JP2011244063A - Radio communication system, transmitter, receiver, communication method, transmission method, and reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means such as a radio communication system which provides an excellent characteristic between a transmitter and a receiver without deploying many repeaters.SOLUTION: A transmitter 101 transmits transmission streams to a receiver 103 and transmits to a repeater 102 transmission streams fewer than the transmission streams sent to the receiver 103. The repeater 102 receives a signal including the streams transmitted by the transmitter 101, amplifies the received signal, and transmits the amplified signal to the receiver. The receiver 103 demodulates the transmission streams receiving all of streams transmitted to the receiver 103 by the repeater 102 and the transmitter 101.

Description

  The present invention relates to a wireless communication system or the like capable of MIMO communication including a transmission device, at least one relay device, and a reception device.

  In recent years, in the field of wireless communication, as a technique for realizing high-speed transmission, by using a plurality of transmission / reception antennas, a plurality of independent transmission signals are transmitted from a wireless transmission device to a wireless reception device at the same frequency and the same timing. Attention has been focused on MIMO (Multiple Input Multiple Output) transmission that can increase the transmission rate without widening the frequency bandwidth.

  However, in order to obtain good reception characteristics in MIMO transmission, there are many scatterers such as buildings between the transmission device and the reception device, and the spatial correlation needs to be low as in an environment where reception is performed via various paths. . When the number of scatterers is small, the spatial correlation becomes high, and it becomes difficult to separate spatially multiplexed MIMO signals, so that there is a problem that transmission characteristics are greatly deteriorated.

  In response to such a problem, for example, in Patent Document 1, as shown in FIG. 12, a signal transmitted from a transmission device 5001 having a plurality of antennas is transmitted to a plurality of relay devices 5002-1 to 5002-2. A technique of receiving via a reception device 5003 including a plurality of antennas via the network is disclosed. This realizes a MIMO transmission technique with small spatial correlation by regarding a plurality of relay devices as scatterers.

JP 2003-198442 A

  However, in the technique disclosed in Patent Document 1 described above, when the spatial correlation between the transmission apparatus and one relay apparatus is high, a large number of relay apparatuses are required to lower the spatial correlation. There was a problem that.

  In view of the above-described problems, an object of the present invention is to provide a wireless communication system or the like in which good characteristics can be obtained between a transmission device and a reception device without arranging many relay devices.

In view of the problems described above, the wireless communication system of the present invention is a wireless communication system capable of MIMO communication including a transmission device, at least one relay device, and a reception device,
The transmitter is
A transmission unit that transmits a stream to the relay device and the reception device, and that transmits a stream having a number of streams smaller than the number of streams transmitted by the transmission device to the relay device;
The relay device is
A relay unit that receives a signal including a stream transmitted by the transmission device, amplifies the received signal, and transmits the amplified signal to the reception device;
The reception apparatus includes a signal detection unit that receives a stream transmitted from the relay apparatus and the transmission apparatus to the reception apparatus, and performs signal detection on the received stream.

  In the wireless communication system of the present invention, the transmission device transmits at least one same stream from the transmission unit to the reception device and the relay device.

In the radio communication system according to the present invention, the transmission device may be configured such that the number of streams transmitted to the relay device and / or the reception device is one in the transmission unit.
Moreover, in the wireless communication system of the present invention, the transmission device includes:
A precoding unit that performs precoding to separate a stream to be transmitted to the relay device and a stream to be transmitted to the reception device;
The transmission unit transmits the pre-coded stream to the relay device or the reception device.

A transmission apparatus according to the present invention is a transmission apparatus that transmits a stream to at least one relay apparatus and a reception apparatus via a wireless communication system capable of MIMO communication.
A transmission unit that transmits a stream to the relay device and the reception device, and that transmits a transmission stream having a number of streams smaller than the number of streams transmitted by the transmission device to the relay device;
A precoding unit that performs precoding such that at least one stream is transmitted to both the relay device and the receiving device using report information received from the relay device and the receiving device;
It is characterized by providing.

Moreover, the transmission device of the present invention is
A stream selection unit that selects the number of streams to be transmitted to each of the relay apparatuses and the reception apparatus based on the report information is further provided.
In the transmission device of the present invention,
The precoding unit performs precoding so that each of the relay apparatuses and the reception apparatus do not interfere with each other.

The receiving apparatus of the present invention is
A receiving apparatus that receives a signal in which a first stream having a delay time difference within a guard interval length and a second stream having a delay time difference exceeding a guard interval are spatially multiplexed.
A decoding unit that performs error correction decoding to obtain a bit log likelihood ratio;
A channel estimation unit that performs channel estimation and obtains a channel estimation value;
A signal detector that performs MIMO separation from the received signal, the bit log likelihood ratio, and the channel estimation value to obtain the bit log likelihood ratio;
With
The signal detection unit performs sequential interference cancellation for MIMO separation by changing the detection order of the first stream and the second stream depending on whether or not the initial process has never been decoded. Features.

In the receiving device of the present invention,
In the first process, the signal detection unit detects the first stream before the second stream.

In the receiving device of the present invention,
The signal detection unit may detect the second stream before the first stream when the first process is not performed.

The communication method of the present invention includes:
A communication method in a wireless communication system capable of MIMO communication including a transmission device, at least one relay device, and a reception device,
The transmission device transmits a stream to the relay device and the reception device, and transmits to the relay device a transmission stream having a number of streams smaller than the number of streams transmitted by the transmission device,
The relay device is
Receiving and amplifying a signal including a stream transmitted by the transmission device, and transmitting the amplified signal to the reception device;
The receiving apparatus receives all streams transmitted from the relay apparatus and the transmitting apparatus to the receiving apparatus, and decodes the transmission stream.

The transmission method of the present invention includes:
A transmission method of transmitting a stream to at least one relay device and a reception device via a wireless communication system capable of MIMO communication,
Transmitting a stream to the relay device and the receiving device, and transmitting to the relay device a transmission stream having a number of streams smaller than the number of streams transmitted by the transmitting device;
Precoding is performed such that different streams are transmitted to each of the relay device and the reception device using report information received from the relay device and / or the reception device.

The receiving method of the present invention includes:
A reception method for receiving a signal in which a first stream having a delay time difference within a guard interval length and a second stream having a delay time difference exceeding a guard interval are spatially multiplexed.
Perform error correction decoding to obtain a bit log likelihood ratio and a channel estimation to obtain a channel estimation value,
Performing MIMO separation from the received signal, the bit log likelihood ratio and the channel estimation value to further determine the bit log likelihood ratio,
It is characterized by performing sequential interference cancellation for MIMO separation by changing the detection order of the first stream and the second stream depending on whether or not the initial processing has never been decoded.

  According to the present invention, when a stream is transmitted from a transmission apparatus to a reception apparatus, MIMO separation performance is improved without arranging a large number of relay apparatuses by transmitting different streams to each relay apparatus. Is possible. Therefore, appropriate communication can be performed even with a small number of relay apparatuses in the wireless communication system.

1 is an overall view of a wireless communication system in a first embodiment. It is a figure for demonstrating the function structure of the transmitter in 1st Embodiment. It is a figure for demonstrating the function structure of the receiver in 1st Embodiment. It is a figure for demonstrating the function structure of the signal detection part in 1st Embodiment. It is a flowchart for demonstrating the flow of the process in 1st Embodiment. It is a whole figure of the radio | wireless communications system in 2nd Embodiment. It is a figure for demonstrating the function structure of the transmitter in 2nd Embodiment. It is a figure for demonstrating the function structure of the receiver in 2nd Embodiment. It is a figure for demonstrating the function structure of the signal detection part in 2nd Embodiment. It is a flowchart for demonstrating the flow of the transmission process in 2nd Embodiment. It is a flowchart for demonstrating the flow of the reception process in 2nd Embodiment. 1 is an overall view of a wireless communication system in the prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where OFDM (Orthogonal Frequency Division Multiplexing) is used will be described. However, the scope of application of the present invention is not limited to this, and other multi-carrier transmission and single-carrier transmission may be used. Can also be applied.

[1. First Embodiment]
[1.1 System configuration]
FIG. 1 is a schematic diagram of a wireless communication system in the first embodiment. The wireless communication system includes a transmission apparatus 101, a relay apparatus 102 (relay apparatus 102-1 and relay apparatus 102-2), and a reception apparatus 103. A case where two streams are transmitted from the transmission apparatus 101 to the reception apparatus 103 will be described.

  Here, each of the transmission apparatus 101 and the reception apparatus 103 includes a plurality of antennas. The relay apparatuses 102-1 and 102-2 have one or more antennas. Unless otherwise specified, a case will be described in which the relay apparatus 102 amplifies and retransmits a received signal, for example, a repeater or an Amplify-and-Forward relay.

  At this time, the receiving apparatus 103 can receive the signal transmitted from the transmitting apparatus 101 and the signal relayed by the relay apparatus 102 with the same resource. The transmission apparatus 101 transmits a stream to be transmitted to the relay apparatus 102-1 and a stream to be transmitted to the relay apparatus 102-2 separately.

Here, the stream represents an independent signal sequence spatially multiplexed by the transmission apparatus. For example, assume that the transmission apparatus 101 transmits independent streams of S = [x1 x2] ^T.

  T represents transposition of the matrix. The relay apparatus 102 may be placed in a line-of-sight environment with the transmission apparatus 101 because stable and good reception performance can be obtained. In this case, the spatial correlation between the transmission apparatus 101 and one relay apparatus 102 becomes high, the relay apparatus 102 relays a signal having a high spatial correlation, and if the number of relay apparatuses 102 is small, the spatial correlation is increased. Without being lowered, the MIMO separation performance is degraded.

Therefore, the transmission apparatus 101 according to the present embodiment, for example, has different streams for each relay apparatus, such as S1 = [x1] ^T for the relay apparatus 102-1 and S2 = [x2] ^{T for} the relay apparatus 102-2. Then, S3 = [x1 x2] ^T is transmitted to the receiving apparatus 103 by spatial multiplexing.

  Since there is a delay due to relay processing in the relay apparatus 102, the reception apparatus 103 has S1 and S2 relayed by the relay apparatuses 102-1 and 102-2 as delay waves with respect to S transmitted from the transmission apparatus 101. Received.

[1.2 Device configuration]
Here, the configuration of each apparatus will be described with reference to the drawings.

[1.2.1 Transmitter]
First, the configuration of the transmission apparatus 101 will be described. FIG. 2 is a block diagram illustrating a configuration of the transmission apparatus 101 when two streams are transmitted using four transmission antennas. Transmitting apparatus 101 includes coding sections 210-1, 201-2, modulation sections 202-1, 202-2, allocation sections 203-1, 203-2, pilot generation section 204, precoding section 205, IFFT (fast inverse Fourier transform). Transform: Inverse Fast Fourier Transform) units 206-1 to 206-4, GI (Guard Interval) insertion units 207-1 to 207-4, radio transmission units 208-1 to 208-4, and transmission antenna 209-1 To 209-4.

  The transmission bits are encoded by the encoding units 201-1 and 201-2 using an error correction code such as a convolutional code, a turbo code, or an LDPC (Low Density Parity Check) code, and the encoded bits are the modulation unit. 202-1 to 202-2 are mapped to modulation symbols such as PSK (Phase Shift Keying) and QAM (Quadrature Amplitude Modulation).

  Modulation symbols are allocated to time / frequency resources by allocation sections 203-1 and 203-2 together with pilot signals known on the transmission / reception side generated by pilot generation section 204. The precoding unit 205 performs precoding so that a desired stream is transmitted to the relay apparatuses 102-1 and 102-2 and the receiving apparatus 103.

The precoded signal is frequency-time converted by IFFT sections 206-1 to 206-4, guard intervals are inserted by GI insertion sections 207-1 to 207-4, and radio transmission sections 208-1 to 208-4 are inserted. D / A conversion and conversion to a radio frequency are performed and transmitted from the transmission antennas 209-1 to 209-4.
Here, details of the precoding unit 205 will be described. An example will be described in which the transmission apparatus 101 transmits two streams x1 and x2 from four transmission antennas. It is assumed that S1 = [x1] is transmitted to the relay apparatus 102-1, S2 = [x2] ^T is transmitted to the relay apparatus 102-2, and S3 = [x1 x2] ^T is transmitted to the receiving apparatus 103.

The channel between the transmission device 101 and the relay device 102-1 is H ₁ , the channel between the transmission device 101 and the relay device 102-2 is H ₂ , and the channel between the transmission device 101 and the reception device 103 is H ₃ . In the present embodiment, as an example, the number of transmission / reception antennas of the relay apparatuses 102-1 and 102-2 will be described as one, and the number of reception antennas of the reception apparatus will be two, but it is needless to say that the number is not limited thereto. At this time, H ₁ and H ₂ are a matrix of 1 row and 4 columns, and H ₃ is a matrix of 2 rows and 4 columns.

It is assumed that the transmitting apparatus 101 knows (stores) H ₁ and H ₂ from the report information from the relay apparatuses 102-1 and 102-2, or knows in advance. H ₃ is the report information from the receiver 103, it is assumed that the transmitting apparatus 101 knows (stored).

First, the plurality of relay apparatuses 102-1 and 102-2 and the receiving apparatus 103 are diagonalized. As shown in the following equation, singular value decomposition is performed on the channels H _RS and H ₃ between the transmission device and the relay device.

However, _URS is a 2 × 2 unitary matrix, _DRS is a 2 × 4 diagonal matrix having singular values as diagonal elements, and _VRS is a 4 × 4 unitary matrix. U ₃ is a 2 × 2 unitary matrix, D ₃ is a 2 × 4 diagonal matrix having singular values as diagonal elements, and V ₃ is a 4 × 4 unitary matrix. Superscript H represents the complex conjugate transpose of the matrix. The transmission weight W can be set as follows, for example, so that signals transmitted to the relay device and the reception device do not interfere with each other.

Note that v _3,3 , v _3,4 are the third column vector and the fourth column vector of V ₃ , respectively, and v _{RS, 3} , v _{RS, 4} are the third column vector and the fourth column of V _RS , respectively. Is a vector. Assuming that H = [H _RS ^T H ₃ ] ^T , the equivalent channel when W is multiplied and transmitted is as follows.

Expression (6) indicates that transmission can be performed to a plurality of relay apparatuses and reception apparatuses without interference. Here again, H _RS ′ = H _RS W _{RS, 1} , H ₁ ′ = [H ₁ v _3,3 H ₁ v _3,4 ], H ₂ ′ = [H ₂ v _3,3 H ₂ v _{3, 4} ]. By multiplying _HRS ′ by a weight, a desired signal is transmitted to a plurality of relay apparatuses. Singular value decomposition is performed on H ₁ ′ and H ₂ ′ as in the following equation.

Where U ₁ is a 1 × 1 unitary matrix, D ₁ is a 1 × 2 diagonal matrix with singular values as diagonal elements, V ₁ is a 2 × 2 unitary matrix, and U ₂ is 1 A unitary matrix of row 1 column, D ₂ is a 1 × 2 diagonal matrix having singular values as diagonal elements, and V ₂ is a 2 × 2 unitary matrix. In order to transmit a desired stream to the relay apparatuses 102-1 and 102-2, the following weights are used.

Multiplying H _RS 'by the weight of equation (9) yields:

Accordingly, the overall weight W ′ is as follows.

となり、送信装置１０３から中継装置１０２−１にはＳ１、送信装置１０３から中継装置１０２−２にはＳ２、送信装置１０３から受信装置１０３にはＳ３が送信されていることがわかる。 The signal to be precoded by W ′ is S = [S1 S2 S3] ^T , the signal received by the relay device 102-1 is Y1, the signal received by the relay device 102-2 is Y2, and the transmission device receives the signal by the receiving device 103. If the signal from 103 is Y3,

Thus, S1 is transmitted from the transmission apparatus 103 to the relay apparatus 102-1, S2 is transmitted from the transmission apparatus 103 to the relay apparatus 102-2, and S3 is transmitted from the transmission apparatus 103 to the reception apparatus 103.

[1.2.2 Receiver]
Next, the configuration of the receiving apparatus 103 will be described. FIG. 3 is a block diagram illustrating a configuration of the reception device 103. Receiving antennas 301-1 and 301-2, radio receiving units 302-1 and 302-2, propagation path estimating unit 303, signal detecting unit 304, decoding units 305-1 and 305-2, and report information generating unit 306 are provided. Composed.

  The received waves received by the receiving antennas 301-1 and 301-2 are converted from radio frequency to baseband and A / D converted by the radio receiving units 302-1 and 302-2 and output as received signals.

  The propagation path estimation unit 303 performs propagation path estimation based on the received signal and the pilot signal, and outputs the propagation path estimation value to the signal detection unit 304 and the report information generation unit 306. The report information generation unit 306 generates report information to the transmission apparatus 101 from the propagation path estimated value. The report information is information necessary for precoding, for example, information indicating a propagation path between the transmission apparatus 101 and the reception apparatus 103.

  Since the receiving apparatus 103 receives S3 = [x1 x2] from the transmitting apparatus 101 and S1 = [x1] and S2 = [x2] from the relay apparatuses 102-1 and 102-2, respectively, it is detected by the receiving apparatus 103. The stream [x1 x2] to be received is received as a MIMO signal having a large delay time difference. Here, the delay time difference is a time difference between a path arriving first and a path arriving last in the path estimated by the receiving apparatus.

  In particular, when there is a delay time difference that exceeds the guard interval length, inter-symbol interference (ISI: Inter Symbol Interference) from adjacent OFDM symbols or ICI (Inter-Symbol Interference Interference), which is interference between subcarriers, occurs. As a result, transmission characteristics deteriorate. For this reason, the signal detection unit 304 performs ISI, ICI suppression, and MIMO separation, and calculates and outputs a coded bit LLR (Log Likelihood Ratio).

  Decoding unit 305-1 to decoding unit 305-2 performs error correction decoding on the input coded bit LLR, and outputs a decoded transmission bit if there is no error in the decoding result, and there is an error in the decoding result. In this case, the decoded encoded bit LLR is output to the signal detection unit 304.

  A CRC (Cyclic Redundancy Check) code may be used for error detection of the decoding result. It is assumed that the maximum number of repetitions of the signal detection unit 304 and the decoding units 305-1 and 305-2 is determined in advance. The number of iterations may be checked by the decoding units 305-1 and 305-2.

  Here, the signal detection unit 304 will be described in more detail with reference to FIG. The signal detection unit 304 includes an interference replica generation unit 401, an interference removal unit 402, GI removal units 403-1 and 403-2, FFT (Fast Fourier Transform) units 404-1, 404-2, and a MIMO separation unit. 405 is configured.

  Interference replica generation section 401 generates an interference replica that is a replica of an interference signal from coded bits LLR obtained from decoding sections 305-1 to 305-2 and a propagation path estimation value obtained from propagation path estimation section 303. Here, the interference signal is inter-stream interference (MSI) by ISI, ICI, and MIMO spatial multiplexing.

  The interference replica generation unit 401 does not need to generate all the replicas of ISI, ICI, and MSI, and may generate at least one interference replica. The MSI replica may not be generated by the interference replica generation unit 401 but may be generated by a MIMO separation unit 405 described later.

  The interference replica generated by the interference replica generation unit 401 is subtracted from the received signal by the interference removal unit 402 to suppress interference. If no decoding has been performed, an interference replica cannot be generated, and the interference removal unit 402 outputs the received signal as it is.

  In the signal after interference removal, the guard interval is removed by the GI removal units 403-1 and 403-2, the time frequency conversion is performed by the FFT units 404-1 and 404-2, and the MIMO separation is performed by the MIMO separation unit 405. Thus, the coded bit LLR is obtained.

  As a technique for MIMO separation, conventional techniques such as MMSE (Minimum Mean Square Error) detection, MLD (Maximum Likelihood Detection), or the like may be used.

Let the kth subcarrier of the signal after interference cancellation be R (k), the channel matrix of the kth subcarrier be H (k), and the kth subcarrier of the stream detected by the receiving apparatus 103 be S (k). When performing MMSE detection, the following may be performed.

S ^ (k) represents S (k) after detection, and M (k) is an MMSE weight as shown in the following equation.

Or

Σ _n ² represents average noise power, and I represents a unit matrix. The detected S ^ (k) is demodulated to obtain a coded bit LLR. Further, the MLD obtains the encoded bit LLR as follows.

Note that the LLR of the q-th bit b _{t, q} of the t-th stream is λ (b _{t, q} ). Β ₊ is a sequence where b _{t, q} = 0 (or +1) among the bit sequences that can constitute S (k), and β ₋ is b _{t, q} among the bit sequences that can constitute S (k). = 1 (or -1).

[1.2.3 Relay device]
Next, the relay apparatus 102 will be described. The relay device is a device that includes a reception unit that receives a signal as a relay unit, an amplification unit that amplifies the received signal, and a transmission unit that transmits the amplified signal again.

  The so-called relay device 102 is configured by a conventionally known relay station device or the like, and has a relay unit that amplifies and retransmits a received signal, and a detailed description thereof is omitted.

[1.3 Process flow]
FIG. 5 is a flowchart of the transmission process in this embodiment. First, in step s501, error correction coding is performed on the transmission bits, and modulation is performed in step s502. In step s503, modulation symbols are assigned to time / frequency resources. In step s504, precoding is performed so that a desired stream is transmitted to each relay apparatus and reception apparatus. In step s505, frequency / time conversion is performed, in step s506, a guard interval is inserted, and transmission is performed in step s507.

  As described above, in this embodiment, different streams are transmitted to each relay apparatus. This makes it possible to improve the MIMO separation performance without arranging a large number of relay apparatuses.

[2. Second Embodiment]
Next, the second embodiment will be described.

[2.1 System configuration]
FIG. 6 is a schematic diagram of a wireless communication system according to the second embodiment. The wireless communication system includes a transmission device 601, a relay device 602, and a reception device 603. In the first embodiment, all streams are received by the receiving apparatus as signals having a large delay time difference due to relay. However, in this embodiment, some streams are received by the receiving apparatus as signals having a large delay time difference due to relay. . For example, the transmission apparatus 601 transmits two streams x1 and x2. When S1 = [x1] and S2 = [x1 x2], S1 is transmitted to the relay apparatus 602, and S2 is transmitted to the reception apparatus 603. To do.

[2.2 Device configuration]
Next, the device configuration in this embodiment will be described.

[2.2.1 Transmitter]
FIG. 7 is a block diagram illustrating a configuration of the transmission apparatus 601. The transmission apparatus 601 includes a stream selection unit 701, an encoding / modulation selection unit 702, encoding units 703-1 to 703-2, modulation units 704-1 to 704-2, a pilot generation unit 705, and allocation units 706-1 to 706. -2, Precoding section 707, IFFT sections 708-1 to 708-3, GI insertion sections 709-1 to 709-3, wireless transmission sections 710-1 to 710-3, and transmission antennas 711-1 to 711-3 It is prepared for.

  The stream selection unit 701 selects a stream to be transmitted to the relay device 602 and the reception device 603 from the report information reported from the relay device 602 and the reception device 603, and outputs the stream to the encoding / modulation selection unit 702 and the precoding unit 707. .

  The coding / modulation selection unit 702 selects a coding rate and a modulation scheme for each stream. In this embodiment, some streams are transmitted from the transmission device 601 and the relay device 602. Accordingly, although there is interference due to delay, the received power is larger than that of the other streams, so that the transmission rates of the streams transmitted from both the transmission apparatus 601 and the relay apparatus 602 are higher than the transmission rates of the other streams. It is also possible to determine the coding rate and modulation method.

  In the example of the present embodiment, the transmission rate of the stream x1 is higher than that of the stream x2. According to the coding rate and modulation method selected by the coding / modulation selection unit 702, the coding units 703-1 and 703-2 and the modulation units 704-1 and 704-2 perform error correction coding and modulation.

  Allocation sections 706-1 and 706-2 allocate the pilot signal and modulation symbol generated by pilot generation section 705 to time / frequency resources. The precoding unit 707 performs precoding so as to transmit a desired stream to the relay apparatus 602 and the reception apparatus 603 as in the first embodiment.

In precoding, the relay device 602 and the receiving device 603 are block-diagonalized as in the first embodiment, and the signal to be precoded is S = [S1 S2] ^T. The signal after precoding is frequency-time converted by IFFT sections 708-1 to 708-3, guard intervals are inserted by GI insertion sections 709-1 to 709-3, and D is transmitted by radio transmission sections 710-1 to 710-3. / A conversion and radio frequency conversion are performed and transmitted from the transmission antennas 711-1 to 711-3.

[2.2.2 Receiver]
Next, the configuration of the receiving device 603 will be described. FIG. 8 is a block diagram illustrating a configuration of the receiving device 603. The reception device 603 includes reception antenna units 801-1 and 801-2, radio reception units 802-1 and 802-2, a propagation path estimation unit 803, a signal detection unit 804, decoding units 805-1 and 805-2, and report information. A generation unit 806 is provided.

  The received waves received by the receiving antennas 801-1 and 801-2 are converted from radio frequency to baseband and A / D converted by the radio receiving units 802-1 and 802-2, and output as received signals.

  The propagation path estimation unit 803 performs propagation path estimation based on the received signal and the pilot signal, and outputs the propagation path estimation value to the signal detection unit 804 and the report information generation unit 806.

  Report information generation section 806 generates report information to transmission apparatus 601 from the propagation path estimation value. Since the receiving apparatus 603 receives S2 = [x1 x2] from the transmitting apparatus 601 and S1 = [x1] from the relay apparatus 602 with the same resource, among the streams [x1 x2] to be detected by the receiving apparatus 603, x1 is It is received as a signal with a large delay time difference.

  The signal detection unit 804 performs ISI, ICI suppression, and x1 and x2 MIMO separation for x1, and calculates and outputs a coded bit LLR (Log Likelihood Ratio).

  The decoding units 805-1 and 805-2 perform error correction decoding on the input coded bit LLR, and output the decoded transmission bit if there is no error in the decoding result, and if there is an error in the decoding result The decoded encoded bit LLR is output to the signal detection unit 804. The signal detection unit 804 can perform the same processing as the signal detection unit 304 of the first embodiment, but in the second embodiment, there is a bias in the delay time difference between streams. Will be explained.

  In the received signal of this embodiment, there are a stream that is not relayed (referred to as a first stream) and a stream that has a large delay time difference that exceeds the GI due to relaying (referred to as a second stream).

  In this example, x2 is the first stream and x1 is the second stream. The second stream has higher reception power than the first stream, but ISI and ICI exist. This means that the reception quality of the second stream varies greatly depending on the difference in reception method, that is, whether or not ISI and ICI are suppressed.

  Using this, the signal detection unit 804 performs successive interference cancellation (SIC) for MIMO separation. SIC can obtain good characteristics by performing detection and removal in the order of good reception quality.

  For this reason, in the initial processing in which ISI and ICI replicas cannot be generated, the first stream is detected and removed from the first stream because the reception quality is better than the second stream. In the second and subsequent times when ISI and ICI can be suppressed, detection / removal is performed from the second stream, assuming that the second stream has better reception quality than the first stream.

  FIG. 9 is a block diagram illustrating a configuration of the signal detection unit 804. The signal detection unit 804 includes an interference replica generation unit 901, an interference removal unit 902, GI removal units 903-1 and 903-2, FFT units 904-1 and 904-2, an inter-stream interference replica generation unit 905, a subtraction unit 906, A MIMO separation unit 907 is provided.

  First, the initial process will be described. Since the decoding has not been performed yet in the initial processing, guard interval removal is performed on the received signal by the GI removal units 903-1 and 903-2, and time frequency conversion is performed by the FFT units 904-1 and 904-2. Done.

  Again, since decoding has not yet been performed, the inter-stream interference replica generation unit 905 cannot generate an inter-stream interference replica, so the MIMO separation unit 907 performs MIMO separation on the outputs of the FFT units 904-1 and 904-2.

  For the MIMO separation method, the MMSE detection described in the first embodiment may be performed. Among the detected streams, the encoded bit LLR of the first stream is output to the decoding unit. The inter-stream interference replica generation unit generates a reception replica of the first stream as the inter-stream interference replica from the encoded bit LLR of the first stream after decoding, and the subtraction unit 906 includes FFT units 904-1 and 904-2. The inter-stream interference replica is subtracted from the signal output by. The MIMO separation unit 907 performs MMSE detection on the signal in which the first stream is suppressed, and outputs the detected encoded bit LLR of the second stream to the decoding unit. This is the first process.

  Next, the second and subsequent cases will be described. Since the decoding is performed after the second time, the ISI and ICI replicas are generated by the interference replica generation unit 901, and the ISI and ICI replicas are subtracted from the received signal by the interference removal unit 902. To suppress. The guard interval is removed from the output signal of the interference removal unit 902 by the GI removal units 903-1 and 903-2, and the time frequency is converted by the FFT units 904-1 and 904-2.

  In the second and subsequent times, since ISI and ICI are suppressed, detection is performed from the second stream. The inter-stream interference replica generation unit 905 generates a first inter-stream interference replica as an inter-stream interference replica from the coded bit LLR of the first stream, removes it from the outputs of the FFT units 904-1 and 904-2, Perform MMSE-based MIMO separation.

  The encoded bit LLR of the second stream after detection is output to the decoding unit and subjected to error correction decoding. The newly decoded encoded bit LLR of the second stream is input to the signal detection unit 804 again.

  The inter-stream interference replica generation unit 905 generates a reception replica of the second stream as the inter-stream interference replica using the encoded bit LLR of the second stream, and the inter-stream interference replica is the FFT in the subtraction unit 906. Subtracted from the outputs of the sections 904-1 and 904-2.

  The MIMO separation unit 907 performs MMSE-based MIMO separation on the output signal of the subtraction unit 906, and outputs the encoded bit LLR of the first stream to the decoding unit.

[2.3 Process flow]
[2.3.1 Transmission processing]
FIG. 10 is a flowchart of the transmission process of the transmission apparatus 601. In step s1001, the stream transmitted to the relay apparatus 602 and the stream transmitted to the reception apparatus overlap at least partially based on the report information from the relay apparatus 602 and the reception apparatus 603 known by the transmission apparatus 601. Select In step s1002, a coding rate and a modulation scheme are selected so that a transmission rate of a stream transmitted to both the relay device and the reception device is higher than that of the other streams.

  In step s1003, encoding and modulation are performed according to the code rate and modulation method selected in step s1002. Step s1004 allocates modulation symbols to time / frequency resources. Step s1005 is precoded so that the stream selected in step s1001 is transmitted to the relay device or the receiving device. The signal after precoding is frequency-time converted in step s1006, a guard interval is inserted in step s1007, and transmitted in step s1008.

[2.3.2 Reception processing]
FIG. 11 is a flowchart of the reception process of the reception device 603. In step s1101, it is determined whether or not the process is an initial process.

  If it is determined that the process is an initial process, the process proceeds to step s1102. Step s1102 removes a guard interval (GI) from the received signal, and step s1103 performs frequency-time conversion (FFT).

  In step s1104, first, MIMO separation is performed to detect the first stream to obtain the coded bit LLR. The encoded bit LLR of the first stream is subjected to error correction decoding, a reception replica of the first stream is generated from the obtained encoded bit LLR, and is removed from the received signal.

  In step s1105, MIMO separation is performed on the signal in which the first stream is suppressed, the second stream is detected to obtain a coded bit LLR, and error correction is performed on the coded bit LLR of the second stream. Decrypt.

  In step s1106, it is determined whether there is no error in the error correction decoding results of the first stream and the second stream, or whether a predetermined number of processes have been performed, and there is no error in the decoding result, or the predetermined number of times. When the above process is performed, the transmission bit obtained by decoding is output and the process is terminated.

  If there is an error in the decoding result and the predetermined number of processes have not been performed, the process proceeds to step s1101.

  Next, a case where the initial process is not performed in step s1101 will be described. In step s1107, ISI and ICI interference replicas are generated from the coded bits LLR of the first stream and the second stream obtained in the previous process.

  In step s1108, ISI and ICI interference replicas are subtracted from the received signal to suppress ISI and ICI. In step s1109, the guard interval (GI) is removed, and in step s1110, time frequency conversion (FFT) is performed.

  In step s1111, a reception replica of the first stream is generated from the encoded bit LLR of the first stream obtained in the immediately preceding process, and is removed from the signal obtained in step s1110.

  The signal in which the first stream is suppressed is subjected to MIMO separation, and the second stream is detected to obtain the encoded bit LLR. Error correction decoding is performed on the encoded bit LLR after detection to obtain the encoded bit LLR. A reception replica is generated from the coded bits LLR of the second stream after decoding, and is removed from the signal obtained in step s1110.

  In step s1112, MIMO separation is performed on the signal in which the second stream obtained in step s1111 is suppressed to obtain coded bits LLR, and the process proceeds to step s1106.

  As described above, in the present embodiment, the transmission device 601 transmits a part of the stream to the relay device 602 and the reception device 603. For this reason, streams with different reception environments are generated, and more efficient communication can be performed by performing processing using this difference.

[3. Modified example]
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and the like within the scope of the present invention are also within the scope of the claims. include.

  In the first and second embodiments, the case where one stream is transmitted to the relay device has been described as an example. However, embodiments to which the present invention can be applied are not limited to this, and the transmission device transmits to the reception device. If the number of streams is less than the number of streams to be transmitted, a plurality of streams can be sent to the relay apparatus.

  In the second embodiment, the number of streams is 1 for both the first stream and the second stream. However, the embodiment to which the present invention is applicable is not limited to this, and the first stream is also the first stream. The two streams may be a plurality of streams.

  Further, in the first and second embodiments, the case where the transmission device transmits all the streams to be transmitted to the reception device has been described. However, embodiments to which the present invention can be applied are not limited thereto, and There may be a stream that does not communicate directly between the receiving apparatuses but only through the relay apparatus.

  In the first and second embodiments, the transmission apparatus transmits a plurality of streams to the reception apparatus. However, the embodiment to which the present invention can be applied is not limited to this, and one stream is transmitted to the reception apparatus. May be sent.

  The program that operates in the transmission device, the reception device, and the relay device according to the present invention is a program (a program that causes a computer to function) that controls the CPU and the like so as to realize the functions of the embodiments according to the present invention. Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU, and corrected and written as necessary. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

  In the case of distribution in the market, the program can be stored and distributed in a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Moreover, you may implement | achieve part or all of the mobile station apparatus and base station apparatus in embodiment mentioned above as LSI which is typically an integrated circuit. Each functional block of the transmission device, the reception device, and the relay device may be individually chipped, or a part or all of them may be integrated into a chip. When each functional block is integrated, an integrated circuit controller for controlling them is added.

  Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

101 Transmitting devices 201-1 to 201-2 Encoding unit 202-1 to 202-2 Modulating unit 203-1 to 203-2 Allocation unit 204 Pilot generating unit 205 Precoding unit 206-1 to 206-4 IFFT unit 207-1 207-4 GI insertion unit 208-1 to 208-4 wireless transmission unit 209-1 to 209-4 transmission antenna 102, 102-1 and 102-2 relay device 103 reception device 301-1 to 301-2 reception antenna 302 -1 to 302-2 Radio reception unit 303 Propagation path estimation unit 304 Signal detection unit 401 Interference replica generation unit 402 Interference removal unit 403-1 to 403-2 GI removal unit 404-1 to 404-2 FFT unit 405 MIMO separation unit 305-1 to 305-2 Decoding unit 306 Report information generation unit

Claims (13)

A wireless communication system capable of MIMO communication including a transmission device, at least one relay device, and a reception device,
The transmitter is
A transmission unit that transmits a stream to the relay device and the reception device, and that transmits a stream having a number of streams smaller than the number of streams transmitted by the transmission device to the relay device;
The relay device is
A relay unit that receives a signal including a stream transmitted by the transmission device, amplifies the received signal, and transmits the amplified signal to the reception device ;
The wireless communication system, wherein the reception device includes a signal detection unit that receives a stream transmitted from the relay device and the transmission device to the reception device, and performs signal detection on the received stream. The wireless communication system according to claim 1, wherein the transmission device transmits at least one same stream from the transmission unit to the reception device and the relay device.   3. The wireless communication system according to claim 1, wherein in the transmission device, the number of streams transmitted to the relay device and / or the reception device is one in the transmission unit. The transmitter is
Further comprising a precoding section that performs precoding that separate the stream to be transmitted with the stream to be transmitted to the relay device to the receiving device,
4. The wireless communication system according to claim 1, wherein the transmission unit transmits the pre-coded stream to the relay device or the reception device. 5. A transmission device that transmits a stream to at least one relay device and a reception device via a wireless communication system capable of MIMO communication,
A transmission unit that transmits a stream to the relay device and the reception device, and that transmits a transmission stream having a number of streams smaller than the number of streams transmitted by the transmission device to the relay device;
A precoding unit that performs precoding such that at least one stream is transmitted to both the relay device and the receiving device using report information received from the relay device and the receiving device;
A transmission device comprising: On the basis of the report information, respectively, transmitting apparatus according to claim 5, further comprising a stream selector for selecting the number of streams to be transmitted to said receiving device of the relay device. The precoding unit, respectively, transmitting apparatus according to claim 5 or 6, characterized in that the precoding such that the receiving device does not cause interference with each other of the relay device. A receiving apparatus that receives a signal in which a first stream having a delay time difference within a guard interval length and a second stream having a delay time difference exceeding a guard interval are spatially multiplexed.
A decoding unit that performs error correction decoding to obtain a bit log likelihood ratio;
A channel estimation unit that performs channel estimation and obtains a channel estimation value;
A signal detector that performs MIMO separation from the received signal, the bit log likelihood ratio, and the channel estimation value to obtain the bit log likelihood ratio;
With
The signal detection unit performs sequential interference cancellation for MIMO separation by changing the detection order of the first stream and the second stream depending on whether or not the initial process has never been decoded. A receiving device.   The receiving apparatus according to claim 8, wherein the signal detection unit detects the first stream before the second stream in the case of initial processing.   The receiving apparatus according to claim 8, wherein the signal detection unit detects the second stream before the first stream when the initial processing is not performed. A communication method in a wireless communication system capable of MIMO communication including a transmission device, at least one relay device, and a reception device,
The transmission device transmits a stream to the relay device and the reception device, and transmits to the relay device a transmission stream having a number of streams smaller than the number of streams transmitted by the transmission device,
The relay device is
Receiving and amplifying a signal including a stream transmitted by the transmission device, and transmitting the amplified signal to the reception device;
The receiving apparatus receives all the streams transmitted from the relay apparatus and the transmitting apparatus to the receiving apparatus, and decodes the transmission stream. A transmission method of transmitting a stream to at least one relay device and a reception device via a wireless communication system capable of MIMO communication,
Transmitting a stream to the relay device and the receiving device, and transmitting to the relay device a transmission stream having a number of streams smaller than the number of streams transmitted by the transmitting device;
A transmission method comprising performing precoding such that different streams are transmitted to each of the relay device and the receiving device, using report information received from the relay device and / or the receiving device. A reception method for receiving a signal in which a first stream having a delay time difference within a guard interval length and a second stream having a delay time difference exceeding a guard interval are spatially multiplexed.
Perform error correction decoding to obtain a bit log likelihood ratio and a channel estimation to obtain a channel estimation value,
Performing MIMO separation from the received signal, the bit log likelihood ratio and the channel estimation value to further determine the bit log likelihood ratio,
A receiving method, wherein sequential interference cancellation is performed for MIMO separation by changing the detection order of the first stream and the second stream depending on whether or not the initial process has never been decoded.

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