CONTROL METHOD AND WIRELESS COMMUNICATION SYSTEM

Abstract

One embodiment of the present invention is a control method in a wireless communication system provided with a plurality of distributed antennas that perform wireless communication with a user terminal and a plurality of signal processing units that connect to the distributed antennas and perform signal processing. The control method comprises: an initial allocation step for allocating the distributed antennas that connect to the signal processing units; an acquisition step for acquiring load information that indicates loads on the signal processing units; an assessment step for assessing, on the basis of the load information acquired through the acquisition step, whether the distributed antennas connecting to the signal processing units are to be reallocated; and a reallocation step for performing reallocation, and equalizing the loads of the plurality of signal processing units, when it is assessed through the assessment step that reallocation is to be performed.

Description

[Technical field]

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

[0002] 5G (fifth generation mobile communications system) uses high frequency millimeter wave bands, and in order to achieve even higher speeds and capacity in future wireless systems such as 6G, it is expected that even higher frequency bands that can secure wider bandwidths will be used.

[0003] High frequency bands are known to have large propagation losses and tend to travel in a very directional direction, and distributed antenna systems are being considered to improve connectivity in covering communication areas (see Non-Patent Document 1).

[0004] Fig. 5 shows an example of a typical base station configuration. The base station configuration in Fig. 5 includes a BBU (Base Band Unit) that performs processing of layers higher than the physical layer, an RRH (Remote Radio Head) that may include RF processing and a part of the physical layer, and an antenna. UE indicates a user terminal. The antenna may extend from the RRH or may be integrated with it.

[0005] Figure 6 shows an example of a base station configuration of a distributed antenna system. The base station configuration in Figure 6 includes a BBU, an RRH, and an antenna, similar to Figure 5. In the base station configuration in Figure 6, multiple antennas are extended from the RRH, and the same cell is covered by multiple antennas. This makes it possible to expand the communication area with the base station configuration in Figure 6. In addition, by coordinating multiple antennas to perform MIMO (Multiple Input and Multiple Output), it is expected that communication capacity will also increase. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] NTT Docomo, Inc., “Docomo 6G White Paper 2.0”, July 2020 [Non-Patent Document 2] K. Ito, M. Suga, Y. Shirato, N. Kita, and T. Onizawa, “A novel centralized beamforming scheme for radio-over-fiber systems with fixed wavelength allocation,” IEICE Communications Express, Vol. 8, No. 12. pp. 584-589, 2019. Summary of the Invention [Problem to be solved by the invention]

[0007] In the case of base station configurations such as those shown in Figures 5 and 6, antennas and cell resources are fixedly linked. Therefore, in base station configurations such as those shown in Figures 5 and 6, it is not possible to follow temporal fluctuations in load, such as uneven distribution of traffic volume and number of connected users depending on the cell. As a result, there is a high probability of causing a decrease in throughput and a shortage or surplus of cell resources.

[0008] In addition, with existing technology, by copying and distributing one cell resource to multiple antennas in a base station configuration such as that shown in Figure 6, it is possible to perform resource control across multiple areas within one cell resource, but it is not possible to perform resource control across multiple cell resources.

[0009] In view of the above circumstances, an object of the present invention is to provide a technique capable of realizing a control method and a wireless communication system capable of following fluctuations in load. [Means for solving the problem]

[0010] One aspect of the present invention is a control method in a wireless communication system including a plurality of distributed antennas that perform wireless communication with a user terminal and a plurality of signal processing units that are connected to the distributed antennas and perform signal processing, the control method including an initial allocation step of allocating the distributed antennas to be connected to the signal processing units, an acquisition step of acquiring load information indicating the load of the signal processing units, a determination step of determining whether or not to reallocate the distributed antennas connected to the signal processing units based on the load information acquired by the acquisition step, and a reallocation step of performing reallocation and leveling the load of the plurality of signal processing units when it is determined by the determination step that reallocation should be performed.

[0011] One aspect of the present invention is a control method in a communication system including a distributed antenna that performs wireless communication with a user terminal, and a plurality of signal processing units to which the distributed antenna is assigned and which perform processing related to signals transmitted and received from the assigned distributed antenna, the control method including an acquisition step of acquiring load information indicating a load on the signal processing units, and an allocation step of assigning the distributed antenna to the signal processing units so as to equalize the load on the plurality of signal processing units based on the load information acquired by the acquisition step.

[0012] One aspect of the present invention is a wireless communication system comprising a plurality of distributed antennas that perform wireless communication with a user terminal, and a plurality of signal processing units that are connected to the distributed antennas and perform signal processing, the wireless communication system comprising: an initial allocation unit that allocates the distributed antennas to be connected to the signal processing units; an acquisition unit that acquires load information indicating the load of the signal processing units; a determination unit that determines whether to reallocate the distributed antennas to be connected to the signal processing units based on the load information acquired by the acquisition unit; and a reallocation unit that performs reallocation and equalizes the load on the plurality of signal processing units when the determination unit determines that reallocation should be performed. Effect of the Invention

[0013] According to the present invention, it is possible to realize a control method and a wireless communication system capable of following fluctuations in load. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a configuration of a wireless communication system 1. FIG. [Diagram 2] 1 is a block diagram showing the configuration of a CS100; [Diagram 3] 1 is a flowchart showing the flow of processing by the CS100. [Figure 4] FIG. 13 is a diagram illustrating a modified example of the wireless communication system. [Diagram 5] FIG. 1 is a diagram showing a configuration of a conventional technique. [Figure 6] FIG. 1 is a diagram showing a configuration of a conventional technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. 1 is a block diagram showing a configuration of a wireless communication system 1 according to an embodiment. The wireless communication system 1 includes a CS (Central Station) 100, a switch 20, and a distributed antenna 30. UE indicates a user terminal.

[0016] Analog RoF (Radio over Fiber) technology is used in the wireless communication system 1. Specifically, waveform information of an analog signal is transmitted by optical fiber from the CS 100 to a base station where a distributed antenna 30 is installed. This allows the signal processing function to be concentrated in the CS 100, so that the base station only needs to have functions such as the distributed antenna 30, an amplifier, E / O conversion, and O / E conversion, making it possible to reduce the size and power consumption of the base station.

[0017] The CS100 communicates with the distributed antenna 30 via the switch 20. The CS100 also performs remote beam control that supports beamforming technology only at the aggregation station. The switch 20 is connected to the distributed antenna 30 and the CS100. Under the control of the CS100, the switch 20 dynamically assigns the distributed antenna 30 to multiple signal processing units provided in the CS100.

[0018] Fig. 2 is a block diagram showing the configuration of the CS100. The CS100 includes N (N is an integer of 2 or more) signal processing units 10-1, 10-2, ..., 10-N, an acquisition unit 40, and an allocation unit 50. When the signal processing units 10-1, 10-2, ..., 10-N are not particularly distinguished from each other, they are expressed as signal processing units 10. Furthermore, in the configuration of Fig. 2, J (J is an integer of 2 or more) distributed antennas 30-1, 30-2, ..., 30-J are provided. When the distributed antennas 30-1, 30-2, ..., 30-J are not particularly distinguished from each other, they are expressed as distributed antennas 30.

[0019] The signal processing unit 10 performs various processes on signals received from a higher-level device (not shown) and outputs the signals to the distributed antenna 30. The signal processing unit 10 also performs various processes on signals received from the distributed antenna 30 and outputs the signals to the higher-level device.

[0020] Several distributed antennas 30 are assigned to the signal processing unit 10. The distributed antennas 30 assigned to each signal processing unit 10 can be changed using the switch 20 under the control of the assignment unit 50.

[0021] The acquiring unit 40 acquires load information indicating the load of the signal processing unit 10 for each signal processing unit 10. In this embodiment, the load information is information indicating the number of connected user terminals performing wireless communication with the distributed antenna, the user throughput in the user terminal, the number of traffic buffers in the signal processing unit 10, or the call loss rate in the signal processing unit 10, but is not limited thereto.

[0022] The allocating unit 50 allocates the distributed antennas 30 to the signal processing units 10 so as to equalize the loads of the multiple signal processing units 10 based on the load information acquired by the acquiring unit 40. Specifically, the allocating unit 50 dynamically allocates to each signal processing unit 10 on a distributed antenna 30 basis based on the load information of each signal processing unit 10. When new allocation is performed, the newly allocated signal processing unit 10 takes over the allocated distributed antennas 30 and the users connected to the distributed antennas 30, thereby equalizing the loads of the signal processing units 10.

[0023] Fig. 3 is a flowchart showing the flow of processing of the CS 100. In Fig. 3, the allocation unit 50 performs initial allocation for allocating the distributed antennas 30 to be connected to the signal processing unit 10 (step S101). The allocation here may be according to a setting by a station operator, may be equal allocation, or may be based on the processing capacity of the signal processing unit 10.

[0024] The acquisition unit 40 determines whether an acquisition event has arrived (step S102). For example, when acquisition is performed at a predetermined time interval, the acquisition event may be the arrival of the time or an acquisition instruction from a higher-level device.

[0025] When an acquisition event arrives (step S102: YES), the acquisition unit 40 acquires the above-mentioned load information indicating the load of the signal processing unit 10 (step S103). The acquired load information is output to the allocation unit 50.

[0026] The allocation unit 50 determines whether or not to reallocate the distributed antennas 30 connected to the signal processing unit 10 based on the load information (step S104). Here, the allocation unit 50 may determine whether or not to perform reallocation processing by comparing with thresholds set for the number of connected user terminals, the user throughput, the number of traffic buffers, or the call loss rate. The allocation unit 50 may determine whether or not to perform reallocation processing based on the magnitude of the load imbalance of the signal processing unit 10. The allocation unit 50 may also detect a failure (such as a failure of a part of the distributed antenna 30 or the CS 100) and determine whether or not to perform reallocation processing based on the detection result.

[0027] As a result of the reallocation determination by the allocation unit 50, if it is not determined that the reallocation process is to be performed (step S105: NO), the allocation unit 50 returns to step S102 without performing the reallocation process. On the other hand, if it is determined that the reallocation process is to be performed (step S105: YES), the allocation unit 50 performs the reallocation process (step S106) and returns to step S102. In this reallocation, allocation is performed so as to equalize the loads on the multiple signal processing units 10.

[0028] Specifically, in the reallocation process of step S106, reallocation is performed in units of distributed antennas 30. For example, the reallocation process is performed to allocate the distributed antenna 30 with the highest load to the signal processing unit 10 with the lowest load. Alternatively, the reallocation process is performed to randomly select one of the distributed antennas 30 allocated to the signal processing unit 10 with the highest load, and allocate the selected distributed antenna 30 to the signal processing unit 10 with the lowest load. In this way, it becomes possible to follow fluctuations in the load.

[0029] In the above-mentioned flowchart, the load is leveled according to the result of comparison with the threshold. However, the load may be leveled by determining whether or not to perform the reallocation process when a predetermined trigger other than the acquisition event occurs, without comparing with the threshold. An example of the predetermined trigger is when the load of the signal processing unit 10 becomes more uneven (when the variance is greater than or equal to a predetermined value).

[0030] Furthermore, the load of the distributed antenna 30 varies depending on the day of the week and the time of day. Therefore, statistics showing the load of the distributed antenna 30 for each day of the week and time of day may be obtained in advance, and the connection destination of the distributed antenna 30 may be assigned in the reallocation process of step S106 based on the statistics. For example, if statistics showing that the number of UEs connected to a specific distributed antenna 30 increases around Sunday noon are obtained, the connection destination of the specific distributed antenna 30 may be assigned to a different signal processing unit 10 at the start of Sunday noon.

[0031] In the above-described embodiment, the switch 20 is provided outside the CS 100, but may be provided inside the CS 100. In addition, in the wireless communication system 1 in the embodiment, the analog RoF technology is used as the communication method between the distributed antenna 30 and the signal processing unit 10, but the digital RoF technology may be used instead of the analog RoF technology. This is because the process of leveling the loads of the multiple signal processing units does not depend on the communication method between the distributed antenna 30 and the signal processing unit 10.

[0032] (Modification) In the wireless communication system 1, the CS 100 is connected to the distributed antenna 30 via the switch 20, but a configuration using multiple CSs and switches may also be used. Fig. 7 shows a configuration example of a wireless communication system 1000 using multiple CSs and switches. The wireless communication system 1000 includes multiple (M: M is an integer equal to or greater than 2) CSs 100-1, 100-2, ..., 100-M.

[0033] The CSs 100-1, 100-2, ..., 100-M are connected to the distributed antenna 30 via the switch 200. In the wireless communication system 1000, the CSs 100-1, 100-2, ..., 100-M and the switch 200 are connected by one signal line, but this is just an example and they may be connected by multiple signal lines.

[0034] In the wireless communication system 1000, the CSs 100-1, 100-2, ..., 100-M each include one or more signal processing units, but may not include the acquisition unit and allocation unit described in FIG. 2, and the switch 200 may have functions corresponding to the acquisition unit and allocation unit. Alternatively, an operation system (OPS) may be provided above the CSs 100-1, 100-2, ..., 100-M, and functions corresponding to the acquisition unit, allocation unit, and setting unit may be realized in this OPS. Alternatively, the CSs 100-1, 100-2, ..., 100-M may exchange load information and allocation information with each other to realize functions corresponding to the acquisition unit and allocation unit. In the wireless communication system 1000, when the CSs 100-1, 100-2, ..., 100-M each include an acquisition unit and an allocation unit, each CS may function as an acquisition unit and an allocation unit for allocating to its own signal processing unit.

[0035] By applying this embodiment to the case of spanning a plurality of CSs in this way, it is possible to not only distribute the load information but also ensure redundancy in the event of a CS failure.

[0036] The acquisition unit 40 and the allocation unit 50 may be configured using a processor such as a CPU (Central Processing Unit) and a memory. In this case, the acquisition unit 40 and the allocation unit 50 function as the acquisition unit 40 and the allocation unit 50 by the processor executing a program. All or part of the functions of the acquisition unit 40 and the allocation unit 50 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. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a semiconductor storage device (for example, an SSD: Solid State Drive), or a storage device such as a hard disk or a semiconductor storage device built into a computer system. The above program may be transmitted via an electric communication line.

[0037] 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 designs that do not deviate from the gist of the present invention are also included. [Industrial Applicability]

[0038] The present invention is applicable to wireless communication systems in which the load fluctuates relatively greatly, such as when the number of user terminal connections changes significantly. [Explanation of symbols]

[0039] 1... wireless communication system, 10... signal processing unit, 20... switch, 30... distributed antenna, 40... acquisition unit, 50... allocation unit, 100... CS

Claims

1. A control method in a wireless communication system including a plurality of distributed antennas that perform wireless communication with a user terminal, and a plurality of signal processing units that are connected to the distributed antennas and perform signal processing, comprising: an initial allocation step of allocating the distributed antennas to be connected to the signal processing unit; acquiring load information indicating a load of the signal processing unit; a determination step of identifying a predetermined period among the plurality of periods, in which the statistics show a predetermined change, based on load statistics for each period corresponding to a day of the week or a time period acquired based on the load information acquired in the acquisition step, and determining whether or not to reallocate the distributed antennas to be connected to the signal processing unit based on whether or not the predetermined period has arrived; a reallocation step of performing reallocation and leveling the loads of the plurality of signal processing units when it is determined in the determination step that reallocation is to be performed; A control method comprising:

2. The control method according to claim 1 , wherein in the initial allocation step and the reallocation step, the signal processing unit to which the distributed antenna is connected is allocated using a switch that switches the connection destination of the distributed antenna.

3. 3. The control method according to claim 1, wherein the load information indicates a number of connected user terminals that perform wireless communication with the distributed antenna, a user throughput in a user terminal that performs wireless communication with the distributed antenna, a number of traffic buffers in the signal processing unit, or a call loss rate in the signal processing unit.

4. 2. The control method according to claim 1, wherein in the reallocation step, the signal processing units to which the distributed antennas are connected are allocated based on statistics indicating loads of the distributed antennas.

5. A wireless communication system comprising a plurality of distributed antennas that perform wireless communication with user terminals, and a plurality of signal processing units that are connected to the distributed antennas and perform signal processing, an initial allocation unit that allocates the distributed antennas to be connected to the signal processing unit; an acquisition unit that acquires load information indicating a load of the signal processing unit; a determination unit that identifies a predetermined period among a plurality of periods, based on load statistics for each period corresponding to a day of the week or a time period acquired based on the load information acquired by the acquisition unit, in which the statistics indicate a predetermined change, and determines whether or not to reallocate the distributed antennas to be connected to the signal processing unit based on whether the predetermined period has arrived; a reallocation unit that performs reallocation when the determination unit determines that reallocation should be performed, and equalizes loads on the plurality of signal processing units; A wireless communication system comprising:

Images