CONTROLLER, COMMUNICATION SYSTEM, CONTROL METHOD, AND PROGRAM

Abstract

The objective of the present invention is to provide a controller, a communication system, a control method and a program that enable a transmission scheduling for avoiding mutual interferences with respect to a plurality of wireless networks so as to solve the foregoing problem.　A controller 13 according to the present invention is characterized by comprising a scheduler SCH3 that performs: calculating, every predetermined period, a transmission schedule of packets that are to be transmitted from buffers (FB1, FB2) on the basis of a packet amount stored by a database DB; and setting a limit such that when the transmission schedule is calculated, a total amount of packets that are to be transmitted from all of the buffers (FB1, FB2) included in each of a plurality of networks NW #j does not exceed the product of the throughput of the respective network NW #j and the predetermined period.

Description

[Technical field]

[0001] The present disclosure relates to a controller, a communication system, a control method, and a program for controlling communications of a plurality of access networks. [Background technology]

[0002] In recent years, studies are being conducted on accommodating multiple services and applications with various network requirements on the same network infrastructure.To achieve this, it is necessary to guarantee the quality required by each service or application accommodated on the same network (NW) in the end-to-end sections from "terminal to terminal" or "terminal to application server."

[0003] The end-to-end network can be divided into wireless and wired sections. Among them, in the wireless section, there is a priority control function called Enhanced Distributed Channel Access (EDCA) of IEEE802.11 as an existing technology (see, for example, Non-Patent Documents 1 and 2).

[0004] EDCA is a terminal (destination)-based control, and it is difficult to control on a traffic flow basis, which would enable quality control on a service and application basis. However, by applying the technology described in Non-Patent Document 3, it is possible to realize quality control on a service and application basis. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] IEEE 802.11e-2005 - IEEE Standard for Information technology--Local and metropolitan area networks--Specific requirements--Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications - Amendment 8: Medium Access Control (MAC) Quality of Service Enhancements [Non-Patent Document 2] "IEEE802.11e: Wireless LAN standard for achieving QoS," Journal of the Institute of Image Information and Television Engineers, Vol. 57, No. 11 (2003) [Non-Patent Document 3] Yuki Sakagami, Kazuki Aiura, Tatsuya Fukui, et al.: "Proposal of quality control technology by centralized control independent of wireless network", Institute of Electronics, Information and Communication Engineers General Conference, March 9, 2021, B-6-5 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the transmission control technology in Non-Patent Document 3 is a technology for a single wireless network. For this reason, for example, when multiple access points use a wireless network of the same frequency as shown in Fig. 1, interference occurs due to their wireless communications, and the transmission control technology in Non-Patent Document 3 has the problem that it is difficult to transmit packets according to the scheduler. For example, if the packet transmission timing of terminals #1-N and #2-N' overlaps, the transmission will physically fail due to interference. No specific solution to this problem has been made clear.

[0007] Therefore, in order to solve the above problem, an object of the present invention is to provide a controller, a communication system, a control method, and a program capable of performing transmission scheduling for multiple wireless networks in such a way as to avoid interference with each other. [Means for solving the problem]

[0008] In order to achieve the above object, a controller according to the present invention collects information from terminals and access points included in each network, and collectively schedules transmission timing.

[0009] Specifically, the controller according to the present invention is a controller that controls traffic of a plurality of networks, Each of the networks has one access point and one or more terminals, and transmits packets between the terminals and the access point; a database for storing, at each predetermined period, the amount of packets stored in a buffer for each traffic flow of the terminal and the access point; a scheduler that calculates a transmission schedule for packets to be transmitted from the buffer based on the packet amounts stored in the database for each of the predetermined periods, and that applies a restriction when calculating the transmission schedule so that the total packet amount to be transmitted from all of the buffers included in the network does not exceed the product of the throughput of each of the networks and the predetermined period; a transmitter for transmitting the transmission schedule to the terminal and the access point; The present invention is characterized by comprising:

[0010] A control method according to the present invention is a control method for controlling traffic of a plurality of networks, comprising the steps of: Each of the networks has one access point and one or more terminals, and transmits packets between the terminals and the access point; storing, at each predetermined period, an amount of packets stored in a buffer for each traffic flow that the terminal and the access point have; calculating a transmission schedule for packets to be transmitted from the buffer based on the amount of packets stored in the database for each of the predetermined periods; When calculating the transmission schedule, adding a restriction so that a total amount of packets to be transmitted from all of the buffers included in the network does not exceed a product of a throughput of each of the networks and the predetermined period; and transmitting the transmission schedule to the terminal and the access point; The present invention is characterized by carrying out the following steps.

[0011] When scheduling packet transmission timing, the controller grasps the amount of packets accumulated from all terminals and access points, sets a limit so that the total packet transmission amount is equal to or less than the product of the throughput and the schedule period, and performs schedule calculation. Therefore, the present invention can provide a controller and a control method that can perform transmission scheduling for multiple wireless networks that avoids mutual interference.

[0012] The calculation method is as follows. (1) First calculation method The database also stores the bandwidth of each of the networks; The scheduler is characterized in that, in the restriction, the total amount of packets transmitted from all of the buffers included in each of the networks is equal to or less than the bandwidth of each of the networks. (2) Second calculation method The scheduler The predetermined period is divided for each of the networks to obtain divided periods, In the above restriction, the product of the throughput of each of the networks and the predetermined period is set to the product of the throughput of each of the networks and the division period. It is characterized by: (3) The third calculation method If the communication between the terminal and the access point is Orthogonal Frequency-Division Multiplexing (OFDM), The scheduler Divide each subcarrier available in the network into divided subcarriers for each network; In the above restriction, the product of the throughput of each of the networks and the predetermined period is set to the product of the throughput of each of the networks when the subcarriers are divided and the predetermined period.

[0013] Moreover, a communication system according to the present invention includes the controller, and a plurality of networks each having one of the access points and one or a plurality of the terminals.

[0014] Furthermore, the present invention relates to a program for causing a computer to function as the controller. The data collection device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0015] The above-mentioned inventions can be combined as much as possible. Effect of the Invention

[0016] The present invention can provide a controller, a communication system, a control method, and a program that are capable of performing transmission scheduling for a plurality of wireless networks to avoid interference with each other. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a problem to be solved by the present invention. [Diagram 2] FIG. 1 is a diagram illustrating a communication system according to the present invention. [Diagram 3] FIG. 4 is a diagram illustrating a database provided in a controller according to the present invention. [Figure 4] FIG. 4 is a diagram illustrating a database provided in a controller according to the present invention. [Diagram 5] FIG. 4 is a diagram illustrating a control method according to the present invention. [Figure 6] FIG. 4 is a diagram illustrating a control method according to the present invention. [Figure 7] FIG. 4 is a diagram illustrating a control method according to the present invention. [Figure 8] FIG. 1 is a diagram illustrating a communication system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0019] (Embodiment 1) Fig. 2 is a diagram for explaining the communication system of this embodiment. This communication system includes a controller 13, and multiple networks (NW#1, NW#2) each having one access point 12 and one or multiple terminals 11. In Fig. 2, the number of networks NW is two, but it may be three or more. In addition, the networks are wireless networks, and all of them communicate at the same frequency.

[0020] The controller 13 is connected to each terminal 11 and each access point 12, and it is assumed that no other network devices exist. The controller 13 previously stores information about each terminal 11 to be connected, each access point 12, the network NW#j to which they belong, and the maximum throughput TP j It is assumed that the above information is recorded in the database unit DB.

[0021] The controller 13 is connected to each terminal 11 and each access point 12 . Each terminal 11 and each access point 12 accumulates packets in a buffer for each traffic flow (per-flow buffer units FB1, FB2) or in a buffer within an application, and notifies the controller 13 of the amount of accumulated packets at predetermined intervals. The controller 13 records the notified accumulated amount of each packet in the database unit DB. The scheduling unit SCH3 of the controller 13 determines the packet transmission schedule (transmission time and transmission amount for each traffic flow) for each flow unit buffer unit (FB1, FB2) based on the information in the database unit DB. At this time, the scheduling unit SCH3 calculates so that the total packet transmission amount according to the schedule does not exceed the product of the throughput and a predetermined period (schedule period). Details of the scheduling will be described later. The controller 13 notifies each terminal 11 and each access point 12 of the determined transmission schedule. The scheduler units (SCH1, SCH2) of each terminal 11 and each access point 12 instruct each per-flow buffer unit (FB1, FB2) to transmit packets according to the notified transmission schedule. Each terminal 11 and each access point 12 transmits packets via a main signal buffer unit (MB1, MB2) and a main signal transmitting / receiving unit (MTR1, MTR2). It is assumed that the times of the terminals 11, the access points 12, and the controller 13 are synchronized using NTP (Network Time Protocol), PTP (Precision Time Protocol), or the like.

[0022] Specifically, the controller 13 is a controller that controls traffic of a plurality of networks NW#j, Each network NW#j has one access point 12 and one or more terminals 11, and transmits packets between the terminals 11 and the access points 12. a database DB for storing the amount of packets stored in the buffers (FB1, FB2) for each traffic flow of the terminal 11 and the access point 12 at each predetermined period; a scheduler SCH3 that calculates a transmission schedule for packets to be transmitted from the buffers (FB1, FB2) based on the packet amounts stored in a database DB for each of the predetermined periods, and that applies a restriction when calculating the transmission schedule so that the total packet amount to be transmitted from all of the buffers (FB1, FB2) included in the network NW#j does not exceed the product of the throughput of each of the networks NW#j and the predetermined period; a transmitter CTR3 for transmitting the transmission schedule to a terminal 11 and an access point 12; The present invention is characterized by comprising:

[0023] This communication system communicates control signals between the controller 13 and the access points 12 / terminals 11 using a communication means separate from the communication means for main signals (traffic packets). Specifically, the control signals are transmitted and received between the control signal transmitting / receiving unit CTR1 of each terminal 11 and the control signal transmitting / receiving unit CTR3 of the controller 13, and between the control signal transmitting / receiving unit CTR2 of each access point 12 and the control signal transmitting / receiving unit CTR3 of the controller 13.

[0024] Each terminal 11 and each access point 12 periodically (every schedule period) notifies the controller 13 of the amount of packets stored in the per-flow buffer units (FB1, FB2) as a control signal. The terminal 11 accumulates packets from each application AP1 in a buffer (FB1#1 to FB1#L / FB1#L') for each application (for each flow). The packet amount notification unit NTF1 periodically checks the amount of accumulated packets in each buffer (FB1#1 to FB1#L / FB1#L') and notifies the controller 13 of the amount as a control signal via the control signal transmission / reception unit CTR1. Also, the access point 12 accumulates packets from the upper network devices (50#1, 50#2) in buffers (FB2#1-FB2#K / FB2#K') for each application (each flow). The packet amount notification unit NTF2 periodically checks the amount of accumulated packets in each buffer (FB2#1-FB2#K / FB2#K') and notifies the controller 13 of this as a control signal via the control signal transmission / reception unit CTR2. Incidentally, each of the flow unit buffer units FB1 may be owned by the application AP1.

[0025] The controller 13 records the notified packet accumulation amount, terminal 11, access point 12, and information on the per-flow buffers (FB1, FB2), and based on that determines a transmission schedule (transmission time and transmission amount) for each buffer and notifies each terminal 11 and each access point 12 as a control signal.

[0026] The control signal transmission / reception unit CTR3 of the controller 13 receives control signals from each terminal 11 and each access point 12, and organizes the packet accumulation amount, terminal 11, access point 12, and per-flow buffer (FB1, FB2) included in the control signal in a database DB.

[0027] 3 and 4 are diagrams for explaining an example of information organized in the database DB. This database DB organizes the following four pieces of information in the first information section (see FIG. 3). Item number: A serial number for all buffers (FB1, FB2) of the terminal 11 and the access point 12. · Belonging wireless network: The number j of the wireless network (NW#1, NW#2) to which the target buffer (FB1, FB2) belongs. Node number: The number of the access point 12 or the terminal 11 . Buffer number: the number of the buffer FB1 held by each terminal 11, or the number of the buffer FB2 held by each access point 12. Packet volume: The amount of packets stored in a buffer with each buffer number. For example, item number K+2 indicates the amount of packets stored in the per-flow buffer unit FB1#2 of the terminal 11#1 belonging to the wireless network NW1 (j=1), and the amount is "B12."

[0028] This database DB organizes the following two pieces of information in the second information section (see Figure 4). · Belonging wireless network: The number j of the wireless network (NW#1, NW#2) to which the target buffer (FB1, FB2) belongs. Throughput: The maximum throughput TP of each wireless network NW#j j It is.

[0029] The scheduling unit SCH3 of the controller 13 uses a scheduling method described later to determine a transmission schedule (transmission time and transmission amount) for each buffer from the contents of the database unit DB. Then, the scheduling unit SCH3 uses the determined transmission schedule as a control signal and transmits it from the control signal transmitting / receiving unit CTR3 to the terminal 11 and the access point 12.

[0030] Each terminal 11 and access point 12 extracts packets stored in the per-flow buffer units (FB1, FB2) at the transmission time and transmission amount of the notified transmission schedule and inputs them to the main signal buffer units (MB1, MB2). The main signal transceiver units (MTR1, MTR2) transmit the packets in the main signal buffer units (MB1, MB2) to the wireless network 15.

[0031] 5 is a flowchart illustrating the above-described operation. The control method of this embodiment is a transmission control performed by the controller 13 on each terminal 11 and each access point 12 that transmit packets to each other via the respective wireless networks (15#1, 15#2), Storing transmission packets for each traffic flow in the buffers (FB1, FB2) of each terminal 11 and each access point 12 (steps S111, S112, S121, S122); Transmitting to the controller 13 the amount of transmission packets stored in each of the buffers for each traffic flow (steps S113 and S123); The controller 13 determines a transmission schedule for the transmission packets for each traffic flow based on the accumulated amounts received from the terminal 11 and the access point 12 (steps S131 and S132); Transmitting the transmission schedule from the controller 13 to each of the terminal 11 and the access point 12 (step S133); and Transmitting transmission packets for each traffic flow from the buffers (FB1, FB2) of the terminal 11 and the access point 12 to the wireless networks (15#1, 15#2) according to the transmission schedule (steps S114, S124). It is characterized by: However, certain restrictions, which will be described later, are imposed when determining the transmission schedule.

[0032] [Scheduling method] Here, we will explain the scheduling method performed by the scheduling unit SCH13 of the controller 13. Any scheduling method may be used, but here we will explain the scheduling method disclosed in Non-Patent Document 3. [1] Fair scheduling This scheduling method performs calculations in which the bandwidth or time is divided by the total number of per-flow buffers (FB1, FB2) in which packets are stored in the terminal 11 and the access point 12. The parameters are explained below. The number of per-flow buffers in which packets are stored, including the terminal 11 and the access point 12 combined: n Time for 1 cycle: T[sec] Total transmission limit of main signal per cycle: Z [Bytes / sec] Time to send the first stored packet: t start [sec]

[0033] in this case, Transmission volume S of flow unit buffer #J J [Bytes] is

number

number

number

[0034] The order of the per-flow buffers from which transmission starts may be, for example, from the lowest item number arranged in the database unit DB of the controller 13 .

[0035] [2] Scheduling with consideration of bandwidth weighting This scheduling method is determined based on the number of per-flow buffers in which packets are stored, and the amount of packets stored, among the per-flow buffers (FB1, FB2) of terminal 11 and access point 12. The parameters are explained below. Packet accumulation amount in per-flow buffer #J: B J [Bytes] Time for 1 cycle: T[sec] Transmission limit per cycle: Z [Bytes / sec] Time required to transmit all packets stored in all per-flow buffers: T all [sec] The time when the first packet is transmitted from all the packets stored in the per-flow buffer: t start [sec]

[0036] in this case,

number

number

number

number

number

number

number

[0037] In addition, T all If >T, packets that cannot be sent are carried over to the next transmission timing.

[0038] [Certain Restrictions] Here, restrictions imposed on the schedule calculation performed by the scheduling unit SCH13 of the controller 13 will be described.

[0039] As a result of the scheduling, the amount of packets to be sent from each flow-based buffer (FB1, FB2) is p i In this case, the total amount of packets P to be transmitted in the scheduling period T can be expressed as follows:

number

[0040] In addition, the throughput TP of each wireless network NW#j j Specifically, the throughput of the wireless network NW#1 is TP1, and the throughput of the wireless network NW#2 is TP2 (see FIG. 4). The controller 13 calculates a transmission schedule so that the following relationship always holds for each wireless network NW#j. [Number A2] T×TP j ≧P This is because when multiple same-frequency wireless networks exist, the maximum throughput is not the sum of the maximum throughputs of each wireless network, but is the maximum throughput among the same-frequency wireless networks divided by each wireless network.

[0041] In addition, the controller 13 controls each wireless network NW in real time. j Throughput tp j If the controller 13 knows, it schedules such that

number

[0042] (Example 1) In this example, the database DB also stores the bandwidth of each network NW#j. The scheduling unit SCH3 is characterized in that, in the above-mentioned restriction, the total amount of packets transmitted from all the buffers (FB1, FB2) included in each network NW#j is equal to or less than the bandwidth of each network NW#j.

[0043] The controller 13 determines in advance the bandwidth to be used by each wireless network NW#j. Specifically, the bandwidth of the wireless network NW#1 is P1, and the bandwidth of the wireless network NW#2 is P2. When calculating the transmission schedule, the scheduling unit SCH3 determines whether the packet transmission amount (the amount of packets transmitted from the main buffer units (MB1, MB2)) of the terminal 11 and the access point 12 belonging to each wireless network NW#j is greater than or equal to the determined bandwidth amount P j In this example, when calculating the transmission schedule, a restriction is imposed so that the relationship in formula (A4) below is satisfied.

number

[0044] (Example 2) In this example, the scheduling period is divided for each network (see FIG. 6). The scheduler 13 The predetermined period T is divided for each network NW#j to obtain the divided period T j year, In the above restriction, the throughput TP of each network NW#j j The product of and the predetermined period T is the throughput TP of each network NW#j. j and the division period T j It is characterized in that the product is

[0045] The scheduler 13 determines in advance the available period (division period T j ) is determined in advance. Specifically, the division periods of the wireless networks NW#1 and NW#2 are T1 and T2, respectively. If the scheduling period is T, the following relationship holds: [Math A5] T=T1+T2

[0046] In this example, when calculating the transmission schedule, each division period T j The throughput of each network is TP jand the following restriction using the total packet amount P is added: [Number A6] T1×TP1≧P T2×TP2≧P

[0047] (Example 3) In this example, the network band is divided into subcarriers (see FIG. 7). When the communication between the terminal 11 and the access point 12 is Orthogonal Frequency-Division Multiplexing (OFDM), the scheduler 13 Each subcarrier SC available in the network NW#j is divided into separate subcarriers SC j year, In the above restriction, the throughput TP of each network NW#j j and the predetermined period T is defined as the product of the throughput of each network NW#j when the subcarriers are divided and the predetermined period T. It is characterized by:

[0048] The scheduler 13 divides the available subcarriers SC in advance as shown in FIG. 7 and assigns them to each wireless network NW#j (divided subcarriers SC j Specifically, the divided subcarriers allocated to the wireless networks NW#1 and NW#2 are designated SC1 and SC2, respectively. If the available subcarriers are designated SC, the following relationship holds: [Number A7] SC=SC1+SC2

[0049] In this example, when calculating the transmission schedule, the divided subcarriers SC j The throughput of each network when j and the following restriction using the total packet amount P is added: [Number A8] T×TP'1≧P T×TP'2≧P

[0050] (Embodiment 2) The controller 13 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. 8 shows a block diagram of a system 100. The system 100 includes a computer 105 connected to a network 135.

[0051] Network 135 is a data communications network. Network 135 may be a private or public network and may include any or all of the following: (a) a personal area network, e.g., covering a room; (b) a local area network, e.g., covering a building; (c) a campus area network, e.g., covering a campus; (d) a metropolitan area network, e.g., covering a city; (e) a wide area network, e.g., covering an area that crosses city, regional, or national boundaries; or (f) the Internet. Communications are conducted by electronic and optical signals over network 135.

[0052] Computer 105 includes a processor 110 and a memory 115 connected to processor 110. Although computer 105 is depicted herein as a stand-alone device, it is not limited to such, but rather may be connected to other devices not shown in a distributed processing system.

[0053] Processor 110 is an electronic device made up of logic circuits that responds to and executes instructions.

[0054] The memory 115 is a tangible computer-readable storage medium in which a computer program is encoded. In this regard, the memory 115 stores data and instructions, i.e., program code, that can be read and executed by the processor 110 to control the operation of the processor 110. The memory 115 can be implemented as a random access memory (RAM), a hard drive, a read-only memory (ROM), or a combination thereof. One component of the memory 115 is a program module 120.

[0055] The program modules 120 include instructions for controlling the processor 110 to perform the processes described herein. Although operations are described herein as being performed by the computer 105 or a method or process or sub-process thereof, those operations are actually performed by the processor 110.

[0056] The term "module" is used herein to refer to a functional operation that may be embodied either as a stand-alone component or as an integrated configuration of multiple subcomponents. Thus, program module 120 may be implemented as a single module or as multiple modules operating in coordination with one another. Furthermore, although program module 120 is described herein as being installed in memory 115 and thus implemented in software, it may be implemented in any of hardware (e.g., electronic circuitry), firmware, software, or a combination thereof.

[0057] Although the program module 120 is shown as already loaded into the memory 115, it may be configured to be located on the storage device 140 for later loading into the memory 115. The storage device 140 is a tangible computer-readable storage medium that stores the program module 120. Examples of the storage device 140 include compact disks, magnetic tapes, read-only memories, optical storage media, memory units consisting of a hard drive or multiple parallel hard drives, and Universal Serial Bus (USB) flash drives. Alternatively, the storage device 140 may be a random access memory or other type of electronic storage device located in a remote storage system not shown and connected to the computer 105 via the network 135.

[0058] System 100 further includes data source 150A and data source 150B, collectively referred to herein as data sources 150, that are communicatively connected to network 135. In practice, data sources 150 may include any number of data sources, i.e., one or more data sources. Data sources 150 may include unstructured data and may include social media.

[0059] The system 100 further includes a user device 130 operated by the user 101 and connected to the computer 105 via a network 135. The user device 130 includes an input device, such as a keyboard or a voice recognition subsystem, to enable the user 101 to communicate information and command selections to the processor 110. The user device 130 further includes an output device, such as a display device or a printer or a voice synthesizer. A cursor control, such as a mouse, trackball, or touch-sensitive screen, enables the user 101 to manipulate a cursor on a display device to communicate further information and command selections to the processor 110.

[0060] The processor 110 outputs the results 122 of the execution of the program modules 120 to a user device 130. Alternatively, the processor 110 can provide the output to a storage device 125, such as a database or memory, or via a network 135 to a remote device, not shown.

[0061] For example, a program for performing steps S131 to S133 in the flowchart of FIG.

[0062] The term "comprising" or "comprising" is to be interpreted as specifying the presence of the stated features, integers, steps or components, but not excluding the presence of one or more other features, integers, steps or components or groups thereof. The terms "a" and "an" are indefinite articles and therefore do not exclude embodiments having a plurality thereof.

[0063] (Other embodiments) In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. In short, the present invention is not limited to the above-described embodiment, and the components can be modified and embodied without departing from the spirit of the present invention at the implementation stage.

[0064] In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components across different embodiments may be appropriately combined. [Explanation of symbols]

[0065] 11, 11#1, 11#2: Terminal 12, 12#1, 12#2: Access points 13: Controller NW#j: Wireless network 50, 50#1, 50#2: Upper network device 100: System 101:User 105: Computer 110: Processor 115: Memory 120: Program module 122:Result 125: Storage device 130: User device 135: Network 140: Storage device 150: Data source 301: Control Systems

Claims

1. A controller for controlling traffic of a plurality of networks, comprising: Each of the networks has one access point and one or more terminals, and transmits packets between the terminals and the access point; a database for storing, at each predetermined period, the amount of packets stored in a buffer for each traffic flow of the terminal and the access point; a scheduler that calculates a transmission schedule for packets to be transmitted from the buffer based on the packet amounts stored in the database for each of the predetermined periods, and that applies a restriction when calculating the transmission schedule so that the total packet amount to be transmitted from all of the buffers included in the network does not exceed the product of the throughput of each of the networks and the predetermined period; a transmitter for transmitting the transmission schedule to the terminal and the access point; A controller comprising:

2. The database also stores the bandwidth of each of the networks; 2. The controller according to claim 1, wherein the scheduler sets the restriction such that a total amount of packets transmitted from all of the buffers included in each of the networks is equal to or less than a bandwidth of each of the networks.

3. The scheduler The predetermined period is divided for each of the networks to obtain divided periods, In the above restriction, the product of the throughput of each of the networks and the predetermined period is set to the product of the throughput of each of the networks and the division period.

2. The controller of claim 1.

4. If the communication between the terminal and the access point is orthogonal frequency-division multiplexing (OFDM), The scheduler Divide each subcarrier available in the network into divided subcarriers for each network; In the above restriction, the product of the throughput of each of the networks and the predetermined period is defined as the product of the throughput of each of the networks when the subcarriers are divided and the predetermined period.

2. The controller of claim 1.

5. A controller according to any one of claims 1 to 4; a plurality of networks each having one of the access points and one or more of the terminals; A communication system comprising:

6. A method for controlling traffic of a plurality of networks, comprising: Each of the networks has one access point and one or more terminals, and transmits packets between the terminals and the access point; storing, at each predetermined period, an amount of packets stored in a buffer for each traffic flow that the terminal and the access point have; calculating a transmission schedule for packets to be transmitted from the buffer based on the stored packet amount for each predetermined period; When calculating the transmission schedule, adding a restriction so that a total amount of packets to be transmitted from all of the buffers included in the network does not exceed a product of a throughput of each of the networks and the predetermined period; and transmitting the transmission schedule to the terminal and the access point; A control method comprising the steps of:

7. A program for causing a computer to function as the controller according to any one of claims 1 to 4.

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