Base station, system, and information processing method

Abstract

To suppress deterioration in radio communication quality.SOLUTION: A base station performs first processing for acquiring a first signal from a first terminal from among signals simultaneously received from N terminals, and demodulating and decoding the first signal to obtain first data, second processing for generating a second signal which is a replica of a signal coming from the first terminal, on the basis of the first data, and third processing of extracting a signal excluding the second signal from among the signals simultaneously received from the N terminals, and the first processing to the third processing are repetitively successively performed on the extracted signal by newly using one of the (N-1) terminals as the first terminal for the extracted signal. The base station shares the first data acquired by the first processing with other base stations through a backbone line. When the number of the N terminals is larger than the number of M receiving antennas, the second processing and the third processing are executed by using the first data received from another base station for a terminal in which the pieces of first data are not acquired by the first processing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] TECHNICAL FIELD This disclosure relates to wireless communications. [Background technology]

[0002] For example, in the case of IoT (Internet of Things), 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. Input Multiple Output (MIMO) is used. 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 at the same time is called multi-user MIMO. With the development of such wireless communication technology, the number of terminals accessing public networks is predicted to increase in the future, and there are concerns about the congestion of uplinks.

[0003] The terminal transmits radio waves using Power-Domain Uplink Non-Orthogonal Multiple Access (PD-UL-NOMA). PD-UL-NOMA is In the uplink, this technology realizes multiplexing not only in the domains divided by time and frequency, but also in the power domain at the same time and frequency. This makes it possible to simultaneously connect more transmitting antennas than receiving antennas, i.e., more terminals than receiving antennas. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Shogo Kishiyama, Akira Sume, Yukihiko Okumura, "Latest Wireless Access Technologies and Field Trial Results of 5G System - Technologies for Achieving Ultra-High-Speed Wireless Data Transmission, Support for High-Speed Mobility, and Improved Frequency Utilization Efficiency -", NTT DoCoMo Technical Journal, April 2017, Vol. 25, No.1, p.16-29 [Non-Patent Document 2] Akira Sume, Tatsuki Okuyama, Yuki Inoue, Shogo Kishiyama, "5G Multi-Antenna Technology", NTT DoCoMo Technical Journal, January 2016, Vol. 23, No.4, p.30-39. [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, for example, in communication using PD-UL-NOMA, when the number of terminals transmitting to the base station at the same timing increases and the number of connected terminals becomes larger than the number of receiving antennas, the communication quality is likely to deteriorate.

[0006] An embodiment of the present disclosure aims to provide a base station, a system, and a method capable of suppressing a deterioration in the quality of wireless communication. [Means for Solving the Problems]

[0007] One aspect of the present disclosure is a communication unit connected to a backbone line to which one or more base stations are connected, M (1 < M) receiving antennas, a first process of obtaining a first signal from a first terminal, which is one of the N terminals, from signals received simultaneously from N (1 < N) terminals by a predetermined process, demodulating and decoding the first signal to obtain first data, a second process of generating a second signal, which is a replica of the signal arriving from the first terminal before the predetermined process is performed, based on the first data, a third process of extracting a signal obtained by excluding the generated second signal from the received signals, ​For the extracted signal, one of the N - 1 terminals excluding the first terminal from the N terminals is sequentially set as the new first terminal, and the first process to the third process are repeated. A base station including a control unit that executes The control unit Shares the first data obtained by the first process with one or more other base stations through the backbone line. When there are more terminals among the N terminals than the M receiving antennas, for the terminals from which the first data was not obtained by the first process, the second process and the third process are executed using the first data received from any of the one or more other base stations. Is a base station.

[0008] One of the other aspects of the present disclosure is A communication unit connected to a backbone line to which one or more base stations are connected, M (1 < M) receiving antennas, From the signals received simultaneously from N (1 < N) terminals, by a predetermined process, a first signal from a first terminal which is one of the N terminals is acquired, and the first signal is demodulated and decoded to acquire first data (first process); Based on the first data, a second process of generating a second signal which is a replica of the signal coming from the first terminal before the predetermined process is performed; A third process of extracting a signal obtained by excluding the generated second signal from the received signals; For the extracted signal, one of the N - 1 terminals excluding the first terminal from the N terminals is sequentially set as the new first terminal, and the first process to the third process are repeated. A base station including a control unit that executes The control unit Shares the first data obtained by the first process with one or more other base stations through the backbone line. When the number of the N terminals is greater than the number of the M receiving antennas, for a terminal from which the first data is not acquired by the first process, the second process and the third process are executed using the first data received from any one of the one or more other base stations. A base station, A server that is connected to the base station and processes the first data acquired by the first process performed by the base station, including a plurality of combinations of is a system.

[0009] One of other aspects of the present disclosure is A communication unit connected to a backbone line to which one or more base stations are connected, M (1 < M) receiving antennas, A base station including From signals received simultaneously from N (1 < N) terminals, by a predetermined process, a first signal from a first terminal that is one of the N terminals is acquired, and the first signal is demodulated and decoded to acquire first data; a first process; Based on the first data, a second process of generating a second signal that is a replica of a signal coming from the first terminal before the predetermined process is performed; A third process of extracting a signal obtained by excluding the generated second signal from the received signals; Repeating the first process to the third process sequentially with one of the N - 1 terminals excluding the first terminal from the N terminals as a new first terminal for the extracted signal; executing Sharing the first data acquired by the first process with one or more other base stations through the backbone line, When the number of the N terminals is greater than the number of the M receiving antennas, for a terminal from which the first data is not acquired by the first process, the second process and the third process are executed using the first data received from any one of the one or more other base stations. is a method.

[0010] According to one aspect of the present disclosure, it is possible to suppress a deterioration in the quality of wireless communication.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a wireless communication system according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of SIC processing. [Diagram 3] FIG. 3 is a diagram showing an example of the hardware configuration of a base station and a Multi-access Edge Computing (MEC) server according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the functional configuration of a base station and a control station. [Diagram 5] FIG. 5 is an example of a terminal management table of a control station. [Figure 6] FIG. 6 is an example of a flowchart of MIMO reception processing of a base station. [Figure 7] FIG. 7 is an example of a flowchart of terminal management processing of a control station.

Embodiments for Carrying Out the Invention

[0012] One aspect of the present disclosure is a base station including a communication unit connected to a backbone line to which one or more base stations are connected, M (1 < M) reception antennas, and a control unit. When the control unit receives signals from N (1 < N) terminals simultaneously, it repeatedly executes the following first process, second process, and third process.

[0013] The first process is a process of acquiring a first signal from a first terminal, which is one of the N terminals, from signals simultaneously received from N terminals by a predetermined process, and demodulating and decoding the first signal to acquire first data. The second process is a process of generating a second signal, which is a replica of a signal arriving from the first terminal before the predetermined process is performed, based on the first data acquired by the first process. The third process is a process of extracting a signal excluding the second signal generated by the second process from the signals simultaneously received from N terminals. The control unit repeats the first process to the third process in sequence for the signal extracted by the third process, with one of the N-1 terminals, excluding the first terminal, being newly set as the first terminal. The first process, the second process, and the third process are processes called successive interference cancellation (SIC).

[0014] The predetermined processing is processing for extracting a signal arriving from a first terminal from signals simultaneously received from N terminals. The processing for extracting a signal arriving from a first terminal from signals simultaneously received from N terminals is, for example, reception diversity processing. The reception diversity processing is, for example, processing of the Minimum Mean Square Error (MMSE) method. The reception diversity processing is carried out by using a weight W defined using a channel matrix H. In this way, the signal arriving from the first terminal is extracted from the signals simultaneously received from N terminals, and the signals from the other terminals are treated as interference signals and canceled. Note that the process of separating the signal arriving from the first terminal from the signals simultaneously received from N terminals is not limited to a specific method.

[0015] In this disclosure, the term "signal" refers to a signal that is not binarized with 0 and 1, including an analog signal and a digital signal. In this disclosure, the term "data" refers to a signal that is binarized with 0 and 1.

[0016] In one aspect of the present disclosure, the control unit of the base station shares the first data acquired by the first process with one or more other base stations through a backbone line. Also, when N terminals are greater than M receiving antennas, the control unit of the base station executes the second process and the third process for a terminal from which the first data was not acquired by the first process, using the first data of the terminal received from one or more of the other base stations.

[0017] When there are N terminals more than M receiving antennas, the signals from NM terminals cannot be cancelled even by performing a predetermined process and remain as interference signals, so that when demodulating the signal arriving from the first terminal, an error occurs due to the influence of the interference signal, and the first data may not be acquired. In one aspect of the present disclosure, the first data of each terminal acquired by each base station is shared between base stations, so that even if the first data from the first terminal cannot be acquired, a second signal that is a replica of the signal arriving from the first terminal can be created using the first data corresponding to the first terminal received from another base station, and the second signal can be removed from the signal extracted by the previous third process. As a result, even if the first data from one terminal cannot be acquired at the base station, the second signal can be created using the first data received from another base station and removed, so that the number of signals that become interference signals for signals from the remaining terminals is reduced. As a result, the first process to the third process for the remaining terminals can be continued, and the number of terminals that can separate the signal arriving from one terminal from the signals simultaneously received from N terminals is likely to increase, improving the performance of removing interference between terminals.

[0018] Another aspect of the present disclosure is a system including a plurality of combinations of the above-mentioned base station and a server that performs processing according to the first data acquired by the first processing by the base station and responds to the first terminal. The server is, for example, an MEC server. According to another aspect of the present disclosure, the first data acquired by demodulation and decode by the base station is processed by a server connected to the base station, and a response as the processing result is returned to the first terminal, thereby realizing low latency.

[0019] A system according to another aspect of the present disclosure may further include an information processing device including a communication unit connected to a backbone line and a control unit that executes receiving first data transmitted from a base station and transmitting the received first data to another base station. This allows the first data acquired at each base station to be aggregated in the information processing device. In addition, since the first data is binarized data of 0 and 1, it is small in size and the bandwidth used in the backbone line can be reduced. In addition, compared to a system in which signals received at each base station are aggregated in the information processing device and the information processing device performs separation processing of signals from each terminal and demodulation and decoding processing, the load on the information processing device can be reduced.

[0020] In another aspect of the present disclosure, the control unit of the information processing device may identify a base station receiving a signal from a first terminal corresponding to the first data received from one base station, and transmit the received first data to the identified base station. Since the first data is not transmitted to a base station that has not received the first data from the other base station, the use of the bandwidth of the backbone line can be reduced.

[0021] In another aspect of the present disclosure, the control unit of the information processing device may transmit a stop of the first to third processes to the base stations when the first data is acquired for all of the multiple terminals that have transmitted signals and are present in a cell including the multiple base stations. This allows each base station to stop the first to third processes for all of the N terminals that have received the data when it receives a stop instruction from the information processing device, even if the base station is in the middle of performing the first to third processes. This reduces the processing load at the base station.

[0022] Another aspect of the present disclosure may be specified as a method in which the above-mentioned base station performs the above-mentioned processing. Also, another aspect of the present disclosure may be specified as a program for causing a computer to execute the above-mentioned processing of the base station, and a non-transitory computer-readable recording medium storing the program.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The configurations of the following embodiments are merely examples, and the present disclosure is not limited to the configurations of the embodiments.

[0024] First Embodiment 1 is a diagram illustrating a configuration of a wireless communication system 100 according to the first embodiment. The wireless communication system 100 includes a plurality of base stations 1, a plurality of MEC (Multi-access Edge Computing or Mobile Edge Computing) servers 2 connected one-to-one to each of the base stations 1, a control station 3 that manages the base stations 1, and a plurality of terminals 4 that communicate wirelessly with the base stations 1. The plurality of base stations 1 are base stations that exist in one cell managed by the control station 3. The base stations 1 and the control station 3 are connected by a backbone line 50.

[0025] In the first embodiment, each base station 1 has M receiving antennas and implements multi-user MIMO. Furthermore, the terminal 4 transmits radio waves using PD-UL-NOMA. Therefore, in the first embodiment, the base station 1 receives signals from a plurality of terminals 4 simultaneously. Since the signals received by the base station 1 by MIMO are superimposed with the signals from a plurality of terminals 4, the base station 1 separates the signals from each terminal 4 from the received signal. One method of separating the signals from each terminal 4 from the superimposed signal is successive interference cancellation (SIC).

[0026] Fig. 2 is a diagram showing an example of SIC processing. Fig. 2 shows an example of a case where a signal from each terminal AE is separated from a superimposed signal including signals from five terminals AE. In SIC processing, three processes are repeatedly executed: (1) data acquisition processing of a desired signal, (2) replica signal generation processing, and (3) replica signal removal processing.

[0027] (1) In the data acquisition process for a desired signal, first, a signal from one target terminal is extracted by performing receive diversity processing on the received signal (superimposed signal) received by the antenna. Hereinafter, the signal from one target terminal is referred to as the desired signal. Extracting the desired signal from the superimposed signal is also referred to as separating the desired signal. A terminal from which the desired signal is not extracted from the superimposed signal is referred to as an unseparated terminal.

[0028] In the diversity reception process, a predetermined calculation is performed using a predetermined weight W, and signals from terminals other than the target terminal are cancelled as interference signals, and the desired signal from the target terminal can be obtained as a result of the calculation. The desired signal is demodulated and decoded to obtain the data transmitted from the target terminal. By demodulating and decoding the desired signal, The obtained data is corrected by error correction codes such as CRC (Cyclic Redundancy Check). The binarized data of 0 and 1 is hereinafter referred to as a hard decision value.

[0029] In the first embodiment, the term "signal" refers to a signal that is not binarized with 0 and 1. The term "data" refers to a signal that is binarized with 0 and 1. For example, a baseband signal is a digital signal, but is not binarized with 0 and 1, and is therefore referred to as a "signal" in the first embodiment. In the first embodiment, both data and hard decision values ​​refer to the same thing binarized with 0 and 1, but data obtained by demodulating and decoding a signal and binarized with 0 and 1 in which no error is detected by an error check is distinguished and referred to as a hard decision value. A signal from one target terminal extracted from a superimposed signal is an example of a "first signal". Data (hard decision value) obtained by demodulating and decoding a signal from one target terminal extracted from a superimposed signal and in which no error is detected by a CRC error check is an example of a "first data".

[0030] (2) In the replica signal generation process, a replica of the desired signal is generated by encoding and modulating the hard decision value. The replica of the desired signal is called a replica signal. (3) In the replica signal removal process, the replica signal of the desired signal is removed from the superimposed signal. The replica signal is an example of a "second signal."

[0031] The processes (1)-(3) are repeated for the superimposed signal after the replica signal has been removed and for the unseparated terminals, thereby separating the signals from each terminal contained in the superimposed signal. The SIC process ends, for example, when all terminals have been separated or an error occurs in the error check. (1) The data acquisition process of the desired signal is an example of a "first process". (2) The replica signal generation process is an example of a "second process". (3) The replica signal removal process is an example of a "third process".

[0032] In the example shown in FIG. 2, first, the desired signal of terminal A is obtained, and a replica signal of the desired signal of terminal A is removed from the superimposed signal including the signal of terminal AE. Next, the desired signal of terminal B is obtained, and a replica signal of the desired signal of terminal B is removed from the superimposed signal including the signal of terminal BE. Next, the desired signal of terminal C is obtained, and a replica signal of the desired signal of terminal B is removed from the superimposed signal including the signal of terminal CE. Finally, the desired signal of terminal D is obtained, and a replica signal of the desired signal of terminal D is removed from the superimposed signal including the signal of terminal DE, and the remaining signal becomes the desired signal of terminal E, and the SIC processing ends. In the example shown in FIG. 2, the processing of (1)-(3) is repeated four times. The order of terminals from which signals are separated is, for example, the order of terminals with the largest power of received signals. However, this is not limited to this.

[0033] Returning to FIG. 1, in the first embodiment, it is assumed that an overloaded MIMO state occurs in which the number of terminals N is greater than the number of receiving antennas M at the base station 1. In the case of overloaded MIMO, since the number of transmitting terminals (N) is greater than the number of receiving antennas (M) at the base station, signals from NM terminals cannot be cancelled even if a predetermined weight W of receiving diversity is used. Since signals from NM terminals that cannot be cancelled remain as interference signals, there is a possibility that when demodulating a desired signal, the data demodulated and decoded from the desired signal may become erroneous due to the influence of the interference signals. That is, in the case of overloaded MIMO, in the desired signal data acquisition process (1) of the SIC process, the data obtained by demodulation and decoding may become erroneous in the error check, and there is an increased possibility that a terminal may not be able to obtain a hard decision value.

[0034] If a hard decision value cannot be obtained in the (1) desired signal data acquisition process of the SIC process, the following (2) replica signal generation process and (3) replica signal removal process cannot be performed. The IC process itself ends at that point. This could result in an increase in the number of devices that receive the signal but are unable to obtain the data.

[0035] Also, (1) if a hard decision value cannot be obtained in the data acquisition process of the desired signal, the SIC process may be performed first for other terminals that have not been separated, and then, at some point thereafter, the SIC process may be performed again for the terminals for which a hard decision value cannot be obtained. However, even in this case, there is a possibility that a hard decision value cannot be obtained for all terminals whose signals are included in the superimposed signal.

[0036] Therefore, in the first embodiment, each base station 1 transmits the hard decision value acquired in (1) desired signal data acquisition processing of the SIC processing to the backbone line 50 together with the identification information of the target terminal, and shares them among the base stations 1. When the base station 1 cannot acquire a hard decision value in (1) desired signal data acquisition processing of the SIC processing, it executes (2) replica signal generation processing and (3) replica signal removal processing using the hard decision value of the target terminal acquired by another base station 1.

[0037] As a result, (1) even if a hard decision value cannot be acquired in the data acquisition process for the desired signal, the SIC process can be continued, and the number of terminals for which a hard decision value cannot be acquired can be kept small.

[0038] In the first embodiment, each base station 1 demodulates a signal from a terminal 4 to acquire data, and therefore, a MEC server 2 that processes the data is connected to each base station 1. The MEC server 2 processes data such as responses of HTTP (HyperText Transfer Protocol). The MEC server 2 executes a predetermined process according to the data and returns a response to the terminal 4 that sent the data. That is, the data from the terminal 4 demodulated by the base station 1 is processed by the MEC server 2 connected to the base station 1, so that the data can be processed without being sent to the backbone line 50, shortening the response time to the terminal 4 and achieving low latency. The MEC server 2 is an example of a "server".

[0039] The control station 3 receives the hard decision value and the identification information of the terminal 4 from each base station 1, and transmits the hard decision value and the identification information of the terminal 4 to other base stations 1. This allows the base stations 1 to share the hard decision value even when there are three or more base stations 1 in a cell.

[0040] In addition, when MIMO reception occurs within the cell, the control station 3 receives from each base station 1 a report of information on the terminal 4 whose signal the base station 1 has received, and grasps the demodulation status of the signal of the terminal 4 transmitting within the cell under its control from the hard decision value transmitted from each base station 1 and the identification information of the terminal 4. When demodulation of the signal of all terminals 4 transmitting within the cell under its control is completed, the control station 3 instructs each base station 1 to end MIMO. When the base station 1 receives an instruction to stop MIMO reception processing from the control station 3, it stops SIC processing and deletes information on MIMO reception. This eliminates the need to execute extra SIC processing in the base station 1, reducing the processing load of the base station 1. The control station 3 is an example of an "information processing device".

[0041] 3 is a diagram showing an example of the hardware configuration of the base station 1 and the control station 3 of the first embodiment. The base station 1 has, as its hardware configuration, a processor 11, a memory 12, an internal interface (IF) 13, a network IF 14A that connects to a backbone line 50, a network IF 14B that connects to the MEC server 2, a radio processing device 15, and an antenna 16.

[0042] The processor 11 is, for example, a Central Processing Unit (CPU) or a Microprocessor Unit (MPU). The processor 11 is not limited to a single processor. The processor 11 may have a multi-processor configuration. Also, a single physical CPU connected via a single socket may have a multi-core configuration. Furthermore, the processor 11 may include an arithmetic device of various circuit configurations, such as a digital signal processor (DSP) or a graphics processing unit (GPU). The processor 11 may also cooperate with an integrated circuit (IC), other digital circuits, or analog circuits. The integrated circuit may include an LSI, an application specific integrated circuit (ASIC), or a programmable logic device (PLD). The PLD may be, for example, a field-programmable gate array (FP The processor 11 may include a microcontroller (MCU), a system-on-a-chip (SoC), a system LSI, a chip set, or the like.

[0043] 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.

[0044] The network IF 14A is a communication device for the base station 1 to access a backbone line 50 to which other base stations are connected. The backbone line 50 is, for example, a wired network using optical communication. In this case, the network IF 14A is, for example, an X1 interface.

[0045] The network IF 14B is a communication device for connecting the MEC server 2. The network connecting the MEC server 2 is, for example, a LAN (Local Area Network) or the like. The network IF 14B is, for example, a NIC (Network Interface Card). The network connecting the MEC server 2 may be a wireless network. In that case, the network IF 14B is a wireless communication circuit.

[0046] The radio processing device 15 includes a transceiver for transmitting radio signals and a receiver for receiving radio signals, and is connected to M antennas 16. The radio processing device 15 may have M systems of transceivers and receivers, the number of which is equal to the number of antennas. The radio processing device 15 is called a remote radio head (RRH), and may be configured to be connected to the baseband device via a wired network using optical communication and installed remotely. Alternatively, a configuration in which multiple remote radio heads are connected to one baseband device may be used. The network connecting the baseband device and the remote radio heads is also called a fronthaul.

[0047] Next, the control station 3 is, for example, a dedicated or general-purpose computer. The control station 3 includes, as a hardware configuration, a processor 31, a memory 32, an internal IF 33, a network IF 34, and an external storage device 35. The processor 31, the memory 32, the internal IF 33, and the network IF 34 are similar to the processor 11, the memory 12, the internal IF 13, and the network IF 14A.

[0048] The external storage device 35 stores various programs and data used by the processor 31 when executing each program. The external storage device 35 is, for example, an erasable programmable ROM (EPROM) or a hard disk drive. The programs stored in the external storage device 35 include, for example, an operating system (OS) and various other application programs. Note that the hardware configurations of the base station 1 and the control station 3 are not limited to those shown in Fig. 3. The hardware configuration of the MEC server 2 is similar to that of the control station 3, and includes a processor, a memory, an external storage device, and a network interface.

[0049] Fig. 4 is a diagram showing an example of the functional configuration of the base station 1 and the control station 3. The base station 1 has a replica removing unit 101, a reception diversity processing unit 102, a demodulation and decoding unit 103, a CRC unit 104, a replica generating unit 105, a selection unit 106, and a control unit 107. The processor 11 shown in Fig. 3 executes an instruction sequence (computer program) executablely deployed in the memory 12, thereby performing each process of the replica removing unit 101, the reception diversity processing unit 102, the demodulation and decoding unit 103, the CRC unit 104, the replica generating unit 105, the selection unit 106, and the control unit 107.

[0050] The replica removal unit 101 executes replica signal removal processing (3) of the SIC processing. Specifically, the replica removal unit 101 subtracts a replica signal of a received signal from one terminal 4 generated by a replica generation unit 105 described later from a superimposed signal from which replica signals of each received signal received at M receiving antennas 16 or received signals from one or more terminals 4 have been removed. Since a received signal exists for each receiving antenna 16, the replica signal generated by the replica generation unit 105 is also generated for each receiving antenna 16, and the replica signal is subtracted from the received signal for each receiving antenna 16.

[0051] The reception diversity processing unit 102, the demodulation and decoding unit 103, and the CRC unit 104 execute (1) data acquisition processing of the desired signal in the SIC processing. The reception diversity processing unit 102 receives an input of the superimposed signal from the replica removal unit 101, and performs reception diversity processing using a predetermined weight, for example, by the MMSE method, to suppress (cancel) interference other than the desired signal of the target terminal 4, and extract the desired signal of the target terminal 4. The desired signal of the target terminal 4 is output to the demodulation and decoding unit 103. As the target terminal 4, for example, the terminal 4 with the largest reception power may be selected from among the unseparated terminals 4.

[0052] The demodulation and decoding unit 103 generates (demodulates) a bit string from the desired signal input from the reception diversity processing unit 102, and decodes the obtained bit string using an error correction code to obtain data. The decoded data is output to the CRC unit 104.

[0053] The CRC unit 104 performs an error check using a CRC on the data input from the demodulation and decoding unit 103. Specifically, the CRC unit 104 performs a CRC calculation on the payload portion of the data input from the demodulation and decoding unit 103, and compares the calculation result with the value of the CRC portion of the data input from the demodulation and decoding unit 103. If the CRC calculation result and the value of the CRC portion of the data input from the demodulation and decoding unit 103 match, there is no error, and the data input from the demodulation and decoding unit 103 is a hard decision value. On the other hand, if the CRC calculation result and the value of the CRC portion of the data input from the demodulation and decoding unit 103 do not match, there is an error, and the data input from the demodulation and decoding unit 103 is determined to be incorrect data and is discarded.

[0054] The CRC unit 104 outputs the result of the CRC error check, the identification information of the target terminal 4, and, if there is no error, the hard decision value to the selection unit 106. If there is no CRC error, the CRC unit 104 outputs the identification information of the target terminal 4 and the hard decision value to the backbone line 50. If there is no CRC error, the CRC unit 104 transmits the hard decision value to the MEC server 2. The identification information of the terminal 4 is included in the received signal from the terminal 4. In the first embodiment, the identification information of the target terminal 4 and the hard decision value are transmitted to the control station 3 through the backbone line 50.

[0055] The replica generating unit 105 executes the replica signal generation process (2) of the SIC process. Specifically, the replica generating unit 105 generates a replica signal of the signal received from the target terminal 4 at the antenna 16, based on the hard decision value of the target terminal 4 input from the selection unit 106. The replica generating unit 105 performs error correction coding on the input hard decision value, digitally modulates the error correction coded signal, performs transmit diversity processing on the digitally modulated signal, and multiplies the transmit diversity processed signal by a channel matrix to generate a replica signal. The replica generating unit 105 outputs the generated replica signal to the replica removing unit 101.

[0056] The selection unit 106 receives the hard decision value acquired by another base station 1 and the identification information of the corresponding terminal 4 from the backbone line 50. The selection unit 106 stores the received hard decision value and the identification information of the terminal 4 in a storage area of ​​the memory 12.

[0057] The selection unit 106 receives an input of the result of the CRC error check from the CRC unit 104. Based on the result of the CRC error check, the selection unit 106 selects whether to use the hard decision value acquired by the own station or the hard decision value received from the other station to generate a replica signal. If the result of the CRC error check from the CRC unit 104 indicates that there is no error, the selection unit 106 selects the hard decision value acquired by the own station, i.e., the hard decision value input from the CRC unit 104, and outputs it to the replica generation unit 105. If the result of the CRC error check from the CRC unit 104 indicates that there is an error, the selection unit 106 selects the hard decision value received from the other station, and outputs it to the replica generation unit 105.

[0058] The control unit 107 controls the processing in the base station 1. The control unit 107 acquires, from the receive diversity processing unit 102, the identification information of the terminals 4 whose signals have been received by the M receiving antennas 16, creates a signal reception list including the identification information of the terminals 4 whose signals have been received, and transmits it to the control station 3 through the backbone line 50. The identification information of the terminals 4 whose signals have been received by the M receiving antennas 16 is acquired, for example, by receiving a reference signal transmitted by the terminal 4 before transmitting user data.

[0059] Furthermore, the control unit 107 receives an instruction to stop MIMO reception processing from the control station 3 via the backbone line 50. When an instruction to stop MIMO reception processing is received, the control unit 107 stops SIC processing and deletes information related to MIMO reception processing. The information related to MIMO reception processing includes, for example, identification information of terminals 4 whose signals are received by M antennas 16, identification information of terminals 4 corresponding to hard decision values ​​of other base stations 1, etc.

[0060] The functional configuration of the base station 1 is not limited to that shown in Fig. 4. In Fig. 4, the base station 1 includes one replica generation unit 105 and a selection unit 106, and the selection unit 106 selects a hard decision value used to generate a replica signal and outputs it to the replica generation unit 105. Alternatively, the base station 1 may include a replica generation unit 105A that generates a replica signal from a hard decision value acquired by the base station itself, a replica generation unit 105B that generates a replica signal from a hard decision value received from another station, and the selection unit 106, and the selection unit 106 may select which of the replica generation unit 105A and the replica generation unit 105B to activate according to the result of a CRC error check.

[0061] Next, the control station 3 includes a control unit 301 as a functional configuration. The control unit 301 keeps track of all terminals 4 present within the cell. This is done, for example, by location registration at the time of initial connection of the terminals 4. Furthermore, when simultaneous reception of signals from multiple terminals 4 occurs by MIMO, the control unit 301 receives from each base station 1 a signal reception list of terminals 4 whose signals have been received by each base station 1. The signal reception list includes identification information of terminals 4 whose signals have been received by the base station 1. This allows the control unit 301 to keep track of terminals 4 that are transmitting within the cell and terminals 4 whose signals are being received by each base station 1.

[0062] The control unit 301 receives the hard decision value and the corresponding signal from each base station 1 via the backbone line 50. The control unit 301 receives the hard decision value and the identification information of the terminal 4. This allows the control unit 301 to grasp the demodulation status of the signal of the terminal 4 that is transmitting within the cell under its management. The control unit 301 shares the hard decision value received from one base station and the identification information of the corresponding terminal 4 between the base stations 1. Specifically, the control unit 301 identifies the base station 1 that is receiving a signal from the terminal 4 from which the identification information is received, and transmits the received hard decision value and the identification information of the corresponding terminal 4 to the identified base station 1 other than the base station 1 that received the hard decision value. Note that this is not limited to this, and when the control unit 301 receives the hard decision value and the identification information of the corresponding terminal 4 from one base station, it may transmit the received hard decision value and the identification information of the corresponding terminal 4 to another base station 1.

[0063] Furthermore, when the control unit 301 detects that signal demodulation has been completed for all terminals 4 transmitting signals within the cell under its control, it transmits an instruction to stop MIMO reception processing to each base station 1 within the cell via the backbone line 50. Upon receiving the instruction to stop MIMO reception processing, the base station 1 stops SIC processing and deletes information related to MIMO reception.

[0064] 5 is an example of a terminal management table of the control station 3. The terminal management table is a table for managing the transmission status of the terminal 4 in the cell and the demodulation status of the signal during MIMO reception. The terminal management table is stored in a storage area of ​​the memory 32 of the control station 3, for example.

[0065] The terminal management table includes entries for the number of terminals 4 present in the cell. When a terminal 4 that has newly entered the cell is detected, the control unit 301 adds an entry for the terminal 4 to the terminal management table. When a terminal 4 that has newly entered the cell is detected, the control unit 301 deletes the entry for the terminal 4 from the terminal management table.

[0066] Each entry includes fields of terminal ID, base station A receiving terminal, base station B receiving terminal, ..., and decoded. The terminal ID field stores identification information of the terminal 4 present in the cell. The base station A receiving terminal, base station B receiving terminal, ... fields store flags indicating whether each base station in the cell is receiving a signal from the terminal 4. For example, when the base station X is receiving a signal from the terminal 4 corresponding to the entry, the value of the base station X receiving terminal field is "1". The initial value of the base station A receiving terminal, base station B receiving terminal, ... fields is "0". For example, when the signal reception list received from the base station X includes identification information of the terminal #N corresponding to the entry, the control unit 301 sets a flag in the base station X receiving terminal field of the terminal #N.

[0067] The demodulated field stores a flag indicating whether demodulation of the signal of the terminal 4 corresponding to the entry has been completed or not. For example, if demodulation of the signal from the terminal 4 corresponding to the entry has been completed, the value of the demodulated field of the terminal 4 is "1". The initial value of the demodulated field is "0". When the identification information and hard decision value of terminal #N are received from any of the base stations 1, the control unit 301 sets a flag in the demodulated field of terminal #N.

[0068] The control unit 301 of the control station 3 identifies the base station 1 that transmits the hard decision value received from one base station 1 and the identification information of the terminal 4, based on the terminal management table. Also, the control unit 301 of the control station 3 determines whether demodulation of signals from all terminals 4 transmitting within the cell is completed, based on the terminal management table. Note that the terminal management table shown in FIG. 5 is an example, and is not limited to the one shown in FIG. 5.

[0069] 6 is an example of a flowchart of the MIMO reception process of the base station 1. The process shown in FIG. 6 is repeatedly executed while the base station 1 is in operation. In the OP101, the processor 11 calculates the MIMO reception signals (superimposed signals) received by the M reception antennas 16 and the radio processing device 15. It is assumed that the number of terminals receiving signals is N. Furthermore, in the OP 101, the processor 11 generates a signal reception list and transmits it to the control station 3.

[0070] The processing from OP102 onwards is repeatedly executed the number of times corresponding to the number of terminals of the received signal (N-1), or until an instruction to stop the MIMO receiving processing is received from the control station 3. In OP102, the processor 11 determines the target terminal 4, and separates and acquires the signal received from the target terminal 4 (desired signal) from the received signal by, for example, the MMSE method. The processing of OP102 corresponds to the processing of the receive diversity processing unit 102.

[0071] In OP103, the processor 11 executes digital demodulation processing on the desired signal acquired in the processing of OP102, and further performs decoding using error correction coding. That is, the processor 11 extracts a bit string as a baseband signal from the desired signal, which is a modulated carrier signal, and decodes data from the error correction coded signal, which is the demodulated baseband signal. The processing of OP103 corresponds to the processing of the demodulation and decoding unit 103.

[0072] In OP 104, the processor 11 performs a CRC check on the data acquired in the processing in OP 103. The processing in OP 104 corresponds to the processing in the CRC unit 104.

[0073] In OP105, the processor 11 determines whether or not the result of the CRC check of the data acquired in the process of OP103 indicates that there is an error. If the result of the CRC check of the data acquired in the process of OP103 indicates that there is an error (OP105: YES), the process proceeds to OP109. If the result of the CRC check of the data acquired in the process of OP103 indicates that there is no error (OP105: NO), the process proceeds to OP106.

[0074] In OP106, the processor 11 transmits a hard decision value, which is data without error as a result of the check, to the control station 3 through the backbone line 50, and to the MEC server 2 connected to the own station. In OP107, the processor 11 determines whether or not the target terminal 4 is a terminal that has already removed a replica signal from a superimposed signal. If the target terminal 4 is a terminal that has already removed a replica signal from a superimposed signal (OP107: YES), the process proceeds to OP111. If the target terminal 4 is a terminal that has already removed a replica signal from a superimposed signal (OP107: NO), the process proceeds to OP111.

[0075] In OP108, the processor 11 generates a replica signal of the received signal from the target terminal 4 from the hard decision value acquired in OP103, that is, the hard decision value acquired by the local terminal.

[0076] In OP109, the processor 11 determines whether or not the hard decision value of the target terminal 4 acquired by the other base station 1 has been received. If the hard decision value of the target terminal 4 acquired by the other base station 1 has been received (OP109: YES), the process proceeds to OP110. If the hard decision value of the target terminal 4 acquired by the other base station 1 has not been received (OP109: NO), the process proceeds to OP112.

[0077] In OP110, the processor 11 generates a replica signal of the received signal from the target terminal 4 from the hard decision value of the target terminal 4 acquired by another base station 1. The processing of OP105 to OP110 corresponds to the processing of the selection unit 106 and the replica generation unit 105.

[0078] In OP111, the processor 11 removes the replica signal generated by the processing in OP 108 or OP 110 from the superimposed signal. The processing in OP 111 corresponds to the processing in the replica removing unit 101.

[0079] In OP112, the processor 11 determines whether or not an instruction to stop MIMO reception processing has been received from the control station 3. If an instruction to stop MIMO reception processing has been received from the control station 3 (YES in OP112), the processor 11 deletes information related to MIMO reception processing in the memory 12, and the processing shown in Fig. 6 ends. If an instruction to stop MIMO reception processing has been received from the control station 3 (YES in OP112), the processing proceeds to OP102 for the unseparated terminal 4. The processing in OP112 corresponds to the processing of the control unit 107.

[0080] In addition, when there is no overloaded MIMO, that is, when the number of receiving antennas M is equal to or greater than the number of terminals N, the effect of interference signals on the desired signal in the receiving diversity processing is small, so the probability of an error in the CRC check is small. Therefore, when there is no overloaded MIMO, the OP105 makes a negative decision, and it is possible to separate the signals for N terminals and obtain data without using the hard decision value received from the other station. In the case of overloaded MIMO, as described above, the possibility of a CRC error increases, so the OP105 is likely to make a positive decision, and it is likely to use the hard decision value received from the other station.

[0081] Fig. 7 is an example of a flowchart of the terminal management process of the control station 3. The process shown in Fig. 7 is repeatedly executed at a predetermined cycle.

[0082] In OP201, the processor 31 determines whether or not a hard decision value and identification information of the corresponding terminal 4 have been received from the base station 1. If a hard decision value and identification information of the corresponding terminal 4 have been received from the base station 1 (OP201: YES), the process proceeds to OP202. If a hard decision value and identification information of the corresponding terminal 4 have been received from the base station 1 (OP201: NO), the process shown in FIG. 7 ends.

[0083] In OP202, the processor 31 sets a flag in the decoded field of the entry in the terminal management table whose terminal ID field value matches the received identification information, thereby recording that modulation of the signal from the terminal 4 of the received identification information has been completed.

[0084] In OP203, the processor 31 refers to the terminal management table and determines whether or not signal demodulation has been completed for all terminals 4 transmitting signals within the cell. If signal demodulation has been completed for all terminals 4 transmitting signals within the cell (OP203: YES), the process proceeds to OP204. In OP204, the processor 31 transmits an instruction to each base station 1 to stop MIMO reception processing via the backbone line 50. Then, the process shown in FIG. 7 ends.

[0085] In OP203, if there is a terminal 4 that has not yet completed demodulation of a signal among the transmitting terminals 4 in the cell (OP203: NO), the process proceeds to OP205. In OP205, the processor 31 extracts from the terminal management table a base station 1 that is receiving a signal from the terminal 4 that corresponds to the received identification information, and transmits the received hard decision value and the identification information of the corresponding terminal 4 to the extracted base station 1 via the backbone line 50. Then, the process shown in FIG. 7 ends.

[0086] <Effects of the First Embodiment> In the first embodiment, by sharing hard decision values ​​between base stations 1, even for erroneous data in overloaded MIMO, a replica signal of the signal from terminal 4 can be generated using the hard decision value corresponding to terminal 4 that transmitted the data. This improves the inter-terminal interference removal performance in base station 1, and improves wireless communication quality.

[0087] In the first embodiment, the base station 1 demodulates the signal from the terminal 4 to obtain data. By connecting an MEC server 2 to the base station 1 and having the MEC server 2 process the data, a response can be returned to the terminal 4 more quickly, thereby achieving low latency.

[0088] In the first embodiment, each base station 1 transmits a hard decision value to the backbone line 50. Since the hard decision value is binarized data, the size of the hard decision value is smaller than that of a baseband signal, for example. Therefore, according to the first embodiment, the use of the bandwidth of the backbone line 50 can be reduced. It is possible.

[0089] In the first embodiment, the control station 3 receives a hard decision value and identification information of the terminal 4 from each base station 1, extracts another base station 1 receiving a signal from the terminal 4, and transmits the received hard decision value and identification information of the terminal 4 to the extracted base station 1. This makes it possible to prevent the hard decision value and identification information of the terminal 4 from being transmitted to a base station 1 that does not require the hard decision value of the terminal 4.

[0090] In the first embodiment, the control station 3 receives hard decision values ​​and identification information of the terminals 4 from each base station 1 to manage the demodulation status of signals from the terminals 4 transmitting within the cell under its management. When the control station 3 detects that demodulation of signals from all the terminals 4 transmitting within the cell under its management is completed, the control station 3 transmits an instruction to each base station 1 to stop MIMO reception processing. This allows each base station 1 to stop MIMO reception processing even if there is, for example, an unseparated terminal 4, so that the processing load of each base station 1 can be reduced. The processing shown in FIG. 7 corresponds to the processing of the control unit 301 of the control station 3.

[0091] Also, for example, compared to the case where each base station 1 does not demodulate the signal received from the terminal, but instead aggregates the baseband signal in the control station 3 and the control station 3 performs the demodulation, the total amount of MIMO calculations in the entire system is smaller when each base station 1 demodulates the signal received from the terminal in the first embodiment. This is because the size of the matrix in the calculation in the receive diversity processing increases with the number of antennas. For example, assuming that the number of antennas in each base station 1 is M, when each base station 1 performs demodulation as in the first embodiment, the size of the matrix in the calculation in the receive diversity processing is M×M. On the other hand, when the control station 3 performs demodulation from the baseband signal, the size of the matrix in the calculation in the receive diversity processing is (M×number of base stations)×(M×number of base stations).

[0092] <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.

[0093] The processes and means described in this disclosure can be freely combined and implemented as long as no technical contradiction occurs.

[0094] 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.

[0095] 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 may be, for example, a magnetic disk (floppy disk (registered This includes any type of disk, such as a portable (trademark) disk, hard disk drive (HDD), optical disk (CD-ROM, DVD disk, Blu-ray disk, etc.), read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic card, flash memory, optical card, and any type of medium suitable for storing electronic instructions. [Explanation of symbols]

[0096] 1...Base station 2. MEC Server 3. Control Station 4. Terminal 11, 31 Processor 12, 32... Memory 13, 33...Internal IF 14A, 14B, 34 Network IF 14B Network Interface 15. Radio processing device 35...External storage device 301 Control section 50··Backbone Line 100 Wireless communication system 101 Replica removal section 102 Reception diversity processing unit 103 Demodulation and decoding unit 104...CRC section 105 Replica generation unit 106 Selection section 107 Control section

Claims

1. A communication unit connected to a backbone line to which one or more base stations are connected; M (1<M) receiving antennas; A first process of acquiring a first signal from a first terminal that is one of the N terminals by a predetermined process from signals simultaneously received from N (1<N) terminals, and acquiring first data by demodulating and decoding the first signal; a second process of generating a second signal, which is a replica of a signal arriving from the first terminal before the predetermined process is performed, based on the first data; a third process of extracting a signal excluding the generated second signal from the received signal; Repeating the first to third processes for the extracted signal, one of the N-1 terminals excluding the first terminal from the N terminals as a new first terminal; A base station comprising a control unit that executes The control unit is sharing the first data acquired by the first process with one or more other base stations via the backbone line; When the number of the N terminals is greater than the number of the M receiving antennas, for a terminal from which the first data has not been acquired by the first processing, the second processing and the third processing are performed using the first data received from any one of the one or more other base stations. Base station.

2. A communication unit connected to a backbone line to which one or more base stations are connected; M (1<M) receiving antennas; From signals received simultaneously from N (1<N) terminals, the N a first process of acquiring a first signal from a first terminal, the first terminal being one of the terminals, and demodulating and decoding the first signal to acquire first data; a second process of generating a second signal, which is a replica of a signal arriving from the first terminal before the predetermined process is performed, based on the first data; a third process of extracting a signal excluding the generated second signal from the received signal; Repeating the first to third processes for the extracted signal, one of the N-1 terminals excluding the first terminal from the N terminals as a new first terminal; A base station comprising a control unit that executes The control unit is sharing the first data acquired by the first process with one or more other base stations via the backbone line; When the number of the N terminals is greater than the number of the M receiving antennas, for a terminal from which the first data has not been acquired by the first processing, the second processing and the third processing are performed using the first data received from any one of the one or more other base stations. A base station; a server that performs processing according to the first data acquired by the first processing by the base station and responds to the first terminal; Includes multiple combinations of system.

3. A communication unit connected to the backbone line; receiving first data transmitted from the base station; Transmitting the received first data to another base station; A control unit that executes the above. The system of claim 2 further comprising an information processing device comprising:

4. The control unit of the information processing device Identifying a base station receiving a signal from the first terminal corresponding to the received first data; transmitting the received first data to the specified base station other than the base station which is a source of the first data; The system of claim 3.

5. The control unit of the information processing device when first data is acquired for all of a plurality of terminals that have transmitted signals and are present in a cell including a plurality of base stations, transmitting a stop of the first process to the third process to the plurality of base stations; 5. A system according to claim 3 or 4.

6. A communication unit connected to a backbone line to which one or more base stations are connected; M (1<M) receiving antennas; A base station comprising: A first process of acquiring a first signal from a first terminal that is one of the N terminals by a predetermined process from signals simultaneously received from N (1<N) terminals, and acquiring first data by demodulating and decoding the first signal; a second process of generating a second signal, which is a replica of a signal arriving from the first terminal before the predetermined process is performed, based on the first data; a third process of extracting a signal excluding the generated second signal from the received signal; Repeating the first to third processes for the extracted signal, one of the N-1 terminals excluding the first terminal from the N terminals as a new first terminal; Run sharing the first data acquired by the first process with one or more other base stations via the backbone line; When the number of the N terminals is greater than the number of the M receiving antennas, for a terminal from which the first data has not been acquired by the first processing, the second processing and the third processing are performed using the first data received from any one of the one or more other base stations. method.

7. An information processing device including a communication unit connected to the backbone line, receiving first data transmitted from the base station; Transmitting the received first data to another base station; Execute The method according to claim 6.

8. The information processing device, Identifying a base station receiving a signal from the first terminal corresponding to the received first data; transmitting the received first data to the specified base station other than the base station which is a source of the first data; The method of claim 7.

9. The information processing device, when first data is acquired for all of a plurality of terminals that have transmitted signals and are present in a cell including a plurality of base stations, transmitting a stop of the first process to the third process to the plurality of base stations; 9. The method according to claim 7 or 8.

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