JP2006303691A - Mimo-receiving device, reception method, and radio communications system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MIMO receiving device capable of sufficiently suppressing interference from other transmission antennas in the filter reception of MINO of DS-CDMA, using the same code set in each transmission antenna, and to provide a reception method and a radio communications system. <P>SOLUTION: A correction coefficient calculating section 41 inputs an orthogonal coefficient ρ of a transmission line calculated by a transmission line orthogonal coefficient calculating section 43, and calculates a correction coefficient β that considers the interfering power of a transmission antenna signal as being larger than an actual value, as compared with the power of a desired transmission antenna signal. A weight calculating section 40 inputs the impulse response of the transmission line converted into a frequency region by FFT sections 12-1-1 to 12-M-N, chip noise power estimated by a chip noise estimating section 16, and the correction coefficient β calculated by the correction coefficient calculating section 41, and calculates the weight of a filter, based on MMSE. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a MIMO (Multiple Input Multiple Output) receiving apparatus, a receiving method, and a wireless communication system, and more particularly to a minimum mean square error method (MMSE) using a plurality of receiving antennas.
The present invention relates to a MIMO receiving apparatus, a receiving method, and a wireless communication system that perform signal demodulation by Mean Square Error).

  It is important to realize high-speed data transmission in the next-generation mobile communication wireless communication system. As a technique for realizing high-speed data transmission, a MIMO multiplexing system that transmits signals from a plurality of transmitting antennas using the same frequency and time and demodulates signals (signal separation) using a plurality of receiving antennas has attracted attention. Yes.

  FIG. 3 is a diagram illustrating a MIMO transmitting / receiving apparatus when the number of transmission antennas is M (M is an integer of 1 or more) and the number of reception antennas is N (N is an integer of 1 or more). The transmission side includes transmission antennas 1-1 to 1-M and the transmission device 2, and the reception side includes reception antennas 3-1 to 3-N and the reception device 4. By transmitting different signals from the plurality of transmission antennas 1-1 to 1-M using the same frequency and time and receiving signals using the plurality of reception antennas 3-1 to 3-N, the transmission bandwidth High-speed data transmission proportional to the number of transmission antennas is possible without increasing the number of transmission antennas. On the receiving side, signal separation processing is required to demodulate signals from the plurality of transmitting antennas 1-1 to 1-M from signals received by the plurality of receiving antennas 3-1 to 3-N.

  There are various methods for demodulating a MIMO multiplexed signal, and linear filter reception is a relatively simple method. When MIMO multiplexing is used for DS-CDMA (Direct Sequence-Code Division Multiple Access) signals, in addition to interference from other transmission antennas, multipath of the desired transmission antenna signal also becomes interference, and these interferences are simultaneously suppressed. Filter reception is effective. A frequency domain equalizer that performs this signal processing easily in the frequency domain has been proposed (see, for example, Non-Patent Document 1).

  FIG. 4 shows an example of a configuration when the frequency domain equalizer described in Non-Patent Document 1 is used in a DS-CDMA MIMO receiver. The MIMO receiving apparatus will be described assuming that the number of transmitting antennas is M (M is an integer of 1 or more) and the number of receiving antennas is N (N is an integer of 1 or more). Conventional MIMO receivers include transmission path estimators 10-1-1 to 10-MN, S / P (serial-parallel) converters 11-1-1 to 11-MN, 14-1 to 14-. N, FFT (Fast Fourier Transform) units 12-1-1 to 12-MN, 15-1 to 15-N, GI (guard interval) removing units 13-1 to 13-N, chip noise estimating unit 16, Weight calculation unit 17, filter processing unit 18, IFFT (fast inverse Fourier transform) units 19-1 to 19-M, P / S (parallel serial) conversion units 20-1 to 20-M, and despreading circuit 21-1 21-M.

  The transmission path estimators 10-1-1 to 10-MN receive signals received by the receiving antennas 3-1 to 3-N, and use a known pilot signal included in the received signal to transmit the transmitting antenna 1 The transmission path estimation value between −1 to 1-M and the receiving antennas 3-1 to 3-N is estimated for each path, and the impulse response is obtained.

  The S / P conversion units 11-1-1 to 11-MN perform S / P conversion on the impulse response of the transmission path estimated by the transmission path estimation units 10-1-1 to 10-MN.

  The FFT units 12-1-1 to 12 -MN receive the impulse responses of the transmission lines converted by the S / P converters 11-1-1 to 11 -MN and convert them to the frequency domain.

  The chip noise estimator 16 receives the signals received by the receiving antennas 3-1 to 3-N and the transmission path estimation values estimated by the transmission path estimators 10-1-1 to 10-MN, and the chip noise power Is estimated.

  The weight calculation unit 17 receives the impulse response of the transmission path converted into the frequency domain by the FFT units 12-1-1 to 12 -MN and the chip noise power estimated by the chip noise estimation unit 16, and receives the minimum mean square error. The weight of the filter is calculated by the method (MMSE).

  The GI removal units 13-1 to 13-N receive the signals received by the reception antennas 3-1 to 3-N, and remove received signals corresponding to the GI with reference to reception path timing.

  The S / P converters 14-1 to 14-N perform S / P conversion on the signals from which the GI has been removed by the GI removers 13-1 to 13-N.

  The FFT units 15-1 to 15-N receive the reception signals converted by the S / P conversion units 14-1 to 14-N and convert them into the frequency domain.

  The filter processing unit 18 receives the weight calculated by the weight calculation unit 17 and the reception signal frequency-converted by the FFT units 15-1 to 15-N, and performs filtering (equalization) of the reception signal in the frequency domain.

  The IFFT units 19-1 to 19-M receive the frequency domain signal equalized by the filter processing unit 18 and convert it into the time domain.

  The P / S conversion units 20-1 to 20-M perform P / S conversion on the signal converted into the time domain.

  The despreading circuits 21-1 to 21-M receive time domain signals converted by the P / S conversion units 20-1 to 20-M, perform despreading, and transmit from the transmission antennas 1-1 to 1-M. The transmitted signal is demodulated.

  FIG. 5 is a block diagram illustrating a configuration of the weight calculation unit 17 in the subcarrier f after FFT (1 ≦ f ≦ F). The conventional weight calculation unit 17 in the subcarrier f includes correlation matrix generation units 30-1 to 30-M, a correlation matrix addition unit 31, a noise addition unit 32, an inverse matrix calculation unit 33, and weight generation units 34-1 to 34-34. M, and each subcarrier has the same configuration.

  Correlation matrix generation units 30-1 to 30-M input transmission path estimation values between the transmission antenna and the reception antenna converted into the frequency domain by the FFT units 12-1-1-1 to 12-MN of FIG. A correlation matrix from each transmission antenna to the reception antenna is generated for each transmission antenna.

  The correlation matrix adding unit 31 inputs the correlation matrix for each transmission antenna generated by the correlation matrix generating units 30-1 to 30-M, and adds the correlation matrix.

  The noise adder 32 receives the correlation matrix added by the correlation matrix adder 31 and the chip noise power estimated by the chip noise estimator 16 of FIG. 4 and adds a noise component to the correlation matrix.

  The inverse matrix calculation unit 33 receives the correlation matrix obtained by adding the noise components by the noise addition unit 32 and performs an inverse matrix calculation.

  The weight generation units 34-1 to 34-M input the inverse matrix calculated by the inverse matrix calculation unit 33 and the transmission path estimation value between the transmission antenna and the reception antenna converted to the frequency domain, and generate filter weights.

The above processing will be described in detail using mathematical expressions. Transmission path vector H _m (1 ≦ m ≦ M) and the transmission path vector H _m (in the subcarrier f) obtained by converting the impulse response of the transmission path into the frequency domain by the FFT units 12-1-1-1 to 12-MN. f) is defined by the following equation.
H _m (f) = [h _{m, 1} (f), h _{m, 2} (f),..., H _{m, N} (f)] ^T (1)

Here, T represents transposition. Also, the received signal vector X (f) in subcarrier f obtained by converting the received signal into the frequency domain by FFT sections 15-1 to 15-N is defined by the following equation.
X (f) = [x ₁ (f), x ₂ (f),..., X _N (f)] ^T (2)
The weight vector W _m (f) of the filter of the transmission antenna m in the subcarrier f calculated by the weight calculation unit 17 is expressed by the following equation.

ここで、Ｈは複素共役転置、Ｐはパイロット電力、Ｄはデータ電力、Ｋはデータのコード数、Ｎ_０はチップ雑音電力、Ｉは単位行列を示す。

Here, H is a complex conjugate transpose, P is pilot power, D is data power, K is the number of data codes, N ₀ is chip noise power, and I is a unit matrix.

  The transmission signal vector Y (f) in the subcarrier f equalized and signal-separated by the filter processing unit 18 is expressed by the following equation.

Y (f) = W ^H (f) X (f) (4)
Here, W (f) and Y (f) are defined by the following equations.

W (f) = [W ₁ (f), W ₂ (f),..., W _M (f)] ^T (5)
Y (f) = [Y ₁ (f), Y ₂ (f),..., Y _M (f)] ^T (6)

Xu Zhu and Ross D.D. Murch, “Novel Frequency-Domain Equalization Architectures for a Single-Carrier Wireless MIMO System,” IEEE VTC2002-Fall, pp. 196 874-878, Sep. 2002.

  The conventional MIMO receiver has the following problems. In the filter weight calculation in the weight calculation unit 17, the correlation matrix generation unit 30-1 to 30 -M generates a correlation matrix for each transmission antenna, and the correlation matrix addition unit 31 adds them to all transmission antennas. The degree of suppression of interference between transmission antennas is determined by the relationship.

  The frequency domain equalizer described in Non-Patent Document 1 is a filter weight calculation formula of a non-spreading method (or a different code set for each transmitting antenna even in the spreading method), and the same code set is used for each transmitting antenna. In the case of DS-CDMA MIMO using the above, there is a problem that the weight accuracy is shifted and the characteristics are deteriorated.

  This is because, in the case of DS-CDMA MIMO using the same code set at each transmission antenna, when demodulating a desired transmission antenna signal, the same path with the same code among the interference from other transmission antennas. This is because the despreading gain cannot be obtained with respect to the above signal, and interference from other transmitting antennas cannot be sufficiently suppressed by the outputs of the despreading circuits 21-1 to 21-M.

  An object of the present invention is to provide a transmission path so that interference from other transmission antennas is sufficiently suppressed by the output of a despreading circuit in DS-CDMA MIMO filter reception using the same code set in each transmission antenna. MIMO that achieves excellent interference suppression characteristics by calculating the filter weight by correcting the transmission antenna signal power that causes interference more than the actual transmission antenna power based on the orthogonality of the desired To provide a receiving apparatus, a receiving method, and a wireless communication system.

  In order to solve the above problems, a first MIMO receiving apparatus provided by the present invention is a receiving apparatus that receives a CDMA signal transmitted from a plurality of transmitting antennas using a plurality of receiving antennas, and is orthogonal to the transmission path. Correction coefficient calculation means for calculating a correction coefficient (a constant of 1 or more) that considers the power of the transmission antenna signal that causes interference more than the actual power than the power of the desired transmission antenna signal based on the characteristics; A weight calculation means for calculating a weight of a filter for filtering the received signal based on a minimum mean square error method (MMSE) using a transmission path estimation value between the transmitting and receiving antennas, and filtering the received signal with the weight; And a filter processing unit that suppresses a transmission antenna signal that causes interference and demodulates a desired transmission antenna signal.

  For example, the correction coefficient calculation means may calculate the interference component of the transmission antenna signal that causes interference, the interference component of the same path where the despread gain is obtained, and the interference component of the same path where the despread gain is obtained, The correction coefficient is calculated as a sum of interference components of different codes.

  The weight calculation means and the filter processing unit can be performed by time domain signal processing. Alternatively, the weight calculation unit and the filter processing unit can be performed by frequency domain signal processing.

  When the weight calculation means performs signal processing in the frequency domain, for example, a first correlation that generates a correlation matrix from a channel estimation value between a desired transmission antenna and reception antenna expressed in the frequency domain. Matrix generation means, second correlation matrix generation means for generating a correlation matrix for each transmission antenna from a transmission path estimation value between the transmission antenna and the reception antenna that causes interference expressed in the frequency domain, and Correction coefficient multiplication means for multiplying the correlation matrix for each transmission antenna generated by the correlation matrix generation means by the correction coefficient calculated by the correction coefficient calculation means; a correlation matrix for each transmission antenna multiplied by the correction coefficient; A correlation matrix addition means for adding all the correlation matrices generated by one correlation matrix generation means; and a noise power addition for adding a noise component to the correlation matrix added by the correlation matrix addition means. Means, an inverse matrix computing means for computing an inverse matrix of the correlation matrix obtained by adding the noise component by the noise power adding means, and an inverse matrix of the correlation matrix computed by the inverse matrix computing means and a desired matrix expressed in the frequency domain Weight generating means for generating a weight from a transmission path estimated value between the transmitting antenna and the receiving antenna;

  A second MIMO receiving apparatus provided by the present invention is a receiving apparatus that receives a CDMA signal transmitted from a plurality of transmitting antennas by a plurality of receiving antennas, and receives a received signal as an input and determines a delay profile of a transmission path. A path search unit that generates and detects a plurality of paths having a large level from the delay profile; a transmission path orthogonal coefficient calculation unit that calculates an orthogonal coefficient of a transmission path from the plurality of paths detected by the path search unit; Correction coefficient calculation means for calculating a correction coefficient (a constant of 1 or more) that considers the power of the transmission antenna signal causing interference more than the actual power based on the transmission path orthogonal coefficient, and the correction coefficient Is used to filter the received signal based on the minimum mean square error method (MMSE). A weight calculation means for calculating the filter weights to filter the received signal at the weight suppresses the transmission antenna signal serving as interference, and having a filter processing unit that demodulates a transmission antenna signal of the desired.

  For example, the correction coefficient calculation means may calculate the interference component of the transmission antenna signal that causes interference, the interference component of the same path where the despread gain is obtained, and the interference component of the same path where the despread gain is obtained, The correction coefficient is calculated as a sum of interference components of different codes.

  The weight calculation means and the filter processing unit can be performed by time domain signal processing. Alternatively, the weight calculation unit and the filter processing unit can be performed by frequency domain signal processing.

  When the weight calculation means performs signal processing in the frequency domain, for example, a first correlation that generates a correlation matrix from a channel estimation value between a desired transmission antenna and reception antenna expressed in the frequency domain. Matrix generation means, second correlation matrix generation means for generating a correlation matrix for each transmission antenna from a transmission path estimation value between the transmission antenna and the reception antenna that causes interference expressed in the frequency domain, and Correction coefficient multiplication means for multiplying the correlation matrix for each transmission antenna generated by the correlation matrix generation means by the correction coefficient calculated by the correction coefficient calculation means; a correlation matrix for each transmission antenna multiplied by the correction coefficient; A correlation matrix addition means for adding all the correlation matrices generated by one correlation matrix generation means; and a noise power addition for adding a noise component to the correlation matrix added by the correlation matrix addition means. Means, an inverse matrix computing means for computing an inverse matrix of the correlation matrix obtained by adding the noise component by the noise power adding means, and an inverse matrix of the correlation matrix computed by the inverse matrix computing means and a desired matrix expressed in the frequency domain Weight generating means for generating a weight from a transmission path estimated value between the transmitting antenna and the receiving antenna;

  Another aspect of the present invention is a receiving method applied to a receiving apparatus that receives signals transmitted from a plurality of transmitting antennas by a CDMA system using a plurality of receiving antennas, and is based on orthogonality of transmission paths. A correction coefficient (constant of 1 or more) that considers the power of the transmission antenna signal that causes interference to be greater than the actual power of the transmission antenna signal is calculated, and the correction coefficient and the transmission path estimation values between all transmitting and receiving antennas are used Then, based on the minimum mean square error method (MMSE), the weight of the filter for filtering the received signal is calculated, the received signal is filtered with the weight, the transmission antenna signal that causes interference is suppressed, and the desired transmission antenna signal Is demodulated.

  According to still another aspect of the present invention, a wireless communication system includes a transmission device that includes a plurality of transmission antennas and transmits a CDMA signal using the same code set at each transmission antenna, and the reception device of the present invention. It is.

  In the MIMO receiving apparatus of the present invention, in DS-CDMA MIMO filter reception using the same code set in each transmission antenna, interference from other transmission antennas is sufficiently suppressed by the output of the despreading circuit. Based on the orthogonality of the transmission path, a correction that considers the power of the transmitting antenna signal that causes interference to be greater than the power of the desired transmitting antenna signal is performed, and excellent interference suppression characteristics are achieved by calculating the filter weight. it can.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a MIMO receiving apparatus according to the present invention. The same parts as those in FIG. 4 are denoted by the same reference numerals. In FIG. 1, the number of transmitting antennas is M (M is an integer of 1 or more), the number of receiving antennas is N (N is an integer of 1 or more), and the MIMO receiving apparatus will be described. The MIMO receiver of the present invention includes transmission path estimation units 10-1-1 to 10-MN, S / P conversion units 11-1-1 to 11-MN, 14-1 to 14-N, and FFT. Units 12-1-1-1 to 12-MN, 15-1 to 15-N, GI removal units 13-1 to 13-N, chip noise estimation unit 16, filter processing unit 18, IFFT units 19-1 to 19-19 -M, P / S conversion units 20-1 to 20-M, despreading circuits 21-1 to 21-M, weight calculation unit 40, correction coefficient calculation unit 41, path search unit 42, and transmission path orthogonal coefficient calculation unit 43 Consists of.

  The transmission path estimators 10-1-1 to 10-MN receive signals received by the receiving antennas 3-1 to 3-N, and use a known pilot signal included in the received signal to transmit the transmitting antenna 1 The transmission path estimation value between −1 to 1-M and the receiving antennas 3-1 to 3-N is estimated for each path, and the impulse response is obtained.

  The S / P conversion units 11-1-1 to 11-MN perform S / P conversion on the impulse response of the transmission path estimated by the transmission path estimation units 10-1-1 to 10-MN.

  The FFT units 12-1-1 to 12 -MN receive the impulse responses of the transmission lines converted by the S / P converters 11-1-1 to 11 -MN and convert them to the frequency domain.

  The chip noise estimator 16 receives the signals received by the receiving antennas 3-1 to 3-N and the transmission path estimation values estimated by the transmission path estimators 10-1-1 to 10-MN, and the chip noise power Is estimated. There are various methods for estimating chip noise power, but since they are not directly related to the present invention, the detailed configuration and description thereof will be omitted.

  The path search unit 42 receives signals received by the reception antennas 3-1 to 3-N, generates a delay profile of a transmission path using a known pilot signal included in the reception signal, and determines a level from the delay profile. Detect large multiple paths.

  The transmission path orthogonal coefficient calculation unit 43 inputs a plurality of paths with a large level detected by the path search unit 42, and calculates the transmission path orthogonal coefficient ρ (0 ≦ ρ ≦ 1). The larger ρ is, the higher the orthogonality of the transmission line is. When ρ = 1, it represents a completely orthogonal one-path transmission line, and when ρ = 0, it represents a non-orthogonal transmission line with many paths separated. As described above, the orthogonal coefficient ρ of the transmission path can be adaptively calculated using the received signal, but a fixed value can also be used when the propagation environment is known in advance.

  The correction coefficient calculation unit 41 receives the transmission channel orthogonal coefficient ρ calculated by the transmission channel orthogonal coefficient calculation unit 43, and corrects the transmission antenna signal power that causes interference more than the actual transmission antenna signal power. The coefficient β (β is a constant of 1 or more) is calculated.

  The weight calculation unit 40 calculates the impulse response of the transmission path converted into the frequency domain by the FFT units 12-1-1 to 12 -MN, the chip noise power estimated by the chip noise estimation unit 16, and the correction coefficient calculation unit 41. The correction coefficient β is input, and the weight of the filter is calculated by the minimum mean square error method (MMSE).

  The GI removal units 13-1 to 13-N receive the signals received by the reception antennas 3-1 to 3-N, and remove received signals corresponding to the GI with reference to reception path timing.

  The S / P converters 14-1 to 14-N perform S / P conversion on the reception signals from which the GI has been removed by the GI removers 13-1 to 13-N.

  The FFT units 15-1 to 15-N receive the reception signals converted by the S / P conversion units 14-1 to 14-N and convert them into the frequency domain.

  The filter processing unit 18 receives the weight calculated by the weight calculation unit 40 and the reception signal frequency-converted by the FFT units 15-1 to 15-N, and performs filtering (equalization) of the reception signal in the frequency domain.

  The filter processing unit 18 suppresses multipath interference of a desired transmission antenna signal at the same time as suppressing interference from other transmission antennas.

  The IFFT units 19-1 to 19-M receive the frequency domain signal equalized by the filter processing unit 18 and convert it into the time domain.

  The P / S conversion units 20-1 to 20-M perform P / S conversion on the signal converted into the time domain.

  The despreading circuits 21-1 to 21-M receive time domain signals converted by the P / S conversion units 20-1 to 20-M, perform despreading, and transmit from the transmission antennas 1-1 to 1-M. Is demodulated.

  The operation of the embodiment of the present invention will be described with reference to the drawings. Here, the weight calculator 40 shown in FIG. 1 will be described in detail. FIG. 2 is a block diagram showing a configuration of the weight calculation unit 40 of the transmission antenna m (1 ≦ m ≦ M) in the subcarrier f (1 ≦ f ≦ F) after the FFT of the present invention. The weight calculation unit 40 of the transmission antenna m in the subcarrier f includes a first correlation matrix generation unit 50, second correlation matrix generation units 51-1 to 51-M, a correction coefficient multiplication unit 52, a correlation matrix addition unit 53, and noise addition. Unit 54, inverse matrix calculation unit 55, and weight generation unit 56. Each subcarrier and each transmission antenna have the same configuration.

  The first correlation matrix generation unit 50 inputs a transmission path estimation value between the desired transmission antenna m and the reception antenna converted into the frequency domain by the FFT units 12-1-1-1 to 12-MN of FIG. A correlation matrix from the antenna m to the receiving antenna is generated.

  The second correlation matrix generation units 51-1 to 51-M estimate the transmission path between the transmission antenna and the reception antenna that become interference converted into the frequency domain by the FFT units 12-1-1-1 to 12-MN of FIG. A value is input, and a correlation matrix from the transmitting antenna to the receiving antenna that causes interference is generated.

  The correction coefficient multiplication unit 52 inputs the correlation matrix of the transmission antenna that is the interference generated by the second correlation matrix generation units 51-1 to 51-M and the correction coefficient β calculated by the correction coefficient calculation unit 41 of FIG. A correction coefficient β is multiplied by the correlation matrix for each transmission antenna, and correction is performed so that the correlation matrix of the transmission antenna that causes interference is larger than the correlation matrix of the desired transmission antenna m.

  The correlation matrix adding unit 53 inputs the correlation matrix of the desired transmission antenna m generated by the first correlation matrix generation unit 50 and the correlation matrix of the transmission antenna that becomes interference multiplied by the correction coefficient β by the correction coefficient multiplication unit 52, Add each correlation matrix.

  The noise adder 54 receives the correlation matrix added by the correlation matrix adder 53 and the chip noise power estimated by the chip noise estimator 16 of FIG. 1, and adds a noise component to the correlation matrix.

  The inverse matrix calculation unit 55 inputs the correlation matrix obtained by adding the noise component by the noise addition unit 54 and performs an inverse matrix calculation.

  The weight generation unit 56 inputs the inverse matrix calculated by the inverse matrix calculation unit 55 and the transmission path estimation value between the desired transmission antenna m and the reception antenna converted into the frequency domain, and generates the weight of the filter.

The above processing will be described in detail using mathematical expressions. The definition of the transmission path vector H _m (f) between the transmission antenna m and the reception antenna in the subcarrier f obtained by converting the impulse response of the transmission path into the frequency domain by the FFT units 12-1-1 to 12 -MN When the received signal vector X (f) in the subcarrier f obtained by converting the received signal into the frequency domain by the FFT units 15-1 to 15-N as defined in 1) is defined as in Expression (2), the weight shown in FIG. The weight vector W _m (f) of the filter of the transmission antenna m in the subcarrier f calculated by the calculation unit 40 is expressed by the following equation.

ここで、補正係数計算部４１で計算した補正係数βは、伝送路の直交性に依存した値であり、例えば、次式のように求められる。

Here, the correction coefficient β calculated by the correction coefficient calculation unit 41 is a value depending on the orthogonality of the transmission path, and is obtained, for example, by the following equation.

ここで、ＳＦは逆拡散回路２１−１〜２１−Ｍの拡散率（データの拡散率）を表す。式（８）で分母は実際の干渉となる送信アンテナ信号の電力であり、分子は逆拡散回路２１−１〜２１−Ｍの出力で干渉となる送信アンテナ信号を十分に抑圧できるようにウエイト計算で大きくみなす干渉電力である。この電力は干渉となる送信アンテナ信号の電力を逆拡散利得が得られない同一コードで同一パスの干渉成分ＳＦρＤと、逆拡散利得が得られる同一コードで異なるパスの干渉成分（１−ρ）Ｄおよび異なるコードの干渉成分Ｐ＋（Ｋ−１）Ｄとの和とみなして求める。

Here, SF represents the spreading factor (data spreading factor) of the despreading circuits 21-1 to 21-M. In equation (8), the denominator is the power of the transmission antenna signal that becomes the actual interference, and the numerator calculates the weight so that the transmission antenna signal that causes the interference can be sufficiently suppressed by the output of the despreading circuits 21-1 to 21-M. This is the interference power that is considered to be large. This power is an interference component SFρD of the same path with the same code where despread gain is not obtained, and an interference component (1-ρ) D of a different path with the same code where despread gain is obtained. And the sum of interference components P + (K−1) D of different codes.

  As described above, the weight calculation unit 40 uses the correction coefficient β based on the orthogonality of the transmission path and regards the power of the transmission antenna signal that causes interference more than the actual power of the transmission antenna signal. In DS-CDMA MIMO using the same code set for each transmission antenna to perform correction and calculate the filter weight, interference from other transmission antennas is sufficient at the output of the despreading circuits 21-1 to 21-M. It is possible to demodulate the signals from the transmission antennas 1-1 to 1 -M suppressed to.

  In the above-described embodiment, the weight calculation unit 40 and the filter processing unit 18 perform frequency domain signal processing. However, the same effect can be obtained by performing time domain signal processing. Is applicable.

  Further, the present invention can be applied to both a base station radio apparatus and a mobile station radio apparatus of a mobile communication system.

  According to the present invention, a MIMO receiving apparatus having excellent interference suppression characteristics can be realized.

It is a block diagram which shows one Example of the MIMO receiver of this invention. It is a block diagram which shows the structure of the weight calculation part of this invention. It is a figure which shows the structure of a MIMO transmission / reception apparatus. It is a block diagram which shows an example of the conventional MIMO receiver. It is a block diagram which shows the structure of the conventional weight calculation part.

Explanation of symbols

1-1 to 1-M transmitting antenna 2 transmitting apparatus 3-1 to 3-N receiving antenna 4 receiving apparatus 10-1-1 to 10-MN transmission path estimation units 11-1-1 to 11-MN S / P converters 12-1-1 to 12 -MN FFT units 13-1 to 13 -N GI removal units 14-1 to 14 -N S / P converters 15-1 to 15 -N FFT unit 16 Chip noise estimation unit 17 Weight calculation unit 18 Filter processing units 19-1 to 19-M IFFT units 20-1 to 20-M P / S conversion units 21-1 to 21-M Despreading circuits 30-1 to 30-M Correlation matrix generation unit 31 Correlation matrix addition unit 32 Noise addition unit 33 Inverse matrix operation units 34-1 to 34-M Weight generation unit 40 Weight calculation unit 41 Correction coefficient calculation unit 42 Path search unit 43 Transmission path orthogonal coefficient calculation unit 50 One correlation matrix generators 51-1 to 51-M Second correlation matrix Generating section 52 correction coefficient multiplication unit 53 correlation matrix addition unit 54 the noise adding section 55 inverse matrix calculator 56 weight generating unit

Claims (12)

A receiving device that receives signals of a CDMA system transmitted from a plurality of transmitting antennas by a plurality of receiving antennas,
Correction coefficient calculation means for calculating a correction coefficient (a constant of 1 or more) that considers the power of the transmission antenna signal that causes interference more than the actual power based on the orthogonality of the transmission path;
Weight calculation means for calculating a weight of a filter for filtering a received signal based on a minimum mean square error (MMSE) method using the correction coefficient and transmission path estimation values between all transmitting and receiving antennas. When,
A MIMO receiving apparatus comprising: a filter processing unit that filters a reception signal with the weight, suppresses a transmission antenna signal that causes interference, and demodulates a desired transmission antenna signal.   The correction coefficient calculation means calculates the interference component of the different path in the same code that can obtain the interference component of the same path and the despread gain with the same code for which the despread gain cannot be obtained for the power of the transmission antenna signal that causes interference. The MIMO receiving apparatus according to claim 1, wherein the correction coefficient is calculated on the assumption that the correction coefficient is a sum of the interference component and the interference component.   The MIMO receiving apparatus according to claim 1, wherein the weight calculation unit and the filter processing unit perform signal processing in a time domain.   The MIMO receiving apparatus according to claim 1, wherein the weight calculation unit and the filter processing unit perform signal processing in a frequency domain. The weight calculation means is frequency domain signal processing,
First correlation matrix generation means for generating a correlation matrix from a channel estimation value between a desired transmission antenna and reception antenna expressed in a frequency domain;
Second correlation matrix generation means for generating a correlation matrix for each transmission antenna from a transmission path estimation value between the transmission antenna and the reception antenna that causes interference expressed in the frequency domain;
Correction coefficient multiplication means for multiplying the correlation matrix for each transmission antenna generated by the second correlation matrix generation means by the correction coefficient calculated by the correction coefficient calculation means, respectively.
Correlation matrix addition means for adding all of the correlation matrix for each transmission antenna multiplied by the correction coefficient and the correlation matrix generated by the first correlation matrix generation means;
Noise power adding means for adding a noise component to the correlation matrix added by the correlation matrix adding means;
An inverse matrix calculating means for calculating an inverse matrix of a correlation matrix obtained by adding a noise component by the noise power adding means;
Weight generating means for generating a weight from an inverse matrix of a correlation matrix calculated by the inverse matrix calculating means and a transmission path estimation value between a desired transmitting antenna and a receiving antenna expressed in a frequency domain, The MIMO receiver according to claim 1. A receiving device that receives signals of a CDMA system transmitted from a plurality of transmitting antennas by a plurality of receiving antennas,
A path search unit that receives a received signal as input and generates a delay profile of a transmission path, and detects a plurality of paths having a large level from the delay profile;
A transmission path orthogonal coefficient calculating means for calculating an orthogonal coefficient of a transmission path from a plurality of paths detected by the path search unit;
Correction coefficient calculation means for calculating a correction coefficient (a constant of 1 or more) that considers the power of the transmission antenna signal that causes interference more than the actual power of the transmission antenna signal based on the transmission path orthogonal coefficient;
A weight calculating means for calculating a weight of a filter for filtering a received signal based on a minimum mean square error method (MMSE) using the correction coefficient and a transmission path estimation value between all transmitting and receiving antennas;
A MIMO receiving apparatus comprising: a filter processing unit that filters a reception signal with the weight, suppresses a transmission antenna signal that causes interference, and demodulates a desired transmission antenna signal.   The correction coefficient calculation means calculates the interference component of the different path in the same code that can obtain the interference component of the same path and the despread gain with the same code for which the despread gain cannot be obtained for the power of the transmission antenna signal that causes interference. The MIMO receiving apparatus according to claim 6, wherein the correction coefficient is calculated by regarding the sum as an interference component.   The MIMO receiving apparatus according to claim 6, wherein the weight calculation unit and the filter processing unit perform time-domain signal processing.   The MIMO receiving apparatus according to claim 6, wherein the weight calculation unit and the filter processing unit perform signal processing in a frequency domain. The weight calculation means is frequency domain signal processing,
First correlation matrix generation means for generating a correlation matrix from a channel estimation value between a desired transmission antenna and reception antenna expressed in a frequency domain;
Second correlation matrix generation means for generating a correlation matrix for each transmission antenna from a transmission path estimation value between the transmission antenna and the reception antenna that causes interference expressed in the frequency domain;
Correction coefficient multiplication means for multiplying the correlation matrix for each transmission antenna generated by the second correlation matrix generation means by the correction coefficient calculated by the correction coefficient calculation means, respectively.
Correlation matrix addition means for adding all of the correlation matrix for each transmission antenna multiplied by the correction coefficient and the correlation matrix generated by the first correlation matrix generation means;
Noise power adding means for adding a noise component to the correlation matrix added by the correlation matrix adding means;
An inverse matrix calculating means for calculating an inverse matrix of a correlation matrix obtained by adding a noise component by the noise power adding means;
Weight generating means for generating a weight from an inverse matrix of a correlation matrix calculated by the inverse matrix calculating means and a transmission path estimation value between a desired transmitting antenna and a receiving antenna expressed in a frequency domain, The MIMO receiver according to claim 6. A receiving method applied to a receiving apparatus that receives signals transmitted from a plurality of transmitting antennas by a CDMA system using a plurality of receiving antennas,
Based on the orthogonality of the transmission path, a correction coefficient (a constant greater than or equal to 1) that considers the power of the transmission antenna signal that causes interference to be greater than the power of the desired transmission antenna signal is calculated. Based on the minimum mean square error method (MMSE), the transmission weight between the antennas is calculated based on the minimum mean square error method (MMSE), and the weight of the filter for filtering the reception signal is calculated. A MIMO receiving method comprising suppressing a signal and demodulating a desired transmitting antenna signal. A transmission apparatus comprising a plurality of transmission antennas, each transmitting antenna for transmitting a CDMA signal using the same code set;
A wireless communication system comprising: the receiving device according to claim 1.

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