in which direct waves are dominant, there may be cases where good error rate characteristics (hereinafter sometimes referred to as reception quality) cannot be obtained even if the reception field strength is sufficient. it is conceivable that. This is because even if the reception electric field strength is sufficient, the reception quality may be deteriorated depending on the state of the direct wave matrix of Equation (2).

  On the other hand, there is no direct wave in the NLOS environment. In the NLOS environment, as shown in Non-Patent Document 2, it is possible to obtain a spatial diversity gain by using MLD (Maximum Likelihood Detection).

  From the above, it can be seen that a technique for improving the reception quality in the LOS environment is important in the multi-antenna communication.

Conventionally, there is precoding as one method for improving reception quality. For example, Non-Patent Document 3 describes a technique for improving reception quality in spatial multiplexing MIMO communication by precoding a transmission signal based on a minimum Euclidean distance in a transmitter.
“Analysis of MIMO system in rice fading” The Institute of Electronics, Information and Communication Engineers, IEICE Tech. 1-6, July 2003 “Multiple-antenna diversity techniques for transmission over fading channels” IEEE WCNC 1999, pp.1038-1042, Sep. 1999. “Optimal minimum distance-based precoder for MIMO spatial multiplexing systems” IEEE Transactions on Signal Processing, pp.617-627, vol.52, no.3, March 2004

  However, when the technique described in Non-Patent Document 3 is used, there is a drawback that the amount of calculation required to search for the minimum Euclidean distance becomes enormous, and the circuit scale increases accordingly.

  The present invention has been made in consideration of such points, and provides a multi-antenna transmission method and a multi-antenna transmission apparatus capable of realizing precoding capable of improving reception quality with a relatively small amount of calculation.

  One aspect of the multi-antenna transmission method of the present invention includes a step of determining a modulation scheme of a modulation signal transmitted from each antenna based on feedback information from a communication partner station, and a plurality of precoding models prepared in advance. A step of selecting a precoding model corresponding to a combination of modulation schemes of modulation signals transmitted from the antennas, and a step of performing precoding with the precoding model as a target.

  One aspect of the multi-antenna transmission method of the present invention further includes a step of determining whether it is a line-of-sight environment or a non-line-of-sight environment based on feedback information from the communication partner station. The precoding is not performed.

  One aspect of the multi-antenna transmission apparatus of the present invention is a multi-antenna transmission apparatus capable of controlling a modulation scheme of a signal transmitted from each antenna for each antenna, the receiving antenna of the communication partner station, each of the transmitting antennas, A plurality of precoding models corresponding to combinations of receiving means for receiving the channel fluctuation value between the communication partner stations as feedback information and modulation schemes transmitted from the respective antennas are stored, and the stored plurality of precoding models are stored. One precoding model is selected from the coding model based on the feedback information, and phase / amplitude control means for performing precoding processing using the selected precoding model is employed.

  According to the present invention, since precoding that does not require computation for searching for the minimum Euclidean distance can be realized, reception quality can be improved with a relatively small amount of computation.

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

(Embodiment 1)
(1) Configuration FIG. 1 shows a configuration example of a multi-antenna transmission apparatus according to an embodiment of the present invention. In the case of this embodiment, multi-antenna transmission apparatus 100 is provided in a base station. Therefore, in the following description, the multi-antenna transmission apparatus 100 may be referred to as the base station 100.

  The encoding unit 102_A receives the data 101_A of the stream A and the frame configuration signal 121, and encodes the data 101_A based on the encoding method information included in the frame configuration signal 121, thereby obtaining encoded data 103_A. .

  The mapping unit 105_A receives the encoded data 103_A and the frame configuration signal 121 and maps the encoded data 103_A based on the modulation scheme information included in the frame configuration signal 121, thereby obtaining a mapped signal 106_A.

  The phase / amplitude control unit 107_A receives the mapped signal 106_A and the frame configuration signal 121, and controls the phase and amplitude of the mapped signal 106_A based on the precoding information included in the frame configuration signal 121. Thus, the signal 108_A after the phase / amplitude control is output.

  The band limiting unit 109_A obtains a band-limited signal 110_A by band-limiting the signal 108_A after the phase / amplitude control. The radio unit 111_A obtains a transmission signal 112_A by performing predetermined radio processing such as quadrature modulation, frequency conversion, and amplification on the band-limited signal 110_A. The transmission signal 112_A is radiated as a radio wave from the antenna 113_A.

  The multi-antenna transmission apparatus 100 performs the same processing as the above-described stream 101 data 101_A on the stream 101 data 101_B. That is, the encoding unit 102_B obtains the encoded data 103_B based on the information on the encoding scheme included in the frame configuration signal 121, and the mapping unit 105_B obtains the post-mapping based on the modulation scheme information included in the frame configuration signal 121. A signal 106_B is obtained. Next, the phase / amplitude control unit 107_B obtains the signal 108_B after the phase / amplitude control based on the precoding information included in the frame configuration signal 121. Next, a band-limited signal 110_B is obtained by the band-limiting unit 109_B, a transmission signal 112_B is obtained by the radio unit 111_B, and this is supplied to the antenna 113_B.

  Here, in multi-antenna transmission apparatus 100, the processing of encoding section 102_A, mapping section 105_A and phase / amplitude control section 107_A for processing stream A data 101_A, and processing of stream B data 101_B are performed. The processing of the encoding unit 102_B, the mapping unit 105_B, and the phase / amplitude control unit 107_B can be controlled independently. That is, the encoding method, modulation method, and phase / amplitude of the transmission signal 112_A transmitted from the antenna 113_A and the transmission signal 112_B transmitted from the antenna 113_B can be controlled independently between the antennas.

  In addition, multi-antenna transmission apparatus 100 inputs reception signal 115 received by antenna 114 to reception unit 116. The receiving unit 116 obtains received data 117 by frequency-converting, orthogonally demodulating, detecting and decoding the received signal 115.

  Transmission method determining section 118 receives received data 117, extracts feedback information included in received data 117, determines a modulation scheme, a coding scheme, and a precoding scheme based on the extracted feedback information, and determines the determined scheme Is transmitted to the frame configuration signal generation unit 120 as transmission method determination information 119.

  The frame configuration signal generation unit 120 determines a transmission frame configuration based on the transmission method determination information 119, and outputs a frame configuration signal 121 indicating the determined transmission frame configuration. This frame configuration signal 121 includes coding scheme information, modulation scheme information, and precoding information.

  FIG. 2 illustrates an example of a detailed configuration of the mapping units 105_A and 105_B and the phase / amplitude control units 107_A and 107_B. In FIG. 2, the configuration of the mapping unit 105_A and the phase / amplitude control unit 107_A is shown, but the configuration of the mapping unit 105_B and the phase / amplitude control unit 107_B is the same.

  The mapping unit 105_A includes a BPSK modulation unit 201, a QPSK modulation unit 203, and a selection unit 205. The encoded data 103_A is input to the BPSK modulation unit 201 and the QPSK modulation unit 203.

  When the frame configuration signal 121 indicates BPSK modulation, the BPSK modulation unit 201 operates, the BPSK modulation unit 201 outputs the BPSK modulation signal 202, the selection unit 205 selects the BPSK modulation signal 202, and the BPSK modulation signal 202 Is output as the mapped signal 106_A.

  On the other hand, when the frame configuration signal 121 indicates QPSK modulation, the QPSK modulation unit 203 operates, the QPSK modulation unit 203 outputs the QPSK modulation signal 204, the selection unit 205 selects the QPSK modulation signal 204, and the QPSK modulation is performed. The signal 204 is output as the mapped signal 106_A.

  The phase / amplitude control unit 107_A includes a model selection unit 206 and a phase / amplitude control circuit 208.

  The model selection unit 206 stores a plurality of precoding models corresponding to combinations of modulation schemes transmitted from the antennas 113_A and 113_B. The model selection unit 206 receives the frame configuration signal 121, selects a target model in the phase / amplitude control based on the modulation scheme information included in the frame configuration signal 121, and sets the selected target model information 207 as the phase. Output to the amplitude control circuit 208. Specifically, model selection section 206 outputs target model information 207 corresponding to the combination of the modulation scheme of the signal transmitted from antenna 113_A and the modulation scheme of the signal transmitted from antenna 113_B.

Although not shown, the model selection unit 206 receives, for example, channel fluctuation values h ₁₁ (t), h ₁₂ (t), h in Equation (1) as feedback information from the communication partner station (for example, terminal). ₂₁ (t) and h ₂₂ (t) are input. The model selection unit 206 forms target model information 207 using the input channel fluctuation values h ₁₁ (t), h ₁₂ (t), h ₂₁ (t), and h ₂₂ (t).

  The phase / amplitude control circuit 208 controls the phase and amplitude of the mapped signal 106_A based on the target model information 207 to obtain a signal 108_A after the phase / amplitude control. For example, when a QPSK modulated signal as shown in FIG. 3A is input as the mapped signal 106_A, the phase / amplitude control circuit 208 controls the phase and amplitude of the input signal, thereby controlling the phase / amplitude control. As the signal 108_A, a signal having a signal point arrangement as shown in FIG. 3B, for example, is output.

  FIG. 4 shows a configuration of a receiving apparatus that receives a signal transmitted from multi-antenna transmitting apparatus (base station) 100. In the case of this embodiment, receiving apparatus 300 is provided in a terminal. Therefore, in the following description, the receiving device 300 may be referred to as a terminal 300.

  Reception signals 302_X and 302_Y received by the antennas 301_X and 301_Y are input to the radio units 303_X and 303_Y. The radio units 303_X and 303_Y obtain baseband signals 304_X and 304_Y by performing processing such as frequency conversion and orthogonal demodulation on the received signals 302_X and 302_Y.

Channel fluctuation estimation section 305A of stream A receives baseband signal 304_X and extracts signals of pilot symbol 402A and channel estimation symbol 405A (FIG. 5) transmitted from antenna 113_A. Further, the channel variation estimation unit 305A of the stream A, based on the extracted signal variation, the antenna variation 113_A and the antenna 301_X corresponding to the channel variation of the stream A (that is, the channel variation value h ₁₁ (t) in Expression (1)). And the estimation result is output as a channel fluctuation estimation signal 306_A.

Channel fluctuation estimation section 305_B of stream B receives baseband signal 304_X and extracts signals of pilot symbol 402B and channel estimation symbol 405B (FIG. 5) transmitted from antenna 113_B. Further, the channel fluctuation estimation unit 305_B of the stream B, based on the extracted fluctuation of the signal, corresponds to the channel fluctuation of the stream B (that is, the channel fluctuation value h ₂₁ (t) in the equation (1)). The channel fluctuation between the two is estimated, and the estimation result is output as a channel fluctuation estimation signal 306_B.

Similarly, the channel fluctuation estimation unit 307_A of the stream A receives the baseband signal 304_Y and extracts the pilot symbol 402A and the channel estimation symbol 405A (FIG. 5) signals transmitted from the antenna 113_A. Further, the channel fluctuation estimation unit 307_A of the stream A is based on the extracted signal fluctuation between the antenna 113_A and the antenna 301_Y corresponding to the channel fluctuation of the stream A (that is, the channel fluctuation value h ₁₂ (t) of Expression (1)). Channel fluctuation) and the estimation result is output as a channel fluctuation estimation signal 308_A.

Channel fluctuation estimation section 307_B of stream B receives baseband signal 304_Y and extracts signals of pilot symbol 402B and channel estimation symbol 405B (FIG. 5) transmitted from antenna 113_B. Further, the channel fluctuation estimation unit 307_B of the stream B, based on the fluctuation of the extracted signal, the antenna 113_B and the antenna 301_Y corresponding to the channel fluctuation of the stream B (that is, the channel fluctuation value h ₂₂ (t) of Expression (1)). Channel fluctuation between the two) is estimated, and the estimation result is output as a channel fluctuation estimation signal 308_B.

  The signal processing unit 309 receives the baseband signals 304_X and 304_Y and the channel fluctuation estimation signals 306_A, 306_B, 308_A, and 308_B, and performs the same calculation as Expression (1) to estimate the signals of the stream A and the stream B . The signal processing unit 309 obtains stream A reception data 310_A and stream B reception data 310_B by demodulating the estimated stream A and stream B signals.

  Feedback information generation section 311 receives channel fluctuation estimation signals 306_A, 306_B, 308_A, and 308_B, and generates feedback information 312 for feeding back each channel fluctuation estimation value to multi-antenna transmission apparatus (base station) 100.

  The transmission unit 314 receives the feedback information 312 and the transmission data 313 and generates a transmission signal 315 by performing processing such as encoding, modulation, quadrature modulation, frequency conversion, and amplification on these. The transmission signal 315 is output from the antenna 316 as a radio wave.

  FIG. 5 shows an example of a transmission frame configuration of base station 100 and terminal 300. In the example of FIG. 5, base station 100 transmits pilot symbol 402A, channel estimation symbol 405A, and data symbol 406A as stream A (modulated signal A) from antenna 113_A. Also, base station 100 transmits control information symbol 401, pilot symbol 402B, transmission method notification symbol 404, channel estimation symbol 405B, and data symbol 406B as stream B (modulated signal B) from antenna 113_B. Here, symbols transmitted from the antennas 113_A and 113_B at the same time are transmitted in the same frequency band.

  The control information symbol 401 is a symbol for the base station to control terminal communication, and is a symbol for transmitting control information for establishing communication such as a frequency channel. Pilot symbols 402 </ b> A and 402 </ b> B are, for example, symbols known between transmitters and receivers, and terminal 300 estimates channel fluctuation using these symbols and creates feedback information 403 to be transmitted to base station 100.

  Transmission method notification symbol 404 is a symbol for notifying terminal 300 of information such as the coding scheme, modulation scheme, and precoding scheme of data symbols (symbols for transmitting data) 406A and 406B transmitted by base station 100. It is.

Channel estimation symbols 405A and 405B are symbols for estimating channel fluctuations necessary for terminal 300 to realize detection of a received signal transmitted by MIMO. That is, it is a symbol for estimating the channel fluctuation values h ₁₁ (t), h ₁₂ (t), h ₂₁ (t), and h ₂₂ (t) in the equation (1), and is known for example between the transceivers. Composed of symbols.

  Data symbols 406A and 406B are symbols for transmitting data of stream A and stream B. Data symbols 406A and 406B are precoded as described above.

(2) Precoding (2-1) Selection of Precoding Model Next, precoding processing in the present embodiment will be described. In the following, in order to simplify the description, the description will be made only when the selectable modulation schemes are BPSK and QPSK.

  FIG. 6 shows a precoding procedure in the present embodiment.

  When the base station 100 receives the feedback information from the terminal 300 in step ST1, in step ST2, the transmission method determining unit 118 determines whether or not the LOS environment is based on the feedback information. Here, the LOS environment means an environment where a direct wave component exists in Equation (2), and the NLOS environment means an environment where no direct wave component exists in Equation (2).

  When determining that the LOS environment is established (ST2; YES), the base station 100 confirms or estimates received electric field strengths (received power) of the stream A and the stream B based on the feedback information in step ST3.

  Next, in step ST4, the base station 100 determines a combination of a modulation scheme applied to the stream A and a modulation scheme applied to the stream B based on the received electric field strength estimated in step ST3. That is, the base station 100 uses both QPSK as the modulation scheme for stream A and stream B, or both BPSK as the modulation scheme for stream A and stream B, or sets QPSK as the modulation scheme for stream A and stream B. Or BPSK as the modulation method for stream A and QPSK as the modulation method for stream B.

  Next, in step ST5, the base station 100 forms the baseband signal of the modulation scheme determined in step ST4 by the mapping units 105_A and 105_B.

  Next, in step ST6, the base station 100 combines the modulation schemes determined in step ST4 from among a plurality of precoding models by the model selection unit 206 (FIG. 2) of the phase / amplitude control units 107_A and 107_B. Select a precoding model corresponding to. Furthermore, base station 100 determines a precoding target model by applying feedback information (channel fluctuation value) from terminal 300 to the selected precoding model.

  Next, in step ST7, the base station 100 uses the phase / amplitude control circuit 208 (FIG. 2) of the phase / amplitude control units 107_A and 107_B so as to approach the target model for precoding determined in step ST6. Controls the phase and amplitude of the band signal.

  Next, in step ST8, base station 100 limits the band of the baseband signal after precoding (after phase / amplitude control), performs radio processing, and transmits the baseband signal.

  On the other hand, if the base station 100 determines in step ST2 that it is not the LOS environment (that is, the NLOS environment) (ST2; NO), it does not perform precoding.

  That is, if the base station 100 determines in step ST2 that it is not in the LOS environment, the base station 100 moves to step ST9. Further, the base station 100 determines whether the modulation schemes of the stream A and the stream B are both QPSK, or the modulation schemes of the stream A and the stream B are both BPSK. Then, after forming the baseband signal of the modulation scheme determined in step ST9 in step ST10, the base station 100 proceeds to the transmission process in step ST8 without performing precoding.

  Thus, in multi-antenna transmission apparatus (base station) 100 of the present embodiment, precoding is performed in the case of LOS environment, while precoding is performed in the case of not LOS environment (that is, NLOS environment). Absent.

  The precoding features of this embodiment include the following points.

  When the base station performs precoding, it performs precoding by controlling the phase and amplitude of each modulation signal based on feedback information from the terminal.

  ・ Set multiple models for precoding in advance.

  -One type of precoding prepared in advance is selected from the feedback information, and the phase and amplitude of the modulation signal are controlled so as to approach the selected precoding model.

  Specifically, based on the feedback information, first, a combination of modulation schemes is determined, and a precoding model corresponding to the combination of modulation schemes is selected. Then, the phase and amplitude are controlled using the selected precoding model as a target.

  In the example of FIG. 6, (stream A, stream B) is (QPSK, QPSK), (QPSK, BPSK), (BPSK, QPSK), (BPSK, BPSK) as precoding models in the case of the LOS environment. A precoding model is prepared for each combination.

  Incidentally, although the base station does not perform precoding in the NLOS environment, in other words, it can be said that a precoding model without precoding is prepared. That is, the base station first selects either a precoding model for performing precoding or a precoding model for which precoding is not performed, depending on whether the LOS environment or the NLOS environment is used. Next, in the case of the LOS environment, it can be said that the base station further selects one precoding model corresponding to a combination of modulation schemes from a plurality of precoding models.

  As described above, in the present embodiment, the base station does not perform precoding when it is determined to be an NLOS environment, and selects one of a plurality of precoding models when it is determined to be an LOS environment. A model is selected, and the phase and amplitude of the baseband signal are controlled using the selected precoding model as a target. Thereby, compared with the case where precoding is performed based on the minimum Euclidean distance as disclosed in Non-Patent Document 3, for example, the amount of calculation for performing precoding can be significantly reduced.

  Here, the process of finding the above-described precoding will be described. In general, in a spatial multiplexing MIMO system, in a NLOS environment, a spatial diversity gain can be obtained, so that the reception quality of data at the receiver is good. On the other hand, it is difficult to obtain a spatial diversity gain in the LOS environment.

  The inventors of the present invention pay attention to this point, and in the NLOS environment, even if precoding is performed, the improvement in data reception quality is considered to be small. That is, in the NLOS environment, since the data reception quality is good in the first place, it is difficult to further improve the data reception quality. On the other hand, in the LOS environment, the data reception quality is considered to be highly likely to be improved by precoding. That is, in the LOS environment, the space diversity gain cannot be obtained sufficiently, so there is room for improvement in data reception quality.

  From these considerations, precoding is not performed when it is determined to be an NLOS environment, and precoding is performed when it is determined to be an LOS environment, so that precoding is actually performed only when the effect of improving data reception quality is large. Added coding.

(2-2) Precoding Model Next, a specific example of the precoding model will be described. In the following, the precoding model (in other words, the target model for controlling the phase and amplitude) when the LOS environment is determined will be described in detail.

  FIG. 7 is a diagram for explaining precoding when the modulation scheme of stream A and stream B is determined to be QPSK and it is determined to be a LOS environment. FIG. 7A shows an example of the signal point arrangement of reception candidate signal points on the in-phase I-orthogonal Q plane when a QPSK modulation signal is transmitted as the modulation signal of stream A and stream B. It is. Incidentally, in order to simplify the description, FIG. 7 shows a case where the scattered wave component of Expression (2) does not exist.

In general, in the formula ^{_{(2), | h 11,}} d | 2 = | h 12, d | 2 and _{^{| h 21, d | 2 =}} | h 22, d | ^{likely 2} is established. In addition, the matrix of the direct wave component in Expression (2) is highly likely to be a regular matrix. Therefore, in the equation (2), the reception candidate signal point Rx ₁ and the reception candidate signal point Rx ₂ are likely to have the same value, and hence only the reception candidate signal point Rx ₁ will be discussed below.

FIG. 7A shows the arrangement of candidate signal points when | h _{11, d} | ² = | h _{12, d} | ² and θ _d = Arg (h _{11, d} / h _{12, d} ). ○ indicates the candidate signal point position when θ _d = 0 [°], and ● indicates the candidate signal point position when rotated from θ by θ _d .

FIG. 7B shows a graph when the horizontal axis is θ _d and the vertical axis is the square of the minimum Euclidean distance. From FIG. 7B, it can be seen that the square of the minimum Euclidean distance is the maximum when θ _d = 30 [°]. Therefore, precoding that satisfies θ _d = 30 [°] is desired.

By the way, there is a high possibility that | h _{11, d} | ² = | h _{12, d} | ² and | h _{21, d} | ² = | h _{22, d} | ² are satisfied. It cannot be said that it will be a good model. Therefore, as another model, | h _{11, d} | ² = 4 | h _{12, d} | ² and | h _{21, d} | ² = 4 | h _{22, d} | ² , or 4 | h _{11, d} | Consider the position of the reception candidate signal point on the in-phase I-quadrature Q plane when ² = | h _{12, d} | ² and 4 | h _{21, d} | ² = | h _{22, d} | ² . The state at that time is shown in FIG. In this case, when θ _d = 0 [°], the square of the minimum Euclidean distance is the maximum. Therefore, precoding that satisfies θ _d = 0 [°] is desired.

From the above, in the present embodiment, when the modulation method of stream A and stream B is determined as QPSK and it is determined as the LOS environment,
<1> As shown in FIG. 7A, | h _{11, d} | ² = | h _{12, d} | ² and θ _d = 30 [°]
<2> As shown in FIG. 8, | h _{11, d} | ² = 4 | h _{12, d} | ² or 4 | h _{11, d} | ² = | h _{12, d} | ² and θ _d = 0 [° ] Is selected, and control is performed so that the phase and amplitude of the baseband signal are selected.

  Thereby, since the minimum Euclidean distance between candidate signal points at the terminal can be increased, the data reception quality can be improved. According to the precoding method of the present embodiment, it is possible to eliminate the need for performing a complicated search such as searching for the minimum Euclidean distance and performing precoding accordingly, as in Non-cited Document 1. In other words, in the precoding method of the present embodiment, since a precoding model has already been determined, the search for the minimum Euclidean distance that requires enormous calculation is not performed, so the amount of calculation is greatly reduced. Can do.

  FIG. 9 is a diagram for explaining the precoding when the modulation scheme of the stream A and the stream B is determined as BPSK and it is determined as the LOS environment. Specifically, FIG. 9 illustrates an example of signal point arrangement of reception candidate signal points at the receiver when the BPSK modulation signal is transmitted as the modulation signal of stream A and stream B. It is shown above. Incidentally, FIG. 9 shows a case where the scattered wave component of Expression (2) does not exist in order to simplify the description.

FIG. 9 shows the arrangement of candidate signal points when | h _{11, d} | ² = | h _{12, d} | ² and θ _d = Arg (h _{11, d} / h _{12, d} ). ○ indicates the candidate signal point position when θ _d = 0 [°], and ● indicates the candidate signal point position when rotated from θ by θ _d . Here, when the minimum Euclidean distance is discussed regardless of the magnitudes of | h _{11, d} | ² and | h _{12, d} | ² , the minimum Euclidean distance may be maximized when θ _d = 90 [°]. it can. Therefore, precoding that satisfies θ _d = 90 [°] is desired. In this case, precoding may not involve amplitude control. However, transmission power may be controlled in order to ensure reception quality. At this time, the phase control in precoding is not affected.

From the above, in the present embodiment, when the modulation method of stream A and stream B is determined as BPSK and it is determined as the LOS environment,
<1> As shown in FIG. 9, a model with θ _d = 90 [°] is selected, and control is performed so that the phase of the baseband signal is selected.

  FIG. 10 is a diagram for explaining precoding when the receiver determines that the modulation scheme of stream A is BPSK, the modulation scheme of stream B is QPSK, and determines that the LOS environment is used. Further, FIG. 10 is also a diagram for explaining precoding when it is determined that the modulation scheme of stream A is QPSK, the modulation scheme of stream B is BPSK, and the LOS environment is determined in the receiver. . Specifically, FIG. 10 shows the signal point arrangement of the reception candidate signal points in the receiver when the BPSK modulation signal is transmitted as the stream A modulation signal and the QPSK modulation is transmitted as the stream B modulation signal. Is shown on the in-phase I-orthogonal Q plane. Further, FIG. 10 shows an example of signal point arrangement of reception candidate signal points in a receiver when a QPSK modulation signal is transmitted as a stream A modulation signal and a BPSK modulation signal is transmitted as a stream B modulation signal. Is shown on the in-phase I-orthogonal Q plane.

  In the present embodiment, from FIG. 10, the following two models are prepared in order to maximize the square of the minimum Euclidean distance.

<1> When stream A is the stream B in QPSK at _BPSK, | at ^{2, | h 11, d |} 2 = 2 | h 12, d | 2 and ^{_{| h 21, d | 2 =}} 2 | h 22, d Model <1 ′> with θ _d = 0 [°] If stream A is QPSK and stream B is BPSK, 2 | h _{11, d} | ² = | h _{12, d} | ² and 2 | h _{21, d} | ² = | H _{22, d} | ² and θ _d = 0 [°]

  When the receiver determines the modulation scheme for stream A as BPSK and the modulation scheme for stream B as QPSK, the receiver selects the model <1>. In addition, when the receiver determines the modulation scheme of stream A as QPSK and the modulation scheme of stream B as BPSK, the receiver selects the model <1 '>. And it controls so that it may become a model which selected the phase and amplitude of the baseband signal.

  Up to this point, in order to simplify the description, the description has been made only on the case where the selectable modulation schemes are BPSK and QPSK. However, for precoding in the LOS environment when 16 QAM can also be selected. An example of the model will be described.

  Here, a precoding model when one of the modulation schemes of stream A and stream B is 16QAM and the other is QPSK will be described. The precoding model in this case will be described in detail with reference to FIGS. 11A and 11B.

  From FIG. 11A, in order to maximize the square of the minimum Euclidean distance, the following two models are prepared.

<1> When stream A is the stream B in QPSK in _16QAM, | at ^{2, | h 11, d |} 2 = 5 | h 12, d | 2 and ^{_{| h 21, d | 2 =}} 5 | h 22, d Model <1 ′> with θ _d = 30 [°] When stream A is QPSK and stream B is 16QAM, 5 | h _{11, d} | ² = | h _{12, d} | ² and 5 | h _{21, d} | ² = | H _{22, d} | ² and θ _d = 30 [°]

  Alternatively, from FIG. 11B, the following two models are prepared in order to maximize the square of the minimum Euclidean distance.

<2> When stream A is 16QAM and stream B is QPSK, 16 | h _{11, d} | ² = 5 | h _{12, d} | ² and 16 | h _{21, d} | ² = 5 | h _{22, d} | ² When θ _d = 0 [°] model <2 ′> stream A is QPSK and stream B is 16QAM, 5 | h _{11, d} | ² = 16 | h _{12, d} | ² and 5 | h _{21, d} | ² = 16 | h22 _{, d} | ² , and model of _θd = 0 [°]

  When the receiving terminal determines that the modulation scheme for stream A is 16QAM and the modulation scheme for stream B is QPSK, the receiving terminal selects the model <1> or <2>. Further, when the receiving terminal determines that the modulation scheme for stream A is QPSK and the modulation scheme for stream B is 16QAM, the receiving terminal selects the model <1 '> or <2'>. And it controls so that it may become a model which selected the phase and amplitude of the baseband signal.

  Here, the case of a set of 16QAM and QPSK has been described, but precoding modeling can be similarly performed in the case of a set of 16QAM and BPSK.

(3) Reduction of feedback information Next, a method for reducing feedback information will be described in detail. For example, in the case of a 2 × 2 spatial multiplexing MIMO system, if the terminal 300 in FIG. 4 feeds back all the values of h ₁₁ , h ₁₂ , h ₂₁ , and h ₂₂ , the amount of feedback information becomes very large. As will be described in detail in Embodiment 2, when a multi-carrier scheme such as OFDM is used, if the above four values are fed back for each subcarrier, the amount of information to be fed back further increases. Considering this, reducing the feedback information is very important in securing the data transmission rate. Therefore, in the following, a method for reducing feedback information will be described in detail.

The phase difference between h ₁₁ and h ₁₂ is θ ₁ (−π radians <θ ₁ <π radians), the phase difference between h ₂₁ and h ₂₂ is θ ₂ (−π radians <θ ₂ <π radians), and φ = Θ ₂ −θ ₁ (−π radians <φ <π radians) is defined.

  In the present embodiment, φ is fed back, and it is determined that the LOS environment is close when φ = 0 radians.

Further, in this _embodiment, the ratio of _{h 11} and _{h 12} and R2 the ratio of _{R1, h 21} and _{h 22,} feeds back the R1 and R2.

  Then, if φ is close to 0 radians and R1≈R2, the base station 100 determines that the LOS environment is used and performs precoding. On the other hand, if the above conditions are not met, the base station 100 determines the NLOS environment and does not perform precoding. However, precoding may be performed even when the NLOS environment is determined.

In this way, by generating information degenerated from h ₁₁ , h ₁₂ , h ₂₁ , and h ₂₂ and performing precoding based on the information, precoding can be performed with less feedback information. As a result, it is possible to perform precoding on the downlink while suppressing a decrease in the data transmission rate on the uplink.

(4) Effects and Modifications As described above, according to the present embodiment, a plurality of precoding models are prepared in advance, and the prepared plurality of models are based on feedback information from a communication partner. Select one of the precoding models. Further, the amplitude and phase of the baseband signal for each stream are controlled so as to conform to the selected precoding model (that is, precoding is performed so as to conform to the precoding model), and after the precoding The baseband signal for each stream is transmitted from a different antenna.

  As a result, the reception quality of the communication partner can be improved by a simple process such as selecting a precoding model based on feedback information without performing an operation for searching for the minimum Euclidean distance based on feedback information. become. As a result, the processing for precoding can be reduced and the reception quality can be improved effectively.

  In addition, the base station does not perform precoding when it is determined as an NLOS environment, and performs precoding when it is determined as an LOS environment. For this reason, the base station actually performs precoding only when the effect of improving the reception quality of data is large, thereby further reducing the processing for precoding and effectively improving the reception quality. Can be improved.

  In the above-described embodiment, the base station mainly describes the case where precoding is not performed when it is determined to be an NLOS environment. However, precoding is also performed when it is determined to be an NLOS environment. It may be. Even in this case, the base station prepares a plurality of precoding models in advance, and selects one of the prepared precoding models based on feedback information from the communication partner. If the amplitude and phase of the baseband signal for each stream are controlled so as to be selected and adapted to the selected precoding model, the amount of calculation can be reduced as compared with the conventional case.

  In the above-described embodiment, the case where both the phase and the amplitude are controlled by the phase / amplitude control units 107_A and 107_B as shown in FIG. 1 is described, but the phase is controlled as shown in FIG. The portion for controlling the amplitude may be separated from the portion for controlling the amplitude.

  In FIG. 12, in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, a multi-antenna transmission apparatus (base station) 500 includes phase controllers 501_A and 501_B and power amplifiers (amplifiers) 502_A and 502_B. The frame configuration signal 121 is input to the phase controllers 501_A and 501_B and the power amplifiers (amplifiers) 502_A and 502_B. In the case of FIG. 12, it is assumed that the frame configuration signal 121 includes information on the selected precoding model, that is, target phase information and amplitude information.

  The phase control units 501_A and 501_B control only the phase of the mapped signals 106_A and 106_B. The amplitude control is performed by the power amplifiers 502_A and 502_B in the final stage. In this way, only the phase control is performed in the digital processing domain, and the amplitude control is performed in the analog signal domain, so that the dynamic range of the signal during the digital-analog conversion is reduced. There is a merit that the generation of the conversion error can be suppressed.

  Further, in the above-described embodiment, the base station has been described by taking the case where the number of transmission streams is 2, but the present invention is not limited to this, and when the number of transmission streams is 3 or more, pre-coding is performed in advance. Prepare multiple models, select one of the prepared precoding models based on the feedback information from the communication partner, and fit the selected precoding model Control the amplitude and phase of the baseband signal for each stream. If the base station performs precoding to match the precoding model and transmits the baseband signal for each stream after precoding from a different antenna, the processing for precoding is reduced. Thus, the reception quality can be improved effectively. The same applies to the case of Embodiment 2 described later.

  Also, the feedback information reduction method is not limited to the method described in the above embodiment, and other methods may be used.

  Furthermore, the configuration and method for reducing the precoding processing described in the above-described embodiment may be applied not only to the single carrier transmission method but also to the multicarrier transmission method. The configuration and method of the above-described embodiment are effective when applied to various transmission systems such as a spread spectrum communication system, OFDM system, SC-FDMA (Single Carrier Frequency Division Multiple Access) system, and the like.

  In the MIMO system according to the present embodiment, the modulation signal is transmitted from different antennas at the same frequency.

(Embodiment 2)
In this embodiment, a case will be described in detail where the method and configuration for reducing the precoding processing described in Embodiment 1 are applied to a multicarrier transmission scheme, particularly an OFDM scheme.

  In FIG. 13, in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, a multi-antenna transmission apparatus (base station) 600 includes serial / parallel converters (S / P) 601_A and 601_B, and an inverse Fourier transformer (ift). 603_A and 603_B.

  The serial / parallel converters 601_A and 601_B receive the signals 108_A and 108_B after the phase / amplitude control, and obtain the signals 602_A and 602_B after the serial / parallel conversion. The inverse Fourier transform units 603_A and 603_B receive the signals 602_A and 602_B after serial parallel, and obtain the signals 604_A and 604_B after inverse Fourier transform. The radio units 605_A and 605_B receive the signals 604_A and 604_B after the inverse Fourier transform, and perform predetermined radio processing such as frequency conversion and amplification on the signals 604_A and 604_B after the inverse Fourier transform, thereby transmitting the signal 606_A. , 606_B is obtained.

  FIG. 14, in which parts corresponding to those in FIG. 4 are assigned the same reference numerals, shows the configuration of a receiving apparatus (terminal) that receives a signal transmitted from multi-antenna transmitting apparatus (base station) 600.

  The receiving device (terminal) 700 inputs the baseband signals 304_X and 304_Y to the Fourier transform and parallel / serial converters 701_X and 701_Y. The Fourier transform and parallel serial conversion units 701_X and 701_Y perform Fourier transform processing and parallel serial conversion processing on the baseband signals 304_X and 304_Y to obtain signals 702_X and 702_Y after OFDM demodulation.

  FIG. 15, in which the same reference numerals are assigned to corresponding parts as in FIGS. 14 and 12, shows a configuration example of a multi-antenna transmission apparatus (base station) different from multi-antenna transmission apparatus (base station) 600 in FIG. A multi-antenna transmission apparatus 800 in FIG. 15 is configured by separating a part for controlling the phase and a part for controlling the amplitude, as described in FIG. Specifically, compared with the configuration of FIG. 14, phase control is performed by the phase control units 501_A and 501_B, and amplitude control is performed by the power amplifiers (amplifiers) 502_A and 502_B.

  By the way, in the case of a multicarrier transmission scheme such as OFDM, precoding is performed by performing phase control and amplitude control control of a baseband signal for each subcarrier. In the case of this embodiment, the same method as that of Embodiment 1 is mainly applied for precoding.

  However, the following methods can be considered as precoding specific to the multicarrier transmission scheme.

  (Method 1) All subcarriers are subjected to the same precoding. In this case, it is assumed that the modulation scheme is the same for each stream, and the target model for precoding is also the same for each stream.

  (Method 2) Different precoding is performed for each subcarrier. In this case, it is assumed that the modulation scheme is different for each subcarrier, and the target model for precoding is also different for each subcarrier.

  Each of the above (Method 1) and (Method 2) has the following characteristics.

  In (Method 1), the same precoding is applied to all subcarriers, and therefore the operation scale is small. On the other hand, the improvement in reception quality is reduced. In (Method 1), feedback information from the terminal can be reduced. For example, the terminal may obtain the feedback information described in Embodiment 1 for each subcarrier, calculate an average value thereof, and feed it back to the base station as a representative value.

  In (Method 2), since different precoding is performed for each subcarrier, the calculation scale is large, but the effect of improving the reception quality is large. Further, since it is necessary to notify the terminal of the precoding scheme for all subcarriers, the data transmission efficiency in the downlink is reduced. In addition, since the terminal needs to obtain feedback information for each subcarrier and feed back all or a part thereof, the data transmission efficiency on the uplink is reduced. However, the effect of improving the reception quality at the terminal is greater than that of (Method 1).

  As described above, (Method 1) and (Method 2) are effective in specific points, but it is difficult to achieve both improvement in reception quality, reduction in computation scale, and reduction in feedback information. is there.

  Therefore, in this embodiment, a precoding method in units of subcarrier blocks is presented as a precoding method that achieves both improvement in reception quality, reduction in computation scale, and reduction in feedback information.

  FIG. 16 illustrates an example of a subcarrier block division method on the frequency axis in the present embodiment. As shown in FIGS. 16A and 16B, it is assumed that stream A and stream B are each composed of 40 subcarriers. Here, 40 subcarriers of stream A are divided into subcarrier blocks A and 1, subcarrier blocks A and 2, subcarrier blocks A and 3, and subcarrier blocks A and 4 in units of 10 subcarriers. Similarly, 40 subcarriers of stream B are divided into subcarrier blocks B and 1, subcarrier blocks B and 2, subcarrier blocks B and 3, and subcarrier blocks B and 4 in units of 10 subcarriers.

  Then, the same precoding is performed using (Method 1) for each subcarrier block unit. For example, the same precoding is applied to 10 carriers of subcarrier blocks A and 1 and 10 carriers of subcarriers B and 1. Similarly, 10 carriers of subcarrier blocks A and 2 and 10 carriers of subcarriers B and 2 are subjected to the same precoding, and 10 carriers of subcarrier blocks A and 3 and 10 carriers of subcarriers B and 3 are the same. And 10 carriers of subcarrier blocks A and 4 and 10 carriers of subcarriers B and 4 are subjected to the same precoding.

  Thereby, the terminal only needs to create feedback information in units of subcarrier blocks, and the feedback information can be reduced as compared with the case of creating feedback information of all subcarriers. In addition, since the base station performs precoding in units of blocks, the reception quality is improved as compared with the case where the same precoding is applied to all subcarriers, and the case where different precoding is applied to each subcarrier. In comparison, the operation scale can be reduced.

  As described above, according to the present embodiment, by performing precoding in units of subcarrier blocks, it is possible to compensate for the drawbacks of (Method 1) and (Method 2). That is, it is possible to compensate for the drawback of (Method 1) to enhance the effect of improving reception quality, and to compensate for the drawback of (Method 2) to reduce the operation scale and reduce feedback information.

  Furthermore, if the precoding process mitigation method described in the first embodiment is applied to precoding in units of subcarrier blocks according to the present embodiment, the precoding process is further reduced and the reception quality is effectively improved. Can be improved.

  In addition, although the example which comprises a subcarrier block per 10 subcarriers was demonstrated in FIG. 16, it is not restricted to this, For example, you may comprise a subcarrier block per 5 subcarriers. Also, the number of subcarriers constituting each subcarrier block does not have to be the same in each subcarrier block. For example, the first subcarrier block is composed of 10 subcarriers, and the second subcarrier block is composed of 20 subcarrier blocks. You may comprise with a carrier. Further, the configuration of subcarrier blocks may be switched depending on the communication status.

  Further, although the present embodiment has been described by taking the OFDM system as an example of the multicarrier transmission system, the present invention is not limited to this.

  In the MIMO system according to the present embodiment, the modulation signal is transmitted from different antennas at the same frequency.

  Furthermore, the present invention is not limited to the first and second embodiments, and can be implemented with various modifications. For example, although cases have been described with the above embodiment where each process of the present invention is implemented with a hardware configuration, the present invention is not limited to this, and each process of the present invention can also be performed with software.

  For example, a program for executing each process of the present invention may be stored in advance in a ROM (Read Only Memory), and the program may be operated by a CPU (Central Processor Unit). Further, a program for executing each process of the present invention is stored in a computer-readable storage medium, the program stored in the storage medium is recorded in a RAM (Random Access Memory) of the computer, and the computer is executed according to the program. You may make it operate.

  The present invention can be widely applied to a multi-antenna transmission method and apparatus capable of controlling the modulation scheme of a signal transmitted from each antenna for each antenna.

The block diagram which shows the structural example of the multi-antenna transmission apparatus (base station) which concerns on Embodiment 1 of this invention. Block diagram showing configuration examples of mapping unit and phase / amplitude control unit 3A is a diagram illustrating an example of signal point arrangement of a signal after mapping, and FIG. 3B is a diagram illustrating an example of signal point arrangement after phase / amplitude control. FIG. 2 is a block diagram illustrating a configuration example of a receiving device (terminal) according to the first embodiment. The figure which shows the example of a frame structure of the signal transmitted / received between a base station and a terminal Flowchart showing the precoding procedure of the first embodiment In FIG. 7A, a QPSK modulated signal is transmitted as a modulated signal of stream A and stream B, and | h _{11, d} | ² = | h _{12, d} | ² and | h _{21, d} | ² = | h _{22, d} | ² FIG. 7B is a graph showing the relationship between the phase rotation between the modulated signals and the square of the minimum Euclidean distance. QPSK modulated signals are transmitted as the modulated signals of stream A and stream B, and | h _{11, d} | ² = 4 | h _{12, d} | ² and | h _{21, d} | ² = 4 | h _{22, d} | ² , Or 4 | h _{11, d} | ² = | h _{12, d} | ² and 4 | h _{21, d} | ² = | h _{22, d} | ² signal points of reception candidate signal points at the receiver Diagram showing example of arrangement A BPSK modulation signal is transmitted using the modulation scheme of stream A and stream B as a BPSK modulation signal, and | h _{11, d} | ² = | h _{12, d} | ² , θ _d = Arg (h _{11, d} / h _{12, d} ) a signal point arrangement example of reception candidate signal points at the receiver in the case of _d ) Stream A is BPSK and Stream B is QPSK and | h _{11, d} | ² = 2 | h _{12, d} | ² and | h _{21, d} | ² = 2 | h _{22, d} | ² , or stream A is QPSK ^h 11, d _| | ₂ is the stream B at the BPSK in ^{_{2 = | h 12, d |}} 2 and ^{_{2 | h 21, d | 2}} = | h 22, d | a case ^2, the received candidate signal at the receiver Diagram showing an example of signal point arrangement of points In FIG. 11A, stream A is 16QAM and stream B is QPSK. | H _{11, d} | ² = 5 | h _{12, d} | ² and | h _{21, d} | ² = 5 | h _{22, d} | ² and θ _d = 30 [°], or stream A is QPSK and stream B is 16QAM. 5 | h _{11, d} | ² = | h _{12, d} | ² and 5 | h _{21, d} | ² = | h _22, FIG. 11B is a diagram showing a model of _d | ² and θ _d = 30 [°], and FIG. 11B shows that stream A is 16QAM and stream B is QPSK, 16 | h _{11, d} | ² = 5 | h _{12, d} | ^2, and 16 | H _{21, d} | ² = 5 | h _{22, d} | ² or stream A is QPSK and stream B is 16QAM 5 | h _{11, d} | ² = 16 | h _{12, d} | ² and 5 ^{_{| h 21, d | 2 =}} 16 | h 22, d | It shows a model in FIG. 2 is a block diagram illustrating a configuration example of a multi-antenna transmission apparatus (base station) according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration example of a multi-antenna transmission apparatus (base station) according to a second embodiment. FIG. 9 is a block diagram illustrating a configuration example of a receiving apparatus (terminal) according to the second embodiment. FIG. 3 is a block diagram illustrating a configuration example of a multi-antenna transmission apparatus (base station) according to a second embodiment. 16A shows an example of subcarrier division for stream A, and FIG. 16B shows an example of subcarrier division for stream B. Diagram showing the relationship between the transmitting and receiving antennas The figure which shows the example of a frame structure on the time-axis of the modulation signal transmitted from each antenna

Explanation of symbols

100, 500, 600, 800 Multi-antenna transmitter (base station)
105_A, 105B Mapping unit 107_A, 107_B Phase / amplitude control unit 118 Transmission method determination unit 120 Frame configuration signal generation unit 206 Model selection unit 208 Phase / amplitude control circuit 501_A, 501_B Phase control unit 502_A, 502_B Amplification unit

Claims (4)

Determining a modulation scheme of a modulation signal transmitted from each antenna based on feedback information from a communication partner station;
Selecting a precoding model corresponding to a combination of modulation schemes of modulation signals transmitted from the antennas from a plurality of precoding models prepared in advance;
Precoding with the precoding model as a target;
Including a multi-antenna transmission method. Determining whether it is a line-of-sight environment or a non-line-of-sight environment based on feedback information from the communication partner station;
If it is determined that the environment is unforeseen, the precoding is not performed.
The multi-antenna transmission method according to claim 1. A multi-antenna transmission apparatus capable of controlling a modulation scheme of a signal transmitted from each antenna for each antenna,
A receiving means for receiving, as feedback information, a channel fluctuation value between the receiving antenna of the communication partner station and each of the transmission antennas;
A plurality of precoding models corresponding to combinations of modulation schemes transmitted from each antenna are stored, and one precoding model is selected from the plurality of stored precoding models based on the feedback information, and then selected. A phase / amplitude control means for performing precoding processing using the precoding model,
A multi-antenna transmission apparatus comprising: Based on feedback information from the communication partner station, further comprises means for determining whether the environment is a line-of-sight environment or a non-line-of-sight environment,
The phase / amplitude control means does not perform the precoding process when it is determined that the environment is not visible.
The multi-antenna transmission apparatus according to claim 3.

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