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

Abstract

A wireless communication system according to one embodiment of the present invention comprises a plurality of base stations that perform wireless communication with a wireless terminal and a centralized control device that applies centralized control to each of the base stations and relay devices. The centralized control device performs control of: calculating, for each of the plurality of base stations and a plurality of relay devices, a ratio of a transmittable traffic amount based on an allocated channel and a bandwidth to an accommodated traffic amount as a utility function; setting, on the basis of the calculated utility functions, a value corresponding to the transmittable traffic amount of a higher-level device in a relay configuration as an accommodated traffic amount for a lower-level device; and changing the channel and the bandwidth of each of the plurality of base stations and the plurality of relay devices so as to maximize the sum of the utility functions calculated after the accommodated traffic amount is set.

Description

[[Technical Field]]

[0001] The present invention relates to a wireless communication system, a centralized control apparatus, a centralized control method and a centralized control program. [[Background Art]]

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

[0003] In RATOP, a centralized control apparatus grasps the state of each AP and allocates radio resources such as frequency channels and bandwidth to be used by each AP.

[0004] For example, in RATOP, as an evaluation index for radio resource allocation, the ratio (utility function) of an estimated transmittable traffic volume (transmittable traffic volume) based on allocated radio resources (channel / bandwidth) to an estimated maximum traffic volume (accommodated traffic volume) of each AP is defined. Then, the centralized control apparatus performs control to maximize the total value of the utility function. [[Prior Art Documents]] [[Non-Patent Documents]]

[0005] [[Non-Patent Document 1]] 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 [Overview of the initiative] [Problems that the invention aims to solve]

[0006] However, conventional centralized control methods for wireless resources, such as RATOP, had a problem in that they could not efficiently increase the effective throughput of the entire system when relay devices relayed traffic.

[0007] The present invention aims to provide a wireless communication system, a central control device, a central control method, and a central control program that can centrally control the allocation of wireless resources in order to efficiently expand the overall communication capacity of the system when traffic is relayed by a relay device. [Means for solving the problem]

[0008] A wireless communication system according to one embodiment of the present invention comprises a plurality of base stations that perform wireless communication via a plurality of relay devices accommodating wireless terminals, and a central control device that centrally controls each of the base stations and the relay devices, wherein the central control device includes a utility function calculation unit that calculates a utility function for each of the plurality of base stations and the plurality of relay devices, which is the ratio of the amount of transmittable traffic to the amount of accommodated traffic based on the allocated channel and bandwidth; a setting unit that sets a value corresponding to the amount of transmittable traffic of the higher-level device in the relay configuration as the amount of accommodated traffic of the lower-level device based on each of the utility functions calculated by the utility function calculation unit; and a change control unit that performs control to change the channel and bandwidth of each of the plurality of base stations and the plurality of relay devices so that the sum of the utility functions calculated by the utility function calculation unit after the setting unit has set the amount of accommodated traffic is maximized.

[0009] Another wireless communication system according to one embodiment of the present invention is a wireless communication system comprising a plurality of base stations that perform wireless communication via a plurality of relay devices accommodating wireless terminals, and a central control device that centrally controls each of the base stations and the relay devices, wherein the central control device comprises a utility function calculation unit that calculates a utility function for each of the plurality of base stations and the plurality of relay devices, which is the ratio of the amount of transmittable traffic to the amount of accommodated traffic based on the allocated channel and bandwidth; a setting unit that sets a value corresponding to the sum of the transmittable traffic amounts of the lower-level devices in the relay configuration as the amount of accommodated traffic of the higher-level devices based on each of the utility functions calculated by the utility function calculation unit; and a change control unit that performs control to change the channels and bandwidths of each of the plurality of base stations and the plurality of relay devices so that the sum of the utility functions calculated by the utility function calculation unit after the setting unit has set the amount of accommodated traffic is maximized.

[0010] Another wireless communication system according to one embodiment of the present invention is a wireless communication system comprising a plurality of base stations that perform wireless communication via a plurality of relay devices that accommodate wireless terminals, and a central control device that centrally controls each of the base stations and the relay devices, wherein the central control device comprises a utility function calculation unit that calculates for each of the plurality of base stations and the plurality of relay devices the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of traffic that can be accommodated as a utility function, a setting unit that sets for each of the plurality of base stations and the plurality of relay devices the sum of the traffic that can be accommodated by the wireless terminals and the relay devices that can be connected to as the traffic that can be accommodated by the device, based on the utility functions calculated by the utility function calculation unit, and a change control unit that performs control to change the channel and bandwidth of each of the plurality of base stations and the plurality of relay devices so that the sum of the utility functions calculated by the utility function calculation unit after the setting unit has set the traffic that can be accommodated is maximized.

[0011] Furthermore, a central control device according to one embodiment of the present invention is a central control device that centrally controls a plurality of relay devices that accommodate wireless terminals and a plurality of base stations that perform wireless communication via the relay devices, and is characterized by comprising: a utility function calculation unit that calculates a utility function for each of the plurality of base stations and the plurality of relay devices, which is the ratio of the amount of transmittable traffic to the amount of received traffic based on the allocated channel and bandwidth; a setting unit that sets a value corresponding to the amount of transmittable traffic of the higher-level device in the relay configuration as the amount of received traffic of the lower-level device based on each of the utility functions calculated by the utility function calculation unit; and a change control unit that performs control to change the channel and bandwidth of each of the plurality of base stations and the plurality of relay devices so that the sum of the utility functions calculated by the utility function calculation unit after the setting unit has set the amount of received traffic is maximized.

[0012] Furthermore, another centralized control device according to one embodiment of the present invention is a centralized control device that centrally controls a plurality of relay devices that accommodate wireless terminals and a plurality of base stations that perform wireless communication via the relay devices, and is characterized by comprising: a utility function calculation unit that calculates a utility function for each of the plurality of base stations and the plurality of relay devices, which is the ratio of the amount of transmittable traffic to the amount of received traffic based on the allocated channel and bandwidth; a setting unit that sets a value corresponding to the sum of the transmittable traffic of the lower-level devices in the relay configuration as the amount of received traffic of the higher-level devices based on the utility functions calculated by the utility function calculation unit; and a change control unit that performs control to change the channel and bandwidth of each of the plurality of base stations and the plurality of relay devices so that the sum of the utility functions calculated by the utility function calculation unit after the setting unit has set the amount of received traffic is maximized.

[0013] Furthermore, another centralized control device according to one embodiment of the present invention is a centralized control device that centrally controls a plurality of relay devices that accommodate wireless terminals and a plurality of base stations that perform wireless communication via the relay devices, and is characterized by comprising: a utility function calculation unit that calculates a utility function for each of the plurality of base stations and the plurality of relay devices the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of traffic that can be accommodated; a setting unit that sets the sum of the traffic amounts that can be connected to each of the plurality of base stations and the plurality of relay devices as the traffic amount that can be accommodated by each of the plurality of base stations and the plurality of relay devices based on the utility functions calculated by the utility function calculation unit; and a change control unit that performs control to change the channels and bandwidths of each of the plurality of base stations and the plurality of relay devices so that the sum of the utility functions calculated by the utility function calculation unit is maximized after the setting unit has set the traffic amount that can be accommodated.

[0014] Furthermore, a centralized control method according to one embodiment of the present invention is a centralized control method for centrally controlling a plurality of relay devices that accommodate wireless terminals and a plurality of base stations that perform wireless communication via the relay devices, and is characterized by including a utility function calculation step of calculating a utility function for each of the plurality of base stations and the plurality of relay devices the ratio of the amount of transmittable traffic to the amount of accommodated traffic based on the allocated channel and bandwidth; a setting step of setting a value corresponding to the amount of transmittable traffic of the higher-level device in the relay configuration as the amount of accommodated traffic of the lower-level device based on each of the utility functions calculated in the utility function calculation step; and a change control step of performing control to change the channel and bandwidth of each of the plurality of base stations and the plurality of relay devices after setting the amount of accommodated traffic in the setting step so that the sum of the utility functions calculated in the utility function calculation step is maximized. [Effects of the Invention]

[0015] According to the present invention, when traffic is relayed by a relay device, the allocation of wireless resources can be centrally controlled to efficiently expand the overall communication capacity of the system. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows an overview of an example configuration of a wireless communication system according to one embodiment. [Figure 2] This figure shows a specific example of the RATOP algorithm executed by the central control unit. [Figure 3] This is a functional block diagram illustrating the functions of a centralized control device according to one embodiment. [Figure 4] This figure shows an overview of a more specific first configuration example of a wireless communication system. [Figure 5] This figure shows an overview of a more specific second configuration example of a wireless communication system. [Figure 6] This figure shows an overview of a third, more specific configuration example of a wireless communication system. [Figure 7]It is a diagram outlining a more specific fourth configuration example of a wireless communication system. [Figure 8] It is a flowchart showing an operation example of a wireless communication system according to an embodiment. [Figure 9] It is a diagram illustrating an example of a hardware configuration included in a centralized control apparatus according to an embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0017] First, an outline of a wireless communication system according to an embodiment will be described. FIG. 1 is a diagram outlining a configuration example of a wireless communication system 1 according to an embodiment. The wireless communication system 1 is, for example, a wireless LAN system, to which the above-mentioned RATOP is applied.

[0018] As shown in FIG. 1, the wireless communication system 1 includes, for example, a plurality of base stations 2 connected to a network 100, a plurality of relay apparatuses 3, a centralized control apparatus 4, and a plurality of wireless terminals 5. Each base station 2 performs bidirectional wireless communication (data transmission) with a wireless terminal 5 via any one of the relay apparatuses 3.

[0019] Further, each of the base stations 2 and the relay apparatuses 3 accommodates the plurality of wireless terminals 5 by being centrally controlled by the centralized control apparatus 4. For example, each base station 2 performs wireless communication with a wireless terminal 5 via the plurality of relay apparatuses 3. Hereinafter, a base station may be referred to as an AP.

[0020] The centralized control apparatus 4 performs RATOP control targeting the plurality of base stations 2 and relay apparatuses 3. At this time, it is assumed that the control index is the utility function U (= corresponding to satisfaction) shown in the following formula (1).

[0021]

Mathematical formula

[0022] The amount of traffic that AP(a) can transmit depends on the channel usage status of other APs, etc. Furthermore, the amount of traffic that can be accommodated (which depends on the amount of data generated) is, for example, the estimated maximum traffic of AP(a) shown in equation (2) below.

[0023]

number

[0024] In addition, the traffic capacity may be calculated as the traffic capacity per wireless terminal (5) multiplied by the number of assumed wireless terminals.

[0025] The central control unit 4 then performs a process to maximize the sum ΣU of the utility functions U according to the following algorithm.

[0026] RATOP's algorithm: (A): The central control unit 4 "provisionally allocates" the channels and bandwidth used by each AP according to predetermined rules. (B): The central control unit 4 calculates the sum ΣU of the utility functions U of each AP in the case of (A) above. (C): The central control unit 4 reallocates channels and bandwidths to APs with low utility function U, and controls them so that ΣU does not decrease. The central control unit 4 then repeats (C) within a predetermined range.

[0027] Figure 2 shows a specific example of the RATOP algorithm executed by the central control unit 4. As shown in Figure 2, the central control unit 4 performs Phase I (initial calculation) and Phase II (optimization).

[0028] In Phase I, the central control unit 4 selects one AP and designates it as AP-a (S100), selects a bandwidth b that can be allocated to AP-a (S102), selects a channel c that can be allocated to AP-a (S104), and calculates the utility function U of AP-a (S106).

[0029] The central control unit 4 then performs the processes in S104 and S106 for all channels c, and then repeats the process for all bandwidths b.

[0030] Next, the central control unit 4 selects the combination of (b,c) that maximizes the utility function U (S108), and repeats the process for all APs.

[0031] In Phase II, the central control unit 4, for example, selects AP with a small utility function U, and then repeatedly selects a combination (parameters) (b,c) that maximizes the utility function U and does not degrade the sum ΣU of the utility functions U (S110).

[0032] The central control unit 4 then uses the selected combination of (b,c) from each AP as the controlled allocated bandwidth and channel, respectively.

[0033] In this way, RATOP's central control unit 4 understands the status of each AP and allocates the frequency channel and bandwidth that each AP should use. As an evaluation index for the allocation, the central control unit 4 defines the ratio (utility function) of the estimated amount of transmittable traffic (transmittable traffic) based on the allocated radio resources (channel and bandwidth) to the estimated amount of maximum traffic (accommodated traffic) of each AP, and controls the system in a direction that maximizes the sum of the utility functions.

[0034] Figure 3 is a functional block diagram illustrating the functions of a centralized control device 4 according to one embodiment. As shown in Figure 3, the centralized control device 4 includes, for example, a wireless communication unit 41, a data collection unit 42, a utility function calculation unit 43, a setting unit 44, a change control unit 45, and a main control unit 46.

[0035] The wireless communication unit 41 transmits and receives signals to and from each base station 2 via wireless communication.

[0036] The data collection unit 42 collects information about the base station 2, the relay device 3, and the wireless terminal 5 via the wireless communication unit 41 and outputs it to the utility function calculation unit 43. For example, the data collection unit 42 collects information about the base station 2, the relay device 3, and the wireless terminal 5 (such as traffic information).

[0037] The utility function calculation unit 43 calculates a utility function for each of the multiple base stations 2 and multiple relay devices 3, based on the information collected by the collection unit 42, which is the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic, and outputs the calculated utility function to the setting unit 44.

[0038] The setting unit 44 is characterized by its function of setting a value corresponding to the amount of traffic that can be transmitted by the higher-level device (such as the same value or a value multiplied by a coefficient) as the traffic capacity of the lower-level device, based on each utility function calculated by the utility function calculation unit 43, in order to avoid the allocation of higher-level devices in the relay configuration becoming a bottleneck and the allocation of lower-level devices being wasted.

[0039] Furthermore, the setting unit 44 may be characterized by a function that sets a value (the same value or a value multiplied by a coefficient, etc.) corresponding to the sum of the available traffic amounts of the lower-level devices, based on each utility function calculated by the utility function calculation unit 43, so that the higher-level device in the relay configuration can secure enough traffic to accommodate the lower-level devices below it.

[0040] Furthermore, the setting unit 44 may also be characterized by a function that, in order to ensure that the total system traffic amount is neither excessive nor insufficient compared to the required amount, reflects the number of devices that perform wireless communication via relay and the number of devices under them, and, based on the utility function calculated by the utility function calculation unit 43, assumes the number of under-device wireless terminals 5 and the traffic amount per terminal, and sets the total traffic amount of each wireless terminal 5 that can be connected and each relay device 3 as the traffic amount of the device itself.

[0041] The change control unit 45 controls the channels and bandwidths of each of the multiple base stations 2 and multiple relay devices 3 so that the sum of the utility functions calculated by the utility function calculation unit 43 after the setting unit 44 has set the amount of traffic to be accommodated is maximized.

[0042] The main control unit 46 controls each component that makes up the central control device 4.

[0043] In other words, the central control unit 4 performs control to change the channels and bandwidths of each of the multiple base stations 2 and multiple relay devices 3 after the setting unit 44 has set the traffic capacity for each of the multiple base stations 2 and multiple relay devices 3.

[0044] Next, we will describe the wireless communication system 1 in more detail. Figure 4 is a diagram showing an overview of a more specific first configuration example of the wireless communication system 1.

[0045] In the following more specific configuration examples of the wireless communication system 1, the explanation will focus on the control performed by the centralized control device 4, which is not shown in the diagram.

[0046] Furthermore, base station 20 is a base station (AP) that performs wireless communication using, for example, the 920 MHz band. Base station 22 is a base station (AP) that performs wireless communication using, for example, the 5 / 6 GHz band.

[0047] Furthermore, relay units 30 (30-1, 30-2, 30-3) will perform wireless communication using, for example, the 920 MHz band. Relay unit 32 will perform wireless communication using, for example, the 5 / 6 GHz band. One or more relay units 30 and relay units 32 will function as a single relay device 3.

[0048] Furthermore, wireless terminal 50 will perform wireless communication using, for example, the 5 / 6 GHz band. Wireless terminal 52 will perform wireless communication using, for example, the 920 MHz band.

[0049] In the example shown in Figure 4, the setting unit 44 sets the traffic capacity of the lower-level device to the same value (or a value multiplied by a coefficient) as the traffic capacity that can be discharged by the higher-level device.

[0050] First, the central control unit 4 performs the initial allocation of each device using RATOP in the 920MHz band and the 5 / 6GHz band (if systems from different frequency bands are mixed, allocation is performed using RATOP for each frequency band).

[0051] In this case, the transmittable traffic capacity of base station 20 is set to 2 Mbps. Furthermore, base station 22 and relay unit 32 share wireless resources in the 5 / 6 GHz band, and their respective transmittable traffic capacities are set to 60 Mbps.

[0052] Next, the central control unit 4 compares the transmittable traffic volume of the base station 20, which is the higher-level unit in the relay configuration, with that of the lower-level relay devices (relay unit 32, relay unit 30-2, and relay unit 30-3).

[0053] Next, the central control unit 4, with respect to the lower-level devices (relay unit 32, relay unit 30-2, relay unit 30-3), sets the amount of traffic it can handle to the same value as the amount of traffic the base station 20 can transmit (or a value close to the value obtained by multiplying the base station 20 by a coefficient) if the amount of traffic it can handle is greater than the amount of traffic the higher-level device (base station 20) can transmit.

[0054] Here, when the central control unit 4 sets the traffic capacity, it sets the traffic capacity of the relay unit 32 to 2 Mbps because the relay unit 32 is under the control of the base station 20 (transmittable traffic capacity of 2 Mbps). This is because although the base station 22 and the relay unit 32 share radio resources and have a transmittable traffic capacity of 60 Mbps, setting the relay unit 32 to more than 2 Mbps would be wasteful. In addition, the transmittable traffic capacity of the relay unit 32 will be 2 Mbps or less.

[0055] Then, the central control unit 4 controls RATOP again for the entire system based on the set traffic volume. The central control unit 4 may also control RATOP only for relay units 32, 30-2, and 30-3.

[0056] The relay unit 32 and the base station 22 share wireless resources in the same 5 / 6GHz band. Therefore, by reducing the wasted transmittable traffic of the relay unit 32, it is possible to increase the transmittable traffic of the base station 22 beyond 60Mbps.

[0057] Figure 5 shows an overview of a more specific second configuration example of the wireless communication system 1. In the example shown in Figure 5, the setting unit 44 sets the traffic capacity of the higher-level device to the same value (or a value multiplied by a coefficient) as the sum of the transmittable traffic amounts of the lower-level devices. The central control unit 4 then increases the transmittable traffic amount of the higher-level device, eliminating the traffic bottleneck in the higher-level device.

[0058] First, the central control unit 4 assigns each device to the 920MHz band and the 5 / 6GHz band using RATOP (if systems from different frequency bands are mixed, RATOP is assigned to each frequency band separately).

[0059] For example, for a 920MHz band device, let θ1 be the traffic capacity of base station 20. Let θ2 be the traffic capacity of relay unit 30-2. Let θ3 be the traffic capacity of relay unit 30-3. In this case, the shared radio resources (total transmittable traffic) are the sum of the transmittable traffic capacity Φ1 of base station 20, the transmittable traffic capacity Φ2 of relay unit 30-2, and the transmittable traffic capacity Φ3 of relay unit 30-3 (Φ1 + Φ2 + Φ3 = S).

[0060] Furthermore, relay unit 32 accommodates traffic at a different frequency (5 / 6 GHz band) than relay units 30-2 and 30-3.

[0061] The central control unit 4 controls the devices so that the utility function is equal across all devices, using RATOP control.

[0062] The transmittable traffic amount of base station 20 is Φ1 = S × θ1 / (θ1 + θ2 + θ3). The transmittable traffic amount of relay unit 30-2 is Φ2 = S × θ2 / (θ1 + θ2 + θ3). The transmittable traffic amount of relay unit 30-3 is Φ3 = S × θ3 / (θ1 + θ2 + θ3).

[0063] Furthermore, the amount of traffic that can be transmitted through the relay unit 32 is set to Φ4 (>Φ1). However, the amount of traffic that can be transmitted through the relay unit 32 is limited to a maximum of Φ1 due to a bottleneck.

[0064] Furthermore, the transmittable traffic volume of base station 20 is smaller than the total transmittable traffic volume of the devices under its control, becoming a traffic bottleneck in the wireless communication system 1.

[0065] Next, the central control unit 4 sets the traffic capacity of the higher-level device (base station 20) by reflecting the total amount of transmittable traffic of the lower-level devices (relay unit 32, relay units 30-2, 30-3).

[0066] Then, the central control unit 4 controls RATOP for the entire system again based on the set traffic capacity. The central control unit 4 may also control RATOP only for the base station 20 and relay units 30-2 and 30-3.

[0067] For example, the central control unit 4 resets the traffic capacity of the base station 20 to the sum of the transmitted traffic amounts of the subordinate devices θ1a = Φ2 + Φ3 + Φ4 (> θ1). The transmittable traffic amount becomes Φ1a = S × θ1a / (θ1a + θ2 + θ3), which is greater than Φ1.

[0068] The amount of traffic that can be transmitted from relay unit 30-2 is given by Φ2a = S × θ2 / (θ1a + θ2 + θ3).

[0069] The amount of traffic that can be transmitted from relay unit 30-3 is given by Φ3a = S × θ3 / (θ1a + θ2 + θ3).

[0070] The maximum traffic volume Φ4a that can be transmitted from the relay unit 32 becomes Φ1a (>Φ1) due to the bottleneck.

[0071] Furthermore, after resetting, the transmittable traffic amounts become Φ1 < Φ1a, Φ2 > Φ2a, and Φ3 > Φ3a (θ1a > θ1. ΣΦ = ΣΦa = S). Since Φ1a becomes larger than Φ1, the bottleneck caused by the base station 20 to the relay unit 32 can be alleviated, and the bottlenecks for relay units 30-2 and 30-3 can also be alleviated.

[0072] Figure 6 shows an overview of a more specific third configuration example of the wireless communication system 1. In the example shown in Figure 6, the setting unit 44 sets the traffic capacity of the higher-level device to the same value (or a value multiplied by a coefficient) as the sum of the transmittable traffic amounts of the lower-level devices. The central control unit 4 then increases the transmittable traffic amount of the higher-level device, eliminating the traffic bottleneck in the higher-level device.

[0073] In the example shown in Figure 6, base station 20 has a capacity of 4 Mbps and a transmittable traffic capacity of 2 Mbps. Relay unit 30-2 has a capacity of 4 Mbps and a transmittable traffic capacity of 2 Mbps.

[0074] Furthermore, it is assumed that the base station 20 and relay unit 30-2, which use the 920MHz band, share radio resources (total transmittable traffic) of 4Mbps (here, for simplicity, it is assumed that there is no sharing of radio resources with surrounding radio equipment).

[0075] The relay unit 32 is configured to have a maximum transmittable traffic capacity of 60 Mbps. However, because the upstream equipment is a bottleneck, the maximum transmittable traffic capacity of the relay unit 32 is 2 Mbps.

[0076] In the re-implementation of RATOP, the central control unit 4 recalculates the traffic capacity of the base station 20 from the sum of the transmittable traffic capacity of the subordinate relay units 32 and 30-2, using 60 + 2 = 62. The transmittable traffic capacity becomes greater than 2 Mbps (for example, 4 × (62 / (62 + 2)) = 3.85 Mbps).

[0077] The relay unit 30-2 has a capacity of 4 Mbps and a transmittable traffic capacity less than 2 Mbps (for example, 4 × (2 / (62 + 2)) = 0.125 Mbps).

[0078] The relay unit 32 has a maximum transmittable traffic capacity of 60 Mbps, but due to a bottleneck in the higher-level equipment, the maximum is 3.85 Mbps.

[0079] The effective maximum traffic volume of the relay unit 32 (5 / 6GHz) under base station 20 increases from 2Mbps to 3.85Mbps.

[0080] Figure 7 shows an overview of a more specific fourth configuration example of the wireless communication system 1. In the example shown in Figure 7, the setting unit 44 assumes, for example, the number of wireless terminals under its control and the amount of traffic each terminal can handle for each base station or relay device, and sets the sum of the traffic amounts of the wireless terminals under its control as its own traffic amount. For example, when the central control device 4 sets the traffic amount, it aggregates from the lowest level. Furthermore, the wireless communication system 1 may have a large number of hops, and the number of wireless terminals may be unclear, with only the number of relay devices being known.

[0081] For example, the central control unit 4 assumes the amount of traffic each terminal can handle for each frequency band. Then, for each base station and relay device, the central control unit 4 calculates the amount of traffic it can handle, starting from the lowest level, based on the number of wireless terminals and relay devices under its control.

[0082] The central control unit 4 then controls the entire RATOP system, starting from the lowest level, based on the amount of traffic it can accommodate.

[0083] For example, the traffic capacity of base station 20 is calculated by combining the 30Mbps x 2 → 60Mbps relayed by relay unit 32, the 2Mbps x 2 → 4Mbps relayed by relay unit 30-2, and the 2Mbps x 2 → 4Mbps relayed by relay unit 30-3, resulting in a total traffic capacity of 60 + 4 + 4Mbps.

[0084] Next, an example of the overall operation of the wireless communication system 1 will be described. Figure 8 is a flowchart showing an example of the operation of the wireless communication system 1 according to one embodiment, taking into account the number of wireless terminals.

[0085] First, each base station determines whether or not it has received an instruction from the central control unit 4 to collect information (S200). If there is an instruction (S200:Yes), it proceeds to process S202; otherwise, it repeats process S200.

[0086] In step 202 (S202), each base station obtains information on the number of relay devices and wireless terminals it houses and notifies the central control unit 4.

[0087] In step 204 (S204), each base station determines whether or not it has received a control instruction from the central control unit 4 to update the bandwidth b and channel c (parameters) of the relay equipment and wireless terminals it accommodates (or a control instruction to update traffic allocation). If each base station determines that it has received a control instruction (S204:Yes), it proceeds to process S206; if it determines that it has not received a control instruction (S204:No), it returns to process S200.

[0088] In step 206 (S206), each base station performs change control (or control to update traffic allocation) to change the bandwidth b and channel c (parameters).

[0089] Thus, in one embodiment of the wireless communication system 1, the setting unit 44 sets the amount of traffic to be accommodated, and the change control unit 45 controls the channels and bandwidths of each of the multiple base stations and multiple relay devices. Therefore, when a relay device relays traffic, the allocation of wireless resources can be centrally controlled to efficiently expand the overall communication capacity of the system.

[0090] Furthermore, each function of the central control unit 4 may be partially or entirely comprised of hardware such as a PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array), or it may be comprised of a program executed by a processor such as a CPU.

[0091] For example, the centralized control unit 4 can be implemented using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0092] Figure 9 illustrates the hardware configuration of a centralized control device 4 according to one embodiment. As shown in Figure 9, the centralized control device 4 has an input unit 400, an output unit 410, a communication unit 420, a CPU 430, a memory 440, and an HDD 450 connected via a bus 460, and is equipped with computer functions. The centralized control device 4 is also capable of inputting and outputting data to and from a computer-readable storage medium 470.

[0093] The input unit 400 is, for example, a keyboard and mouse. The output unit 410 is, for example, a display device such as a display.

[0094] The communication unit 420 is a communication interface that performs wireless communication, such as via a wireless LAN.

[0095] The CPU 430 controls each component of the central control unit 4 and performs predetermined processing. The memory 440 and HDD 450 store data, etc.

[0096] The storage medium 470 is capable of storing programs and the like that cause the central control unit 4 to execute its functions. Note that the architecture of the central control unit 4 is not limited to the example shown in Figure 9. [Explanation of symbols]

[0097] 1... Wireless communication system, 2, 20, 22... Base station, 3... Relay device, 4... Centralized control unit, 5, 50, 52... Wireless terminal, 30-1~30-3, 32... Relay unit, 41... Wireless communication unit, 42... Data collection unit, 43... Utility function calculation unit, 44... Setting unit, 45... Change control unit, 46... Main control unit, 100... Network, 400... Input unit, 410... Output unit, 420... Communication unit, 430... CPU, 440... Memory, 450... HDD, 460... Bus, 470... Storage medium

Claims

1. In a wireless communication system comprising multiple base stations that perform wireless communication via multiple relay devices accommodating wireless terminals, and a central control device that centrally controls each of the base stations and relay devices, The aforementioned centralized control device is A utility function calculation unit calculates, for each of the multiple base stations and multiple relay devices, the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic as a utility function, Based on the utility function calculated by the utility function calculation unit, a setting unit sets a value corresponding to the amount of transmittable traffic of the higher-level device in the relay configuration as the amount of traffic accommodated by the lower-level device. A change control unit controls the channels and bandwidths of each of the multiple base stations and multiple relay devices so that the sum of the utility functions calculated by the utility function calculation unit is maximized after the setting unit sets the traffic capacity. A wireless communication system characterized by having the following features.

2. In a wireless communication system comprising multiple base stations that perform wireless communication via multiple relay devices accommodating wireless terminals, and a central control device that centrally controls each of the base stations and relay devices, The aforementioned centralized control device is A utility function calculation unit calculates, for each of the multiple base stations and multiple relay devices, the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic as a utility function, Based on the utility functions calculated by the utility function calculation unit, a setting unit sets a value corresponding to the sum of the available traffic amounts of the lower-level devices in the relay configuration as the traffic capacity of the higher-level device. A change control unit controls the channels and bandwidths of each of the multiple base stations and multiple relay devices so that the sum of the utility functions calculated by the utility function calculation unit is maximized after the setting unit sets the traffic capacity. A wireless communication system characterized by having the following features.

3. In a wireless communication system comprising multiple base stations that perform wireless communication via multiple relay devices accommodating wireless terminals, and a central control device that centrally controls each of the base stations and relay devices, The aforementioned centralized control device is A utility function calculation unit calculates, for each of the multiple base stations and multiple relay devices, the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic as a utility function, Based on the utility function calculated by the utility function calculation unit, a setting unit sets the total of the traffic capacity of each of the multiple base stations and multiple relay devices that can be connected to each of the relay devices as the traffic capacity of the device itself. A change control unit controls the channels and bandwidths of each of the multiple base stations and multiple relay devices so that the sum of the utility functions calculated by the utility function calculation unit is maximized after the setting unit sets the traffic capacity. A wireless communication system characterized by having the following features.

4. In a central control device that centrally controls multiple relay devices that accommodate wireless terminals and multiple base stations that perform wireless communication via the relay devices, A utility function calculation unit calculates, for each of the multiple base stations and multiple relay devices, the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic as a utility function, Based on the utility function calculated by the utility function calculation unit, a setting unit sets a value corresponding to the amount of transmittable traffic of the higher-level device in the relay configuration as the amount of traffic accommodated by the lower-level device. A change control unit controls the channels and bandwidths of each of the multiple base stations and multiple relay devices so that the sum of the utility functions calculated by the utility function calculation unit is maximized after the setting unit sets the traffic capacity. A centralized control device characterized by having the following features.

5. In a central control device that centrally controls multiple relay devices that accommodate wireless terminals and multiple base stations that perform wireless communication via the relay devices, A utility function calculation unit calculates, for each of the multiple base stations and multiple relay devices, the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic as a utility function, Based on the utility functions calculated by the utility function calculation unit, a setting unit sets a value corresponding to the sum of the available traffic amounts of the lower-level devices in the relay configuration as the traffic capacity of the higher-level device. A change control unit controls the channels and bandwidths of each of the multiple base stations and multiple relay devices so that the sum of the utility functions calculated by the utility function calculation unit is maximized after the setting unit sets the traffic capacity. A centralized control device characterized by having the following features.

6. In a central control device that centrally controls multiple relay devices that accommodate wireless terminals and multiple base stations that perform wireless communication via the relay devices, A utility function calculation unit calculates, for each of the multiple base stations and multiple relay devices, the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic as a utility function, Based on the utility function calculated by the utility function calculation unit, a setting unit sets the total of the traffic capacity of each of the multiple base stations and multiple relay devices that can be connected to each of the relay devices as the traffic capacity of the device itself. A change control unit controls the channels and bandwidths of each of the multiple base stations and multiple relay devices so that the sum of the utility functions calculated by the utility function calculation unit is maximized after the setting unit sets the traffic capacity. A centralized control device characterized by having the following features.

7. In a centralized control method for centrally controlling multiple relay devices that accommodate wireless terminals and multiple base stations that perform wireless communication via the relay devices, A utility function calculation step for each of the multiple base stations and multiple relay devices, which calculates the ratio of the amount of transmittable traffic based on the allocated channel and bandwidth to the amount of accommodated traffic as a utility function; Based on the utility functions calculated in the utility function calculation step, a setting step is performed to set a value corresponding to the amount of transmittable traffic of the higher-level device in the relay configuration as the amount of traffic accommodated by the lower-level device. After setting the traffic capacity in the setting step, a change control step is performed to control the channels and bandwidths of each of the multiple base stations and multiple relay devices so that the sum of the utility functions calculated in the utility function calculation step is maximized. A centralized control method characterized by including the following:

8. A centralized control program for causing a computer to function as one of the components of the centralized control device according to any one of claims 4 to 6.

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