Control station, control method, control circuit, and storage medium

The present disclosure relates to a control station, a control method, a control circuit, and a storage medium for controlling a constellation network consisting of multiple satellite stations and multiple ground stations.

Satellite constellations, which are constructed from multiple low-orbit satellites, can significantly reduce latency compared to the geostationary satellites that have been used up until now, and are therefore expected to be a means of communication to areas where it is difficult to develop terrestrial communication networks. In addition, low-orbit and medium-orbit satellites, which are at lower altitudes than geostationary satellites, are also capable of more detailed observations than geostationary satellites, and are therefore expected to be used for a variety of observations.

Although optical communications are more susceptible to atmospheric and rain attenuation than radio-wave communications, their high-capacity communications capabilities have led to their potential use as inter-satellite links in space. However, satellite-to-ground station links, which transmit data from satellites to ground stations, are inevitably affected by atmospheric and rain attenuation. Therefore, optical satellite-to-ground station links are significantly affected by rainfall and may be unable to communicate depending on the weather at the ground station. On the other hand, radio-wave satellite-to-ground station links are less affected by atmospheric and rain attenuation than optical communications, but their communication capacity is also low. Therefore, even if high-speed inter-satellite communications are possible for large volumes of data generated onboard satellites, the satellite-to-ground station link becomes a bottleneck. Therefore, it is necessary to increase the capacity of satellite-to-ground station communications by using multiple ground stations. In satellite constellation network systems where large volumes of data are generated onboard satellites, it is important to effectively utilize these multiple satellite-to-ground station links.

For example, Patent Document 1 describes a technique for realizing effective use of the satellite-ground station link by modeling atmospheric attenuation between the satellite and the ground station and optimizing the satellite parameters.

<p><patcit num="1"><text>U.S. Patent No. 6,587,687</text></patcit></p>

<p>When optical fiber is used as the line between the satellite and the ground station, its capacity can change significantly or even become unusable due to factors such as weather. Even when radio waves are used as the line between the satellite and the ground station, the line condition changes due to factors such as changes in the elevation angle between the satellite and the ground station, causing the communication capacity to fluctuate. When downlinking data acquired from low-earth or medium-earth orbit satellites to the ground using a satellite-to-ground station link whose communication capacity changes depending on the situation, if data is concentrated at a ground station with a small communication capacity between the satellite and the ground station, it will take a long time to downlink the data from the satellite to the ground station, resulting in increased latency.</p><p>The present disclosure has been made in view of the above, and aims to provide a control station that can suppress an increase in data transmission delay between a satellite and a ground station in a constellation network.</p>

<p>In order to solve the above-mentioned problems and achieve the object, the present disclosure provides a control station for controlling a constellation network that includes a plurality of satellite stations and a plurality of ground stations, each of which is mounted on an orbiting satellite, and in which some of the plurality of satellite stations communicate directly with the ground stations, the control station controlling the constellation network includes a control station for controlling the constellation network that includes a plurality of satellite stations and a plurality of ground stations, each of which communicates directly with the ground stations, based on the line quality of a communication line that the satellite station uses for direct communication with the ground stations.<u style="Single">Data from</u>is the downlink data<u style="Single">as</u>send<u style="Single">will be</u>The communication system is characterized in that it is provided with a destination control unit that determines a destination ground station, which is a ground station with which to communicate when the communication line is established, and the destination control unit determines the destination ground station so that the ratio of the amount of data transmitted on each communication line approaches the ratio of the communication capacities of each communication line.</p>

<p>The control station according to the present disclosure has the advantage of being able to suppress increases in data transmission delay between satellites and ground stations in a constellation network.</p>

<figref num="1">FIG. 1 is a diagram illustrating a configuration example of a satellite communication system according to a first embodiment.</figref><figref num="2">FIG. 1 is a diagram illustrating a configuration example of a control station according to a first embodiment;</figref><figref num="3">1 is a flowchart illustrating an example of an operation of a control station according to a first embodiment.</figref><figref num="4">FIG. 1 is a diagram showing information exchanged between devices constituting the satellite communication system according to the first embodiment.</figref><figref num="5">FIG. 1 is a diagram illustrating an example of hardware for implementing a control station according to a first embodiment.</figref><figref num="6">FIG. 1 is a first diagram for explaining a method in which a control station according to a first embodiment determines a combination of a satellite station and a ground station with which to communicate;</figref><figref num="7">FIG. 2 is a second diagram for explaining a method in which the control station according to the first embodiment determines a combination of a satellite station and a ground station with which to communicate;</figref><figref num="8">FIG. 10 is a diagram illustrating a configuration example of a control station according to a second embodiment;</figref><figref num="9">FIG. 10 is a diagram for explaining a method for determining a communication path by a control station according to a second embodiment;</figref><figref num="10">FIG. 10 is a diagram illustrating an example of a method for determining a communication path by a control station according to a second embodiment;</figref><figref num="11">FIG. 10 is a diagram illustrating another example of a method for determining a communication path by a control station according to the second embodiment.</figref>

A control station, a control method, a control circuit, and a storage medium according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

First Embodiment FIG. 1 is a diagram showing an example of the configuration of a satellite communication system 100 according to a first embodiment.

The satellite communication system 100 according to the first embodiment includes a plurality of satellite stations 1 and a plurality of ground stations 2 that form a constellation network, and a control station 3 that controls the constellation network.

A satellite station 1 is a communication device mounted on an orbiting satellite, and is connected to other adjacent satellite stations 1 via inter-satellite links 11, which are optical links. Multiple satellite stations 1 form a satellite constellation network, and some satellite stations 1 are connected to ground stations 2, which are communication devices installed on the ground 5. Satellite stations 1 connected to ground stations 2 communicate directly with ground stations 2 via communication lines 12. Satellite stations 1 not connected to ground stations 2 communicate with other satellite stations 1 connected to ground stations 2 and ground stations 2 via communication lines 12. Furthermore, each satellite station 1 moves over time, and the satellite station 1 that communicates directly with ground stations 2 also changes over time. Note that the ground stations 2 are located far enough apart that a specific satellite station 1 cannot communicate with all ground stations 2 simultaneously.

Each ground station 2 is connected via a terrestrial network 51, and each satellite station 1 may transmit data to any ground station 2. A control station 3 is also connected to the terrestrial network 51. The control station 3 determines the combination of satellite station 1 and ground station 2 with which to communicate. Note that while FIG. 1 shows an example of a configuration in which the control station 3 is connected to the terrestrial network 51, the control station 3 may also be mounted on a specific satellite station 1. In other words, the control station 3 may determine the combination of satellite station 1 and ground station 2 with which to communicate on board the satellite, and control each satellite station 1 and each ground station 2 in accordance with the determination result. The control station 3 is assumed to hold information regarding the relative positions of the multiple satellite stations 1 and multiple ground stations 2 that make up the constellation network, information regarding the connection relationships between the satellite stations 1, and so on.

2 is a diagram illustrating an example of the configuration of the control station 3 according to the first embodiment. The control station 3 includes a receiving unit 31 that receives signals transmitted from each ground station 2, a transmitting unit 32 that transmits signals to each ground station 2, a line quality information collecting unit 33 that collects quality information of the communication line 12 between each ground station 2 and the satellite station 1, and a destination control unit 34 that determines a combination of a satellite station 1 and a ground station 2 that will communicate with each other and notifies each satellite station 1 of the ground station 2 that is the destination of a signal transmitted from each satellite station 1.

Next, a description will be given of the operation of the control station 3. Fig. 3 is a flowchart showing an example of the operation of the control station 3 according to the first embodiment.

As shown in FIG. 3 , the control station 3 first collects line quality information (step S11). In step S11, the line quality information collection unit 33 collects information on the line quality between the satellite station 1 and the ground station 2, which is periodically monitored by each ground station 2, from each ground station 2 via the receiving unit 31. The line quality information between the satellite station 1 and the ground station 2 is information indicating the quality of the communication line 12 between the ground station 2 and the satellite station 1 with which the ground station 2 directly communicates. The line quality of the communication line 12 fluctuates when the atmospheric conditions between the satellite station 1 and the ground station 2 change, or when the elevation angle between the satellite station 1 and the ground station 2 changes due to a change in the attitude of the orbiting satellite on which the satellite station 1 is mounted. Therefore, one or both of the atmospheric conditions between the satellite station 1 and the ground station 2 and the attitude of the orbiting satellite may be used as the line quality of the communication line 12.

The control station 3 then determines a combination of satellite stations 1 that will communicate with each ground station 2 (step S12). In step S12, the destination control unit 34 determines a combination of satellite stations 1 and ground stations 2 that will communicate based on the line quality information collected by the line quality information collection unit 33 in step S11. Specifically, the destination control unit 34 determines, for all satellite stations 1, the ground stations 2 that will be the destinations of data transmitted by each satellite station 1. The method by which the destination control unit 34 determines the combinations will be described in detail later.

The control station 3 then notifies each satellite station 1 of the determined combination (step S13). In this step S13, the destination control unit 34 transmits the combination of satellite station 1 and earth station 2 to communicate determined in step S12, i.e., information about the earth station 2 to which each satellite station 1 will send data (hereinafter referred to as destination earth station information), from the transmitter 32 to each satellite station 1 via the earth station 2. For satellite stations 1 that cannot communicate directly with the earth station 2, the destination earth station information is transmitted via the inter-satellite link 11. Each satellite station 1 changes the earth station 2 to which the transmission data, which is downlink data, is addressed (hereinafter referred to as destination earth station) based on the destination earth station information received from the control station 3. In step S13, the destination control unit 34 of the control station 3 does not need to transmit the destination earth station information to satellite stations 1 that do not need to change the destination earth station.

The combination determined in step S12 is also followed when transmitting uplink data from the ground to the satellite station 1. That is, the uplink data from the ground to each satellite station 1 is transmitted to the destination satellite station 1 via a route based on the combination determined by the control station 3 in step S12.

4 is a diagram illustrating information exchanged among devices constituting the satellite communication system 100 according to the first embodiment. As shown in FIG. 4, a ground station 2 periodically monitors the line quality between the ground station 2 and the satellite station 1 with which it directly communicates, and transmits the acquired line quality information to a control station 3. Combination information indicating the combination determined by the control station 3, i.e., information indicating the combination of the communicating satellite station 1 and the ground station 2, is transmitted from the control station 3 to each ground station 2, and then transmitted from each ground station 2 to each satellite station 1. The combination information includes destination ground station information for the satellite station 1. Note that, although transmission of combination information between satellite stations 1 is omitted in FIG. 4, the combination information transmitted from the ground station 2 is transmitted to all satellite stations 1 via inter-satellite links 11.

2, each functional unit may be configured as a separate circuit or device, or multiple functional units may be configured as a single circuit or device. Each functional unit may be realized by a control circuit including a memory and a processor that executes a program stored in the memory, or by dedicated hardware.

5 is a diagram illustrating an example of hardware for realizing the control station 3 according to the first embodiment. In FIG. 5, an example is shown in which the control station 3 is realized by a control circuit. The control circuit for realizing the control station 3 includes an input unit 91, a processor 92, a memory 93, and an output unit 94.

The input unit 91 receives signals from the outside. The output unit 94 outputs signals from the control circuit to the outside. The processor 92 is, for example, a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), etc. The memory 93 is, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, a DVD (Digital Versatile Disk), etc.

5, programs for operating as the receiving unit 31, transmitting unit 32, line quality information collecting unit 33, and destination control unit 34 of the control station 3 are stored in memory 93, and the processor 92 reads and executes these programs to realize the receiving unit 31, transmitting unit 32, line quality information collecting unit 33, and destination control unit 34. The programs stored in memory 93 may be provided to users or the like in a state written on a storage medium such as a CD (Compact Disc)-ROM or DVD-ROM, or may be provided via a network.

Furthermore, when the control station 3 is realized by dedicated hardware, the dedicated hardware may be, 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.

Next, a method by which the destination control unit 34 of the control station 3 determines a combination of a satellite station 1 and a ground station 2 to communicate with will be described in detail with reference to Fig. 6 and Fig. 7. Fig. 6 is a first diagram for explaining a method by which the control station 3 according to the first embodiment determines a combination of a satellite station 1 and a ground station 2 to communicate with, and Fig. 7 is a second diagram for explaining a method by which the control station 3 according to the first embodiment determines a combination of a satellite station 1 and a ground station 2 to communicate with.

6 and 7 show an example of a method for determining combinations when there are six satellite stations 1 and two earth stations 2, earth station #A and earth station #B, with which each satellite station 1 can directly or indirectly communicate.

FIG. 6 shows a case where the line quality between the satellite side and ground station #A and the line quality between the satellite side and ground station #B are both good. In such a case, the line via ground station #A and the line via ground station #B have the same communication capacity. Therefore, the destination control unit 34 determines a combination so that data from three satellite stations 1 is downlinked via each of the lines via ground station #A and ground station #B. Note that the example shown in FIG. 6 assumes that the amount of data generated at each satellite station 1 and transmitted to ground station #A or ground station #B is the same and does not differ between the satellite stations 1. The same applies to the example shown in FIG. 7.

If the line quality information collected by the line quality information collection unit 33 changes, i.e., if the line quality changes, the destination control unit 34 changes the destination ground station of the satellite station 1 based on the changed line quality information, and changes the number of satellite stations 1 that transmit data to each ground station 2.

For example, Figure 7 shows a case where the line quality via ground station #A is poor and the line quality via ground station #B is good. In such a case, the destination control unit 34 reduces the amount of data downlinked via the line via ground station #A and increases the amount of data downlinked via the line via ground station #B, thereby achieving effective use of the downlink capacity. In the example shown in Figure 7, the number of satellite stations 1 that transmit data to ground station #A as the destination ground station is set to two, and the number of satellite stations 1 that transmit data to ground station #B as the destination ground station is increased to four, thereby achieving effective use of the downlink capacity.

7, there are two and four satellite stations 1 that have ground station #A and ground station #B as their destination ground stations, respectively. However, depending on the line conditions, the number of satellite stations 1 may be one and five. The number of satellite stations 1 that use each line is determined based on the ratio of the communication capacities of the communication lines between the ground station and the satellite station that directly communicates with the ground station. For example, if the communication line used for communication with ground station #A is communication line #A and the communication line used for communication with ground station #B is communication line #B, and the communication capacity ratio between communication line #A and communication line #B is 2:3, the destination control unit 34 determines the number of satellite stations 1 that have each ground station as their destination so that the ratio between the number of satellite stations 1 that transmit data addressed to ground station #A and the number of satellite stations 1 that transmit data addressed to ground station #B approaches 2:3.

6 and 7, it is assumed that the amount of data generated by each satellite station 1 is the same, but if the amount of data generated by each satellite station 1 differs, the control station 3 weights the number of satellite stations 1 to be combined depending on the amount of data generated. In other words, the control station 3 takes into account the ratio of the amount of data generated by each satellite station 1 and determines the combination of satellite stations 1 and terrestrial stations 2 so as to minimize the transmission delay in each line.

For example, in the case shown in Fig. 6, when the quality of the line via ground station #A and the quality of the line via ground station #B are both good and the communication capacities of these two lines are equivalent, control station 3 determines the combination of satellite station 1 and ground station 2 so that the amount of downlink data transmitted over each line is equivalent. By determining the combination in this manner, the difference in the amount of data transmission delay over each line is reduced, and the transmission delay of data transmitted and received between satellite station 1 and ground station 2 can be reduced across the entire satellite communication system 100. In other words, an increase in the transmission delay of data transmitted and received between satellite station 1 and ground station 2 can be suppressed.

Furthermore, when the amount of data generated differs for each satellite station 1 and the quality of the line (communication line #A) passing through ground station #A differs from the quality of the line (communication line #B) passing through ground station #B, as in the case shown in Figure 7, the control station 3 determines the combination of satellite station 1 and ground station 2 so that the ratio between the amount of data transmitted on communication line #A and the amount of data transmitted on communication line #B approaches the ratio between the communication capacity of communication line #A and the communication capacity of communication line #B.

As described above, the satellite communication system 100 according to this embodiment changes the destination terrestrial station of downlink data generated at the satellite station 1 depending on the state of each communication line 12 between the satellite station 1 and the terrestrial station 2. This makes effective use of the communication line 12 between the satellite station 1 and the terrestrial station 2, thereby reducing the delay in the arrival of downlink data generated at each satellite station 1 at the terrestrial station 2.

Second Embodiment Next, a satellite communication system according to the second embodiment will be described. The satellite communication system according to the second embodiment is similar to the satellite communication system 100 according to the first embodiment shown in FIG. 1. In this embodiment, differences from the first embodiment will be described. The satellite communication system according to the second embodiment determines a pair of satellite stations 1 and earth stations 2 to communicate with, as well as a communication route from each satellite station 1 to a destination earth station. In this embodiment, the control station that determines the pair of satellite stations 1 and earth stations 2 to communicate with and the communication route is referred to as control station 3a. In addition to the line quality information described in the first embodiment, the control station 3a according to the second embodiment also collects fault information on each inter-satellite link 11 used in determining the communication route, and determines the destination earth station for each satellite station 1 and the communication route from each satellite station 1 to the destination earth station based on the collected line quality information and fault information.

Fig. 8 is a diagram illustrating a configuration example of a control station 3a according to the second embodiment. In Fig. 8, the same components as those in the control station 3 according to the first embodiment shown in Fig. 2 are denoted by the same reference numerals. Explanation of the components denoted by the same reference numerals as those in Fig. 2 will be omitted.

The control station 3a has a configuration in which a link failure information collection unit 35 and a route control unit 36 are added to the control station 3 according to the first embodiment.

The link fault information collector 35 collects link fault information indicating the occurrence of a fault in each inter-satellite link 11 from the satellite station 1. The link fault information is transmitted from the satellite station 1 that detects a fault in the inter-satellite link 11 to the control station 3a via the ground station 2.

Based on the link failure information collected by the link failure information collection unit 35, the route control unit 36 determines a communication route from each satellite station 1 to the ground station 2 with which each satellite station 1 communicates.

The method by which the destination control unit 34 and the route control unit 36 determine the combination of satellite station 1 and earth station 2 with which to communicate, and the method by which they determine the communication route from each satellite station 1 to the earth station 2 with which to communicate, will be described in detail later, but depending on the results of determining the communication route, the destination earth station of the satellite station 1 may be changed.

Combination information indicating the combination determined by the destination control unit 34 and communication path information indicating the communication path from each satellite station 1 to the earth station 2 with which it will communicate, determined by the path control unit 36, are transmitted from the transmitter 32 to each satellite station 1 via the earth station 2. Each satellite station 1 changes the destination earth station based on the destination earth station information included in the combination information received from the control station 3a, and changes the communication path to the destination earth station based on the communication path information. Note that because the communication path information also includes information about the earth station 2 that is the destination of the downlink data, the control station 3a may omit transmitting the combination information, and each satellite station 1 may change the destination earth station and the communication path to the destination earth station based on the communication path information.

Fig. 9 is a diagram for explaining a method for determining a communication path by the control station 3a according to the second embodiment. Fig. 9 shows an example of a method for determining a communication path when there are 12 satellite stations 1, and these 12 satellite stations 1 are satellite stations #1 to #12. In this embodiment, the satellite station 1 that communicates directly with the ground station 2 is referred to as the destination satellite station, and in the example shown in Fig. 9, satellite station #6 and satellite station #8 are the destination satellite stations. It is assumed that the line quality of the communication line used by satellite station #6 and satellite station #8 for direct communication with the ground station 2 is equivalent, and that the communication capacity of each communication line is also equivalent.

In the configuration shown in FIG. 9, data can be transmitted from satellite station #2 to satellite station #6 in one hop, but data must be transmitted three hops to reach satellite station #8 via satellite stations #3 and #4. If there are many satellite stations to be passed through, the bandwidth of the inter-satellite link will be consumed. Therefore, satellite station #6 should be selected as the destination satellite station for satellite station #2. Therefore, the control station 3a determines the communication path, i.e., the destination satellite station for each satellite station, as shown in FIG. 10. FIG. 10 is a diagram illustrating an example of a method for determining a communication path by the control station 3a according to the second embodiment. In the example shown in FIG. 10, the control station 3a determines the satellite station for transmitting to satellite station #6 and the satellite station for transmitting to satellite station #8 so as to minimize the number of hops from each satellite station to the destination satellite station. While the present embodiment describes an example in which the number of hops is used as a metric to determine a communication path, physical distance, transmission delay, or the like may also be used as a metric to determine a communication path. Furthermore, a combination of indicators such as the number of hops, physical distance, and transmission delay may also be used as a metric.

Fig. 11 is a diagram illustrating another example of a method for determining a communication path by the control station 3a according to the second embodiment. Fig. 11 illustrates an example of a method for determining a communication path when a failure occurs in an inter-satellite link. Fig. 11 illustrates, as an example, a method for determining a communication path when a failure occurs in the inter-satellite link connecting satellite station #3 and satellite station #4 and the inter-satellite link connecting satellite station #3 and satellite station #7.

In the communication path determination method shown in FIG. 10, satellite station #8 was selected as the destination satellite station for satellite station #3. However, as shown in FIG. 11, if the inter-satellite links connecting satellite stations #3 and #4 and the inter-satellite link connecting satellite stations #3 and #7 are unavailable due to communication failures caused by factors such as a failure of the optical communication terminals installed in the satellite stations or the effects of attitude control of the orbiting satellite on which the satellite station is installed, data transmission from satellite station #3 to satellite station #8 requires at least four hops via satellite station #2. On the other hand, if satellite station #6 is selected as the destination satellite station for satellite station #3, data transmission is possible in two hops. In this case, the destination satellite station for satellite station #3 is changed to satellite station #6. In this case, the amount of data transmitted to satellite station #6 is greater than the amount of data transmitted to satellite station #8. Therefore, the amount of data must be adjusted to effectively utilize the downlink capacity and reduce transmission delays. In this case, transmission from satellite station #10 to satellite station #8 is possible in three hops, so the destination satellite station for satellite station #10 is changed to satellite station #8. In this way, when changing the destination satellite station, the new destination satellite station is determined so that the total number of hops from each satellite station to the destination satellite station for each destination satellite station does not change significantly before and after the change. In other words, when it is necessary to change the destination satellite station, the new destination satellite station is determined so that the change in the total number of hops from each satellite station to the destination satellite station for each destination satellite station that occurs as a result of the change is small. Note that when the destination satellite station is changed, the destination ground station also changes accordingly.

As described above, the control station 3a determines the combination of satellite stations 1 and ground stations 2 to communicate with and the communication paths from each satellite station 1 to the ground station 2, including the link failure information, and controls each satellite station 1 and each ground station 2 to transmit data according to the determination results. When each satellite station 1 generates an equal amount of data, the destination control unit 34 in the control station 3a determines the number of satellite stations 1 to communicate with each of the multiple ground stations 2, for example, based on the line quality information collected by the line quality information collection unit 33. The route control unit 36 determines the communication paths based on the failure information collected by the link failure information collection unit 35 and the number of satellite stations 1 to communicate with each of the multiple ground stations 2 determined by the destination control unit 34, so that the total number of hops from each satellite station 1 to each ground station 2 for each ground station 2 is equal. Note that the number of hops used in this process may be the number of hops to the satellite station 1 (corresponding to the destination satellite station described above) that directly communicates with the ground station 2.

For example, if the satellite communication system 100 comprises two ground stations 2, designated as ground station #A and ground station #B, and the number of satellite stations 1 communicating with ground station #A and ground station #B is the same, the route control unit 36 determines the communication route from each satellite station 1 to the destination satellite station so that the total number of hops from each satellite station 1 communicating with ground station #A to ground station #A is equal to the total number of hops from each satellite station 1 communicating with ground station #B to ground station #B. At this time, the route control unit 36 changes the destination ground station for each satellite station 1 already determined by the destination control unit 34, as necessary.

Furthermore, when the number of satellite stations 1 communicating with ground station #A and ground station #B is different, route control unit 36 determines the communication route from each satellite station 1 to the destination satellite station so that the ratio of the total number of hops from each satellite station 1 communicating with ground station #A to ground station #A to the total number of hops from each satellite station 1 communicating with ground station #B to ground station #B approaches the ratio of the number of satellite stations 1 communicating with ground station #A to the number of satellite stations 1 communicating with ground station #A. Instead of the ratio of the number of satellite stations 1 communicating with ground station #A to the number of satellite stations 1 communicating with ground station #A, the ratio of the communication capacity between ground station #A and satellite station 1 to the communication capacity between ground station #B and satellite station 1 may be used. Alternatively, the ratio of the line quality between ground station #A and satellite station 1 to the line quality between ground station #B and satellite station 1 may be used.

As described above, in this embodiment, the control station 3a determines the combination of satellite station 1 and ground station 2 to communicate with and the communication path, thereby adjusting the utilization capacity of each communication line 12 depending on the state of each communication line 12 between the satellite station 1 and the ground station 2. By adjusting the utilization capacity depending on the state of each communication line 12, it is possible to reduce the delay in the arrival of downlink data generated by each satellite station 1 at the ground station 2.

The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

1 Satellite station, 2 ground station, 3,3a control station, 11 inter-satellite link, 12 communication line, 31 receiving unit, 32 transmitting unit, 33 line quality information collection unit, 34 destination control unit, 35 link fault information collection unit, 36 route control unit, 51 ground network, 100 satellite communication system.