Wireless communication device, communication system, wireless communication method, and program

Abstract

One aspect of the present invention is a wireless communication device comprising: a prediction unit that predicts communication quality with an counterpart device that performs wireless communication via one or more optical antennas; and a control unit that reduces the number of streams simultaneously transmitted and received for the antenna of which the communication quality is predicted to deteriorate by the prediction unit, or set the antenna to be used for diversity communication.

Description

[Technical Field]

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

[0002] High-frequency millimeter-wave bands are used in wireless systems such as 5G, and in order to achieve even higher speeds and capacities in future wireless systems such as 6G, it is expected that even higher frequency bands will be used, which will enable wider bandwidths to be secured. High-frequency bands are known to have large propagation losses and tend to travel in a straight line, and distributed antenna systems are being considered to improve connectivity in covering communication areas (see Non-Patent Documents 1 and 2).

[0003] In a distributed antenna system, by using multiple distributed antennas to perform SU-MIMO (Single User Multiple-Input Multiple-Output) or MU-MIMO (Multi User MIMO), it is possible to improve frequency utilization efficiency and capacity and throughput.When performing MIMO, it is generally assumed that in order to reduce inter-stream interference, channel information (CSI: Channel State Information) between the distributed antennas and the terminal station (UE: User Equipment) is acquired and precoding is performed on the downlink and postcoding on the uplink at the base station (BS).

[0004] Here, if the spatial correlation between antennas is high, it becomes difficult to separate the streams using precoding and postcoding, so it is necessary to reduce the number of streams (number of MIMO layers) that are simultaneously transmitted and received. In this way, rank adaptation, which controls the number of streams based on the reception conditions, is also used (see Non-Patent Document 3). Rank adaptation increases the number of MIMO layers when the channel conditions are good, and uses diversity when the channel conditions are poor, based on the SINR and the spatial correlation between antennas. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] NTT Docomo, Inc., "Docomo 6G White Paper 4.0 Edition," November 2021 [Non-patent document 2] Uchida, Iwakuni, Kita, Onisawa, Kishiyama, Suyama, Nagata, and Asai, "Study on High-Frequency Distributed Antenna Systems for the 6G Era," IEICE Technical Report RCS2020-148, pp. 73-78, December 2020. [Non-patent document 3] T. Taoka, T. Nagata, T. Takeda, T. Kakishima, Y. Yu, and T. Kusume, "MIMO and Inter-Cell Cooperative Transmission and Reception Technology in LTE-Advanced," NTT DOCOMO Technical Journal, Vol. 18, No. 2, July 2010. Summary of the Invention [Problem to be solved by the invention]

[0006] In a distributed antenna system, when a UE communicates by connecting to a single distributed antenna, if the link with the BS is cut off due to obstruction caused by movement or changes in the surrounding environment, communication cannot be continued until the link is reconnected. Also, when switching the destination distributed antenna based on reception quality, there are concerns about an increase in control signals and processing associated with the switching, as well as an increase in the load of data transfer between distributed antennas via the BS.

[0007] Furthermore, when MIMO communication is performed using multiple antennas in a distributed antenna system, if the link with one of the distributed antennas is cut off due to obstruction caused by movement or changes in the surrounding environment, throughput will decrease. In particular, if interference reduction is performed by precoding between antennas performing MIMO communication, this will also affect the demodulation of signals from other distributed antennas that are not obstructed, raising concerns about further degradation of throughput.

[0008] In view of the above circumstances, an object of the present invention is to provide a technology that can improve the continuity of communication. [Means for solving the problem]

[0009] One aspect of the present invention is a wireless communication device that includes a prediction unit that predicts communication quality with an opposing device that communicates wirelessly via one or more antennas, and a control unit that reduces the number of streams that are simultaneously transmitted and received or sets an antenna that is predicted by the prediction unit to have deteriorated communication quality to be used for diversity communication.

[0010] One aspect of the present invention is a communication system including one or more antennas and a wireless communication device that controls the antenna, wherein the wireless communication device is equipped with a prediction unit that predicts communication quality with an opposing device that communicates wirelessly via the antenna, and a control unit that reduces the number of streams that are transmitted and received simultaneously or sets the antenna to be used for diversity communication for an antenna that is predicted by the prediction unit to have a deteriorated communication quality.

[0011] One aspect of the present invention is a wireless communication method comprising: a prediction step of predicting communication quality with a counterpart device that communicates wirelessly via one or more antennas; and a control step of reducing the number of streams simultaneously transmitted and received or setting an antenna for use in diversity communication for which the prediction step predicts that the communication quality will deteriorate.

[0012] One aspect of the present invention is a program for causing a computer to execute a prediction step of predicting communication quality with an opposing device that communicates wirelessly via one or more antennas, and a control step of reducing the number of streams transmitted and received simultaneously or setting the antenna for use in diversity communication for an antenna predicted by the prediction step to have degraded communication quality. [Effects of the Invention]

[0013] The present invention makes it possible to improve the continuity of communication. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating an example of a communication system including a base station as a wireless communication device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating an example of the configuration of a base station. [Figure 3] FIG. 2 is a diagram illustrating an example of the configuration of a prediction unit. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a prediction unit. [Figure 5] 10 is a flowchart showing the flow of a multiple connection control process. [Figure 6] 10 is a flowchart showing the flow of a predictive control process. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a diagram showing an example of a communication system 10 including a base station 100 as a wireless communication device according to this embodiment. The communication system 10 includes the base station 100, a plurality of antennas 200 (five in Fig. 1), and UE (User Equipment) 300. As shown in Fig. 1, the communication system 10 is a communication system to which a distributed antenna system is applied. The UE 300 is a mobile terminal such as a smartphone used by a user.

[0016] The base station 100 supports MIMO (Multiple-Input Multiple-Output). The base station 100 also controls antennas 200 that are arranged extending from the base station 100. Each of the distributed antennas 200 includes a radio unit (RU) function and supports beamforming by controlling the phase and / or amplitude of multiple elements to ensure gain in high frequency bands. The UE 300 may also support beamforming. The base station 100 also has a function to predict future communication quality of the UE 300 connected thereto.

[0017] Under normal control, the base station 100 performs downlink MIMO transmission by simultaneously transmitting multiple streams from multiple antennas 200. Not only downlink, but also uplink MIMO transmission may be performed by similarly receiving multiple streams simultaneously from multiple antennas 200. Note that the maximum number of streams that can be communicated simultaneously is determined by the maximum number of MIMO layers that can be processed by the base station 100, and all of the distributed antennas 200 may be used for communication simultaneously, or only some of the antennas 200 may be used.

[0018] FIG. 2 is a diagram illustrating an example configuration of a base station 100. The base station 100 is configured with a control unit 110, a prediction unit 120, a transmission unit 130, a signal processing unit 140, a beam control unit 150, a transmission / reception unit 160, and a storage unit 170. The control unit 110 controls the entire base station 100 and the antennas 200. The control unit 110 controls, for example, the allocation of communication resources to opposing devices. Furthermore, for an antenna 200 for which the prediction unit 120 predicts that communication quality will deteriorate, the control unit 110 reduces the number of streams (i.e., the number of layers) to be simultaneously transmitted and received, or sets the antenna 200 to be used for diversity communication. In this specification, the number of streams and the number of layers are synonymous.

[0019] The prediction unit 120 predicts the communication quality with the UE 300. For example, the communication quality may be predicted to be reduced if the fluctuation range of the received power of the UE 300 within a certain period of time exceeds a set threshold, assuming obstruction around the UE 300. The prediction method may be a prediction method such as linear prediction based on communication quality records for each movement, a method using machine learning, or a method using an external sensor such as a camera. The storage unit 170 stores various information required for the prediction by the prediction unit 120. For example, the storage unit 170 stores feedback information from the UE 300 or values ​​sensed by an external sensor.

[0020] The transmission unit 130 transmits signals between a higher-level device and other wireless communication devices on the network. The transmission unit 130 outputs a received signal to the signal processing unit 140, and transmits a signal input from the signal processing unit 140 to the higher-level device, other wireless communication devices, etc. The signal processing unit 140 performs signal processing related to wireless communication. For example, the signal processing unit 140 performs signal processing on a signal input from the transmission unit 130 and outputs the signal to the beam control unit 150. The signal processing unit 140 also performs signal processing on a signal input from the beam control unit 140 and outputs the signal to the transmission unit 130. Furthermore, the signal processing unit 140 outputs feedback information received from the UE 300 to the control unit 110 and the storage unit 170. Note that in a case where the prediction unit 120 performs prediction using a value sensed by an external sensor, when the signal processing unit 140 receives the sensed value from the beam control unit 150, it outputs the sensed value to the storage unit 170.

[0021] The beam control unit 150 controls the beam formed by the antenna 200 using the transceiver unit 160 in accordance with the signal output from the signal processing unit 140. The beam control unit 150 outputs the signal output from the transceiver unit 160 to the signal processing unit 140. The transceiver unit 160 performs processing related to signals received by the antenna 200 and signals to be transmitted, in accordance with the control of the beam control unit 150. For example, the transceiver unit 160 performs beamforming that controls the phase and / or amplitude of the signal, and processing related to transmission and reception of the signal.

[0022] The configuration of the base station 100 is not limited to the configuration shown in Fig. 2. For example, the base station 100 may be configured such that functional units such as a signal processing unit and a beam control unit are divided into devices, such as a CU (Central Unit), DU (Distributed Unit), and RU in 5G NR (New Radio).

[0023] An example of the configuration of the prediction unit 120 will be described. Figures 3 and 4 are diagrams showing an example of the configuration of the prediction unit 120. The prediction unit 120 in Figure 3 stores fluctuations in received power over a certain period of time for all antennas 200 connected to UE 300 in the storage unit 170, predicts that an antenna 200 whose fluctuation range of received power exceeds a set threshold T is an antenna whose quality will deteriorate, and outputs the prediction to the control unit 110.

[0024] 4 is a diagram illustrating a configuration example in which prediction unit 120 uses a machine learning model. For example, a machine learning model that has learned in advance which antennas will deteriorate in quality from the position and moving direction of UE 300 is stored in storage unit 170. Then, when prediction unit 120 receives the position and moving direction of UE 300 as input, it uses the stored machine learning model to output to control unit 110 antennas that are expected to deteriorate in quality.

[0025] 3 and 4, the control unit 110 sets the input antenna to be deteriorated to reduce the number of streams to be transmitted and received simultaneously or to use the antenna for diversity communication, thereby improving the continuity of communication.

[0026] Next, a description will be given of feedback information received from UE 300. First, base station 100 transmits a reference signal to UE 300. UE 300 feeds back to base station 100 received signal strength, signal-to-noise power ratio, timestamp at reception, timestamp at transmission, CSI (Channel State Information), etc. from the received reference signal. In the case of a cellular system, the feedback information includes CQI (Channel Quality Indicator), RI (Rank Indicator), PMI (Precoding Matrix Indicator), etc.

[0027] Note that, taking into consideration the possibility that the number of layers may be 1, UE 300 may also feed back PMI etc. corresponding to 1 layer. Based on such feedback information, base station 100 determines the number of transmission layers using rank adaptation that takes into consideration the received SINR and spatial correlation between antennas 200.

[0028] Next, improvement of connectivity will be described. In this embodiment, in order to improve connectivity with the base station 100, the UE 300 is controlled by the base station 100 so as to connect to as many antennas 200 as possible, regardless of communication capacity or whether MIMO is applied. This control may be referred to as "multiple connection control."

[0029] Regarding this multiple connection control, UEs 300 may be classified into those to which the multiple connection control is applied and those to which the multiple connection control is not applied. Furthermore, in the multiple connection control, antennas 200 with high received power from a reference signal may be selected as the multiple antennas 200 to be connected to UE 300. Alternatively, antennas 200 with low spatial correlation from CSI may be selected as the multiple antennas 200 to be connected, taking MIMO communication into consideration. Alternatively, antennas 200 with low correlation in the surrounding shielding environment may be selected as the multiple antennas 200 to be connected, taking connectivity into consideration. Specifically, for example, a pair of antennas 200 may be selected that maximizes the sum of the angle differences calculated from the directions of each distributed antenna with UE 300 as the origin, based on the location information of UE 300 and the location information of each antenna 200. In either case, since UE 300 connects to multiple antennas 200, the continuity of communication can be improved.

[0030] Fig. 5 is a flowchart showing the flow of the multiple connection control process. The flowchart in Fig. 5 shows an example of a process for selecting antennas with high received power. In Fig. 5, the base station 100 transmits a reference signal to the UE 300 (step S101). The base station 100 acquires information on received power from the UE 300 via the antennas 200 (step S102). The base station 100 sorts the acquired received power (step S103). The base station 100 instructs the UE 300 to communicate with multiple antennas 200, including the antenna 200 corresponding to the maximum received power among the sorted received powers (step S104), and ends the multiple connection control process.

[0031] Next, a description will be given of a prediction control process using a prediction result by prediction section 120. Fig. 6 is a flowchart showing the flow of the prediction control process. In Fig. 6, base station 100 transmits a reference signal to UE 300 (step S201), and acquires the above-mentioned feedback information from UE 300 (step S202).

[0032] The control unit 110 focuses on one antenna 200 out of the multiple antennas 200 and determines the number of layers M using rank adaptation that takes into account the received SINR and spatial correlation between antennas based on feedback information (step S203). The control unit 110 determines whether the number of layers M is 2 or more (step S204). If the number of layers is 1 (step S204: NO), the control unit 110 sets the number of layers for all antennas to 1 (step S213), sets them to be used for diversity communication (step S214), and ends the process.

[0033] If the number of layers is two or more (step S204: YES), the control unit 110 assigns 0 to a counter N (step S205). This counter N is a counter for counting antennas whose fluctuation range of received power is less than a set threshold T. The prediction unit 120 focuses on one antenna and determines whether the fluctuation range of received power of this antenna is greater than or equal to the threshold T (step S206). If the fluctuation range of received power is greater than or equal to the threshold T (step S206: YES), the process proceeds to step S208. If the fluctuation range of received power is less than the threshold T (step S206: NO), the control unit 110 increments N by 1 (step S207).

[0034] The control unit 110 determines whether or not the process of determining whether the fluctuation range of the received power is equal to or greater than the threshold value T has been performed for all antennas (step S208). If the process has not been performed for all antennas (step S208: NO), the control unit 110 performs the process of step S206 for the antennas that have not been processed. If the process has been performed for all antennas (step S208: YES), the control unit 110 determines whether or not N is 0 or 1 (step S209). If N is 0 or 1 (step S209: YES), the process proceeds to step S213 described above.

[0035] If N is neither 0 nor 1 (step S209: NO), the smaller of M and N is set as L (step S210). The control unit 110 sets the number of layers for all antennas as L (step S211), sets them to be used for MIMO (step S212), and ends the process.

[0036] In the above process, the prediction unit 120 may predict whether the antenna 200 of interest is an antenna expected to deteriorate, in addition to other indicators such as a received power value and spatial correlation of a MIMO channel. After controlling the number of layers in this way, wireless communication is performed between the base station 100 and each antenna 200 and the UE 300, thereby improving the continuity of communication.

[0037] The control unit 110 and the prediction unit 120 may be configured using a processor such as a CPU (Central Processing Unit) and a memory. In this case, the control unit 110 and the prediction unit 120 function as the control unit 110 and the prediction unit 120 by the processor executing a program. Note that all or part of the functions of the control unit 110 and the prediction unit 120 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The above program may be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include portable media such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and a semiconductor storage device (e.g., a solid-state drive (SSD)), as well as storage devices such as a hard disk or semiconductor storage device built into a computer system. The above program may be transmitted via a telecommunications line.

[0038] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0039] The present invention is applicable to a wireless communication device such as a base station that wirelessly communicates with a UE. [Explanation of symbols]

[0040] 10 communication system, 100 base station, 110 control unit, 120 prediction unit, 130 transmission unit, 140 signal processing unit, 150 beam control unit, 150 performs signal processing on the signal input from the beam control unit, 160 transmission / reception unit, 170 storage unit, 200 antenna, 300 UE

Claims

1. A prediction unit that predicts communication quality with an opposite device that wirelessly communicates via a plurality of antennas, for each of the plurality of antennas; a control unit that sets an antenna, among the plurality of antennas, for which the prediction unit predicts that the communication quality will be degraded, to reduce the number of streams that are simultaneously transmitted and received or to use the antenna for diversity communication; A wireless communication device comprising:

2. The wireless communication device according to claim 1 , wherein the prediction unit predicts that communication quality will deteriorate if a fluctuation range of received power detected by the opposite device within a certain period of time exceeds a predetermined threshold.

3. The wireless communication device according to claim 1 , wherein the control unit controls the opposing device to perform wireless communication with the plurality of antennas.

4. The wireless communication device according to claim 1 , wherein the control unit controls the opposing device to perform wireless communication with a plurality of antennas including an antenna corresponding to a maximum reception power among the reception powers corresponding to the plurality of antennas.

5. The wireless communication device according to claim 1 , wherein the control unit determines the number of streams based on a channel quality indicator (CQI), a rank indicator (RI), or a precoding matrix indicator (PMI) fed back from the opposite device.

6. A communication system including a plurality of antennas and a wireless communication device that controls the plurality of antennas, The wireless communication device a prediction unit that predicts a communication quality with an opposite device that wirelessly communicates via the plurality of antennas, for each of the plurality of antennas; a control unit that sets an antenna, among the plurality of antennas, for which the prediction unit predicts that the communication quality will be degraded, to reduce the number of streams that are simultaneously transmitted and received or to use the antenna for diversity communication; A communication system comprising:

7. A prediction step of predicting communication quality with an opposing device that wirelessly communicates via a plurality of antennas, for each of the plurality of antennas; a control step of reducing the number of streams to be simultaneously transmitted and received or setting an antenna for which communication quality is predicted to deteriorate in the prediction step among the plurality of antennas to be used for diversity communication; A wireless communication method comprising:

8. On the computer, a prediction step of predicting, for each of a plurality of antennas, a communication quality with an opposite device that wirelessly communicates via the plurality of antennas; a control step of reducing the number of streams to be simultaneously transmitted and received or setting an antenna for which communication quality is predicted to deteriorate in the prediction step among the plurality of antennas to be used for diversity communication; A program to execute.

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