JP2008205697A - Mimo receiver and reception method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MOMO receiver for achieving an excellent MIMO signal separation characteristic, while suppressing the increase in demodulation delay, by receiving a single carrier MIMO signal. <P>SOLUTION: The DFT part 51 of the MIMO receiver converts signals received by a plurality of reception antennas into the signals of a frequency domain. A channel estimating part 52 estimates channel gain between transmission antennas and the reception antennas by using a pilot signal inserted for every transmission antenna. A multi-path interference replica reproducing part 53 equalizes reception signals with the use of a weight calculated on the basis of the channel gain, and generates multi-path interference in the equalizing signal of each transmission antenna. A demodulating part 54 equalizes the reception signals with the use of the weight which is calculated in consideration of the channel gain and multi-path interference removal, subtracts the multi-path interference from the equalizing signal of each transmission antenna, and performs MIMO signal separation by MLD. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a MIMO receiving apparatus and a receiving method.

  High-speed data transmission is required in next-generation mobile communication wireless systems, and as a technology for realizing high-speed data transmission, data signals are transmitted from a plurality of transmitting antennas using the same frequency, and a plurality of receiving antennas are used. Attention has been focused on MIMO (Multiple Input Multiple Output) multiplexing for demodulating data signals.

  FIG. 1 is a diagram showing a configuration of a conventional MIMO transmission / reception system using MIMO multiplexing. In the MIMO transmission / reception system shown in FIG. 1, when the number of transmission antennas is M (M is an integer of 2 or more) and the number of reception antennas is N (N is an integer of 2 or more), the transmission side includes: It comprises a plurality of transmission devices 201 (first transmission antenna 202-1 to Mth transmission antenna 202-M). The reception side includes a plurality of reception antennas 203 (first reception antenna 203-1 to Nth reception antenna 203-N) and a reception device 204. By transmitting different data signals from a plurality of transmitting antennas 202 using the same frequency and receiving data signals using a plurality of receiving antennas 203, a high speed proportional to the number of transmitting antennas without increasing the transmission bandwidth. Data transmission can be performed.

  The receiving device 204 needs to demodulate (separate) each data signal transmitted from the plurality of transmitting antennas 202 from signals received by the plurality of receiving antennas 203. Various schemes have been proposed for this MIMO signal separation. For example, a linear processing filter based on a minimum mean square error (MMSE) is used as the simplest scheme, and a transmission antenna to be demodulated is used. A method for suppressing interference from other transmission antennas is known.

  In an uplink radio system for next-generation mobile communication, it is necessary to realize high transmission power efficiency in a terminal in order to expand a communication area. For this reason, a single carrier (SC) system having a low peak power to average power ratio (PAPR) is considered to be promising. When MIMO multiplexing is performed in the SC scheme, multipath interference becomes a problem. When MIMO signal separation is performed by an MMSE filter, MIMO signal separation and multipath interference suppression are performed simultaneously, that is, in the spatial direction and the time direction. MMSE equalization (two-dimensional MMSE equalization) is required. A method combining two-dimensional MMSE equalization and transmission antenna interference removal has excellent characteristics and is considered promising.

  FIG. 2 is a diagram illustrating a configuration of a conventional MIMO receiving apparatus. In the MIMO receiving apparatus shown in FIG. 2, an increase in the amount of computation is suppressed by performing two-dimensional MMSE equalization and transmission antenna interference removal by frequency domain signal processing. Further, a method for improving the characteristics by repeatedly performing the two-dimensional frequency domain equalization and the reception processing for removing the antenna interference has been considered (for example, see Non-Patent Document 1).

  The MIMO receiving apparatus shown in FIG. 2 receives single carrier MIMO signals transmitted from M (M is an integer of 2 or more) transmission antennas by N (N is an integer of 2 or more) receiving antennas, A MIMO receiver that performs MIMO signal separation by frequency domain signal processing. This MIMO receiving apparatus includes a plurality of receiving antennas 101 (first receiving antenna 101-1 to Nth receiving antenna 101-N) and a plurality of cyclic prefix (CP) removing units 102 (first CP removing unit 102). -1 to NCP removing unit 102-N), a plurality of Discrete Fourier Transform (DFT) units 103 (first DFT unit 103-1 to NDFT unit 103-N), and a plurality of reception filters 104 ( First reception filter 104-1 to Nth reception filter 104-N), subtraction unit 105, channel estimation unit 106, weight calculation unit 107, two-dimensional frequency domain equalization unit 108, and a plurality of discrete inverse Fouriers A transform (IDFT: Inverse Discrete Fourier Transform) unit 109 (first IDFT unit 109-1 to MIDFT unit 109-M) and a plurality of bit likelihoods Calculation unit 110 (first bit likelihood calculation unit 110-1 to Mth bit likelihood calculation unit 110-M) and a plurality of decoders 111 (first decoder 111-1 to Mth decoder 111-M) A plurality of symbol replica generation units 112 (first symbol replica generation unit 112-1 to M-th symbol replica generation unit 112-M), and a plurality of DFT units 113 (first DFT unit 113-1 to MDFT unit 113- M), a plurality of transmission / reception filters 114 (first transmission / reception filter 114-1 to M-th transmission / reception filter 114-M), and a plurality of antenna interference replica generation units 115 (first antenna interference replica generation units 115-1 to M-th. Antenna interference replica generation unit 115-M).

  FIG. 3 is a diagram illustrating an example of a radio frame format when frequency domain equalization is used. The frame format shown in FIG. 3 indicates a radio frame signal transmitted from one transmission antenna among a plurality of transmission antennas. The radio frame signal is composed of a plurality of blocks of pilot signals or data signals. In the example shown in FIG. 3, there is a pilot signal block at the head, and a plurality of data blocks are continued after that.

  A CP is added to the head of each block in order to avoid multipath interference from the previous block during DFT processing. CP is a signal generated by copying the last data of each block to the front. In MIMO, it is necessary to estimate the channel gain between the transmitting antenna and the receiving antenna, and the pilot signals of each transmitting antenna are preferably orthogonal to each other. Frequency multiplexing, code multiplexing, and the like are considered as a method for multiplexing pilot signals of each transmission antenna.

  Returning to FIG. 2 described above, the first receiving antenna 101-1 to the Nth receiving antenna 101-N receive the single carrier MIMO signal. The first CP removing unit 102-1 to the NCP removing unit 102-N receive each received antenna signal and remove a signal corresponding to the CP at a common timing. First DFT unit 103-1 to NDFT unit 103-N each receive antenna signal from which CP has been removed as input, perform DFT of NDFT1 (NDFT1 is an integer of 2 or more) points, and convert the received signal to a frequency domain signal. Convert. The first reception filter 104-1 to the Nth reception filter 104-N perform reception signal filtering in the frequency domain, and perform noise suppression and user separation. For the first reception filter 104-1 to the Nth reception filter 104-N, a raised cosine roll-off filter is generally used (including a roll-off rate of 0).

  In the configuration of FIG. 2, the first reception filter 104-1 to the Nth reception filter 104-N perform signal processing in the frequency domain, but the time domain prior to the first DFT unit 103-1 to the NDFT unit 103-N. This signal processing can also be performed. The subtracting unit 105 leaves the transmission antenna signal to be demodulated, and subtracts other transmission antenna interference replicas.

  Here, the subtraction unit 105 will be described. FIG. 4 is a diagram illustrating a configuration of the subtracting unit 105 for the DFT signal of the receiving antenna n. The subtracting unit 105 includes a first replica combining unit 121-1 to an Mth replica combining unit 121 -M, and a first subtractor 122-1 to an Mth subtractor 122 -M. The first replica synthesis unit 121-1 to M-th replica synthesis unit 121-M synthesizes transmission antenna interference replicas excluding the transmission antenna signal to be demodulated. The first subtractor 122-1 to M-th subtractor 122-M subtracts the outputs of the first replica combining unit 121-1 to M-th replica combining unit 121-M from the DFT signal of the receiving antenna n.

とする。また、送信アンテナｍの第ｉ繰り返し干渉レプリカを

とする。なお、

はＮ行の列ベクトルであり、

はＮ行の列ベクトルであるものとする。 The received signal of subcarrier k (1 ≦ k ≦ NDFT1) after DFT

And In addition, the i-th repetitive interference replica of the transmitting antenna m is

And In addition,

Is an N row column vector,

Let N be a column vector of N rows.

とすると、その等化用信号は次式で表される。

ただし、

はＮ行の列ベクトルであるものとする。またここで、最初（第０繰り返し）の受信処理では干渉除去は行わず、受信信号をそのまま用いる。すなわち、

である。 At this time, the equalization signal of the transmission antenna m after the i-th repetitive interference cancellation is

Then, the equalization signal is expressed by the following equation.

However,

Let N be a column vector of N rows. Here, in the first (0th repetition) reception process, interference is not removed and the received signal is used as it is. That is,

It is.

  Channel estimation section 106 estimates the channel gain between the transmission antenna and the reception antenna in the frequency domain using the pilot signal inserted for each transmission antenna. In the configuration of FIG. 2, the channel estimation unit 106 performs frequency domain signal processing, but can also perform time domain signal processing prior to the first DFT unit 103-1 to the NDFT unit 103-N.

とすると、その送信アンテナｍの第ｉ繰り返しＭＭＳＥウエイトは、チャネル推定値行列

と、雑音電力

とを用いて、次式で計算される。

なお、

はＮ列の行ベクトルであり、

はＮ行Ｍ列の行列であるものとする。 The weight calculation unit 107 calculates the weight of two-dimensional frequency domain equalization using the channel gain between the transmission antenna and the reception antenna. The weight calculation unit 107 generally uses an MMSE algorithm. I-th repeated MMSE weight of transmit antenna m

Then, the i-th iterative MMSE weight of the transmitting antenna m is a channel estimation value matrix

And noise power

And is calculated by the following equation.

In addition,

Is an N column row vector,

Is a matrix of N rows and M columns.

で表され、

は送信アンテナｍと受信アンテナとの間のチャネル推定値である。なお、

はＮ行の列ベクトルである。 Where the channel estimate matrix is

Represented by

Is the channel estimate between the transmit antenna m and the receive antenna. In addition,

Is a column vector of N rows.

は送信アンテナｍの第ｉ繰り返し干渉除去考慮行列であり、次式で表される。

ここで、

は、例えば、送信アンテナｍの時間領域の第ｉ繰り返し軟判定シンボルレプリカ

の平均電力を用いて次式で計算される。

ただし、Ｎ_ＳＹＭＢは、データブロックのシンボル数である。また、

は、初回（ｉ=0）では単位行列である。 Also,

Is an i-th iterative interference cancellation consideration matrix of the transmission antenna m, and is expressed by the following equation.

here,

Is, for example, the i-th iterative soft decision symbol replica in the time domain of the transmission antenna m.

Using the average power of

N _SYMB is the number of symbols in the data block. Also,

Is the unit matrix at the first time (i = 0).

とし、減算部１０５の出力を

とすると、２次元周波数領域等化部１０８で２次元等化した送信アンテナｍの等化信号

は、次式で表される。

The two-dimensional frequency domain equalization unit 108 receives the two-dimensional equalization weight calculated by the weight calculation unit 107 and the output of the subtraction unit 105 and multiplies them for each subcarrier, thereby performing MIMO signal separation and multi-frequency in the frequency domain. Simultaneously suppress path interference. The weight calculated by the weight calculation unit 107 is

And the output of the subtraction unit 105 is

Then, the equalized signal of the transmission antenna m that has been two-dimensionally equalized by the two-dimensional frequency domain equalization unit 108

Is expressed by the following equation.

First IDFT section 109-1 to MIDFT section 109-M receives the equalized signal of each transmission antenna, which is the output of two-dimensional frequency domain equalization section 108, and inputs N _IDFT (N _IDFT is an integer of 2 or more) points IDFT is performed to convert the equalized signal into a time domain signal.

  The first bit likelihood calculation unit 110-1 to the M-th bit likelihood calculation unit 110-M calculate the likelihood for each bit transmitted from the equalized signal of each transmission antenna. The output signal of the i-th repetition (i ≧ 1) of the first bit likelihood calculation unit 110-1 to the M-th bit likelihood calculation unit 110-M is a final bit demodulated signal. The first decoder 111-1 to the M-th decoder 111-M receive the bit likelihood of each transmission antenna signal and perform error correction decoding. A turbo code or a convolutional code is used for error correction coding.

  First symbol replica generation section 112-1 to M-th symbol replica generation section 112 -M generate symbol replicas from the decoding results of the respective transmission antenna signals. The first symbol replica generation unit 112-1 to the M-th symbol replica generation unit 112-M generate a hard decision symbol replica, a hard decision symbol replica, and a predetermined replica weight coefficient (a constant equal to or less than 1). There are a method of multiplication, a method of generating a soft decision symbol replica, and the like, and a method of generating a soft decision symbol replica has good characteristics.

  The first DFT unit 113-1 to the MDFT unit 113 -M receive the symbol replicas of the respective transmission antennas generated by the first symbol replica generation unit 112-1 to the M-th symbol replica generation unit 112 -M, and input NDFT 2 (NDFT 2 Is an integer greater than or equal to 2) and performs a DFT of the point to convert the symbol replica into a signal in the frequency domain. The first transmission / reception filter 114-1 to the Mth transmission / reception filter 114-M pass the frequency domain symbol replica through the transmission / reception filter.

とし、チャネル推定値を

とすると、送信アンテナｍの第ｉ繰り返し干渉レプリカ

は次式で表される。

First antenna interference replica generation section 115-1 to M-th antenna interference replica generation section 115 -M generate transmission antenna interference replicas using the frequency domain symbol replica signal and channel estimation value of each transmission antenna. The symbol replica signal in the frequency domain of the transmitting antenna m

And the channel estimate is

Then, the i th repetitive interference replica of the transmitting antenna m

Is expressed by the following equation.

  In addition to the above-described conventional techniques, techniques related to a MIMO receiving apparatus and a receiving method are known (see, for example, Patent Documents 1 to 4). In Patent Document 1 (Japanese Patent Laid-Open No. 2002-247011), a weighting factor reflecting the reliability of data is calculated using the likelihood calculated when a transmission signal is estimated and used for soft decision. The technology to do is described. In Patent Document 2 (Japanese Patent Laid-Open No. 2003-051802), a means for detecting frequency characteristics from a received signal of a receiver and performing frequency domain equalization, and an amplitude phase characteristic in a symbol from the frequency domain equalized signal are detected. And a time domain equalization unit that corrects and corrects the received signal, performs frequency domain equalization, performs time domain equalization, performs FFT processing, and demodulates.

  Patent Document 3 (Japanese Patent Laid-Open No. 2006-157732) describes a technique for improving a symbol determination system by generating a replica of a received signal in consideration of an estimated Doppler shift value. In addition, a technique is described in which symbol determination is repeatedly performed until the maximum likelihood calculated by the likelihood calculating unit is equal to or greater than a predetermined value. Patent Document 4 (Japanese Patent Application Laid-Open No. 2006-196990) describes a technique in which a receiver processes reception signals of reception antennas (four in this case) using an OFDM-MIMO demodulator. In addition, a technique for indicating a received signal by using a matrix representation in the frequency domain and using a transfer function H of a propagation path is described. In addition, it is described that the MLD method is not a method that can be applied only to the multicarrier modulation method, but can be generally applied to single carrier transmission. In addition, a technique for generating a replica signal of a received signal by performing processing such as complex multiplication and addition of a channel estimation signal and a transmission signal is described. Further, a technique is described in which a replica signal is temporarily stored, and a replica signal stored in the replica signal storage circuit is subtracted from the stored received signal.

Akinori Nakajima, Fumiyuki Adachi, “Throughput characteristics of SC-MIMO multiplexing using two-dimensional MMSE weight for frequency domain repetition PIC”, IEICE Technical Report, RCS 2005-88, pp. 19-24, October 2005 Japanese Patent Application Laid-Open No. 2002-247011 Japanese Patent Laid-Open No. 2003-051802 JP 2006-157732 A JP 2006-196990 A

  The reception characteristic is good when the above-described linear processing filter based on the minimum mean square error (MMSE) is used and the method of suppressing interference from transmission antennas other than the transmission antenna to be demodulated is used. It can not be said. In order to improve reception characteristics using this method, a method combining an MMSE filter and transmission antenna interference cancellation has been proposed. Further, a maximum likelihood detection method (MLD: Maximum Likelihood Detection) is considered in which replicas of all transmission antenna signals are generated and the most likely transmission antenna signal is selected. However, although reception characteristics are good, the number of transmission antennas and As the modulation multi-level number increases, the amount of calculation increases exponentially.

  In addition, in the conventional MIMO receiver, by performing two-dimensional frequency domain equalization and antenna interference removal in the frequency domain including channel estimation, the amount of computation is significantly reduced compared to time domain reception processing, and path timing is also improved. It is characterized by not being affected by errors. However, in the conventional MIMO receiving apparatus, it is necessary to repeat two-dimensional frequency domain equalization, error correction decoding, and antenna interference removal processing a plurality of times in order to improve reception characteristics, which increases the amount of computation and demodulation delay. There's a problem. Further, noise enhancement due to MMSE equalization remains even if repeated processing is repeated, and thus there is a problem that it does not reach the reception characteristics of MLD.

  The problem to be solved by the present invention is to convert a single carrier MIMO signal into a frequency domain signal, perform equalization processing and multipath interference cancellation processing, and then perform demodulation by performing MIMO signal separation by MLD in the time domain. An object of the present invention is to provide a MIMO receiver that realizes excellent reception characteristics while suppressing an increase in delay.

  The means for solving the problem will be described below using the numbers used in [Best Mode for Carrying Out the Invention]. These numbers are added to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers should not be used to interpret the technical scope of the invention described in [Claims].

In order to solve the above-mentioned problem, N (M is an integer of 2 or more) single-carrier MIMO signals transmitted from M transmitting antennas are received by N (N is an integer of 2 or more) receiving antennas (1). A MIMO receiver for performing MIMO signal separation,
A DFT section (51) (3) for converting each reception antenna (1) signal into a frequency domain signal, and a channel between the transmission antenna and the reception antenna (1) using a pilot signal inserted for each transmission antenna A channel estimator (52) for estimating the gain; a multipath interference replica regenerator (53) for equalizing the received signal with the weight calculated from the channel gain and generating multipath interference in the equalized signal of each transmitting antenna; A demodulator that equalizes a received signal from a weight calculated in consideration of multipath interference removal from the channel gain, subtracts the multipath interference from the equalized signal of each transmitting antenna, and performs MIMO signal separation by MLD in the time domain (54) is comprised.

  The MIMO receiver further includes a K-stage (K is an integer equal to or greater than 1) multi-path interference replica reproduction section (55) following the multi-path interference replica reproduction section (53). It is preferable to perform replica reproduction repeatedly.

  In the MIMO receiving apparatus, the multipath interference replica reproduction unit (53) calculates a weight for frequency domain equalization from a channel gain between the transmission antenna and the reception antenna (1). Frequency domain for performing MIMO signal separation and multipath interference suppression in the frequency domain by inputting the weight and the signal output from the DFT unit (51) (3) and multiplying each of them by subcarriers An equalization unit (7), an IDFT unit (9) for converting an equalization signal of each transmission antenna, which is a signal output from the frequency domain equalization unit (7), into a time domain signal, and the IDFT unit ( 9) a bit likelihood calculating unit (12) for calculating the likelihood for each bit transmitted from the output signal, and a symbol for generating a symbol replica based on the bit likelihood. A replica generation unit (14), a DFT unit (15) that converts the symbol replica into a frequency domain signal, and a multipath interference replica that generates a multipath interference replica using the frequency domain symbol replica signal and the channel gain It is preferable to provide a production | generation part (16).

  In the MIMO receiver, the demodulator (54) calculates a weight for frequency domain equalization in consideration of multipath interference removal from a channel gain between the transmitting antenna and the receiving antenna (1). Unit (6), the weight and the signal output from the DFT unit (51) (3) are input and multiplied for each subcarrier, thereby performing MIMO signal separation and multipath interference suppression in the frequency domain. A frequency domain equalization unit (7) that performs the above, an IDFT unit (9) that converts an equalized signal of each transmission antenna, which is a signal output from the frequency domain equalization unit (7), into a time domain signal, An error for selecting the most probable transmit antenna symbol candidate by comparing the output signal of the IDFT unit (9) with the received replicas of all transmit antenna symbol candidates An MLD (11) that performs an arithmetic operation, and a bit likelihood calculation unit (12) that selects a symbol candidate with a minimum error from an error signal that is an output of the MLD (11) and calculates a likelihood for each transmitted bit. It is preferable to provide.

  In the MIMO receiving apparatus, each of the K-stage multipath interference replica reproduction unit (55) takes into account multipath interference removal from the channel gain between the transmission antenna and the reception antenna (1), and is in a frequency domain. The weight calculation unit (6) for calculating the equalization weight, and the weight and the signal output from the DFT unit (51) (3) are input, and each is multiplied for each subcarrier in the frequency domain. A frequency domain equalization unit (7) that performs MIMO signal separation and multipath interference suppression, and an equalized signal of each transmission antenna that is a signal output from the frequency domain equalization unit (7) is converted into a time domain signal Comparing the output signal of the IDFT unit (9) and the IDFT unit (9) with the reception replicas of all transmission antenna symbol candidates, MLD (11) that performs error calculation for selecting a symbol candidate, and a bit that calculates a likelihood for each transmitted bit by selecting a symbol candidate with the smallest error from an error signal that is an output of the MLD (11) A likelihood calculating unit (12), a symbol replica generating unit (14) for generating a symbol replica based on the bit likelihood, a DFT unit (51) for converting the symbol replica into a frequency domain signal, and a frequency domain Preferably, a multipath interference replica generation unit (16) that generates a multipath interference replica using the symbol replica signal and the channel gain is provided.

  In the MIMO receiving apparatus, the multipath interference replica reproduction unit (53) further includes an MLD (11) subsequent to the IDFT unit (9), and performs high-precision MIMO signal separation by the MLD (11). preferable.

  In the MIMO receiver, the multipath interference replica reproduction unit (53) further includes a decoder (13) subsequent to the bit likelihood calculation unit (12), and generates a symbol replica using the error-corrected decoded bits. It is preferable to do.

  In the MIMO receiver, each of the K-stage multipath interference replica reproduction unit (55) further includes a decoder (13) subsequent to the bit likelihood calculation unit (12), and uses the error-corrected decoded bits. It is preferable to generate a symbol replica.

  In the MIMO receiving apparatus, the multipath interference replica reproduction unit (53) (55) further includes a whitening filter (10) before the MLD (11), and outputs each output signal of the IDFT unit (9). It is preferable to perform MLD (11) after making noise uncorrelated.

  In the MIMO receiver, the demodulator (54) further includes a whitening filter (10) in front of the MLD (11), and makes noise of each output signal of the IDFT unit (9) uncorrelated. It is preferable to perform MLD (11).

  In the MIMO receiving apparatus, each of the K-stage multipath interference replica reproduction unit (55) further includes a whitening filter (10) in front of the MLD (11), and each output of the IDFT unit (9). It is preferable to perform MLD (11) after making signal noise uncorrelated.

  In the MIMO receiver, the symbol replica generation unit (14) preferably uses a hard decision replica or a soft decision replica as the symbol replica.

In order to solve the above problems, N (M is an integer of 2 or more) single carrier MIMO signals transmitted from M transmission antennas (M is an integer of 2 or more) are received by N (N is an integer of 2 or more) receiving antennas (1). A MIMO reception method for performing MIMO signal separation,
A process of converting each receiving antenna (1) signal into a frequency domain signal, a process of estimating a channel gain between the transmitting antenna and the receiving antenna (1) using a pilot signal inserted for each transmitting antenna; The received signal is equalized by the weight calculated from the channel gain, multipath interference is generated in the equalized signal of each transmitting antenna, and the received signal is calculated by the weight calculated in consideration of multipath interference removal from the channel gain. A MIMO reception method is performed that includes equalizing, subtracting multipath interference from the equalized signal of each transmit antenna, and performing MIMO signal separation with MLD (11) in the time domain.

  In the MIMO receiver of the present invention, a single carrier MIMO signal is converted to a frequency domain signal, equalization processing and multipath interference cancellation processing are performed, and then MIMO signal separation is performed by MLD in the time domain, thereby reducing demodulation delay. Excellent reception characteristics can be realized while suppressing the increase.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram illustrating the configuration of the MIMO receiving apparatus of this embodiment. The MIMO receiving apparatus of this embodiment receives single carrier MIMO signals transmitted from M (M is an integer of 2 or more) transmission antennas by N (N is an integer of 2 or more) reception antennas, and has a frequency. MIMO signal separation is performed by area signal processing.

  Referring to FIG. 5, the MIMO receiving apparatus of the present embodiment includes a plurality of receiving antennas 1 (first receiving antenna 1-1 to Nth receiving antenna 1-N), a DFT unit 51, a channel estimation unit 52, A multipath interference replica reproduction unit 53 and a demodulation unit 54 are included.

The DFT unit 51 performs DFT on the reception signals of the first reception antenna 1-1 to the Nth reception antenna 1-N at N _DFT1 (N _DFT1 is an integer of 2 or more) points.

  The channel estimation unit 52 estimates the channel gain between the transmission antenna and the reception antenna using the pilot signal inserted for each transmission antenna. The multipath interference replica reproduction unit 53 equalizes the received signal with the weight calculated from the channel gain, and generates a multipath interference replica in the equalized signal of each transmission antenna. The multipath interference replica reproduction unit 53 may be configured to convert the signal after two-dimensional frequency domain equalization into the time domain, and to perform highly accurate MIMO signal separation by MLD.

  The demodulation unit 54 equalizes the received signal with the weight calculated considering the multipath interference removal from the channel gain, subtracts the multipath interference from the equalized signal of each transmitting antenna, and performs MLD in the time domain. Perform MIMO signal separation. In the MIMO receiving apparatus of the present embodiment, the demodulation delay increases by performing MIMO signal separation by MLD in the time domain after performing multipath interference cancellation of each transmission antenna signal after the demodulation unit 54 performs two-dimensional frequency domain equalization. It is possible to realize excellent reception characteristics while suppressing noise.

  FIG. 6 is a block diagram illustrating another configuration of the MIMO receiving apparatus of this embodiment. In the MIMO receiving apparatus according to another embodiment, a K-stage (K is an integer of 1 or more) multi-path interference replica reproduction section 55 (first multi-path interference reproduction section 55) is provided after the multi-path interference replica reproduction section 53 of the above-described embodiment. Path interference replica reproduction unit 55-1 to K-th multipath interference replica reproduction unit 55-K). As described above, the MIMO reception apparatus receives single carrier MIMO signals transmitted from M (M is an integer of 2 or more) transmission antennas by N (N is an integer of 2 or more) reception antennas, MIMO signal separation is performed by frequency domain signal processing.

  In another embodiment, the MIMO receiver includes a plurality of reception antennas 1 (first reception antenna 1-1 to Nth reception antenna 1-N), a DFT unit 51, a channel estimation unit 52, and multipath interference. The replica reproduction unit 53 includes a plurality of multipath interference replica reproduction units 55 (first multipath interference replica reproduction unit 55-1 to Kth multipath interference replica reproduction unit 55-K), and a demodulation unit 54. Has been. The configurations of the DFT unit 51, the channel estimation unit 52, and the multipath interference replica reproduction unit 53 are the same as those in the above-described embodiment. Therefore, in the following, description will be made corresponding to the different points from the above-described embodiment.

  The multipath interference replica reproduction unit 55 (the first multipath interference replica reproduction unit 55-1 to the Kth multipath interference replica reproduction unit 55-K) has weights calculated in consideration of multipath interference removal from the channel gain, respectively. The received signal is equalized in a two-dimensional frequency domain, multipath interference is subtracted from the equalized signal of each transmitting antenna, MIMO signal separation is performed by MLD in the time domain, and a multipath interference replica in the equalized signal of each transmitting antenna is Generate.

  The demodulation unit 54 equalizes the received signal with the weight calculated considering the multipath interference removal from the channel gain, subtracts the multipath interference from the equalized signal of each transmitting antenna, and performs MLD in the time domain. Perform MIMO signal separation.

  In the MIMO receiver according to another embodiment, the demodulation unit 54 performs demodulation of multipath interference after the two-dimensional frequency domain equalization, and then performs MIMO signal separation by MLD in the time domain, thereby reducing demodulation delay. Excellent reception characteristics can be realized while suppressing the increase. In addition, since it is possible to generate a highly accurate replica by repeating multipath interference replica reproduction and multipath interference cancellation, it is possible to further improve the MIMO reception characteristics.

  Next, a detailed configuration and operation of the MIMO receiving apparatus according to the present embodiment will be described with reference to FIGS. 7A and 7B. FIG. 7A illustrates the configuration of the previous stage of the MIMO receiving apparatus of this embodiment. FIG. 7B illustrates the configuration of the latter stage of the MIMO receiving apparatus of this embodiment. The MIMO receiver of this embodiment includes a plurality of receiving antennas 1 (first receiving antenna 1-1 to Nth receiving antenna 1-N) and a plurality of CP removing units 2 (first CP removing unit 2-1 to NCPth. Removing section 2-N), a plurality of DFT sections 3 (first DFT section 3-1 to NDFT section 3-N), and a plurality of reception filters 4 (first reception filter 4-1 to N-th reception filter 4- N), a channel estimation unit 5, a weight calculation unit 6, a two-dimensional frequency domain equalization unit 7, a subtraction unit 8, and a plurality of IDFT units 9 (first IDFT unit 9-1 to MIDFT unit 9-M). ), Whitening filter 10, MLD unit 11, a plurality of bit likelihood calculation units 12 (first bit likelihood calculation unit 12-1 to M-th bit likelihood calculation unit 12 -M), and a plurality of decodings A first decoder 13-1 to an Mth decoder 13-M, and a plurality of symbol readers Rica generation unit 14 (first symbol replica generation unit 14-1 to M-th symbol replica generation unit 14-M), a plurality of DFT units 15 (first DFT unit 15-1 to MDFT unit 15-M), a plurality Multipath interference replica generation unit 16 (first multipath interference replica generation unit 16-1 to M-th multipath interference replica generation unit 16-M).

The plurality of receiving antennas 1 (first receiving antenna 1-1 to Nth receiving antenna 1-N) receive a single carrier MIMO signal. A plurality of CP removal units 2 (first CP removal unit 2-1 to NCP removal unit 2-N) input each reception antenna signal and remove a signal corresponding to a CP at a common timing. A plurality of DFT units 3 (the first DFT unit 3-1 to the NDFT unit 3-N) receive each received antenna signal from which CP is removed and perform DFT of N _DFT1 (N _DFT1 is an integer of 2 or more) points. The received signal is converted into a frequency domain signal.

  The plurality of reception filters 4 (first reception filter 4-1 to Nth reception filter 4-N) perform filtering of reception signals in the frequency domain, and perform noise suppression and user separation. A raised cosine roll-off filter is generally used for the plurality of reception filters 4 (first reception filter 4-1 to N-th reception filter 4-N) (including a roll-off rate of 0). 7A and 7B, the plurality of reception filters 4 (the first reception filter 4-1 to the Nth reception filter 4-N) are performed by frequency domain signal processing. Prior to the processing in (first DFT unit 3-1 to NDFT unit 3-N), it can also be performed by signal processing in the time domain. The channel estimation unit 5 estimates the channel gain between the transmission antenna and the reception antenna in the frequency domain using the pilot signal inserted for each transmission antenna.

  Here, the channel estimation unit 5 for obtaining the channel gain of the transmission antenna m in the reception antenna n will be described. FIG. 8 is a block diagram illustrating the configuration of the channel estimation unit 5. The channel estimation unit 5 includes a DFT unit 61, a transmission / reception filter 62, a reference signal generation unit 63, a correlation processing unit 64, and a noise suppression unit 65.

  The DFT unit 61 performs DFT on the pilot code of the transmission antenna m and converts it to a frequency domain signal. The transmission / reception filter 62 passes the signal in the frequency domain of the pilot code through the transmission / reception filter. The reference signal generator 63 uses the output of the transmission / reception filter 62 to calculate a pilot reference signal used for correlation processing with the received pilot signal. The reference signal generation unit 63 uses a zero forcing method that completely cancels the sign characteristics of the pilot reception signal, or an MMSE or clipping method that suppresses noise enhancement in correlation processing.

  The correlation processing unit 64 estimates the channel gain by correlation processing between the frequency domain pilot received signal and the pilot reference signal. The noise suppression unit 65 suppresses channel gain noise estimated by the correlation processing unit 64 and improves the signal power to noise power ratio (S / N) of the channel estimation value. The noise suppression unit 65 includes a method of averaging adjacent subcarriers, a method of converting a channel estimation value into a time-domain channel response once by IDFT, and returning to the frequency domain by DFT after removing a noise path.

  7A and 7B, the channel estimation unit 5 performs the frequency domain signal processing. However, the channel estimation unit 5 may perform the time domain signal processing prior to the first DFT unit 3-1 to the NDFT unit 3-N. it can.

とすると、送信アンテナｍの第ｉ繰り返しＭＭＳＥウエイトは、チャネル推定値行列

と、雑音電力

とを用いて、次式で計算される。

The weight calculation unit 6 calculates the weight of the two-dimensional frequency domain equalization using the channel gain between the transmission antenna and the reception antenna. The weight calculation unit 6 generally uses an MMSE algorithm. I-th repeated MMSE weight of transmit antenna m

Then, the i-th iterative MMSE weight of the transmission antenna m is the channel estimation value matrix

And noise power

And is calculated by the following equation.

はＮ列の行ベクトルであり、

はＮ行Ｍ列の行列であるものとする。ここで、

で表される。また、

は、送信アンテナｍと受信アンテナとの間のチャネル推定値である。なお、

はＮ行の列ベクトルであるものとする。 In addition,

Is an N column row vector,

Is a matrix of N rows and M columns. here,

It is represented by Also,

Is the channel estimate between the transmit antenna m and the receive antenna. In addition,

Let N be a column vector of N rows.

は第ｉ繰り返し干渉除去考慮行列であり、全ての送信アンテナに対して共通となり次式で表される。

ここで、

は、例えば、送信アンテナｍの時間領域の第ｉ繰り返し軟判定シンボルレプリカ

の平均電力を用いて次式で計算される。

Also, the equation (9)

Is an i-th iterative interference cancellation consideration matrix, which is common to all transmission antennas and is expressed by the following equation.

here,

Is, for example, the i-th iterative soft decision symbol replica in the time domain of the transmission antenna m.

Using the average power of

は、初回（ｉ＝０）では単位行列である。式（９）のウエイト計算において［・］^−１の計算は送信アンテナｍに対して共通であり１度だけ行えばよく、従来と比べ演算量を削減できる。２次元周波数領域等化部７は、ウエイト計算部６で計算した２次元等化ウエイトおよび第１受信フィルタ４−１〜第Ｎ受信フィルタ４−Ｎの出力を入力とし、それぞれをサブキャリア毎に乗じることにより、周波数領域でＭＩＭＯ信号分離とマルチパス干渉抑圧を同時に行う。 Here, N _SYMB is the number of symbols in the data block. Also,

Is a unit matrix at the first time (i = 0). In the weight calculation of Expression (9), the calculation of [·] ⁻¹ is common to the transmission antenna m and needs to be performed only once. The two-dimensional frequency domain equalization unit 7 receives the two-dimensional equalization weight calculated by the weight calculation unit 6 and the outputs of the first reception filter 4-1 to the Nth reception filter 4-N as input, and each of them is sub-carrier-based. By multiplying, MIMO signal separation and multipath interference suppression are simultaneously performed in the frequency domain.

とし、第１受信フィルタ４−１〜第Ｎ受信フィルタ４−Ｎの出力を

とすると、２次元周波数領域等化部７で２次元等化した送信アンテナｍの等化信号

は、次式で表される。

The weight calculated by the weight calculator 6

And outputs of the first reception filter 4-1 to the Nth reception filter 4-N.

Then, the equalized signal of the transmission antenna m that has been two-dimensionally equalized by the two-dimensional frequency domain equalization unit 7

Is expressed by the following equation.

とすると、送信アンテナｍの第ｉ繰り返し出力信号

は次式で表される。

The subtracting unit 8 subtracts multipath interference of all transmission antennas from the equalized signal of each transmission antenna. Multipath interference removal in the frequency domain corresponds to a process of flattening a frequency spectrum by adding and subtracting a multipath interference replica to an equalized signal in the frequency domain. Multipath interference replica in equalized signal of transmit antenna m

Then, the i-th repeated output signal of the transmitting antenna m

Is expressed by the following equation.

  7A and 7B, the multipath interference replica is subtracted in the subsequent stage of the two-dimensional frequency domain equalization unit 7 in the subtraction unit 8, but weight correction is performed on the multipath interference replica to obtain the two-dimensional frequency domain. An equivalent configuration in which subtraction is performed in the preceding stage of the equalization unit 7 can also be considered. The first IDFT unit 9-1 to the MIDFT unit 9-M receive the equalized signal of each transmission antenna, which is the output of the two-dimensional frequency domain equalizing unit 7, as input, and IDFT of NIDFT (NIDFT is an integer of 2 or more) points. To convert the equalized signal into a time domain signal. Here, if there is a correlation in the noise of the equalized signal of each transmitting antenna, the maximum likelihood characteristic cannot be realized in the MLD. The whitening filter 10 performs a linear operation on the equalized signal of each transmission antenna to make the noise included in each signal uncorrelated.

とすると、白色化フィルタ行列

は次式を満足すればよい。

Time domain equalization filter matrix

Then the whitening filter matrix

Should satisfy the following equation.

の固有値行列を

とし、固有ベクトル行列を

とすると、白色化フィルタ

は次式で表される。

なお、時間領域の等化ウエイト

は周波数領域の等化ウエイトをＩＤＦＴして求めることができる。また、特性は劣化するが白色化フィルタ１０を省略した構成も考えられる。 Where the correlation matrix

The eigenvalue matrix of

And the eigenvector matrix is

Then, the whitening filter

Is expressed by the following equation.

Time domain equalization weight

Can be obtained by IDFT of equalization weights in the frequency domain. In addition, a configuration in which the whitening filter 10 is omitted although the characteristics deteriorate may be considered.

を用いて計算される。ここで、

は周波数領域の等化後チャネル利得を時間領域へ変換して求められ（ＩＤＦＴ出力の第０ポイント）、その要素

は次式で計算される。

ここで、

は、２次元周波数領域等化後チャネル利得のサブキャリア平均値である。 The MLD unit 11 compares the equalized / whitened signal and the reception replicas of all the transmission antenna signals, and calculates an error for selecting the most likely transmission antenna symbol candidate. MLD receive replica is receive replica generator matrix

Is calculated using here,

Is obtained by converting the channel gain after frequency domain equalization to the time domain (0th point of the IDFT output), and its elements

Is calculated by the following equation.

here,

Is a subcarrier average value of channel gain after two-dimensional frequency domain equalization.

  Here, the MLD unit 11 will be described. FIG. 9 is a block diagram illustrating the configuration of the MLD unit 11. The MLD unit 11 includes a symbol candidate generation unit 71, a reception replica generation unit 72, and an error signal calculation unit 73.

  The symbol candidate generation unit 71 generates symbol candidates for all transmission antennas. The reception replica generation unit 72 generates a reception replica by multiplying the symbol candidate and the reception replica generation matrix. The error signal calculator 73 compares the equalized / whitened signal with the received replica, and calculates a square Euclidean error.

  The MLD unit 11 can also use a computational complexity reduction type MLD using QR decomposition / M algorithm, sphere decoding, or the like, instead of Full-MLD (MLD for calculating errors of all symbol candidates).

  The first bit likelihood calculation unit 12-1 to the M-th bit likelihood calculation unit 12-M select a symbol candidate with the smallest error from the output error signal of the MLD unit 11, and calculate the likelihood for each transmitted bit. To do. The output signal of the i-th repetition (i ≧ 1) of the first bit likelihood calculation unit 12-1 to the M-th bit likelihood calculation unit 12-M is a final bit demodulated signal. The first decoder 13-1 to the M-th decoder 13-M receive the bit likelihood of each transmission antenna signal and perform error correction decoding. A turbo code or a convolutional code is used as the error correction code. The first symbol replica generation unit 14-1 to the M-th symbol replica generation unit 14-M generate symbol replicas from the decoded bits of each transmission antenna signal. The first symbol replica generation unit 14-1 to the M-th symbol replica generation unit 14-M generate a hard decision symbol replica, a hard decision symbol replica, and a predetermined replica weight coefficient (a constant equal to or less than 1). There are a method of multiplication, a method of generating a soft decision symbol replica, and the like, and a method of generating a soft decision symbol replica has good characteristics. The first DFT unit 15-1 to the MDFT unit 15-M receive the symbol replicas of the transmission antennas generated by the first symbol replica generation unit 14-1 to the M-th symbol replica generation unit 14-M as inputs, and use NDFT2 (NDFT2 Is an integer greater than or equal to 2) and performs a DFT of the points to convert the symbol replica into a frequency domain signal. The first multipath interference replica generation unit 16-1 to the M-th multipath interference replica generation unit 16-M use the frequency domain symbol replica signal of each transmission antenna, the equalization weight and the channel gain, etc. A multipath interference replica in the digitized signal is generated.

とし、等化ウエイトを

とし、チャネル推定値を

とすると、送信アンテナｍの第i繰り返しマルチパス干渉レプリカ

は、全ての送信アンテナのマルチパス干渉の和で表される。

本発明のＭＩＭＯ受信装置では、全ての送信アンテナ信号のマルチパス干渉除去を考慮し、２次元等化ウエイトを計算するため、レプリカ精度が向上すれば等化ウエイトは所望の送信アンテナ信号に対して最大比合成ウエイトに収束し、他アンテナ干渉とマルチパス干渉は抑圧しなくなる。そのとき、本発明のＭＩＭＯ受信装置では、各送信アンテナ信号を最大比合成受信し、マルチパス干渉の除かれた状態でＭＬＤを行う動作となり、最尤特性が実現できる。 The symbol replica signal in the frequency domain of the transmitting antenna m

And the equalization weight

And the channel estimate is

Then, the i-th repeated multipath interference replica of the transmitting antenna m

Is represented by the sum of multipath interference of all transmission antennas.

In the MIMO receiving apparatus of the present invention, since the two-dimensional equalization weight is calculated in consideration of multipath interference cancellation of all transmission antenna signals, if the replica accuracy is improved, the equalization weight is obtained with respect to a desired transmission antenna signal. It converges to the maximum ratio combining weight, and other antenna interference and multipath interference are not suppressed. At that time, in the MIMO receiving apparatus of the present invention, the maximum ratio combining reception of each transmission antenna signal is performed, and the MLD is performed in a state where multipath interference is removed, and the maximum likelihood characteristic can be realized.

  In the present embodiment, the conversion from the time domain signal to the frequency domain signal is performed by DFT, and the conversion from the frequency domain signal to the time domain signal is performed by IDFT, but fast Fourier transform (FFT), fast inverse A Fourier transform (IFFT: Inverse Fast Fourier Transform) or other algorithms may be used.

FIG. 1 is a diagram showing a configuration of a conventional MIMO transmission / reception system using MIMO multiplexing. FIG. 2 is a diagram illustrating a configuration of a conventional MIMO receiving apparatus. FIG. 3 is a diagram illustrating an example of a radio frame format when frequency domain equalization is used. FIG. 4 is a diagram illustrating a configuration of a subtracting unit of a conventional MIMO receiving apparatus. FIG. 5 is a block diagram illustrating the configuration of the MIMO receiving apparatus of this embodiment. FIG. 6 is a block diagram illustrating another configuration of the MIMO receiving apparatus of this embodiment. FIG. 7A is a block diagram illustrating the configuration of the previous stage of the MIMO receiving apparatus of this embodiment. FIG. 7B is a block diagram illustrating the configuration of the latter stage of the MIMO receiving apparatus of this embodiment. FIG. 8 is a block diagram illustrating the configuration of the channel estimation unit 5. FIG. 9 is a block diagram illustrating the configuration of the MLD unit 11.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reception antenna 1-1 ... 1st reception antenna 1-N ... Nth reception antenna 51 ... DFT part 52 ... Channel estimation part 53 ... Multipath interference replica reproduction | regeneration part 54 ... Demodulation part 55 ... Multipath interference replica reproduction | regeneration part 55 -1 ... first multipath interference replica reproduction unit 55-K ... Kth multipath interference replica reproduction unit 2 ... CP removal unit 2-1 ... first CP removal unit 2-N ... NCP removal unit 3 ... DFT unit 3- DESCRIPTION OF SYMBOLS 1 ... 1st DFT part 3-N ... NDFT part 4 ... Reception filter 4-1 ... 1st reception filter 4-N ... Nth reception filter 5 ... Channel estimation part 6 ... Weight calculation part 7 ... Two-dimensional frequency domain equalization Unit 8 ... Subtracting unit 9 ... IDFT unit 9-1 ... First IDFT unit 9-M ... MIDFT unit 10 ... Whitening filter 11 ... MLD unit 12 ... Bit likelihood calculating unit 12-1 ... First bit likelihood calculating unit 12-M ... M Likelihood likelihood calculation unit 13 ... decoder 13-1 ... first decoder 13 -M ... M-th decoder 14 ... symbol replica generation unit 14-1 ... first symbol replica generation unit 14 -M ... M-th symbol replica Generation unit 15 ... DFT unit 15-1 ... first DFT unit 15-M ... MDFT unit 16 ... multipath interference replica generation unit 16-1 ... first multipath interference replica generation unit 16-M ... Mth multipath interference replica Generation unit 61 ... DFT unit 62 ... transmission / reception filter 63 ... reference signal generation unit 64 ... correlation processing unit 65 ... noise suppression unit 71 ... symbol candidate generation unit 72 ... reception replica generation unit 73 ... error signal calculation unit 101 ... reception antenna 101- DESCRIPTION OF SYMBOLS 1 ... 1st receiving antenna 101-N ... Nth receiving antenna 102 ... Cyclic prefix (CP: Cyclic Prefix) removal part 102-1 ... 1st CP removal part 102-N NCP removing unit 103 ... Discrete Fourier Transform (DFT) unit 103-1 ... first DFT unit 103-N ... NDFT unit 104 ... reception filter 104-1 ... first reception filter 104-N ... Nth reception Filter 105 ... Subtraction unit 106 ... Channel estimation unit 107 ... Weight calculation unit 108 ... Two-dimensional frequency domain equalization unit 109 ... Discrete inverse Fourier transform (IDFT) unit 109-1 ... First IDFT unit 109-M ... MIDFT unit 110 ... bit likelihood calculation unit 110-1 ... first bit likelihood calculation unit 110-M ... Mth bit likelihood calculation unit 111 ... decoder 111-1 ... first decoder 111-M ... M Decoder 112 ... symbol replica generator 112-1 ... first symbol replica generator 112 -M ... M th symbol replica generator 113 ... DFT 113-1 ... 1st DFT unit 113-M ... MDFT unit 114 ... Transmission / reception filter 114-1 ... 1st transmission / reception filter 114-M ... M-th transmission / reception filter 115 ... Antenna interference replica generation unit 115-1 ... 1st antenna interference replica Generation unit 115-M ... M-th antenna interference replica generation unit 121 ... Replica synthesis unit 121-1 ... First replica synthesis unit 121-M ... M-th replica synthesis unit 122 ... Subtractor 122-1 ... First subtractor 122- M ... Mth subtractor 201 ... transmitting device 202 ... transmitting antenna 202-1 ... first transmitting antenna 202-M ... Mth transmitting antenna 203 ... receiving antenna 203-1 ... first receiving antenna 203-N ... Nth receiving antenna 204: Receiver

Claims (13)

A MIMO receiving apparatus that receives single carrier MIMO signals transmitted from M (M is an integer of 2 or more) transmission antennas by N (N is an integer of 2 or more) reception antennas and performs MIMO signal separation. ,
A DFT unit for converting each receiving antenna signal into a frequency domain signal;
A channel estimation unit for estimating a channel gain between the transmission antenna and the reception antenna using a pilot signal inserted for each transmission antenna;
A multipath interference replica regenerator that equalizes the received signal with the weight calculated from the channel gain and generates multipath interference in the equalized signal of each transmit antenna;
A demodulator that equalizes a received signal with a weight calculated in consideration of multipath interference removal from the channel gain, subtracts the multipath interference from the equalized signal of each transmitting antenna, and performs MIMO signal separation by MLD in the time domain; A MIMO receiver. The multi-path interference replica reproduction section further includes a K-stage (K is an integer of 1 or more) multi-path interference replica reproduction section after the multi-path interference replica reproduction section, and repeats multi-path interference removal and replica reproduction. 2. The MIMO receiver according to 1. The multi-path interference replica reproduction unit is
A weight calculation unit for calculating a weight of frequency domain equalization from a channel gain between the transmission antenna and the reception antenna;
A frequency domain equalization unit that performs MIMO signal separation and multipath interference suppression in the frequency domain by inputting the weight and the signal output from the DFT unit and multiplying each signal by subcarriers,
An IDFT unit that converts an equalized signal of each transmission antenna, which is a signal output from the frequency domain equalization unit, into a signal in the time domain;
A bit likelihood calculation unit for calculating likelihood for each bit transmitted from the output signal of the IDFT unit;
A symbol replica generation unit that generates a symbol replica based on the bit likelihood;
A DFT unit for converting the symbol replica into a frequency domain signal;
The MIMO receiving apparatus according to claim 1, further comprising: a multipath interference replica generation unit that generates a multipath interference replica using a frequency domain symbol replica signal and a channel gain. The demodulator
A weight calculation unit for calculating a weight of frequency domain equalization in consideration of multipath interference removal from a channel gain between the transmission antenna and the reception antenna;
A frequency domain equalization unit that performs MIMO signal separation and multipath interference suppression in the frequency domain by inputting the weight and the signal output from the DFT unit and multiplying each signal by subcarriers,
An IDFT unit that converts an equalized signal of each transmission antenna, which is a signal output from the frequency domain equalization unit, into a signal in the time domain;
An MLD that compares the output signal of the IDFT unit with received replicas of all transmit antenna symbol candidates and performs error calculation to select the most probable transmit antenna symbol candidates;
The MIMO reception according to claim 1, further comprising: a bit likelihood calculation unit that selects a symbol candidate with a minimum error from an error signal that is an output of the MLD and calculates a likelihood for each transmitted bit. apparatus. Each of the K-stage multipath interference replica reproduction units is
A weight calculation unit for calculating a weight of frequency domain equalization in consideration of multipath interference removal from a channel gain between the transmission antenna and the reception antenna;
A frequency domain equalization unit that performs MIMO signal separation and multipath interference suppression in the frequency domain by inputting the weight and the signal output from the DFT unit, and multiplying each signal by subcarrier,
An IDFT unit that converts an equalized signal of each transmission antenna, which is a signal output from the frequency domain equalization unit, into a signal in the time domain;
An MLD that compares the output signal of the IDFT unit with received replicas of all transmit antenna symbol candidates and performs error calculation to select the most probable transmit antenna symbol candidates;
A bit likelihood calculating unit that selects a symbol candidate with a minimum error from an error signal that is an output of the MLD and calculates a likelihood for each transmitted bit;
A symbol replica generation unit that generates a symbol replica based on the bit likelihood;
A DFT unit for converting the symbol replica into a frequency domain signal;
The MIMO reception apparatus according to claim 2, further comprising: a multipath interference replica generation unit that generates a multipath interference replica using a frequency domain symbol replica signal and a channel gain. The multi-path interference replica reproduction unit is
4. The MIMO receiving apparatus according to claim 3, further comprising an MLD at a subsequent stage of the IDFT unit, and performing highly accurate MIMO signal separation by the MLD. The multi-path interference replica reproduction unit is
The MIMO receiving apparatus according to claim 3, further comprising a decoder at a stage subsequent to the bit likelihood calculating unit, and generating a symbol replica using the bits subjected to error correction decoding. Each of the K-stage multipath interference replica reproduction units is
The MIMO receiving apparatus according to claim 5, further comprising a decoder at a stage subsequent to the bit likelihood calculating unit, and generating a symbol replica using bits subjected to error correction decoding. The multi-path interference replica reproduction unit is
4. The MIMO receiving apparatus according to claim 3, further comprising a whitening filter in a previous stage of the MLD, and performing MLD after making noise of each output signal of the IDFT unit uncorrelated. 5. The demodulator
The MIMO receiving apparatus according to claim 4, further comprising a whitening filter in front of the MLD, and performing MLD after making noise of each output signal of the IDFT unit uncorrelated. Each of the K-stage multipath interference replica reproduction units is
The MIMO receiving apparatus according to claim 5, further comprising a whitening filter in a preceding stage of the MLD, and performing MLD after making noise of each output signal of the IDFT unit uncorrelated. The symbol replica generation unit
The MIMO receiving apparatus according to claim 3, wherein a hard decision replica or a soft decision replica is used as the symbol replica. A MIMO reception method for receiving MIMO single-carrier MIMO signals transmitted from M (M is an integer of 2 or more) transmission antennas by N (N is an integer of 2 or more) reception antennas and performing MIMO signal separation. ,
A process of converting each receiving antenna signal into a frequency domain signal;
A process of estimating a channel gain between the transmission antenna and the reception antenna using a pilot signal inserted for each transmission antenna;
A process of equalizing the received signal by the weight calculated from the channel gain and generating multipath interference in the equalized signal of each transmitting antenna;
A process of equalizing a received signal by a weight calculated in consideration of multipath interference removal from the channel gain, subtracting multipath interference from the equalized signal of each transmitting antenna, and performing MIMO signal separation by MLD in the time domain; A MIMO reception method.

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