Wireless communication system, communication path control device, communication path control method, and communication path control program

Abstract

The purpose of the present disclosure is to provide technology that makes it possible to dynamically set a communication path with respect to an airborne relay station that moves relatively to the ground and improve communication quality. A wireless communication system according to the present disclosure uses a plurality of airborne relay stations that move relatively to the ground, said wireless communication system comprising at least one ground station, the plurality of airborne relay stations, each of which switches a feeder link to a ground station designated in accordance with a schedule, and a communication path control device. The communication path control device detects a poor weather region on the basis of a received signal that reaches a ground station via a feeder link from a first airborne relay station, and, when a poor weather region is detected, determines on the basis of the schedule whether there is a second airborne relay station that will move so as to overlap with the poor weather region. When there is such a second airborne relay station, the communication path control device sets a communication path which comprises at least one link that can connect the second airborne relay station and one of the at least one ground station in a manner avoiding the poor weather region, and establishes the set communication path.

Description

Wireless communication system, communication path control device, communication path control method, and communication path control program

[0001] The present disclosure relates to a wireless communication system, a communication path control device, a communication path control method, and a communication path control program using a non-terrestrial network.

[0002] For future B5G / 6G services, ultra-coverage is required. In B5G / 6G services, the use of NTN (Non-Terrestrial Network) is expected to expand the coverage area. As a result, the service area can be expanded to locations where the laying cost of terrestrial stations is high or difficult, such as mountains, seas, or the air. In addition, it is also possible to construct a communication system that is resistant to terrestrial disasters.

[0003] In NTN, high-altitude pseudo-satellites (HAPS: High Altitude Platform Station) located at an altitude of about 20 km, LEO (Low Earth Orbit) satellites, MEO (Medium Earth Orbit) satellites, GEO (Geostationary Orbit) satellites, etc. in space are utilized as relay stations in the upper air.

[0004] In Non-Patent Document 1, an NTN using a plurality of LEO satellites as relay stations in the upper air is reported. Since LEO satellites are closer to terrestrial stations than GEO satellites, stable wireless communication with low latency and high throughput is possible (see Non-Patent Document 1).

[0005] However, relay stations in the upper air that move in non-geostationary orbits (NGSO: Non-Geostationary Orbit) such as LEO and MEO move relative to the ground, so handover is required each time.

[0006] Sami Ma, Yi-Ching Chou, Haoyuan Zhao, Long Chen, Xiaoqiang Ma, Jiangchuan Liu. "Network Characteristics of LEO Satellite Constellations: A Starlink-Based Measurement from End Users", IEEE INFOCOM 2023 - IEEE Conference on Computer Communications, pages 1-10, IEEE, 2023.

[0007] Aerial relay stations, which move relative to the ground, establish feeder links with designated ground stations at specified times according to a schedule. However, conventionally, even when it was known that the feeder link with the planned ground station could not meet the required quality, the aerial relay station had no choice but to establish the feeder link as scheduled.

[0008] This disclosure aims to provide a technology that can dynamically set communication paths for aerial relay stations that are moving relative to the ground, thereby improving communication quality, in order to solve the aforementioned problems.

[0009] A first aspect of the present disclosure is a wireless communication system using a plurality of aerial relay stations that move relative to the ground, comprising: one or more ground stations; the plurality of aerial relay stations, each switching a feeder link to a designated ground station according to a schedule; and a communication path control device that controls a communication path, wherein the communication path control device is preferably configured to perform: a process for detecting a weather deterioration area based on a received signal that reaches the ground station from the first aerial relay station via a feeder link; a process for determining, based on the schedule, whether there is a second aerial relay station that moves to overlap the weather deterioration area when a weather deterioration area is detected; a process for setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and a process for opening the set communication path.

[0010] A second embodiment is a communication path control device for controlling a communication path in a wireless communication system comprising one or more ground stations and a plurality of aerial relay stations that move relative to the ground and each switches a feeder link to a designated ground station according to a schedule, wherein the communication path control device is preferably configured to perform the following: a process for detecting a weather deterioration area based on a received signal that reaches the ground station from a first aerial relay station via a feeder link; a process for determining, based on the schedule, whether there is a second aerial relay station that moves so as to overlap the weather deterioration area when a weather deterioration area is detected; a process for setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and a process for opening the set up communication path.

[0011] A third embodiment is a communication path control method for controlling a communication path in a wireless communication system comprising one or more ground stations and a plurality of aerial relay stations that move relative to the ground and each switches a feeder link to a designated ground station according to a schedule, wherein the method preferably includes: detecting a weather deterioration area based on a received signal that reaches the ground station from a first aerial relay station via a feeder link; determining, based on the schedule, whether there is a second aerial relay station that moves to overlap the weather deterioration area when a weather deterioration area is detected; setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and opening up the set communication path.

[0012] A fourth embodiment is a communication path control program to be executed by a communication path control device that controls a communication path in a wireless communication system comprising one or more ground stations and a plurality of aerial relay stations that move relative to the ground and each switches a feeder link to a designated ground station according to a schedule, wherein the communication path control program preferably includes a program that causes the device to execute: a process for detecting a weather deterioration area based on a received signal that reaches the ground station from a first aerial relay station via a feeder link; a process for determining, based on the schedule, whether there is a second aerial relay station that moves so as to overlap the weather deterioration area when a weather deterioration area is detected; a process for setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and a process for opening the set up communication path.

[0013] This disclosure describes how, when an area of ​​deteriorating weather is detected, a new communication path is established for an aerial relay station that is attempting to move into the area of ​​deteriorating weather, allowing it to avoid the area of ​​deteriorating weather. This enables the dynamic setting of communication paths for aerial relay stations that are moving relative to the ground, thereby improving communication quality.

[0014] This figure shows the configuration of a wireless communication system according to Embodiment 1. This figure illustrates a method for controlling a communication path by a communication path control device according to Embodiment 1. This figure illustrates a method for controlling a communication path by a communication path control device according to Embodiment 1. This figure illustrates a method for controlling a communication path in a comparative example of the present disclosure. This figure illustrates a method for controlling a communication path in a comparative example of the present disclosure. This block diagram shows an example of the configuration of a communication path control device according to Embodiment 1, and this figure shows the hardware configuration of the communication path control device according to Embodiment 1. This is a flowchart illustrating the processing performed by the CPU of the communication path control device according to Embodiment 1. This figure illustrates a method for controlling a communication path by a communication path control device according to Embodiment 2. This is a modified example of Figure 10.

[0015] Embodiments of this disclosure will be described with reference to the drawings. The same or corresponding components will be denoted by the same reference numerals, and repetition of the description may be omitted.

[0016] Embodiment 1 Figure 1 is a diagram showing the configuration of a wireless communication system 200 according to Embodiment 1. The wireless communication system 200 comprises a plurality of aerial relay stations 110, a plurality of ground stations 120, and a communication path control device 100.

[0017] The aerial relay station 110 is a radio relay station that moves along a predetermined air route and moves relative to the ground. Nearby aerial relay stations 110 are connected by an aerial link 60 (not shown), and an aerial network is formed by radio or optical signal communication.

[0018] Each of the aerial relay stations 110 stores a schedule that specifies when and with which ground station 120 to establish a feeder link 50. The aerial relay station 110 establishes a feeder link 50 with the designated ground station 120 at the designated time according to the schedule.

[0019] The aerial relay station 110 receives data transmitted from a ground terminal station (not shown). The aerial relay station 110 transmits the data to the ground station 120 via the aerial network.

[0020] Examples of aerial relay stations 110 include satellite communication stations that move in non-geostationary orbit, such as MEO satellite communication stations and LEO satellite communication stations. Alternatively, aerial relay stations 110 may also be HAPS, drones, unmanned aerial vehicles, aircraft, etc., and are not limited to these. Multiple aerial relay stations 110 do not necessarily have to be of the same type; for example, they may include multiple types from the examples listed above.

[0021] The ground station 120 receives data transmitted from the aerial relay station 110 via the feeder link 50 and transmits the packet data contained in the radio waves to the ground network 130 (not shown). In other words, the ground station 120 is a ground base station, ground relay station, etc., that functions as a gateway station for the ground network 130.

[0022] A ground terminal station is a wireless terminal such as a smartphone that communicates wirelessly with the aerial relay station 110 via a service link. The ground terminal station transmits and receives data such as internet traffic to and from the aerial relay station 110.

[0023] The communication path control device 100 is connected to each of the ground stations 120 under its management by wire or wireless connection. The communication path control device 100 detects areas of deteriorating weather 10 that occur on the feeder link 50 by monitoring received signals that arrive at the ground stations 120 via the feeder link 50 from the aerial relay station 110. Areas of deteriorating weather 10 are areas where rainfall is occurring, areas where clouds are developing, or areas where there are signs of future bad weather.

[0024] If a weather deterioration area 10 is detected, the communication path control device 100 sets a new communication path that avoids the weather deterioration area 10 for the aerial relay station 110 that is attempting to move over the weather deterioration area 10.

[0025] Thus, in the wireless communication system 200 of this disclosure, the communication path control device 100 dynamically sets the communication path to the aerial relay station 110 according to the weather.

[0026] In the above description, we explained a method of transmitting data from a ground terminal station to a ground station 120 via relaying by an aerial relay station 110. However, it is also possible to transmit data from a ground station 120 to a ground terminal station via relaying by an aerial relay station 110.

[0027] <Method for controlling the communication path> In this embodiment, the communication path consists of a feeder link 50 connecting an aerial relay station 110 and one of several ground stations 120. The method for controlling the communication path will be specifically explained below using Figures 2 and 3.

[0028] Figures 2 and 3 illustrate the method of controlling the communication path by the communication path control device 100 according to Embodiment 1. Here, it is assumed that the first aerial relay station 110-1 and the second aerial relay station 110-2 each have a feeder link 50 connecting them to the first ground station 120-1. The second aerial relay station 110-2 is a radio station that follows the first aerial relay station 110-1, and if according to the schedule, it will fly after the first aerial relay station 110-1 to the same location as or near the first aerial relay station 110-1.

[0029] Hereafter, the feeder link 50 connecting the first aerial relay station 110-1 to the first ground station 120-1 will be referred to as the first link 51-1, and the feeder link 50 connecting the second aerial relay station 110-2 to the first ground station 120-1 will be referred to as the second link 52-1.

[0030] The first ground station 120-1 notifies the communication path control device 100 of the information of the received signal received via the first link 51-1 and the second link 52-1 as time-series data. The information of the received signal is not limited to, but may include, for example, communication quality, delay magnitude, and propagation path information such as phase information and amplitude information of the received signal. Furthermore, communication quality may be, for example, the strength of the received power such as RSSI and RSRQ, noise indicators such as RSRP and SINR, throughput, or other indicators.

[0031] The communication path control device 100 acquires information on received signals that have arrived via the first link 51-1 and the second link 52-1 from the first ground station 120-1. Furthermore, the communication path control device 100 detects weather deterioration areas 10 that have occurred on the feeder links 50 based on the information on received signals from each feeder link 50.

[0032] For example, if the information of the received signal is information about communication quality such as received power, the communication path control device 100 compares the acquired communication quality with a preset communication quality requirement to extract feeder links 50 in which deterioration of communication quality is occurring or is showing signs of deterioration in the future. Furthermore, the communication path control device 100 sets the propagation path of the extracted feeder links 50 and its surroundings as a weather deterioration area 10.

[0033] Alternatively, if the information in the received signal is propagation path information, the communication path control device 100 detects the weather deterioration area 10 by analyzing the propagation path information. Alternatively, if the information in the received signal is the magnitude of the delay, the communication path control device 100 detects the weather deterioration area 10 based on the magnitude of the delay. Note that the method for detecting the weather deterioration area 10 is not limited, and other methods may be used.

[0034] In Figure 2, rainfall occurs in the propagation path of the first link 51-1, causing rain attenuation in the wireless signal. In this case, the communication path control device 100 detects the weather deterioration region 10 that has occurred on the first link 51-1.

[0035] Furthermore, the communication path control device 100 determines, based on the schedule of each airborne relay station 110, whether there is an airborne relay station 110 that is about to move into the weather deterioration area 10. In the example shown in the figure, the subsequent second airborne relay station 110-2 is about to move into the weather deterioration area 10, and the second link 52-1 of the second airborne relay station 110-2 is about to enter the weather deterioration area 10. Therefore, the communication path control device 100 sets a new communication path for the second airborne relay station 110-2 that can avoid the weather deterioration area 10.

[0036] Specifically, the communication path control device 100 searches for any ground stations 120 other than the first ground station 120-1 that can establish a feeder link 50 for the second airborne relay station 110-2 before the weather deterioration area 10 overlaps with the second airborne relay station 110-2.

[0037] If a ground station 120 (referred to as the second ground station 120-2) capable of establishing a feeder link 50 is found, the communication path control device 100 determines whether the weather deterioration area 10 can be avoided by the feeder link 50 between the second aerial relay station 110-2 and the second ground station 120-2.

[0038] The method of determination is not particularly limited, but as an example, the communication path control device 100 determines whether a weather deterioration area 10 has occurred on the feeder link 50 established by the second ground station 120-2 based on the information of the received signal acquired from the second ground station 120-2. If a weather deterioration area 10 has not occurred, it can be said that there is no bad weather above the second ground station 120-2, and therefore the communication path control device 100 determines that the weather deterioration area 10 can be avoided by the feeder link 50 between the second upper-air relay station 110-2 and the second ground station 120-2.

[0039] If it is determined that it is possible to avoid the weather deterioration area 10, the communication path control device 100 transmits a command signal 20 to the second airborne relay station 110-2 to switch the feeder link 50 to the second ground station 120-2. At this time, the command signal 20 may also include information on the expected time when the second airborne relay station 110-2 and the weather deterioration area 10 will overlap. This allows the second airborne relay station 110-2 to complete the establishment of the feeder link 50 with the second ground station 120-2 by the scheduled time.

[0040] The command signal 20 from the communication path control device 100 is transmitted to the second aerial relay station 110-2 via the second link 52-1. However, the command signal 20 may be transmitted via other paths.

[0041] Upon receiving the command signal 20 from the communication path control device 100, the second aerial relay station 110-2 changes its schedule and switches the feeder link 50 to the second ground station 120-2. As a result, as shown in Figure 3, a third link 52-2 is established between the second aerial relay station 110-2 and the second ground station 120-2. Since the third link 52-2 does not overlap with the weather deterioration area 10, it is possible to prevent deterioration of communication quality due to bad weather.

[0042] In Figure 2, it was explained that the information in the received signal from the ground station 120 includes communication quality. However, the communication path control device 100 may calculate the communication quality of each feeder link 50 instead of the ground station 120.

[0043] Note that, as shown in FIG. 2, in the wireless communication system 200 of the present embodiment, two or more aerial relay stations 110 and two or more terrestrial stations 120 may be included.

[0044] <Comparative Example> FIGS. 4 and 5 are diagrams for explaining a method of controlling a communication path in a comparative example of the present disclosure. Similar to the case of FIG. 2, here, the second aerial relay station 110-2 is a subsequent radio station of the first aerial relay station 110-1, and if it is on schedule, it flies to a position identical to or around the first aerial relay station 110-1 after the first aerial relay station 110-1.

[0045] In the prior art, the switching of the feeder link 50 by each aerial relay station 110 was determined by a schedule. Therefore, even if rainfall occurred on the first link 51-1 established by the first aerial relay station 110-1 and the first terrestrial station 120-1 (FIG. 4), the subsequent second aerial relay station 110-2 continued to establish the second link 52-1 on schedule (FIG. 5). As a result, the second link 52-1 overlapped with the bad weather area 10, resulting in a problem that the communication quality deteriorated. In the prior art, deterioration of communication quality due to bad weather had to be tolerated, and it was a best-effort type of operation.

[0046] FIG. 6 is a block diagram showing a configuration example of the communication path control device 100 according to Embodiment 1. Here, a case where the communication path control device 100 calculates the communication quality of each feeder link 50 and detects the bad weather area 10 based on the communication quality will be described.

[0047] The communication quality analysis circuit 101 analyzes the information of the received signal notified from each terrestrial station 120 and calculates the communication quality of each feeder link 50. The determination circuit 102 detects the bad weather area 10 generated on the feeder link 50 based on the communication quality of each feeder link 50. When there is a feeder link 50 in which the bad weather area 10 has occurred, the determination circuit 102 notifies the communication path control circuit 103 of the identification information (position information, etc.) of the terrestrial station 120 and the aerial relay station 110 that open the feeder link 50.

[0048] The communication path control circuit 103 sets a communication path that can avoid the bad weather area 10 for the subsequent high-altitude relay station 110 by the above method. The communication path control circuit 103 transmits a command signal 20 to the subsequent high-altitude relay station 110 to open the feeder link 50 according to the newly set communication path.

[0049] The storage device 104 stores the route information (orbit information in the case of a satellite communication station) and schedule of each high-altitude relay station 110.

[0050] FIG. 7 is a diagram showing the hardware configuration of the communication path control device 100 according to Embodiment 1. The processing performed by the communication path control device 100 may be executed by a program using a computer including a CPU and a memory, with the communication path control program stored in the memory. Alternatively, it may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). Note that the communication path control program may be provided by being recorded on a storage medium or provided through a network.

[0051] The communication path control device 100 includes an input unit 40, an output unit 41, a communication unit 42, a CPU (Central Processing Unit, also referred to as a processor) 43, a memory 44, and an HDD (Hard Disk Drive) 45 connected via a bus 46, and has functions as a computer. Further, the communication path control device 100 is capable of inputting and outputting data to and from a computer-readable storage medium 47.

[0052] The input unit 40 is, for example, a keyboard and a mouse. The output unit 41 is, for example, a display device such as a display.

[0053] The communication unit 42 is, for example, a communication interface for communicating with the ground station 120.

[0054] The memory 44 corresponds to, for example, a volatile or non-volatile semiconductor memory such as a RAM, a ROM, or a flash memory, or a magnetic disk, a flexible disk, an optical disk, a DVD, or the like.

[0055] The CPU 43 controls each component of the communication path control device 100 and performs predetermined processing. The memory 44 and HDD 45 are storage devices 104 that store data such as information on received signals acquired from the ground station 120, communication path control programs, flight path information for each airborne relay station 110, and schedules.

[0056] The storage medium 47 is capable of storing communication path control programs and the like that cause the communication path control device 100 to execute its functions. The storage medium 47 is a USB (Universal Serial Bus) memory, a CD-ROM (Compact Disc Read Only Memory), etc.

[0057] Note that the architecture of the communication path control device 100 is not limited to the example shown in Figure 7.

[0058] Figure 8 is a flowchart illustrating the processing performed by the CPU 43 of the communication path control device 100 according to Embodiment 1. Here, we will explain the case in which the communication path control device 100 calculates the communication quality of each feeder link 50 and detects the weather deterioration area 10 based on the communication quality.

[0059] The CPU 43 reads the communication path control program stored in the memory 44 or HDD 45 and executes the following processes. First, it analyzes the information of the received signals notified from each of the managed ground stations 120 and calculates the communication quality of each feeder link 50 (step S01). Next, it determines whether or not there is a feeder link 50 where a weather deterioration area 10 is occurring, based on the communication quality of each feeder link 50 (step S02).

[0060] If no feeder link 50 experiencing a weather deterioration area 10 is detected (No), no new communication paths are set up for each aerial relay station 110, and the handover is performed as scheduled (step S03).

[0061] On the other hand, if a feeder link 50 where a weather deterioration area 10 is occurring is detected (Yes), it is determined, based on the schedule of each airborne relay station 110, whether there is an airborne relay station 110 that is moving to overlap with the weather deterioration area 10 (step S04). If there is no such airborne relay station 110 (No), the process proceeds to step S03.

[0062] On the other hand, if there is a suitable aerial relay station 110 (Yes), a communication path that avoids the weather deterioration area 10 is set for the suitable aerial relay station 110 (step S05). Furthermore, a command signal 20 is sent to the suitable aerial relay station 110 to open a feeder link 50 according to the newly set communication path (step S06).

[0063] As described above, in this embodiment, the ground station 120 detects the weather deterioration area 10 based on the received signal received from the aerial relay station 110 via the feeder link 50. When the weather deterioration area 10 is detected, the communication path control device 100 sets a new communication path that avoids the weather deterioration area 10 for the aerial relay station 110, which is attempting to move so as to overlap with the weather deterioration area 10. This provides a technology that can dynamically set a communication path for the aerial relay station 110 as it moves relative to the ground and improve communication quality.

[0064] This disclosure is particularly effective when applied to a wireless communication system 200 using a high-frequency band (millimeter wave) feeder link 50. From the viewpoint of expanding communication capacity, it was agreed at the recent World Radiocommunication Conference (WRC) to allocate high-frequency band electromagnetic waves to the feeder link 50. It is known that attenuation due to rainfall and developed clouds is unavoidable in the millimeter wave frequency band. In this embodiment, the feeder link 50 can be set to avoid the weather deterioration area 10 for the upper-air relay station 110, thereby improving the communication quality in the wireless communication system 200 using the high-frequency band feeder link 50.

[0065] Embodiment 2 This embodiment describes a case where the communication path includes one or more upper links 60 and feeder links 50. The following describes the changes from Embodiment 1.

[0066] Figures 9 and 10 illustrate the method of controlling the communication path by the communication path control device 100 according to Embodiment 2. Similar to Figure 2 of Embodiment 1, it is assumed that a weather deterioration area 10 occurs on the first link 51-1 between the first aerial relay station 110-1 and the first ground station 120-1. It is also assumed that the second link 52-1 between the second aerial relay station 110-2 and the first ground station 120-1 is expected to overlap with the weather deterioration area 10.

[0067] The communication path control device 100 of this embodiment searches for a communication path that can connect the second aerial relay station 110-2 to the ground station 120 while avoiding the weather deterioration area 10 by using the aerial link 60.

[0068] If a communication path that avoids the weather deterioration area 10 is found, the communication path control device 100 transmits a command signal 20 to the second airborne relay station 110-2 and the airborne relay station 110 included in the communication path (referred to as the third airborne relay station 110-3) to establish an airborne link 60 according to the communication path.

[0069] Figure 10 is a diagram illustrating the effects of Embodiment 2. Upon receiving a command signal 20 from the communication path control device 100, the second airborne relay station 110-2 establishes an airborne link 60 with the third airborne relay station 110-3 based on the communication path information. The third airborne relay station 110-3 is an airborne relay station 110 that follows the second airborne relay station 110-2, and has established the first ground station 120-1 and the fourth link 53-1 according to the schedule. Since the communication path using the airborne link 60 and the fourth link 53-1 does not overlap with the weather deterioration area 10, deterioration of communication quality due to bad weather can be prevented.

[0070] In this embodiment, the wireless communication system 200 may include two or more aerial relay stations 110 and one or more ground stations 120, as shown in Figures 9 and 10.

[0071] In this embodiment, the communication path control device 100 sets a new communication path including one or more aerial links 60 and feeder links 50 for an aerial relay station 110 that is moving to overlap with the weather deterioration area 10. Compared to the case where only the feeder links 50 are targeted as in Embodiment 1, the degree of freedom in selecting the communication path is higher, making it easier to find a communication path that is more suitable for avoiding the weather deterioration area 10 than in Embodiment 1.

[0072] <Modification of Embodiment 2> In Figure 10, the communication path that can avoid the weather deterioration area 10 is not limited to the communication path described in Figure 10. For example, as shown in Figure 11, a communication path using the air link 60 between the first air relay station 110-1 and the second air relay station 110-2, and the fifth link 51-2 between the first air relay station 110-1 and the second ground station 120-2 may also be used. Thus, the newly established communication path may involve a change in the ground station 120.

[0073] This disclosure is not limited to the embodiments described above, and various modifications can be made during implementation without departing from its essence. Furthermore, each embodiment and its modifications may be combined as appropriate, and in that case, the combined effects can be obtained.

[0074] <Explanation of terms used in the claims> The term "link" as used in the claims refers to both the feeder link 50 and the upper link 60.

[0075] 10: Weather deterioration area, 20: Command signal, 40: Input unit, 41: Output unit, 42: Communication unit, 43: CPU, 44: Memory, 45: HDD, 46: Bus, 47: Storage medium, 50: Feeder link, 51-1: First link, 52-1: Second link, 52-2: Third link, 53-1: Fourth link, 51-2: Fifth link, 60: Upper air link, 100: Communication path Control device, 101: Communication quality analysis circuit, 102: Decision circuit, 103: Communication path control circuit, 104: Memory device, 110: Airborne relay station, 110-1: First airborne relay station, 110-2: Second airborne relay station, 110-3: Third airborne relay station, 120: Ground station, 120-1: First ground station, 120-2: Second ground station, 130: Ground network, 200: Wireless communication system

Claims

1. A wireless communication system using a plurality of aerial relay stations that move relative to the ground, comprising: one or more ground stations; the plurality of aerial relay stations, each switching a feeder link to a designated ground station according to a schedule; and a communication path control device that controls the communication path, wherein the communication path control device is configured to perform: a process for detecting a weather deterioration area based on a received signal that reaches the ground station from a first aerial relay station via a feeder link; a process for determining, based on the schedule, whether there is a second aerial relay station that moves to overlap the weather deterioration area when a weather deterioration area is detected; a process for setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and a process for opening the set communication path.

2. A communication path control device for controlling a communication path in a wireless communication system comprising one or more ground stations and a plurality of aerial relay stations that move relative to the ground and each switches a feeder link to a designated ground station according to a schedule, the communication path control device being configured to perform the following: a process for detecting a weather deterioration area based on a received signal that reaches the ground station from a first aerial relay station via a feeder link; a process for determining, based on the schedule, whether there is a second aerial relay station that moves to overlap with the weather deterioration area when a weather deterioration area is detected; a process for setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and a process for opening the set up communication path.

3. A communication path control method for controlling a communication path in a wireless communication system comprising one or more ground stations and a plurality of aerial relay stations that move relative to the ground and each switches a feeder link to a designated ground station according to a schedule, the method comprising: detecting a weather deterioration area based on a received signal that reaches the ground station from a first aerial relay station via a feeder link; determining, based on the schedule, whether there is a second aerial relay station that moves to overlap with the weather deterioration area when a weather deterioration area is detected; setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and establishing the set up communication path.

4. A communication path control program to be executed by a communication path control device that controls a communication path in a wireless communication system comprising: one or more ground stations and a plurality of aerial relay stations that move relative to the ground and each switches a feeder link to a designated ground station according to a schedule, the program includes: a process for detecting a weather deterioration area based on a received signal that reaches the ground station from a first aerial relay station via a feeder link; a process for determining, based on the schedule, whether there is a second aerial relay station that moves to overlap the weather deterioration area when a weather deterioration area is detected; a process for setting up a communication path consisting of one or more links that can connect the second aerial relay station and one of the one or more ground stations while avoiding the weather deterioration area when the second aerial relay station is present; and a process for opening the set up communication path.

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