Wireless communication system, ground wireless station, wireless communication method, and wireless communication program

Abstract

The purpose of the present disclosure is to provide technology that enables a ground wireless station to transmit data to a sky wireless station having the longest communication duration. A wireless communication system according to the present disclosure comprises a plurality of sky wireless stations that move in the sky, and a ground wireless station. The wireless communication system calculates a communication duration between each of the plurality of sky wireless stations and the ground wireless station. The wireless communication system furthermore compares the communication duration calculated for each of the plurality of sky wireless stations, and selects the sky wireless station having the longest communication duration as a communication station. The wireless communication system furthermore causes the ground wireless station to transmit data to the communication station.

Description

Wireless communication system, terrestrial wireless station, wireless communication method, and wireless communication program

[0001] The present disclosure relates to a wireless communication system including an airborne radio station and a terrestrial radio station, a terrestrial radio station, a wireless communication method for communicating between the terrestrial radio station and the airborne radio station, and a wireless communication program.

[0002] With the recent spread of 4G / 5G services, the demand for network communication bandwidth is increasing year by year. Furthermore, ultra-wide coverage is required for future B5G / 6G services. To expand the coverage area, B5G / 6G services are expected to use NTNs (Non-Terrestrial Networks). This will enable the expansion of service areas to locations where the construction of terrestrial base stations is expensive or difficult, such as mountainous, marine, or aerial locations. It will also enable the construction of communication systems that are resistant to terrestrial disasters.

[0003] In NTN, satellites and other overhead radio stations that move through the sky, including outer space, are responsible for relaying data. The time during which communication is possible between these stations and terrestrial radio stations (terrestrial terminal stations, terrestrial base stations, etc.) depends on their positions.

[0004] Patent Literature 1 discloses a technology in which an overhead radio station calculates the antenna coverage for each time based on its own orbital information and identifies the communication available time period for each area. This enables control such as directing the antenna direction of the overhead radio station to the area where communication is available during the communication available time period.

[0005] International Publication No. 2022 / 137493

[0006] However, for terrestrial radio stations, there is a risk that they may fall out of the coverage area of ​​an overhead radio station while transmitting data if they select an overhead radio station with a short communication duration as their communication partner.If there are multiple overhead radio stations with which they can communicate, it is desirable for the terrestrial radio station to transmit data to the overhead radio station with the longest communication duration.

[0007] However, with the above-mentioned method, the terrestrial radio station cannot transmit data to the overhead radio station with the longest communication duration among the multiple overhead radio stations.

[0008] In order to solve the above-mentioned problems, the present disclosure aims to provide a technology that enables a terrestrial radio station to transmit data to an overhead radio station with the longest communication duration.

[0009] A first aspect of the present disclosure is a wireless communication system comprising a plurality of overhead radio stations moving in the sky and a terrestrial radio station, and is preferably configured to perform the following processes: calculating a communication duration between each of the plurality of overhead radio stations and the terrestrial radio station; comparing the communication durations calculated for each of the plurality of overhead radio stations and selecting the overhead radio station with the longest communication duration as a communication station; and causing the communication station to transmit data to the terrestrial radio station.

[0010] In addition, a second aspect is a terrestrial radio station capable of wireless communication with a plurality of overhead radio stations moving in the sky, and is preferably configured to perform the following processes: acquiring information on the duration of communication between each of the plurality of overhead radio stations and the station itself; comparing the duration of communication between each of the plurality of overhead radio stations and the station itself, and selecting the overhead radio station with the longest duration of communication as the communication station; and transmitting data to the communication station.

[0011] Furthermore, a third aspect is preferably a wireless communication method including: calculating a communication duration between each of a plurality of airborne radio stations moving in the sky and a terrestrial radio station; comparing the calculated communication durations for each of the plurality of airborne radio stations and selecting the airborne radio station with the longest communication duration as the communication station; and transmitting data from the terrestrial radio station to the communication station.

[0012] In addition, a fourth aspect is preferably a wireless communication program including a program that executes the following processes: a process of calculating the duration of communication between each of a plurality of overhead radio stations moving in the sky and a terrestrial radio station; a process of comparing the calculated duration of communication between each of the plurality of overhead radio stations and selecting the overhead radio station with the longest duration of communication as the communication station; and a process of causing the communication station to transmit data to the terrestrial radio station.

[0013] In the present disclosure, the duration of communication between each of a plurality of airborne radio stations and a terrestrial radio station is calculated, and the airborne radio station with the longest duration of communication is selected as the communication station. Furthermore, the terrestrial radio station is made to transmit data to the selected communication station. This allows the terrestrial radio station to transmit data to the airborne radio station with the longest duration of communication.

[0014] Fig. 1 is a diagram showing an example of the configuration of a wireless communication system according to a first embodiment. Fig. 2 is a flowchart explaining processing executed by an airborne radio station and a terrestrial radio station according to the first embodiment. Fig. 3 is a diagram showing a method in which a terrestrial radio station selects a communication station based on transmission signals from a first airborne radio station and a second airborne radio station according to the first embodiment. Fig. 4 is a block diagram showing an example of the configuration of an airborne radio station according to the first embodiment. Fig. 5 is a block diagram showing an example of the configuration of a terrestrial radio station according to the first embodiment. Fig. 6 is a diagram showing the hardware configuration of an airborne radio station according to the first embodiment. Fig. 7 is a diagram showing the hardware configuration of a terrestrial radio station according to the first embodiment.

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

[0016] 1 is a diagram showing an example of the configuration of a wireless communication system 100 according to embodiment 1. The wireless communication system 100 includes a plurality of first-layer airborne radio stations 110, a plurality of second-layer airborne radio stations 120, and a third-layer airborne radio station 130. The system further includes a terrestrial terminal station 180 and a plurality of terrestrial base stations 140.

[0017] The first-tier airborne radio station 110 is a radio relay station that moves in the sky, including outer space, or that moves in the sky, including outer space, but appears to be stationary relative to the ground. The first-tier airborne radio station 110 is, for example, a High Altitude Platform System (HAPS), a drone, an unmanned aerial vehicle, or an aircraft.

[0018] Neighboring first-layer airborne radio stations 110 are connected to each other by intralayer circuits 2 and perform wireless or optical signal communication. The first-layer airborne radio stations 110 connected by the intralayer circuits 2 form a first airborne network 111.

[0019] The second-layer airborne radio station 120 is also a radio relay station that moves in the sky, including outer space, or that moves in the sky, including outer space, but appears to be stationary relative to the ground. Examples of the second-layer airborne radio station 120 include LEO (Low Earth Orbit) satellites that move in sun-synchronous orbits, sun-synchronous quasi-recurrent orbits, circular orbits, polar orbits, etc. at orbital altitudes of 2000 km or less.

[0020] Neighboring second-layer airborne radio stations 120 are connected to each other by intralayer circuits 4 and perform radio or optical signal communication. The second-layer airborne radio stations 120 connected by the intralayer circuits 4 form a second airborne network 121.

[0021] The second layer airborne radio station 120 receives data transmitted from the ground terminal station 180 via the inter-ground station line 1 .

[0022] The second layer airborne radio station 120 relays data via the second airborne network 121 to a second layer airborne radio station 120 that can communicate with an airborne radio station at a different layer from itself, or to a second layer airborne radio station 120 that can communicate with a terrestrial base station 140.

[0023] The second-layer air radio station 120 that can communicate with an air radio station in a different hierarchical layer from itself transmits the received data to the air radio station in a different hierarchical layer from itself via the inter-network lines 3 and 8. The second-layer air radio station 120 that can communicate with the terrestrial base station 140 transmits the received data to the terrestrial base station 140 via the inter-base station line 5.

[0024] The same applies to the third-layer radio station 130, so a description thereof will be omitted. The third-layer radio station 130 is, for example, a GEO (Geostationary Orbit) satellite.

[0025] If necessary, the wireless communication system 100 may include a fourth layer airborne radio station, a fifth layer airborne radio station, and so on.

[0026] Hereinafter, when there is no need to distinguish between the first layer radio station 110, the second layer radio station 120, and the third layer radio station 130, they will be simply referred to as radio stations 160. Only when there is a need to distinguish between them will the respective names be written.

[0027] The terrestrial base station 140 receives data transmitted from the airborne radio station 160 via the inter-base station line 5 and transmits the data to the terrestrial network. In other words, the terrestrial base station 140 functions as a gateway station for the terrestrial network. The terrestrial base station 140 may be a portable radio station such as a very small aperture terminal (VSAT).

[0028] The ground terminal station 180 is a smartphone, an IoT terminal, a Bluetooth (registered trademark) communication device, or the like that performs wireless communication with the airborne radio station 160 via the inter-ground station line 1. The ground terminal station 180 transmits data such as internet traffic to the airborne radio station 160.

[0029] In this manner, in the wireless communication system 100 of the present disclosure, the terrestrial terminal station 180 transmits data to the overhead radio station 160. The transmitted data is relayed by the overhead radio station 160 and transmitted to the terrestrial base station 140. Although not explained further, it is of course also possible for the data transmitted by the terrestrial base station 140 to be relayed by the overhead radio station 160 and transmitted to the terrestrial terminal station 180.

[0030] 1 illustrates an example in which multiple airborne radio stations 160 form a three-layer non-terrestrial network, but the airborne radio stations 160 do not necessarily need to be arranged in layers. The wireless communication system 100 disclosed herein may include two or more airborne radio stations 160 and one terrestrial radio station 170 (terrestrial base station 140 or terrestrial terminal station 180), and the layers of the two or more airborne radio stations 160 may be the same or different.

[0031] <Method for terrestrial radio station to transmit data to overhead radio station with longest communication duration> Hereinafter, a method for terrestrial radio station 170 to transmit data to the overhead radio station 160 with the longest communication duration among multiple overhead radio stations 160 will be described. Here, the terrestrial radio station 170 refers to a terrestrial base station 140 or a terrestrial terminal station 180.

[0032] 2 is a flowchart illustrating the processing executed by the overhead radio station 160 and the terrestrial radio station 170 according to embodiment 1. For simplicity of explanation, a method will be described here in which the terrestrial radio station 170 transmits data to the overhead radio station 160 with which the communication time is longer than the other of the two overhead radio stations 160.

[0033] First, the first overhead radio station 160 transmits information on the duration of communication for each ground area (hereinafter simply referred to as "area") (step S01). The first overhead radio station 160 periodically calculates the duration of communication for each area based on its own orbital information and transmits the calculation results each time. Examples of a transmission method include a beacon at a specific frequency. Generally, a frequency is assigned to a beacon signal that is unique to the overhead radio station 160 that transmitted the signal, or that rarely overlaps with other overhead radio stations 160. By using a beacon, the terrestrial radio station 170 that receives the transmitted signal can identify the overhead radio station 160 that transmitted the signal from the frequency information.

[0034] It is preferable that the information on the communication duration be transmitted together with the time (also called the epoch) at which the orbital information used to calculate the information was generated.

[0035] Next, the terrestrial radio station 170 receives the transmission signal from the first overhead radio station 160 (step S02). Next, the terrestrial radio station 170 determines the duration of communication between itself and the first overhead radio station 160 from the information on the communication duration for each area included in the transmission signal (step S03). The determined communication duration is stored in the storage device 173 of the terrestrial radio station 170.

[0036] Next, the second overhead radio station 160 transmits information on the communication duration for each area (step S04), in the same manner as the first overhead radio station 160. Like the first overhead radio station 160, the second overhead radio station 160 also periodically calculates the communication duration for each area based on its own orbit information, and transmits the calculation results each time.

[0037] Furthermore, the terrestrial radio station 170 receives the transmission signal from the second overhead radio station 160 (step S05). Next, the terrestrial radio station 170 determines the duration of communication between itself and the second overhead radio station 160 from the information on the communication duration for each area included in the transmission signal (step S06). As in the case of the first overhead radio station 160, the determined communication duration is stored in the storage device 173.

[0038] Next, the terrestrial radio station 170 compares the communication duration of the first overhead radio station 160 with the communication duration of the second overhead radio station 160, and selects the overhead radio station 160 with the longest communication duration as the communication station (step S07).

[0039] Furthermore, the terrestrial radio station 170 transmits data to the selected communication station during a time period when communication with the selected communication station is possible (step S08).

[0040] 3 is a diagram showing a method according to the first embodiment in which the terrestrial radio station 170 selects a communication station based on signals transmitted from the first overhead radio station 160 and the second overhead radio station 160. Note that the time information in the diagram is merely an example.

[0041] The table in the upper part shows information about the communication duration contained in the signal transmitted from the first overhead radio station 160. The communication duration is listed for each area. The communication duration information is given by the start and end times of the communication, which allows the terrestrial radio station 170 to know the time period during which communication with the overhead radio station 160 is possible. Therefore, the terrestrial radio station 170 can transmit its own data to the overhead radio station 160 during that time period.

[0042] The middle table shows information about communication duration times included in the signal transmitted from the second overhead radio station 160. As with the top table, communication duration times are listed for each area.

[0043] The terrestrial wireless station 170 acquires its own location information using a Global Navigation Satellite System (GNSS) or the like, and identifies the area it is in. The terrestrial wireless station 170 identifies information on the communication duration for the area in which it is located from information on the communication duration for each area, and stores this information in the storage device 173.

[0044] The table at the bottom shows information on communication duration stored in the storage device 173 of the terrestrial radio station 170. Here, as an example, a case is shown in which the terrestrial radio station 170 is located in area B. The terrestrial radio station 170 stores a list of communication durations between itself and each of the first overhead radio station 160 and the second overhead radio station 160. The terrestrial radio station 170 compares the communication durations of the first overhead radio station 160 and the second overhead radio station 160 based on the list, and selects the overhead radio station 160 with the longest communication duration as the communication station.

[0045] In the example of the lower table, the first overhead radio station 160 starts communication at 11:10 and ends it at 11:18. Therefore, the duration of communication for the first overhead radio station 160 is 8 minutes. On the other hand, the second overhead radio station 160 starts communication at 11:10 and ends it at 11:20. Therefore, the duration of communication for the second overhead radio station 160 is 10 minutes. In this case, the second overhead radio station 160, which has the longer duration of communication, is selected as the communication station.

[0046] The communication duration information is preferably given by the start and end times of the communication, but it may also be given by only the difference between the start and end times of the communication. Furthermore, the communication duration information included in the transmission signal does not necessarily have to be information for each area, and may be information only for the area where the terrestrial radio station 170 is located.

[0047] 4 is a block diagram showing an example of the configuration of an overhead radio station 160 according to the first embodiment. While the case of a first-layer overhead radio station 110 will be described here, the same applies to the overhead radio stations 160 in other layers. The intra-layer communication circuit 161 connects and communicates with a nearby first-layer overhead radio station 110 via intra-layer line 2. The base station communication circuit 162 connects and communicates with a terrestrial base station 140 via inter-base station line 5. The ground station communication circuit 163 connects and communicates with a terrestrial terminal station 180 via inter-ground station line 1. The inter-network communication circuit 166 connects and communicates with a nearby overhead radio station 160 in another layer (here, the second-layer overhead radio station 120) via inter-network line 3.

[0048] The calculation circuit 165 periodically calculates the communication duration for each area based on its own orbit information. The calculation result is transmitted, for example, from the base station communication circuit 162 to the terrestrial base station 140 via the inter-base station line 5, or from the terrestrial station communication circuit 163 to the terrestrial terminal station 180 via the inter-terrestrial station line 1. The calculation result may be transmitted via a control line (not shown) different from the line used for transmitting and receiving traffic data, or may be transmitted by another method.

[0049] 5 is a block diagram showing an example of the configuration of a terrestrial radio station 170 according to embodiment 1. A communication circuit 171 receives a signal transmitted from an overhead radio station 160 via an inter-base station line 5, an inter-terrestrial station line 1, or a control line (not shown).

[0050] The control circuit 172 determines the duration of communication between its own station and the originating overhead radio station 160 from the transmission signal received by the communication circuit 171, and stores the determined result in the memory device 173. When information on the duration of communication for multiple overhead radio stations 160 is stored in the memory device 173, the control circuit 172 compares the duration of communication for each of the multiple overhead radio stations 160 and selects the overhead radio station 160 with the longest duration of communication as the communication station. The transmission data generation circuit 174 generates data to be transmitted and sends it to the communication circuit 171. The communication circuit 171 transmits data to the overhead radio station 160 selected as the communication station via the inter-ground station line 1 during a time period when communication with the overhead radio station 160 is possible.

[0051] The processes performed by the above-described airborne radio station 160 and terrestrial radio station 170 may be executed by a computer equipped with a CPU and memory and having a wireless communication program stored in the memory, or may be executed by a program using an integrated circuit such as an FPGA. The wireless communication program may be provided by being recorded on a storage medium or via a network.

[0052] FIG. 6 is a diagram showing the hardware configuration of the overhead radio station 160 according to the first embodiment.

[0053] The airborne radio station 160 has computer functions, with an input unit 40, an output unit 41, a communication unit 42, a CPU (Central Processing Unit, also called a processor) 43, a memory 44, and an HDD (Hard Disk Drive) 45 connected via a bus 46. The airborne radio station 160 is also capable of inputting and outputting data to and from a computer-readable storage medium 47.

[0054] The input unit 40 is, for example, a keyboard and a mouse, etc. The output unit 41 is, for example, a display device such as a display.

[0055] The communication unit 42 is a communication interface that communicates with, for example, other airborne radio stations 160 or terrestrial radio stations 170 .

[0056] The memory 44 may be, 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.

[0057] The memory 44 and HDD 45 are storage devices that store data such as a wireless communication program, generated orbit information, and information on the duration of communication for each area. The CPU 43 controls each component of the overhead radio station 160. The CPU 43 reads the wireless communication program stored in the memory 44 or HDD 45 and executes predetermined processes including the process described in the flowchart of FIG. 2.

[0058] The storage medium 47 is capable of storing wireless communication programs and the like that cause the overhead radio station 160 to perform its functions. The storage medium 47 is a USB (Universal Serial Bus) memory, a CD-ROM (Compact Disc Read Only Memory), or the like.

[0059] The architecture of the overhead radio station 160 is not limited to the example shown in the figure.

[0060] FIG. 7 is a diagram showing the hardware configuration of the terrestrial radio station 170 according to the first embodiment.

[0061] The terrestrial radio station 170 has an input unit 50, an output unit 51, a communication unit 52, a CPU 53, a memory 54, and an HDD 55 connected via a bus 56, and functions as a computer. The terrestrial radio station 170 is also capable of inputting and outputting data to and from a computer-readable storage medium 57.

[0062] The input unit 50 and output unit 51 are similar to those in the case of the above-mentioned overhead radio station 160, and therefore will not be described here.

[0063] The communication unit 52 is a communication interface that communicates with, for example, an overhead radio station 160 .

[0064] The memory 54 and HDD 55 are the storage device 173 described above that stores, for example, a wireless communication program and information on the duration of communication acquired from the overhead radio station 160. The CPU 53 controls each unit constituting the terrestrial radio station 170 and performs predetermined processing, etc. The CPU 53 reads the wireless communication program stored in the memory 54 or the HDD 55 and executes predetermined processing including the processing described in the flowchart of FIG.

[0065] The storage medium 57 will not be described here because it is the same as that of the above-mentioned airborne radio station 160. The architecture of the terrestrial radio station 170 is not limited to the example shown in the figure.

[0066] As described above, the wireless communication system 100 of the present disclosure calculates the duration of communication between each of the multiple overhead radio stations 160 and the terrestrial radio station 170, and selects the overhead radio station with the longest duration of communication as the communication station. Furthermore, the terrestrial radio station 170 is made to transmit data to the selected communication station. This allows the terrestrial radio station to transmit data to the overhead radio station with the longest duration of communication.

[0067] <Variation 1> The process of calculating the communication duration does not necessarily have to be performed by the overhead radio station 160. Furthermore, the process of comparing the communication durations of the multiple overhead radio stations 160 and selecting the overhead radio station 160 with the longest communication duration as the communication station does not necessarily have to be performed by the terrestrial radio station 170. These processes may be performed, for example, by a central device that manages the non-terrestrial network, or may be performed by at least one of the overhead radio station 160 and the terrestrial radio station 170. If the terrestrial radio station 170 does not select the communication station itself, the device that selected the communication station notifies the terrestrial radio station 170 of the selection result and causes the selected communication station to transmit data to the terrestrial radio station 170. This provides the same effects as those of the first embodiment.

[0068] <Modification 2> The communication duration of the overhead radio station 160 does not have to be calculated based on the orbital information of the overhead radio station 160, but may be calculated based on position information or the like.

[0069] The present disclosure is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the present disclosure. Furthermore, the embodiments and modifications may be implemented in appropriate combinations, in which case the combined effects can be obtained.

[0070] 1: Inter-ground station line, 2: Intra-layer line, 3: Inter-network line, 4: Intra-layer line, 5: Inter-base station line, 8: Inter-network line, 40: Input unit, 41: Output unit, 42: Communication unit, 43: CPU, 44: Memory, 45: HDD, 46: Bus, 47: Storage medium, 50: Input unit, 51: Output unit, 52: Communication unit, 53: CPU, 54: Memory, 55: HDD, 56: Bus, 57: Storage medium, 100: Wireless communication system, 110: First layer airborne radio station, 111: First air network, 120: second layer airborne radio station, 121: second airborne network, 130: third layer airborne radio station, 140: terrestrial base station, 160: airborne radio station, 161: intra-layer communication circuit, 162: base station communication circuit, 163: ground station communication circuit, 165: calculation circuit, 166: inter-network communication circuit, 170: terrestrial radio station, 171: communication circuit, 172: control circuit, 173: storage device, 174: transmission data generation circuit, 180: terrestrial terminal station, A to C: area

Claims

1. A wireless communication system comprising a plurality of airborne radio stations moving in the sky and a terrestrial radio station, configured to execute the following processes: calculating the duration of communication between each of the plurality of airborne radio stations and the terrestrial radio station; comparing the calculated durations of communication between each of the plurality of airborne radio stations and selecting the airborne radio station with the longest duration of communication as the communication station; and causing the communication station to transmit data to the terrestrial radio station.

2. A terrestrial radio station capable of wireless communication with a plurality of overhead radio stations moving in the sky, configured to perform the following processes: acquiring information on the duration of communication between the station and each of the plurality of overhead radio stations; comparing the duration of communication between the station and each of the plurality of overhead radio stations and selecting the overhead radio station with the longest duration of communication as the communication station; and transmitting data to the communication station.

3. A wireless communication method comprising: calculating a duration of communication between each of a plurality of airborne radio stations moving in the sky and a terrestrial radio station; comparing the calculated durations of communication between each of the plurality of airborne radio stations and selecting the airborne radio station with the longest duration of communication as the communication station; and transmitting data from the terrestrial radio station to the communication station.

4. A wireless communication program including a program that executes the following processes: calculating the duration of communication between each of a plurality of overhead radio stations moving in the sky and a terrestrial radio station; comparing the calculated duration of communication between each of the plurality of overhead radio stations and selecting the overhead radio station with the longest duration of communication as the communication station; and causing the communication station to transmit data to the terrestrial radio station.

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