Wireless communication system, wireless communication method, network controller, and program

Abstract

In a wireless communication system according to the present disclosure, communication between a terminal station and a core network is performed via a wireless network including a plurality of sky node stations and a plurality of ground base stations. A network controller establishes a communication path by linking at least one sky node station among the plurality of sky node stations and one ground base station among the plurality of ground base stations. When a review condition pertaining to the communication path is satisfied, the network controller determines the availability of each of a plurality of communication links constituting the wireless network and re-allocates electric power of a communication link having a low likelihood of use to a communication link having a high likelihood of use. The network controller re-establishes the communication path on the basis of the electric power state of each communication link after the reallocation.

Description

Wireless communication system, wireless communication method, network controller, and program

[0001] The present disclosure relates to a wireless communication system and a wireless communication method that utilize a non-terrestrial network, as well as a network controller and a program suitable for the wireless communication system.

[0002] In recent years, mobile communication systems have evolved, enabling mobile services to be enjoyed over most of the earth. Ultra-coverage is one of the requirements for the 5th generation (Beyond 5G) or 6th generation mobile communication systems, which are expected to be commercialized in the future. Ultra-coverage refers to expanding the service area to locations where the cost of installing existing base stations is high or difficult, such as mountains, oceans, and the air. Furthermore, there is a need to strengthen the nation's resilience against natural disasters, and the emergence of communication systems that are resistant to terrestrial disasters is desirable.

[0003] As a means for realizing the above-mentioned requirements, non-terrestrial networks (NTNs) have attracted attention. Non-terrestrial networks are wireless networks that use node stations deployed in the air or space, such as satellites, unmanned aerial vehicles (UAVs), high altitude pseudo satellites (HAPSs), and drones. In non-terrestrial networks, the node stations form a network by connecting with each other through communication links, and are further connected to terrestrial mobile networks via terrestrial base stations.

[0004] In non-terrestrial networks, node stations are equipped with mobile base station functions. Traffic packets generated by terminal stations are forwarded within the non-terrestrial network to node stations that can communicate with terrestrial base stations using routing functions, and then sent to the core network via the terrestrial base station. Packets sent from the core network to terminal stations are also processed in the same way using the routing functions of the non-terrestrial network.

[0005] Non-Patent Document 1 discloses a conventional technique for selecting a communication route when routing in a non-terrestrial network. In the conventional technique, a communication route is selected that minimizes the cost value C calculated by the following formula (1). However, in formula (1), Cｉ is the cost value of communication link i, n is the total number of links included in the communication path, and R ｉ is the link capacity of communication link i, and B ｒ is the reference value of the link capacity, and d ｉ is the delay time of communication link i, and B ｄ is the reference value of the delay time.

[0006] In communications using non-terrestrial networks, for example, communication may become impossible due to the effects of attenuation caused by rainfall. In such cases, according to conventional techniques, a new communication path is selected using equation (1) based on the capacity and delay time of each communication link at that time.

[0007] Tada, Nishiyama, Yoshimura, and Kato, "A Study on Efficient Routing Control in Hierarchical Satellite Networks," IEICE Technical Report SAT2010-9

[0008] However, node stations such as satellites and HAPS that make up non-terrestrial networks are supplied with power by solar power generation. Therefore, in communications using non-terrestrial networks, it is necessary to effectively utilize limited power resources. However, the above-mentioned conventional technologies do not take into consideration the effective utilization of power resources when selecting a communication path.

[0009] The present disclosure has been made in view of the above-mentioned problems, and aims to provide a technology that enables selection of a communication path that makes effective use of power resources of a non-terrestrial network.

[0010] The present disclosure provides a wireless communication system for achieving the above-mentioned object. The wireless communication system according to one embodiment of the present disclosure is a system for performing communication between a terminal station and a core network via a wireless network including a plurality of aerial node stations and a plurality of terrestrial base stations. The wireless communication system includes a network controller. The network controller is configured to establish a communication path by linking at least one of the plurality of aerial node stations with one of the plurality of terrestrial base stations. More specifically, when a communication path review condition is met, the network controller is configured to: determine a utilization probability for each of a plurality of communication links constituting the wireless network; reallocate the power of a communication link with a low utilization probability to a communication link with a high utilization probability; and reestablish the communication path based on the power state of each communication link after the reallocation.

[0011] The present disclosure also provides a wireless communication method for achieving the above-mentioned object. According to one embodiment of the present disclosure, the wireless communication method is a method for performing communication between a terminal station and a core network via a wireless network including a plurality of aerial node stations and a plurality of terrestrial base stations. The wireless communication method includes: establishing a communication path by linking at least one of the plurality of aerial node stations with one of the plurality of terrestrial base stations; determining a utilization probability for each of a plurality of communication links constituting the wireless network when a communication path review condition is met; reallocating the power of a communication link with a low utilization probability to a communication link with a high utilization probability; and reestablishing the communication path based on the power state of each communication link after the reallocation.

[0012] The present disclosure also provides a network controller for achieving the above object. According to one embodiment of the present disclosure, the network controller is provided in a wireless communication system that performs communication between a terminal station and a core network via a wireless network including a plurality of aerial node stations and a plurality of terrestrial base stations. The network controller includes a processing circuit. The processing circuit is configured to: establish a communication path by linking at least one of the plurality of aerial node stations with one of the plurality of terrestrial base stations; determine a utilization probability for each of a plurality of communication links constituting the wireless network when a communication path review condition is met; reallocate the power of a communication link with a low utilization probability to a communication link with a high utilization probability; and re-establish the communication path based on the power state of each communication link after the reallocation.

[0013] Furthermore, the present disclosure provides a program for achieving the above object. The program according to one embodiment of the present disclosure is a program including instructions for causing a processor to execute the processing performed by the network controller. The program may be recorded on a computer-readable recording medium or provided via a network.

[0014] According to the technology disclosed herein, when a communication path review condition is met, the availability of each of the communication links constituting the wireless network is determined. Then, the power of a communication link with a low availability probability is reallocated to a communication link with a high availability probability, and the communication path is re-established based on the power status of each communication link after the reallocation. This enables the selection of a communication path that makes effective use of the power resources of the non-terrestrial network.

[0015] FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating conventional communication control using a non-terrestrial network. FIG. 3 is a diagram illustrating a first example of communication control by a wireless communication system according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating a second example of communication control by a wireless communication system according to an embodiment of the present disclosure. FIG. 5 is a diagram illustrating a third example of communication control by a wireless communication system according to an embodiment of the present disclosure. FIG. 6 is a diagram illustrating a configuration of a node station-equipped communication device according to an embodiment of the present disclosure. FIG. 7 is a diagram illustrating a configuration of a network controller according to an embodiment of the present disclosure. FIG. 8 is a flowchart illustrating a first example of operation of a network controller according to an embodiment of the present disclosure. FIG. 9 is a flowchart illustrating a second example of operation of a network controller according to an embodiment of the present disclosure. FIG. 10 is a flowchart illustrating a third example of operation of a network controller according to an embodiment of the present disclosure.

[0016] Hereinafter, a wireless communication system according to an embodiment of the present disclosure will be described with reference to the drawings.

[0017] 1. Configuration of Wireless Communication System First, an example of the configuration of a wireless communication system according to an embodiment of the present disclosure will be described with reference to Fig. 1. As shown in Fig. 1, the wireless communication system 2 includes a non-terrestrial network (NTN) 15 formed from a plurality of airborne node stations (hereinafter simply referred to as node stations) deployed in the sky. The non-terrestrial network 15 includes three types of networks 15A, 15B, 15C, and 15D at different altitudes. These three types of networks 15A, 15B, and 15C are connected by communication links.

[0018] The first network is a low altitude network 15A formed by connecting a first group of node stations 5A deployed at relatively low altitudes via communication links. Hereinafter, the node stations 5A of the first group that make up the low altitude network 15A will be referred to as low altitude node stations. The second network is a medium altitude network 15B formed by connecting a second group of node stations 5B deployed at relatively medium altitudes via communication links. Hereinafter, the node stations 5B of the second group that make up the medium altitude network 15B will be referred to as medium altitude node stations. The third network is a high altitude network 15C formed by connecting a third group of node stations 5C deployed at relatively high altitudes via communication links. Hereinafter, the node stations 5C of the third group that make up the high altitude network 15C will be referred to as high altitude node stations.

[0019] Node stations can be geostationary orbit (GEO) satellites, medium orbit (MEO) satellites, low orbit (LEO) satellites, high altitude pseudo satellites (HAPS), as well as drones, unmanned aerial vehicles (UAVs), and aircraft. Typically, GEO satellites are used as high-altitude node stations 5C, and MEO satellites and LEO satellites are used as medium-altitude node stations 5B. HAPS, drones, UAVs, and aircraft are used as low-altitude node stations 5A. However, whether a node station is a high-altitude node station 5C, a medium-altitude node station 5B, or a low-altitude node station 5A depends on the relative altitude differences between the node stations that make up the non-terrestrial network 15. Therefore, if the node stations that make up the non-terrestrial network 15 are GEO satellites, MEO satellites, and LEO satellites, the LEO will be the low-altitude node station 5A. Also, if the node stations that make up the non-terrestrial network 15 are MEO satellites, LEO satellites, and HAPS, the MEO satellites become the high altitude node stations 5C.

[0020] The types of networks included in the non-terrestrial network 15 are not necessarily limited to the three types of low altitude, medium altitude, and high altitude. The non-terrestrial network 15 may be composed of two types of networks: low altitude and high altitude. For example, the non-terrestrial network 15 may be composed of a GEO network using GEO satellites as high altitude node stations and a HAPS network using HAPS as low altitude node stations. Furthermore, the non-terrestrial network 15 may include only one type of network.

[0021] In the non-terrestrial network 15 shown in FIG. 1 , the low altitude network 15A is linked to the terrestrial base station 3 and connected to the core network 14, which is a terrestrial network, via the terrestrial base station 3. Similarly, the medium altitude network 15B and the high altitude network 15C are linked to the terrestrial base station 3 and connected to the core network 14 via the terrestrial base station 3. A communication link is also established between a node station 5A belonging to the low altitude network 15A and a node station 5B belonging to the medium altitude network 15B. A communication link is also established between a node station 5B belonging to the medium altitude network 15B and a node station 5C belonging to the high altitude network 15C. Furthermore, a communication link can also be established between a node station 5A belonging to the low altitude network 15A and a node station 5C belonging to the high altitude network 15C. The communication link between the node stations may be realized by radio wave wireless communication or other wireless communication such as optical communication. Each communication link includes a communication line and a control line.

[0022] Each node station constituting the non-terrestrial network 15 has a routing function. Each node station transmits packets to a destination by transferring packets between other node stations. Each node station also has a mobile base station function. A terminal station 4 connects to one of the node stations and connects to the core network 14 via the non-terrestrial network 15. The terminal station 4 can connect to the Internet via the core network 14.

[0023] The wireless communication system 2 includes a network controller 10. The network controller 10 is placed in the air and connected to a non-terrestrial network 15. The network controller 10 is a device that establishes a communication path by linking at least one of the multiple node stations 5A, 5B, and 5C that form the non-terrestrial network 15 with one of the multiple terrestrial base stations 3. However, the network controller 10 may also be placed on the ground and connected to a core network 14. In this specification, a network including the non-terrestrial network 15 and the terrestrial base station 3 is collectively referred to as a wireless network. Details of the functions of the network controller 10 will be explained later.

[0024] 2. Communication Control Using a Wireless Communication System First, conventional communication control using a non-terrestrial network will be described with reference to Figure 2. In the example shown in Figure 2, the non-terrestrial network includes node stations 5-1, 5-2, 5-3, and 5-4. The node stations 5-1, 5-2, 5-3, and 5-4 are node stations located at relatively low altitudes, such as HAPS and LEO satellites. In the example shown in Figure 2, the node station 5-1 is connected to the node station 5-2 by a communication link L2. The node station 5-1 is also connected to the node station 5-3 by a communication link L4. On the other hand, the node station 5-4 is not connected to the other node stations 5-1, 5-2, and 5-3 by a communication link.

[0025] The non-terrestrial network is connected to the core network 14 via terrestrial base stations 3-1, 3-2, 3-3, and 3-4. The node station 5-1 is connected to the terrestrial base station 3-1 by a communication link L1, the node station 5-2 is connected to the terrestrial base station 3-2 by a communication link L3, the node station 5-3 is connected to the terrestrial base station 3-3 by a communication link L5, and the node station 5-4 is connected to the terrestrial base station 3-4 by a communication link L11.

[0026] As the communication path for communication between the terminal stations 4-1 and 4-2 and the core network 14, for example, the communication path with the smallest cost value calculated by the above-mentioned formula (1) is selected. In the example shown in FIG. 2, for the terminal station 4-1, the communication path R1 from the terminal station 4-1 to the terrestrial base station 3-1 via the node station 5-1 is selected as the smallest cost path. The communication path R1 includes a communication link L0 connecting the terminal station 4-1 and the node station 5-1, and a communication link L1 connecting the node station 5-1 and the terrestrial base station 3-1. The terminal station 4-2 is connected to the node station 5-4 by a communication link L10.

[0027] Now, suppose that rainfall causes signal attenuation in the communication link L1 connecting the node station 5-1 and the terrestrial base station 3-1, making communication using the communication link L1 impossible. In this case, a new communication path is selected by recalculating the cost value using the above-mentioned equation (1). In the example shown in Figure 2, communication path R2 from the terminal station 4-1 to the terrestrial base station 3-2 via the node station 5-1 and the node station 5-2 is selected as the new minimum-cost path.

[0028] However, in conventional communication control, power is allocated even to communication link L1 that is unavailable for communication, and the cost value is recalculated based on the link capacity and delay time in that state. Communication link L1 is a communication link that cannot be used as a communication path, and the power allocated to communication link L1 becomes unused surplus power. Therefore, allocating power to such a communication link is a waste of power resources. In non-terrestrial networks with limited available power, it is desirable to effectively utilize power resources by not allocating power to communication links that are unlikely to be used as communication paths or that are unlikely to be used, but to communication links that are likely to be used.

[0029] In contrast to conventional communication control having such problems, the wireless communication system 2 performs communication control as will be explained using Figures 3 to 5. In order to clarify the difference between the communication control by the wireless communication system 2 and conventional communication control, the configuration of the wireless network used in the explanation is assumed to be the same as the configuration shown in Figure 2.

[0030] As shown in Fig. 3, the wireless communication system 2 includes a network controller 10 arranged in a non-terrestrial network. The network controller 10 is mounted on a node station 5-5. The node station 5-5 may be arranged in a network at the same altitude as the node stations 5-1, 5-2, 5-3, and 5-4, or may be arranged in a high-altitude network. However, the network controller 10 may also be arranged on the ground.

[0031] The network controller 10 monitors the status of each communication link that constitutes the communication path and detects communication links that have become unavailable due to the effects of rainfall or the like. The communication links whose status is monitored by the network controller 10 include the communication link L1 that connects the node station 5-1 and the terrestrial base station 3-1. This communication link L1, together with the communication link L0 that connects the terminal station 4-1 and the node station 5-1, forms a communication path that connects the terminal station 4-1 and the core network 14.

[0032] The communication link L1 becoming unavailable is one of the conditions for the network controller 10 to review the communication path. When the communication path review condition is met, the network controller 10 determines the availability of each communication link established in the non-terrestrial network. Since communication link L1 is unavailable, it cannot be used. On the other hand, the availability of communication link L1 increases the availability of existing communication link L2 connecting node station 5-1 and node station 5-2 and existing communication link L4 connecting node station 5-1 and node station 5-3. This is because it is necessary to establish a new communication path to replace the communication path that used communication link L1. Here, if the cost value of the communication path that uses communication link L2 is lower than the cost value of the communication path that uses communication link L4, it can be determined that communication link L2 has a higher availability probability than communication link L4. In this case, the network controller 10 reallocates power by allocating the power that was allocated to communication link L1 to communication link L2.

[0033] By reallocating power in this manner, the carrier-to-noise ratio (CNR) of the communication link L2 can be improved, and the link capacity of the communication link L2 can be increased to support a higher modulation and coding scheme (MCS). After reallocating power, the network controller 10 calculates the cost value of each communication path using the above-mentioned equation (1) and selects the minimum-cost path as the new communication path. By re-establishing a communication path after reallocating power in this manner, it becomes possible to select a communication path that makes effective use of the power resources of a non-terrestrial network, which are by no means abundant. Note that the number of communication links that are the subject of power reallocation is not limited to one. For example, the power allocated to communication link L1 may be allocated to both communication link L2 and communication link L4. In this case, the amount of power reallocated may be allocated equally or pro rata according to the expected level of usage.

[0034] Furthermore, although there is no existing communication link between node station 5-1 and node station 5-4, it is possible to establish a new communication link if certain conditions regarding link capacity and delay time are met. In this case, it is possible to consider a potential communication link to exist between node station 5-1 and node station 5-4, and a new communication link L7 can be established by allocating the power that was allocated to communication link L1. For example, if the cost value of the communication path from terminal station 4-1 to terrestrial base station 3-4 via node station 5-1 and node station 5-4 is lower than the cost values ​​of other communication paths, it can be determined that communication link L7 is a communication link with a high probability of utilization. In this case, the network controller 10 may reallocate power so that the power allocated to communication link L1 is used to establish new communication link L7.

[0035] The probability of availability of a communication link decreasing is not necessarily limited to one at a time. For example, when the rainfall area is wide as shown in Figure 4, not only the communication link L1 between the node station 5-1 and the terrestrial base station 3-1 but also the communication link L3 between the node station 5-2 and the terrestrial base station 3-2 becomes uncommunicable. In this case, not only are the communication links L1 and L3 uncommunicable, but the probability of availability of the communication link L2 connecting the node station 5-1 and the node station 5-2 is also low. This is because even if traffic is transmitted from the node station 5-1 to the node station 5-2, the node station 5-2 cannot communicate with the terrestrial base station 3-3, and therefore the traffic cannot be transmitted to the core network 14.

[0036] When a communication link becomes unavailable, the network controller 10 determines whether there are any communication links that are no longer expected to be available or that have a low availability probability, based on the link connection relationships between the wireless networks. The communication link L2 shown in FIG. 4 is a communication link that is no longer expected to be available because the communication links L1 and L3 have become unavailable. Just as continuing to allocate power to the unavailable communication links L1 and L3 is a waste of power resources, continuing to allocate power to the communication link L2 with a low availability probability is also a waste of power resources. Therefore, the network controller 10 reallocates the power allocated to the communication links L1 and L3, as well as the power allocated to the communication link L2, to other communication links with a high availability probability. In the example shown in FIG. 4, the communication link L4 is determined to be a communication link with a high availability probability, and power is reallocated to the communication link L4. By reestablishing a communication path after reallocating power in this manner, it is possible to select a communication path that effectively utilizes the power resources of the non-terrestrial network, which are by no means abundant.

[0037] The network controller 10 may review a communication path not only when a communication link becomes unavailable or when the availability of the link decreases. A decrease in the available power at a node station is also one of the conditions for reviewing a communication path. Because node stations, such as satellites and HAPS, that constitute non-terrestrial networks generate power using solar power, available power decreases at night compared to during the day. To effectively utilize the reduced power at night, it is desirable to allocate power preferentially to communication links with high communication demand. Therefore, the network controller 10 reduces the power allocated to communication links with low availability and increases the power allocated to communication links with high availability. In the example shown in FIG. 5 , the power allocated to communication links L2 and L4 is reduced, and the reduced power is allocated to communication links L1, L3, and L5. By reestablishing a communication path after performing such power reallocation, it becomes possible to select a communication path that effectively utilizes scarce power resources at night.

[0038] 3. Configuration of Node Station Next, we will explain the configuration of the node station for realizing the above-mentioned communication control by the wireless communication system 2. Each node station, including the node stations 5-1, 5-2, 5-3, and 5-4, is equipped with a node station-mounted communication device 50 having the configuration shown in FIG.

[0039] The node station-mounted communication device 50 comprises an inter-node station communication device 51, an inter-terminal station communication device 52, and an inter-terrestrial base station communication device 53. The inter-node station communication device 51 connects a communication link to communicate with nearby node stations. The inter-terminal station communication device 52 connects a communication link to communicate with terminal stations. The inter-terrestrial base station communication device 53 connects a communication link to communicate with terrestrial base stations.

[0040] The node station-mounted communication device 50 further includes a management device 54, a route control device 55, and a power control device 56. The management device 54 aggregates information from the inter-node station communication device 51, the inter-terminal station communication device 52, and the inter-terrestrial base station communication device 53, and notifies the network controller 10 of the aggregated information. The management device 54 also notifies the route control device 55 and the power control device 56 of information notified from the network controller 10. The route control device 55 controls the inter-node station communication device 51, the inter-terminal station communication device 52, and the inter-terrestrial base station communication device 53 in accordance with the information notified from the network controller 10, and controls link connections for establishing communication paths. The power control device 56 controls the inter-node station communication device 51, the inter-terminal station communication device 52, and the inter-terrestrial base station communication device 53 in accordance with the information notified from the network controller 10, and controls the amount of power of the communication link with the corresponding node station (or terminal station, or terrestrial base station).

[0041] Each of the above-mentioned devices 51, 52, 53, 54, 55, and 56 included in the node station-equipped communication device 50 can be configured by a processing circuit including a general-purpose processor, an application-specific processor, an integrated circuit, an ASIC, an FPGA, a CPU, a conventional circuit, and / or a combination thereof. When the processing circuit includes a memory in which instructions and data are stored and a processor, the functions of each of the above-mentioned devices 51, 52, 53, 54, 55, and 56 can be realized by having the processor execute the instructions. The program can also be recorded on a recording medium or provided via a network.

[0042] 4. Configuration of the Network Controller Next, the configuration of the network controller 10 for realizing the above-described communication control by the wireless communication system 2 will be described with reference to FIG.

[0043] The network controller 10 includes a management device 101, a route control device 102, and a power control device 103. The management device 101 aggregates information notified from each node station and notifies the aggregated information to the route control device 102 and the power control device 103. The information notified from each node station includes information on the status of the communication link, such as the received CNR and delay time. The information on the status of the communication link also includes a notification that the communication link is not available for communication.

[0044] The power control device 103 determines the power to be allocated to each communication link based on information about the communication link notified by each node station, and notifies the management device 101 of the determined power. When a communication path review condition is met, the power is reallocated and the reallocated power is notified to the management device 101. The path control device 102 determines a communication path based on information about the communication link notified by each node station. When the power control device 103 reallocates power to each communication link, the path control device 102 calculates cost values ​​for determining the communication path based on the reallocated power. Note that the path control device 102 may use either static routing or dynamic routing to determine the communication path. The management device 101 notifies each node station of the power to be allocated to each communication link and the communication path to be used.

[0045] Each of the above devices 101, 102, and 103 included in the network controller 10 can be configured by a processing circuit including a general-purpose processor, an application-specific processor, an integrated circuit, an ASIC, an FPGA, a CPU, a conventional circuit, and / or a combination thereof. When the processing circuit includes a memory in which instructions and data are stored and a processor, the functions of each of the above devices 101, 102, and 103 can be realized by having the processor execute the instructions. The program can be recorded on a recording medium or provided via a network.

[0046] 5. Operation of the Network Controller The flowcharts shown in Figures 8 to 10 briefly summarize the operation of the network controller 10 configured as described above. The operations shown in these flowcharts correspond to the wireless communication method according to the embodiment of the present disclosure, which is executed by the wireless communication system 2. In the following description, it is assumed that the wireless communication system 2 is configured as in the examples shown in Figures 3 to 5.

[0047] In step S11 in the flowchart of Fig. 8, the network controller 10 determines whether there is an unavailable communication link in the wireless network (a network including a non-terrestrial network and a terrestrial base station). The communication link L1 in Fig. 3 and the communication links L1 and L3 in Fig. 4 correspond to unavailable communication links. If there is no unavailable communication link, the network controller 10 does not reallocate power.

[0048] If there is an unavailable communication link, the operation of the network controller 10 proceeds to step S12. In step S12, the network controller 10 determines whether there is an unavailable communication link in the wireless network. The communication link L2 in FIG. 4 corresponds to the unavailable communication link.

[0049] If there is a communication link that is not expected to be used, the operation of the network controller 10 proceeds to step S13. In step S13, the network controller 10 reallocates the power that was allocated to the unavailable communication link and the power that was allocated to the communication link that is not expected to be used. The communication link that is the target of reallocation is a communication link that is relatively likely to be used. In the example shown in FIG. 4, communication link L4 corresponds to a communication link that is relatively likely to be used. After the power reallocation, the network controller 10 re-establishes a communication path based on the power status of each communication link.

[0050] If there is no communication link that is unlikely to be used, the operation of the network controller 10 proceeds to step S14. In step S14, the network controller 10 reallocates the power that was allocated to the unavailable communication link. The communication link to be reallocated is a communication link that is likely to be used relatively frequently. In the example shown in FIG. 3, communication links L2 and L7 correspond to communication links that are likely to be used frequently. After the power reallocation, the network controller 10 reestablishes a communication path based on the power status of each communication link.

[0051] In step S21 in the flowchart of Fig. 9, the network controller 10 determines whether it is currently nighttime. Whether it is currently nighttime or not may be determined based on whether the node stations constituting the non-terrestrial network are receiving sunlight sufficient for power generation. If it is not currently nighttime, the network controller 10 does not reallocate power.

[0052] If it is currently nighttime, the operation of the network controller 10 proceeds to step S22. In step S22, the network controller 10 reallocates the power that was allocated to communication links with low communication demand. The communication links to be reallocated are communication links with relatively high communication demand. In the example shown in FIG. 4, communication links L1, L3, and L5 correspond to communication links with high communication demand, and communication links L2 and L4 correspond to communication links with low communication demand. After the power reallocation, the network controller 10 reestablishes communication paths based on the power status of each communication link.

[0053] The flowchart in Figure 10 is a flowchart showing the operation of the network controller 10 when the magnitude of communication demand, regardless of whether it is day or night, is considered to be the magnitude of expected usage, and power is reallocated from a communication link with low communication demand to a communication link with high communication demand.

[0054] In step S31 in the flowchart of FIG. 10, the network controller 10 determines whether there is a communication link whose communication demand exceeds a predetermined upper limit. A communication link whose communication demand exceeds the upper limit means a communication link experiencing congestion or a communication link with extremely high communication volume. The magnitude of the communication demand may be measured by measuring the current communication volume and communication speed, or may be predicted in advance based on statistical information on these. If there is no communication link whose communication demand exceeds the upper limit, the network controller 10 does not reallocate power.

[0055] If there is a communication link whose communication demand is greater than the upper limit, the operation of the network controller 10 proceeds to step S32. In step S32, the network controller 10 determines whether there is a communication link whose communication demand is less than a predetermined lower limit. A communication link whose communication demand is less than the lower limit means a communication link where no communication is being performed or a communication link with extremely low communication volume. If there is no communication link whose communication demand is less than the lower limit, the network controller 10 does not reallocate power.

[0056] If there is a communication link whose communication demand is less than the lower limit, the operation of the network controller 10 proceeds to step S33. In step S33, the network controller 10 reallocates the power that was allocated to the communication link whose communication demand is less than the lower limit. The communication link to be reallocated is the communication link whose communication demand is greater than the upper limit. After the power reallocation, the network controller 10 re-establishes the communication path based on the power state of each communication link. In other words, in this flowchart, the condition for reviewing the communication path is that both a communication link whose communication demand is less than the upper limit and a communication link whose communication demand is less than the lower limit exist.

[0057] As described above, the network controller 10 operates to reallocate the power of communication links with low availability to communication links with high availability, and re-establish communication paths based on the power status of each communication link after reallocation. This enables the selection of communication paths that make effective use of the power resources of the non-terrestrial network.

[0058] 2 Wireless communication system 3, 3-1, 3-2, 3-3, 3-3 Terrestrial base station 4, 4-1, 4-2 Terminal station 5A Low altitude node station 5B Medium altitude node station 5C High altitude node station 5-1, 5-2, 5-3, 5-4, 5-5 Node station 10 Network controller 14 Core network 15 Non-terrestrial network 15A Low altitude network 15B Medium altitude network 15C High altitude network 50 Node station mounted communication device R1, R2 Communication path L0, L1, L2, L3, L4, L5, L7, L10, L11 Communication link

Claims

1. A wireless communication system in which communication between a terminal station and a core network is performed via a wireless network including a plurality of aerial node stations and a plurality of terrestrial base stations, the wireless communication system comprising: a network controller that establishes a communication path by linking at least one of the plurality of aerial node stations with one of the plurality of terrestrial base stations; and the network controller is configured to, when a condition for reviewing the communication path is met, determine the likelihood of utilization of each of a plurality of communication links constituting the wireless network; reallocate the power of the communication link with a low likelihood of utilization to the communication link with a high likelihood of utilization; and re-establish the communication path based on the power state of each communication link after the reallocation.

2. A wireless communication method for communicating between a terminal station and a core network via a wireless network including a plurality of aerial node stations and a plurality of terrestrial base stations, comprising: establishing a communication path by linking at least one of the plurality of aerial node stations with one of the plurality of terrestrial base stations; determining the availability of each of a plurality of communication links constituting the wireless network when a review condition for the communication path is met; reallocating the power of the communication link with a low availability probability to the communication link with a high availability probability; and re-establishing the communication path based on the power state of each communication link after the reallocation.

3. A network controller provided in a wireless communication system that performs communication between a terminal station and a core network via a wireless network including a plurality of aerial node stations and a plurality of terrestrial base stations, the network controller comprising a processing circuit configured to: establish a communication path by linking at least one of the plurality of aerial node stations with one of the plurality of terrestrial base stations; determine the likelihood of utilization of each of a plurality of communication links that constitute the wireless network when a review condition for the communication path is met; reallocate the power of the communication link with a low likelihood of utilization to the communication link with a high likelihood of utilization; and re-establish the communication path based on the power state of each communication link after the reallocation.

4. A program comprising instructions for causing a processor to execute the processing performed by the network controller according to claim 3.

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