Communication system, communication control device, control circuit, storage medium, and communication control method

Abstract

This communication system including a first wireless section and a second wireless section is characterized by comprising routers (6-1, 6-2) each serving as a first proxy which is installed at a pre-stage of the first wireless section and which has a function of controlling a first window size that is the amount of data to be transmitted at once towards the first wireless section and a gateway (3) serving as a second proxy which can communicate with the first proxy via the second wireless section and which has a function of controlling a second window size that is the amount of data to be transmitted at once towards the first proxy, and is characterized in that the second proxy predicts the future buffer state of the first proxy and determines the second window size on the basis of the prediction.

Description

Technical Field

[0001] The present disclosure relates to a communication system, a communication control device, a control circuit, a storage medium, and a communication control method for transmitting data via a plurality of wireless sections.

Background Art

[0002] In TCP (Transmission Control Protocol) communication, the window size, which is the amount of data transmitted at one time by a congestion control algorithm, is controlled. Usually, in TCP communication, the congestion state of the network is determined by a delivery confirmation called an ack that is returned from the destination device to the source device. Therefore, when a wireless section with a large delay, such as a satellite line, is included in the communication path from the source device to the destination device, the window size is set low and the line cannot be effectively utilized. Also, when the communication environment in the wireless section is poor and packets are dropped, congestion is determined to have occurred and the window size is set low, and it takes a long time for the window size to recover again.

[0003] In response to such problems, for example, in Non-Patent Document 1, a method of installing a proxy that returns an ack instead of the destination device is proposed in front of the wireless section. When the source device receives an ack from the proxy, it determines that there is no congestion and increases the window size. The proxy re-sets the window size for the wireless section. At this time, the base station notifies the proxy of the amount of data accumulated in the buffer of the base station, and the proxy sets the window size so that congestion does not occur at the base station.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] However, when attempting to apply the above conventional technology in a system with multiple radio intervals, there is a problem that it is difficult to avoid congestion while effectively utilizing the line. When using a proxy in a communication system with multiple radio intervals, it is necessary to install a proxy for each radio interval and determine the window size from the proxy to the radio interval. In this case, between the proxies, the buffer state of one proxy is notified to the other proxy, and the window size is determined based on the notified buffer state. At this time, there will be a radio interval between multiple proxies, and the notification of the buffer state will be performed via the radio interval. For this reason, a delay occurs in the notification of the buffer state, and at the time of transmitting data, since the buffer state is different from that notified, it may not be possible to determine an appropriate window size and congestion may occur.

[0006] The present disclosure has been made in view of the above, and an object thereof is to obtain a communication system capable of avoiding congestion while effectively utilizing the line even when there are multiple radio intervals. Means for Solving the Problems

[0007] In order to solve the above-described problems and achieve the object, a communication system according to the present disclosure is a communication system including a first wireless section and a second wireless section, and includes a first proxy installed in front of the first wireless section and having a function of controlling a first window size which is the amount of data transmitted at a time toward the first wireless section, and a second proxy communicable with the first proxy via the second wireless section and having a function of controlling a second window size which is the amount of data transmitted at a time toward the first proxy. The first proxy transmits a control signal including information indicating the current buffer state of the first proxy and a parameter that affects the future buffer state of the first proxy to the second proxy, The second proxy Based on the control signal transmitted from the first proxy, is characterized by predicting a future buffer state of the first proxy and determining the second window size based on the prediction result.

Advantages of the Invention

[0008] The communication system according to the present disclosure has an effect that even when there are a plurality of wireless sections, it is possible to avoid congestion while effectively using the line.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0010] Hereinafter, a communication system, a communication control device, a control circuit, a storage medium, and a communication control method according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0011] Embodiment 1. FIG. 1 is a diagram showing a configuration example of a communication system 10 according to Embodiment 1. The communication system 10 includes a TCP communication device 1, a 5G core device 2, a gateway 3, relay terminals 4-1, 4-2, 4-3, a relay station 5, routers 6-1, 6-2, base stations 7-1, 7-2, and terminals 8-1, 8-2. There are wireless connections between the gateway 3 and the relay station 5, between the relay station 5 and each of the routers 6-1, 6-2, between the base station 7-1 and the terminal 8-1, and between the base station 7-2 and the terminal 8-2.

[0012] The communication system 10 is an example of a system including a plurality of wireless sections. The wireless section between the base stations 7-1, 7-2 and the terminals 8-1, 8-2 is an example of a first wireless section, and the wireless section between the routers 6-1, 6-2 and the gateway 3 is an example of a second wireless section.

[0013] The base stations 7-1, 7-2 provide a wireless communication environment for the terminals 8-1, 8-2. Here, the relay station 5 is assumed to be a communication satellite, but it may be a moving body staying at a high altitude.

[0014] The terminals 8-1, 8-2 are mobile stations that wirelessly connect to the base stations 7-1, 7-2. The first wireless section is, here, a wireless communication section between the base stations 7-1, 7-2 and the terminals 8-1, 8-2 which are mobile stations, and the second wireless section is a part of a backhaul line that connects the base stations 7-1, 7-2 and the core network.

[0015] Note that the configuration shown in FIG. 1 is an example, and the technology of this embodiment is applicable to a system that includes a plurality of wireless sections and performs congestion control by controlling the window size. In this embodiment, the communication system 10 is a fifth-generation mobile communication (hereinafter referred to as 5G) system. Due to the increasing communication demand in recent years, 5G, which enables large-capacity communication, has been introduced and is being widely used. While the frequency band used in the 5G system enables large-capacity data communication, it has a large attenuation, and compared with the 4G wireless access network, it is necessary to install a large number of base stations. For this reason, in the 5G system, it is necessary to provide an inexpensive and efficient backhaul line that connects the base station and the core network. Conventionally, the backhaul line has generally been composed of optical fibers, but a method of configuring the backhaul line wirelessly is being standardized as IAB (Integrated Access and Backhaul). Furthermore, in recent years, with the spread of IoT (Internet of Things), in the 5G system, provision of a communication environment for things is required, and a more flexible access environment is needed than ever. A use case of mounting a base station on a mobile body is also considered, and in this case as well, wirelessization of the backhaul line is required.

[0016] As described above, the use cases in which the 5G system is used are diversified, and as part of the function expansion of the 5G system, connection with non-terrestrial networks (NTN: Non Terrestrial Network) such as satellites and HAPS (High Altitude Platform Station) is expected. The connection form between the 5G system and the satellite system has been discussed by ITU-R (International Telecommunication Union-Radio communication sector), 3GPP (registered trademark) (Third Generation Partnership Project), etc. As shown in FIG. 1, a method of connecting the backhaul line between the base stations 7-1 and 7-2 and the 5G core device 2 with a satellite is also being considered. In addition, a mobile direct method in which the 5G terminal and the satellite directly communicate is also being considered.

[0017] In the communication system 10, a backhaul connection is established between the base stations 7-1 and 7-2 and the 5G core device 2 using a satellite link with a large delay, and TCP communication is performed. In this case, when performing TCP communication between the TCP communication device 1 and the terminal 8-1 or between the TCP communication device 1 and the terminal 8-2, it will pass through a plurality of radio sections. In normal TCP communication, for example, when the TCP communication device 1 sends data to the terminal 8-1, the TCP communication device 1, which is the source device, determines the congestion state of the network based on the ack returned from the terminal 8-1, which is the destination device. In this case, if a satellite link with a large delay is passed through on the path to the destination device, the delay until the ack is returned from the destination device will increase. On the other hand, in the communication system 10, a proxy that returns an ack instead of the destination device is installed in front of each radio section. The routers 6-1 and 6-2 are examples of proxies installed in front of the first radio section. The gateway 3 is an example of a proxy installed in front of the second radio section. Therefore, when the TCP communication device 1 sends data to the terminal 8-1, the gateway 3 returns an ack instead of the terminal 8-1, which is the destination device. Therefore, the TCP communication device 1 can perform data transmission without reducing the window size. The data received by the gateway 3 from the TCP communication device 1 is then transmitted to the router 6-1 via the second radio section, and then transmitted from the router 6-1 to the terminal 8-1 via the base station 7-1. At this time, the gateway 3 and the router 6-1 temporarily store the received data and perform buffering to transmit the temporarily stored data according to the determined window size. The control of the window size will be described later.

[0018] Note that the configurations and functions of the TCP communication device 1, 5G core device 2, relay terminals 4-1 to 4-3, relay stations 5, base stations 7-1, 7-2, and terminals 8-1, 8-2 are common and do not have configurations or functions specific to this embodiment. Therefore, detailed descriptions thereof are omitted. Hereinafter, the detailed configurations of the gateway 3 and routers 6-1, 6-2 will be described. Also, in FIG. 1, for a plurality of devices having the same configuration and function, different numbers are appended after a common reference numeral with a hyphen to distinguish each device. However, hereinafter, when it is not necessary to distinguish each of the plurality of devices, or when describing matters common to the plurality of devices, only the common reference numeral may be shown. For example, when it is not necessary to distinguish each of the routers 6-1, 6-2, and when describing matters common to the routers 6-1, 6-2, they are simply referred to as router 6.

[0019] FIG. 2 is a diagram showing the functional configuration of router 6 according to Embodiment 1. Router 6 includes a transmission unit 61, a reception unit 62, a storage unit 63, a transmission window control unit 64, and a control signal transmission unit 65.

[0020] The transmitting unit 61 has a function of transmitting data to an external device. The receiving unit 62 has a function of receiving data from an external device. The storage unit 63 has a buffer function of temporarily storing the data received from the external device. The transmission window control unit 64 determines the window size, which is the amount of data to be transmitted at one time, when transmitting data from the router 6 to the external device. Note that the window size when the router 6 transmits data toward the first wireless section is referred to as the first window size. The transmitting unit 61 transmits data according to the window size determined by the transmission window control unit 64. The transmission window control unit 64 may determine the window size using an ack returned from the destination device, like in conventional general TCP communication, or may determine the window size based on the line quality between the base station 7 and the terminal 8. As a method of determining the window size based on the line quality, for example, as described in Japanese Unexamined Patent Application Publication No. 2018-85642, a method of previously determining the correspondence between the radio wave intensity and the window size and using the window size corresponding to the radio wave intensity can be used.

[0021] The control signal transmitting unit 65 transmits a control signal including information on the amount of data in the storage unit 63, that is, information on the buffer state, to the gateway 3. The control signal can include information indicating the current buffer state of the storage unit 63 in the router 6 and a parameter that affects the future buffer state of the storage unit 63. The parameter that affects the future buffer state is, for example, the window size determined by the transmission window control unit 64 of the router 6, the line quality between the base station 7 and the terminal 8, the number of terminals 8 connected to the base station 7, and the like. The control signal transmitting unit 65 periodically transmits the control signal to the gateway 3 as long as data is stored in the storage unit 63. Here, the router 6 is described as a device separate from the base station 7, but the function of the router 6 may be incorporated in the base station 7.

[0022] FIG. 3 is a diagram showing the functional configuration of the gateway 3 according to Embodiment 1. The gateway 3 includes a transmission unit 31, a reception unit 32, a storage unit 33, an Ack transmission unit 34, an Ack termination unit 35, and a transmission window control unit 36.

[0023] The transmission unit 31 has a function of transmitting data to an external device. The reception unit 32 has a function of receiving data from an external device. The storage unit 33 has a buffer function of temporarily storing the data received from the external device. The Ack transmission unit 34 returns an ack for the data received from the TCP communication device 1 which is the source device. The Ack termination unit 35 terminates the ack returned from the terminal 8 which is the destination device. The transmission window control unit 36 determines a second window size which is the window size when the gateway 3 transmits data to the router 6 via the second radio section. The gateway 3 temporarily stores the data received by the reception unit 32 from the TCP communication device 1 in the storage unit 33, and transmits the data in the storage unit 33 to the router 6 using the transmission unit 31 according to the second window size determined by the transmission window control unit 36. The transmission window control unit 36 predicts the future buffer state of the router 6 based on the control signal received from the router 6, and determines the second window size based on the prediction result.

[0024] The data received by the gateway 3 is of three types: data transmitted from the TCP communication device 1, a control signal transmitted from the router 6, and an ack transmitted from the terminal 8 which is the destination device via the router 6. The data transmitted from the TCP communication device 1 is temporarily stored in the storage unit 33 as described above. The control signal from the router 6 is used in the transmission window control unit 36 to predict the future buffer state and determine the second window size. Regarding the ack transmitted from the terminal 8 which is the destination device via the router 6, since the ack has already been returned to the TCP communication device 1 which is the source device by the Ack transmission unit 34, it is terminated by the Ack termination unit 35 in the gateway 3.

[0025] Here, each of the router 6 shown in FIG. 2 and the gateway 3 shown in FIG. 3 may be configured as a single circuit or device, or a plurality of functional units may be configured as one circuit or device. Also, each part may be realized by a control circuit including a memory and a processor that executes a program stored in the memory, or may be realized by dedicated hardware.

[0026] FIG. 4 is a diagram showing an example of the hardware that realizes the router 6 and the gateway 3 according to Embodiment 1. The control circuit 90 shown in FIG. 4 includes an input unit 91, a processor 92, a memory 93, and an output unit 94. The input unit 91 receives a signal from the outside. The output unit 94 outputs a signal from the control circuit 90 to the outside. The processor 92 is, for example, a CPU (Central Processing Unit), a central processing device, a processing device, an arithmetic device, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), or the like. The memory 93 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), an EEPROM (registered trademark) (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disk), or the like.

[0027] When the functions of the router 6 and the gateway 3 are realized by the control circuit 90, it is realized by the processor 92 reading and executing a program corresponding to the processing of each component stored in the memory 93. Also, the memory 93 is also used as a temporary memory in each process executed by the processor 92. The program executed by the processor 92 may be provided in a state stored in a storage medium, or may be provided via a communication path such as the Internet.

[0028] In addition, when the functions of the router 6 and the gateway 3 are realized using dedicated hardware, the dedicated hardware is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

[0029] Furthermore, the functions of the router 6 and the gateway 3 may be realized by combining the control circuit 90 and dedicated hardware. Note that the division of the functional units shown in FIGS. 2 and 3 is an example, and there is no particular limitation on the correspondence between the functional units and the hardware used to realize their functions. For example, one functional unit may be realized by a plurality of control circuits 90 or dedicated hardware, or a plurality of functional units may be realized by one control circuit 90 or dedicated hardware.

[0030] FIG. 5 is a sequence diagram showing the data flow of the communication system 10 according to Embodiment 1. Here, as an example, the case of transmitting data from the TCP communication device 1 to the terminal 8-1 via the router 6-1 will be described.

[0031] The TCP communication device 1, which is the source device, transmits data addressed to the terminal 8-1 toward the gateway 3 (step S1). The Ack transmission unit 34 of the gateway 3 returns an ack to the TCP communication device 1, which is the source device (step S2). Since the router 6-1 and the gateway 3 are connected by a satellite line, the delay until an ack is returned from the destination device, the terminal 8-1, becomes large. Therefore, when the TCP communication device 1, which is the source device, determines the window size based on the ack from the destination device, the window size is kept low. Thus, by returning an ack to the TCP communication device 1, which is the source device, at the gateway 3, the TCP communication device 1 can transmit data without reducing the window size.

[0032] The gateway 3 transmits the data received from the TCP communication device 1 to the router 6-1 via the second radio section using the set window size (step S3).

[0033] The router 6-1 that has received the data from the gateway 3 determines the first window size, which is the window size for transmission from the router 6-1 to the base station 7-1, i.e., the first radio section, based on the delay state of the ack returned from the terminal 8-1, the communication quality between the base station 7 and the terminal 8, etc. (step S4). The router 6-1 transmits the data received from the gateway 3 to the terminal 8-1 via the base station 7-1 according to the calculated first window size (step S5). Also, the router 6-1 generates a control signal and transmits it to the gateway 3 (step S6).

[0034] The gateway 3 that has received the control signal predicts the future buffer state of the router 6-1 based on the control signal and determines the second window size based on the prediction result (step S7). Thereafter, data is transmitted from the gateway 3 to the router 6-1 according to the determined second window size (step S8).

[0035] As described above, the communication system 10 according to Embodiment 1 includes a first wireless section and a second wireless section, and includes a router 6 which is a first proxy installed in front of the first wireless section, and a gateway 3 which is a second proxy installed in front of the second wireless section and can communicate with the router 6 via the second wireless section. The router 6 has a function of controlling a first window size which is the amount of data transmitted at a time toward the first wireless section. The gateway 3 has a function of controlling a second window size which is the amount of data transmitted at a time toward the router 6. The gateway 3 predicts the future buffer state of the router 6 and determines the second window size based on the prediction result. When the communication system 10 includes a plurality of wireless sections, since the buffer state information notified from the router 6 is transmitted via a wireless section with a large delay, a delay occurs and the information becomes old, and when appropriate window size control cannot be performed, it may lead to network congestion. However, by having the above-described configuration, in the gateway 3, the window size is controlled based on the prediction result of the future buffer state of the router 6, so that even when there are a plurality of wireless sections, it is possible to avoid congestion while effectively using the line.

[0036] Note that the gateway 3 can predict the future buffer state based on a control signal transmitted from the router 6. At this time, the router 6 transmits a control signal including information indicating the current buffer state of the router 6 and parameters that affect the future buffer state to the gateway 3. Further, the router 6 can transmit a control signal including the first window size determined by the router 6 as a parameter that affects the future buffer state to the gateway 3. Further, examples of the parameters that affect the future buffer state include, in addition to the first window size determined by the router 6, the line quality between the base station 7 and the terminal 8, the number of terminals 8 connected to the base station 7, and the like.

[0037] The first wireless section is a wireless communication section between the base station 7 and the terminal 8 which is a mobile station, and the second wireless section can be a part of a backhaul line connecting the base station 7 and the core network. As described above, particularly in a 5G system, wireless backhaul lines are required, and by making the backhaul line wireless, it becomes possible to provide a flexible access environment.

[0038] Also, in Embodiment 1, the relay station 5 constituting the second wireless section is a communication satellite, but the second wireless section is not limited to a high-altitude communication platform such as a communication satellite or HAPS, or mobile objects on the ground such as drones and ships, and may be configured by a non-terrestrial network which is a system that multi-layerly connects all mobile objects from the sea, air, to space.

[0039] Also, according to Embodiment 1, in the communication system 10 including the first wireless section and the second wireless section, a router having a function of controlling a first window size which is the amount of data transmitted at one time toward the first wireless section and is installed in front of the first wireless section, and a gateway 3 which is a communication control device capable of communicating via the second wireless section can also be provided. The gateway 3 is characterized by including a transmission window control unit 36 that predicts the future buffer state of the router 6 and determines a second window size which is the amount of data transmitted at one time toward the router 6 based on the prediction result.

[0040] Also, according to Embodiment 1, in the communication system 10 including the first wireless section and the second wireless section, a control circuit for controlling a router 6 which is a first proxy having a function of controlling a first window size which is the amount of data transmitted at one time toward the first wireless section and is installed in front of the first wireless section, and a gateway 3 which is a second proxy capable of communicating via the second wireless section can be provided. This control circuit can cause the gateway 3 to execute a step of predicting the future buffer state of the router 6 and a step of determining a second window size which is the amount of data transmitted at one time toward the router 6 based on the prediction result of the future buffer state.

[0041] Also, according to Embodiment 1, in the communication system 10 including the first wireless section and the second wireless section, a storage medium storing a program for controlling the gateway 3, which is a second proxy capable of communicating with the router 6, which is a first proxy installed in front of the first wireless section and having a function of controlling a first window size, which is the amount of data transmitted to the first wireless section at one time, can be provided. The program stored in this storage medium can cause the gateway 3 to perform a step of predicting the future buffer state of the router 6 and a step of determining a second window size, which is the amount of data transmitted to the router 6 at one time, based on the prediction result of the future buffer state.

[0042] Also, according to Embodiment 1, in the communication system 10 including the first wireless section and the second wireless section, the router 6, which is a first proxy installed in front of the first wireless section and having a function of controlling a first window size, which is the amount of data transmitted to the first wireless section at one time, and the gateway 3, which is a second proxy capable of communicating with the first wireless section via the second wireless section, can include a step of predicting the future buffer state of the router 6 and a step of the gateway 3 determining a second window size, which is the amount of data transmitted to the router 6 at one time, based on the prediction result of the future buffer state.

[0043] Embodiment 2. FIG. 6 is a diagram showing a configuration example of a communication system 10A according to Embodiment 2. The communication system 10A includes a TCP communication device 1, a 5G core device 2, a gateway 3, relay terminals 4-1, 4-2, 4-3, relay stations 5-1, 5-2, 5-3, routers 6A-1, 6A-2, base stations 7-1, 7-2, and terminals 8-1, 8-2. The communication system 10A has three relay stations 5-1, 5-2, 5-3, whereas there was one relay station 5 in the communication system 10, and has routers 6A-1, 6A-2 instead of the routers 6-1, 6-2 of the communication system 10. Hereinafter, differences from Embodiment 1 will be mainly described.

[0044] The relay stations 5-1, 5-2, and 5-3 are geostationary satellites, low-earth orbit satellites, HAPS, etc. Between the gateway 3 and the router 6A, one of the relay stations 5-1, 5-2, and 5-3 is passed through, and there will be multiple relay paths. When the altitudes of the relay stations 5-1, 5-2, and 5-3 are different from each other, the delay time is different for each relay path. In the communication system 10A, depending on the allowable delay of data, data size, etc., the gateway 3 selects an appropriate path and performs data transmission to each router 6A-1, 6A-2.

[0045] Figure 7 is a diagram showing a functional configuration example of the router 6A according to Embodiment 2. The router 6A includes a transmission unit 61, a reception unit 62, a storage unit 63, a transmission window control unit 64, a control signal transmission unit 65, and a control signal transmission path calculation unit 66. Since the functions of the transmission unit 61, the reception unit 62, the storage unit 63, the transmission window control unit 64, and the control signal transmission unit 65 are the same as those of the router 6, detailed descriptions thereof are omitted here. The data transmitted from the gateway 3 to the router 6A reaches the router 6A through different relay paths. At this time, the control signal transmission path calculation unit 66 of the router 6A can measure the delay time between the gateway 3 and the router 6A based on the timestamp added to the data transmitted by the gateway 3. The control signal transmission path calculation unit 66 selects the relay path with the smallest delay time based on the measured delay time, and notifies the selected relay path to the control signal transmission unit 65. The control signal transmission unit 65 transmits the control signal using the notified relay path. Here, the control signal transmission path calculation unit 66 measures the delay time and selects the relay path, but a path with the minimum delay time may be stored in advance.

[0046] In addition, when the gateway 3 receives a control signal from the router 6A, it can determine how old the buffer information included in the control signal is by using the delay information of the relay path. If the delay of the relay path for transmitting the control signal is large and the buffer information of the router 6A is old, it is highly likely that the buffer amount fluctuates greatly. If the delay of the relay path for transmitting the control signal is small, it is highly likely that the change in the buffer information of the router 6A is small. In this way, by predicting the future buffer amount of the router 6A in consideration of the delay time of the relay path for transmitting the control signal, the prediction accuracy can be further improved, and it becomes possible to avoid congestion with higher accuracy.

[0047] As described above, according to the communication system 10A according to the second embodiment, the same effects as those of the first embodiment can be achieved. Further, in the communication system 10A, the second wireless section includes a plurality of relay paths, and the router 6A, which is the first proxy, can select a path for transmitting a control signal based on the delay time of each of the plurality of relay paths. Thereby, the delay of the control signal transmitted from the router 6A to the gateway 3 can be minimized as much as possible, so that it becomes possible to improve the prediction accuracy of the future buffer state, and it becomes possible to avoid congestion while effectively using the line with higher accuracy.

[0048] In addition, the router 6A, which is the first proxy, can measure the delay time in the relay path based on the timestamp added to the transmission data by the gateway 3, which is the second proxy, and select a relay path for transmitting the control signal based on the measured delay time. This delay time can be used when the gateway 3, which is the second proxy, determines the second window size. The gateway 3 may determine the second window size based on the delay time in the second wireless section in addition to the control signal. Thereby, it becomes possible to improve the prediction accuracy of the future buffer state of the router 6A, and it becomes possible to avoid congestion while effectively using the line with higher accuracy.

[0049] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine the embodiments with each other, or omit or modify a part of the configuration without departing from the gist.

[0050] For example, in the above, as an example of a communication system including a plurality of radio intervals, the communication systems 10 and 10A including the first radio interval and the second radio interval are shown. However, the technologies of the above embodiments can be applied to a system including three or more radio intervals. Further, the system to which the technology is applied is not limited to a 5G system. Also, the second radio interval is not limited to a satellite line. The technologies of Embodiments 1 and 2 are suitable for a system including a radio interval with a relatively large delay.

Explanation of Reference Numerals

[0051] 1 TCP communication device, 2 5G core device, 3 gateway, 4-1, 4-2, 4-3 relay terminal, 5, 5-1, 5-2, 5-3 relay station, 6, 6-1, 6-2, 6A, 6A-1, 6A-2 router, 7-1, 7-2 base station, 8-1, 8-2 terminal, 10, 10A communication system, 31, 61 transmission unit, 32, 62 reception unit, 33, 63 storage unit, 34 Ack transmission unit, 35 Ack termination unit, 36, 64 transmission window control unit, 65 control signal transmission unit, 66 control signal transmission path calculation unit, 90 control circuit, 91 input unit, 92 processor, 93 memory, 94 output unit.

Claims

1. A communication system including a first radio section and a second radio section, a first proxy installed in front of the first radio section and having a function of controlling a first window size which is the amount of data transmitted at one time toward the first radio section, a second proxy communicable with the first proxy via the second radio section and having a function of controlling a second window size which is the amount of data transmitted at one time toward the first proxy, comprising: the first proxy transmits a control signal including information indicating the current buffer state of the first proxy and a parameter affecting the future buffer state of the first proxy to the second proxy, the second proxy predicts the future buffer state of the first proxy based on the control signal transmitted from the first proxy, and determines the second window size based on the prediction result. A communication system characterized by this.

2. The communication system according to claim 1, wherein the first proxy transmits the control signal including the first window size determined by the first proxy as a parameter affecting the future buffer state to the second proxy.

3. The second radio section includes a plurality of paths, The communication system according to claim 1, wherein the first proxy selects a path for transmitting the control signal based on the delay time of each of the plurality of paths.

4. The communication system according to claim 3, wherein the first proxy measures the delay time in the path based on a time stamp added to the transmission data by the second proxy, and selects a path for transmitting the control signal based on the measured delay time.

5. The communication system according to claim 1, wherein the second proxy determines the second window size based on the delay time in the second radio section in addition to the control signal.

6. The first radio section is a radio communication section between a base station and a mobile station, The communication system according to claim 1, wherein the second radio section is a part of a backhaul line connecting the base station and the core network.

7. The communication system according to claim 1, wherein the second radio section is constituted by a non-terrestrial network.

8. In a communication system including a first radio section and a second radio section, a router installed in front of the first radio section and having a function of controlling a first window size which is the amount of data transmitted at a time toward the first radio section, and a communication control device capable of communicating via the second radio section, a transmission window control unit that receives a control signal including information indicating a current buffer state of the router and a parameter that affects a future buffer state of the router from the router, predicts a future buffer state of the router based on the received control signal, and determines a second window size which is the amount of data transmitted at a time toward the router based on a prediction result, A communication control device comprising the above.

9. In a communication system including a first radio section and a second radio section, a control circuit for controlling a first proxy installed in front of the first radio section and having a function of controlling a first window size which is the amount of data transmitted at a time toward the first radio section and a second proxy capable of communicating via the second radio section, Based on the control signal transmitted from the first proxy, the step of predicting a future buffer state of the first proxy based on the control signal including information indicating a current buffer state of the first proxy and a parameter that affects a future buffer state of the first proxy, Based on the prediction result of the future buffer state, the step of determining a second window size which is the amount of data transmitted at a time toward the first proxy, A control circuit characterized in that the above is executed by the second proxy.

10. In a communication system including a first radio section and a second radio section, a storage medium storing a program for controlling a first proxy installed in front of the first radio section and having a function of controlling a first window size which is the amount of data transmitted at a time toward the first radio section and a second proxy capable of communicating via the second radio section, the program includes, Based on the control signal transmitted from the first proxy, the step of predicting a future buffer state of the first proxy based on the control signal including information indicating a current buffer state of the first proxy and a parameter that affects a future buffer state of the first proxy, Determining a second window size, which is the amount of data to be transmitted at once towards the first proxy, based on the prediction result of the future buffer state; A storage medium, characterized in that it causes the second proxy to execute the above. **Claim 11** In a communication system including a first radio section and a second radio section, a first proxy installed in front of the first radio section and having a function of controlling a first window size, which is the amount of data to be transmitted at once towards the first radio section, and a second proxy capable of communicating via the second radio section predict the future buffer state of the first proxy based on a control signal transmitted from the first proxy and including information indicating the current buffer state of the first proxy and a parameter affecting the future buffer state of the first proxy; The second proxy determines a second window size, which is the amount of data to be transmitted at once towards the first proxy, based on the prediction result of the future buffer state; A communication control method, characterized by including the above.

Images