Control System, Control Method, Controller, and Program

Abstract

The purpose of the present disclosure is to control packet transmission for each buffer in accordance with a communication requirement of an application.　In order to achieve the above objective, a control system according to the present disclosure controls the traffic of a wireless network, wherein: the control system comprises a terminal and an access point for transmitting packets stored in a buffer to each other via the wireless network, and a controller for controlling transmission with respect to the terminal and the access point; and on the basis of the packet volumes stored in buffers of the terminal and the access point, and a communication requirement of an application associated with the buffers, the controller controls transmission of a packet between the terminal and the access point for each of said buffers.

Description

Technical Field

[0001] The present disclosure relates to a control system, a control method, a controller, and a program for allocating communication bandwidth within an access network.

Background Art

[0002] In recent years, consideration has been given to accommodating a plurality of services and applications having various network requirements on the same network infrastructure. To this end, it is necessary to guarantee the quality required by each service and application accommodated in the same NW in the End-End section from "terminal to terminal" or from "terminal to application server".

[0003] The End-End of a network can be divided into a wireless section and a wired section. 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 (Non-Patent Documents 1 and 2).

[0004] EDCA is control at the terminal (destination) unit, and it is difficult to perform packet transmission control in traffic flow units that enable quality control at the service and application units. By applying the technology described in Non-Patent Document 3, it becomes possible to perform packet transmission control in traffic flow units, and quality control at the service and application units can be realized.

[0005] On the other hand, the applications and their states used by devices corresponding to terminals such as smartphones, mobile phones, personal computers, and robots change every moment, and the required communication requirements also change accordingly.

[0006] In the technology described in Non-Patent Document 3, there is no function to follow the fluctuations in communication requirements as described above. Therefore, there is a possibility of performing scheduling that does not conform to the actual situation. For example, when the required bandwidth is larger than the bandwidth given by scheduling, it causes packet loss, delay, and jitter. Also, when the required bandwidth is smaller than the bandwidth given by scheduling, packet loss, delay, and jitter do not occur, but the bandwidth utilization efficiency of the wireless network decreases. From the above, the controller needs to grasp the changes in the communication requirements of the application accompanying the time change.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] To solve the above problems, the present disclosure aims to perform packet transmission control for each buffer according to the communication requirements of the application.

Means for Solving the Problems

[0009] To achieve the above object, the present disclosure performs packet transmission control based on the amount of packets accumulated in each buffer and the communication requirements of the application.

[0010] Specifically, the control system according to the present disclosure is a control system for controlling the traffic of a wireless network, including terminals and access points that transmit packets accumulated in the buffer to each other via the wireless network, and a controller that performs transmission control on the terminals and the access points, and is provided with the controller controls packet transmission between the terminal and the access point for each buffer based on the amount of packets accumulated in the buffers of the terminal and the access point and the communication requirements of the application associated with the buffer.

[0011] Specifically, the control method according to the present disclosure is a control method for controlling the traffic of a wireless network, the control method is transmission control performed by a controller on terminals and access points that transmit packets to each other via the wireless network, and based on the amount of packets accumulated in the buffers of the terminal and the access point and the communication requirements of the application associated with the buffer, controls packet transmission between the terminal and the access point for each buffer.

[0012] Specifically, the controller according to the present disclosure is a controller for controlling the traffic of a wireless network, The controller is a device that performs transmission control on terminals and access points that mutually transmit packets via the wireless network, and controls packet transmission between the terminal and the access point for each buffer based on the amount of packets accumulated in the buffers of the terminal and the access point and the communication requirements of the application associated with the buffer.

[0013] This disclosure is a program for causing a computer to function as the controller. The controller can also be realized by a computer and a program, and it is also possible to record the program on a recording medium or provide it through a network.

Advantages of the Invention

[0014] According to this disclosure, packet transmission control can be performed for each buffer according to the communication requirements of the application.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

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Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These examples are merely illustrative, and the present disclosure can be implemented in various modified forms based on the knowledge of those skilled in the art. In the present specification and drawings, components having the same reference numerals indicate the same components as each other.

[0017] (Basic Configuration) First, the basic configuration of the control system of the present embodiment will be described. FIG. 1 is a diagram for explaining the control system 300 of the present embodiment. The control system 300 is a control system that controls the traffic of the wireless network 15, including terminals 11 and access points 12 that transmit packets to each other via the wireless network 15, and a controller 13 that performs transmission control on the terminals 11 and the access points 12. It is provided with.

[0018] In the control system 300 of the present disclosure, each terminal 11 and access point 12 holds one or more flow unit buffer parts, which are associated with each application, and the controller 13 associates the buffer numbers of the flow unit buffer parts held by each terminal 11 and access point 12 in advance with the communication requirements for each application and records them in the database part. The controller 13 refers to the database part and controls the packet transmission between the terminal 11 and the access point 12 for each flow unit buffer part of the terminal 11 and the access point 12 based on the packet amount accumulated in the flow unit buffer part and the application (AP1) associated with the flow unit buffer parts (FB1, FB2).

[0019] Here, the communication requirements include the required bandwidth, required delay time, and required delay fluctuation time (required jitter) of the application associated with each of the flow unit buffer unit of the terminal 11 and the flow unit buffer unit of the access point 12. The required bandwidth is the communication bandwidth in the wireless network 15 necessary for executing the application AP1. In this embodiment, an example of realizing the required bandwidth using the transmission time is shown, but the required bandwidth in the present disclosure is not limited to the time axis and may be achieved using the wavelength axis. The required delay time is the allowable value of the packet delay time necessary for executing the application AP1. The required jitter is the allowable value of the packet delay fluctuation time necessary for executing the application AP1.

[0020] In the terminal 11, the application AP1 to be used changes at an arbitrary timing. Therefore, the present disclosure updates the information of the application associated with the flow unit buffer unit according to the application executed in the terminal 11. This update method is arbitrary. For example, the notification unit may notify the information of the application associated with the flow unit buffer unit to the controller 13. Further, the controller 13 may update the communication requirements stored in the database DB3 to new communication requirements based on an input signal from the outside. Furthermore, the controller 13 may add and store new communication requirements in the database DB3 based on an input signal from the outside.

[0021] (Embodiment 1) FIG. 2 is a diagram for explaining the control system of this embodiment. The control system 301 of this embodiment includes N terminals 11, an access point 12 that communicates with these terminals 11, and a controller 13 that allocates the communication bandwidth of the terminal 11 (hereinafter, the "communication bandwidth" is abbreviated as "bandwidth"). The terminal 11, the access point 12, and 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 through a network.

[0022] The control system 301 has a function of controlling packet transmission between the terminal 11 and the access point 12 based on notifications of the packet amounts from the terminal 11 and the access point 12. Specifically, it has the following configuration. The terminal 11 includes a main signal transceiver MTR1, a main signal buffer MB1, flow unit buffers FB1#1 to #L, applications AP1#1 to #L, a scheduler SCH1, a notifier NTF1, and a control signal transceiver CTR1. The access point 12 includes a main signal transceiver (lower) MTR2, a main signal buffer MB2, flow unit buffers FB2#1 to #K, a main signal transceiver (upper) MTRU, a notifier NTF2, a scheduler SCH2, and a control signal transceiver CTR2. The controller 13 includes a database unit DB3, a scheduling unit SCH3, and a control signal transceiver CTR3.

[0023] Each of the terminal 11 and the access point 12 has buffers (FB1, FB2) for accumulating transmission packets for each traffic flow, device-side transceivers (CTR1, CTR2) that transmit the accumulated amounts of the transmission packets for each traffic flow accumulated in the buffers (FB1, FB2) to the controller 13 and receive the transmission start timing and transmission time of the transmission packets for each traffic flow from the controller 13, and main signal transmitters (MTR1, MTR2) that transmit the transmission packets for each traffic flow in the buffers (FB1, FB2) to the wireless network 15 according to the transmission start timing and the transmission time. It is provided with.

[0024] The controller 13 has a control signal transceiver CTR3 that receives the accumulated amounts from each of the terminal 11 and the access point 12 and transmits the transmission start timing and the transmission time to each of the terminal 11 and the access point 12, A scheduling unit SCH3 that determines the transmission start timing and the transmission time of the transmission packet for each traffic flow based on the communication requirements of the application AP1 included in the terminal 11 and the accumulated amount received. It is provided with.

[0025] The control system 301 communicates a control signal between the controller 13 and the access point 12 / terminal 11 by a communication means different from the communication means of the main signal (traffic packet). Specifically, the control signal is transmitted and received between the control signal transmission / reception unit CTR1 of the terminal 11 and the control signal transmission / reception unit CTR3 of the controller 13, and between the control signal transmission / reception unit CTR2 of the access point 12 and the control signal transmission / reception unit CTR3 of the controller 13.

[0026] Each terminal 11 and access point 12 periodically notifies the controller 13 of the amount of packets accumulated in the flow unit buffer parts (FB1, FB2) using a control signal. The terminal 11 accumulates the packets transmitted from each application AP1 in the flow unit buffer part FB1 for each application (each flow). The notification unit NTF1 periodically checks the packet accumulation amount in each flow unit buffer part FB1, and notifies the controller 13 of the packet accumulation amount stored in each flow unit buffer part FB1 via the control signal transmission / reception unit CTR1 using a control signal. In the present disclosure, the control signal for notifying this packet accumulation amount is referred to as "packet amount notification". The packet amount notification also includes information on the terminal 11 or the access point 12 and information on the flow unit buffer parts (FB1, FB2). Note that the application AP1 may own the flow unit buffer part FB1.

[0027] Also, the access point 12 accumulates the packets from the upper network device 50 in the flow unit buffer part FB2 for each application (each flow). The notification unit NTF2 periodically checks the packet accumulation amount in each flow unit buffer part FB2, and notifies the controller 13 via the control signal transmission / reception unit CTR2 using a control signal.

[0028] The controller 13 records the notified packet accumulation amount, information on the terminal 11, the access point 12, and the flow unit buffer sections (FB1, FB2). Then, based on the communication requirements and packet accumulation amount of the application AP1 of the terminal 11, it determines the transmission start timing and transmission time for each flow unit buffer section (FB1, FB2), and notifies each terminal 11 and access point 12 using a control signal.

[0029] The control signal transceiver unit CTR3 of the controller 13 receives control signals from each terminal 11 and the access point 12, and arranges the information on the packet accumulation amount, terminal 11, access point 12, and flow unit buffer sections (FB1, FB2) included in the control signals in the database DB3. In addition, the controller 13 manages the communication requirements of the application AP1 in the database DB3.

[0030] Figure 3 is a diagram for explaining an example of the information arranged in the database DB3. This database DB3 arranges the following five pieces of information. The item number is a sequential number for all the flow unit buffer sections (FB1, FB2) of the terminal 11 and the access point 12. The node number is the number of the access point 12 or the terminal 11. The buffer number is the number of the flow unit buffer section FB1 held by each terminal 11, or the number of the flow unit buffer section FB2 held by the access point 12. The packet amount is the packet accumulation amount held by the flow unit buffer section having each buffer number. For example, item number K + 2 is the packet accumulation amount of the flow unit buffer section FB1#2 held by the terminal 11#1, and the amount being "B12" means that. The communication requirement is the communication requirement of the application AP1 associated with the flow unit buffer section (FB1, FB2). Note that in the communication requirements in Figure 3, "bandwidth" abbreviates "required bandwidth", "delay" abbreviates "required delay time", and "jitter" abbreviates "required jitter".

[0031] The scheduling unit SCH3 of the controller 13 uses the scheduling method described later to determine the transmission start timing and transmission time for each flow unit buffer unit from the contents of the database unit DB3. Then, the scheduling unit SCH3 transmits the determined transmission start timing and transmission time to the terminal 11 and the access point 12 from the control signal transmission / reception unit CTR3 using a control signal.

[0032] Each terminal 11 and access point 12 reads out the packet amount corresponding to the notified transmission time from the flow unit buffer units (FB1, FB2) at the notified transmission start timing and inputs it to the main signal buffer units (MB1, MB2). The main signal transmission / reception units (MTR1, MTR2) transmit the packets in the main signal buffer units (MB1, MB2) to the wireless network 15 over the notified transmission time.

[0033] FIG. 4 is a diagram illustrating the operation described above in a flowchart. The control method of the present embodiment is a control method for controlling the traffic of the wireless network 15, The control method according to the present disclosure is transmission control performed by the controller 13 for the terminal 11 and the access point 12 that mutually transmit packets via the wireless network 15, accumulating transmission packets for each traffic flow in the respective buffers (FB1, FB2) of the terminal 11 and the access point 12 (steps S111, S112, S121, S122), transmitting the accumulated amount of the transmission packets for each traffic flow accumulated in the respective buffers (FB1, FB2) to the controller 13 (steps S113, S123), at the controller 13, determining the transmission start timing and transmission time of the transmission packets for each traffic flow based on the accumulated amounts received from the terminal 11 and the access point 12 respectively (steps S131, S132), transmitting the transmission start timing and transmission time from the controller 13 to each of the terminal 11 and the access point 12 (step S133), and Transmit the transmission packets for each traffic flow from the respective buffers (FB1, FB2) of the terminal 11 and the access point 12 according to the transmission start timing and the transmission time to the wireless network 15 (steps S114, S124). It is characterized by this.

[0034] [Scheduling method] Here, the scheduling method performed by the scheduling unit SCH13 of the controller 13 will be described. An example of the scheduling of a control system 301 composed of two terminals 11#1 and 11#2 provided with flow unit buffer units FB1#1 to 3 and one access point 12 provided with flow unit buffer units FB2#1 to 3 is shown. For easy understanding, the throughput on the frequency axis of the wireless network 15 is fixed. Also, the controller 13 notifies the scheduler to the terminals 11#1 and 11#2 and the access point 12 every period T c shall be.

[0035] The database DB3 of this example is shown in FIG. 5. First, the scheduling unit SCH13 determines the minimum transmission time based on the required bandwidth of the communication requirements for each of the flow unit buffer units FB1 and FB2. For example, in the case of item number #7, the required bandwidth is RB 21 is. In this case, the scheduling unit SCH13 assigns the transmission time corresponding to RB 21 to item number #7. In this way, as shown in FIG. 6, the transmission time for each item number is assigned. Also, at the set throughput and transmission time, there may be a flow unit buffer unit FB1 or FB2 that cannot transmit the accumulated total packet amount. In this case, the scheduling unit SCH13 may schedule the remaining packet amount for the flow unit buffer unit FB1 or FB2 for which the total packet amount could not be transmitted in the next scheduling. Here, the scheduling unit SCH13 may calculate the remaining packet amount that could not be transmitted using the throughput, transmission time, and packet amount.

[0036] Also, for each of the flow unit buffer units FB1 and FB2, the scheduling unit SCH13 may allocate a transmission time shorter than the transmission time based on the required bandwidth, which allows the transmission of the accumulated packet amount, considering the packet amount and throughput. By allocating the transmission time according to the packet amount, more efficient scheduling can be performed.

[0037] Then, the scheduling unit SCH13 determines the transmission start timing of each flow unit buffer unit so that the transmission start timing of the flow unit buffer unit with a shorter required delay time for communication requirements comes first. For example, regarding the required delay time of each flow unit buffer unit shown in FIG. 5, RD 01 <RD 11 <RD 21 <RD 02 <RD 12 <RD 22 <RD 03 <RD 13 <RD 23 is assumed to hold. In this case, as shown in FIG. 6, the order of the transmission start timing is item number #1 (RD 01 ), item number #4 (RD 11 ), item number #7 (RD 21 ), item number #2 (RD 02 ), item number #5 (RD 12 ), item number #8 (RD 22 ), item number #3 (RD 03 ), item number #6 (RD 13 ), item number #9 (RD 23 ).

[0038] Also, for each flow unit buffer unit, the scheduling unit SCH13 determines the transmission start timing of each flow unit buffer unit so that the packet transmission interval in the same flow unit buffer unit, that is, the time from the transmission completion timing to the next transmission start timing, is equal to or less than the required jitter of the communication requirements. For example, for the flow unit buffer unit of item number #7 shown in FIG. 6, the time from the transmission completion timing t2 to the next transmission start timing t3 is the required jitter RJ 21Perform scheduling as follows. The same applies to the flow unit buffer parts of other item numbers. Here, when the transmission start timing does not satisfy the required jitter of the communication requirement due to the required delay time of the communication requirement, the scheduling unit SCH13 ignores the required delay time of the communication requirement and determines the transmission start timing so as to satisfy the required jitter of the communication requirement.

[0039] The communication requirements of an application may change over time. For example, in the case of video communication, when the change in the video is large, the amount of packets to be communicated increases, but when the change in the video is small, the amount of packets to be communicated decreases. In such a case, it is conceivable that the communication requirements change depending on the time even for the same application. Therefore, the control system 301 according to the present embodiment may include a monitoring unit that detects that the communication requirements have changed. It is possible to deal with the changed communication requirements by the following method.

[0040] For example, the application AP1 of the terminal 11 may function as a monitoring unit. In this case, when the communication requirements of the application 11 change, the application 11 may notify the changed communication requirements to the controller 13 through the notification unit NTF1.

[0041] Since there is an application manager that controls and monitors an application depending on the application, the application manager may function as a monitoring unit. In this case, the application manager may detect that the communication requirements of the application have changed, and the application manager may directly notify the changed communication requirements to the controller 13.

[0042] In the terminal 11 such as a robot, there are things whose state changes can be objectively known. Therefore, in order to objectively detect the state change, the terminal 11 may include various sensors such as an acceleration sensor and a thermosensor, or a camera as a monitoring unit. The terminal 11 indirectly confirms its own state change from these various sensors or the camera, and notifies the controller 13 of the communication requirements changed due to the state change.

[0043] In a wireless network, it is possible to monitor traffic. Therefore, the control system may further include a network monitoring unit as a monitoring unit. The network monitoring unit checks for changes in traffic and notifies the controller 13 of the changed communication requirements. Specific examples of changes in traffic include, for example, throughput, delay time, jitter, packet loss, etc. Here, it is presumed that an application or the like has changed along with the change in the traffic, and the communication requirements corresponding to the presumed application or the like are notified to the controller 13.

[0044] When the controller 13 receives a notification from the above-described monitoring unit, it updates the communication requirements stored in the database to the notified communication requirements. An example of the update of the communication requirements will be described with reference to FIG. 5. For example, assume that the amount of packets transmitted by the application AP1#1 associated with the flow unit buffer FB1#1 of the terminal 11#1 described in item number 4 has increased rapidly. Along with this, assume that the required bandwidth of the application AP1#1 has changed from RB 11 to RB' 11 In this case, the controller 13 receives a notification from the terminal 11#1 that the required bandwidth in item number 4 has changed from RB 11 to RB' 11 and updates the required bandwidth in item number 4 of the database DB3 from RB 11 to RB' 11

[0045] ​In the conventional control system, the controller 13 performed scheduling based only on the amount of packets accumulated in the flow unit buffer sections of the terminal 11 and the access point 12. Therefore, in the conventional control system, when the communication requirements were changed, scheduling could not be performed corresponding to the changed communication requirements. However, in the present disclosure, since the controller 13 manages the communication requirements of the application in association with the flow unit buffer section, scheduling can be performed in consideration of the communication requirements. Therefore, as shown in FIG. 7, even if the application used by the terminal 11#1 is changed from the application AP1 to AP2 and the communication requirements are changed from the communication requirements #1 to the communication requirements #2, scheduling can be performed so as to satisfy the communication requirements #2.

[0046] As described above, according to the present disclosure, packet transmission control can be performed for each buffer according to the communication requirements of the application.

Industrial Applicability

[0047] The present disclosure can be applied to the information and communication industry.

Explanation of Signs

[0048] 11: Terminal 12: Access Point 13: Controller 15: Wireless Network 50: Upper Network Device 300, 301: Control System

Claims

1. A control system for controlling traffic in a wireless network, comprising: terminals and access points that transmit packets stored in a buffer to each other via the wireless network; a controller that performs transmission control on the terminals and the access points; wherein the controller manages all buffers of the terminals and the access points in flow units, and schedules the transmission start timing and transmission time of packets in each buffer based on the amount of packets stored in each buffer of the terminals and the access points and the communication requirements of the applications associated with each buffer; characterized in that, further when there is a change in the communication requirements of the application, the terminal notifies the controller of the changed communication requirements; the controller updates, for each buffer of the terminals and the access points, a database storing the amount of packets stored in the buffer and the communication requirements of the application associated with the buffer, with the communication requirements notified from the terminal; A control system characterized by the above.

2. A control system for controlling traffic in a wireless network, comprising: terminals and access points that transmit packets stored in a buffer to each other via the wireless network; a controller that performs transmission control on the terminals and the access points; wherein the controller manages all buffers of the terminals and the access points in flow units, and schedules the transmission start timing and transmission time of packets in each buffer based on the amount of packets stored in each buffer of the terminals and the access points and the communication requirements of the applications associated with each buffer; characterized in that, further it comprises a network monitoring unit that monitors the traffic in the wireless network, estimates a change in the communication requirements of the application from the change in the traffic when there is a change in the traffic, and notifies the controller of the changed communication requirements; The controller updates, for each buffer of the terminal and the access point, a database storing the amount of packets accumulated in the buffer and the communication requirements of the application associated with the buffer, with the communication requirements notified from the network monitoring unit. A control system characterized by the above.

3. The communication requirements include a required jitter indicating an allowable value of the delay fluctuation time of packets required to execute the application, and the controller performs scheduling so that the packet transmission interval accumulated in the buffer associated with the same application is equal to or less than the required jitter. The control system according to claim 1 or 2, characterized by the above.

4. The communication requirements include the required bandwidth and required delay time of the application, and the controller allocates the required bandwidth of the application to each buffer in ascending order of the required delay time of the application. The control system according to claim 3, characterized by the above.

5. A control method for controlling the traffic of a wireless network, wherein the control method is transmission control performed by a controller for a terminal and an access point that mutually transmit packets via the wireless network, managing all buffers of the terminal and the access point in flow units, and scheduling the transmission start timing and transmission time of packets in each buffer based on the amount of packets accumulated in each buffer of the terminal and the access point and the communication requirements of the application associated with each buffer. Characterized by the above, and further when there is a change in the communication requirements of the application, the terminal notifies the controller of the changed communication requirements, and the controller updates, for each buffer of the terminal and the access point, a database storing the amount of packets accumulated in the buffer and the communication requirements of the application associated with the buffer, with the communication requirements notified from the terminal. A control method characterized by the above.

6. A control method for controlling the traffic of a wireless network, wherein the control method is transmission control performed by a controller for a terminal and an access point that mutually transmit packets via the wireless network, managing all buffers of the terminal and the access point in flow units, and scheduling the packet transmission start timing and transmission time of each of the buffers based on the packet amount stored in each of the buffers of the terminal and the access point and the communication requirements of the application associated with each of the buffers characterized in that, further a network monitoring unit monitors the traffic of the wireless network, and when there is a change in the traffic, estimates a change in the communication requirements of the application from the change in the traffic and notifies the controller of the communication requirements after the change; the controller updates, for each buffer of the terminal and the access point, a database storing the packet amount stored in the buffer and the communication requirements of the application associated with the buffer to the communication requirements notified from the network monitoring unit A control method characterized by the above.

7. A controller for controlling the traffic of a wireless network, wherein the controller is a device that performs transmission control on a terminal and an access point that mutually transmit packets via the wireless network, and manages all buffers of the terminal and the access point in flow units, and schedules the packet transmission start timing and transmission time of each of the buffers based on the packet amount stored in each of the buffers of the terminal and the access point and the communication requirements of the application associated with each of the buffers characterized in that, further when there is a change in the communication requirements of the application, the terminal notifies the controller of the communication requirements after the change; the controller updates, for each buffer of the terminal and the access point, a database storing the packet amount stored in the buffer and the communication requirements of the application associated with the buffer to the communication requirements notified from the terminal A controller characterized by the above.

8. A controller for controlling the traffic of a wireless network, wherein the controller is a device that performs transmission control on a terminal and an access point that mutually transmit packets via the wireless network, managing all the buffers of the terminal and the access point in flow units, and scheduling the packet transmission start timing and transmission time of each buffer based on the packet amount stored in each buffer of the terminal and the access point and the communication requirements of the application associated with each buffer is characterized in that, furthermore a network monitoring unit monitors the traffic of the wireless network, and when there is a change in the traffic, estimates a change in the communication requirements of the application from the change in the traffic and notifies the controller of the communication requirements after the change; the controller updates, for each buffer of the terminal and the access point, a database storing the packet amount stored in the buffer and the communication requirements of the application associated with the buffer with the communication requirements notified from the network monitoring unit A controller characterized by the above.

9. A program for causing a computer to function as the controller according to Claim 7 or 8.

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