Wireless communication system, wireless communication method, wireless communication device, and wireless communication program

Abstract

This wireless communication system comprises a terminal station, a terrestrial base station, a plurality of node stations constituting a non-terrestrial network; and a routing device. The terrestrial base station and at least one of the node stations are multi-carrier compatible stations comprising a first wireless child station corresponding to a first carrier and a second wireless child station corresponding to a second carrier. The routing device acquires the link capacity and traffic flow of communication routes leading to the multi-carrier compatible stations, and calculates congestion levels of the communication routes leading to the multi-carrier compatible stations on the basis of the link capacity and traffic flow. If the congestion level is at or above a threshold, the routing device chooses a communication route such that one of either the first or second carrier is accommodated by the wireless child stations provided in the multi-carrier compatible stations and the other is accommodated by a radio child station provided in a station different from the multi-carrier compatible stations. If the congestion level is below the threshold, the routing device chooses a communication route such that both the first and second carriers are accommodated by the wireless child stations provided in the multi-carrier compatible stations.

Description

Wireless communication system, wireless communication method, wireless communication device, and wireless communication program

[0001] The present disclosure relates to a wireless communication system, a wireless communication method, a wireless communication device, and a wireless communication program.

[0002] With the recent development of mobile communication systems, mobile services can now be enjoyed over most of the earth. One of the requirements for the 5th generation and later mobile communication systems, which are expected to be commercialized in the future, is ultra-coverage. Ultra-coverage refers to expanding the service area to places where the construction cost of existing base stations is high or difficult, such as mountains, oceans, or air.

[0003] To achieve the above, non-terrestrial networks (NTNs) using node stations such as satellites, unmanned aerial vehicles (UAVs), high altitude pseudo satellites (HAPS), or drones are gaining attention. In NTNs, node stations connect to each other via communication links to form a network, which is then connected to a terrestrial mobile network via a terrestrial base station. Traffic generated at terrestrial terminal stations is transferred within the NTN to a node station that can communicate with a terrestrial base station.

[0004] For example, Non-Patent Document 1 discloses a route control method in a hierarchical satellite network using NTN. In this route control method, wireless communication may be performed using carrier aggregation, which simultaneously uses multiple carriers managed by a single cellular base station.

[0005] Tada, Nishiyama, Yoshimura, and Kato, “A Study on Efficient Routing Control in Hierarchical Satellite Networks,” IEICE Technical Report SAT2010-9

[0006] When wireless communication is performed using the above-mentioned carrier aggregation, more traffic can be transmitted and received than when only one carrier is used. Therefore, there is a problem that the amount of traffic that exceeds the link capacity flows into the communication link, increasing the possibility of congestion.

[0007] In order to solve the above-mentioned problems, a first object of the present disclosure is to provide a wireless communication system that can avoid congestion even when transmitting and receiving a large amount of traffic by simultaneously using multiple carriers.

[0008] A first aspect of the present disclosure is a wireless communication system that uses a non-terrestrial network to perform communication using first and second carriers simultaneously, the wireless communication system including: a terminal station; a terrestrial base station; a plurality of node stations that constitute the non-terrestrial network; and a route control device, wherein at least one of the terrestrial base station and the node stations is a multi-carrier compatible station that has a first wireless slave station that corresponds to the first carrier and a second wireless slave station that corresponds to the second carrier, and the route control device is configured to perform the following processes: acquiring link capacity and traffic flow rate of a communication path leading to the multi-carrier compatible station; calculating a congestion degree of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; selecting a communication path such that one of the first and second carriers is accommodated in a wireless slave station equipped in the multi-carrier compatible station and the other is accommodated in a wireless slave station equipped in a station other than the multi-carrier compatible station, if the congestion degree is equal to or greater than a threshold; and selecting a communication path such that both the first and second carriers are accommodated in a wireless slave station equipped in the multi-carrier compatible station, if the congestion degree is less than the threshold.

[0009] A second aspect of the present disclosure is a wireless communication method implemented by a wireless communication system that uses a non-terrestrial network to perform communication using a first and a second carrier simultaneously, the wireless communication system preferably comprising: a terminal station; a terrestrial base station; a plurality of node stations that constitute the non-terrestrial network; and a route control device, wherein at least one of the terrestrial base station and the node stations is a multi-carrier compatible station that has a first wireless slave station that corresponds to the first carrier and a second wireless slave station that corresponds to the second carrier, and the route control device preferably comprises: acquiring a link capacity and a traffic flow rate of a communication path leading to the multi-carrier compatible station; calculating a congestion degree of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; selecting a communication path, if the congestion degree is equal to or greater than a threshold, such that one of the first and second carriers is accommodated in a wireless slave station equipped in the multi-carrier compatible station, and the other carrier is accommodated in a wireless slave station equipped in a station other than the multi-carrier compatible station; and selecting a communication path, if the congestion degree is less than the threshold, such that both the first and second carriers are accommodated in a wireless slave station equipped in the multi-carrier compatible station.

[0010] A third aspect of the present disclosure is a wireless communication device that uses a non-terrestrial network to perform communication simultaneously using a first and second carrier with a terminal station, a terrestrial base station, and a plurality of node stations that constitute the non-terrestrial network, wherein at least one of the terrestrial base station and the node station is a multi-carrier compatible station that includes a first wireless slave station that corresponds to the first carrier and a second wireless slave station that corresponds to the second carrier, and the wireless communication device is preferably configured to perform the following processes: a process of acquiring link capacity and traffic flow rate of a communication path leading to the multi-carrier compatible station; a process of calculating a congestion degree of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; a process of selecting a communication path such that one of the first and second carriers is accommodated in the wireless slave station included in the multi-carrier compatible station and the other is accommodated in a wireless slave station included in a station other than the multi-carrier compatible station, if the congestion degree is equal to or greater than a threshold; and a process of selecting a communication path such that both the first and second carriers are accommodated in the wireless slave station included in the multi-carrier compatible station, if the congestion degree is less than the threshold.

[0011] A fourth aspect of the present disclosure is a wireless communication program that causes a wireless communication device to communicate using a non-terrestrial network simultaneously with a terminal station, a terrestrial base station, and a plurality of node stations that constitute the non-terrestrial network, wherein at least one of the terrestrial base station and the node station is a multi-carrier compatible station that includes a first wireless slave station that corresponds to the first carrier and a second wireless slave station that corresponds to the second carrier, and the wireless communication program preferably includes a program that causes a computer to execute the following processes: a process of acquiring link capacity and traffic flow rate of a communication path leading to the multi-carrier compatible station; a process of calculating a congestion level of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; a process of selecting a communication path such that one of the first and second carriers is accommodated in the wireless slave station included in the multi-carrier compatible station and the other is accommodated in a wireless slave station included in a station other than the multi-carrier compatible station, if the congestion level is equal to or greater than a threshold; and a process of selecting a communication path such that both the first and second carriers are accommodated in the wireless slave station included in the multi-carrier compatible station, if the congestion level is less than the threshold.

[0012] According to the first to fourth aspects of the present disclosure, congestion can be avoided even when a large amount of traffic is transmitted and received by simultaneously using multiple carriers.

[0013] FIG. 1 is a diagram illustrating a wireless communication system according to a comparative example. FIG. 2 is a diagram illustrating switching in a wireless communication system according to embodiment 1 of the present disclosure. FIG. 3 is a diagram illustrating a configuration of a wireless communication system according to embodiment 1 of the present disclosure. FIG. 4 is a diagram illustrating a configuration of a wireless communication device mounted in a node station according to embodiment 1 of the present disclosure. FIG. 5 is a diagram illustrating a configuration of a network controller according to embodiment 1 of the present disclosure. FIG. 6 is a diagram illustrating a hardware configuration of a route control device according to embodiment 1 of the present disclosure. FIG. 7 is a flowchart illustrating processing performed by a wireless communication device according to embodiment 1 of the present disclosure. FIG. 8 is a diagram illustrating a first modified example of a wireless communication system according to embodiment 1 of the present disclosure. FIG. 9 is a diagram illustrating a second modified example of a wireless communication system according to embodiment 1 of the present disclosure. FIG. 10 is a diagram illustrating a third modified example of a wireless communication system according to embodiment 1 of the present disclosure. FIG. 11 is a diagram illustrating a fourth modified example of a wireless communication system according to embodiment 1 of the present disclosure. FIG. 12 is a diagram illustrating a wireless communication system according to embodiment 2 of the present disclosure.

[0014] First Embodiment [Wireless Communication System According to a Comparative Example] Fig. 1 is a diagram showing a wireless communication system according to a comparative example. Wireless communication system 500 includes a plurality of terminal stations 2. Terminal stations 2 are, for example, terminal stations installed on the ground. Traffic generated at terminal stations 2 is transmitted to terrestrial base station 4b. At this time, node stations 6c and 6d do not relay the traffic, but node stations 6a and 6b do. This communication path is referred to as communication path 14a.

[0015] The traffic communication on the communication path 14a will be described in more detail. This wireless communication system 500 performs communication using carrier aggregation, which simultaneously uses multiple carriers managed by a single cellular base station. Here, it is assumed that the terminal station 2 performs communication using two types of carriers, a PCC (Primary Component Carrier) and an SCC (Secondary Component Carrier), simultaneously. That is, the terminal station 2 is installed in an area where a PCC cell 22 and an SCC cell 24 overlap.

[0016] Traffic generated in the terminal station 2 is transmitted to the node station 6a via the service link 8. At this time, the service link 8 performs communication using two types of carriers, the PCC 26 and the SCC 28, simultaneously.

[0017] Traffic received by node station 6a is transmitted to node station 6b via communication link 10a, and then transmitted to terrestrial base station 4b via feeder link 12b. That is, traffic generated by terminal station 2 is transmitted to terrestrial base station 4b via communication path 14a.

[0018] Traffic received by the terrestrial base station 4b is transmitted to RUs 42b and 44b. RU 42b is a radio station (Radio Unit) accommodating a PCC, and RU 44b is a radio station accommodating an SCC. Traffic received by RUs 42b and 44b is transmitted to DU 46b. DU 46b is a distributed station (Distributed Unit). Traffic received by DU 46b is transmitted to CU 48b. CU 48b is a central station (Central Unit). Note that RUs 42b, RU 44b, DU 46b, and CU 48b are included in a cellular communication base station (gNB).

[0019] A terrestrial base station 4d is installed under the node station 6d. An RU 42d is installed under the terrestrial base station 4d, a DU 46d is installed under the RU 42d, and a CU 48d is installed under the DU 46d.

[0020] In the wireless communication system 500, wireless communication is performed using carrier aggregation, and therefore a large amount of traffic using the PCC 26 and the SCC 28 flows into the communication path 14a. As a result, there is a problem in that an amount of traffic exceeding the link capacity flows into the communication link, increasing the possibility of congestion. The present disclosure solves this problem.

[0021] [Wireless Communication System According to First Embodiment of the Present Disclosure] Fig. 2 is a diagram illustrating switching in a wireless communication system according to the first embodiment of the present disclosure. The configuration of the wireless communication system according to this embodiment is similar to that of the wireless communication system 500. However, the wireless communication system according to this embodiment differs from the wireless communication system 500 in that it switches between carrier aggregation and dual connectivity depending on the congestion state of the communication link being used.

[0022] The diagram on the left of Figure 2 shows carrier aggregation, and the diagram on the right shows communication when switched to dual connectivity. Carrier aggregation allows communication to be performed simultaneously using multiple carriers managed by a single cellular base station. On the other hand, dual connectivity allows communication to be performed simultaneously using carriers managed by multiple cellular base stations.

[0023] The communication shown in the left diagram of Fig. 2 is the same as that shown in Fig. 1, so a description thereof will be omitted. The parts of the right diagram of Fig. 2 that differ from the left diagram of Fig. 2 will be described.

[0024] Traffic generated in the terminal station 2 is transmitted to the node station 6a via the service link 8. At this time, the service link 8 performs communication using two types of carriers, the PCC 26 and the SCC 28, simultaneously.

[0025] Traffic received by node station 6a using PCC 26 is transmitted to node station 6b via communication link 10a and then to terrestrial base station 4b via feeder link 12b. That is, traffic transmitted from terminal station 2 using PCC 26 is transmitted to terrestrial base station 4b via communication path 14a.

[0026] The traffic received by the terrestrial base station 4b is transmitted to the RU 42b, the traffic received by the RU 42b is transmitted to the DU 46b, and the traffic received by the DU 46b is transmitted to the CU 48b.

[0027] Traffic received by node station 6a using SCC 28 is transmitted to node station 6c via communication link 10b and further to node station 6d via communication link 10c. This traffic is then transmitted to terrestrial base station 4d via feeder link 12d. That is, traffic transmitted from terminal station 2 using SCC 28 is transmitted to terrestrial base station 4d via communication path 14b.

[0028] The traffic received by the terrestrial base station 4d is transmitted to the RU 42d. The RU 42d is a wireless terminal that accommodates the SCC. The traffic received by the RU 42d is transmitted to the DU 46d. The traffic received by the DU 46d is transmitted to the CU 48d.

[0029] A method for switching between carrier aggregation and dual connectivity will now be described. First, the node station 6a calculates the congestion level α of the communication path 14a when communication is performed using carrier aggregation. The congestion level α is defined by Equation 1. Here, R is the link capacity [bps] of the communication link, and r is the traffic flow rate [bps] of the communication link.

[0030]

[0031] If α is less than the threshold, the node station 6a determines that the communication path 14a is not congested and selects carrier aggregation. If α is equal to or greater than the threshold, the node station 6a determines that the communication path 14a is congested and selects dual connectivity.

[0032] When dual connectivity is selected, new communication paths are set independently for the PCC 26 and the SCC 28. In other words, the RU accommodating the PCC 26 and the RU accommodating the SCC 28 are set to belong to different terrestrial base stations. This allows traffic to be distributed across multiple paths, thereby avoiding congestion.

[0033] 3 is a diagram illustrating a configuration of a wireless communication system according to the first embodiment of the present disclosure. The wireless communication system 100 includes an NTN 30 that relays communication between a terminal station 2 and a terrestrial base station 4.

[0034] The NTN 30 includes, for example, a network 32 having low-earth orbit satellites (LEO), a network 34 having medium-earth orbit satellites (MEO), and a network 36 having geostationary orbit satellites (GEO). The networks 32, 34, and 36 are networks made up of the same type of node stations, which can form communication links with each other, and the NTN 30 is formed by combining multiple networks. Other node stations that can be used include high-altitude pseudo satellites (HAPS), drones, unmanned aerial vehicles (UAVs), and aircraft. The communication links may be wireless or optical wireless.

[0035] In this way, the wireless communication system 100 includes a plurality of node stations in the sky, and the node stations are connected to one another via communication links. Communication links are also formed with the terrestrial base station 4, and networks are formed for each type of node station.

[0036] Furthermore, the NTN 30 is connected to a network controller 40. When the communication method of the wireless communication system 100 is a centralized control method, the network controller 40 performs processing necessary for calculating a communication path. The necessary processing is, for example, calculation of a congestion degree α.

[0037] When the communication method of the wireless communication system 100 is a distributed control method, the necessary processes described above are performed by each node station, eliminating the need for the network controller 40. Even when the communication method of the wireless communication system 100 is a centralized control method, the necessary processes described above are performed by each node station, eliminating the need for the network controller 40.

[0038] 4 is a diagram illustrating a configuration of a wireless communication device installed in a node station according to the first embodiment of the present disclosure. Here, an example will be described in which NTN control is performed using a distributed control method.

[0039] The wireless communication device 60 includes an inter-node communication device 62a. The inter-node communication device 62a connects a communication link with the node station 6a and performs communication. The wireless communication device 60 also includes inter-node communication devices 62b and 62c. The inter-node communication devices 62b and 62c connect communication links with the nearby node stations 6b and 6c and perform communication.

[0040] The wireless communication device 60 includes an inter-terminal station communication device 64. The inter-terminal station communication device 64 connects a communication link with the terminal station 2 and performs communication. The wireless communication device 60 also includes an inter-terrestrial base station communication device 66. The inter-terrestrial base station communication device 66 connects a communication link with the terrestrial base station 4 and performs communication.

[0041] The wireless communication device 60 includes a management device 68. The management device 68 aggregates information on each communication link obtained from the inter-node station communication devices 62a to 62c, the inter-terminal station communication device 64, and the terrestrial base station inter-communication device 66, and notifies the information to the route control device 70 and the management devices of adjacent node stations. This information includes the communication status of the communication links, such as congestion status and weather, and information required to calculate the congestion level α.

[0042] The route control device 70 calculates the congestion level α based on the notified information and determines whether to use carrier aggregation or dual connectivity for communication. Furthermore, the route control device 70 determines the communication route of the PCC 26 and SCC 28 and notifies the management device 68. The management device 68 notifies the node station, terminal station 2, and terrestrial base station 4 that form the communication link selected as the communication route of the corresponding communication route.

[0043] When the NTN is controlled by a centralized control system, the wireless communication device 60 does not determine the communication path, and therefore the path control device 70 is not required. In this case, information from the management device 68 is notified to the network controller 40, which will be described later with reference to Fig. 5. The network controller 40 then determines a communication path based on the notified information and notifies the management device 68.

[0044] 5 is a diagram illustrating a configuration of a network controller according to the first embodiment of the present disclosure. Here, an example in which NTN control is performed using a centralized control method will be described.

[0045] The network controller 40 includes a management device 68. The management device 68 aggregates information about each communication link notified by the node stations and notifies the route control device 70. The route control device 70 calculates a congestion level α based on the notified information and determines whether to use carrier aggregation or dual connectivity for communication. Furthermore, the route control device 70 determines the communication paths of the PCC 26 and SCC 28 and notifies the management device 68. The management device 68 notifies the node stations, terminal stations 2, and terrestrial base stations 4 that form the communication links selected as the communication paths of the corresponding communication paths.

[0046] 6 is a diagram illustrating a hardware configuration of a route control device according to the first embodiment of the present disclosure. The route control device 70 includes a CPU 118. The CPU 118 is connected to a bus line 120. Memory devices such as a ROM 122, a RAM 124, and a storage 126 are connected to the bus line 120. A wireless communication program executed by the CPU 118 is stored in the memory device. The route control device 70 can realize functions specific to this embodiment by the CPU 118 executing the wireless communication program.

[0047] A communication interface 128 is also connected to the bus line 120. The route control device 70 communicates with the network via the communication interface 128. An operation unit 130 and a display unit 132 are also connected to the bus line 120. The operation unit 130 and the display unit 132 function as a user interface for operating the route control device 70.

[0048] As described above, the route control device 70 can realize the functions specific to this embodiment by the CPU 118 executing the wireless communication program. That is, the route control device 70 can also be realized by a computer and the program. The program can also be recorded on a recording medium or provided via a network.

[0049] 7 is a flowchart showing processing performed by the wireless communication device according to the first embodiment of the present disclosure. First, in step 100, a congestion level α of a communication link is calculated. Next, in step 102, it is confirmed whether the congestion level α is equal to or greater than a threshold. If it is equal to or greater than the threshold, the process proceeds to step 104. If it is less than the threshold, the process proceeds to step 110.

[0050] In step 104, it is determined that the communication link is congested, and a selection is made to communicate using dual connectivity. Next, in step 106, a communication path for the PCC 26 is selected. Next, in step 108, a communication path for the SCC 28 is selected, and the process ends. At this time, the communication paths are selected so that one of the PCC 26 and the SCC 28 is accommodated in an RU provided in a terrestrial base station that supports multiple carriers, and the other is accommodated in an RU provided in another terrestrial base station.

[0051] In step 110, it is determined that the communication link is not congested, and carrier aggregation is used for communication. Next, in step 112, a communication path between the PCC 26 and the SCC 28 is selected, and the process ends. At this time, the communication path is selected so that both the PCC 26 and the SCC 28 are accommodated in an RU provided in a terrestrial base station that supports multiple carriers.

[0052] As described above, this embodiment enables flexible communication path setting based on the value of the congestion degree α, which makes it possible to avoid congestion even when a large amount of traffic is transmitted and received by simultaneously using multiple carriers.

[0053] [Modification of the Wireless Communication System According to the First Embodiment of the Present Disclosure] Figure 8 is a diagram showing a first modification of the wireless communication system according to the first embodiment of the present disclosure. DUs arranged one by one under each node station may be accommodated together in a single CU. For example, DUs 46a, 46b, and 46c arranged one by one under node stations 6a, 6b, and 6c may be accommodated together in a single CU 48.

[0054] Furthermore, RUs under multiple node stations may be housed together in a single DU. For example, RUs 42d and 44d under node station 6d and RUs 42e and 44e under node station 6e may be housed together in a single DU 46.

[0055] Furthermore, a CU that accommodates a plurality of CUs may be arranged. For example, a CU 50 that accommodates CU 48 and CU 49 may be arranged.

[0056] 9 is a diagram illustrating a second modification of the wireless communication system according to the first embodiment of the present disclosure. A node station may include some or all of the CU, DU, and RU. For example, node station 6e may include RUs 61e and 63e, and node station 6f may include RUs 61f and 63f.

[0057] In this modification, when communication is performed using carrier aggregation, the PCC 26 is accommodated in the RU 61 e, and the SCC 28 is accommodated in the RU 63 e. That is, traffic generated in the terminal station 2 is transmitted to the terrestrial base station 4 e via the communication path 16 a.

[0058] Furthermore, when communication is performed using dual connectivity in this modification, the PCC 26 is accommodated in the RU 61e, and the SCC 28 is accommodated in the RU 61f. That is, traffic transmitted from the terminal station 2 using the PCC 26 is transmitted to the terrestrial base station 4e via the communication path 16a. Furthermore, traffic transmitted from the terminal station 2 using the SCC 28 is transmitted to the terrestrial base station 4f via the communication path 16b.

[0059] 10 is a diagram illustrating a third modified example of the wireless communication system according to the first embodiment of the present disclosure. The node stations included in the communication path may be not only node stations in the sky but also node stations on the ground. In other words, the terrestrial base station may communicate directly with the terminal station without going through the node station.

[0060] For example, the communication path used when communicating using dual connectivity may be a communication path 14c that directly connects to the terrestrial node station 5. The terrestrial node station 5 includes an RU 52, an RU 54, a DU 56, and a CU 58, similar to the terrestrial base station 4a.

[0061] Furthermore, when communication is performed using dual connectivity in this modification, the PCC 26 is accommodated in the RU 42b, and the SCC 28 is accommodated in the RU 52. That is, traffic transmitted from the terminal station 2 using the PCC 26 is transmitted to the terrestrial base station 4b via the communication path 14a. Furthermore, traffic transmitted from the terminal station 2 using the SCC 28 is transmitted to the terrestrial node station 5 via the communication path 14c.

[0062] 11 is a diagram illustrating a fourth modification of the wireless communication system according to the first embodiment of the present disclosure. The node stations included in the communication path may be different types of node stations installed in the sky. For example, the node stations included in the communication path may include a first altitude station that is a node station installed at a first altitude and a second altitude station that is installed at a second altitude.

[0063] For example, the communication path used when communicating using dual connectivity may be not only the node stations 6a and 6b of the network 32 but also the node stations 7a and 7b of the network 34. In this case, the node stations 6a and 6b are first altitude stations, and the node stations 7a and 7b are second altitude stations. The node station 7b of the network 32 has a terrestrial base station 4g under its control. The terrestrial base station 4g has an RU 42g, an RU 44g, a DU 46g, and a CU 48g under its control.

[0064] Furthermore, when communication is performed using dual connectivity in this modification, the PCC 26 is accommodated in the RU 42b, and the SCC 28 is accommodated in the RU 42g. That is, traffic transmitted from the terminal station 2 using the PCC 26 is transmitted to the terrestrial base station 4b via the communication path 14a. Furthermore, traffic transmitted from the terminal station 2 using the SCC 28 is transmitted to the terrestrial base station 4g via the communication path 14d.

[0065] 12 is a diagram illustrating a wireless communication system according to a second embodiment of the present disclosure. The second embodiment differs from the first embodiment in that the communication method is a centralized control method and that the network controller is arranged in the absolute node station.

[0066] Recently, there has been a need to make the nation more resilient against natural disasters, etc., and the emergence of a communication system that is resistant to terrestrial disasters is desired. In this embodiment, by placing a network controller in the sky, NTN route control can be performed without being affected by terrestrial disasters.

[0067] The wireless communication system 200 includes an absolute node station 71. The absolute node station 71 is, for example, a GEO satellite. The absolute node station 71 is installed in the sky and is a node station that can establish direct communication links with all node stations included in the system. The absolute node station 71 is connected to node stations 6a to 6d via communication links 72a to 72d. The absolute node station 71 has a wide communication area and can communicate directly with all node stations that make up the NTN. This embodiment makes use of this feature.

[0068] Furthermore, the absolute node station 71 has a network controller 40. The network controller 40 implements a protocol for collecting information necessary to calculate the congestion degree α.

[0069] The node stations 6a to 6d notify the absolute node station 71 of information necessary for calculating the congestion level α via the communication links 72a to 72d. The absolute node station 71 calculates the congestion level α based on the notified information and determines a communication route. The absolute node station 71 then notifies the node stations 6a to 6d of information about the determined communication route.

[0070] The absolute node station 71 may exchange information by directly communicating with each node station, or may exchange information via a plurality of node stations.

[0071] As described above, in this embodiment, congestion can be avoided when transmitting and receiving a large amount of traffic by using multiple carriers simultaneously, without being affected by terrestrial disasters.

[0072] 2 Terminal station 4, 4a, 4b, 4d, 4e, 4f, 4g Terrestrial base station 5 Node station 6a, 6b, 6c, 6d, 6e, 6f Node station 7a, 7b Node station 16a, 16b Communication path 14a, 14b, 14c, 14d Communication path 32, 34, 36 Network 60 Wireless communication device 70 Route control device 71 Absolute node station 100, 200, 500 Wireless communication system

Claims

1. A wireless communication system that uses a non-terrestrial network to perform communication using a first and second carriers simultaneously, comprising: a terminal station, a terrestrial base station, a plurality of node stations constituting the non-terrestrial network, and a route control device, wherein at least one of the terrestrial base station and the node stations is a multi-carrier compatible station equipped with a first wireless sub station corresponding to the first carrier and a second wireless sub station corresponding to the second carrier, and the route control device is configured to perform the following processes: acquiring link capacity and traffic flow rate of a communication path leading to the multi-carrier compatible station; calculating a congestion degree of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; selecting a communication path such that one of the first and second carriers is accommodated in a wireless sub station equipped in the multi-carrier compatible station and the other is accommodated in a wireless sub station equipped in a station other than the multi-carrier compatible station, when the congestion degree is equal to or greater than a threshold; and selecting a communication path such that both of the first and second carriers are accommodated in a wireless sub station equipped in the multi-carrier compatible station, when the congestion degree is less than the threshold.

2. The wireless communication system according to claim 1, wherein the node station comprises some or all of a wireless slave station, a remote station and a central station.

3. The wireless communication system according to claim 1, wherein said terrestrial base station is capable of communicating with said terminal station without going through said node station.

4. A wireless communication system according to claim 1, wherein the node stations include a first altitude station which is a node station installed at a first altitude, and a second altitude station which is a node station installed at a second altitude.

5. The wireless communication system according to claim 1, further comprising an absolute node station capable of directly communicating with all node stations constituting said non-terrestrial network, said absolute node station comprising said route control device.

6. A wireless communication method implemented by a wireless communication system that uses a non-terrestrial network to perform communication simultaneously using a first and a second carrier, the wireless communication system comprising a terminal station, a terrestrial base station, a plurality of node stations constituting the non-terrestrial network, and a route control device, at least one of the terrestrial base station and the node stations being a multi-carrier compatible station having a first wireless slave station corresponding to the first carrier and a second wireless slave station corresponding to the second carrier, the route control device: acquiring link capacity and traffic flow rate of a communication path leading to the multi-carrier compatible station; calculating a congestion degree of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; if the congestion degree is equal to or greater than a threshold, selecting a communication path such that one of the first and second carriers is accommodated in a wireless slave station provided in the multi-carrier compatible station and the other is accommodated in a wireless slave station provided in a station other than the multi-carrier compatible station; if the congestion degree is less than the threshold, selecting a communication path such that both of the first and second carriers are accommodated in a wireless slave station provided in the multi-carrier compatible station. A wireless communication method comprising:

7. A wireless communication device that uses a non-terrestrial network to communicate simultaneously using a first and second carrier with a terminal station, a terrestrial base station, and multiple node stations that constitute the non-terrestrial network, wherein at least one of the terrestrial base station and the node stations is a multi-carrier compatible station equipped with a first wireless sub station corresponding to the first carrier and a second wireless sub station corresponding to the second carrier, and the wireless communication device is configured to perform the following processes: acquiring link capacity and traffic flow rate of a communication path leading to the multi-carrier compatible station; calculating a congestion degree of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; selecting a communication path such that one of the first and second carriers is accommodated in a wireless sub station equipped in the multi-carrier compatible station and the other is accommodated in a wireless sub station equipped in a station other than the multi-carrier compatible station, when the congestion degree is equal to or greater than a threshold; and selecting a communication path such that both of the first and second carriers are accommodated in a wireless sub station equipped in the multi-carrier compatible station, when the congestion degree is less than the threshold.

8. A wireless communication program for causing a wireless communication device to communicate using a non-terrestrial network simultaneously using a first and second carrier with a terminal station, a terrestrial base station, and a plurality of node stations constituting the non-terrestrial network, wherein at least one of the terrestrial base station and the node stations is a multi-carrier compatible station equipped with a first wireless sub station corresponding to the first carrier and a second wireless sub station corresponding to the second carrier, the wireless communication program including a program for causing a computer to execute the following processes: a process for acquiring link capacity and traffic flow rate of a communication path leading to the multi-carrier compatible station; a process for calculating a congestion degree of the communication path leading to the multi-carrier compatible station based on the link capacity and the traffic flow rate; a process for selecting a communication path such that one of the first and second carriers is accommodated in a wireless sub station equipped in the multi-carrier compatible station and the other is accommodated in a wireless sub station equipped in a station other than the multi-carrier compatible station, if the congestion degree is equal to or greater than a threshold; and a process for selecting a communication path such that both of the first and second carriers are accommodated in a wireless sub station equipped in the multi-carrier compatible station, if the congestion degree is less than the threshold.

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