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

Abstract

The present invention provides a wireless communication system capable of determining a node station to which a terminal station is connected such that congestion can be suppressed. To this end, the wireless communication system in which a terminal station and a base station communicate via a non-terrestrial communication network comprises: a connection candidate node station specification unit that specifies connection candidate node stations for the terminal station from among a plurality of node stations in the non-terrestrial communication network; a communication route specification unit that specifies communication routes that can each transmit / receive traffic to / from the base station via any of the connection candidate node stations; a cost calculation unit that calculates the cost value of each communication route; and a connection node station determination unit that determines, as a connection node station, a connection candidate node station to which the terminal station needs to be connected in order to communicate with the base station via a communication route having a minimum cost value. The cost calculation unit uses the traffic transmission capacity and traffic flow rate of each of communication links between the node stations in a communication route to calculate the cost value of the communication route.

Description

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

[0001] This disclosure relates to wireless communication systems, wireless communication devices, wireless communication methods, and wireless communication programs.

[0002] In routing control in hierarchical satellite networks, it is known that the link cost is the sum of propagation delay and queuing delay, and the communication delay of each traffic is determined by the sum of the link costs of each link it passes through, i.e., the sum of each propagation delay and each queuing delay (see, for example, Patent Document 1).

[0003] Tada, Nishiyama, Yoshimura, Kato, "A Study on Efficient Routing Control in Hierarchical Satellite Networks," IEICE Technical Review, Institute of Electronics, Information and Communication Engineers, SAT2010-9 (2010-6), pp. 45-50.

[0004] In recent years, the importance of wireless communication using non-terrestrial networks (NTN) has been increasing. However, routing methods such as those described in Non-Patent Document 1 only consider the communication delay of traffic on each communication link and do not consider traffic flow. Therefore, in a wireless communication system in which terminal stations and base stations communicate via a non-terrestrial communication network, if routing methods such as those described in Non-Patent Document 1 are used when a terminal station determines which node station to connect to, the traffic flow on the communication route from the node station to the base station is not considered. As a result, there is a possibility that congestion may occur due to an influx of traffic exceeding the transmission capacity of the communication link.

[0005] This disclosure was made to solve these problems. Its purpose is to provide a wireless communication system, wireless communication device, wireless communication method, and wireless communication program that can take into account the traffic status (congestion) of each communication link constituting the communication network when a terminal station determines which node station to connect to, and thereby can avoid congestion.

[0006] The wireless communication system according to this disclosure is a wireless communication system in which a terminal station and a base station communicate via a non-terrestrial communication network, comprising: a connection candidate node station identification unit that identifies candidate connection candidate node stations from among a plurality of node stations of the non-terrestrial communication network to which the terminal station will connect; a communication route identification unit that identifies a communication route to which traffic can be transmitted and received with the base station via any of the connection candidate node stations; a cost calculation unit that calculates the cost value of each of the communication routes; and a connection node station determination unit that determines the connection candidate node station to be the connection node station that the terminal station needs to connect to in order to communicate with the base station via the communication route that minimizes the cost value, wherein the terminal station connects to the connection node station, and the cost calculation unit calculates the cost value of the communication route using at least the traffic transmission capacity of each communication link between each of the node stations in the communication route and the traffic flow rate of each communication link.

[0007] The wireless communication device according to this disclosure is a wireless communication device included in a wireless communication system in which a terminal station and a base station communicate via a non-terrestrial communication network, and comprises: a connection candidate node station identification unit that identifies a candidate connection candidate node station from among a plurality of node stations of the non-terrestrial communication network to which the terminal station will connect; a communication route identification unit that identifies a communication route to which traffic can be transmitted and received with the base station via any of the connection candidate node stations; a cost calculation unit that calculates the cost value of each of the communication routes; and a connection node station determination unit that determines the connection candidate node station to be the connection node station that the terminal station needs to connect to in order to communicate with the base station via the communication route with the minimum cost value, wherein the terminal station connects to the connection node station, and the cost calculation unit calculates the cost value of the communication route using at least the traffic transmission capacity of each communication link between each of the node stations in the communication route and the traffic flow rate of each communication link.

[0008] The wireless communication method according to the present disclosure is a wireless communication method in which a terminal station and a base station communicate via a non-terrestrial communication network, including a connection candidate node station identification step of identifying a connection candidate node station that is a candidate for the node station to be connected by the terminal station from among a plurality of node stations of the non-terrestrial communication network, a communication route identification step of identifying a communication route through which traffic can be transmitted and received with the base station via any one of the connection candidate node stations, a cost calculation step of calculating a cost value for each of the communication routes, and a connection node station determination step of determining the connection candidate node station that needs to be connected by the terminal station to communicate with the base station via the communication route having the minimum cost value. The cost calculation step calculates the cost value of the communication route using at least the traffic transmission capacity between each of the node stations in the communication route and the traffic flow of each of the communication links.

[0009] The wireless communication program according to the present disclosure is a program for causing a computer of a wireless communication device included in a wireless communication system in which a terminal station and a base station communicate via a non-terrestrial communication network to execute the above-described wireless communication method.

[0010] According to the wireless communication system, wireless communication device, wireless communication method, and wireless communication program of the present disclosure, when determining the node station to be connected by the terminal station, the traffic state (congestion state) of each communication link constituting the communication network can be taken into consideration, and thus the effect of avoiding congestion can be achieved.

[0011] This is a diagram showing the overall configuration of the wireless communication system according to Embodiment 1. This is a block diagram showing the configuration of the communication device mounted on the node station of the wireless communication system according to Embodiment 1. This is a block diagram showing the configuration of the network controller of the wireless communication system according to Embodiment 1. This is a diagram illustrating the flow of information centered on the network controller of the wireless communication system according to Embodiment 1. This is a block diagram illustrating the configuration of the connection destination control device of the wireless communication system according to Embodiment 1. This is a flowchart showing an example of the operation of the wireless communication system according to Embodiment 1. This is a diagram illustrating a specific example of connection destination control in the wireless communication system according to Embodiment 1. This is a diagram illustrating a modified example of connection destination control in a conventional wireless communication system, which is a comparative example. This is a diagram illustrating a modified example of connection destination control in the wireless communication system according to Embodiment 1.

[0012] The embodiments for implementing the wireless communication system, wireless communication device, wireless communication method, and wireless communication program relating to this disclosure will be described with reference to the attached drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are simplified or omitted as appropriate. For convenience, the positional relationships of each structure may be expressed based on the illustrated state in the following description. This disclosure is not limited to the embodiments described below, and any combination of embodiments, any modification of any component of each embodiment, or any omission of any component of each embodiment is possible without departing from the spirit of this disclosure.

[0013] Embodiment 1. Referring to FIGS. 1 to 9, Embodiment 1 of the present disclosure will be described. FIG. 1 is a diagram showing the overall configuration of a wireless communication system. FIG. 2 is a block diagram showing the configuration of a communication device mounted on a node station of the wireless communication system. FIG. 3 is a block diagram showing the configuration of a network controller of the wireless communication system. FIG. 4 is a diagram for explaining the flow of information centered on the network controller of the wireless communication system. FIG. 5 is a block diagram showing the configuration of a connection destination control device of the wireless communication system. FIG. 6 is a flowchart showing an example of the operation of the wireless communication system. FIG. 7 is a diagram for explaining a specific example of connection destination control of the wireless communication system. FIG. 8 is a diagram for explaining a specific example of connection destination control in a conventional wireless communication system which is a comparative example. FIG. 9 is a diagram for explaining a modified example of connection destination control of the wireless communication system.

[0014] The wireless communication system according to this embodiment is one in which the terminal station 100 and the base station 200 communicate via the non-terrestrial communication network 300. The non-terrestrial communication network 300 consists of a plurality of node stations 400. The types of the node stations 400 may include, for example, geostationary (GEO: Geosynchronous Orbit) satellites including stationary satellites, medium earth orbit (MEO: Medium Earth Orbit) satellites, low earth orbit (LEO: Low Earth Orbit) satellites, high altitude pseudo satellites (HAPS: High Altitude Platform Station, also referred to as high altitude platform), drones, unmanned aerial vehicles (UAV: Unmanned Aerial Vehicle), aircraft, and the like.

[0015] The non-terrestrial communication network 300 may be a set of communication networks configured for each type of the node station 400. That is, the non-terrestrial communication network 300 may consist of one communication network or may include a plurality of communication networks. In the example shown in FIG. 1, the non-terrestrial communication network 300 includes three communication networks, namely, non-terrestrial communication network (A), non-terrestrial communication network (B), and non-terrestrial communication network (C).

[0016] In the illustrated example, non-terrestrial communication network (A) has node stations 400, namely node station (A1), node station (A2), node station (A3), ... and non-terrestrial communication network (B) has node stations 400, namely node station (B1), node station (B2), node station (B3), ... and non-terrestrial communication network (C) has node stations 400, namely node station (C1), node station (C2), node station (C3), ...

[0017] Each node station 400 is equipped with a node station-mounted communication device 410. As shown in Figure 2, the node station-mounted communication device 410 includes an inter-node station communication unit 411, an inter-base station communication unit 412, an inter-terminal station communication unit 413, and a node station management unit 414. The inter-node station communication unit 411 establishes a communication link between the node station 400 and a node station 400 adjacent to it. The inter-node station communication unit 411 then communicates between the node station 400 with which the communication link has been established and the node station 400.

[0018] The inter-base station communication unit 412 establishes a communication link between the node station 400 and the base station 200. The inter-terminal station communication unit 413 then communicates between the base station 200, which has established the communication link, and the node station 400. The inter-terminal station communication unit 413 establishes a communication link between the node station 400 and the terminal station 100. The inter-terminal station communication unit 413 then communicates between the terminal station 100, which has established the communication link, and the node station 400.

[0019] The node station management unit 414 manages the information necessary for calculating the cost value of the communication route, which will be described later. Specifically, for example, the node station management unit 414 measures or acquires the traffic transmission capacity, traffic flow rate, and delay time of the communication link of the node station 400. The node station management unit 414 then transmits this acquired information to the network controller 500 located in the aggregate node station 401, which will be described later.

[0020] The node stations 400 of the non-terrestrial communication network 300 may include an aggregate node station 401. The aggregate node station 401 is a node station 400 that can communicate with all other node stations 400 and terminal stations 100. In this case, the node station-mounted communication device 410 further includes an aggregate node station-to-node communication unit 415, as shown in Figure 2. The aggregate node station-to-node communication unit 415 establishes a communication link between the node station 400 and the aggregate node station 401. The aggregate node station-to-node communication unit 415 then communicates between the aggregate node station 401 with which the communication link has been established and the node station 400. This enables communication between aggregate node stations 401 and between aggregate node stations 401 and node stations 400 that are not aggregate node stations 401.

[0021] The wireless communication system according to this embodiment includes a network controller 500. The network controller 500 is installed, for example, in the aforementioned aggregation node station 401. As shown in Figure 3, the network controller 500 includes a network management device 510 and a connection destination control device 520. As shown in Figure 4, information transmitted from the node station 400 is aggregated in the network controller 500. The network management device 510 manages this aggregated information. That is, the network management device 510 stores and manages information such as traffic transmission capacity, traffic flow rate, and delay time for the communication links of each node station 400, which is transmitted from the node station-mounted communication device 410. The network management device 510 also notifies the connection destination control device 520 of this managed information.

[0022] The connection destination control device 520 determines the connection destinations for the terminal station 100 and each node station 400 based on the information notified by the network management device 510. That is, the connection destination control device 520 determines the node station 400 to which the terminal station 100 will connect, i.e., the node station 400 with which the terminal station 100 will establish a communication link. The connection destination control device 520 also determines the node station 400 to which each node station 400 will connect, i.e., the node station 400 with which each node station 400 will establish a communication link. The network controller 500 notifies the terminal station 100 and each node station 400 of the connection destinations determined by the connection destination control device 520. The terminal station 100 and each node station 400 connect to the node station 400 that is the connection destination notified by the network controller.

[0023] Next, the configuration related to determining the node station 400 to which the terminal station 100 connects in the wireless communication system according to this embodiment will be described in more detail. In the wireless communication system according to this embodiment, the connection destination control device 520 of the network controller 500 includes a candidate node station identification unit 521, a communication route identification unit 522, a cost calculation unit 523, and a connection node station determination unit 524, as shown in Figure 5.

[0024] The connected control device 520 includes a computer with a processor and memory as hardware. The processor is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory includes, for example, non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM, or magnetic disks, flexible disks, optical disks, compact disks, minidiscs, and DVDs.

[0025] The memory of the connection destination control device 520 stores a program as software. The connection destination control device 520 then performs pre-configured processing by having the processor execute the program stored in memory, and as a result of the cooperation between hardware and software, the functions of the connection candidate node station identification unit 521, the communication route identification unit 522, the cost calculation unit 523, and the connection node station determination unit 524 are realized.

[0026] The connection candidate node station identification unit 521 identifies one or more connection candidate node stations from among the multiple node stations 400 of the non-terrestrial communication network 300. A connection candidate node station is a candidate node station 400 to which the terminal station 100 will connect. For example, the connection candidate node station identification unit 521 identifies a node station 400 as a connection candidate node station among the multiple node stations 400 in which the received C / N (Carrier-to-Noise Ratio) at the terminal station 100 is equal to or greater than a preset reference value.

[0027] The communication route identification unit 522 identifies a communication route that allows traffic transmission and reception with the base station 200 via one of the candidate connection node stations. The cost calculation unit 523 then calculates a cost value for each of the communication routes identified by the communication route identification unit 522. The cost calculation unit 523 calculates the cost value of the communication route by using at least the traffic transmission capacity and traffic flow rate of each communication link between each node station 400 in the communication route. The cost calculation unit 523 may further use the delay time of each communication link between each node station 400 in the communication route to calculate the cost value of the communication route.

[0028] As a more specific example, the cost calculation unit 523 calculates the cost value C of each communication route using the following equations (1) to (3). In these equations (1) to (3), n is the total number of links included in the communication route, and C ｉ R is the cost value of communication link i. ｉ is the traffic transmission capacity of communication link i, r ｉ δ is the traffic flow rate of communication link i. ｉis the traffic congestion level of communication link i, B ｒ is the reference value of link capacity, d ｉ is the delay time of communication link i, B ｄ is the reference value of the delay time. The reference value B of the link capacity ｒ and the reference value B of the delay time ｄ are preset. The reference value B of the link capacity ｒ and the reference value B of the delay time ｄ are stored, for example, in the storage device of the network controller 500, etc.

[0029]

[0030]

[0031]

[0032] The connection node station determination unit 524 determines the candidate connection node stations that the terminal station 100 needs to connect to in order to communicate with the base station 200 via the communication route with the minimum cost value calculated by the cost calculation unit 523 as the connection node stations. In this way, the connection destination control device 520 determines the connection node station, which is the node station 400 where the terminal station 100 connects, based on the information notified from the network management device 510.

[0033] As shown in FIG. 4, the information of the connection node station determined by the connection node station determination unit 524 is transmitted from the aggregation node station 401 where the network controller 500 is arranged to the terminal station 100. At this time, it may be directly notified to the terminal station 100 via the link for control result notification from the aggregation node station 401, or it may be notified to the terminal station 100 via the terrestrial relay station 600.

[0034] Furthermore, the network controller 500 may be located on the ground instead of at the aerial aggregation node station 401. The functions of the network controller 500 may be distributed to each node station 400 instead of at the aggregation node station 401. Alternatively, the connection destination control device 520 of the network controller 500 may be provided at each terminal station 100. In addition, only some of the functions of the connection destination control device 520, such as the connection candidate node station identification unit 521, the communication route identification unit 522, the cost calculation unit 523, and the connection node station determination unit 524, may be provided at each terminal station 100. In other words, the connection destination control device 520 is an example of a wireless communication device provided in a wireless communication system, and such a wireless communication device may be provided at the network controller 500, each terminal station 100, each node station 400, etc.

[0035] Next, with reference to the flowchart in Figure 6, an example of the operation of the connection destination control device 520 in the wireless communication system according to this embodiment will be described. First, in step S10, the connection candidate node station identification unit 521 of the connection destination control device 520 detects a node station 400 to which the terminal station 100 can connect. A node station 400 to which the terminal station 100 can connect is, for example, a node station 400 to which the received C / N at the terminal station 100 is equal to or greater than the aforementioned reference value, as described above.

[0036] If no node station 400 that can be connected to the terminal station 100 is detected, that is, if there is no node station 400 whose received C / N at the terminal station 100 is equal to or greater than the reference value, the series of processes ends. On the other hand, if a node station 400 that can be connected to the terminal station 100 is detected, that is, if there is a node station 400 whose received C / N at the terminal station 100 is equal to or greater than the reference value, the connection candidate node station identification unit 521 identifies the node station 400 whose received C / N at the terminal station 100 is equal to or greater than the reference value as a connection candidate node station. Then, the connection destination control device 520 performs the process of step S11.

[0037] In step S11, the connection node station determination unit 524 of the connection destination control device 520 determines whether there are two or more node stations 400 that the terminal station 100 can connect to, that is, whether there are two or more candidate connection node stations identified in step S10. If there are not two or more candidate connection node stations, that is, if there is only one candidate connection node station, the connection destination control device 520 then performs the process in step S12.

[0038] In step S12, the node station 400 that the terminal station 100 can connect to, i.e., the candidate node station, is determined to be the destination of the communication link of the terminal station 100, i.e., the connected node station. Then, the series of processes is completed.

[0039] On the other hand, if there are two or more candidate node stations in step S11, the destination control device 520 then performs the process in step S13. In step S13, the communication route identification unit 522 of the destination control device 520 identifies a communication route through which the terminal station 100 can send and receive traffic with the base station 200 via one of the candidate node stations identified in step S10. In the following step S14, the cost calculation unit 523 of the destination control device 520 calculates the cost value of each communication route identified in step S13. After step S14, the destination control device 520 then performs the process in step S15.

[0040] In step S15, the connection node station determination unit 524 of the connection destination control device 520 identifies the communication route that minimizes the cost value calculated in step S14. In the following step S16, the connection node station determination unit 524 of the connection destination control device 520 determines the node station 400 that the terminal station 100 needs to connect to in order to communicate with the base station 200 via the communication route that minimizes the cost value identified in step S15 as the connection destination of the communication link of the terminal station 100, i.e., the connection node station. The series of operations then ends.

[0041] In the wireless communication method described above, in which a terminal station 100 and a base station 200 communicate via a non-terrestrial communication network 300, step S10 corresponds to the candidate node station identification step. The candidate node station identification step is the step of identifying candidate node stations from among a plurality of node stations 400 of the non-terrestrial communication network 300 that are candidates for the node station 400 to which the terminal station 100 will connect. Step S13 corresponds to the communication route identification step. The communication route identification step is the step of identifying a communication route that enables traffic transmission and reception with the base station 200 via one of the candidate node stations.

[0042] Step S14 corresponds to the cost calculation step. The cost calculation step is a step to calculate the cost value of each communication route. This cost calculation step calculates the cost value of the communication route using at least the traffic transmission capacity of each communication link between each node station 400 in the communication route and the traffic flow rate of each communication link.

[0043] Steps S11, S12, S15, and S16 correspond to the connection node station determination step. The connection node station determination step is the step of determining the connection node station to be a candidate connection node station that the terminal station 100 needs to connect to in order to communicate with the base station 200 via the communication route with the minimum cost value.

[0044] Furthermore, as mentioned above, if the connection destination control device 520 is equipped with a computer, the program causes the computer of the connection destination control device 520 to function as the connection candidate node station identification unit 521, the communication route identification unit 522, the cost calculation unit 523, and the connection node station determination unit 524. This program is a wireless communication program for operating the wireless communication equipment provided in the wireless communication system. This program is also a wireless communication program that causes the computer of the connection destination control device 520 to execute the wireless communication method described above. This wireless communication program causes the computer of the connection destination control device 520 to execute the connection candidate node station identification step, the communication route identification step, the cost calculation step, and the connection node station determination step described above. The storage medium according to this disclosure is a computer-readable storage medium that stores such a wireless communication program.

[0045] Next, with reference to Figure 7, a specific example of how to determine the node station 400 to which the terminal station 100 connects in the wireless communication system according to this embodiment will be described. In the example described here, the reference value B of the link capacity ｒ = 100 [Mbps], reference value B for delay time ｄ Let = 1 [ms].

[0046] First, the connection candidate node station identification unit 521 identifies three node stations, node station (A1), node station (A2), and node station (B2), as connection candidate node stations based on the received C / N from each node station 400 at terminal station (C). Then, the communication route identification unit 522 identifies five communication routes, from route A1 to route C1, as communication routes through which terminal station (C) can send and receive traffic with base station 200 via any of these connection candidate node stations.

[0047] Route A1: Terminal station (C) - Node station (A2) - Base station 200 Route A2: Terminal station (C) - Node station (A2) - Node station (A3) - Base station 200 Route B1: Terminal station (C) - Node station (A1) - Base station 200 Route C1: Terminal station (C) - Node station (B2) - Base station 200 Route C2: Terminal station (C) - Node station (B2) - Node station (B3) - Base station 200

[0048] Here, the traffic transmission capacity R in each communication link ｉ , traffic flow r ｉ and delay time d ｉ These are as follows:

[0049] Link A (communication link between terminal station (C) and node station (A2)): ・R ｉ =100 [Mbps] ・r ｉ =0 [Mbps] ・d ｉ = 1 [ms]

[0050] Link A1 (communication link between node station (A2) and base station 200): ・R ｉ =100 [Mbps] ・r ｉ =90 [Mbps] ・d ｉ = 1 [ms]

[0051] Link A2 (communication link between node station (A2) and node station (A3): ・R ｉ =100 [Mbps] ・r ｉ =10 [Mbps] ・d ｉ = 2 [ms]

[0052] Link A3 (communication link between node station (A3) and base station 200): ・R ｉ =100 [Mbps] ・r ｉ =5 [Mbps] ・d ｉ = 1 [ms]

[0053] Link B (communication link between terminal station (C) and node station (A1)): ・R ｉ =100 [Mbps] ・r ｉ =0 [Mbps] ・d ｉ = 1 [ms]

[0054] Link B1 (communication link between node station (A1) and base station 200): ・R ｉ =100 [Mbps] ・r ｉ =80 [Mbps] ・d ｉ = 1 [ms]

[0055] Link C (communication link between terminal station (C) and node station (B2)): ・R ｉ =100 [Mbps] ・r ｉ =0 [Mbps] ・d ｉ = 10 [ms]

[0056] Link C1 (communication link between node station (B2) and base station 200): ・R ｉ =100 [Mbps] ・r ｉ =10 [Mbps] ・d ｉ = 10 [ms]

[0057] Link C2 (communication link between node station (B2) and node station (B3): ・R ｉ =100 [Mbps] ・r ｉ =10 [Mbps] ・d ｉ = 5 [ms]

[0058] Link C3 (communication link between node station (B3) and base station 200): ・R ｉ =100 [Mbps] ・r ｉ =10 [Mbps] ・d ｉ = 10 [ms]

[0059] In this case, using equations (2) and (3) mentioned above, the respective cost values ​​C from link A to link C3 are ｉ It will be as follows:

[0060] Link A:C ｉ = 100 / 100 × (1-0) + 1 / 1 = 2 • Link A1:C ｉ = 100 / 100 × (1 - 90 / 100) + 1 / 1 = 11 • Link A2:C ｉ = 100 / 100 × (1 - 10 / 100) + 2 / 1 = 3.1 • Link A3:C ｉ = 100 / 100 × (1 - 5 / 100) + 1 / 1 = 2.1 • Link B: C ｉ = 100 / 100 × (1-0) + 1 / 1 = 2 • Link B1:C ｉ= 100 / 100 × (1 - 80 / 100) + 1 / 1 = 6 • Link C: C ｉ = 100 / 100 × (1 - 0) + 10 / 1 = 11 • Link C1: C ｉ = 100 / 100 × (1 - 10 / 100) + 10 / 1 = 11.1 • Link C2: C ｉ = 100 / 100 × (1 - 5 / 100) + 5 / 1 = 6.1 • Link C3: C ｉ = 100 / 100 × (1 - 10 / 100) + 10 / 1 = 11.1

[0061] Therefore, according to equation (1) above, the respective cost values ​​C from √ A1 to √ C2 are as follows:

[0062] ・√A1: C = C ｉ (Link A) + C ｉ (Link A1) = 2 + 11 = 13 • Root A2: C = C ｉ (Link A) + C ｉ (Link A2) + C ｉ (Link A3) = 2 + 3.1 + 2.1 = 7.2 • Root B1: C = C ｉ (Link B) + C ｉ (Link B1) = 2 + 6 = 8 • Root C1: C = C ｉ (Link C) + C ｉ (Link C1) = 11 + 11.1 = 22.1 • Root C2: C = C ｉ (Link C) + C ｉ (Link C2) + C ｉ (Link C3) = 11 + 6.1 + 11.1 = 28.2

[0063] Comparing the cost values ​​C of each route from A1 to C2 calculated in this way, the cost value C of route A2 is the smallest at 7.2. Therefore, in this example, the connection node station determination unit 524 determines node station (A2), which is a candidate connection node station that terminal station (C) needs to connect to in order for terminal station (C) to communicate with base station 200 on route A2, as the connection node station.

[0064] Next, with reference to Figure 8, a specific example of determining the node station 400 to which a terminal station 100 connects in a conventional wireless communication system will be described as a comparative example of the wireless communication system according to this embodiment. In this conventional example, the node station 400 to which a terminal station 100 connects is determined by the received C / N at the terminal station 100. Specifically, for example, suppose the received C / N at terminal station (C) in link A (communication link between terminal station (C) and node station (A2)) is 8 [dB], the received C / N at terminal station (C) in link B (communication link between terminal station (C) and node station (A1)) is 10 [dB], and the received C / N at terminal station (C) in link C (communication link between terminal station (C) and node station (B2)) is 0 [dB]. In this case, the node station (A1) with the highest received C / N is selected as the connection destination for terminal station (C). In such conventional systems, the traffic conditions along the communication route from the node station (A1) to the base station 200 are not taken into consideration. Therefore, depending on the traffic conditions, the amount of traffic exceeding the transmission capacity of the communication link may flow in, potentially causing congestion.

[0065] In contrast, according to the wireless communication system described above, when determining which node station 400 the terminal station 100 will connect to, control is performed based on a cost value calculated considering the traffic status (congestion status) of each communication link constituting the communication network, thereby enabling the determination of which node station 400 the terminal station 100 will connect to in a way that suppresses congestion.

[0066] In the wireless communication system according to this disclosure, the connection node station determination unit 524 may select not just one but two or more communication routes as the communication route with the minimum cost value. For example, when selecting two routes under the conditions shown in Figure 7, in addition to route A2, which has the minimum cost value C, route B1, which has the second smallest cost value C, is also selected. Then, since it is necessary to connect to node station (A1) in order to communicate using route B1, the terminal station 100 connects communication links to both node station (A1) and node station (A2).

[0067] In this case, it is possible that the node station 400 that the terminal station 100 needs to connect to in order to communicate using the communication route with the second smallest cost value C is the same node station 400 that the terminal station 100 needs to connect to in order to communicate using the communication route with the largest cost value C. In such a case, the communication route with the third smallest cost value C may be selected, and the node station 400 that needs to be connected to in order to communicate using that communication route may be identified. Alternatively, if the node station 400 that needs to be connected to in order to communicate using the communication route with the third smallest cost value C is the same node station 400 that needs to be connected to in order to communicate using the communication route with the largest cost value C, then the fourth, fifth, and so on communication routes may be identified in order of increasing cost value C, and this process may be repeated until the destination node station 400 is determined.

[0068] In the wireless communication system according to this disclosure, as shown in Figure 9, the connection destination control device 520 may determine the connection destination of the node station 400, as well as the connection destination of the terminal station 100. In this case, the candidate node station identification unit 521 identifies candidate node stations from among the multiple node stations 400 of the non-terrestrial communication network 300 that are candidates for the node station 400 to which the node station 400 will connect. The communication route identification unit 522 identifies a communication route to which the node station 400 can transmit and receive traffic with the base station 200 via one of the candidate node stations. The cost calculation unit 523 calculates the cost value of each identified communication route. The connection node station determination unit 524 then determines the candidate node station to which the node station 400 needs to connect in order to communicate with the base station 200 via the communication route with the minimum cost value as the connection node station.

[0069] This disclosure can be used in wireless communication systems, wireless communication devices, wireless communication methods, and wireless communication programs in which terminal stations and base stations communicate via a non-terrestrial communication network.

[0070] 100 Terminal Station 200 Base Station 300 Non-terrestrial Communication Network 400 Node Station 401 Aggregation Node Station 401 410 Node Station Onboard Communication Equipment 411 Node Station Inter-station Communication Unit 412 Base Station Inter-station Communication Unit 413 Terminal Station Inter-station Communication Unit 414 Node Station Management Unit 415 Aggregation Node Station Inter-station Communication Unit 500 Network Controller 510 Network Management Device 520 Connection Destination Control Device 521 Connection Candidate Node Station Identification Unit 522 Communication Route Identification Unit 523 Cost Calculation Unit 524 Connection Node Station Determination Unit 600 Terrestrial Relay Station

Claims

1. A wireless communication system in which a terminal station and a base station communicate via a non-terrestrial communication network, comprising: a connection candidate node station identification unit that identifies candidate node stations that the terminal station will connect to from among a plurality of node stations of the non-terrestrial communication network; a communication route identification unit that identifies a communication route to which traffic can be transmitted and received with the base station via any of the connection candidate node stations; a cost calculation unit that calculates the cost value of each of the communication routes; and a connection node station determination unit that determines the connection candidate node station to be the connection node station that the terminal station needs to connect to in order to communicate with the base station via the communication route that minimizes the cost value, wherein the terminal station connects to the connection node station, and the cost calculation unit calculates the cost value of the communication route using at least the traffic transmission capacity of each communication link between each of the node stations in the communication route and the traffic flow rate of each communication link.

2. A wireless communication device for a wireless communication system in which a terminal station and a base station communicate via a non-terrestrial communication network, comprising: a connection candidate node station identification unit that identifies candidate connection candidate node stations from among a plurality of node stations of the non-terrestrial communication network to which the terminal station will connect; a communication route identification unit that identifies a communication route to which traffic can be transmitted and received with the base station via any of the connection candidate node stations; a cost calculation unit that calculates the cost value of each of the communication routes; and a connection node station determination unit that determines the connection candidate node station to be the connection node station to which the terminal station needs to connect in order to communicate with the base station via the communication route that minimizes the cost value, wherein the terminal station is connected to the connection node station, and the cost calculation unit calculates the cost value of the communication route using at least the traffic transmission capacity of each communication link between each of the node stations in the communication route and the traffic flow rate of each communication link.

3. A wireless communication method for a terminal station and a base station to communicate via a non-terrestrial communication network, comprising: a connection candidate node station identification step for identifying a candidate node station that is a candidate for the node station to which the terminal station will connect from among a plurality of node stations of the non-terrestrial communication network; a communication route identification step for identifying a communication route to which traffic can be transmitted and received with the base station via any of the connection candidate node stations; a cost calculation step for calculating the cost value of each of the communication routes; and a connection node station determination step for determining the connection candidate node station that the terminal station needs to connect to in order to communicate with the base station via the communication route with the minimum cost value, wherein the cost calculation step calculates the cost value of the communication route using at least the traffic transmission capacity of each communication link between each of the node stations in the communication route and the traffic flow rate of each communication link.

4. A wireless communication program for causing a computer in a wireless communication device of a wireless communication system in which the terminal station and the base station communicate via the non-terrestrial communication network to execute the wireless communication method described in claim 3.

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