JP2011049765A - Radio receiver, radio receiving method, and radio reception program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain satisfactory receiving characteristics by reducing the influence of a division error due to multipath division. <P>SOLUTION: In this receiver which generates a replica of a received signal on the basis of a demodulated modulation symbol, eliminates the replica of the received signal other than a corresponding path from the received signal in each path or each of a plurality of paths, synthesizes the signals with the replica eliminated therefrom on the basis of information showing the propagation path states of each path or each of the plurality of paths, repeats demodulating a synthesized signal of the synthesis result and extracts transmission data, a selecting part b114 selects whether to perform signal addition processing for adding eliminated replica components to the signal with the replica eliminated on the basis of signal quality information showing the quality of the synthesized signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless reception device, a wireless reception method, and a wireless reception program.

In wireless communication, in particular, in the case of broadband transmission, in addition to the path received in advance, there is a path that arrives with a delay, such as through reflection from an obstacle such as a building or a mountain, and intersymbol interference ( ISI: Inter Symbol Interference (ISI). An environment in which a plurality of paths arrives in this way is called a multipath environment. For example, OFDM (Orthogonal Frequency Division Multiplexing), OFDMA (Orthogonal Frequency Division Multiple Access), MC-CDM (Multi Carrier-Code Diving, etc.) If the delay path is within GI, ISI is prevented from occurring. However, when there is a delay path exceeding the GI, in addition to ISI, the periodicity of FFT (Fast Fourier Transform) is destroyed, so that ICI (Inter-Carrier Interference) also occurs. ISI and ICI significantly degrade reception performance.
Patent Document 1 and Non-Patent Document 1 describe a technique that can obtain good reception characteristics even when ISI or ICI occurs. These techniques divide a multipath by generating a replica of a delay path from a bit log likelihood ratio (LLR) of an error correction decoding result and removing the replica from the received signal. A path diversity effect can be obtained by dividing the block into a plurality of suppressed blocks and combining the signals of the respective blocks.

International Publication No. 2007/136056 Pamphlet

K. Shimezawa, T .; Yoshimoto, R.A. Yamada, N .; Okamoto, “A novel SC / MMSE turbo equalization for multi-carrier system with insulative cyclic prefix”, IEEE PIMRC. 2008, September 2008

  However, in the techniques described in Patent Document 1 and Non-Patent Document 1, since a multipath is divided by generating a replica and removing it from a received signal, a division error occurs due to this division. These techniques have a problem in that good reception characteristics may not be obtained due to the influence of the division error.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a receiving apparatus capable of reducing the influence of division error due to multipath division and obtaining good reception characteristics.

  (1) The present invention has been made to solve the above problems, and the present invention generates a replica of a received signal based on a demodulated modulation symbol, and for each of one or a plurality of paths other than the path. It repeats removing the replica of the received signal from the received signal, synthesizing the signal from which the replica has been removed based on the information indicating the propagation path status of each of the one or more paths, and demodulating the resultant synthesized signal Whether or not to perform signal addition processing for adding the component of the removed replica to the signal from which the replica has been removed based on signal quality information indicating the quality of the combined signal in the wireless reception device that extracts transmission data It is a radio | wireless receiver characterized by including the selection part which selects these.

  (2) Further, according to the present invention, in the above-described wireless reception device, when the signal quality information indicates that the quality is low, the selection unit selects to perform the signal addition processing and performs the removal. It is characterized by reducing errors that occur.

  (3) Further, the present invention is characterized in that, in the above-described radio reception apparatus, the selection unit selects not to perform the signal addition processing when the signal quality information indicates high quality. .

  (4) Further, according to the present invention, in the above-described wireless reception device, the selection unit does not perform the signal addition process and the first method for performing the signal addition process at least once in the repetition process. The second mode is switched.

  (5) Moreover, the present invention is characterized in that, in the above-described radio receiving apparatus, the selection unit only switches from the first method to the second method in the repetitive processing. .

  (6) Further, the present invention is characterized in that, in the above-described radio receiving apparatus, the signal quality information is the number of repetitions.

  (7) Further, in the wireless reception device according to the present invention, when the number of repetitions is smaller than a predetermined value, the selection unit determines that the number of repetitions indicates low quality, It is characterized by selecting the signal addition processing and reducing the error caused by the removal.

  (8) Further, in the wireless reception device according to the present invention, when the number of repetitions is greater than a predetermined value, the selection unit determines that the number of repetitions indicates high quality, It is characterized by selecting not to perform signal addition processing.

  (9) Further, in the radio reception apparatus according to the present invention, the selection unit performs the signal addition process for each subcarrier, and the signal of each subcarrier of the signal from which the replica is removed is transmitted to the same subcarrier. A component of the removed replica is added.

  (10) Further, the present invention is characterized in that, in the above radio receiving apparatus, the replica component is a replica component of a received signal other than the one or a plurality of paths and is a component in the same subcarrier. To do.

  (11) Further, the present invention is characterized in that, in the above-described radio receiving apparatus, the selection unit changes the division number of the one or more paths based on the signal quality information.

  (12) Further, the present invention is a radio receiving apparatus that performs MIMO communication, and generates a replica of a received signal based on a demodulated modulation symbol, and receives a received signal other than the corresponding path for each one or a plurality of paths The replica is removed from the received signal, the signal from which the replica has been removed is subjected to MIMO separation based on information indicating the propagation path status of each of the one or more paths, and the separated signal as a result of the separation is repeatedly demodulated A signal receiving process for extracting transmission data and adding the removed replica component to the signal from which the replica has been removed based on signal quality information indicating the quality of the demodulated separated signal It is a radio | wireless receiver characterized by including the selection part which selects whether to perform.

  (13) Further, the present invention generates a replica of the received signal based on the demodulated modulation symbol, removes the received signal replica other than the corresponding path from the received signal for each of one or a plurality of paths, and removes the replica In the radio reception method in the radio reception apparatus for synthesizing the received signal based on information indicating the propagation path condition of each of the one or more paths, and demodulating the synthesized signal as a result of the synthesis, thereby extracting transmission data A selection step in which the selection unit selects whether or not to perform signal addition processing for adding the removed replica component to the signal from which the replica has been removed, based on signal quality information indicating the quality of the combined signal. It is a radio | wireless receiving method characterized by having.

  (14) Further, the present invention generates a replica of the received signal based on the demodulated modulation symbol, removes the received signal replica other than the corresponding path from the received signal for each of one or a plurality of paths, and removes the replica A computer of a wireless reception device that extracts transmission data by repeatedly synthesizing a synthesized signal based on information indicating a propagation path condition of each of the one or more paths, and demodulating a synthesized signal as a result of the synthesis, A radio reception program for functioning as selection means for selecting whether or not to perform signal addition processing for adding a component of the removed replica to the signal from which the replica has been removed, based on signal quality information indicating the quality of a synthesized signal is there.

  According to the present invention, it is possible to reduce the influence of the division error due to multipath division and to obtain good reception characteristics.

It is a schematic block diagram which shows the structure of the transmitter which concerns on the 1st Embodiment of this invention. It is a schematic block diagram which shows the structure of the receiver which concerns on this embodiment. It is a schematic block diagram which shows the structure of the signal detection part which concerns on this embodiment. It is the schematic which shows an example of the channel impulse response of the multipath which concerns on this embodiment. It is the schematic which shows an example of the received signal which concerns on this embodiment. It is the schematic which shows another example of the received signal which concerns on this embodiment. It is the schematic which shows an example of a frequency response. It is a flowchart which shows an example of operation | movement of the receiver which concerns on this embodiment. It is a schematic block diagram which shows the structure of the transmitter which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram which shows the structure of the receiver which concerns on this embodiment. It is a schematic block diagram which shows the structure of the signal detection part which concerns on this embodiment. It is a flowchart which shows an example of operation | movement of the receiver which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each of the following embodiments, a case where OFDM transmission is used will be described, but the present invention is not limited to this. For example, MC-CDMA (Multi Carrier-Code Division Multiple Access: Multicarrier-Code Division Multiple Access), SC-FDMA (Single Carrier-Frequency Division Multiple Access: Single Carrier-Frequency Division Multiple Access-DF) It is also possible to apply to a transmission system to which GI (Guard Interval) such as Discrete Fourier Transform-spread Orthogonal Frequency Division Multiplexing (Discrete Frequency Conversion-Spread Frequency Division Multiple Access) is added.

(First embodiment)
<About the configuration of the transmission device a1>
FIG. 1 is a schematic block diagram showing the configuration of the transmission device a1 according to the first embodiment of the present invention. In this figure, a transmission device a1 includes a pilot generation unit a101, a coding unit a102, a modulation unit a103, a mapping unit a104, an IFFT unit a105, a GI insertion unit a106, a D / A conversion unit a107, a transmission filter unit a108, and a radio unit a109. And a transmission antenna unit a110.

The pilot generation unit a101 generates a pilot signal in which the reception device b1 stores the waveform (or its signal sequence) in advance, and outputs the pilot signal to the mapping unit a104.
The encoding unit a102 encodes information bits to be transmitted to the receiving apparatus b1 using an error correction code such as a convolutional code, a turbo code, and an LDPC (Low Density Parity Check) code, and encodes the encoded bits. Is generated. The encoding unit a102 outputs the generated encoded bits to the modulating unit a103.
The modulation unit a103 modulates the coded bits input from the coding unit a102 using a modulation scheme such as PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation), and the modulation symbol Is generated. Modulation section a103 outputs the generated modulation symbol to mapping section a104.

The mapping unit a104 maps the pilot signal input from the pilot generation unit a101 and the modulation symbol input from the modulation unit a103 to a predetermined resource (time frequency band), and the mapped frequency domain signal is an IFFT unit. It outputs to a105.
The IFFT unit a105 performs frequency-time conversion on the frequency domain signal input from the mapping unit a104, and generates a time domain signal. The IFFT unit a105 outputs the generated time domain signal to the GI insertion unit a106.
The GI insertion unit a106 adds a guard interval to the time domain signal input from the IFFT unit a105, and outputs the signal with the guard interval added to the D / A conversion unit a107. Note that the time interval of the time domain signal output from the IFFT unit a105 (referred to as the FFT interval) and the time interval of the guard interval added to the signal of the time interval by the GI insertion unit a106 are units for performing FFT and IFFT. The section (referred to as GI section) is collectively referred to as an OFDM symbol section. A signal in the OFDM symbol section is called an OFDM symbol.

The D / A conversion unit a107 performs digital / analog conversion on the signal input from the GI insertion unit a106, and outputs the converted analog signal to the transmission filter unit a108.
The transmission filter unit a108 shapes the analog signal input from the D / A conversion unit a107, and outputs the waveform-shaped signal to the radio unit a109.
Radio section a109 up-converts the signal input from transmission filter section a108 from the baseband band to the radio frequency band, and transmits the signal from transmission antenna a110 to receiving apparatus b1.
Note that the transmission device a1 may include an interleaving unit, and the interleaving unit may interleave the encoded bits generated by the encoding unit a102 and output the interleaved encoded bits to the modulating unit a103.

<Configuration of Receiving Device b1>
FIG. 2 is a schematic block diagram illustrating a configuration of the receiving device b1 according to the present embodiment. In this figure, a receiving device b1 (wireless receiving device) includes a receiving antenna b101, a radio unit b102, a reception filter unit b103, an A / D conversion unit b104, a propagation path estimation unit b105, a signal detection unit b11, a demapping unit b106, A demodulator b107, a decoder b108, and a symbol replica generator b109 are included.

The radio unit b102 down-converts the signal received from the transmission device a1 via the reception antenna b101 from the radio frequency band to the baseband, and outputs it to the reception filter unit b103. The received signal may include a delayed wave exceeding the guard interval depending on the propagation path condition.
The reception filter unit b103 shapes the waveform of the signal input from the radio unit b102 and outputs the waveform to the A / D conversion unit b104.
The A / D conversion unit b104 performs analog / digital conversion on the signal input from the reception filter unit b103, and outputs the converted reception signal to the signal detection unit b11. In addition, the A / D conversion unit b104 outputs a pilot signal among the converted signals to the propagation path estimation unit b105.
The propagation path estimation unit b105 calculates a propagation path estimation value based on the pilot signal input from the A / D conversion unit b104. The propagation path estimation unit b105 outputs the calculated propagation path estimation value to the signal detection unit b11.

The signal detection unit b11 receives a received signal input from the A / D conversion unit b104 using a symbol replica input from a symbol replica generation unit b109, which will be described later, and a propagation path estimation value input from the propagation path estimation unit b105. Multipath splitting is performed on. The received signal consists of the sum of multiple incoming paths. Multipath division is processing for dividing a path constituting a received signal based on predetermined rules and conditions. In this embodiment, the received signal is divided so that each divided section after multipath division does not exceed the GI length. The signal detection unit b11 synthesizes the signal subjected to multipath division, that is, a signal in which interference caused by a delayed wave exceeding GI is suppressed, and outputs the synthesized signal to the demapping unit b106. Interference caused by delayed waves exceeding the GI is also referred to as multipath interference. Multipath interference is interference between ISI (Inter Symbol Interference) and subcarriers that are interference between preceding and following OFDM symbols. ICI (Inter Carrier Interference) is included.
Further, the signal detection unit b11 selects whether or not to perform signal addition processing for adding the component of the replica for division to the signal subjected to multipath division. Details of the signal detection unit b11 will be described later.

The demapping unit b106 demaps the signal input from the signal detection unit b11 according to the format notified from the transmission device a1 through the control channel or the like, and extracts the modulation symbols arranged in each resource. The demapping unit b106 outputs the extracted modulation symbol to the demodulation unit b107.
The demodulation unit b107 demodulates the signal input from the demapping unit b106 using the same modulation scheme as that used by the modulation unit a103 of the transmission device a1, and encodes bit LLR (encoding bit likelihood information). Log Likelihood Ratio: log likelihood ratio) is calculated. The demodulation unit b107 outputs the calculated encoded bit LLR (decoded encoded bit LLR) to the decoding unit b108.
The decoding unit b108 decodes the encoded bit LLR input from the demodulation unit b107 using the same error correction code as that used by the encoding unit a102 of the transmission device a1. The decoding unit b108 determines whether or not the iterative process described later has been performed up to the maximum number of times, and when it is determined that the maximum number of times has been performed, outputs the decoded information bits (hard decision value). On the other hand, when the decoding unit b108 determines that the maximum number of times has not been performed, the decoding unit b108 determines whether there is no error in the error correction decoding result. If it is determined that there is no error in the result of error correction decoding, the decoding unit b108 outputs the decoded information bits. On the other hand, when it is determined that there is an error in the error correction decoding result, the decoding unit b108 outputs the encoded bit LLR (the encoded bit LLR after decoding) whose likelihood has been updated by the decoding process to the symbol replica generation unit b109. To do. The coded bit LLR is also called a soft decision value.

The symbol replica generation unit b109 generates a symbol replica that is an expected value of the modulation symbol from the coded bits LLR input from the decoding unit b108, and outputs the symbol replica to the signal detection unit b11.
When the transmission device a1 includes an interleaving unit, the reception device b1 includes a deinterleaving unit. The deinterleaving unit deinterleaves the encoded bit LLR calculated by the demodulation unit b107, and the deinterleaved encoded bit LLR is obtained. It outputs to the decoding part b108.

<Regarding the Configuration of the Signal Detection Unit b11>
FIG. 3 is a schematic block diagram illustrating the configuration of the signal detection unit b11 according to the present embodiment. In this figure, the signal detection unit b11 is divided replica generation unit b111, multipath dividing unit b112, FFT (Fast Fourier Transform: fast Fourier transform) unit _{b113-1~b113-N B,} selector B 114, and the synthesis unit b115 is included.

The division replica generation unit b111 performs frequency-time conversion on a frequency domain signal in which the symbol replica input from the symbol replica generation unit b109 is arranged at the position where the demapping unit b106 has been demapped. The division replica generation unit b111 adds a guard interval to the time domain signal subjected to frequency-time conversion in the same manner as the GI insertion unit a106 of the transmission device a1. Division replica generating unit b111, using the channel estimation value input from the channel estimation unit b105, from a signal obtained by adding the guard interval, N _B blocks comprising one or more paths b (b = 1 ~ N _B ), a division replica is generated and output to the multipath division unit b112 and the selection unit b114.

The multipath division unit b112 stores the reception signal input from the A / D conversion unit b104 until the decoding unit b108 determines that there is no error in the error correction decoding result. The multipath division unit b112 divides the stored received signal into signals for each block b (multipath division) using the division replica input from the division replica generation unit b111. Specifically, the division replica other than the block b is subtracted from the stored reception signal. Thus, the receiving apparatus b1 can remove ISI by performing multipath division. Multipath dividing unit b112 each signal block 1 to N _B where the multipath division, and outputs the FFT unit _{b113-1~b113-N B.}
FFT unit _{b113-1~b113-N B} extracts the signal of each FFT interval from the signal of each block b input from the multipath dividing unit b 112. FFT unit _{b113-1~b113-N B,} a signal of the extracted FFT interval and the time-frequency transformation, and generates a signal in the frequency domain. FFT unit _{b113-1~b113-N B} outputs a signal of the generated frequency domain to the selection unit B 114.

The selection unit b114 counts the number of times that the decoding unit b108 determines that there is an error in the error correction decoding result, that is, the number of multi-division processes performed by the multipath division unit b112. The number of times of multi-division processing indicates the number of repetitions of processing (repetition processing) of the symbol replica generation unit b109, signal detection unit b11, demapping unit b106, demodulation unit b107, and decoding unit b108 (hereinafter referred to as multi-division processing). The number of times is called the repetition number. The selection unit b114 determines whether or not to perform division error suppression processing based on the number of repetitions (signal quality information).
If it is determined to perform the suppression of the division error, selecting section b114, as described later, the components of the divided replica input from the division replica generating unit b111, the FFT unit _{b113-1~b113-N B} A signal addition process for adding to the input signal is performed, and the signal subjected to the signal addition process is output to the synthesis unit b115. On the other hand, if it is determined not to perform the suppressing process of division error, selecting section b114 outputs the signal input from the FFT unit _{b113-1~b113-N B} as the combining unit B115.
The synthesizer b115 generates a signal (synthesized signal) obtained by synthesizing the signal input from the selector b114, and outputs the signal to the demapping unit b106. Here, the synthesis unit b115 generates a signal subjected to propagation path compensation using MMSEC (Minimum Mean Square Error Combining: synthesis based on least mean square error), MRC (Maximum Ratio Combining: maximum ratio synthesis), or the like. . Details of the signal synthesis processing performed by the synthesis unit b115 will be described later together with the processing of the signal detection unit b11.
Hereinafter, the processing of the signal detection unit b11 when the selection unit b114 does not perform division error suppression processing is referred to as a division error suppression method (first method), and the signal detection unit b11 when the division error suppression processing is performed. This process is called a division error non-suppression method (second method).

<Regarding Processing of Signal Detection Unit b11>
Hereinafter, details of the processing of the signal detection unit b11 will be described. Although the case where the number of multipath divisions is two (N _B = 2) will be described, the present invention is not limited to this.

FIG. 4 is a schematic diagram illustrating an example of a multipath channel impulse response according to the present embodiment. 4A to 4C, the vertical axis represents received power, and the horizontal axis represents time. 4A to 4C, p1 to p12 indicate channel impulse responses of the respective paths.
Multipath dividing unit b112, as described above, by dividing the multipath several blocks N _B, to extract the signal paths included from the received signal to each block b. For example, when (A) in FIG. 4 is divided into two blocks as shown in (B) and (C) in FIG. 4, the multipath dividing unit b112 extracts a signal of the path indicated by p1 to p6 in block 1. , A signal of a path indicated by p7 to p12 of the block 2 is extracted.

FIG. 5 is a schematic diagram illustrating an example of a received signal according to the present embodiment. This figure shows the signal divided into the multipath components of FIG. 5A to 5C, the horizontal axis indicates time. 5A to 5C, r1 to r12 represent received signals received by the receiving apparatus b1 through the paths indicated by p1 to p12 in FIG. 4, respectively. The signal actually received by the receiving device b1 is a signal obtained by adding the received signals r1 to r12.
FIGS. 5B and 5C show the components of blocks 1 and 2 extracted from the received signal, respectively. The multipath division unit b112 subtracts the division replica signal from the reception signal in order to extract each block component from the reception signal shown in FIG. Here, the division replica signal is a replica signal generated by the division replica generation unit b111 using a channel impulse response included in a block other than the block to be extracted. For example, when the block 1 component is extracted from the received signal shown in FIG. 5A, the multipath dividing unit b112 divides the signal received through the block 2, that is, the signals r7 through r12 through p7 through p12. The replica signal for use is subtracted from the received signal. Similarly, when extracting the two components of the block, the multipath dividing unit b112 subtracts the signal received through the block 1, that is, the replica signal for dividing the signals r1 to r6 that have passed through p1 to p6, from the received signal. .
Divided signal thus is converted into the frequency domain by the FFT unit _{b113-1~b113-N B.} As shown in FIGS. 5B and 5C, the FFT is performed on the basis of the head of each block.

Next, the iOFDM symbols FFT unit B113-b to process the block b is the output of the FFT unit _{b113-1~b113-N B,} the signal ^R _{1 i} of the k _subcarrier, b (k) are the following It is represented by formulas (1) and (2).

Here, H _b (k) represents a frequency response in the k-th subcarrier of the path included in the b-th block. S _i (k) indicates a modulation symbol transmitted on the k-th subcarrier of the _i- th OFDM symbol, and S ′ _i (k) indicates a symbol replica of S _i (k). N _f indicates the number of points in the FFT interval.
H ^- _b (k) is the frequency response in the k-th subcarrier of the path other than the b-th block, and H ^- _{b, k} (l) is from the l-th subcarrier of the path other than the b-th block to the k-th subcarrier. Represents a leaking frequency component. A method for calculating H ^- _b (k) will be described later. H− _{1, b, k} (l) is the frequency component of the k-th subcarrier affected by the l-th subcarrier among the components leaked from the previous OFDM symbol, and H _{+ 1, b, k.} (L) represents the frequency component of the k-th subcarrier affected by the l-th subcarrier among the components that leak from the next OFDM symbol.

That is, Equation (1) indicates that the first term is the desired signal component of the b-th block. Also, Equation (1) indicates that N ′ (k) of the second term, that is, Equation (2), is a residual component of the multipath k-th subcarrier included in other than the b-th block.
Further, the expression (2) indicates that N ′ (k) is a component (first to fourth terms) based on the removal residual (S _i (k) −S ′ _i (k)) and noise N (k) ( And the sum of the fifth term). Specifically, the equation (2) indicates that the first term is an interference component received from the kth subcarrier other than the bth block, and the second term is an ICI component received from the kth subcarrier from other than the kth subcarrier. Show. Equation (2) is the ISI component received by the k-th subcarrier among the components that the third term leaks from the previous OFDM symbol, and the fourth term is also calculated from the next OFDM symbol. This indicates that it is the ISI component received by the k-th subcarrier among the incoming components. Equation (2) indicates that the fifth term is noise N (k) in the k-th subcarrier.
In Expressions (1) and (2), if the quality of S ′ _i (k) is high, the signal of each block obtained by dividing the multipath can be extracted with good quality, and combining them can provide a path diversity effect. Therefore, it shows that a favorable characteristic is acquired. On the other hand, in the equations (1) and (2), if the quality of S ′ _i (k) is low, the replica removal residual (S _i (k) −S ′ _i (k)) is generated and the characteristics deteriorate. Indicates that The removal error of the replica generated by dividing the multipath is called a division error.

As described above, when the selection unit b114 determines to perform the division error suppression process, the selection unit b114 adds the component of the division replica to the signal R ¹ _{i, b} (k). In this case, the _i- th OFDM symbol of the block b and the k-th subcarrier signal R ² _{i, b} (k) output from the selection unit b114 are expressed by the following equations (3) and (4).

Equation (4) is a component (first to third terms) in which N ″ (k), which is the second term of Equation (3), is based on the removal residual (S _i (k) −S ′ _i (k)). ) And noise N (k) (fourth term). Specifically, Equation (4) indicates that the first term is an ICI component that the k-th subcarrier receives from other than the k-th subcarrier. Equation (2) is an ISI component received by the k-th subcarrier that the second term leaks from the previous OFDM symbol, and the third term leaks from the next OFDM symbol. It shows that it is an ISI component received by the k-th subcarrier among the coming components. Equation (4) indicates that the fourth term is noise N (k) in the k-th subcarrier.

Comparing equations (2) and (4), in equation (4), the first term of equation (2), that is, a component based on the removal residual (S _i (k) −S ′ _i (k)) The interference component in the k-th subcarrier received from other than the b-th block is removed. That is, for components other than the component calculated from the symbol S _i (k) and the frequency response (the first term in the equations (1) and (3)), the equation (4) is smaller than the equation (2). That is, it shows that the influence of the removal residual is reduced.
As described above, the quality of the symbol replica used for the process of dividing the multipath by performing the process in which the selection unit b114 adds the division replica to the signal R ¹ _{i, b} (k), that is, the division error suppression process. The removal residual (referred to as a division error) resulting from the above can be reduced, and characteristic deterioration can be reduced.

Here, the selection unit b114 selects H ⁻ _b (k based on the channel impulse response h _j (j is a path identification number) and the length M _{j obtained} by removing the GI length from the delay time of the channel impulse response. ) Is calculated. More specifically, the selection unit b114 _{is, ((N f -M j)} / N f) calculating a value of the k-th subcarrier when converted into frequency domain _{h j} in ^{FFT, H} _- b (k) And
For example, the selection unit b114 includes four paths, the division number of the multipath be a two _(N B = 2), ^H as follows: _- calculating the b (k).
FIG. 6 is a schematic diagram illustrating another example of the received signal according to the present embodiment. This figure is a diagram when four waves arrive as received signals rr1, rr2, rr3, and rr4. This figure is a diagram when the multipath is divided into two blocks, that is, a block 1 including the reception signals rr1 and rr2, and a block 2 including the reception signals rr3 and rr4. In this figure, the received signal rr1, rr2, rr3, rr4 each channel impulse response is _{h 1, h 2, h 3} , h 4.

Specifically, when the reception signals rr1 and rr2 in FIG. 6 are extracted in the block 1, the selection unit b114 calculates H ⁻ _b (k) as follows. In this figure, the lengths of the channel impulse responses h ₃ and h ₄ included in the block 2 that exceed the GI are M ₃ and M ₄ , respectively.
At this ^{time, H} _- 1 (k) _was converted _{(((N f -M 3)} / N f) h 3, ((N f -M 4) / N f) h 4) into the frequency domain by FFT of Is calculated as the k-th subcarrier. N _f is the FFT interval. Note that the k-th subcarrier when (h ₃ , h ₄ ) is approximately converted to the frequency domain may be H ⁻ _b (k).

FIG. 7 is a schematic diagram illustrating an example of a frequency response. This figure shows an example of a frequency response when the received signal of FIG. 6 is received. Further, in FIG. 7, the k−2 to k + 2 subcarriers will be described for simplification of description.
FIG. 7B shows a case where the division error suppression method is applied, and FIG. 7C shows a case where the division error non-suppression method is applied. FIG. 7A shows a case where neither the division error suppression method nor the division error non-suppression method is applied. The upper diagram of FIG. 7 (A), (B) , (C) shows the frequency response of the k-. 2 to (k + 2) th subcarriers of the channel impulse response _{h 2} in Fig. The lower part of FIG. 7 (A), (B) , (C) shows the frequency response of the k-. 2 to (k + 2) th subcarriers of the channel impulse response _{h 3} of FIG.

Upper diagram of FIG. 7 (A), since the channel impulse response h ₂ in FIG. 6 is a delay within GI, leaks to the subcarriers other than the k subcarrier (k ± 2, k ± 1 ) Indicates. On the other hand, lower part of FIG. 7 (A) for a delay channel impulse response h ₃ of FIG. 6 exceeds GI, indicating that the leak to the subcarriers other than the k-th subcarrier.

FIG. 7B is a diagram in the case where the division error suppression method is applied to the frequency response received signal of FIG. FIG. 7B is a diagram when the received signals rr1 and rr2 are extracted in the block 1.
Below in FIG. 7 (B), the received signal other than the reception signal included in the block 1 (the received signal rr3, rr4 of Fig. 6) is removed, that the frequency response for the channel impulse response h ₃ is reduced Show.

FIG. 7C is a diagram in the case where the division error non-suppression method is applied to the frequency response reception signal of FIG. FIG. 7C is a diagram when the received signals rr1 and rr2 are extracted in the block 1.
The lower diagram of FIG. 7C is a signal output by the FFT unit 242 for components that do not cause ICI by the division error non-suppression method (components of the k-th subcarrier: components indicated by broken lines in the lower diagram of FIG. 7C). (See FIG. 7B).

  Hereinafter, the signal synthesis process performed by the synthesis unit b115 will be described. The synthesizing unit b115 performs synthesis represented by the following formula (5).

However, R _{i, b} (k) is a signal input from the selection unit b114, and is R ¹ _{i, b} (k) in the case of the division error non-suppression method, and R ^{2 in} the case of the division error suppression method. _{i, b} (k). W _{i, b} (k) is an MMSE weight.
In the case of the division error non-suppression method, the MMSE weight W _{i, b} (k) is expressed by the following equation (6).

Here, σ ₁ ² is represented by the following formula (7), (8), or (9).

Here, E [X] represents a time average of X (for example, an average in one frame). S (k) indicates a modulation symbol transmitted on the k-th subcarrier, and S ′ (k) indicates a symbol replica of S (k). In the calculation of Expression (8), for example, a symbol replica of a pilot signal and a modulation symbol are used for S (k) and S ′ (k). Further, y represents a received signal, and h represents a channel estimation value. In equations (7) and (8), σ _{1 and k} ² are set averages for each subcarrier, but may be set averages for all subcarriers. For example, it is good also as a set average of all the subcarriers in the range in the same symbol, the same packet, and the same frame. Alternatively, σ _{1 and k} ² may be approximated as noise only, and σ _{1 and k} ² may be set as noise power σ _N ² .

On the other hand, in the case of the division error suppression method, the MMSE weight W _{i, b} (k) is expressed by the following equation (10).

Here, σ ₂ ² is expressed by the following formula (11) or (12).

In the calculation of Expression (12), for example, a symbol replica of a pilot signal and a modulation symbol are used for S (k) and S ′ (k). In equations (11) and (12), σ _{2 and k} ² are set averages for each subcarrier, but may be set averages for all subcarriers. For example, it is good also as a set average of all the subcarriers in the range in the same symbol, the same packet, and the same frame. Alternatively, σ _{2 and k} ² may be approximated as noise only, and σ _{2 and k} ² may be set as noise power σ _N ² .

Here, the expressions (1) and (3) are compared.
When the quality of S ′ _i (k) is high and there is no division error, the multipath component of the received signal can be completely divided in Equation (1). Therefore, when it is synthesized by the synthesis unit b115, a path diversity effect is obtained. Can do. Conversely, at this time, the expression (3) has almost the same characteristics as OFDM without ISI or ICI. Therefore, when the division error is small, the selection unit b114 outputs the signal input from the FFT unit _{b113-1~b113-N B} as the synthesis unit B115, it is better to combine the signals of the formula (1) Characteristics Can be obtained.
On the other hand, when the quality of S ′ _i (k) is not high and there is a division error, the division error is equal to the division error of the desired signal, and the division error is smaller in equation (3) than in equation (1). Become. Therefore, when the division error is large, the signal detection unit B115 is, ^H at the selector B 114 _- outputs b (k) signal obtained by adding S _'i (k) to the synthesizing unit B115, combining the signals of the formula (3) The better characteristics can be obtained. In particular, when multi-level modulation or a high coding rate is used, deterioration due to the division error becomes large. Therefore, it is possible to obtain better characteristics when the division error is suppressed as in Expression (3).

As illustrated in FIG. 2, the reception device b1 performs a process of improving the quality of S ′ _i (k) by repeatedly performing the processes from the signal detection unit b11 to the symbol replica generation unit b109. Therefore, when the number of repetitions is smaller than a predetermined value, that is, when the number of repetitions is small, the selection unit b114 determines that the quality of S ′ _i (k) is low and sets H ⁻ _b (k) S ′ _i (k). The added signal is output to the synthesis unit b115 to suppress the division error. On the other hand, the selection unit b114, when the number of repetitions is predetermined value or more, that is, it outputs to the synthesizing unit b115 the signal input from the FFT unit _{b113-1~b113-N B} when many repeat count . When the signal detection unit b11 processes the received signal first, the number of repetitions is 0. At this time, multipath division is not performed, and the same processing as conventional OFDM is performed.
For example, the selection unit b114 outputs a signal obtained by adding H ⁻ _b (k) S ′ _i (k) to the synthesis unit b115 when the predetermined value is “4 times” and the number of repetitions is 0 to 3 times. That is, formula (3) is selected. The selection section b114, the repeat count 4 after outputting the signal input from the FFT unit _{b113-1~b113-N B} as the synthesis unit B115, that is, selects the formula (1). Note that the predetermined value of the number of repetitions may be a value that is half the maximum number of repetitions, or the number of times of convergence when Expression (3) is used. In addition, the larger the number of multipath divisions, the larger the division error and the better characteristics. Therefore, the number of divisions may be increased as the number of repetitions increases.

<About operation>
FIG. 8 is a flowchart showing an example of the operation of the receiving apparatus b1 according to the present embodiment.
(Step S101) The multipath division unit b112 performs multipath division on the received signal using the division replica generated in step S111 described later. Thereafter, the process proceeds to step S102.
(Step S102) FFT unit _{b113-1~b113-N B,} the multipath division signals to the time-frequency conversion performed in step S101, generates a signal in the frequency domain. Thereafter, the process proceeds to step S103.

(Step S103) The selection unit b114 determines whether or not the number of repetitions is smaller than a specified number (for example, 4 times). If the number of repetitions is smaller than the prescribed number (YES), the process proceeds to step S104. On the other hand, if the number of repetitions is equal to or greater than the specified number (NO), the process proceeds to step S105.
(Step S104) The selection unit b114 adds H ^- _b (k) S ′ _i (k), that is, a replica of the k-th subcarrier of the i-th OFDM symbol for a path other than the b-th block to reduce the division error. To do. Thereafter, the process proceeds to step S105.
(Step S105) The synthesizer b115 synthesizes the signal using MMSEC. Thereafter, the process proceeds to step S106.

(Step S106) The demodulator b107 demodulates the signal synthesized in step S105, and calculates the coded bit LLR. To do. Thereafter, the process proceeds to step S107.
(Step S107) The decoding unit b108 decodes the encoded bit LLR demodulated in step S106. Thereafter, the process proceeds to step S108.
(Step S108) The decoding unit b108 determines whether or not the iterative process has been performed up to the maximum number of times. When it is determined that the iterative process has been performed up to the maximum number (YES), the encoded bit LLR decoded in step S107 is output, and the operation is terminated. On the other hand, if it is determined that the repetitive processing has not been performed up to the maximum number (NO), the process proceeds to step S109.
(Step S109) The decoding unit b108 determines whether or not there is an error in the error correction decoding result. If it is determined that there is no error in the result of error correction decoding (YES), the decoded encoded bit LLR is output and the operation is terminated. On the other hand, if it is determined that there is an error in the result of error correction decoding (NO), the process proceeds to step S110.

(Step S110) The symbol replica generation unit b109 generates a symbol replica from the encoded bit LLR decoded in step S107. Then, it progresses to step S111.
(Step S111) The division replica generation unit b111 generates a division replica from the symbol replica generated in step S110. Then, it returns to step S101.

As described above, according to the present embodiment, the receiving device b1 removes the replica of the removed replica component (H ⁻ _b (k) S ′) based on the number of times the division replica generation process is repeated. Whether or not to perform signal addition processing to be added to the signal is selected.
As a result, when the number of repetitions is small and the quality of the signal output from the signal detection unit b11 is low, the reception device b1 performs signal addition processing to reduce the influence of the division error due to multipath division, and is good. Reception characteristics can be obtained. On the other hand, the reception device b1 performs multipath division without performing the signal addition processing when the number of repetitions of the division replica generation processing is large and the quality of the signal output from the signal detection unit b11 is high. A path diversity effect can be obtained. That is, it is possible to select whether to obtain a good reception characteristic by reducing the division error or to obtain a path diversity effect.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings.
In the present embodiment, the case where the communication system is a MIMO (Multiple Input Multiple Output) system will be described. Hereinafter, a case will be described in which a receiving device b1 having R antennas receives a signal transmitted from a transmitting device a2 having T antennas.

<About the configuration of the transmitting device a2>
FIG. 9 is a schematic block diagram showing the configuration of the transmission device a2 according to the second embodiment of the present invention. In this figure, a transmission device a2 includes a pilot generation unit a201, a coding unit a202-t, a modulation unit a203-t, a mapping unit a204-t, an IFFT unit a205-t, a GI insertion unit a206-t, and a D / A conversion unit. a207-t, transmission filter unit a208-t, radio unit a209-t, and transmission antenna unit a210-t. However, t = 1, 2,..., T.

The pilot generation unit a201 generates a pilot signal in which the reception device b2 stores the waveform (or its signal sequence) in advance, and outputs the pilot signal to the mapping unit a204-t.
The encoding unit a202-t encodes information bits to be transmitted to the receiving device b2 using an error correction code such as a convolutional code, a turbo code, and an LDPC code, and generates encoded bits. The encoding unit a202-t outputs the generated encoded bits to the modulation unit a203-t.
The modulation unit a203-t modulates the coded bits input from the coding unit a202-t using a modulation scheme such as PSK or QAM, and generates a modulation symbol. The modulation unit a203-t outputs the generated modulation symbol to the mapping unit a204-t.

The mapping unit a204-t maps pilot signals and modulation symbols input from the pilot generation unit a201 and the modulation unit a203-t, respectively, to predetermined resources (time frequency band), and converts the mapped frequency domain signals to IFFT. To the part a205-t.
The IFFT unit a205-t performs frequency-time conversion on the frequency domain signal input from the mapping unit a204-t to generate a time domain signal. The IFFT unit a205-t outputs the generated time domain signal to the GI insertion unit a206-t.
The GI insertion unit a206-t adds a guard interval to the time domain signal input from the IFFT unit a205-t, and outputs the signal with the guard interval added to the D / A conversion unit a207-t.
The D / A conversion unit a207-t performs digital / analog conversion on the signal input from the GI insertion unit a206-t, and outputs the converted analog signal to the transmission filter unit a208-t.
The transmission filter unit a208-t shapes the analog signal input from the D / A conversion unit a207-t, and outputs the waveform-shaped signal to the radio unit a209-t.
The radio unit a209-t upconverts the signal input from the transmission filter unit a208-t from the baseband to the radio frequency band, and transmits the signal from the transmission antenna a210-t to the reception device b2.

<Configuration of Receiving Device b2>
FIG. 10 is a schematic block diagram showing the configuration of the receiving device b2 according to this embodiment. In this figure, the receiving device b2 includes a receiving antenna b201-r, a radio unit b202-r, a receiving filter unit b203-r, an A / D conversion unit b204-r, a propagation path estimating unit b205, a signal detecting unit b21, demapping. Unit b206-r, demodulator b207-r, decoder b208-r, and symbol replica generator b209-r. However, r = 1, 2,..., R.

The radio unit b202-r down-converts the signal received from the transmission device a1 via the reception antenna b201-r from the radio frequency band to the baseband band, and outputs it to the reception filter unit b203-r. Note that this received signal may include a delayed wave exceeding the guard interval depending on the propagation path condition.
The reception filter unit b203-r shapes the signal input from the radio unit b202-r and outputs the waveform to the A / D conversion unit b204-r.
The A / D conversion unit b204-r performs analog / digital conversion on the signal input from the reception filter unit b203-r, and outputs the converted signal to the signal detection unit b11. In addition, the A / D conversion unit b204-r outputs a pilot signal among the converted signals to the propagation path estimation unit b205.
The propagation path estimation unit b205 calculates propagation path estimation values based on the pilot signals input from the A / D conversion units b204-1 to b204-R. The propagation path estimation unit b205 outputs the calculated propagation path estimation value to the signal detection unit b21.

The signal detection unit b21 uses an A / D conversion unit b204 using a symbol replica input from symbol replica generation units b209-1 to b209-R, which will be described later, and a channel estimation value input from the channel estimation unit b205. Multipath division is performed on the signals input from −1 to b204-R. The signal detection unit b21 performs MIMO signal separation on a signal subjected to multipath division, that is, a signal in which interference caused by a delayed wave exceeding GI is suppressed, and outputs the result to the demapping units b205-1 to b205-R. To do. Details of the signal detection unit b21 will be described later.
Further, the signal detection unit b21 selects whether or not to perform signal addition processing for adding the component of the division replica to the signal subjected to multipath division. Details of the signal detection unit b21 will be described later.

The demapping unit b206-r demaps the signal input from the signal detection unit b21 according to the format notified from the transmission device a2 through the control channel or the like, and extracts the modulation symbols arranged in each resource. The demapping unit b106 outputs the extracted modulation symbol to the demodulation unit b207-r.
The demodulator b207-r demodulates the signal input from the demapping unit b206-r using the same modulation scheme used by the modulator a203-t of the transmission device a2, and uses the likelihood information of the encoded bits. A certain coded bit LLR is calculated. The demodulator b207-r outputs the calculated encoded bit LLR to the decoder b208-r.

The decoding unit b208-r decodes the encoded bit LLR input from the demodulation unit b207-r using the same error correction code as that used by the encoding unit a202-t of the transmission device a2. The decoding unit b208-r determines whether or not the iterative process has been performed up to the maximum number of times, and when it is determined that the maximum number of times has been performed, outputs the decoded information bits. On the other hand, when the decoding unit b208-r determines that the maximum number of times has not been performed, the decoding unit b208-r determines whether there is no error in the result of error correction decoding. If it is determined that there is no error in the error correction decoding result, the decoding unit b208-r outputs the decoded information bits. On the other hand, when it is determined that there is an error in the error correction decoding result, the decoding unit b208-r outputs the encoded bit LLR whose likelihood is updated by the decoding process to the symbol replica generation unit b209-r.
The symbol replica generation unit b209-r generates a symbol replica that is an expected value of the modulation symbol from the encoded bit LLR input from the decoding unit b208-r, and outputs the symbol replica to the signal detection unit b21.

<Regarding the Configuration of the Signal Detection Unit b21>
FIG. 11 is a schematic block diagram illustrating a configuration of the signal detection unit b11 according to the present embodiment. In this figure, the signal detection unit b21 includes dividing replica generating section (b) 211, the multipath dividing unit b 212, FFT section _{b213r-1~b213r-N B,} configured to include a selection unit B 214, and a signal separating unit B215. However, r = 1, 2,..., R.

The division replica generation unit b211 performs frequency-time conversion on a frequency domain signal obtained by mapping the symbol replicas input from the symbol replica generation units b209-1 to b209-R to the positions demapped by the demapping unit b206-r. . The division replica generation unit b211 adds a guard interval to the time domain signal subjected to frequency-time conversion in the same manner as the transmission device a2. Division replica generating unit b211, using the channel estimation value input from the channel estimation unit b 205, a signal obtained by adding the guard interval, N _B blocks n (n = 1 containing one or more paths ~ N _B ), a division replica extracted every time is generated and output to the multipath division unit b212 and the selection unit b214.

The multipath division unit b212 receives a signal for each antenna b201-r (referred to as an rth received signal) input from the A / D conversion unit b204-r until the decoding unit b208 determines that there is no error in the error correction decoding result. ) Is memorized. The multipath division unit b212 divides the stored r-th received signal into signals for each block n (multipath division) using the division replica input from the multipath division unit b212. Specifically, the replica for division other than block n is subtracted from the stored r-th received signal. Multipath dividing unit b212, respectively the first r received signals of the blocks 1 to N _B where the multipath division, and outputs the FFT unit _{b213r-1~b213r-N B.}

FFT unit _{b213r-1~b213r-N B} extracts the signal of the FFT interval from the signal input from the multipath dividing unit b 212. FFT unit _{b213r-1~b213r-N B,} a signal of the extracted FFT interval and the time-frequency transformation, and generates a signal in the frequency domain. FFT unit _{b213r-1~b213r-N B} outputs a signal of the generated frequency domain to the selection unit B 214.

The selection unit b214 determines the number of times that the decoding unit b208-r determines that there is an error in the error correction decoding result, that is, the division replica generation processing performed by the symbol replica generation unit b209-r and the division replica generation unit b211. Count the number of repetitions. The selection unit b214 determines whether or not to perform division error suppression processing based on the number of repetitions.
If it is determined to perform the suppression of the division error, selecting section b214, as described later, the division replica component input from the dividing replica generating section b111, an input from the FFT unit _{b213r-1~b213r-N B} The added signal is added to the signal separation unit b215. On the other hand, if it is determined not to perform the suppressing process of division error, selecting section b214 outputs the signal input from the FFT unit _{b213r-1~b213r-N B} as the signal separation unit B215.
The signal separation unit b215 performs MIMO signal separation on the signal input from the selection unit b214, and separates the spatially multiplexed signals. For example, the signal separation unit c153 performs MIMO signal separation processing using MMSEC. The signal separation unit b215 outputs the separated signal to the demapping unit b206-r. Details of the MIMO signal separation processing performed by the signal separation unit b215 will be described later together with the processing of the signal detection unit b21.
Hereinafter, the process of the signal detection unit b21 when the selection unit b214 does not perform the division error suppression process is referred to as a division error suppression method, and the process of the signal detection unit b21 when the division error suppression process is performed is the division error non-deletion method. This is called a suppression method.

<About the process of the signal detection part b21>
FFT unit _{b213r-1~b213r-N} first iOFDM symbol block b _{that B} is output, the r received signal ^R _{2 i} of the k-th _{subcarrier, b,} r (k) is expressed by the following equation (13) The

Equation (13), first iOFDM symbol, the r received signal ^R _{2 i} of the k-th _{subcarrier, b,} r (k) indicates that represented by a vector of _{N B} dimension. S _i (k) indicates a modulation symbol transmitted on the k-th subcarrier of the _i- th OFDM symbol, and S ′ _i (k) indicates a symbol replica of S _i (k). Note that S _i (k) and S ′ _i (k) are T-dimensional vectors.
H _{b, r} (k) represents a frequency response in the k-th subcarrier of the path included in the b-th block in the r-th received signal.
H ^- _{b, r} (k) is the frequency response in the k-th subcarrier of the path other than the b-th block in the r-th received signal, and H ^- _{b, k, r} (l) is the number in the r-th received signal. This represents a frequency component that leaks from the l-th subcarrier of the path other than the b block to the k-th subcarrier. H− _{1, b, k, r} (l) are frequency components of the k-th subcarrier affected by the l-th subcarrier among components that leak from the previous OFDM symbol in the r-th received signal. , H _{+ 1, b, k, r} (l) represents the frequency component of the kth subcarrier affected by the lth subcarrier among the components that leak from the next OFDM symbol in the rth received signal. .

That is, Expression (13) indicates that the first term is the desired signal component of the b-th block in the r-th received signal. Also, Equation (13) is the second term N _r ′ (k), that is, Equation (14) is the residual component of the multipath k-th subcarrier included in the r-th received signal other than the b-th block. Indicates that
Further, the expression (14) indicates that N _r ′ (k) is a component (first to fourth terms) based on the removal residual (S _i (k) −S ′ _i (k)) and noise N _r (k ) (5th term). Specifically, Equation (14) indicates that the first term is the interference component received from the k-th subcarrier other than the b-th block, and the second term is the ICI component received from the k-th subcarrier from other than the k-th subcarrier. Show. Equation (14) is the ISI component received by the kth subcarrier among the components that the third term leaks from the previous OFDM symbol, and the fourth term is also calculated from the next OFDM symbol. This indicates that it is the ISI component received by the k-th subcarrier among the incoming components. Equation (14) indicates that the fifth term is noise N (k) in the k-th subcarrier.
In Expressions (13) and (14), if the quality of S ′ _i (k) is high, the signal of each block obtained by dividing the multipath can be extracted with good quality, and combining them can provide a path diversity effect. Therefore, it shows that a favorable characteristic is acquired. On the other hand, if the quality of S ′ _i (k) is high, the expressions (13) and (14) are deteriorated because the replica removal residual (S _i (k) −S ′ _i (k)) is generated. Indicates that

As described above, when the selection unit b214 determines to perform the division error suppression process, the selection unit b214 adds the component of the division replica to the r-th received signal R ² _{i, b, r} (k). In this case, the i-th OFDM symbol of the block b and the r-th received signal R ² _{i, b, r} (k) of the k-th subcarrier output from the selection unit b214 are expressed by the following equations (15) and (16). Is done.

Comparing equations (14) and (16), in equation (16), the first term of equation (14), that is, a component based on the removal residual (S _i (k) −S ′ _i (k)) In the r-th received signal, interference components received from other than the b-th block are removed. That is, for components other than the component calculated from the symbol S _i (k) and the frequency response (the first term in the equations (13) and (15)), the equation (16) is smaller than the equation (14). That is, it shows that the influence of the removal residual is reduced.
As described above, the selection unit b114 performs the process of adding the division replica to the r-th received signal R ² _{i, b, r} (k), that is, the division error suppression process, thereby reducing the division error. And characteristic deterioration can be reduced.

Hereinafter, the MIMO signal separation processing performed by the signal separation unit b215 will be described.
In the case of the division error non-suppression method, the MMSE weight M (k) is expressed by the following equation (17).

Here, σ ₁ ² is represented by the above formula (7), (8), or (9).
On the other hand, in the case of the division error suppression method, the MMSE weight M (k) is expressed by the following equation (18).

Here, σ ₂ ² is represented by the formula (11) or (12).

As illustrated in FIG. 11, the reception device b2 performs a process of improving the quality of S ′ _i (k) by repeatedly performing the processes from the signal detection unit b21 to the symbol replica generation unit b209-r. Therefore, selection section b214, when the number of iterations smaller than a predetermined value, i.e., when a small number of repetitions 'as a low-quality ^{_{i (k) H - b,}} r (l) S' S i (k ) Is output to the synthesizing unit b115 to suppress the division error. On the other hand, the selection unit b114, when the number of repetitions is predetermined value or more, that is, it outputs to the synthesizing unit b115 the signal input from the FFT unit _{b113-1~b113-N B} when many repeat count . When the signal detection unit b11 processes the received signal first, the number of repetitions is 0. At this time, multipath division is not performed, and the same processing as conventional OFDM is performed.

<About operation>
FIG. 12 is a flowchart showing an example of the operation of the receiving device b2 according to the present embodiment.
Comparing the flowchart according to the present embodiment (FIG. 12) with the flowchart according to the first embodiment (FIG. 8), in FIG. 12, the process of step 105 in FIG. 8 replaces the process of step S205. The point is different. A description of the same processing (steps S101 to S104, S106 to S111) as in the first embodiment is omitted.

(Step S205) The signal separation unit b215 performs MIMO signal separation processing using MMSEC. Thereafter, the process proceeds to step S106.

As described above, according to the present embodiment, the receiving apparatus b2 that performs MIMO communication performs the removed replica component (H ⁻ _{b, r} (l) S) based on the number of times the division replica generation process is repeated. Select whether or not to perform signal addition processing for adding ') to the signal from which the replica is removed.
As a result, when the number of repetitions is small and the quality of the signal output from the signal detection unit b21 is low, the reception device b2 performs signal addition processing to reduce the influence of the division error due to multipath division, which is favorable. Reception characteristics can be obtained. On the other hand, the reception device b2 performs multipath division without performing the signal addition processing when the number of repetitions of the division replica generation processing is large and the quality of the signal output from the signal detection unit b21 is high. A path diversity effect can be obtained. That is, it is possible to select whether to obtain a good reception characteristic by reducing the division error or to obtain a path diversity effect.

  In each of the above embodiments, the receiving apparatuses b1 and b2 select whether or not to reduce the division error every repetition. In addition to this processing, the receiving devices b1 and b2 may change the number of multipath divisions based on the number of repetitions. For example, the receiving devices b1 and b2 may increase the number of divisions as the number of repetitions increases. Thereby, the receiving apparatuses b1 and b2 can improve the path diversity effect by multipath division when the quality of the signal output from the signal detection unit b21 is high.

  Further, in each of the above embodiments, the case where the receiving apparatuses b1 and b2 calculate weights using MMSEC has been described. However, the present invention is not limited to this, and a ZF (Zero Forcing) criterion may be used, or MLD (Maximum Likelihood Detection) may be used.

  Moreover, in each said embodiment, the case where receiving device b1, b2 used the frequency | count of repetition as signal quality information was demonstrated. However, the present invention is not limited to this, and SINR (Signal to Interference and Noise Power Ratio), SNR (Signal to and Noise Power Ratio), or channel capacity is defined as signal quality. It may be used as information.

Specifically, the selection unit b114 calculates SINR (SINR _{2, k} ) of the k-th subcarrier for the signal output from the synthesis unit b115 in the case of the division error suppression method, using the following equation (19). To do.

In this case, the selection unit b114 determines that the division error suppression processing is performed when the SINR in Expression (19) is smaller than the predetermined threshold, and the division is performed when the SINR in Expression (19) is equal to or larger than the predetermined threshold. It is determined that error suppression processing is not performed.
Further, the selection unit b114 may use the SINR of the k-th subcarrier for the signal output from the synthesis unit b115 in the case of the division error non-suppression method as the signal quality information. SINR (SINR _{2, k} ) in this case is expressed by the following equation (20).

In this case, the selection unit b114 determines that the division error suppression process is performed when the SINR in Expression (20) is smaller than the predetermined threshold, and the division is performed when the SINR in Expression (20) is equal to or larger than the predetermined threshold. It is determined that error suppression processing is not performed.
When the signal quality information is SNR, σ _{1, k} ² and σ _{2, k} ² may be replaced with noise power ρ _N ² in equations (19) and (20).

Further, the selection unit b214 calculates the channel capacity C2 _{, k} of the k-th subcarrier for the signal output from the signal separation unit b215 in the case of the division error suppression method, using the following equation (21).

^{However, H} - (k) is ^H _{- b,} a matrix of _{N B} R rows and T columns arranged vertically for all b and r of the r (k). Further, log represents a logarithm, det represents a determinant, and I represents a unit matrix. X ^H represents a Hermitian matrix of X.
In this case, selection section b314 determines that performs suppression of division error when channel capacity _{C 2, k} of equation (21) is smaller than a predetermined threshold value, the channel capacity _{C 2, k} of equation (21) Is determined not to be subjected to the division error suppression process.
Further, the selection unit b214 may use the channel capacities C1 _{and k} of the k-th subcarrier for the signal output from the signal separation unit b215 in the case of the division error non-suppression method _, as signal quality information. The channel capacity C1 _{, k in} this case is expressed by the following equation (22).

In this case, selection section b314 determines that performs suppression of division error when channel capacity _{C 1, k} of formula (22) is smaller than a predetermined threshold value, the channel capacity _{C 1, k} of formula (22) Is determined not to be subjected to the division error suppression process.

A part of the receiving apparatus b1, b2 in the above-described embodiments, for example, division replica generating unit b111, (b) 211, the multipath dividing unit b 112, b 212, FFT section _{b113-1~b113-N} B, _{b213r-1~ b213r-N B,} the selection unit B 114, B 214, combining unit B115, B215 may be implemented by computer. In that case, the program for realizing the control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed. The “computer system” here is a computer system built in the receiving apparatus b1, and includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” is a medium that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, In such a case, a volatile memory inside a computer system serving as a server or a client may be included and a program that holds a program for a certain period of time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

a1, a2 ... transmitting device, b1, b2 ... receiving device, a101, a201-t ... pilot generation unit, a102, a202-t ... coding unit, a103, a203-t ... modulation Part, a104, a204-t ... mapping part, a105, a205-t ... IFFT part, a106, a206-t ... GI insertion part, a107, a207-t ... D / A conversion part, a108, a208-t ... transmission filter unit, a109, a209-t ... radio unit, a110, a210-t ... transmission antenna unit, b101, b201-r ... reception antenna, b102, b202- r ... wireless unit, b103, b203-r ... reception filter unit, b104, b204-r ... A / D conversion unit, b105, b205 ... propagation path estimation unit, b11 b21 ... signal detection unit, b106, b206-r ... demapping unit, b107, b207-r ... demodulation unit, b108, b208-r ... decoding unit, b109, b209-r ... symbol replica generation unit, b111, b211 ··· division for replica generation unit, b112, b212 ··· multipath dividing _{unit, b113-1~b113-N B, b213r-} 1~b213r-N B ··· FFT section , B114, b214 ... selection unit, b115 ... synthesis unit, b215 ... signal separation unit

Claims (14)

A replica of the received signal is generated based on the demodulated modulation symbol, and a replica of the received signal other than the path is removed from the received signal for each one or a plurality of paths, and the signal from which the replica is removed is the one or a plurality of paths In a wireless reception device that extracts based on information indicating each propagation path condition, repeats demodulating a combined signal as a result of combining, and extracts transmission data.
A selection unit that selects whether or not to perform signal addition processing for adding the removed replica component to the signal from which the replica has been removed based on signal quality information indicating the quality of the synthesized signal. Wireless receiver.   The selection unit according to claim 1, wherein when the signal quality information indicates that the quality is low, the selection unit selects to perform the signal addition processing and reduces an error caused by the removal. Wireless receiver.   The radio reception apparatus according to claim 1, wherein the selection unit selects not to perform the signal addition processing when the signal quality information indicates that the quality is high.   The selection unit switches between a first method for performing the signal addition processing and a second method for not performing the signal addition processing at least once in the repetitive processing. The wireless receiving device according to 1.   The radio reception apparatus according to claim 4, wherein the selection unit performs only switching from the first scheme to the second scheme in the repetitive processing.   The radio reception apparatus according to claim 1, wherein the signal quality information is the number of repetitions.   When the number of repetitions is smaller than a predetermined value, the selection unit determines that the number of repetitions indicates low quality, selects to perform the signal addition process, and causes an error caused by the removal. The radio reception apparatus according to claim 6, wherein   The selection unit, when the number of repetitions is larger than a predetermined value, determines that the number of repetitions indicates high quality, and selects not to perform the signal addition processing. 8. A wireless receiving device according to 7. The selection unit performs the signal addition processing for each subcarrier,
2. The radio receiving apparatus according to claim 1, wherein a component of the same subcarrier and the removed replica is added to a signal of each subcarrier of the signal from which the replica is removed.   The radio receiving apparatus according to claim 9, wherein the replica component is a component of a replica of a received signal of a path other than the one or a plurality of paths, and is a component in the same subcarrier.   The radio reception apparatus according to claim 1, wherein the selection unit changes the number of divisions of the one or more paths based on the signal quality information. A wireless reception device that performs MIMO communication, generates a replica of a received signal based on a demodulated modulation symbol, removes a replica of a received signal other than the path from the received signal for each of a plurality of paths, Radio reception for extracting transmission data by performing MIMO separation on the signal from which the replica has been removed based on information indicating propagation path conditions of each of the one or more paths, and demodulating the separated signal as a result of separation A device,
A selection unit that selects whether or not to perform signal addition processing for adding the removed replica component to the signal from which the replica has been removed, based on signal quality information indicating the quality of the demodulated separated signal; A wireless receiving device. A replica of the received signal is generated based on the demodulated modulation symbol, and a replica of the received signal other than the path is removed from the received signal for each one or a plurality of paths, and the signal from which the replica is removed is the one or a plurality of paths In the wireless reception method in the wireless reception device for extracting the transmission data by repeating the synthesis based on the information indicating the propagation path conditions, demodulating the combined signal of the combined result,
The selection unit has a selection process of selecting whether or not to perform signal addition processing for adding the removed replica component to the signal from which the replica has been removed, based on signal quality information indicating the quality of the synthesized signal. A wireless reception method. A replica of the received signal is generated based on the demodulated modulation symbol, and a replica of the received signal other than the path is removed from the received signal for each one or a plurality of paths, and the signal from which the replica is removed is the one or a plurality of paths A computer of a wireless reception device that extracts transmission data by repeatedly synthesizing based on information indicating each propagation path state and demodulating a combined signal as a result of the synthesis,
A radio reception program for functioning as selection means for selecting whether or not to perform signal addition processing for adding a component of the removed replica to a signal from which the replica has been removed, based on signal quality information indicating the quality of the synthesized signal .

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