Communication device and communication method

Abstract

To provide a communication device and a communication method capable of suppressing a degree to which a converted MER deviates from an ideal MER.SOLUTION: A communication device that receives a signal transmitted from a given device according to an MIMO scheme includes a decomposition unit that identifies a transmission weight matrix by applying singular value decomposition to an estimated channel matrix between the given device and the communication device, a quantization unit that identifies a quantized transmission weight matrix by quantizing the transmission weight matrix, a calculation unit that identifies an effective channel matrix on the basis of the estimated channel matrix and the quantized transmission weight matrix, and calculates a converted modulation error rate on the basis of, an inverse matrix of the effective channel matrix, a determination unit that determines at least a modulation scheme to be applied by the predetermined device on the basis of the converted modulation error rate, and a generation unit that generates, a parameter for identifying a modulation scheme to be applied by the predetermined device as a feedback parameter for the predetermined device.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a communication device and a communication method. [Background technology]

[0002] There is known a digital wireless transmission system in which a first device (e.g., FPU; Field Pickup Unit) transmits a digital signal wirelessly to a second device (e.g., a broadcasting station). In the digital wireless transmission system, eigenmode transmission methods (SVD-MIMO (Time Division Duplex-Singular Value Decomposition-Multiple-Input Multiple-Output) and E-SDM (Eigenbeam-Space Division Multiplexing) are being studied. In the eigenmode transmission method, transmission using independent transmission paths corresponding to the number of eigenmodes is realized by feeding back transmission parameters such as parameters related to a transmission weight matrix (hereinafter, weight parameters) from the second device to the first device. The independent transmission paths refer to equivalently orthogonal SISO (Single-Input Single-Output) transmission paths (e.g., Patent Document 1, Non-Patent Document 1). Furthermore, transmission from the first device to the second device can be performed with a large capacity and stability by adaptive control in which parameters related to MCS (Modulation and Coding Scheme) (hereinafter, MCS parameters) and the like are fed back from the second device to the first device.

[0003] Meanwhile, the second device estimates a channel matrix based on a signal received from the first device, and identifies a diagonal matrix composed of singular values ​​(hereinafter, singular value matrix) by applying singular value decomposition (SVD) to the estimated channel matrix. The second device identifies a transmission weight matrix to be fed back to the first device based on the channel matrix and the singular value matrix. The second device calculates a reduced modulation error ratio (hereinafter, reduced MER) based on the singular value diagonal matrix, and determines an MCS (MCS parameter) to be fed back to the first device based on the reduced MER. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6328021 [Non-patent literature]

[0005] [Non-Patent Document 1] "Portable microwave OFDM digital wireless transmission system for ultra-high definition television broadcasting program material transmission" Standard ARIB STD-B75 Version 1.0 Summary of the Invention [Problem to be solved by the invention]

[0006] As a result of careful investigation, the inventors have found that in an environment where the transmission weight matrix deteriorates, the calculation of the converted MER described above deviates from the ideal MER, and adaptive modulation cannot be applied appropriately.

[0007] Therefore, an object of the present invention is to provide a communication device and a communication method that make it possible to suppress the degree to which the converted MER deviates from the ideal MER. [Means for solving the problem]

[0008] A communication device according to one embodiment of the disclosure is a communication device that receives a signal transmitted from a specified device in accordance with a MIMO system, and includes a decomposition unit that determines a transmission weight matrix by applying singular value decomposition to an estimated propagation path matrix between the specified device and the communication device, a quantization unit that determines a quantized transmission weight matrix by quantizing the transmission weight matrix, a calculation unit that determines an effective propagation path matrix based on the estimated propagation path matrix and the quantized transmission weight matrix and calculates a reduced modulation error rate based on an inverse matrix of the effective propagation path matrix, a determination unit that determines at least a modulation scheme to be applied by the specified device based on the reduced modulation error rate, and a generation unit that generates parameters for determining the modulation scheme to be applied by the specified device as feedback parameters for the specified device.

[0009] A communication device according to one embodiment of the disclosure is a communication device that receives a signal transmitted from a specified device in accordance with a MIMO system, and includes: a decomposition unit that determines a transmission weight matrix by applying singular value decomposition to an estimated propagation path matrix between the specified device and the communication device; a calculation unit that determines an effective propagation path matrix based on the estimated propagation path matrix and the transmission weight matrix, calculates the accuracy of an inverse matrix of the effective propagation path matrix, and calculates a reduced modulation error rate based on the calculated accuracy; a determination unit that determines at least a modulation scheme to be applied by the specified device based on the reduced modulation error rate; and a generation unit that generates parameters for determining the modulation scheme to be applied by the specified device as feedback parameters for the specified device.

[0010] A communication method according to one embodiment of the disclosure is a communication method for transmitting a signal from a first device to a second device in accordance with a MIMO scheme, the method including the steps of: the second device specifying a transmission weight matrix by applying singular value decomposition to an estimated propagation path matrix between the first device and the second device; the second device specifying a quantized transmission weight matrix by quantizing the transmission weight matrix; the second device specifying an effective propagation path matrix based on the estimated propagation path matrix and the quantized transmission weight matrix, and calculating a reduced modulation error rate based on an inverse matrix of the effective propagation path matrix; the second device determining at least a modulation scheme to be applied by the first device based on the reduced modulation error rate; and the second device generating parameters for specifying the modulation scheme to be applied by the first device as feedback parameters for the first device.

[0011] A communication method according to one embodiment of the disclosure is a communication method for transmitting a signal from a first device to a second device in accordance with a MIMO system, comprising: a step in which the second device specifies a transmission weight matrix by applying singular value decomposition to an estimated propagation path matrix between the specified device and the communication device; a step in which the second device specifies an effective propagation path matrix based on the estimated propagation path matrix and the transmission weight matrix, calculates accuracy of an inverse matrix of the effective propagation path matrix, and calculates a reduced modulation error rate based on the calculated accuracy; a step in which the second device determines at least a modulation scheme to be applied by the specified device based on the reduced modulation error rate; and a step in which the second device generates parameters for specifying the modulation scheme to be applied by the specified device as feedback parameters for the specified device. Effect of the Invention

[0012] According to the present invention, it is possible to provide a communication device and a communication method that make it possible to suppress the degree to which the converted MER deviates from the ideal MER. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing a digital wireless transmission system 10 according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a transmission device 100 according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing a receiving device 200 according to the embodiment. [Figure 4] FIG. 4 is a diagram showing a receiving device 200 according to the embodiment. [Diagram 5] FIG. 5 is a diagram for explaining the experiment 1. In FIG. [Figure 6] FIG. 6 is a diagram for explaining the experiment 1. In FIG. [Figure 7] FIG. 7 is a diagram for explaining the experiment 2. In FIG. [Figure 8] FIG. 8 is a diagram for explaining the experiment 2. In FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Next, an embodiment of the present invention will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the ratios of dimensions may differ from the actual ones.

[0015] Therefore, specific dimensions should be determined with reference to the following description. In addition, the drawings may of course include parts with different dimensional relationships and ratios.

[0016] [Disclosure Summary] A communication device according to the outline of the disclosure is a communication device that receives a signal transmitted from a specified device in accordance with a MIMO system, and includes a decomposition unit that determines a transmission weight matrix by applying singular value decomposition to an estimated channel matrix between the specified device and the communication device, a quantization unit that determines a quantized transmission weight matrix by quantizing the transmission weight matrix, a calculation unit that determines an effective channel matrix based on the estimated channel matrix and the quantized transmission weight matrix and calculates a reduced modulation error rate based on an inverse matrix of the effective channel matrix, a determination unit that determines at least a modulation scheme to be applied by the specified device based on the reduced modulation error rate, and a generation unit that generates parameters for determining the modulation scheme to be applied by the specified device as feedback parameters for the specified device.

[0017] A communication method according to the outline of the disclosure is a communication method for transmitting a signal from a first device to a second device in accordance with a MIMO scheme, the method including the steps of: the second device specifying a transmission weight matrix by applying singular value decomposition to an estimated channel matrix between the first device and the second device; the second device specifying a quantized transmission weight matrix by quantizing the transmission weight matrix; the second device specifying an effective channel matrix based on the estimated channel matrix and the quantized transmission weight matrix, and calculating a reduced modulation error rate based on an inverse matrix of the effective channel matrix; the second device determining at least a modulation scheme to be applied by the first device based on the reduced modulation error rate; and the second device generating parameters for specifying the modulation scheme to be applied by the first device as feedback parameters for the first device.

[0018] In the outline of the disclosure, the communication device (second device) specifies an effective channel matrix based on an estimated channel matrix and a quantized transmission weight matrix, and calculates a reduced modulation error rate based on an inverse matrix of the effective channel matrix. With this configuration, it is possible to assume that the amount of noise emphasis that increases due to deterioration of the transmission weight matrix or the generation limit (precision) of the inverse matrix is ​​reflected in the reduced modulation error rate. Therefore, it is possible to suppress the degree to which the reduced modulation error rate deviates from the ideal modulation error rate.

[0019] [Embodiment] (Digital Radio Transmission System) A digital wireless transmission system according to an embodiment will be described below. Fig. 1 is a diagram showing a digital wireless transmission system 10 according to an embodiment. As shown in Fig. 1, the digital wireless transmission system includes a transmitting device 100 and a receiving device 200.

[0020] In the embodiment, the digital wireless transmission system is a system that supports wireless transmission of 4K8K broadcast program materials. The transmitting device 100 may be a Field Pickup Unit (FPU), and the receiving device 200 may be a broadcast station.

[0021] Here, transmitting device 100 has N antennas, and receiving device 200 has M antennas. In digital wireless transmission system 10, an N×M Multiple-Input Multiple-Output (MIMO) system is applied.

[0022] The digital wireless transmission system 10 employs an eigenmode transmission scheme (SVD-MIMO (Time Division Duplex-Singular Value Decomposition-Multiple-Input Multiple-Output) and E-SDM (Eigenbeam-Space Division Multiplexing). In the eigenmode transmission scheme, transmission is realized using k independent transmission paths corresponding to eigenmodes by singular value decomposition (SVD) of a propagation path matrix. k may be expressed as k=min(N,M).

[0023] In the following, a description will be mainly given of an operation of feeding back transmission parameters (hereinafter, FB parameters) such as parameters related to MCS (Modulation and Coding Scheme) (hereinafter, MCS parameters) and parameters related to a transmission weight matrix (hereinafter, weight parameters) from the receiving device 200 to the transmitting device 100. Therefore, a description of operations other than this operation will be omitted.

[0024] (Transmitting device) A transmitting device according to an embodiment will be described below. Fig. 2 is a block diagram showing a transmitting device 100 according to an embodiment. The transmitting device 100 constitutes a predetermined device or a first device that transmits a signal in accordance with the MIMO system.

[0025] As shown in FIG. 2, the transmitting device 100 includes an extracting unit 101, an adaptive modulating unit 103, and a transmitting unit 105.

[0026] The extraction unit 101 extracts the FB parameters received from the receiving device 200. As described above, the FB parameters include the MCS parameters and the weight parameters. The extraction unit 101 outputs the MCS parameters to the adaptive modulation unit 103 and outputs the weight parameters to the transmitting unit 105.

[0027] The MCS parameter may be any parameter for specifying the MCS to be applied to the transmission data. The MCS parameter may be a parameter that explicitly indicates the MSC, or may be a parameter that implicitly indicates the MCS. For example, the MCS parameter may be an index associated with a combination of MCSs to be applied to each eigenmode. In such a case, the association between the combination of MCSs to be applied to each eigenmode and an index is known to the transmitting device 100.

[0028] The weight parameters are eigenvectors that realize k eigenmodes corresponding to the k independent transmission paths. The weight parameters are parameters expressed by a matrix, and may be referred to as a transmission weight matrix V'. Since the transmission weight matrix V' is fed back from the receiving device 200, the details of the transmission weight matrix V' will be described later.

[0029] The adaptive modulation unit 103 specifies an MCS to be applied to the transmission data based on the MCS parameters. The adaptive modulation unit 103 performs adaptive modulation of the transmission data based on the specified MCS. The adaptive modulation unit 103 outputs a modulated signal x (symbol sequence x). The modulated signal x may be referred to as an original signal x before the transmission weight matrix is ​​applied.

[0030] The transmitter 105 generates a transmission signal V'x by multiplying the transmission weight matrix V' by an original signal x. The transmitter 105 transmits the transmission signal V'x to the receiver 200 in accordance with the MIMO scheme.

[0031] Although not shown in Fig. 2, the transmission data may be data to which error correction coding and interleaving processing have been applied. As the error correction code, a turbo code or a low-density parity-check code (LDPC) may be used.

[0032] (Receiving device) A receiving device according to an embodiment will be described below. Fig. 3 and Fig. 4 are block diagrams showing a receiving device 200 according to an embodiment. The receiving device 200 constitutes a communication device or a second device that receives signals in accordance with the MIMO system.

[0033] First, a configuration for receiving a signal transmitted from transmitting device 100 will be described.

[0034] As shown in FIG. 3, the receiving device 200 includes a receiving unit 201, a channel estimating unit 203, a compensating unit 205, and a demodulating unit 207.

[0035] The receiver 201 receives a signal transmitted from the transmitter 100 in accordance with the MIMO scheme. The receiver 201 receives a received signal (r UL ) to the channel estimation unit 203 and the compensation unit 205.

[0036] The channel estimation unit 203 estimates an estimated channel matrix H based on known pilot symbols. The channel estimation unit 203 specifies an effective channel matrix H' based on the estimated channel matrix H and a transmission weight matrix V'. The transmission weight matrix V' is a transmission weight matrix that has been fed back to the transmitting device 100. The estimated channel matrix H and the effective channel matrix H' may be expressed by the following equations. For example, the channel estimation unit 203 outputs HV' to the compensation unit 205.

[0037]

number

[0038] The compensation unit 205 calculates a receiving weight matrix, and based on the calculated receiving weight matrix, compensates for a signal (r UL ) is compensated for. Compensation section 205 outputs the signal compensated for by the receiving weight matrix to demodulation section 207.

[0039] The receiving weight matrix may be calculated by MMSE (Minimum Mean Square Error). In such a case, the receiving weight matrix may be expressed by the following equation.

[0040]

number

[0041] The receiving weight matrix may be calculated by ZF (Zero Forcing). In such a case, the receiving weight matrix may be expressed by the following equation.

[0042]

number

[0043] Demodulation section 207 performs adaptive demodulation of the signal compensated by the receiving weight matrix. Since it is assumed that the MCS parameters are fed back to transmitting apparatus 100, the MCS is known by demodulation section 207. Demodulation section 207 outputs the received data.

[0044] Secondly, a configuration for transmitting FB parameters to the transmitting device 100 will be described.

[0045] 4, the receiving device 200 has, in addition to the channel estimation unit 203, a decomposition unit 211, a quantization unit 213, a calculation unit 215, a determination unit 217, and a generation unit 219. In FIG. 4, the channel estimation unit 203 outputs an estimated channel matrix H.

[0046] Decomposition section 211 specifies transmission weight matrix V by applying singular value decomposition (SVD) to estimated channel matrix H between transmitting apparatus 100 and receiving apparatus 200. Singular value decomposition can be expressed by the following equation.

[0047]

number

[0048] In addition, by using singular value decomposition, the received signal y (for example, the above-mentioned r UL ) can be expressed by the following formula:

[0049]

number

[0050] The quantization unit 213 quantizes the transmission weight matrix V obtained by the singular value decomposition to identify the quantized transmission weight matrix V'. Hereinafter, the quantized transmission weight matrix V' may be simply referred to as the transmission weight matrix V'. Each element (component) constituting the transmission weight matrix V' may be represented by a 3-bit real part and a 3-bit imaginary part. The quantization unit 213 outputs the transmission weight matrix V to the calculation unit 215 and the generation unit 219.

[0051] The calculation unit 215 calculates a reduced modulation error ratio (hereinafter, reduced MER). The calculation unit 215 may calculate the reduced MER for each eigenmode. The calculation unit 215 specifies an effective channel matrix HV' based on the estimated channel matrix H and the quantized transmission weight matrix V', and calculates the reduced MER based on the inverse matrix of the effective channel matrix HV'. The following methods can be used to calculate the reduced MER.

[0052] First, the calculation unit 215 may calculate the converted MER according to the following formula (hereinafter, the first method).

[0053]

number

[0054] That is, in the first method, the calculation unit 215 calculates the deemed singular value ξ' based on the element h' constituting the inverse matrix of the effective channel matrix H' (HV'), and calculates the converted MER based on the calculated deemed singular value ξ'. It should be noted that the first method differs from the conventional method in that h' acquired based on the transmission weight matrix V' is used as the value of ξ. With this configuration, the amount of noise emphasis that increases due to degradation of the transmission weight matrix V can be appropriately reflected in the converted MER. Possible degradations of the transmission weight matrix V include quantization degradation, control delay degradation, and degradation of channel estimation accuracy.

[0055] Secondly, the calculation unit 215 may calculate the converted MER according to the following formula (hereinafter, the second method).

[0056]

number

[0057] That is, in the second method, the calculation unit 215 calculates the accuracy of the inverse matrix of the effective channel matrix H' (HV'), and calculates the converted MER based on the calculated accuracy. With this configuration, the interference components that increase due to the degradation of the transmission weight matrix V can be appropriately reflected in the converted MER. Possible degradations of the transmission weight matrix V include quantization degradation, control delay degradation, and degradation of channel estimation accuracy. Possible interference components include interference components that occur independently of the SNR due to the generation limit (accuracy) of the inverse matrix of the effective channel matrix H' when the SNR is high. The accuracy of the inverse matrix of the effective channel matrix H' is expressed by the following items.

[0058]

number

[0059] Thirdly, the calculation unit 215 may calculate the reduced MER according to the following formula (hereinafter, the third method). In the third method, the first method and the second method described above are combined. That is, in the second method described above, the deemed singular value ξ' described in the first method may be used.

[0060]

number

[0061] The determining unit 217 determines an adaptive modulation scheme (MCS) to be applied to the transmission data transmitted from the transmitting device 100, based on the reduced MER calculated by the calculating unit 215. The determining unit 217 may determine the MCS for each eigenmode. The determining unit 217 outputs information specifying the determined MCS to the generating unit 219.

[0062] The generating unit 219 generates FB parameters. The FB parameters include weight parameters related to the transmission weight matrix V'. The FB parameters include MCS parameters related to the MCS determined based on the converted MER calculated by any one of the first to third methods described above. The FB parameters are transmitted (feedback) from the receiving device 200 to the transmitting device 100.

[0063] (Action and Effects) In the embodiment, the receiving device 200 specifies an effective channel matrix HV' based on the estimated channel matrix H and the quantized transmission weight matrix V', and calculates a converted MER based on the inverse matrix of the effective channel matrix HV'. With such a configuration, it is possible to assume that the amount of noise emphasis that increases due to deterioration of the transmission weight matrix V or the generation limit (precision) of the inverse matrix is ​​reflected in the calculation of the converted MER. Therefore, it is possible to suppress the degree to which the converted MER deviates from the ideal MER.

[0064] In the embodiment, the receiving device 200 may calculate the deemed singular value ξ' based on elements constituting the inverse matrix of the effective channel matrix HV', and calculate the converted MER based on the calculated deemed singular value ξ'. With such a configuration, the amount of noise emphasis that increases due to the deterioration of the transmission weight matrix V can be appropriately reflected in the converted MER.

[0065] In the embodiment, the receiving device 200 may calculate the accuracy of the effective channel matrix HV' and calculate the converted MER based on the calculated accuracy. With this configuration, it is possible to appropriately reflect the interference components that increase due to the deterioration of the transmission weight matrix V in the converted MER.

[0066] [experiment] An experiment on the converted MER will be described below. In the experiment, the deviation between the converted MER and the ideal MER was confirmed in the low SNR region and the high SNR region. In the embodiment, the converted MER was calculated by the above-mentioned third method. On the other hand, in the comparative example, the converted MER was calculated by using the transmission weight matrix before quantization.

[0067] (Experiment 1) In experiment 1, the deviation between the converted MER and the ideal MER was confirmed under the following conditions.

[0068] Model: 1-path Rayleigh fading / Kronecker model Career: Single career Modulation method: QPSK Compensation method…ZF Degradation model: Considers quantization degradation of transmission weights

[0069] First, the experimental results in the low SNR region will be described with reference to Fig. 5. As shown in Fig. 5, in the comparative example, it was confirmed that the deviation between the converted MER and the ideal MER was 40 dB at maximum. Here, in the comparative example, the converted MER was calculated as a value higher than the ideal MER, so that the MCS could not be determined appropriately. On the other hand, in the embodiment, it was confirmed that the deviation between the converted MER and the ideal MER could be suppressed to 1 dB or less. Therefore, in the embodiment, the MCS can be determined appropriately.

[0070] Secondly, the experimental results in the high SNR region will be described with reference to Fig. 6. As shown in Fig. 6, in the comparative example, since the converted MER increases linearly, it was confirmed that the higher the SNR, the greater the deviation between the converted MER and the ideal MER. Here, in the comparative example, since the converted MER is calculated as a value higher than the ideal MER, the MCS cannot be appropriately determined. On the other hand, in the embodiment, since the interference components that occur independently of the SNR due to the generation limit (precision) of the inverse matrix are taken into account, it was confirmed that the deviation between the converted MER and the ideal MER can be suppressed to 1 dB or less. Therefore, in the embodiment, the MCS can be appropriately determined.

[0071] (Experiment 2) In experiment 2, the deviation between the converted MER and the ideal MER was confirmed under the conditions shown below.

[0072] Model: 1-path Rayleigh fading / Kronecker model Career: Single career Modulation method: QPSK Compensation method…ZF Degradation model: Considers control delay in addition to quantization degradation of transmission weight.

[0073] First, the experimental results in the low SNR region will be described with reference to Fig. 7. As shown in Fig. 7, in the comparative example, it was confirmed that the deviation between the converted MER and the ideal MER was 40 dB at maximum. Here, in the comparative example, since the converted MER is calculated as a value higher than the ideal MER, the MCS cannot be appropriately determined. On the other hand, in the embodiment, it was confirmed that the deviation between the converted MER and the ideal MER can be suppressed to 8 dB or less. Therefore, in the embodiment, the MCS can be appropriately determined.

[0074] Secondly, the experimental results in the high SNR region will be described with reference to Fig. 8. As shown in Fig. 8, in the comparative example, since the converted MER increases linearly, it was confirmed that the higher the SNR, the larger the deviation between the converted MER and the ideal MER. Here, in the comparative example, since the converted MER is calculated as a value higher than the ideal MER, the MCS cannot be appropriately determined. On the other hand, in the embodiment, since the interference components that occur independently of the SNR due to the generation limit (precision) of the inverse matrix are taken into account, it was confirmed that the deviation between the converted MER and the ideal MER can be suppressed to 8 dB or less. Therefore, in the embodiment, the MCS can be appropriately determined.

[0075] [Other embodiments] Although the present invention has been described by the above disclosure, the description and drawings forming a part of this disclosure should not be understood as limiting the present invention. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art.

[0076] In the above disclosure, in the second and third methods, a case has been described in which the converted MER is calculated based on the accuracy of the inverse matrix of the effective channel matrix H'. However, the above disclosure is not limited to this. When an interference component is reflected in the converted MER, the converted MER may be calculated based on the accuracy of the inverse matrix of the effective channel matrix H" (=HV). The accuracy of the inverse matrix of the effective channel matrix H" may be expressed by the following items.

[0077]

number

[0078] Although not specifically mentioned in the above disclosure, the digital wireless transmission system 10 may employ an Orthogonal Frequency Division Multiplexing (OFDM) system or a single carrier system.

[0079] Although not specifically mentioned in the above disclosure, the MCS parameters may include parameters that explicitly or implicitly indicate the transmission power to be applied to the transmission data. In such a case, the MCS parameters may include parameters that explicitly or implicitly indicate the combination of transmission power to be applied to each eigenmode.

[0080] In the above disclosure, the case where the transmitting device 100 is an FPU and the receiving device 200 is a broadcasting station has been described. However, the above disclosure is not limited to this. For example, the transmitting device 100 may be a mobile station and the receiving device 200 may be a base station.

[0081] Although not particularly mentioned in the above disclosure, a program may be provided that causes a computer to execute each process performed by the transmitting device 100 and the receiving device 200. The program may also be recorded in a computer-readable medium. Using the computer-readable medium, it is possible to install the program in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0082] Alternatively, a chip may be provided that is configured by a memory that stores a program for executing each process performed by the transmitting device 100 and the receiving device 200, and a processor that executes the program stored in the memory. [Explanation of symbols]

[0083] 10... digital wireless transmission system, 100... transmitting device, 101... extraction unit, 103... adaptive modulation unit, 105... transmitting unit, 200... receiving device, 201... receiving unit, 203... propagation path estimation unit, 205... compensation unit, 207... demodulation unit, 211... decomposition unit, 213... quantization unit, 215... calculation unit, 217... determination unit, 219... generation unit

Claims

1. A communication device that receives a signal transmitted from a predetermined device according to a multiple-input multiple-output (MIMO) system, a decomposition unit that specifies a transmission weight matrix by applying singular value decomposition to an estimated channel matrix between the predetermined device and the communication device; a quantization unit that quantizes the transmission weight matrix to identify a quantized transmission weight matrix; a calculation unit that specifies an effective channel matrix based on the estimated channel matrix and the quantized transmission weight matrix, and calculates a reduced modulation error rate based on an inverse matrix of the effective channel matrix; A determination unit that determines at least a modulation scheme to be applied in the predetermined device based on the converted modulation error rate; A communication device comprising: a generation unit that generates a parameter for specifying a modulation scheme to be applied in the specified device as a feedback parameter for the specified device.

2. The communication device according to claim 1 , wherein the calculation unit calculates assumed singular values ​​based on elements constituting an inverse matrix of the effective channel matrix, and calculates the reduced modulation error rate based on the calculated assumed singular values.

3. The communication device according to claim 1 , wherein the calculation unit calculates the accuracy of an inverse matrix of the effective channel matrix, and calculates the reduced modulation error rate based on the calculated accuracy.

4. A communication device that receives a signal transmitted from a predetermined device according to a multiple-input multiple-output (MIMO) system, a decomposition unit that specifies a transmission weight matrix by applying singular value decomposition to an estimated channel matrix between the predetermined device and the communication device; a calculation unit that specifies an effective channel matrix based on the estimated channel matrix and the transmission weight matrix, calculates the accuracy of an inverse matrix of the effective channel matrix, and calculates a reduced modulation error rate based on the calculated accuracy; A determination unit that determines at least a modulation scheme to be applied in the predetermined device based on the converted modulation error rate; A communication device comprising: a generation unit that generates a parameter for specifying a modulation scheme to be applied in the specified device as a feedback parameter for the specified device.

5. A communication method for transmitting a signal from a first device to a second device in accordance with a multiple-input multiple-output (MIMO) scheme, comprising: determining a transmission weight matrix by applying singular value decomposition to an estimated channel matrix between the first device and the second device; determining a quantized transmission weight matrix by the second device quantizing the transmission weight matrix; the second device specifying an effective channel matrix based on the estimated channel matrix and the quantized transmission weight matrix, and calculating a reduced modulation error rate based on an inverse matrix of the effective channel matrix; determining, by the second device, at least a modulation scheme to be applied by the first device based on the reduced modulation error rate; and generating, by the second device, a parameter for specifying a modulation scheme to be applied by the first device as a feedback parameter for the first device.

6. A communication method for transmitting a signal from a first device to a second device in accordance with a multiple-input multiple-output (MIMO) scheme, comprising: determining a transmission weight matrix by applying singular value decomposition to an estimated channel matrix between the first device and the second device; the second device specifying an effective channel matrix based on the estimated channel matrix and the transmission weight matrix, calculating accuracy of an inverse matrix of the effective channel matrix, and calculating a reduced modulation error rate based on the calculated accuracy; determining, by the second device, at least a modulation scheme to be applied by the first device based on the reduced modulation error rate; and generating, by the second device, a parameter for specifying a modulation scheme to be applied by the first device as a feedback parameter for the first device.

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