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

Abstract

The purpose of the present disclosure is to provide technology that enables reducing a time window in which a ground terminal station cannot communicate with an aerial wireless station even when time elapses from the time calculated for a communicable time window. A wireless communication system according to the present disclosure includes one or a plurality of ground terminal stations present in a predetermined area, and an aerial wireless station that travels along an orbit overhead, and is capable of periodically communicating with the predetermined area. The wireless communication system is configured to execute processing for acquiring or generating a change over time in the communication start time of the aerial wireless station for each orbit pattern of the aerial wireless station, processing for calculating a communicable time window of the aerial wireless station in the predetermined area on the basis of orbit information of the aerial wireless station, and processing for correcting the calculated communicable time window in accordance with the change over time, orbit pattern, and timing at which the ground terminal station transmits data. The ground terminal station is configured to execute processing for acquiring the corrected communicable time window, and processing for transmitting data as the corrected communicable time window starts.

Description

Wireless Communication System, Wireless Communication Method, Control Station, and Wireless Communication Program

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

[0002] Due to the spread of 4G / 5G services in recent years, the demand for using the communication bandwidth of the network has been increasing year by year. In addition, for future B5G / 6G services, ultra-coverage is required. In B5G / 6G services, in order to expand the coverage area, the use of NTN (Non-Terrestrial Network) is expected. As a result, it is possible to expand the service area to places where the laying cost of terrestrial base stations is high or difficult, such as mountains, seas, or the air. It is also possible to construct a communication system that is resistant to terrestrial disasters.

[0003] In NTN, an aerial radio station moving in the sky including outer space is responsible for relaying data. For example, Non-Patent Document 1 discloses a technique of wireless communication using an unmanned aerial vehicle. It is known that an aerial radio station such as an unmanned aerial vehicle can communicate with a terrestrial area periodically because it orbits in the sky. That is, the communicable time zone, which is the time zone when the aerial radio station and the terrestrial terminal station can communicate, can be calculated based on the orbit information of the aerial radio station.

[0004] For example, Non-Patent Document 1 discloses a technique of calculating the receivable time based on orbit prediction in two-terminal simultaneous reception. The receivable time is the start time of the communicable time zone. Therefore, the terrestrial terminal station can efficiently communicate with the aerial radio station by acquiring the receivable time in advance, for example, by notification information, and starting data transmission / reception processing in that time zone.

[0005] Kojima et al., "A Study on the Accuracy of Simultaneous Reception Prediction at Two Terminals in a Low Earth Orbit Satellite Sensing Platform Experiment," IEICE Research Institute, 2024, B-3-03; Wei Feng et al., "UAV-Aided MIMO Communications for 5G Internet of Things," IEEE INTERNET OF THINGS JOURNAL, APRIL 2019, VOL. 6, NO. 2.

[0006] It is generally known that the orbits of aerial radio stations drift over time, which in turn causes drift in the available communication timeframes. On the other hand, ground terminal stations that utilize NTN often find it difficult to communicate without using NTN. Therefore, ground terminal stations that utilize NTN often receive data from aerial radio stations less frequently. As a result, the day on which a ground terminal station transmits data to an aerial radio station may differ from the day on which the ground terminal station obtains the available communication timeframe in advance through broadcast information.

[0007] In this case, the communication window on the day a ground terminal station transmits data to an airborne radio station may differ from the communication window that the ground terminal station had previously received. As a result, there was a problem where, even though the ground terminal station was processing data transmission, there were periods when communication with the airborne radio station was impossible.

[0008] The primary objective of this disclosure is to provide a wireless communication system that can reduce the period of time during which a ground terminal station is unable to communicate with an airborne radio station, even when time has elapsed since the time the communication-available period was calculated, in order to solve the aforementioned problems.

[0009] Furthermore, a second objective of this disclosure is to provide a wireless communication method that can reduce the period of time during which a ground terminal station is unable to communicate with an airborne radio station, even when time has elapsed since the time the communication-available period was calculated.

[0010] Furthermore, a third objective of this disclosure is to provide a control station that can reduce the period of time during which ground terminal stations are unable to communicate with airborne radio stations, even when time has elapsed since the time the communication-enabled period was calculated.

[0011] Furthermore, a fourth objective of this disclosure is to provide a wireless communication program that can reduce the period of time during which a ground terminal station is unable to communicate with an airborne radio station, even if time has elapsed since the time the communication-enabled period was calculated.

[0012] A first aspect of this disclosure is a wireless communication system comprising one or more ground terminal stations located in a predetermined area and an aerial radio station that moves along an orbit in the air and periodically becomes capable of communicating with the predetermined area, wherein the system is configured to perform the following for each orbital pattern of the aerial radio station: a process to acquire or generate the time-dependent change in the communication start time of the aerial radio station; a process to calculate the communication-enabled time period in the predetermined area of ​​the aerial radio station based on the orbital information of the aerial radio station; and a process to correct the calculated communication-enabled time period according to the time-dependent change, orbital pattern, and the timing at which the ground terminal station transmits data, and the ground terminal station is configured to perform the following: a process to acquire the corrected communication-enabled time period and a process to transmit data as the corrected communication-enabled time period begins.

[0013] Furthermore, a second aspect of this disclosure is a wireless communication method to be implemented in a wireless communication system comprising one or more ground terminal stations located in a predetermined area and an aerial radio station that moves in an orbit above the air and periodically becomes capable of communicating with the predetermined area, wherein the wireless communication method preferably comprises: acquiring or generating the time-dependent change in the communication start time of the aerial radio station for each orbital pattern of the aerial radio station; calculating the communication-enabled time period in the predetermined area of ​​the aerial radio station based on the orbital information of the aerial radio station; correcting the calculated communication-enabled time period in accordance with the time-dependent change, orbital pattern, and the timing of data transmission by the ground terminal station; and transmitting data as the corrected communication-enabled time period begins.

[0014] Furthermore, a third aspect of this disclosure is a control station that has one or more ground terminal stations located in a predetermined area under its control, and is configured to perform the following processes for each orbital pattern of an airborne radio station that moves in an orbit above the air and periodically becomes able to communicate with the predetermined area: a process to acquire or generate the time-dependent change in the communication start time of an airborne radio station; a process to calculate the time period during which an airborne radio station is able to communicate in a predetermined area based on the orbital information of the airborne radio station; a process to correct the calculated time period during which a communication is possible according to the time-dependent change, the orbital pattern, and the timing at which the ground terminal station transmits data; and a process to notify the airborne radio station of the corrected time period during which a communication is possible.

[0015] Furthermore, a fourth aspect of this disclosure is a wireless communication program to be executed by a control station having a processor and memory and having one or more ground terminal stations located in a predetermined area under its command, wherein the program is stored in memory, is computer-readable, and preferably includes a program to cause the processor to execute: a process for acquiring or generating the time-dependent change in the communication start time of an airborne radio station for each airborne radio station's orbital pattern, a process for calculating the time period during which the airborne radio station can communicate in a predetermined area based on the airborne radio station's orbital information, a process for correcting the calculated time period during which the airborne radio station can communicate according to the time-dependent change, orbital pattern, and the timing at which the ground terminal station transmits data, and a process for notifying the airborne radio station of the corrected time period during which it can communicate.

[0016] According to the first to fourth aspects of this disclosure, even if time has elapsed since the time the communication-enabled period was calculated, the period during which the ground terminal station is unable to communicate with the airborne radio station can be reduced.

[0017] This is a diagram showing an example configuration of the wireless communication system 100 according to Embodiment 1 of this disclosure. This is a table showing the change over time of the communication start time, which is prepared in advance by the control station 170 according to Embodiment 1 of this disclosure. This is a table showing information on the communication-enabled time period corrected by the control station 170 according to Embodiment 1 of this disclosure. This is a diagram showing the communication-enabled time period according to Embodiment 1 of this disclosure. This is a flowchart explaining the processes performed by the control station 170, beacon, airborne radio station 160, and ground terminal station 180 according to Embodiment 1 of this disclosure. This is a block diagram showing an example configuration of the control station 170 according to Embodiment 1 of this disclosure. This is a block diagram showing an example configuration of the airborne radio station 160 according to Embodiment 1 of this disclosure. This is a block diagram showing an example configuration of the ground terminal station 180 according to Embodiment 1 of this disclosure. This is a diagram showing the hardware configuration of the control station 170 according to Embodiment 1 of this disclosure. This is a diagram showing the hardware configuration of the airborne radio station 160 according to Embodiment 1 of this disclosure. This is a diagram showing the hardware configuration of the ground terminal station 180 according to Embodiment 1 of this disclosure.

[0018] Embodiments of this disclosure will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repetition of the description may be omitted.

[0019] Embodiment 1 Figure 1 is a diagram showing an example configuration of a wireless communication system 100 according to Embodiment 1 of the present disclosure. The wireless communication system 100 comprises 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. Furthermore, the wireless communication system 100 comprises a control station 170, a ground terminal station 180, and a plurality of ground base stations 140.

[0020] The first-layer airborne radio station 110 is a radio relay station that moves in an orbit above the Earth, including outer space, and is capable of periodically communicating with a predetermined ground area. The first-layer airborne radio station 110 is, for example, a HAPS (High Altitude Platform System), a drone, an unmanned aerial vehicle, or an aircraft.

[0021] Nearby first-layer airborne radio stations 110 are connected by an intra-layer circuit 2 and communicate wirelessly or via optical signals. The first-layer airborne radio stations 110 connected by the intra-layer circuit 2 form a first airborne network 111.

[0022] The second-layer upper-air radio station 120 is similarly a radio relay station that moves in an orbit above the Earth, including in outer space, and is capable of periodically communicating with a predetermined ground area. Examples of the second-layer upper-air 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 an orbital altitude of 2000 km or less.

[0023] Nearby second-layer airborne radio stations 120 are connected by an intra-layer circuit 4 and communicate wirelessly or via optical signals. The second-layer airborne radio stations 120 connected by the intra-layer circuit 4 form a second airborne network 121.

[0024] The second-layer airborne radio station 120 receives data transmitted from the ground terminal station 180 via the ground station inter-station link 1.

[0025] The second-layer airborne radio station 120 relays data via the second airborne network 121 to another second-layer airborne radio station 120 that can communicate with an airborne radio station of a different layer, or to another second-layer airborne radio station 120 that can communicate with a ground base station 140.

[0026] A second-layer airborne radio station 120, capable of communicating with airborne radio stations on different layers, transmits the data it receives to the airborne radio station on a different layer via inter-network lines 3 and 8. A second-layer airborne radio station 120, capable of communicating with a ground base station 140, transmits the data it receives to the ground base station 140 via inter-base station line 5.

[0027] The same applies to the third-layer orbital radio station 130, so its explanation will be omitted. The third-layer orbital radio station 130 is, for example, a GEO (Geostationary Orbit) satellite.

[0028] Furthermore, the wireless communication system 100 may include a fourth-layer airborne radio station, a fifth-layer airborne radio station, and so on, as needed.

[0029] Hereafter, unless it is necessary to distinguish between the first-layer airborne radio station 110, the second-layer airborne radio station 120, and the third-layer airborne radio station 130, they will simply be referred to as airborne radio station 160. Only when it is necessary to distinguish between them will their respective names be listed.

[0030] The ground base station 140 receives data transmitted from the airborne radio station 160 via the inter-base station line 5 and transmits it to the ground network. In other words, the ground base station 140 functions as a gateway station for the ground network. The ground base station 140 may also be a portable radio station such as a Very Small Aperture Terminal (VSAT).

[0031] The control station 170 acquires orbital information from the airborne radio station 160 via the control line 6. Based on the acquired orbital information, the control station 170 periodically calculates the communication time period of the airborne radio station 160 in the area where the ground terminal station 180 is located. The control station 170 covers the area where the ground terminal station 180 is located and is a ground base station that has the ground terminal station 180 under its command. Alternatively, the control station 170 may be one of the airborne radio stations 160, and is not limited to being on the ground or in the air.

[0032] The ground terminal station 180 is a smartphone, IoT terminal, Wi-Fi® communication device, Bluetooth® communication device, etc., that communicates wirelessly with the airborne radio station 160 via the ground station inter-station line 1. The ground terminal station 180 transmits data such as internet traffic to the airborne radio station 160.

[0033] Thus, in the wireless communication system 100 of this disclosure, the ground terminal station 180 transmits data to the airborne radio station 160. The transmitted data is relayed by the airborne radio station 160 and transmitted to the ground base station 140. Although not explained here, it is also possible for the ground base station 140 to transmit data to the ground terminal station 180 via relay by the airborne radio station 160.

[0034] Although Figure 1 illustrates an example in which multiple airborne radio stations 160 constitute a three-tiered non-terrestrial network, the airborne radio stations 160 do not necessarily have to be arranged according to tier. The wireless communication system 100 of this disclosure may include one airborne radio station 160, one or more ground terminal stations 180, and a control station 170.

[0035] Figure 2 is a table showing the change over time of the communication start time, which is prepared in advance by the control station 170 according to Embodiment 1 of this disclosure. First, the control station 170 calculates the time of change in the communication start time based on the orbital information of the airborne radio station 160. The control station 170 generates a table showing the change over time of the communication start time by recording the calculation results. This table is stored, for example, in a storage device 173 of the control station 170. This table is prepared before the day on which the airborne radio station 160 transmits the notification information described later to the ground terminal station 180.

[0036] The above records are made at regular intervals based on orbital information for a certain period, such as the past 30 days or less. These regular intervals are, for example, several hours to 24 hours. Figure 2 shows a table created when records are made every 24 hours based on orbital information for the past 7 days.

[0037] Furthermore, the above-mentioned recording is performed for each trajectory pattern. Figure 2 shows a table created when recording is performed for each of the four types of trajectory patterns, A to D. The trajectory pattern information may be stored in advance in a storage device 173 of the control station 170, for example. Alternatively, the trajectory pattern information may be stored in the storage device 173 based on information set externally by the user, or it may be stored in the storage device 173 based on information that is automatically set based on the acquired trajectory information.

[0038] While this description shows a method for creating a table of the time-dependent changes in the communication start time of the airborne radio station 160, the embodiments of this disclosure are not limited to this. For example, the control station 170 may obtain the time-dependent changes in the communication start time of the airborne radio station 160 from an external source, or it may generate it in the form of a table or graph based on the measured communication start time. In other words, the control station 170 can obtain or generate the time-dependent changes in the communication start time of the airborne radio station 160 by some means.

[0039] Figure 3 is a table showing information on the communication-enabled time period corrected by the control station 170 according to Embodiment 1 of this disclosure. However, in the following figures, the date and time information is an example.

[0040] First, the control station 170 calculates the communication time period for the airborne radio station 160 in a predetermined area based on the orbital information of the airborne radio station 160. The calculated communication time period information is listed for each generation time (also called epoch) of the orbital information used in the calculation and stored in the control station 170's storage device 173. The communication time period information is given by the communication start time and communication end time.

[0041] Next, the control station 170 corrects the calculated communication availability period according to the timing at which the ground terminal station 180 transmits data. This correction is performed based on the table showing the time-dependent changes in communication start times, as shown in Figure 2. Specifically, the control station 170 corrects the communication availability period based on the table showing the time-dependent changes in communication start times, the orbital pattern of the corresponding airborne radio station 160, and the timing of data transmission.

[0042] Furthermore, it is assumed that the timing for data transmission is acquired by the control station 170 before the ground terminal station 180 transmits the data. For example, the timing for data transmission may be acquired in advance by the control station 170 from the target ground terminal station 180, or it may be stored in the control station 170's storage device 173 as the timing when the ground terminal station 180 periodically transmits data.

[0043] Furthermore, the control station 170 transmits the corrected communication availability period to the beacon. The airborne radio station 160 obtains the corrected communication availability period from the beacon and transmits it to the ground terminal station 180 as broadcast information. As a result, the ground terminal station 180 can know the corrected communication availability period in advance, depending on the timing of data transmission.

[0044] Using the table shown in FIG. 3, a specific example of the process in which the control station 170 corrects the communicable time period is shown. Note that the values shown in the first row of the table are values related to the communicable time period calculated based on the orbital information on the day of data transmission. Further, the values shown in the second row of the table are values related to the communicable time period calculated based on the orbital information three days before data transmission. This value is stored in the first ground terminal station 180. Furthermore, the values shown in the third row of the table are values related to the communicable time period calculated based on the orbital information six days before data transmission. This value is stored in the second ground terminal station 180.

[0045] The first and second columns of the table indicate the communicable time period before correction. The communicable time period before correction is the communicable time period calculated by the control station 170 based on the orbital information of the airborne radio station 160.

[0046] For example, as shown in the first row, the communicable time period 10-1 calculated based on the orbital information on the day of data transmission is from 10:10 to 10:20. This communicable time period 10 is considered to be the value closest to the communicable time period at the timing of data transmission. Similarly, as shown in the second row, the communicable time period 10-2 calculated based on the orbital information three days before is from 10:09 to 10:19. Similarly, as shown in the third row, the communicable time period 10-3 calculated based on the orbital information six days before is from 10:13 to 10:23. The reason why the communicable time period varies depending on the orbital information generation time is that the orbit of the airborne radio station 160 shifts over time.

[0047] The third and fourth columns of the table indicate the information necessary for correction. The orbit pattern is the orbit pattern of the airborne radio station 160 that is the target of data transmission by the ground terminal station 180. The variation time is the deviation of the communication start time estimated based on the table showing the change over time of the communication start time, the corresponding orbit pattern of the airborne radio station 160, and the timing of data transmission.

[0048] For example, as shown in the third column of the second row, the orbit pattern of the airborne radio station 160 that is the target of data transmission by the ground terminal station 180 is B. Similarly, as shown in the fourth column of the second row, the estimated variation time at a point three days before is -60 seconds.

[0049] Furthermore, as shown in the third row, third column, the orbital pattern of the airborne radio station 160, which is the target of data transmission from the ground terminal station 180, is C. Similarly, as shown in the second row, fourth column, the estimated fluctuation time three days prior is 270 seconds.

[0050] Note that the first row shows information for the day the data was transmitted. Therefore, the communication availability time period 10-1 shown in the first row and columns 1 and 2 is considered to be the closest value to the communication availability time period at the time the data was transmitted. In other words, it is considered that there is no need to correct the communication availability time period 10-1, and therefore there are no values ​​in the first row and columns 3 and 4.

[0051] The fifth and sixth columns of the table show the corrected communication availability time period. The corrected communication availability time period is the time period during which the airborne radio station 160 transmits information to the ground terminal station 180 as broadcast information.

[0052] For example, as shown in the first line, the corrected communication-enabled time zone 20-1, calculated based on the orbital information on the day of data transmission, is from 10:10 to 10:20. However, as mentioned above, it is considered unnecessary to correct the communication-enabled time zone, so the corrected communication-enabled time zone 20-1 will be the same as the communication-enabled time zone 10-1.

[0053] Furthermore, as shown in the second line, the corrected communication time zone 20-2, calculated based on orbital information from three days prior, is from 10:10 to 10:20. Similarly, as shown in the third line, the corrected communication time zone 20-3, calculated based on orbital information from six days prior, is from 10:10 to 10:20. Thus, the corrected communication time zones 20-2 and 20-3 are the same as the communication time zone 10-1.

[0054] Figure 4 is a diagram showing the communication-enabled time period according to Embodiment 1 of this disclosure. The horizontal axis represents time.

[0055] The upper part of Figure 4 shows the communication-enabled time period 10-1 calculated based on the orbital information on the day of data transmission. The communication-enabled time period 10-1 is considered to be the value closest to the communication-enabled time period at the timing of data transmission from the ground terminal station 180 to the airborne radio station 160. Therefore, the control station 170 will perform a process to correct the communication-enabled time period to bring it closer to the communication-enabled time period 10-1.

[0056] The middle section of Figure 4 shows the communication-enabled time period 10-2 calculated based on orbital information from three days prior, and the corrected communication-enabled time period 20-2 corrected based on orbital information from three days prior. The communication-enabled time period 10-2 is the communication-enabled time period stored in the first ground terminal station 180. When the first ground terminal station 180 performs data transmission processing based on the communication-enabled time period 10-2, a problem arises in the occurrence of a non-communication time period 30-2, which is a period during which communication is impossible.

[0057] Therefore, the control station 170 transmits the corrected communication-enabled time period 20-2, which is obtained by correcting the communication-enabled time period 10-2, to the beacon. The first ground terminal station 180 can reduce the non-communication time period 30-2 by performing data transmission processing based on the corrected communication-enabled time period 20-2.

[0058] The lower part of Figure 4 shows the communication-enabled time period 10-3 calculated based on orbital information from six days prior, and the corrected communication-enabled time period 20-3 corrected based on orbital information from six days prior. The communication-enabled time period 10-3 is the communication-enabled time period stored in the second ground terminal station 180. When the second ground terminal station 180 performs data transmission processing based on the communication-enabled time period 10-3, a problem arises in the occurrence of a non-communication time period 30-3, which is a period during which communication is impossible.

[0059] Therefore, the control station 170 transmits the corrected communication-enabled time period 20-3, which is obtained by correcting the communication-enabled time period 10-3, to the beacon. The second ground terminal station 180 can reduce the non-communication time period 30-3 by performing data transmission processing based on the corrected communication-enabled time period 20-3.

[0060] It should be noted that there does not need to be multiple ground terminal stations 180; there may be just one. In this case as well, the ground terminal station 180 can reduce the non-communication time period 30 by performing data transmission processing based on the corrected communication-enabled time period 20, which is corrected based on the orbital information on the day the broadcast information was received.

[0061] The non-communication time zone 30 is a period within the corrected communication-enabled time zone 20 received by the first or second ground terminal station 180 via broadcast information that does not overlap with the communication-enabled time zone 10 calculated based on the orbital information on the day of data transmission. The non-communication time zone 30 means a period during which the first and second ground terminal stations 180 are transmitting data, but the airborne radio station 160 is unable to receive data.

[0062] Figure 5 is a flowchart illustrating the processes performed by the control station 170, beacon, airborne radio station 160, and ground terminal station 180 according to Embodiment 1 of this disclosure.

[0063] First, the control station 170 acquires orbital information from the upper-air radio station 160 (step S01). The acquired orbital information is stored along with the time the orbital information was generated. This orbital information may be stored in the memory device 173 or in the beacon.

[0064] Next, the control station 170 calculates the communication time period 10 for the airborne radio station 160 in a predetermined area based on the latest orbital information it has acquired (step S02).

[0065] Next, the control station 170 selects the orbital pattern of the upper-air radio station 160 (step S03). Next, the control station 170 corrects the communication available time period 10 (step S04). The control station 170 has previously obtained from the ground terminal station 180 the timing at which the ground terminal station 180, which is the communication target, performs data transmission processing. Therefore, the control station 170 can extract the variation time of the reception start time to be used for correction based on the orbital pattern selected in step S02, the timing of data transmission processing, and the generation time of the orbital information.

[0066] Next, the control station 170 notifies the beacon of the communication-enabled time period 10 and the corrected communication-enabled time period 20 (step S05). Next, the beacon stores the received communication-enabled time period 10 and the corrected communication-enabled time period 20 (step S06).

[0067] Next, the aerial radio station 160 transmits the corrected communication time period 20 as broadcast information (step S07). This transmission is achieved by the aerial radio station 160 transmitting the corrected communication time period 20, which it has acquired from the beacon, as broadcast information. This transmission also occurs when the communication time period 10 begins.

[0068] Next, the ground terminal station 180 receives the broadcast information (step S08). The ground terminal station 180 obtains the corrected communication available time period 20 from the broadcast information.

[0069] Next, the ground terminal station 180 transmits data (step S09). This data transmission occurs as the corrected communication time period 20 begins.

[0070] Next, the airborne radio station 160 receives the data transmitted from the ground terminal station 180 and terminates processing (step S10). As described above, the ground terminal station 180 can reduce the non-communication time period 30 by performing data transmission processing based on the corrected communication-enabled time period 20.

[0071] Figure 6 is a block diagram showing an example configuration of a control station 170 according to Embodiment 1 of the present disclosure.

[0072] The first communication circuit 171 connects to the airborne radio station 160 via a control line 6 and communicates with it. The second communication circuit 172 connects to the ground terminal station 180 located within a predetermined area via a line and communicates with it. The calculation circuit 174 acquires orbital information from the airborne radio station 160 via the first communication circuit 171 and stores it in the storage device 173. Based on the acquired orbital information, the calculation circuit 174 calculates the communication available time period 10 for the airborne radio station 160 within the predetermined area.

[0073] The calculation circuit 174 calculates the corrected communication-enabled time period 20 using a table and trajectory pattern information showing the time-dependent changes in the communication start time, which are separately stored in the memory device 173. The calculation circuit 174 also stores the calculated communication-enabled time period 10 and the corrected communication-enabled time period 20 in the memory device 173.

[0074] The calculation circuit 174 also notifies the beacon of the communication-enabled time period 10 and the corrected communication-enabled time period 20. The calculation circuit 174 may also directly notify the airborne radio station 160 of the communication-enabled time period 10 and the corrected communication-enabled time period 20 via the first communication circuit 171.

[0075] Figure 7 is a block diagram showing an example configuration of an airborne radio station 160 according to Embodiment 1 of this disclosure. Here, the case of a first-layer airborne radio station 110 is described, but the same applies to airborne radio stations 160 of other layers. The intra-layer communication circuit 161 connects to a nearby first-layer airborne radio station 110 via an intra-layer line 2 for communication. The base station communication circuit 162 connects to a ground base station 140 via an inter-base station line 5 for communication. The ground station communication circuit 163 connects to a ground terminal station 180 via an inter-ground station line 1 for communication. Note that there may be multiple inter-base station lines 5 and inter-ground station lines 1, and MIMO wireless communication (Multiple-Input and Multiple-Output) may be used. The inter-network communication circuit 166 connects to an airborne radio station 160 of another layer located in its vicinity via an inter-network line 3 for communication. The control station communication circuit 167 connects to a control station 170 via a control line 6 for communication.

[0076] The control circuit 165 generates a broadcast signal containing information on the communication-enabled time period 10 and the corrected communication-enabled time period 20, which is obtained from the control station 170 or a beacon. Furthermore, the control circuit 165 causes the ground station communication circuit 163 to transmit a broadcast signal as the communication-enabled time period 10 begins. The broadcast signal may be transmitted via a control line (not shown) different from the ground station inter-station line 1, or by other means.

[0077] Figure 8 is a block diagram showing an example configuration of a ground terminal station 180 according to Embodiment 1 of the present disclosure. The control circuit 182 instructs the communication circuit 181 to wait for a broadcast signal from the airborne radio station 160 as the latest available communication time period 10 stored in the storage device 183 begins. The control circuit 182 also updates the information on the available communication time period 10 and the latest corrected available communication time period 20 stored in the storage device 183 with the information on the latest available communication time period 10 and the latest corrected available communication time period 20 included in the broadcast signal received by the communication circuit 181.

[0078] Furthermore, when the latest corrected communication-enabled time period 20, newly updated in the storage device 183, begins, the control circuit 182 sends an instruction to the communication circuit 181 to transmit data to the airborne radio station 160. The communication circuit 181 receives the broadcast signal from the airborne radio station 160 via the ground station inter-station line 1 or an unshown control line, etc. The transmission data generation circuit 184 generates the data to be transmitted and sends it to the communication circuit 181.

[0079] The processes performed by the control station 170, the airborne radio station 160, and the ground terminal station 180 described above may be executed by a program using a computer equipped with a CPU and memory, in which the wireless communication program is stored. Alternatively, the processes may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The wireless communication program may be provided by recording it on a storage medium, or it may be provided via a network.

[0080] Figure 9 is a diagram showing the hardware configuration of the control station 170 according to Embodiment 1 of the present disclosure.

[0081] The control station 170 has an input unit 70, an output unit 71, a communication unit 72, a CPU (Central Processing Unit, also called a processor) 73, a memory 74, and an HDD (Hard Disk Drive) 75 connected via a bus 76, and functions as a computer. The control station 170 is also configured to input and output data to and from a storage medium 77 that can be read by a computer.

[0082] The input unit 70 is, for example, a keyboard and mouse. The output unit 71 is, for example, a display device such as a display. The communication unit 72 is, for example, a communication interface for communicating with an airborne radio station 160 and a ground terminal station 180.

[0083] Memory 74 refers to volatile or non-volatile semiconductor memory such as RAM, ROM, and flash memory, as well as magnetic disks, flexible disks, optical disks, and DVDs.

[0084] Memory 74 and HDD 75 are the aforementioned storage devices 173 that store data such as wireless communication programs, acquired orbital information, and calculated communication availability time information. The CPU 73 controls each part that constitutes the control station 170. The CPU 73 reads the wireless communication program stored in memory 74 or HDD 75 and executes predetermined processes, including the processes described in the flowchart of Figure 5.

[0085] The storage medium 77 is capable of storing wireless communication programs and the like that which execute the functions of the control station 170. The storage medium 77 is a USB (Universal Serial Bus) memory, a CD-ROM (Compact Disc Read Only Memory), etc.

[0086] Note that the architecture comprising the control station 170 is not limited to the example shown in the figure.

[0087] Figure 10 shows the hardware configuration of an airborne radio station 160 according to Embodiment 1 of the present disclosure. The airborne radio station 160 has an input unit 60, an output unit 61, a communication unit 62, a CPU 63, a memory 64, and an HDD 65 connected via a bus 66, and is equipped with computer functions. The airborne radio station 160 is also configured to input and output data to and from a storage medium 67 that can be read by a computer.

[0088] The explanation of the input unit 60 and output unit 61 is the same as in the case of the control station 170 described above, so the explanation will be omitted. The communication unit 62 is a communication interface that communicates with other airborne radio stations 160, control stations 170, or ground terminal stations 180, for example.

[0089] Memory 64 and HDD 65 are storage devices that store, for example, a wireless communication program, generated orbital information data, and information on the corrected communication time period 20. The CPU 63 controls each part that constitutes the airborne radio station 160. The CPU 63 reads the wireless communication program stored in memory 64 or HDD 65 and executes predetermined processing, including the processing described in the flowchart of Figure 5.

[0090] The explanation of the storage medium 67 is the same as in the case of the control station 170 described above, so the explanation will be omitted. Note that the architecture constituting the airborne radio station 160 is not limited to the example shown in the figure.

[0091] Figure 11 shows the hardware configuration of a ground terminal station 180 according to Embodiment 1 of the present disclosure. The ground terminal station 180 has an input unit 80, an output unit 81, a communication unit 82, a CPU 83, a memory 84, and an HDD 85 connected via a bus 86, and is equipped with computer functions. The ground terminal station 180 is also configured to input and output data to and from a storage medium 87 that can be read by a computer.

[0092] The explanation of the input unit 80 and output unit 81 is the same as in the case of the control station 170 described above, so the explanation will be omitted. The communication unit 82 is a communication interface that communicates with, for example, the airborne radio station 160 and the control station 170.

[0093] Memory 84 and HDD 85 are the aforementioned storage devices 183 that store, for example, a wireless communication program and information on the corrected communication-enabled time period 20 included in the broadcast signal from the airborne radio station 160. The CPU 83 controls each part that constitutes the ground terminal station 180. The CPU 83 reads the wireless communication program stored in memory 84 or HDD 85 and executes predetermined processing, including the processing described in the flowchart of Figure 5.

[0094] The explanation of the storage medium 87 is the same as in the case of the control station 170 described above, so the explanation will be omitted. Note that the architecture constituting the ground terminal station 180 is not limited to the example shown in the figure.

[0095] As described above, the wireless communication system 100 of this disclosure corrects the communication-enabled time period 10 according to a table showing the time-dependent changes in the communication start time of the airborne radio station 160, the orbital pattern of the airborne radio station 160, and the timing of data transmission by the ground terminal station 180. The ground terminal station 180 transmits data as the corrected communication-enabled time period begins. As a result, even if time has elapsed since the time the communication-enabled time period was calculated, the time period during which the ground base station is unable to communicate with the airborne radio station can be reduced.

[0096] <Modification> The process described in the flowchart of Figure 5 as being performed by the control station 170 does not necessarily have to be performed by the control station 170. In other words, it may be performed by at least one of the airborne radio station 160 or the ground terminal station 180.

[0097] Alternatively, the process described in the flowchart of Figure 5 as being performed by the control station 170 may be performed by the ground base station 140. In this case, the ground base station 140 calculates the latest available communication time period 10 and the latest corrected available communication time period 20 of the airborne radio station 160 in a predetermined area. The ground base station 140 also notifies the airborne radio station 160 of the corrected available communication time period 20 information via a non-terrestrial network or the like. This achieves the same effect as described above.

[0098] 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 the combined effects can be obtained in such cases.

[0099] 10 Communication available time slots 10-1 Communication available time slots 10-2 Communication available time slots 10-3 Communication available time slots 20 Corrected communication available time slots 20-1 Corrected communication available time slots 20-2 Corrected communication available time slots 20-3 Corrected communication available time slots 100 Wireless communication system 160 Airborne radio station 170 Control station 180 Ground terminal station

Claims

1. A wireless communication system comprising: one or more ground terminal stations located in a predetermined area; and an aerial radio station moving in an orbit above the air and periodically enabling communication with the predetermined area, wherein the system is configured to perform: a process for acquiring or generating the time-dependent change in the communication start time of the aerial radio station for each orbital pattern of the aerial radio station; a process for calculating the communication-enabled time period of the aerial radio station in the predetermined area based on the orbital information of the aerial radio station; and a process for correcting the calculated communication-enabled time period according to the time-dependent change, the orbital pattern, and the timing of data transmission by the ground terminal station, wherein the ground terminal station is configured to perform: a process for acquiring the corrected communication-enabled time period; and a process for transmitting data as the corrected communication-enabled time period begins.

2. A wireless communication method to be implemented by a wireless communication system comprising: one or more ground terminal stations located in a predetermined area; and an aerial radio station moving in an orbit above the air and periodically enabling communication with the predetermined area, the method comprising: acquiring or generating the time-dependent change in the communication start time of the aerial radio station for each orbital pattern of the aerial radio station; calculating the communication-enabled time period of the aerial radio station in the predetermined area based on the orbital information of the aerial radio station; correcting the calculated communication-enabled time period according to the time-dependent change, the orbital pattern, and the timing of data transmission by the ground terminal station; and transmitting data as the corrected communication-enabled time period begins.

3. A control station having one or more ground terminal stations located in a predetermined area, wherein for an aerial radio station that moves in an orbit above the air and is periodically able to communicate with the predetermined area, the control station is configured to perform the following processes: acquiring or generating the time-dependent change in the communication start time of the aerial radio station for each orbital pattern of the aerial radio station; calculating the time period during which the aerial radio station is able to communicate in the predetermined area based on the orbital information of the aerial radio station; correcting the calculated time period of communication in accordance with the time-dependent change, the orbital pattern, and the timing at which the ground terminal station transmits data; and notifying the aerial radio station of the corrected time period of communication.

4. A wireless communication program to be executed by a control station having a processor and memory and having one or more ground terminal stations located in a predetermined area under its command, the program being stored in the memory and computer-readable, and including a program to cause the processor to execute: a process for acquiring or generating the time-dependent change in the communication start time of an airborne radio station for each airborne radio station's orbital pattern, for each airborne radio station that moves in an orbit above the air and is periodically able to communicate with the predetermined area; a process for calculating the time period during which the airborne radio station is able to communicate in the predetermined area based on the airborne radio station's orbital information; a process for correcting the calculated time period during which the airborne radio station is able to communicate according to the time-dependent change, the orbital pattern, and the timing at which the ground terminal station transmits data; and a process for notifying the airborne radio station of the corrected time period during which it can communicate.

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