Receiving device and wireless communication method

Abstract

To reduce a deterioration in communication quality in a situation in which overloaded MIMO easily occurs.SOLUTION: A reception-side apparatus comprises: M receiving antennas; and a control unit that executes first processing of acquiring a first signal from a first transmission-side apparatus from among signals simultaneously received from N transmission-side apparatuses through receive diversity processing, and acquiring first data by demodulating and decoding the first signal. In a case of N>M in the first processing, the control unit acquires, for all patterns of the combinations of the first signal, second signals that are from M-1 transmission-side apparatuses and cancelled in the receive diversity processing, and third signals that are from N-M transmission-side apparatuses and not cancelled in the receive diversity processing, the power ratio of the power of the first signal relative to the total power of the second signals and the third signals based on a predetermined weight and channel estimates of the signals, and selects a combination with the largest power ratio from among all the patterns.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to wireless communications. [Background technology]

[0002] There is an increasing need to use terminals that can connect to public networks such as the Internet for control, and there is a demand for low latency wireless communication to access public networks. Meanwhile, multiple input multiple output (MIMO) is used in wireless communication. MIMO is a technology in which a base station and a terminal communicate in the same frequency band using multiple antennas. In addition, in MIMO, a technology in which multiple terminals are involved in communication simultaneously is called multi-user MIMO. Along with the development of such wireless communication technology, the number of terminals accessing public networks is predicted to increase in the future, raising concerns about the congestion of uplinks.

[0003] Meanwhile, in wireless communication, a communication procedure called Configured Grant (CG) is prescribed. An example of a communication procedure that does not rely on CG is Dynamic grant. In Dynamic grant, a terminal transmits a Scheduling Request (SR) to a base station when transmitting data to the base station. Then, the base station designates to the terminal the radio resources that can be used for the data transmission by using Downlink Control Information (DCI), and grants permission for the transmission. The terminal then receives permission to transmit and transmits data to the base station using the designated radio resources.

[0004] In contrast, in CG, the base station transmits transmission parameters that specify the physical resources that can be used for data transmission in advance to the terminal. The base station then notifies the terminal of the start and end of permission for data transmission by CG. However, the transmission parameters for physical resources and the permission start may be transmitted at the same time. This allows the terminal to immediately use the specified physical resources to transmit data to the base station without transmitting an SR and without receiving a DCI. In this way, in communication using CG, the terminal can transmit data to the base station without omitting negotiation with the base station. For this reason, CG is expected to be a technology that will realize low-latency communication. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Hiroshi Suzuki, "Signal Transmission Characteristics in Least-Squares Combining Diversity Reception - Relationship between Desired Signal Combining and Interference Signal Cancellation -", IEICE Transactions on Information and Communication Engineers, August 1992, B-II Vol. J75-B-II, No.8, pp.524-534 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the communication illustrated in CG increases the number of terminals (N) that transmit to the base station at the same time. When the number of terminals (N) that transmit at the same time is greater than the number of receiving antennas (M) of the base station, this is called overloaded MIMO.

[0007] An object of the disclosed embodiments is to suppress deterioration of communication quality in situations where overloaded MIMO is likely to occur. [Means for solving the problem]

[0008] One aspect of the present disclosure is M receiving antennas, A control unit that executes a first process of acquiring a first signal from a first transmitting device among N transmitting devices by a receiving diversity process from signals simultaneously received from the N transmitting devices, and demodulating and decoding the first signal to acquire first data, The control unit, in the first processing, When the number N of the transmitting side devices is greater than the number M of the receiving antennas, acquiring all patterns of combinations of signals from the N transmitting side devices classified into the first signal from the first transmitting side device, the second signal from M-1 transmitting side devices that is canceled by the receiving diversity processing, and the third signal from NM transmitting side devices that is not canceled by the receiving diversity processing; For all of the patterns, obtain a power of the first signal and a power of the second signal based on a weight used in the diversity reception processing of each pattern, and obtain a power of the third signal from a channel estimation value; obtaining a power ratio of a power of the first signal to a total power of the second signal and the third signal; performing the diversity reception processing on the combination that maximizes the power ratio after the diversity reception processing, and determining the combination of signals to be demodulated; The receiving device.

[0009] Another aspect of the present disclosure is A receiving device having M receiving antennas, A wireless communication method including: performing a first process of acquiring a first signal from a first transmitting device, which is one of N transmitting devices, by a receive diversity process from signals simultaneously received from the N transmitting devices, and demodulating and decoding the first signal to acquire first data, In the first process, When the number N of the transmitting side devices is greater than the number M of the receiving antennas, acquiring all patterns of combinations of signals from the N transmitting side devices classified into the first signal from the first transmitting side device, the second signal from M-1 transmitting side devices that is canceled by the receiving diversity processing, and the third signal from NM transmitting side devices that is not canceled by the receiving diversity processing; For all of the patterns, obtain a power of the first signal and a power of the second signal based on a weight used in the diversity reception processing of each pattern, and obtain a power of the third signal from a channel estimation value; obtaining a power ratio of a power of the first signal to a total power of the second signal and the third signal; performing the diversity reception processing on the combination that maximizes the power ratio after the diversity reception processing, and determining the combination of signals to be demodulated; A wireless communication method.

[0010] According to one aspect of the present disclosure, it is possible to suppress deterioration of communication quality in a situation where overloaded MIMO is likely to occur. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a hardware configuration of the base station according to the first embodiment. [Diagram 3] FIG. 3 is a block diagram illustrating a configuration of a terminal. [Figure 4] FIG. 4 is a block diagram illustrating the configuration of a base station. [Diagram 5] FIG. 5 is a flowchart illustrating the processing of the base station. [Figure 6] FIG. 6 is a flowchart illustrating a procedure of reception processing by the base station and the terminal using CG. [Figure 7]FIG. 7 is a flowchart of a process for separating a desired signal in a base station. [Figure 8] FIG. 8 is a diagram illustrating the channel matrices H and R. [Figure 9] FIG. 9 is a diagram illustrating the channel matrices H and R. [Figure 10] FIG. 10 is an example of a flowchart of a process for reducing combination patterns in a base station. [Figure 11] FIG. 11 is an example of a flowchart of a combination selection process in a base station. [Figure 12] FIG. 12 shows an example of the simulation conditions. [Figure 13] FIG. 13 is a diagram showing an example of a simulation result by the processing according to the first embodiment. [Figure 14] FIG. 14 is a diagram showing an example of a simulation result by the processing according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] First Embodiment FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to a first embodiment. This wireless communication system includes a base station 1 and a plurality of terminals 2-1, 2-2, ..., 2-N that communicate wirelessly between the base station 1. The terminals 2-1, etc. are also collectively referred to as terminals 2. In this embodiment, an overloaded MIMO wireless communication system in which the number of terminals N is greater than the number of receiving antennas M at the base station in multi-user MIMO is exemplified. The terminals 2 can be referred to as wireless communication terminals.

[0013] In the case of normal MIMO, where the number of transmitting terminals (N) is equal to or less than the number of receiving antennas (M) of the base station, for example, a predetermined weight W of receiving diversity can be used to extract a desired signal from one terminal and cancel signals from other terminals as interference signals. On the other hand, in the case of overloaded MIMO, the number of transmitting terminals (N) is greater than the number of receiving antennas (M) of the base station, so signals from MN terminals cannot be canceled even if a predetermined weight W of receiving diversity is used. Signals from MN terminals that cannot be canceled remain as interference signals, and there is a risk that the error rate will increase due to the influence of the interference signals when demodulating the desired signal. Note that being able to cancel interference signals means suppressing interference caused by interference signals on the desired signal.

[0014] When the number of transmitting terminals (N) is greater than the number of receiving antennas (M) of a base station, the signals are classified into desired signals, interference signals to be cancelled (M-1), and interference signals that are not cancelled (NM), and receive diversity processing is performed. However, no method has been proposed for classifying signals from N transmitting terminals into desired signals, interference signals to be cancelled (M-1), and interference signals that are not cancelled (NM).

[0015] In one aspect of the present disclosure, a method for classifying a desired signal, an interfering signal to be cancelled (M-1), and an interfering signal not cancelled (NM) is proposed, which reduces the error rate of the desired signal when the number of transmitting terminals (N) is greater than the number of receiving antennas (M) of a base station.

[0016] More specifically, one aspect of the present disclosure is a receiving device that includes M receiving antennas and a control unit that executes a first process of acquiring a first signal from a first transmitting device among the N transmitting devices by receiving diversity processing from signals simultaneously received from N transmitting devices, and demodulating and decoding the first signal to acquire first data. In the first process, when the number N of transmitting devices is greater than the number M of receiving antennas, the control unit performs the following process. The control unit divides the signals from the N transmitting devices into a first signal from the first transmitting device by using a receiving diversity processing. All patterns of combinations classified into a first signal, a second signal that is cancelled by the receive diversity processing from M-1 transmitting side devices, and a third signal that is not cancelled by the receive diversity processing from NM transmitting side devices are acquired. The control unit acquires the power of the first signal and the power of the second signal for all patterns based on the weight used in the receive diversity processing of each pattern, and acquires the power of the third signal from the channel estimation value. The control unit acquires a power ratio of the power of the first signal to the total power of the second signal and the third signal, and executes receive diversity processing on the combination that has the largest power ratio after receive diversity processing, and determines it as the combination of signals to be demodulated.

[0017] The transmitting device is, for example, a wireless communication terminal. The receiving device is, for example, a base station. However, the transmitting device and the receiving device are not limited to a predetermined terminal. For example, the transmitting device may be a base station, and the receiving device may be a wireless communication terminal. The receiving diversity processing is, for example, a least mean square error (MMSE) method. However, the method of the receiving diversity processing is not limited to this. The first signal is, for example, a signal to be extracted, also called a desired signal. The second signal and the third signal are also called interference signals that affect the desired signal. Therefore, the power ratio of the power of the first signal to the total power of the second signal and the third signal is so-called a signal-to-interference ratio (SIR).

[0018] According to one aspect of the present disclosure, signals simultaneously received from multiple transmitting side devices can be classified into three types: a first signal, a second signal to be cancelled, and a third signal that is not cancelled. For this classification, for example, a combination pattern with the largest SIR obtained based on the channel estimation value of each signal and the weight of the diversity reception process is selected from all patterns. That is, based on the magnitude of the power after the diversity reception process, a combination that minimizes the influence of the interference signal on the desired signal can be determined, and the error rate of the desired signal can be reduced.

[0019] In one aspect of the present disclosure, in the first process, when the number N of transmitting side devices is greater than the number M of receiving antennas, the control unit may acquire the reception power of the signal from each transmitting side device, and acquire all combination patterns for signals from N' transmitting side devices, excluding a predetermined number of transmitting side devices from the N transmitting side devices, based on the reception power of the signal from each transmitting side device, thereby reducing the number of acquired patterns. By reducing the number of combination patterns of signal classification, the amount of calculation of the receiving side device is reduced, and the processing load of the receiving side device can be reduced.

[0020] The signals from the N' transmitting side devices may be identified by excluding a predetermined number of transmitting side devices with the lowest received power from the N transmitting side devices. Alternatively, the signals from the N' transmitting side devices may be identified by excluding transmitting side devices with the highest received power value obtained by multiplying the received power by a constant k (k>1).

[0021] In one aspect of the present disclosure, the receive diversity process is a minimum mean square error (MMSE) dummy. In this case, the control unit may obtain the MMSE weight for all patterns of the signal classification by using the power of the third signal of each pattern as a part of the interference power. By obtaining the MMSE weight by using the power of the third signal as a part of the interference power, it is possible to obtain a weight that further suppresses the influence of the third signal, which is an interference signal that is not canceled.

[0022] In one aspect of the present disclosure, the control unit may further execute the following second and third processes: In the second process, the control unit generates a signal arriving from the first transmitting device before receiving diversity processing is performed, based on the first signal or the first data. In the third process, a signal excluding the signal generated by the second process and arriving from the first transmitting device is extracted from the received signal. The control unit may further execute the following for the signal extracted by the third process: repeating the first process to the third process in sequence for one of the N-1 transmitting devices excluding the first transmitting device from the N transmitting devices as a new first transmitting device. In this way, when communication is simultaneously received from N transmitting devices, which is more than the number M of receiving antennas, signals from all transmitting devices can be reproduced.

[0023] In one aspect of the present disclosure, the control unit may allow communication with the receiving device from multiple transmitting devices that are not allocated wireless resources when a request for communication with the receiving device is generated, determine N transmitting devices among the multiple transmitting devices based on the received reference signal, and repeat the first to third processes when signals are simultaneously received from the N transmitting devices. An example of communication with the receiving device from multiple transmitting devices that are not allocated wireless resources when a request for communication with the receiving device is generated is CG with no upper limit on N. When communication is performed using CG with no upper limit on N, a situation in which communication is simultaneously received from N transmitting devices, which is more than the number M of receiving antennas, is likely to occur, but communication of stable quality can be maintained.

[0024] 2 is a diagram illustrating a hardware configuration of the base station 1 according to the first embodiment. The base station 1 includes a processor 11, a memory 12, an internal interface 13, a network interface 14 for communicating with other base stations, and a wireless processing device 15.

[0025] The processor 11 is also called a Central Processing Unit (CPU) or a Microprocessor Unit (MPU). The processor 11 is not limited to a single processor, and may have a multi-processor configuration. Also, a single physical CPU connected to a single socket may have a multi-core configuration. Furthermore, the processor 11 may be a Digital Signal The processor 11 may include various arithmetic devices of various circuit configurations, such as a digital signal processor (DSP) and a graphics processing unit (GPU). The processor 11 may also be integrated with an integrated circuit (IC), other digital circuits, or analog circuits. The integrated circuit may include an LSI, an application specific integrated circuit (ASIC), and a programmable logic device (PLD). The PLD may include, for example, a field-programmable gate array (FPGA). Therefore, the processor 11 may be, for example, what is called a microcontroller (MCU), a system-on-a-chip (SoC), a system LSI, a chip set, or the like.

[0026] The memory 12 stores a sequence of instructions (computer program) executed by the processor 11, or data processed by the processor 11, etc. The processor 11 and the memory 12 are sometimes called a baseband unit (BBU). The internal interface 13 is a circuit that connects various peripheral devices to the processor. The baseband unit can also be called a control unit.

[0027] The network interface 14 is a communication device that allows the base station 1 to access a network to which other base stations are connected. The network to which other base stations are connected is also called a backhaul. The backhaul is, for example, a wired network using optical communication.

[0028] The wireless processing device 15 includes a transceiver for transmitting wireless signals and a receiver for receiving wireless signals, and is connected to antennas ANT-B1, ..., ANT-BM. The wireless processing device 15 may have M systems of transceivers and receivers, the number of which is equal to the number of antennas. The wireless processing device 15 is called a remote radio head (RRH), and may be configured to be installed remotely by connecting to the baseband device via a wired network using optical communication. Alternatively, a plurality of remote radio heads may be connected to one baseband device. Note that a network that connects the baseband device and the remote radio heads is also called a fronthaul.

[0029] FIG. 3 is a block diagram illustrating the configuration of the terminal 2. In FIG. 3, the configuration of the terminal 2 is illustrated along with radio resource blocks and a channel matrix H of radio channels. The radio resource blocks refer to a portion separated by the frequency and time axes of carrier waves (subcarriers) assigned to the terminal 2. The channel matrix H is a matrix indicating the amount of fluctuation in amplitude and phase of the transmission path between each of the antennas ANT-1, ANT-2, etc. of the terminal 2 and the receiving antennas ANT-B1 to ANT-BM of the base station 1. By multiplying the transmission signal vectors of each of the antennas ANT-1, ANT-2, etc. of the transmitting terminal 2 by the channel matrix H, it is possible to obtain estimates of the reception signal vectors at the receiving antennas ANT-B1 to ANT-BM of the base station 1.

[0030] In Fig. 3, a plurality of terminals 2-1, ..., 2-N are illustrated. Furthermore, the detailed configuration of terminal 2 is illustrated by terminal 2-1. In Fig. 3, each terminal 2 has a pair of antennas ANT-1, ANT-2, ..., ANT-2N-1, ANT-2N. In the following description, when the antennas of each terminal 2 are collectively referred to, they will be simply referred to as antenna ANT. However, in this embodiment, the number of antennas of each terminal 2 is not limited to two.

[0031] The terminal 2 is also called User Equipment (UE). The terminal 2 has a processor, a memory, a radio processing device, an antenna ANT, etc. The processor, memory, and radio processing device of the terminal 2 are similar to the processor 11, memory 12, and radio processing device 15 described in FIG. 2. However, in the terminal 2, the processor, memory, and radio processing device are usually accommodated in one housing. The processor of the terminal 2 executes radio communication processing including each process of the encoding unit 206, the modulation unit 207, and the transmit diversity processing unit 208 by an instruction sequence (computer program) executablely deployed in the memory.

[0032] The encoding unit 206 performs error correction coding on the data transmitted from the terminal 2. The error correction code may be a soft decision code or a hard decision code, and there is no limit to the type of coding. The modulation unit 207 performs digital modulation on the error correction coded data. Examples of the digital modulation method include Quadrature Amplitude Modulation (QAM), Phase Shift Keying (PSK), and Frequency Shift Keying (FSK).

[0033] The transmit diversity processing unit 208 separates the digitally modulated signal into multiple signals and forms transmit diversity branches. The transmit diversity processing unit 208 radiates the signals separated into multiple branches from multiple antennas ANT through a radio processing device. In the example of FIG. 3, the transmit diversity processing unit 208 of each terminal 2 separates the transmission path by two antennas and forms transmit diversity branches. However, in this embodiment, the processing by the transmit diversity processing unit 208 is not limited to diversity by multiple antennas. For example, when the terminal 2 has a single antenna, the transmit diversity processing unit 208 may adopt polarization diversity, time diversity, frequency diversity, etc. In this embodiment, there is no limitation on the diversity processing, and various types of diversity are adopted.

[0034] 4 is a block diagram illustrating a configuration of the base station 1. The base station 1 includes a replica removal unit 101, a reception diversity and equalization processing unit 102, a demodulation unit 103, a decoding unit 104, and a replica generation unit 105. The replica generation unit 105 also includes an encoding unit 106, a modulation unit 107, a transmission diversity processing unit 108, and a channel matrix multiplication unit 109. The processor 11 illustrated in FIG. 2 executes an instruction sequence (computer program) executablely deployed in the memory 12, thereby implementing the replica removal unit 101, the reception diversity and equalization processing unit 102, the demodulation unit 103, the decoding unit 104, the replica generation unit 105, the encoding unit 106, the modulation unit 107, the transmission diversity processing unit 108, and the channel matrix multiplication unit 109. 07, a transmission diversity processing unit 108, and a channel matrix multiplication unit 109 perform the respective processes.

[0035] In FIG. 4, the channel matrix H is illustrated along with the configuration of the base station 1. The configuration of the channel matrix H is the same as that in FIG. 3. The channel matrix H is a matrix indicating the amount of fluctuation in amplitude and phase of the transmission path between each antenna ANT-1, ANT-2, etc. of the terminal 2 and antennas ANT-B1 to ANT-BM of the base station. The channel matrix H is determined by receiving a reference signal (Reference Signal, RS) transmitted from each antenna 2j-1, 2j (J=1, . . . , N) of each terminal 2-j at each antenna ANT-B1, . . . , ANT-BM. The same is true when the number of antennas of each terminal 2 is different from 2. In short, the amount of fluctuation corresponding to the transfer function of the transmission path is obtained by the reference signal transmitted and received between each antenna 2j-1, 2j of the transmitting side and each antenna ANT-Bi of the receiving side.

[0036] In the communication system of this embodiment, the RS is transmitted in the same resource block as that used in the CG. However, the RS may be transmitted in a resource block different from that used in the CG. In this embodiment, since the RS is transmitted in the same resource block as that used in the CG, the RS from each transmitting antenna ANT of each terminal 2 is orthogonal so that the RS does not interfere with each other among a plurality of terminals 2. Examples of methods for orthogonalizing the RS include a method of preventing overlap in time (TDMA), a method of shifting the frequency (FDMA), and orthogonalization by code (CDMA). In this embodiment, for example, CDMA is adopted. As the code used for the RS, when the base station 1 sets the CG, the base station 1 assigns a mutually different code to each terminal 2. The RS is added before and after the data (DS: data signal) transmitted from the terminal 2. Since the RS is orthogonal, the base station 1 can separate each signal of the RS and measure the channel matrix H even in an overloaded MIMO state. In this embodiment, the base station 1 is described as always having measured the latest channel matrix H.

[0037] In this embodiment, the receiving antennas ANT-B1 to ANT-BM receive radio signals in overlapping resource blocks that are simultaneously transmitted from N terminals 2, which is greater than the number M of receiving antennas (overloaded MIMO). In each of the antennas ANT-B1 to ANT-BM, signals from the multiple terminals 2 interfere with each other. Furthermore, in an overloaded MIMO state, no effect of transmit diversity is achieved. Therefore, in the base station 1 of this embodiment, the processor 11 repeatedly executes a serial canceller (Successive Interference Canceller, SIC) that sequentially performs MMSE equalization and removal of interference replicas of transmitted signals. .

[0038] First, SIC will be described. In SIC, the processor 11 first obtains received signals sx1 and sx2 from the transmission branches 2x-1 and 2x (antennas ANT-2x-1 and ANT-2x of the terminal 2-x) of a terminal 2-x (an integer of 1≦x≦N) of interest among signals received from each terminal 2 by MMSE equalization. How to select the terminal 2-x of interest is determined by the process described later.

[0039] Next, the processor 11 generates interference replicas r1(i) and rx2(i) (i=1, . . . , M) from the transmitting branches 2x-1 and 2x (transmitting antennas ANT-2x-1 and ANT-2x) corresponding to the received signals sx1 and sx2. (i) is an estimate of the received signal from the transmitting branches 2x-1, 2x (transmitting antennas ANT-2x-1, ANT-2x) before MMSE equalization received at the receiving antenna ANT-Bi.

[0040] Then, the processor 11 calculates the received signals at the receiving antennas ANT-B1 to ANT-BM. Then, let us define the interference replicas rx1(i) and rx2(i) (i = 1, , M) as As a result, the processor 11 can obtain a received signal that is not affected by the transmitted signals from the transmitting branches 1 and 2 (transmitting antennas ANT-2x-1, ANT-2x) as if it had been received from the receiving antennas ANT-B1 to ANT-BM. Thereafter, a new terminal 2-x to be focused on is determined from the terminals 2 that have not been removed (remaining), and the SIC process is repeatedly executed for the transmitting branches 2x-1, 2x of terminal 2-x (transmitting antennas ANT-2x-1, ANT-2x of terminal 2-x). In other words, if the terminal to be focused on in the j-th (j=1,...,N) loop of SIC is terminal 2-x(j), The same process is repeated for the received signal from which the transmission signals from terminal 2-x(1) through terminal 2-x(j-1) have been removed. With such control by processor 11, the received signals from each of antennas ANT-1, ANT-2, ..., ANT-2N-1, ANT-2N of each of terminals 2 are sequentially obtained for the wireless signals received by overloaded MIMO. This concludes the explanation of SIC.

[0041] Next, the configuration of the base station 1 will be described. The replica removing unit 101 subtracts an interference replica generated by a replica generating unit 105 described later from each received signal s(i) (i=1,...,M) received at the receiving antennas ANT-B1 to ANT-BM. After the first loop of SIC is executed, that is, at the start of the second loop of SIC, the replica removing unit 101 outputs a signal s2(i) obtained by subtracting the interference replicas r1-xj(i) and r2-xj(i) (i=1,...,M) from the received signal s(i) (i=1,...,M). The received signal sj(i) (i=1,...,M, j=1,...,N) output from replica removal unit 101 at the start of the j-th (j=1,...,N) SIC loop is a signal obtained by subtracting interference replicas r1-x1(1), r2-x1(1) through r1-x(j-1)(i), and r2-x(j-1)(i) (i=1,...,M) of terminals 2-x(1) through 2-x(j-1) from the received signal s(i)=s1(i). Note that interference replicas r1-x(j-1)(i) and r2-x(j-1)(i) are estimates of received signals from transmitting antennas ANT-2x(j-1)-1 and ANT-2x(j-1) of terminal 2-x(j-1).

[0042] The receive diversity and equalization processing unit 102 receives an input of a signal sj(i) obtained after an interference replica has been removed from a received signal s1(i) received at receiving antennas ANT-B1 to ANT-BM, which is output from the replica removal unit 101. That is, in the j-th loop of SIC, the signal sj(i) can be said to be a signal including a received signal from terminals 2 other than the transmitting antennas ANT-2x(1)-1, ANT-2x(1) to ANT-2x(j-1)-1, and ANT-2x(j-1) of terminals 2-x(1) to 2-x(j-1).

[0043] The receive diversity and equalization processor 102 determines a combination of a desired signal, an interference signal to be cancelled, and an interference signal that is not cancelled, of the signal of the terminal 2 included in the signal sj(i). The desired signal is a received signal from the terminal 2-x(j) of interest. Specifically, the receive diversity and equalization processor 102 acquires all patterns of combinations of a desired signal, an interference signal to be cancelled, and an interference signal that is not cancelled, of the signal of the terminal 2 included in the signal sj(i). Next, the receive diversity and equalization processor 102 acquires the signal-to-interference ratio (SIR) of the signal after processing by the receive diversity and equalization processor 102 using the MMSE method for all patterns. The receive diversity and equalization processor 102 selects the combination with the largest SIR and determines the terminal 2-x(j) of interest.

[0044] The receive diversity and equalization processor 102 uses the MMSE method to suppress interference other than that of the terminal 2-x(j) of interest (transmitting antennas ANT-2x(j)-1 and ANT-2x(j)). To this end, the receive diversity receiver and equalization processor 102 calculates the channel matrix H and From the Hermitian transpose matrix H^T of the above, the MMSE weight Wmmse vector is calculated by the following equation (1).

number

[0045] Then, the receive diversity and equalization processor 102 multiplies each received signal sj(i) (i=1, . . . , M, j=1, . . . , N) received at the receive antennas ANT-B1 to ANT-BM by the MMSE weight Wmmse vector. As a result, the receive diversity and equalization processor 102 performs equalization processing on the signals from the transmit antennas ANT-2j-1 and ANT-2j of each terminal 2-j, suppressing interference from other transmit antennas. In the j-th loop of each SIC, the receive diversity and equalization processor 102 acquires all patterns of combinations of desired signals, interference signals to be cancelled, and interference signals not cancelled for signals of terminals 2 other than terminals 2-x(1) to 2-X(j-1) that have already been cancelled in the 1st to j-1st loops. Next, the receive diversity and equalization processor 102 acquires SIRs from the calculation results of multiplying the channel matrix R by the MMSE weight Wmmse for all patterns. Then, the receive diversity and equalization processor 102 determines the terminal 2 corresponding to the desired signal in the combination with the highest SIR as the terminal 2-x(j) of interest in the j-th loop.The receive diversity and equalization processor 102 then performs receive processing using transmit diversity using multiple branches from the determined terminal 2-x(j).

[0046] The demodulation unit 103 generates a bit string from the received signal obtained by the receive diversity and equalization processing unit 102. The decoding unit 104 decodes the error correction code from the bit string obtained by the demodulation unit 103 to obtain data.

[0047] Based on the decoded signal from terminal 2, replica generation unit 105 generates an interference replica that is transmitted from antennas ANT-2j-1 and ANT-2j of terminal 2 and received by receiving antennas ANT-B1 to ANT-BM.

[0048] That is, the encoding unit 106 again performs error correction encoding on the data transmitted from the terminal 2 and decoded. The modulation unit 107 digitally modulates the error correction encoded data. The transmit diversity processing unit 108 executes the same transmit diversity processing as that of the terminal 2. The channel matrix multiplication unit 109 multiplies the transmit signals that have been subjected to transmit diversity processing and transmitted from each transmit branch of the terminal 2 by a channel matrix. This multiplication generates interference replicas that are received at the receive antennas ANT-B1 to ANT-BM. The data decoded by the decoding unit 104 can be said to be first data decoded from the first signal.

[0049] 5 is a flowchart illustrating the processing of the base station 1. In the OP1, the processor 11 permits the terminal 2 to use CG when connecting with the terminal 2, and designates resources to be used in CG and a different RS (Reference Signal) for each terminal. Here, the time of connection is, for example, when the terminal 2 and the base station establish a connection by a procedure called signaling, or when initial settings are made between the terminal 2 and the base station.

[0050] In OP2, the processor 11 performs settings for receiving a SIC loop in the base station 1. In the SIC loop, for example, the processor 11 checks the RS received from the terminal and identifies the terminal 2, and stores in the memory 12 the relationship between the RS assigned to the terminal 2 and the identification information of the terminal 2. The processor 11 also determines the number of SIC loops from the number of terminals from which the RS is received, and stores the number in the memory 12. The number of SIC loops is, for example, N-1 times, which is the number of terminals 2 that have received the RS.

[0051] In OP3, the processor 11 receives a signal from the terminal 2 by the CG. In addition, upon receiving the signal from the terminal 2, the processor 11 returns a response (ACK, NACK) from the base station 1 as appropriate. In OP4, when the base station 1 releases the connection with the terminal 2, the processor 11 cancels the CG setting and ends the processing shown in FIG. 5. The connection is released, for example, when the terminal 2 leaves the cell of the base station 1, when the terminal 2 stops processing, etc. According to the above processing, when the base station 1 permits the terminal 2 to use CG, the processor 11 performs settings for receiving the SIC loop within the base station 1.

[0052] 6 is a flowchart of reception processing by CG with the terminal 2 in the base station 1. The processing shown in FIG. 6 corresponds to the processing of OP3 in FIG. 5. The processing in FIG. 6 is repeatedly executed until the base station 1 releases the connection with the terminal 2. In OP101, the processor 11 acquires the reception signals of the overloaded MIMO received by the receiving antennas ANT-B1 to ANT-BM and the radio processing device 15.

[0053] In OP102, the processor 11 sets the initial value of a variable N to the number of terminals of the received signal. The variable N is a variable indicating the number of unseparated terminals. In OP103, the processor 11 determines a terminal 2-X of interest, and separates and acquires a signal (desired signal) transmitted from the terminal 2-x from the received signal using the MMSE method. Since the terminal 2-x transmits a signal using transmit diversity, the processor 11 acquires a modulated carrier signal transmitted from the terminal 2-x based on a plurality of transmit branches. The processor 11 executes the process of OP103 as the receive diversity and equalization processing unit 102.

[0054] In OP104, the processor 11 executes digital demodulation processing based on the signal acquired in the processing of OP103. That is, a bit string is extracted as a baseband signal from the modulated carrier signal. The processor 11 executes the processing of OP104 as the demodulation unit 103. In OP105, the processor 11 decodes data from the error correction coded signal, which is the baseband signal demodulated in the processing of OP104. The processor 11 executes the processing of OP105 as the decoding unit 104. By the processing of OP103 to OP105, the signal from the terminal 2 is separated, coded and demodulated from the received signal, and the data carried by the modulated carrier is demodulated and decoded. Therefore, the processing of OP103 to OP105 can be called the first processing.

[0055] In OP106, the processor 11 generates an interference replica from the transmission branch (transmission antenna) of the terminal 2-x. The processor 11 executes the process of OP106 as the replica generation unit 105. The process of OP106 can be called a second process.

[0056] In OP107, the processor 11 removes interference replicas from the signals received by the receiving antennas ANT-B1 to ANT-BM and the radio processing device 15. The processing in OP107 can be called a third processing. In OP108, the processor 11 determines whether or not an unseparated terminal 2 remains. If an unseparated terminal 2 remains (OP108: YES), the processing proceeds to OP109. If all terminals 2 have been processed and there are no unseparated terminals 2 remaining (OP108: NO), the processing shown in FIG. 6 ends, and the processing returns to OP4 in FIG. 5. Proceed to.

[0057] In OP109, the processor 11 subtracts 1 from the variable N to update the variable N. Thereafter, the process proceeds to OP103, where the next terminal 2-x of interest is determined, and the processes from OP103 to OP108 are performed for the terminal 2-x.

[0058] FIG. 7 is a flowchart of a desired signal separation process in the base station 1. The process shown in FIG. 7 is a process executed in OP103 of FIG. 6. In OP201, the processor 11 judges whether or not the variable N is larger than the number M of receiving antennas. The variable N is the number of unseparated terminals. If the variable N is larger than the number M of receiving antennas (OP201: YES), it is indicated that there is an overloaded MIMO state, and the process proceeds to OP202. If the variable N is equal to or smaller than the number M of receiving antennas (OP201: NO), it is indicated that there is no loaded MIMO state, and the process proceeds to OP206. In OP206, the processor 11 determines, for example, the terminal 2 with the highest power of the received signal from among the unseparated terminals 2 as the terminal 2-x of interest, and separates and acquires the signal (desired signal) transmitted from the terminal 2-x from the received signal by the MMSE method. Note that the MMSE weight Wmmse used in OP206 is (Equation 1) with Pi=0. Then, the process shown in FIG. 7 ends, and the process proceeds to OP104 in FIG.

[0059] In OP202, the processor 11 determines whether the variable N is greater than M'. M' is a fixed value greater than the number M of receiving antennas. If the variable N is greater than M' (OP202: YES), there are many combination patterns of the desired signal, the interfering signal to be cancelled, and the interfering signal that is not cancelled, so the process proceeds to OP203, where a process of reducing the combination patterns is performed. The details of the process of OP203 will be described later. If the variable N is equal to or less than M' (OP202: NO), there is no need to reduce the combination patterns of the desired signal, the interfering signal to be cancelled, and the interfering signal that is not cancelled, so the process proceeds to OP204.

[0060] In OP204, the processor 11 performs a combination determination process. That is, in OP204, the processor 11 calculates the SIR for all patterns of combinations of the desired signal, the interference signal to be canceled, and the interference signal not canceled of the unseparated received signal from the terminal 2, and determines the combination with the highest SIR. The details of the process in OP204 will be described later.

[0061] In OP205, for the combination determined in OP204, the processor 11 calculates the MMSE weight Wmmse, and obtains the desired signal from the calculation result of multiplying the MMSE weight Wmmse vector by each received signal sj(i) (i = 1, ···, M, j = 1, ···, N) received by the receiving antennas ANT-B1 to ANT-BM. Then, the process shown in FIG. 7 ends, and the process proceeds to OP104 in FIG. 6.

[0062] FIGS. 8 and 9 are diagrams for explaining the channel matrices H and R. FIGS. 8 and 9 show the definitions of the matrices used in the processes shown in the flowcharts of FIGS. 10 and 11 described later. In FIGS. 8 and 9, the number of receiving antennas is M, the number of terminals from which signals are received simultaneously is N, and the channel matrices in the case of overloaded MIMO where M < N are shown. Also, in FIGS. 8 and 9, the signal from terminal #1 is taken as the desired signal, the signals from M - 1 terminals among terminals #2 to #M are taken as the interference signals to be canceled, and the signals from N - M terminals among terminals #M + 1 to #N are taken as the interference signals not to be canceled for explanation.

[0063] FIG. 8 shows the channel matrix H. The vector hj is the channel vector of the signal from terminal #j. The size of the vector hj is M × 1. The matrix Hc‘ is the channel matrix of the interference signals to be canceled. The size of the matrix Hc is M × M - 1. The matrix Hc is the channel matrix of the desired signal and the interference signals to be canceled, the first column of which is the channel vector h1 of the desired signal, and the second to M - 1 columns are the channel matrix Hc’ of the interference signals to be canceled. The size of the matrix Hc is M × M. The matrix Hu is the channel matrix of the interference signals not to be canceled. The size of the matrix Hu is M × N - M. Note that the overall channel matrix H is an M × N matrix formed by arranging the channel matrix Hc of the desired signal and the interference signals to be canceled and the channel matrix Hu of the interference signals not to be canceled.

[0064] 9 shows a channel matrix R. The channel matrix R is a matrix obtained by multiplying the channel matrix H by the transmission amplitude of each terminal 2. The transmission amplitude of the signal from terminal #j is denoted as pj. The transmission power is obtained by squaring the transmission amplitude pj.

[0065] Vector rj is the channel vector of terminal #j. The components of the channel vector rj of terminal #j are obtained by multiplying the components of the channel vector hj of terminal #j by the transmission amplitude pj of terminal #j.

[0066] Matrix Rc is the channel matrix of the desired signal and the interference signal to be cancelled. Matrix Rc is an arrangement of channel vectors h1 to hM of terminal #1 to terminal #M. Matrix Ru is the channel matrix of the interference signal that is not cancelled. Matrix Ru is an arrangement of channel vectors hM+1 to hN of terminal #M+1 to terminal #N. Note that the overall channel matrix R is an M×N matrix that arranges the channel matrix Rc of the desired signal and the interference signal to be cancelled, and the channel matrix Ru of the interference signal that is not cancelled. The sizes of vector rj, matrix Rc, and Ru are the same as the sizes of vector hj, matrix Hc, and matrix Hu, respectively.

[0067] Fig. 10 is an example of a flowchart of a process of reducing combination patterns in the base station 1. The process shown in Fig. 10 corresponds to the process in OP203 in Fig. 7. The process of reducing combination patterns shown in Fig. 10 is executed when the number of terminals from which signals are received simultaneously is greater than a threshold value M', that is, when the number of combination patterns becomes large.

[0068] In OP301, the processor 11 calculates the received power P_H(n) from a terminal n (n=1, 2, . . . , N). The received power P_H(n) from the terminal n is obtained by the following (Equation 2). R(m, n) indicates the element of the mth row and the nth column of the matrix R.

number

[0069] In OP302, the processor 11 rearranges in descending order the received power of the signal of each terminal 2. The α1 of P_H(α1) in Fig. 10 indicates the order after rearrangement.

[0070] In OP303, the processor 11 specifies a terminal to be excluded. There are two methods for specifying a signal to be excluded in OP303: Method 1 and Method 2. Which method is used for processing may be set, for example, by an administrator of the base station 1. OP303A is processing for specifying a signal to be excluded by Method 1. OP303B is processing for specifying a signal to be excluded by Method 2.

[0071] In the OP303A, that is, in the method 1, the processor 11 specifies, among the signals of each terminal 2, the signals with the lowest X reception powers sorted in descending order as signals to be excluded. In this case, the processor 11 sets the number N' of signals to be considered for combination patterns to NX.

[0072] In OP303B, i.e., in method 2, the processor 11 specifies, as signals to be excluded, signals for which the value obtained by multiplying the received power P_H(αn) of the signal of each terminal 2 by a constant k (k>1) is smaller than the largest received power P_H(α1). In this case, the processor 11 sets the number N' of signals to be considered for combination patterns to a value obtained by subtracting the number of signals to be excluded from N. Since the number of signals specified as signals to be excluded is indefinite, the number N' of signals to be specified is also indefinite.

[0073] When the process of OP303A or OP303B is completed, the process shown in Fig. 10 is completed, and the process proceeds to OP204 in Fig. 7. Note that the received power of the signal to be excluded in OP303A and OP303B is sufficiently smaller than the maximum received power P_H(α1), and even if it is excluded from the consideration of the next process, which is the combination selection process, the influence on the SIR value, etc. is so small that it can be ignored.

[0074] Fig. 11 is an example of a flowchart of a combination selection process in the base station 1. The process shown in Fig. 11 corresponds to the process in OP204 in Fig. 7. The process in Fig. 11 targets the N' signals determined in OP203 (Fig. 10) in Fig. 7.

[0075] In OP401, the processor 11 creates all combination patterns of a desired signal (1), an interference signal (M-1) to be cancelled, and an interference signal (M-N') that is not cancelled, for N' signals. The number of patterns L for one desired signal is the number of combinations of selecting M-1 signals from N'-1 signals.

[0076] The processes from OP402 to OP405 are processes for obtaining the SIR of each combination, and are executed for all patterns (N'*L). In OP402, the processor 11 calculates the interference power Pi of the N'-M non-cancelled interference signals using the following (Equation 3). Pi is the interference power when the interference power of the N'-M non-cancelled interference signals is distributed per receiving antenna.

number

[0077] In OP403, the processor 11 calculates the MMSE weight Wmmse according to (Equation 1). The MMSE weight Wmmse is an M×1 vector. In OP404, the processor 11 obtains the power Ps of the desired signal and the power Pb of other interference signals. The power Pb of the interference signals is the sum of the interference powers of the interference signals to be cancelled (M−1 signals) and the interference signals not to be cancelled (N′−M signals).

[0078] In order to obtain the power Ps of the desired signal and the power Pb of the other interference signals, the processor 11 first multiplies the transposed vector (1×M) of the MMSE weight Wmmse by the entire channel matrix R (M×N′) to obtain a vector G. The vector G is a 1×N′ vector. The components in the first column of the vector G are the desired signal components Gs, and the components in the second to N′ columns of the matrix G are the interference signal components Gu(p) (p=2, . . . , N′). The power is obtained by squaring the absolute value of each component. That is, the power Ps of the desired signal is obtained by squaring the absolute value of the desired signal component Gs. The power Pb of the interference signal is obtained by summing up the squares of the absolute values ​​of the interference signal components Gu(p).

[0079] In OP405, the processor 11 calculates the SIR. The SIR is obtained by dividing the power Ps of the desired signal by the power Pb of the interference signal. When the processes from OP402 to OP405 are performed for all patterns and the SIRs of all patterns are obtained, the process proceeds to OP406.

[0080] In OP406, the processor 11 selects the combination that maximizes the SIR. After that, the process shown in Fig. 10 ends, and the process proceeds to OP205 in Fig. 7. Note that in the process in Fig. 7, if the determination in OP202 is negative, the process in OP203 is not performed, and therefore, in the process in OP204 (Fig. 11), the process is performed assuming that N'=N.

[0081] 12 to 14 show examples of simulation results by the processing of this embodiment. Fig. 12 shows examples of simulation conditions. This simulation is performed when the number of simultaneous transmitting terminals is 3 to 6 (each terminal has two transmitting antennas) and when the number of simultaneous transmitting terminals is 5 to 10 (each terminal has four transmitting antennas).

[0082] The transmission data size is 80 bits. The error correction code is turbo code (coding rate 1 / 3). The modulation method is single-carrier QPSK. The transmission path is assumed to be one-path Rayleigh fading with a maximum Doppler frequency of 0 Hz. The signal-to-noise power ratio of the transmission path is assumed to be 30 dB.

[0083] Figure 13 illustrates the difference in bit error rate depending on whether or not the combination pattern reduction process (Figure 10) and the combination selection process (Figure 11) are performed when the number of receiving antennas is two in a simulation. Each graph in Figure 13 is an example without transmit diversity. In Figure 13, the horizontal axis is the number of terminals transmitting simultaneously, and the vertical axis is the bit error rate.

[0084] In Fig. 13, the graph with circle markers (●) shows the simulation result when the combination pattern reduction process (Fig. 10) and the combination selection process (Fig. 11) are not executed. In the case of the graph with circle markers, the desired signal, the interference signal to be cancelled, and the interference signal not to be cancelled are determined in descending order of the received power of the signal. The graph with triangular markers (▲) shows the simulation result when the combination pattern reduction process (Fig. 10) and the combination selection process (Fig. 11) are executed. In the graph with triangular markers (▲), method 1 is adopted as the method for identifying the signal to be excluded, and the bottom 1 signal is excluded. The graph with black square markers shows the simulation result when the combination pattern reduction process (Fig. 10) and the combination selection process (Fig. 11) are executed. In the graph with black square markers, method 2 is adopted as the method for identifying the signal to be excluded, and the constant k is set to 4.

[0085] Comparing the graphs of the simulation results shown in Figure 13, it can be seen that regardless of whether the number of terminals transmitting simultaneously is 3 to 6, the bit error rate is lower when the combination pattern reduction process (Figure 10) and the combination selection process (Figure 11) are performed (graphs with triangular markers and graphs with square markers) than when they are not performed (graphs with circle markers).

[0086] Fig. 14 illustrates the difference in bit error rate depending on whether or not the combination pattern reduction process (Fig. 10) and the combination selection process (Fig. 11) are performed in a simulation when the number of receiving antennas is four. In Fig. 14, the simulation and graph settings are the same as those in Fig. 13.

[0087] Comparing the graphs of the simulation results shown in Fig. 14, the number of terminals transmitting simultaneously It is shown that, regardless of whether the number is between 5 and 10, the bit error rate is lower when the combination pattern reduction process (Figure 10) and the combination selection process (Figure 11) are performed (graphs with triangular markers and graphs with square markers) than when they are not performed (graphs with circle markers).

[0088] From the simulation results shown in Figures 13 and 14, in overloaded MIMO, the error rate can be reduced by calculating the SIR for all combination patterns in which signals from N terminals 2 are classified into desired signals, interference signals to be cancelled, and interference signals that are not cancelled, and separating the desired signal using the combination with the highest SIR.

[0089] <Effects of the First Embodiment> According to the first embodiment, in an overloaded MIMO situation where the number of terminals simultaneously transmitting is greater than the number of receiving antennas, it is possible to determine a combination of a desired signal, an interference signal to be canceled, and an interference signal that is not canceled that maximizes the SIR. This makes it possible to reduce the error rate of the desired signal, and to suppress deterioration of communication quality even in an overloaded MIMO situation.

[0090] In addition, the SIR of each pattern used in determining the combination of the desired signal, the interference signal to be cancelled, and the interference signal not to be cancelled is calculated based on the calculation result of multiplying the MMSE weight by the channel matrix of the received signal. This allows the combination to be determined based on the actually obtained output, thereby further reducing the error rate.

[0091] Furthermore, in the first embodiment, signals with sufficiently small received power are excluded from the determination of combinations of desired signals, interfering signals to be canceled, and interfering signals that are not canceled, so that the number of combination patterns can be reduced, and the processing load for calculating the SIR of each pattern can be lightened.

[0092] According to the communication system of this embodiment, in overloaded MIMO, the packet error rate can be suppressed and efficient wireless communication can be realized by separating signals from individual terminals 2 by SIC. Also, according to the communication system of this embodiment, in overloaded MIMO, the packet error rate can be further suppressed by using transmit diversity together with SIC.

[0093] Therefore, in the IoT, when CG is implemented and a large number of terminals 2 communicate with the base station 1 in excess of the number of receiving antennas of the base station, the base station 1 implements SIC to suppress the packet error rate and realize efficient and reliable wireless communication. Furthermore, the base station 1 uses transmit diversity in addition to SIC to realize even more efficient and reliable wireless communication. That is, in this embodiment, when the base station 1 allocates CG resources to the terminal 2 and allows CG, it executes SIC processing, which is expected to improve the reliability of communication in CG and to improve the efficiency of communication by suppressing the packet error rate.

[0094] Furthermore, in this embodiment, an interference replica is generated based on data after error correction, so that even in an overloaded MIMO state where the signal-to-interference-plus-noise ratio (SINR) is low, base station 1 can generate and feed back an interference replica with high accuracy.

[0095] <Other embodiments> The above-described embodiment is merely an example, and the present disclosure can be modified and implemented as appropriate without departing from the spirit and scope of the present disclosure.

[0096] In the first embodiment, it is assumed that the terminal 2 is the transmitting side and the base station 1 is the receiving side, but the base station 1 may be the transmitting side and the terminal 2 may be the receiving side. When the base station 1 is the transmitting side and the terminal 2 is the receiving side, the terminal 2 has a similar configuration to the base station 1 described in the first embodiment and performs similar processing. Therefore, the base station 1 is an example of both a "receiving side device" and an example of a "transmitting side device". The terminal 2 is an example of both a "transmitting side device" and an example of a "receiving side device".

[0097] The processes and means described in this disclosure can be freely combined and implemented as long as no technical contradiction occurs.

[0098] Furthermore, a process described as being performed by one device may be shared and executed by multiple devices. Alternatively, a process described as being performed by different devices may be executed by one device. In a computer system, the hardware configuration (server configuration) by which each function is realized can be flexibly changed.

[0099] The present disclosure can also be realized by supplying a computer program implementing the functions described in the above embodiments to a computer, and having one or more processors of the computer read and execute the program. Such a computer program may be provided to the computer by a non-transitory computer-readable storage medium connectable to the system bus of the computer, or may be provided to the computer via a network. Non-transitory computer-readable storage media include, for example, any type of disk, such as a magnetic disk (floppy disk, hard disk drive (HDD), etc.), an optical disk (CD-ROM, DVD disk, Blu-ray disk, etc.), a read-only memory (ROM), a random access memory (RAM), an EPROM, an EEPROM, a magnetic card, a flash memory, an optical card, and any type of medium suitable for storing electronic instructions. [Explanation of symbols]

[0100] 1 base station 2. Terminal 11 Processors 12. Memory 13 Internal Interface 14 Network Interface 15 Radio Processing Unit 101 Replica Removal Department 102 Reception diversity and equalization processing section 103 Demodulation section 104 Decoding section 105 Replica Generation Unit 106 Encoding section 107 Modulation section 108 Transmission diversity processing unit 109 Channel Processing Unit ANT Antenna

Claims

1. M receiving antennas; a control unit that executes a first process of acquiring a first signal from a first transmitting device that is one of the N transmitting devices through a predetermined receiving process from signals simultaneously received from the N transmitting devices, and demodulating and decoding the first signal to acquire first data; A receiving device comprising: the predetermined receiving process is a process of canceling signals from all but one of the plurality of transmitting side devices by multiplying signals simultaneously received from the plurality of transmitting side devices by a first weight when the number of the plurality of transmitting side devices is equal to or less than the number of receiving antennas, and acquiring a signal from the one transmitting side device; The control unit, in the first processing, When the number N of the transmitting side devices is greater than the number M of the receiving antennas, acquiring all patterns of combinations of signals from the N transmitting side devices classified into the first signal from the first transmitting side device, the second signal from M-1 transmitting side devices that is canceled by the predetermined receiving process, and the third signal from N-M transmitting side devices that is not canceled by the predetermined receiving process; For all of the patterns, a power of the first signal and a power of the second signal are obtained based on the first weight used in the predetermined reception processing of each pattern, and a power of the third signal is obtained from a channel estimation value; obtaining a power ratio of a power of the first signal to a total power of the second signal and the third signal; performing the predetermined reception processing and determining a combination that maximizes the power ratio after the predetermined reception processing as a combination of signals to be demodulated; The receiving device.

2. In the first process, the control unit determines whether the number N of the transmitting side devices is greater than the number of the receiving antennas. When the number of is greater than M, obtaining the received power of the signal from each transmitting device; acquiring all patterns of the combinations of signals from N' transmitting side devices, which is obtained by excluding a predetermined number of transmitting side devices from the N transmitting side devices, based on the reception power of the signals from each of the transmitting side devices, thereby reducing the number of acquired patterns.

2. The receiving device according to claim 1.

3. The control unit is excluding a predetermined number of transmitting side devices having the lowest reception power from the N transmitting side devices, and identifying signals transmitted from the N' transmitting side devices; The receiving device according to claim 2.

4. The control unit is From the N transmitting side devices, a transmitting side device having a value obtained by multiplying the received power by a constant k (k>1) that is smaller than the largest received power is excluded, and signals from the N' transmitting side devices are identified. The receiving device according to claim 2.

5. The predetermined receiving process is a minimum mean square error (MMSE) diversity, The control unit obtains the first weight of MMSE for all the patterns by using the power of the third signal of each pattern as a part of interference power. A receiving device according to any one of claims 1 to 4.

6. The control unit is a second process for generating a signal arriving from the first transmitting device before the predetermined receiving process is performed based on the first signal or the first data; a third process of extracting a signal from the received signal excluding the generated signal arriving from the first transmitting device; Repeating the first to third processes for the extracted signal in sequence, with one of the N-1 transmitting devices (excluding the first transmitting device) as a new first transmitting device; Further execute A receiving device according to any one of claims 1 to 5.

7. the control unit allows a plurality of transmitting side devices to communicate with the receiving side device without being assigned wireless resources when a request for communication with the receiving side device is generated, determines the N transmitting side devices among the plurality of transmitting side devices based on a received reference signal, and repeats the first process to the third process when signals are simultaneously received from the N transmitting side devices. The receiving device according to claim 6.

8. A receiving device having M receiving antennas, 1. A wireless communication method comprising: executing a first process of acquiring a first signal from a first transmitting device, which is one of N transmitting devices, by a predetermined receiving process from signals simultaneously received from the N transmitting devices, and acquiring first data by demodulating and decoding the first signal, the predetermined receiving process is a process of canceling signals from all but one of the plurality of transmitting side devices by multiplying signals simultaneously received from the plurality of transmitting side devices by a first weight when the number of the plurality of transmitting side devices is equal to or less than the number of receiving antennas, and acquiring a signal from the one transmitting side device; In the first process, When the number N of the transmitting side devices is greater than the number M of the receiving antennas, acquiring all patterns of combinations of signals from the N transmitting side devices classified into the first signal from the first transmitting side device, the second signal from M-1 transmitting side devices that is canceled by the predetermined receiving process, and the third signal from N-M transmitting side devices that is not canceled by the predetermined receiving process; For all of the patterns, a power of the first signal and a power of the second signal are obtained based on the first weight used in the predetermined reception processing of each pattern, and a power of the third signal is obtained from a channel estimation value; obtaining a power ratio of a power of the first signal to a total power of the second signal and the third signal; performing the predetermined reception processing and determining a combination that maximizes the power ratio after the predetermined reception processing as a combination of signals to be demodulated; A wireless communication method.

9. In the first process, when the number N of the transmitting side devices is greater than the number M of the receiving antennas, obtaining the received power of the signal from each transmitting device; acquiring all patterns of the combinations of signals from N' transmitting side devices, which is obtained by excluding a predetermined number of transmitting side devices from the N transmitting side devices, based on the reception power of the signals from each of the transmitting side devices, thereby reducing the number of acquired patterns. The wireless communication method according to claim 8.

10. excluding a predetermined number of transmitting side devices having the lowest reception power from the N transmitting side devices, and identifying signals from the N' transmitting side devices; The wireless communication method according to claim 9.

11. From the N transmitting side devices, a transmitting side device having a value obtained by multiplying the received power by a constant k (k>1) that is smaller than the largest received power is excluded, and signals from the N' transmitting side devices are identified. The wireless communication method according to claim 9.

12. The predetermined receiving process is a minimum mean square error (MMSE) diversity, obtaining the first weight of MMSE for all the patterns by using the power of the third signal of each pattern as a part of interference power; A wireless communication method according to any one of claims 8 to 11.

13. a second process for generating a signal arriving from the first transmitting device before the predetermined receiving process is performed based on the first signal or the first data; a third process of extracting a signal from the received signal excluding the generated signal arriving from the first transmitting device; Repeating the first to third processes for the extracted signal in sequence, with one of the N-1 transmitting devices (excluding the first transmitting device) as a new first transmitting device; Further execute A wireless communication method according to any one of claims 8 to 12.

14. allowing the N transmitting devices to communicate with the receiving device without being assigned wireless resources when a request for communication with the receiving device is generated, determining the N transmitting devices among the plurality of transmitting devices based on a received reference signal, and repeating the first to third processes when signals are simultaneously received from the N transmitting devices; The wireless communication method according to claim 13.

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