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

Abstract

In a radio communication system according to one embodiment, when a maintenance device detects that one or more base stations have changed a state exceeding a prescribed condition, a centralized control device: calculates, as a utility function, the ratio of an estimated value of a transmittable traffic amount based on a channel and a bandwidth allocated to the base stations to an estimated value of a maximum traffic amount of the base stations detected by the maintenance device when the state change exceeding the prescribed condition is carried out; and performs control for changing the channel and the bandwidth of each of the base stations detected by the maintenance device when the state change exceeding the prescribed condition is carried out so as to increase the total value of each calculated utility function.

Description

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

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

[0002] For example, RATOP (Resource allocation based on Area Throughput Optimization Policy) is known as a method for maximizing the effective capacity of the entire system by centrally controlling wireless resources such as frequency bandwidths and channels used by wireless LAN base stations (APs) (see, for example, Non-Patent Document 1).

[0003] In RATOP, a centralized control device grasps the status of each AP and allocates wireless resources such as frequency channels and bandwidths to be used by each AP.

[0004] For example, in RATOP, the evaluation index for wireless resource allocation is defined as the ratio (utility function) of the estimated amount of traffic that can be transmitted (transmittable traffic volume) based on the allocated wireless resources (channels and bandwidth) to the estimated value of the maximum traffic volume (accommodated traffic volume) of each AP.The centralized control device then performs control so as to maximize the total value of the utility function.

[0005] BAHirantha Sithira Abeysekera et al., "Network Controlled Frequency Channel and Bandwidth Allocation Scheme for IEEE 802.11a / n / ac Wireless LANs: RATOP", 2014 IEEE 25th International Symposium on Personal, Indoor and Mobile Radio Communications, pp.1041-1045

[0006] In a centralized control method for wireless resources such as RATOP, it is assumed that parameters of base stations (APs) in the entire system are updated. Therefore, if parameters of all base stations are updated when a change in radio wave conditions occurs in only some base stations in the system, it is possible that unnecessary processing or communication interruptions will occur.

[0007] The present invention aims to provide a wireless communication system, a centralized control device, a wireless communication method, and a centralized control program that can efficiently increase the effective capacity of the entire system when a state change occurs in only some of the base stations in the system.

[0008] A wireless communication system according to one embodiment of the present invention has a plurality of base stations accommodating wireless terminals, a maintenance device that detects whether one or more of the base stations have undergone a state change that exceeds a predetermined condition, and a centralized control device that centrally controls each of the base stations, wherein the centralized control device is characterized by having a utility function calculation unit that, when the maintenance device detects that one or more of the base stations have undergone a state change that exceeds a predetermined condition, calculates, as a utility function, the ratio of an estimated value of transmittable traffic volume based on the channel and bandwidth assigned to the base station to an estimated value of maximum traffic volume of the base station detected by the maintenance device as having undergone a state change that exceeds a predetermined condition, and a change control unit that controls changing the channel and bandwidth of each of the base stations detected by the maintenance device as having undergone a state change that exceeds a predetermined condition so as to increase the total value of each utility function calculated by the utility function calculation unit.

[0009] Furthermore, a centralized control device according to one embodiment of the present invention is characterized in that, in the centralized control device which centrally controls each of a plurality of base stations which accommodate wireless terminals, when a maintenance device detects that one or more of the base stations have undergone a state change exceeding a predetermined condition, the centralized control device has a utility function calculation unit which calculates, as a utility function, the ratio of an estimated value of the transmittable traffic volume based on the channel and bandwidth assigned to the base station to an estimated value of the maximum traffic volume of the base station which the maintenance device has detected as having undergone a state change exceeding a predetermined condition, and a change control unit which controls to change the channel and bandwidth of each of the base stations which the maintenance device has detected as having undergone a state change exceeding a predetermined condition so as to increase the total value of each of the utility functions calculated by the utility function calculation unit.

[0010] Furthermore, a wireless communication method according to one embodiment of the present invention is a wireless communication method in which a centralized control device centrally controls each of a plurality of base stations that accommodate wireless terminals, and is characterized in that it includes a utility function calculation step of, when a maintenance device detects that one or more of the base stations has undergone a state change that exceeds a predetermined condition, calculating, as a utility function, the ratio of an estimated value of the transmittable traffic volume based on the channel and bandwidth assigned to the base station to an estimated value of the maximum traffic volume of the base station detected by the maintenance device to have undergone a state change that exceeds a predetermined condition, and a change control step of controlling to change the channel and bandwidth of each of the base stations detected by the maintenance device to have undergone a state change that exceeds a predetermined condition so as to increase the total value of each utility function calculated in the utility function calculation step.

[0011] According to the present invention, when a state change occurs in only some base stations in the system, it is possible to efficiently increase the effective capacity of the entire system.

[0012] FIG. 1 is a diagram illustrating an overview of a wireless communication system. FIG. 2 is a diagram illustrating a specific example of a RATOP algorithm executed by a centralized control device. FIG. 3 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment. FIG. 4 is a functional block diagram illustrating functions possessed by a centralized control device according to an embodiment. FIG. 5 is a diagram illustrating a first example of a specific operation of a wireless communication system according to an embodiment. FIG. 6 is a diagram illustrating a second example of a specific operation of a wireless communication system according to an embodiment. FIG. 7 is a diagram illustrating a third example of a specific operation of a wireless communication system according to an embodiment. FIG. 8 is a flowchart illustrating an example of an operation of a wireless communication system according to an embodiment.

[0013] An overview of a wireless communication system will be described below with reference to the drawings. Fig. 1 is a diagram showing an overview of a wireless communication system 1. As shown in Fig. 1, the wireless communication system 1 has, for example, a plurality of base stations (APs) 2, a centralized control device 3, and a plurality of wireless terminals 10 connected to a network 100. Each of the base stations 2 is centrally controlled by the centralized control device 3, and thereby accommodates a plurality of wireless terminals 10. Hereinafter, the base stations may be referred to as APs.

[0014] The centralized control device 3 controls RATOP for a plurality of base stations 2. At this time, the control index is assumed to be a utility function U (corresponding to satisfaction level) shown in the following equation (1).

[0015] a: AP identifier b: Bandwidth c: Channel (primary channel) R: Data rate (MCS)

[0016] The traffic volume that AP(a) can transmit depends on the channel usage status of other APs, etc. The accommodating traffic volume (which depends on the amount of generated data) is set to the maximum traffic estimate value of AP(a) shown in the following formula (2), for example.

[0017]

[0018] In this case, the maximum traffic estimated value may be assumed to be the accommodated traffic volume per wireless terminal multiplied by the expected number of wireless terminals.The centralized control device 3 then performs processing to maximize the sum ΣU of the utility functions U according to the following algorithm.

[0019] RATOP algorithm: (A): The centralized control device 3 "provisionally allocates" the channels and bandwidths used by each AP according to predetermined rules. (B): The centralized control device 3 calculates the sum ΣU of the utility functions U of each AP in the case of (A) above. (C): The centralized control device 3 reallocates channels and bandwidths to APs with low utility functions U, and controls so that ΣU does not decrease. The centralized control device 3 then repeats (C) within the range of predetermined conditions.

[0020] Fig. 2 is a diagram showing a specific example of the RATOP algorithm executed by the centralized control device 3. As shown in Fig. 2, the centralized control device 3 performs processing in Phase I (initial calculation) and Phase II (optimization).

[0021] In Phase I, the centralized control device 3 selects one AP as AP-a (S100), selects a bandwidth b that can be allocated to AP-a (S102), selects a channel (primary channel) c that can be allocated to AP-a (S104), and calculates the utility function U of AP-a (S106).

[0022] Then, the central control device 3 executes the process of S104 and the process of S106 for all channels c, and further repeats the process for all bandwidths b.

[0023] Next, the central control device 3 selects the combination (b, c) that maximizes the utility function U (S108), and repeats the process for all APs.

[0024] In Phase II, the centralized control device 3 selects, for example, an AP with a small utility function U, and then repeats the process of selecting a combination (parameters) of (b, c) that maximizes the utility function U and does not degrade the sum ΣU of the utility functions U (S110).

[0025] Then, the central control device 3 sets the combination of (b, c) selected by each AP as the allocated bandwidth and channel after control (S112).

[0026] 3 is a diagram showing an example of the configuration of a wireless communication system 1a according to an embodiment that utilizes the above-described algorithm more efficiently. As shown in FIG. 3, the wireless communication system 1a according to the embodiment includes, for example, base stations 2-1 to 2-6, a central control device 3, and maintenance devices 4-1 to 4-4, which are connected to each other via a network 100.

[0027] Each of the base stations 2-1 to 2-6 accommodates a wireless terminal (not shown). The centralized control device 3 performs centralized control of each of the base stations 2-1 to 2-6. The maintenance devices 4-1 to 4-4 respectively detect whether one or more of the base stations 2-1 to 2-6 has experienced a change in status exceeding a predetermined condition, and transmit the detection result to the centralized control device 3.

[0028] Here, the state change is assumed to be, for example, a change in throughput, etc. For example, a state change that exceeds a predetermined condition includes a change in throughput that falls below a predetermined threshold.

[0029] Also, suppose that, for example, interfering base stations 2-X and 2-Y having the same functions as the base stations 2-1 to 2-6 are located around the wireless communication system 1a. Here, the interfering base stations 2-X and 2-Y are not subject to centralized control by the centralized control device 3, and can be sources of radio wave interference for the base stations 2-1 to 2-6. In other words, the centralized control device 3 treats the base stations 2-1 to 2-6 as base stations to be managed, and treats the interfering base stations 2-X and 2-Y as base stations not to be managed.

[0030] Next, the centralized control device 3 according to one embodiment will be described in detail. When there is no need to specify one of the multiple configurations, such as base stations 2-1 to 2-6, it will be simply abbreviated as base station 2. Furthermore, in the wireless communication system 1a, the number of base stations 2 and maintenance devices 4 is not limited and can be any number.

[0031] 4 is a functional block diagram illustrating functions of the centralized control device 3 according to one embodiment. As shown in FIG. 4, the centralized control device 3 includes, for example, an NW interface unit 31, a collection unit 32, a utility function calculation unit 33, a change control unit 34, and a main control unit 35.

[0032] The NW interface unit 31 transmits and receives control information to and from each base station 2 .

[0033] The collection unit 32 collects information about each base station 2 via the NW interface unit 31 and outputs the information to the utility function calculation unit 33. For example, the collection unit 32 collects information about the location of the base station 2, the number of wireless terminals connected to each base station 2, traffic (uplink / downlink ratio, etc.), etc.

[0034] When the maintenance device 4 detects that one or more base stations 2 have undergone a state change exceeding a predetermined condition, the utility function calculation unit 33 calculates, as a utility function, the ratio of the estimated value of the maximum traffic volume of the base station 2 that the maintenance device 4 has detected as having undergone a state change exceeding the predetermined condition to the estimated value of the transmittable traffic volume based on the channel and bandwidth assigned to that base station 2.

[0035] Furthermore, for other base stations (including other base stations 2 and interfering base stations 2-X and 2-Y) whose radio waves interfere with the base station 2 that the maintenance device 4 has detected as having undergone a state change exceeding a predetermined condition, the utility function calculation unit 33 calculates the ratio of the estimated value of the transmittable traffic volume based on the channel and bandwidth assigned to the other base station to the estimated value of the maximum traffic volume of the other base station as a utility function.

[0036] In addition, for other base stations 2 that are within a predetermined number of hops from the base station 2 that the maintenance device 4 has detected as having undergone a state change exceeding a predetermined condition, the utility function calculation unit 33 may also calculate, as a utility function, the ratio of the estimated value of the transmittable traffic volume based on the channel and bandwidth assigned to the other base station to the estimated value of the maximum traffic volume of the other base station.

[0037] Furthermore, the utility function calculation unit 33 also has a function of excluding, in advance, base stations 2 that are preset not to cause communication interruptions from the calculation of the utility function. For example, the utility function calculation unit 33 excludes, in advance, some of the base stations designated in advance from the calculation of the utility function so as not to update the channel and bandwidth.

[0038] Then, the utility function calculation unit 33 outputs the calculated utility function to the change control unit 34 .

[0039] The change control unit 34 controls the change of the channel and bandwidth of each base station 2 that the maintenance device 4 detects as having undergone a state change exceeding specified conditions, so as to increase the total value of each utility function calculated by the utility function calculation unit 33.

[0040] The main control unit 35 controls each unit constituting the central control device 3 .

[0041] Next, a specific example of the operation of the wireless communication system 1a will be described.

[0042] 5 is a diagram showing a first example of the specific operation of the wireless communication system 1a. As shown by the dashed double-headed arrows, for example, a base station 2 may experience radio wave interference with another base station 2. Furthermore, as shown by the dashed arrows, an interfering base station 2-X or 2-Y may cause radio wave interference with the base station 2.

[0043] In the wireless communication system 1a, the centralized control device 3 calculates the expected throughput of each of the base stations 2-1 to 2-6 based on the positional relationship between the base stations using the same frequency channel. For example, the centralized control device 3 calculates the positional relationship between the base stations based on the magnitude of the RSSI (Received Signal Strength Indicator) or whether or not a received signal is detected.

[0044] For example, if an interfering base station 2-X uses the same frequency channel as base station 2-1, the throughput of base station 2-1 will be reduced.

[0045] The maintenance device 4 receives radio waves transmitted from the surrounding base stations 2 and detects abnormalities and status changes in the base stations 2. If a status change occurs in the base station 2, the wireless communication system 1a efficiently uses the RATOP algorithm to update the settings of wireless resources.

[0046] Specifically, when the maintenance device 4 detects that an abnormality or change in status has occurred in a base station 2, the centralized control device 3 applies the RATOP algorithm to only the base station 2 in which the abnormality or change in status has occurred (updates parameters) based on the detection results received from the maintenance device 4.

[0047] For example, as shown in FIG. 5, when the maintenance device 4 detects that an abnormality or a change in status has occurred in the base stations 2-3 and 2-6, the central control device 3 applies the RATOP algorithm to only the base stations 2-3 and 2-6.

[0048] 6 is a diagram illustrating a second example of the specific operation of the wireless communication system 1a according to an embodiment. For example, as indicated by the dashed double-headed arrows, a base station 2 may experience radio wave interference with another base station 2. Furthermore, for example, as indicated by the dashed arrows, an interfering base station 2-X or 2-Y may cause radio wave interference with the base station 2.

[0049] In a second example of the operation of the wireless communication system 1a, when the maintenance device 4 detects that an abnormality or change in status has occurred in a base station 2, the centralized control device 3, based on the detection results received from the maintenance device 4, applies the RATOP algorithm to control not only the base station 2 in which the abnormality or change in status has occurred, but also other base stations 2 that are subject to radio wave interference from the base station 2.

[0050] The base station 2 that receives radio wave interference from another base station 2 is determined by referring to, for example, the RSSI value.

[0051] For example, as shown in Figure 6, if the maintenance device 4 detects that an abnormality or status change has occurred in base stations 2-3 and 2-6, the centralized control device 3 applies the RATOP algorithm to control base stations 2-2 and 2-5 in addition to base stations 2-3 and 2-6.

[0052] 7 is a diagram illustrating a third example of the specific operation of the wireless communication system 1a according to an embodiment. For example, as indicated by the dashed double-headed arrows, a base station 2 may experience radio wave interference with another base station 2. Furthermore, for example, as indicated by the dashed arrows, an interfering base station 2-X or 2-Y may cause radio wave interference with the base station 2.

[0053] In a third example of the operation of the wireless communication system 1a, when the maintenance device 4 detects that an abnormality or change in status has occurred in a base station 2, the centralized control device 3, based on the detection result received from the maintenance device 4, applies the RATOP algorithm to control (update parameters) not only the base station 2 where the abnormality or change in status has occurred, but also other base stations 2 that are the nth hop (for example, the number of hops is 2) from the base station 2.

[0054] Furthermore, the wireless communication system 1a divides the base stations 2-1 to 2-6 into multiple clusters, and applies the RATOP algorithm to only the base stations 2 in the same cluster as the base station 2 in which the maintenance device 4 detects an abnormality or a change in status. The cluster may be changed according to fluctuations in the mutual RSSI values ​​of the base stations 2.

[0055] For example, in the case where the wireless communication system 1a applies the RATOP algorithm to the base station 2 at the second hop (n=2), when the maintenance device 4 detects an abnormality or change in status at the base station 2-3 as shown in FIG. 7, the centralized control device 3 applies the RATOP algorithm to the base stations 2-2 and 2-6 (one hop) and the base stations 2-1 and 2-5 (two hops) in addition to the base station 2-3 (target base station).

[0056] 8 is a diagram illustrating a fourth example of the specific operation of the wireless communication system 1a according to an embodiment. For example, as indicated by the dashed double-headed arrows, a base station 2 may experience radio wave interference with another base station 2. Furthermore, for example, as indicated by the dashed arrows, an interfering base station 2-X or 2-Y may cause radio wave interference with the base station 2.

[0057] In the fourth example of the operation of the wireless communication system 1a, for example, the centralized control device 3 assumes that in addition to base station 2-3 (target base station), base stations 2-2 and 2-6 (one hop) and base stations 2-1 and 2-5 (two hops) are to be controlled, as in the third example of the operation of the wireless communication system 1a.

[0058] However, in the fourth example of the operation of the wireless communication system 1a, the base station 2-2 is a base station that is preset not to cause communication interruptions. That is, in the fourth example of the operation of the wireless communication system 1a, the base station 2-2 is excluded in advance from the base stations 2-3, 2-2, 2-6, 2-1, and 2-5 that are assumed to be the base stations to be controlled, from the base stations to be calculated for the utility function.

[0059] Furthermore, in the fourth example of the operation of the wireless communication system 1a, among the base stations 2-3, 2-6, 2-1, and 2-5, the base station 2-1 (the next hop of the base station 2-2) that receives interference only from the excluded base station 2-2 is also excluded in advance from the calculation of the utility function.

[0060] In a fourth example of the operation of the wireless communication system 1a, the centralized control device 3 applies the RATOP algorithm to base station 2-6 (one hop) and base station 2-5 (two hops) in addition to base station 2-3 (target base station).

[0061] 9 is a flowchart showing an example of operation of the wireless communication system 1a according to one embodiment. As shown in FIG. 9, in the wireless communication system 1a, the centralized control device 3 determines whether or not a notification indicating that an abnormality or a state change has occurred in the base station 2 has been received from the maintenance device 4 (S200). If a notification has been received from the maintenance device 4 (S200: Yes), the centralized control device 3 proceeds to processing of S202. If no notification has been received from the maintenance device 4 (S200: No), the centralized control device 3 continues processing of S200.

[0062] In the process of S202, the central control device 3 controls the base station 2 that is the target of control (parameter update) to which the RATOP algorithm is applied.

[0063] In this way, the wireless communication system 1a in one embodiment calculates a utility function for a base station 2 that the maintenance device 4 detects has undergone a state change exceeding a specified condition, and controls the channel and bandwidth of each base station 2 that the maintenance device 4 detects has undergone a state change exceeding a specified condition so as to increase the total value of each utility function.Therefore, when a state change occurs in only some of the base stations in the system, the effective capacity of the entire system can be efficiently increased.

[0064] In addition, each function of the centralized control device 3 may be configured in part or in whole by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

[0065] For example, the central control device 3 can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0066] 10 is a diagram illustrating an example of a hardware configuration of a centralized control device 3 according to one embodiment. As shown in FIG. 10, the centralized control device 3 has an input unit 50, an output unit 51, a communication unit 52, a CPU 53, a memory 54, and an HDD 55 connected via a bus 56, and functions as a computer. The centralized control device 3 is also capable of inputting and outputting data to and from a computer-readable storage medium 57.

[0067] The input unit 50 is, for example, a keyboard and a mouse, etc. The output unit 51 is, for example, a display device such as a display.

[0068] The communication unit 52 is a communication interface that communicates with, for example, the base station 2 to be controlled and the maintenance device 4 .

[0069] The CPU 53 controls each component of the central control device 3 and performs predetermined processing, etc. The memory 54 and HDD 55 store data, etc.

[0070] The storage medium 57 is capable of storing programs and the like that cause the central control device 3 to execute the functions of the central control device 3. The architecture that configures the central control device 3 is not limited to the example shown in FIG.

[0071] 1, 1a... wireless communication system, 2, 2-1 to 2-6... base stations, 2-X, 2-Y... interfering base stations, 3... centralized control device, maintenance devices 4-1 to 4-4, 10... wireless terminal, 31... network interface unit, 32... collection unit, 33... utility function calculation unit, 34... change control unit, 35... main control unit, 50... input unit, 51... output unit, 52... communication unit, 53... CPU, 54... memory, 55... HDD, 56... bus, 57... storage medium, 100... network

Claims

1. A wireless communication system having a plurality of base stations accommodating wireless terminals, a maintenance device which detects whether one or more of the base stations have undergone a state change exceeding a predetermined condition, and a centralized control device which centrally controls each of the base stations, wherein the centralized control device has: a utility function calculation unit which, when the maintenance device detects that one or more of the base stations have undergone a state change exceeding a predetermined condition, calculates, as a utility function, the ratio of an estimated value of transmittable traffic volume based on the channel and bandwidth assigned to the base station to an estimated value of maximum traffic volume of the base station detected by the maintenance device as having undergone a state change exceeding a predetermined condition; and a change control unit which controls the change of the channel and bandwidth of each of the base stations detected by the maintenance device as having undergone a state change exceeding a predetermined condition so as to increase the total value of each utility function calculated by the utility function calculation unit.

2. The wireless communication system according to claim 1, characterized in that the utility function calculation unit calculates, as a utility function, the ratio of an estimated value of transmittable traffic volume based on the channel and bandwidth assigned to the other base station to an estimated value of maximum traffic volume of the other base station, for each of the other base stations whose radio waves interfere with the base station detected by the maintenance device as having undergone a state change exceeding a predetermined condition.

3. The wireless communication system according to claim 1, characterized in that the utility function calculation unit calculates, as a utility function, the ratio of an estimated value of transmittable traffic volume based on the channel and bandwidth assigned to the other base station to an estimated value of maximum traffic volume of the other base station, for the other base station that is within a predetermined hop count of the base station detected by the maintenance device as having undergone a state change exceeding a predetermined condition.

4. The wireless communication system according to any one of claims 1 to 3, wherein the utility function calculation unit preliminarily excludes a preliminarily designated portion of the base stations from the calculation of the utility function so as not to update the channel and bandwidth for the preliminarily designated portion of the base stations.

5. A centralized control device that centrally controls each of a number of base stations that accommodate wireless terminals, comprising: a utility function calculation unit that, when a maintenance device detects that one or more of the base stations have undergone a state change that exceeds a predetermined condition, calculates, as a utility function, the ratio of an estimated value of transmittable traffic volume based on the channel and bandwidth assigned to the base station to an estimated value of maximum traffic volume of the base station detected by the maintenance device as having undergone a state change that exceeds a predetermined condition; and a change control unit that performs control to change the channel and bandwidth of each of the base stations detected by the maintenance device as having undergone a state change that exceeds a predetermined condition so as to increase the total value of each utility function calculated by the utility function calculation unit.

6. The centralized control device according to claim 5, characterized in that the utility function calculation unit calculates, as a utility function, the ratio of an estimated value of transmittable traffic volume based on the channel and bandwidth assigned to the other base station to an estimated value of maximum traffic volume of the other base station, for each of the other base stations whose radio waves interfere with the base station detected by the maintenance device as having undergone a state change exceeding a predetermined condition.

7. A wireless communication method in which a centralized control device centrally controls each of a plurality of base stations accommodating wireless terminals, comprising: a utility function calculation step, when a maintenance device detects that one or more of the base stations have undergone a state change exceeding a predetermined condition, for calculating, as a utility function, the ratio of an estimated value of transmittable traffic volume based on the channel and bandwidth assigned to the base station to an estimated value of maximum traffic volume of the base station detected by the maintenance device as having undergone a state change exceeding a predetermined condition; and a change control step, for controlling the change of the channel and bandwidth of each of the base stations detected by the maintenance device as having undergone a state change exceeding a predetermined condition so as to increase the total value of each utility function calculated by the utility function calculation step.

8. A centralized control program for causing a computer to function as each part of the centralized control device according to claim 5 or 6.

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