JP7095005B2 - Satellite communication system and satellite communication method - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) Issuer name: Institute of Electronics, Information and Communication Engineers, Publication name: IEICE Communications Expressions, Volume, Issue number: Vol. 8, No. 9. Date of issue: June 14, 1st year of Reiwa (2) Date: June 18, 1st year of Reiwa, Meeting name: 32nd International Symposium on Space Technology and Science (ISTS2019 Fukui Convention), held Location: Fukui Prefectural Hall Aossa

The present invention relates to a satellite communication system and a satellite communication method in which a terminal and a base station on the ground communicate with each other via an artificial satellite.

In modern times, wireless communication is an indispensable infrastructure in industry and daily life. The number of wireless terminals represented by smartphones has increased more than several times the population due to the spread of IoT and the like. Under this circumstance, various wireless access methods have been proposed for these terminals to connect to a network and perform data communication with a limited number of base stations. In addition to the access method for communicating between the terminal and the base station, a satellite access method in which the terminal communicates with the base station via an artificial satellite is known.

In the access method that does not go through the satellite, the terminal periodically notifies the base station of the amount of data stored in the transmission buffer inside the terminal as a buffer status report (BSR) via the uplink control channel (Patent Document 1). reference). The base station determines the resources to be allocated to the terminal based on the received BSR, and the base station notifies the terminal on the downlink control channel. The application of this method to the satellite access method is being studied and studied.

US Pat. No. 8,391,150

However, in the case of the satellite access method, since the terminal communicates with the base station via the artificial satellite, it takes about 480 msec for the control packet to go back and forth between the terminal and the base station. Due to this round-trip time, when the terminal receives the resource information allocated by the base station, the allocated resources may not be appropriate at the terminal, and excess or deficiency of resources may occur.

The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a satellite communication system and a satellite communication method capable of shortening a delay time in uplink traffic in a satellite access method.

The satellite communication system according to the present invention is a satellite communication system in which a terminal and a base station on the ground communicate with each other via an artificial satellite, and the terminal is terminal data that temporarily buffers uplink data to be transmitted. A control message including a transmission buffer unit, an uplink traffic measurement unit that measures the inflow amount of the uplink data packet flowing in within a predetermined time, and a BSR (Buffer Status Report) in which the measured inflow amount is recorded . The generated BSR transmitter, the terminal radio frame receiver that receives the radio frame transmitted from the base station, the resource allocation unit that acquires the uplink resource allocation information from the received radio frame, and the buffered upload. The base station includes a terminal radio frame transmission unit that transmits the radio frame including the link data and the generated control message to the base station based on the acquired uplink resource allocation information, and the base station has received the link data. A base station radio frame receiving unit that separates the radio frame into the uplink data and the control message, a base station data transmission buffer unit that temporarily buffers the separated uplink data, and the separated control message. A radio frame including a BSR receiving unit that acquires the BSR from, a scheduling unit that generates uplink resource allocation information based on the acquired BSR, the generated uplink resource allocation information, and downlink data. , A base station radio frame transmission unit for transmitting to the terminal.

In the satellite communication system, the scheduling unit is based on the traffic amount moving average calculation unit that calculates the moving average of the traffic amount of the uplink data based on the acquired BSR, and the calculated moving average traffic amount. , A PID control unit that calculates the uplink resource allocation amount, and a resource block allocation determination unit that allocates resource blocks based on the calculated uplink resource allocation amount, and the resource block allocation determination unit is the up. It is characterized in that the uplink resource allocation information including the link resource allocation amount is transmitted to the base station radio frame transmission unit.

The satellite communication method according to the present invention is a satellite communication method in which a terminal and a base station on the ground communicate with each other via an artificial satellite, and a step of temporarily buffering uplink data to be transmitted in the terminal. A step of measuring the inflow amount of the uplink data packet flowing in within a predetermined time, a step of generating a control message including a BSR (Buffer Status Report) in which the measured inflow amount is recorded, and the base. A radio frame including a step of receiving a radio frame transmitted from a station, a step of acquiring uplink resource allocation information from the received radio frame, the buffered uplink data, and the generated control message. Is provided to the base station based on the acquired uplink resource allocation information, and within the base station, the received radio frame is separated into the uplink data and the control message. A step of temporarily buffering the separated uplink data, a step of acquiring the BSR from the separated control message, and a step of generating uplink resource allocation information based on the acquired BSR, and generation. It is characterized by comprising a step of transmitting a radio frame including the uplink resource allocation information and the downlink data to the terminal.

In the satellite communication method, the step of generating the uplink resource allocation information is based on the step of calculating the moving average of the traffic amount of the uplink data and the calculated moving average traffic amount based on the acquired BSR. The uplink resource allocation information including the uplink resource allocation amount is included in the process of calculating the uplink resource allocation amount and the process of allocating a resource block based on the calculated uplink resource allocation amount. It is characterized by transmitting to the terminal.

In the satellite communication system and the satellite communication method of the present invention, it is possible to reduce the delay time in UDP-based and TCP-based uplink traffic in the satellite access method.

It is explanatory drawing of the satellite communication system which concerns on embodiment of this invention. It is explanatory drawing of the processing procedure of a terminal. It is explanatory drawing of the processing procedure of a base station. It is a figure which shows the simulation result about the delay time by the satellite communication system in UDP communication. FIG. 5A is a diagram showing Comparative Example 1 which is a simulation result regarding a delay time in UDP communication, and FIG. 5B is a diagram showing Comparative Example 2 which is a simulation result regarding a delay time in UDP communication. It is a figure which shows the comparative example 3 which is the simulation result about the delay time in UDP communication. It is a figure which shows the simulation result about the satellite communication system in TCP communication, and the delay time of Comparative Example 4, Comparative Example 5, and Comparative Example 6.

<Structure of satellite communication system 10>
Hereinafter, an embodiment for carrying out the satellite communication system 10 and the satellite communication method according to the embodiment of the present invention (hereinafter, referred to as “embodiment”) will be described with reference to the drawings. FIG. 1 is an explanatory diagram of a satellite communication system 10 according to an embodiment of the present invention.

The satellite communication system 10 includes a terminal 100 and a base station 200 installed on the ground, and the terminal 100 and the base station 200 communicate with each other via an artificial satellite 50.

The terminal 100 includes a terminal data transmission buffer unit 102, an uplink traffic measurement unit 104, a BSR transmission unit 106, a terminal radio frame reception unit 108, a resource allocation unit 110, and a terminal radio frame transmission unit 112.

The terminal 100 is a terminal having a communication function. For example, the terminal 100 is an LTE (registered trademark) terminal formulated by 3GPP (3rd Generation Partnership Project). Further, the terminal 100 may be an aircraft-mounted terminal.

The terminal data transmission buffer unit 102 is a means for temporarily buffering the uplink data to be transmitted.

The uplink traffic measuring unit 104 is a means for measuring the amount of inflow of a packet of uplink data within a predetermined time. Here, the predetermined time is a time equivalent to a predetermined interval in which the BSR transmission unit 106, which will be described later, generates a BSR.

The BSR transmission unit 106 is a means for generating and notifying a control message including the BSR based on the inflow amount at predetermined intervals. Here, the predetermined interval is 0.5 to 2 (msec), preferably 1 (msec).

The terminal radio frame receiving unit 108 is a means for receiving the radio frame transmitted from the base station 200.

The resource allocation unit 110 is a means for acquiring uplink resource allocation information from the radio frame.

The terminal radio frame transmission unit 112 is a means for transmitting a radio frame for transmitting the radio frame to the base station 200 based on the uplink resource allocation information. Here, the radio frame includes the buffered uplink data and the generated control message.

The base station 200 includes a base station radio frame receiving unit 202, a base station data transmission buffer unit 204, a BSR receiving unit 206, a scheduling unit 208, a traffic volume moving average calculation unit 210, a PID control unit 212, a resource block allocation determination unit 214, and the base station 200. A base station radio frame transmission unit 216 is provided.

The base station radio frame receiving unit 202 is a means for separating the radio frame received from the terminal 100 into uplink data and a control message.

The base station data transmission buffer unit 204 is a means for temporarily buffering uplink data.

The BSR receiving unit 206 is a means for acquiring a BSR from a control message.

The scheduling unit 208 is a means for generating uplink resource allocation information based on the BSR. The scheduling unit 208 includes a PID control unit 212, a resource block allocation determination unit 214, and a base station radio frame transmission unit 216.

The traffic amount moving average calculation unit 210 is a means for calculating a moving average for the traffic amount of uplink data based on the acquired BSR.

The PID control unit 212 is a means for calculating the uplink resource allocation amount by PID (Proportional Integral Differential) control based on the moving average traffic amount of the uplink data.

The resource block allocation determination unit 214 is a means for allocating a resource block based on the uplink resource allocation amount and generating uplink resource allocation information including the uplink resource allocation amount.

The base station radio frame transmission unit 216 is a means for transmitting a radio frame including uplink resource allocation information and downlink data to the terminal 100.

<Explanation of operation of terminal 100>
* Next, the operation when uplink data is transmitted from the terminal 100 to the base station 200 via the artificial satellite 50 will be described with reference to the drawings. FIG. 2 is an explanatory diagram of a processing procedure of the terminal 100.

Uplink (UL) data transmitted from the terminal 100 to the base station 200 via the artificial satellite 50 is supplied to the terminal data transmission buffer unit 102 and the uplink traffic measurement unit 104 (step S1).

The terminal data transmission buffer unit 102 temporarily buffers the supplied uplink data, and then transmits the uplink data to the terminal wireless frame transmission unit 112 (step S2).

The uplink traffic measurement unit 104 measures the amount of inflow of the supplied uplink data packet within a predetermined time, and transmits the inflow amount to the BSR transmission unit 106 (step S3).

The BSR transmission unit 106 receives the inflow amount, generates a control message including the BSR based on the inflow amount received at predetermined intervals, and transmits the control message to the terminal radio frame transmission unit 112 (step S4).

The terminal radio frame receiving unit 108 receives the radio frame transmitted from the base station 200 and transmits it to the resource allocation unit 110 (step S5).

The resource allocation unit 110 receives the wireless frame, acquires uplink resource allocation information from the received wireless frame, and transmits the uplink resource allocation information to the terminal wireless frame transmission unit 112 (step S6).

The terminal radio frame transmission unit 112 transmits the radio frame to the base station 200 via the artificial satellite 50 based on the received uplink resource allocation information (step S7).

<Explanation of operation of base station 200>
Next, the operation when the wireless frame is transmitted from the base station 200 to the terminal 100 via the artificial satellite 50 will be described with reference to the drawings. FIG. 3 is an explanatory diagram of a processing procedure of the base station 200.

The base station radio frame receiving unit 202 separates the radio frame received from the terminal 100 into uplink data and a control message (step S11). The base station radio frame receiving unit 202 transmits the separated uplink data to the base station data transmission buffer unit 204. Further, the base station radio frame receiving unit 202 transmits a control message to the BSR receiving unit 206.

The base station data transmission buffer unit 204 receives the uplink data, temporarily buffers it, and transmits it to another terminal (step S12).

The BSR receiving unit 206 receives the control message, acquires the BSR from the received control message, and transmits it to the scheduling unit 208 (step S13).

The traffic amount moving average calculation unit 210 of the scheduling unit 208 receives the BSR, calculates the moving average of the traffic amount of the uplink data based on the received BSR, and transmits it to the PID control unit 212 (step S14). ).

The PID control unit 212 calculates the uplink resource allocation amount to be allocated to the terminal 100 by PID control based on the moving average traffic amount of the received uplink data, and transmits it to the resource block allocation determination unit 214 (step S15).

The resource block allocation determination unit 214 receives the uplink resource allocation amount, allocates the resource block based on the received uplink resource allocation amount, and allocates the uplink resource allocation information including the uplink resource allocation amount to the base station wireless frame. It is transmitted to the transmission unit 216 (step S16).

The base station radio frame transmission unit 216 receives the uplink resource allocation information, and transmits the radio frame including the received uplink resource allocation information and the downlink data to be transmitted to the terminal 100 via the artificial satellite 50. It is transmitted to the terminal 100 (step S17).

FIG. 4 is a diagram showing a simulation result regarding a delay time by the satellite communication system 10 in UDP communication. FIG. 5A is a diagram showing Comparative Example 1 which is a simulation result regarding the delay time in UDP communication, and FIG. 5B is a diagram showing Comparative Example 2 which is a simulation result regarding the delay time in UDP communication. FIG. 6 is a diagram showing Comparative Example 3, which is a simulation result regarding the delay time in UDP communication.

Comparative Example 1 is a case where resources are evenly allocated without scheduling resources (fixed schedule). Comparative Example 2 and Comparative Example 3 are resource scheduling methods adopted in the terrestrial LTE (registered trademark). Comparative Example 2 is a Round Robin schedule, and Comparative Example is Proportional Fairness.

In FIGS. 4 to 6, the horizontal axis represents time, the left vertical axis represents delay time, and the right vertical axis represents traffic volume. The graph indicated by D indicates the delay time, and T indicates the traffic volume.

In the case of communication using UDP (User Datagram Protocol) without congestion control, the delay time does not diverge in the satellite communication system 10 even if the traffic volume fluctuates, and is less than 2000 (msec) (see FIG. 4). ). On the other hand, in Comparative Example 1, Comparative Example 2 and Comparative Example 3, it can be seen that the delay time is 2000 (msec) or more over time (see FIGS. 5A, 5B and 6). ).

FIG. 7 is a diagram showing simulation results of the satellite communication system 10 in TCP communication and the delay times of Comparative Example 4, Comparative Example 5, and Comparative Example 6. The time required for uplink transfer of 3 Mbytes of data per session by TCP is shown. In FIG. 7, the horizontal axis indicates the number of sessions, and the vertical axis indicates the session time.

× indicates data from the satellite communication system 10, ▲ indicates data from the fixed schedule of Comparative Example 4, ◇ indicates data from the Round Robin schedule of Comparative Example 5, and ■ indicates data from the Proportional Fairness of Comparative Example 6.

In the case of TCP (Transmission Control Protocol) communication accompanied by congestion control, it can be seen that the satellite communication system 10 has a shorter session time (delay time) than any of Comparative Examples 4 to 6. Even in Comparative Example 5, which has the shortest session time among the Comparative Examples, the session time is always completed in a short time of about 5000 msec, and it can be seen that stable high performance is exhibited.

The satellite communication system 10 is a satellite communication system 10 in which the terminal 100 and the base station 200 on the ground communicate with each other via the artificial satellite 50, and the terminal 100 temporarily buffers the uplink data to be transmitted. The terminal data transmission buffer unit 102, the uplink traffic measurement unit 104 that measures the inflow amount of the uplink data packet flowing in within a predetermined time, and the BSR (Buffer Status Report) created based on the measured inflow amount. BSR transmission unit 106 that generates a control message including the above, terminal radio frame reception unit 108 that receives a radio frame transmitted from the base station 200, and resource allocation that acquires uplink resource allocation information from the received radio frame. A terminal radio frame transmission unit 112 that transmits a radio frame including the buffered uplink data and the generated control message to the base station 200 based on the acquired uplink resource allocation information. The base station 200 temporarily buffers the separated uplink data with the base station radio frame receiving unit 202 that separates the received radio frame into the uplink data and the control message. The base station data transmission buffer unit 204, the BSR receiving unit 206 that acquires the BSR from the separated control message, the scheduling unit 208 that generates the uplink resource allocation information based on the acquired BSR, and the generated said unit. A satellite communication system including a base station radio frame transmission unit 216 that transmits a radio frame including uplink resource allocation information and downlink data to the terminal 100.

In the satellite communication system 10, the scheduling unit 208 uses the traffic amount moving average calculation unit 210 for calculating the moving average of the traffic amount of the uplink data based on the acquired BSR, and the calculated moving average traffic amount. Based on the PID control unit 212 that calculates the uplink resource allocation amount, and the resource that allocates the resource block based on the calculated uplink resource allocation amount and generates the uplink resource allocation information including the uplink resource allocation amount. It has a block allocation determination unit 214, and the resource block allocation determination unit 214 transmits the uplink resource allocation information to the base station radio frame transmission unit 216.

According to the satellite communication system 10, it is possible to reduce the delay time in UDP-based and TCP-based uplink traffic in the satellite access method.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

10 ... Satellite communication system 50 ... Artificial satellite 100 ... Terminal 102 ... Terminal data transmission buffer unit 104 ... Uplink traffic measurement unit 106 ... BSR transmission unit 108 ... Terminal wireless frame reception unit 110 ... Resource allocation unit 112 ... Terminal wireless frame transmission unit 200 ... Base station 202 ... Base station wireless frame receiving unit 204 ... Base station data transmission buffer unit 206 ... BSR receiving unit 208 ... Scheduling unit 210 ... Traffic volume movement average calculation unit 212 ... PID control unit 214 ... Resource block allocation determination unit 216 … Base station wireless frame transmitter

Claims (4)

It is a satellite communication system in which a terminal and a base station on the ground communicate with each other via an artificial satellite.
The terminal is
The terminal data transmission buffer section that temporarily buffers the uplink data to be transmitted,
An uplink traffic measurement unit that measures the amount of inflow of the uplink data packet within a predetermined time, and
A BSR transmitter that generates a control message including a BSR (Buffer Status Report) in which the measured inflow amount is recorded , and
A terminal radio frame receiver that receives a radio frame transmitted from the base station,
A resource allocation unit that acquires uplink resource allocation information from the received wireless frame, and
A terminal wireless frame transmitter that transmits a wireless frame including the buffered uplink data and the generated control message to the base station based on the acquired uplink resource allocation information.
Equipped with
The base station is
A base station wireless frame receiving unit that separates the received wireless frame into the uplink data and the control message.
A base station data transmission buffer unit that temporarily buffers the separated uplink data, and
A BSR receiver that acquires the BSR from the separated control message, and
A scheduling unit that generates uplink resource allocation information based on the acquired BSR,
A base station wireless frame transmission unit that transmits a wireless frame including the generated uplink resource allocation information and downlink data to the terminal.
A satellite communication system characterized by being equipped with. In the satellite communication system according to claim 1,
The scheduling unit
A traffic amount moving average calculation unit that calculates a moving average for the traffic amount of the uplink data based on the acquired BSR.
A PID control unit that calculates the uplink resource allocation amount based on the calculated moving average traffic amount,
A resource block allocation determination unit that allocates resource blocks based on the calculated uplink resource allocation amount and generates uplink resource allocation information including the uplink resource allocation amount.
Have,
The resource block allocation determination unit is a satellite communication system characterized by transmitting the uplink resource allocation information to the base station radio frame transmission unit. It is a satellite communication method in which a terminal and a base station on the ground communicate with each other via an artificial satellite.
In the terminal,
The process of temporarily buffering the uplink data to be transmitted,
The process of measuring the amount of inflow of the uplink data packet within a predetermined time, and
A step of generating a control message including a BSR (Buffer Status Report) in which the measured inflow amount is recorded , and
The process of receiving the wireless frame transmitted from the base station and
The process of acquiring uplink resource allocation information from the received wireless frame and
A step of transmitting a radio frame including the buffered uplink data and the generated control message to the base station based on the acquired uplink resource allocation information.
Equipped with
In the base station
A step of separating the received wireless frame into the uplink data and the control message, and
The process of temporarily buffering the separated uplink data and
The process of acquiring the BSR from the separated control message and
A process of generating uplink resource allocation information based on the acquired BSR, and
A process of transmitting a wireless frame including the generated uplink resource allocation information and downlink data to the terminal, and
A satellite communication method characterized by comprising. In the satellite communication method according to claim 3,
The step of generating the uplink resource allocation information is
Based on the acquired BSR, the moving average of the traffic volume of the uplink data is calculated in the process and
The process of calculating the uplink resource allocation amount based on the calculated moving average traffic amount, and
It has a process of allocating a resource block based on the calculated uplink resource allocation amount and generating uplink resource allocation information including the uplink resource allocation amount.
A satellite communication method comprising transmitting the uplink resource allocation information to the terminal.

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