Communication device, wireless communication system, and wireless communication program

Abstract

The present disclosure relates to a communication device, a wireless communication system, and a wireless communication program. The communication device controls an AP, and is configured to perform a process for calculating a utility function for each combination of set values including a channel which can be assigned to the AP, and a process for selecting the optimal combination on the basis of the utility function. Selection is performed prioritizing a combination that is currently in use.

Description

Communication device, wireless communication system, and wireless communication program

[0001] The present disclosure relates to a communication device, a wireless communication system, and a wireless communication program.

[0002] 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 the wireless resources used by wireless LAN base stations (APs) (see, for example, Non-Patent Document 1).

[0003] In RATOP, a centralized control device grasps the state of mutual interference among the APs 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 wireless resource control method such as RATOP, parameter updates for APs within the system are assumed. However, if all APs update their parameters simultaneously, temporary communication interruptions associated with the parameter update process occur simultaneously in many wireless devices connected to each AP. This poses a problem of temporary significant degradation in communication quality throughout the system.

[0007] In order to solve the above-mentioned problems, a first object of the present disclosure is to provide a communication device that can prevent a temporary large decrease in communication quality of the entire system.

[0008] A second object of the present disclosure is to provide a wireless communication system that can prevent a temporary large decrease in communication quality of the entire system.

[0009] A third object of the present disclosure is to provide a wireless communication program that can prevent a temporary large decrease in communication quality of the entire system.

[0010] A first aspect of the present disclosure is a communication device that controls an AP, and is configured to perform a process of calculating a utility function for each combination of setting values ​​including channels that can be assigned to the AP, and a process of selecting an optimal combination based on the utility function, and the selection is preferably performed by giving priority to the combination currently in use.

[0011] Furthermore, a second aspect of the present disclosure is preferably a wireless communication system comprising an AP and a centralized control device that controls the AP, wherein the centralized control device is configured to perform a process of calculating a utility function for each combination of setting values ​​including channels that can be assigned to the AP, and a process of selecting an optimal combination based on the utility function, wherein the selection is performed by giving priority to the combination currently in use.

[0012] Furthermore, a third aspect of the present disclosure is a wireless communication program that has a processor and memory and is executed by a communication device that controls an AP, the program being stored in the memory and computer-readable, and including a program that causes the processor to perform a process of calculating a utility function for each combination of setting values ​​including channels that can be assigned to the AP, and a process of selecting an optimal combination based on the utility function, and the selection is preferably performed by giving priority to the combination currently in use.

[0013] According to the first to third aspects of the present disclosure, it is possible to prevent a temporary large decrease in communication quality of the entire system.

[0014] FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating a hardware configuration of a centralized control device according to the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating centralized control by the centralized control device according to the first embodiment of the present disclosure. FIG. 4 is a diagram illustrating a RATOP algorithm executed by the centralized control device according to the first embodiment of the present disclosure. FIG. 5 is a flowchart illustrating an operation example of a wireless communication system according to the first embodiment of the present disclosure. FIG. 6 is a diagram illustrating a RATOP algorithm executed by the centralized control device according to a second embodiment of the present disclosure. FIG. 7 is a diagram illustrating centralized control by the centralized control device according to a third embodiment of the present disclosure.

[0015] 1 is a diagram illustrating a configuration of a wireless communication system according to a first embodiment of the present disclosure. The wireless communication system 100 includes APs 2a to 2f. The dashed arrows indicate mutual interference between APs. For example, AP 2a interferes with APs 2b, 2c, and 2d. This mutual interference occurs, for example, when APs in close proximity share wireless communication resources.

[0016] The wireless communication system 100 also includes a centralized control device 4. The centralized control device 4 grasps the state of mutual interference between each AP and allocates wireless resources such as frequency channels and bandwidths to be used by each AP. This allocation is performed so as to maximize the throughput of the entire wireless communication system 100.

[0017] For example, AP 2a interferes with APs 2b, 2c, and 2d. Therefore, the centralized control device 4 allocates wireless resources so that APs 2a, 2b, 2c, and 2d use different channels for wireless communication. As a result, mutual interference between APs 2a to 2d is less likely to occur, and the throughput of the entire wireless communication system 100 is maximized.

[0018] Non-Patent Document 1 discloses RATOP technology targeted at APs in IEEE 802.11 wireless LANs. In a method using RATOP, if all APs simultaneously update their parameters, temporary communication interruptions associated with the parameter update process occur simultaneously in many wireless devices connected to each AP. This poses a problem of temporary significant degradation in communication quality throughout the system. The present disclosure solves this problem.

[0019] 2 is a diagram illustrating a hardware configuration of the centralized control device according to the first embodiment of the present disclosure. Each function of the centralized control device 4 may be partially or entirely configured by hardware such as a programmable logic device (PLD) or a field programmable gate array (FPGA), or may be configured as a program executed by a processor such as a CPU.

[0020] For example, the central control device 4 can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0021] 2, the centralized control device 4 has an input unit 40, an output unit 41, a communication unit 42, a CPU 43, a memory 44, and an HDD 45 connected via a bus 46, and functions as a computer. The centralized control device 4 is also capable of inputting and outputting data to and from a computer-readable storage medium 47.

[0022] The input unit 40 is, for example, a keyboard and a mouse, etc. The output unit 41 is, for example, a display device such as a display.

[0023] The communication unit 42 is, for example, a communication interface that communicates with a wireless device to be controlled.

[0024] The CPU 43 controls each component of the central control device 4 and performs predetermined processing, etc. The memory 44 and the HDD 45 store data, etc.

[0025] The storage medium 47 is capable of storing programs and the like that cause the central control device 4 to execute the functions of the central control device 4. Note that the architecture that constitutes the central control device 4 is not limited to the example shown in FIG.

[0026] 3 is a diagram illustrating centralized control by a centralized control device according to the first embodiment of the present disclosure. The wireless communication system of this embodiment includes, for example, a plurality of APs connected to a network 8, a centralized control device 4, and a plurality of wireless terminals 6. Each AP is centrally controlled by the centralized control device 4 to accommodate a plurality of wireless terminals 6.

[0027] The centralized control device 4 controls RATOP for a plurality of APs 2. At this time, the control index is the utility function U (corresponding to the degree of satisfaction) shown in Equation 1.

[0028] a: AP identifier b: Bandwidth c: Channel (primary channel) R: Data rate (MCS)

[0029] The transmittable traffic volume of AP(a) is the expected throughput of AP(a) and depends on the channel usage status of other APs, etc. The expected throughput of each AP is derived from the positional relationship between APs using the same frequency channel. This positional relationship is estimated using, for example, RSSI. For example, if APs in interfering positions use the same frequency channel, it can be estimated that the throughput will decrease.

[0030] The accommodated traffic volume (which depends on the amount of generated data) is set to the maximum traffic estimate value of AP(a) shown in Equation 2, for example.

[0031]

[0032] In this case, it is assumed that the maximum traffic estimated value is the accommodated traffic volume per wireless terminal multiplied by the expected number of wireless terminals. Then, the centralized control device 4 performs processing to maximize the sum ΣU of the utility functions U according to the following algorithm.

[0033] RATOP algorithm: (A): The centralized control device 4 "provisionally allocates" the channels and bandwidths used by each AP according to predetermined rules. (B): The centralized control device 4 calculates the sum ΣU of the utility functions U of each AP in the case of (A) above. (C): The centralized control device 4 reallocates channels and bandwidths to APs with low utility functions U, and controls so that ΣU does not decrease. The centralized control device 4 then repeats (C) within the range of predetermined conditions.

[0034] 4 is a diagram illustrating the RATOP algorithm executed by the centralized control device according to the first embodiment of the present disclosure. As shown in FIG. 4, the centralized control device 4 performs processes of Phase I (initial calculation) and Phase II (optimization).

[0035] In Phase I, the centralized control device 4 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).

[0036] The centralized control device 4 then executes the processes of S104 and S106 for all channels c, and then repeats the processes for all bandwidths b. That is, the centralized control device 4 calculates the utility function U for each combination of bandwidth b and channel c that can be assigned to the selected AP. Note that, although the following examples will describe combinations of bandwidth and channel, the process is not limited to these combinations, and may also be performed for combinations of setting values ​​that include channels.

[0037] Next, the centralized control device 4 selects a combination of (b, c) based on the utility function U (S108) and repeats the process for all APs. Specifically, if there are multiple options for the combination of (b, c) that satisfy certain conditions for the utility function U, it checks whether the combination of (b, c) currently in use is included among them. If there is a combination of (b, c) currently in use, that combination is given priority.

[0038] The certain condition that the utility function U satisfies may be that it is the maximum value, or that the difference between the utility function U and the maximum value is equal to or less than a specific threshold value.

[0039] Furthermore, if there is an AP that has been continuously used for a certain period of time or more for a combination of (b, c) currently in use, for which the utility function U satisfies certain conditions, that AP may be excluded from the targets for control. This exclusion process can reduce the time and resources required to determine (b, c).

[0040] In Phase II, the centralized control device 4 optimizes the utility function U (S110). For example, the centralized control device 4 selects the AP with the smallest utility function U, and calculates the utility function for each combination of (b, c) that can be assigned to the selected AP when the degradation of the sum ΣU of the utility functions U is within a certain range. Note that "within a certain range" may include cases where the degradation is a negative value, i.e., improvement. The centralized control device 4 then selects a combination of (b, c) based on the calculated utility function, and repeats the process for all APs. More specifically, if there are multiple options for combinations of (b, c) whose utility function U satisfies certain conditions, it checks whether any of the combinations (b, c) are currently in use. If any combination of (b, c) is currently in use, that combination is prioritized.

[0041] The certain condition that the utility function U satisfies may be that it is the maximum value, or that the difference between the utility function U and the maximum value is equal to or less than a specific threshold value.

[0042] Then, the central control device 4 determines the combination of (b, c) selected by each AP as the bandwidth and channel after allocation (S112).

[0043] 5 is a flowchart showing an example of operation of the wireless communication system according to the first embodiment of the present disclosure. First, in step 100, the central control device 4 determines whether it is time to collect information from each AP and each wireless terminal. The time to collect information occurs, for example, at a regular interval. If it is time to collect information, the process proceeds to step 102. If it is not time to collect information, the process of step 100 is repeated.

[0044] In step 102, the centralized control device 4 collects information from each AP and each wireless terminal. Next, in step 104, the centralized control device 4 determines whether the parameters of each AP should be updated based on the collected information. If they should be updated, the process proceeds to step 106. If they should not be updated, the process returns to step 100.

[0045] In step 106, the centralized control device 4 instructs each AP to update its parameters, and the process returns to step 100. More specifically, the centralized control device 4 first determines the contents of the wireless resources to be allocated to each AP based on the collected information. The centralized control device 4 then transmits the parameters derived for using the allocated wireless resources to each AP as an update instruction. This embodiment solves the problem by preferentially selecting wireless resources currently in use when allocating wireless resources.

[0046] As described above, the wireless communication system of this embodiment can reduce the number of APs that experience communication interruptions by preferentially selecting wireless resources that are currently in use, thereby preventing a temporary significant degradation in communication quality of the entire system.

[0047] 6 is a diagram showing a RATOP algorithm executed by a centralized control device according to a second embodiment of the present disclosure. This embodiment differs from the first embodiment in that a utility function U′ obtained by multiplying the utility function U by a coefficient is used when selecting a channel and bandwidth to be used by each AP.

[0048] The RATOP algorithm executed by the central control device 4 of this embodiment will be described below. Note that a description of steps that perform the same processing as in FIG. 4 will be omitted.

[0049] In Phase I, the central control device 4 calculates the utility function U' of AP-a (S206). The utility function U' is a function obtained by multiplying the utility function U by a coefficient, as shown in Equation 3.

[0050] a: AP identifier b: Bandwidth c: Channel (primary channel) R: Data rate (MCS) A: Coefficient

[0051] This coefficient A is a value greater than 1 if (b, c) is a combination currently in use, and is 1 if it is not a combination currently in use. In other words, if the combination (b, c) is currently in use, the value of the utility function U' is made larger, so that the corresponding (b, c) can be selected with priority.

[0052] Furthermore, if the selected AP-a is a high-priority AP, the coefficient A may be set to be larger than that of an AP with a lower priority. An AP with a higher priority is, for example, an AP with a larger number of associated terminals, a larger amount of communication, or a high real-time nature. This process allows the AP with a higher priority to be selected preferentially.

[0053] In Phase II, the centralized control device 4 optimizes the utility function U' (S210). For example, the centralized control device 4 selects the AP with the smallest utility function U' and calculates the utility function for each combination of (b, c) that can be assigned to the selected AP, provided that the degradation of the sum ΣU of the utility functions U is within a certain range. Then, the centralized control device 4 selects a combination of (b, c) based on the calculated utility function, and repeats the process for all APs. More specifically, if there are multiple options for the combination of (b, c) whose utility function U' satisfies certain conditions, the centralized control device 4 checks whether any of the combinations of (b, c) are currently in use. If any combination of (b, c) is currently in use, the centralized control device 4 prioritizes that combination.

[0054] As described above, the wireless communication system of this embodiment can reduce the number of APs that experience communication interruptions by preferentially selecting wireless resources that are currently in use, thereby preventing a temporary significant degradation in communication quality of the entire system.

[0055] 7 is a diagram illustrating centralized control by a centralized control device according to a third embodiment of the present disclosure. This embodiment differs from the first and second embodiments in that the setting values ​​related to RATOP implemented by the centralized control device 4 can be changed externally.

[0056] The wireless communication system according to this embodiment includes a setting device 10. The setting device 10 is an operation terminal having a setting screen. A user can access the central control device 4 via the setting device 10 to change setting values ​​related to RATOP executed by the central control device 4.

[0057] The setting value for RATOP may be a certain condition satisfied by the utility function U, or may be a coefficient A included in the utility function U'. The user may change the setting value directly via the setting screen, or may change the setting value by changing the setting file to be read into the setting device 10.

[0058] Furthermore, the user may be able to change the RATOP algorithm executed by the centralized control device 4 by accessing the centralized control device 4 via the setting device 10. For example, the user may be able to switch between executing the algorithm according to the first embodiment and the algorithm according to the second embodiment.

[0059] 2 AP 2a AP 2b AP 2c AP 2d AP 2e AP 2f AP 4 Centralized control device 44 Memory 100 Wireless communication system

Claims

1. A communication device for controlling an AP, configured to perform a process of calculating a utility function for each combination of set values including channels assignable to the AP, and a process of selecting an optimal combination based on the utility function, wherein the selection is performed by giving priority to the currently used combination.

2. The communication device according to claim 1, which controls a plurality of APs.

3. The communication device according to claim 2, further configured to perform a process of selecting an AP with the smallest utility function from the plurality of APs, a process of calculating a utility function for each combination of set values including channels assignable to the AP while the deterioration of the total utility function in all the plurality of APs is within a certain range, and a process of selecting an optimal combination based on the utility function.

4. The communication device according to claim 1, wherein giving priority to the currently used combination is realized by multiplying a coefficient to the utility function.

5. The communication device according to claim 1, wherein the selection is made from a combination that maximizes the utility function or a combination whose difference from the utility function that maximizes is less than or equal to a specific threshold.

6. The communication device according to claim 1, wherein when there is an AP selected for a time equal to or longer than a specific threshold, the AP is excluded from the control target.

7. A wireless communication system including an AP and a centralized control device for controlling the AP, wherein the centralized control device is configured to perform a process of calculating a utility function for each combination of set values including channels assignable to the AP, and a process of selecting an optimal combination based on the utility function, and the selection is performed by giving priority to the currently used combination.

8. A wireless communication program including a processor and a memory, for causing a communication device for controlling an AP to execute, the program being stored in the memory, being computer-readable, and including a program for causing the processor to perform a process of calculating a utility function for each combination of set values including channels assignable to the AP, and a process of selecting an optimal combination based on the utility function, wherein the selection is performed by giving priority to the currently used combination.

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