Wireless communication system and transmission device

Abstract

A wireless communication system according to one embodiment: acquires communication path matrices between a transmission station and a reception station; predicts the fluctuation value of each communication path matrix; calculates, on the basis of each fluctuation value, a precoding matrix for a case in which the transmission station and the reception station perform MIMO transmission; generates waveforms of radio waves for a case in which the transmission station and the reception station perform MIMO transmission by using the precoding matrices, and waveforms of radio waves for a case in which the transmission station and the reception station perform non-orthogonal multiple access; calculates the PAPR of each waveform of the generated radio waves; selects one of the smaller PAPRs; and performs control such that the transmission station and the reception station perform multiple access by means of MIMO transmission or non-orthogonal multiple access which results in the selected PAPR.

Description

Wireless communication system and transmitting device

[0001] The present invention relates to a wireless communication system and a transmitting device.

[0002] In wireless communication systems such as the fifth generation mobile communication system (5G), known technologies for improving frequency utilization efficiency include multiple input multiple output (MIMO) and non-orthogonal multiple access (NOMA).

[0003] In SU-MIMO (Single User-Multiple Input Multiple Output) and MU-MIMO (Multiple User-Multiple Input Multiple Output), spatial multiplexing is performed using at least one of analog beamforming and digital beamforming to improve frequency utilization efficiency (see, for example, Non-Patent Documents 1 and 2). In NOMA, signal superposition is performed in the power domain to improve frequency utilization efficiency.

[0004] Yoshio Karasawa, "MIMO Propagation Channel Modeling," Special Issue on Electromagnetic Field Analysis Methods and Design Techniques for Antennas and Propagation, IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J86-B, No. 9, pp. 1706-1720, September 2003. Kazuhiko Fukawa, "MIMO Transmission," [online], IEICE, IEICE Knowledge Base, Group 4, Part 1, Chapter 7, Ver. 1 / 2010.11.9, pp. 1-18, Internet, URL: https: / / www.ieice-hbkb.org / files / 04 / 04gun_01hen_07.pdf

[0005] In multiple access, it is possible to reduce the influence of nonlinear distortion of the power amplifier by using only the linear region of the input / output characteristics of the power amplifier that amplifies the transmission power, but this results in low power efficiency. Therefore, in multiple access, when nonlinear distortion occurs in the power amplifier, it is desirable to reduce the PAPR (Peak to Average Power Ratio) of the input signal to the power amplifier in order to reduce signal distortion.

[0006] In MIMO, when digital beamforming is performed, it is common to perform a precoding matrix operation that performs linear operations on transmission signals transmitted from each antenna. For the precoding matrix, for example, an eigenvector calculated by singular value decomposition such as equation (6) described in Non-Patent Document 1 is used.

[0007] However, in MIMO, when digital beamforming is performed, the radiated signals from each antenna are combined as the inner product of the signal and the row vector of the precoding matrix, which can increase the PAPR depending on the conditions of the channel matrix.

[0008] Therefore, if the back-off of the input to the power amplifier is insufficient, there is a concern that signal distortion may occur due to nonlinear distortion of the power amplifier.

[0009] Furthermore, in NOMA, signal superposition also increases the PAPR.

[0010] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a wireless communication system and a transmitting device that enable connection by power amplification with efficiently suppressed distortion.

[0011] A wireless communication system according to one embodiment of the present invention is a wireless communication system in which a transmitting station and a plurality of receiving stations perform multiple access, the system including: an acquisition unit that acquires channel matrices between the transmitting station and the receiving station, respectively; a prediction unit that predicts a fluctuation value of each of the channel matrices acquired by the acquisition unit; a first calculation unit that calculates a precoding matrix when each of the transmitting station and the receiving station performs MIMO transmission based on each of the fluctuation values ​​predicted by the prediction unit; and a waveform of a radio wave when each of the transmitting station and the receiving station performs MIMO transmission using the precoding matrix calculated by the first calculation unit, and a The present invention is characterized in that it comprises a waveform generation unit that generates waveforms of radio waves when the transmitting station and the receiving station each perform non-orthogonal multiple access, a second calculation unit that calculates a PAPR of each of the waveforms of the radio waves generated by the waveform generation unit, a selection unit that selects a smaller PAPR of either the PAPR when the MIMO transmission is performed or the PAPR when the non-orthogonal multiple access is performed, based on each of the PAPRs calculated by the second calculation unit, and a connection control unit that controls the transmitting station and the receiving station to perform multiple access using the MIMO transmission or the non-orthogonal multiple access that results in the PAPR selected by the selection unit.

[0012] Furthermore, a transmitting device according to one embodiment of the present invention is a transmitting device that performs multiple access with a plurality of receiving devices, and includes an acquiring unit that acquires a channel matrix between each of the receiving devices, a predicting unit that predicts a fluctuation value of each of the channel matrices acquired by the acquiring unit, a first calculating unit that calculates a precoding matrix when MIMO transmission is performed with each of the receiving devices based on each of the fluctuation values ​​predicted by the predicting unit, and a waveform of a radio wave when the MIMO transmission is performed with each of the receiving devices using the precoding matrix calculated by the first calculating unit. a waveform generation unit that generates waveforms of radio waves when performing non-orthogonal multiple access with each of the receiving devices; a second calculation unit that calculates the PAPR of each of the waveforms of the radio waves generated by the waveform generation unit; a selection unit that selects the smaller PAPR of either the PAPR when performing the MIMO transmission or the PAPR when performing the non-orthogonal multiple access based on the PAPRs calculated by the second calculation unit; and a connection control unit that controls to perform multiple access with each of the receiving devices using the MIMO transmission or the non-orthogonal multiple access that results in the PAPR selected by the selection unit.

[0013] According to the present invention, it is possible to provide a wireless communication system and a transmitting device that enable connection by power amplification with distortion efficiently suppressed.

[0014] FIG. 1 is a diagram illustrating an example of an overview when a wireless communication system according to an embodiment performs connection using spatial multiplexing. FIG. 2 is a diagram illustrating an example of an overview when a wireless communication system according to an embodiment performs connection using diversity and NOMA. FIG. 3 is a functional block diagram illustrating functions possessed by a transmitting station and a receiving station of the wireless communication system according to an embodiment. FIG. 4 is a diagram illustrating an example of a hardware configuration possessed by a transmitting station according to an embodiment.

[0015] A wireless communication system according to an embodiment will be described below with reference to the drawings. Fig. 1 is a diagram illustrating an example of an outline of a case where a wireless communication system 1 according to an embodiment performs connection using spatial multiplexing. Fig. 2 is a diagram illustrating an example of an outline of a case where a wireless communication system 1 according to an embodiment performs connection using diversity and NOMA.

[0016] 1, in a wireless communication system 1 according to an embodiment, for example, a transmitting station (transmitting device) 2 connects to multiple receiving stations (receiving devices) 3 using spatial multiplexing. The multiple receiving stations 3 are at different distances and positions from the transmitting station 2. Here, the use of spatial multiplexing refers to, for example, the case where power is allocated to multiple eigenmodes when power allocation is performed in MIMO using singular value decomposition.

[0017] 2 , in a wireless communication system 1 according to an embodiment, for example, a transmitting station (transmitting device) 2 connects to multiple receiving stations (receiving devices) 3 using diversity and NOMA. The multiple receiving stations 3 are at different distances and positions from the transmitting station 2. Here, the use of diversity refers to, for example, a case where power is allocated only to a first eigenmode in MIMO using singular value decomposition.

[0018] In other words, the wireless communication system 1 according to one embodiment is configured so that the transmitting station 2 can connect to multiple receiving stations 3 using spatial multiplexing, or using diversity and NOMA.

[0019] 3 is a functional block diagram illustrating functions of a transmitting station 2 and a receiving station 3 of a wireless communication system 1 according to an embodiment. The transmitting station 2 includes a signal processing unit 20 having a pilot signal transmitting unit 200 that transmits a pilot signal to the receiving station 3, and a control unit 22. The receiving station 3 includes a signal processing unit 30.

[0020] The signal processing unit 30 of the receiving station 3 includes a channel matrix calculation unit 300 , a transmission processing unit 302 , and a communication unit 304 .

[0021] The channel matrix calculation unit 300 calculates a channel matrix (time domain / frequency domain, scalar / vector / matrix / transfer function, etc.) for the communication channel between the transmitting station 2 and the receiving station 3 using the pilot signal transmitted by the pilot signal transmission unit 200 of the transmitting station 2, and outputs the calculated channel matrix to the transmission processing unit 302.

[0022] The transmission processing unit 302 performs feedback by transmitting the channel matrix calculated by the transmission processing unit 302 to the transmitting station 2 .

[0023] The communication unit 304 performs wireless communication with the transmitting station 2 in response to control from the transmitting station 2 .

[0024] The signal processing unit 20 of the transmitting station 2 includes the above-described pilot signal transmitting unit 200, receiving processing unit 202, waveform generating unit 204, and communication unit 206. The control unit 22 of the transmitting station 2 includes an acquiring unit 220, a predicting unit 221, a first calculating unit 222, a second calculating unit 223, a selecting unit 224, and a connection control unit 225.

[0025] The reception processing unit 202 receives the channel matrix transmitted by the reception processing unit 202 of the receiving station 3 and outputs it to the acquisition unit 220 of the control unit 22 .

[0026] The acquisition unit 220 acquires the channel matrices between the transmitting station 2 and the receiving station 3 from the reception processing unit 202 and outputs them to the prediction unit 221 .

[0027] The prediction unit 221 predicts the variation value of each channel matrix acquired by the acquisition unit 220 and outputs the predicted value to the first calculation unit 222. Specifically, the prediction unit 221 predicts the variation value of each channel matrix based on the channel matrices for a predetermined number of past frames calculated by the channel matrix calculation unit 300. When predicting the variation value using machine learning such as a neural network, the prediction unit 221 may perform learning in advance using a database calculated from a predetermined model formula.

[0028] The reason why the prediction unit 221 predicts the fluctuation values ​​of each channel matrix in this way is that, for example, if the channel matrix fluctuates from moment to moment, the channel matrix calculated by the channel matrix calculation unit 300 may differ from the channel matrix when a signal is actually transmitted between the transmitting station 2 and the receiving station 3. Even if the transmitting station 2 performs precoding for multiplexing or diversity utilization using a channel matrix different from the actual one, there is a risk that the communication capacity will be significantly reduced. For this reason, the transmitting station 2 does not acquire and use the channel matrix in real time, but predicts and uses the channel matrix in advance.

[0029] The first calculation unit 222 calculates a precoding matrix for when the transmitting station 2 and the receiving station 3 perform MIMO transmission based on the fluctuation values ​​of each communication channel matrix predicted by the prediction unit 221, and outputs the calculated precoding matrix to the waveform generation unit 204.

[0030] For example, when the first calculation unit 222 calculates a precoding matrix from the fluctuation values ​​(predicted values) of each channel matrix predicted by the prediction unit 221, the first calculation unit 222 may use the eigenvectors calculated from the above-mentioned singular value decomposition as the precoding matrix.

[0031] The waveform generation unit 204 generates the waveform of radio waves when the transmitting station 2 and the receiving station 3 each perform MIMO transmission using the precoding matrix calculated by the first calculation unit 222, and the waveform of radio waves when the transmitting station 2 and the receiving station 3 each perform NOMA, and outputs them to the second calculation unit 223.

[0032] The second calculation unit 223 calculates the PAPR of each of the waveforms of the radio waves generated by the waveform generation unit 204 and outputs the PAPR to the selection unit 224 .

[0033] Based on the PAPRs calculated by the second calculation unit 223, the selection unit 224 selects the smaller PAPR of either the PAPR when MIMO transmission is performed or the PAPR when NOMA is performed, and outputs the selection result to the connection control unit 225.

[0034] The connection control unit 225 controls the transmitting station 2 and the receiving station 3 to perform multiple access using MIMO transmission or NOMA that results in the PAPR selected by the selection unit 224. Furthermore, when the transmitting station 2 and the receiving station 3 perform NOMA, the connection control unit 225 controls the transmitting station 2 and the receiving station 3 to combine or select multiple received waves using diversity using multiple antennas.

[0035] For example, the communication units 206 and 304 perform wireless communication using MIMO transmission or diversity and NOMA under the control of the connection control unit 225 .

[0036] In this way, the wireless communication system 1 according to one embodiment predicts the fluctuation value of each communication channel matrix, selects the smaller PAPR of either the PAPR when MIMO transmission is performed or the PAPR when NOMA is performed, and performs multiple access using MIMO transmission or NOMA that results in the selected PAPR, thereby enabling connection between the transmitting station 2 and the receiving station 3 using power amplification with efficiently suppressed distortion.

[0037] Note that each function possessed by the transmitting station 2 and the receiving station 3 may be partially or entirely configured by hardware such as a programmable logic device (PLD) or a field programmable gate array (FPGA), or may be configured as a program executed by a processor such as a CPU.

[0038] For example, the transmitting station 2 and the receiving station 3 can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network. Furthermore, each function of the transmitting station 2 and the receiving station 3 may be configured to be provided by either the transmitting station 2 or the receiving station 3.

[0039] 4 is a diagram illustrating an example of a hardware configuration of a transmission station 2 according to an embodiment. As illustrated in FIG. 4, the transmission station 2 has, for example, an input unit 50, an output unit 51, a communication unit 52, a CPU 53, a memory 54, and an HDD 55 connected via a bus 56, and functions as a computer. The transmission station 2 is also configured to input and output data to and from a computer-readable storage medium 57.

[0040] The input unit 50 is, for example, a keyboard and a mouse. The output unit 51 is, for example, a display device such as a display that outputs images. The communication unit 52 is, for example, a wireless network interface, and may have a function as an output unit that outputs data to the outside.

[0041] As described above, the CPU 53 controls each component of the transmitting station 2 and performs predetermined processing, etc. The memory 54 and the HDD 55 are storage units that store data, etc.

[0042] The storage medium 57 is capable of storing programs and the like that cause the transmitting station 2 to execute the functions of the transmitting station 2. The architecture that configures the transmitting station 2 is not limited to the example shown in FIG.

[0043] The functions performed by the components described herein may be implemented in circuitry or processing circuitry, including general purpose processors, application specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the described functions.

[0044] A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may be a programmed processor that executes programs stored in memory.

[0045] In this specification, a circuitry, unit, or means is hardware that is programmed to realize or performs the described functions, which may be any hardware disclosed herein or any hardware known to be programmed to realize or perform the described functions.

[0046] If the hardware is a processor considered to be a type of circuitry, the circuitry, means, or unit is a combination of the hardware and software used to configure the hardware and / or processor.

[0047] 1...wireless communication system, 2...transmitting station (transmitting device), 3...receiving station (receiving device), 20...signal processing unit, 22...control unit, 30...signal processing unit, 50...input unit, 51...output unit, 52...communication unit, 53...CPU, 54...memory, 55...HDD, 56...bus, 57...storage medium, 200...pilot signal transmitting unit, 202...receiving processing unit, 204...waveform generating unit, 206...communication unit, 220...acquisition unit, 221...prediction unit, 222...first calculation unit, 223...second calculation unit, 224...selection unit, 225...connection control unit, 300...communication channel matrix calculation unit, 302...transmission processing unit, 304...communication unit

Claims

1. A wireless communication system in which a transmitting station and a plurality of receiving stations perform multiple access, comprising: an acquisition unit that acquires channel matrices between the transmitting station and the receiving station, respectively; a prediction unit that predicts fluctuation values ​​of the channel matrices acquired by the acquisition unit; a first calculation unit that calculates a precoding matrix when the transmitting station and the receiving station perform MIMO transmission, respectively, based on the fluctuation values ​​predicted by the prediction unit; a waveform generation unit that generates, using the precoding matrices calculated by the first calculation unit, waveforms of radio waves when the transmitting station and the receiving station perform MIMO transmission, and waveforms of radio waves when the transmitting station and the receiving station perform non-orthogonal multiple access, respectively; a second calculation unit that calculates a PAPR for each of the waveforms of the radio waves generated by the waveform generation unit; and a selection unit that selects, based on the PAPRs calculated by the second calculation unit, the smaller PAPR of the PAPR when the MIMO transmission is performed or the PAPR when the non-orthogonal multiple access is performed. a connection control unit that controls the transmitting station and the receiving station to perform multiple access by the MIMO transmission or the non-orthogonal multiple access that results in the PAPR selected by the selection unit.

2. The wireless communication system according to claim 1, wherein the prediction unit predicts the fluctuation value of each channel matrix using past channel matrices for a predetermined number of frames.

3. The wireless communication system according to claim 1 or 2, characterized in that the connection control unit controls the combining or selection of multiple received waves by diversity using multiple antennas when the transmitting station and the receiving station each perform the non-orthogonal multiple access.

4. A transmitting device that performs multiple access with a plurality of receiving devices, comprising: an acquiring unit that acquires a channel matrix between each of the receiving devices; a predicting unit that predicts a fluctuation value of each of the channel matrices acquired by the acquiring unit; a first calculating unit that calculates a precoding matrix when MIMO transmission is performed with each of the receiving devices based on each of the fluctuation values ​​predicted by the predicting unit; a waveform generating unit that generates a radio wave waveform when MIMO transmission is performed with each of the receiving devices and a radio wave waveform when non-orthogonal multiple access is performed with each of the receiving devices using the precoding matrix calculated by the first calculating unit; a second calculating unit that calculates a PAPR for each of the radio wave waveforms generated by the waveform generating unit; and a selecting unit that selects the smaller PAPR of the PAPR when MIMO transmission is performed or the PAPR when non-orthogonal multiple access is performed based on each of the PAPRs calculated by the second calculating unit. a connection control unit that controls the transmission device to perform multiple access with each of the receiving devices by the MIMO transmission or the non-orthogonal multiple access that results in the PAPR selected by the selection unit.

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