Communication relay device, remote control device, system, antenna control method and program

Abstract

Provided is an aerial relay type communication relay device that can maximize service area coverage and communication capacity even in an environment where the aircraft moves at high speed or its attitude changes. [Solution] A communication relay device forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the sky, and wirelessly communicates with a plurality of terminal devices present in the cells. The communication relay device optimizes antenna parameters of the service link antenna based on information on the positions of the plurality of terminal devices so as to form the cells in accordance with the distribution of the plurality of terminal devices in the service area, and controls the direction of the beam formed by the antenna or the main directivity direction of the antenna based on information on at least one of the position and attitude of the aircraft so as to fix the position of the footprint of the cell in the service area.

Description

[Technical field]

[0001] The present invention relates to optimization of a service area made up of cells formed by an airborne relay type (airborne type) communication relay device toward the ground or sea. [Background technology]

[0002] Conventionally, there has been known a method of area optimization in which antenna parameters of a service link (e.g., the direction and width of the beam for forming a cell) are optimized so as to obtain a desired communication quality (e.g., throughput) throughout a service area (hereinafter, simply referred to as an "area") formed on the ground by a communication relay device such as a High Altitude Platform Station (HAPS) (also referred to as a "High Altitude Pseudo Satellite") that can remain afloat in the air (see Patent Documents 1 to 3 and Non-Patent Documents 1 to 6).

[0003] For example, Non-Patent Document 1 discloses a method of area optimization assuming that the distribution of user equipment (hereinafter also referred to as "UE") as terminal devices in an area is uniform. Also, Non-Patent Document 2 discloses a method of performing optimization for each cell so that a desired communication quality (e.g., throughput) is obtained in the entire area when the area is composed of multiple cells. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-161734 A [Patent Document 2] JP 2022-161742 A [Patent Document 3] Patent No. 7318047 [Non-patent literature]

[0005] [Non-Patent Document 1] Y. Shibata, N. Kanazawa, M. Konishi, K. Hoshino, Y. Ohta and A. Nagate, "System Design of Gigabit HAPS Mobile Communications," in IEEE Access, vol. 8, pp. 157995-158007, 2020. [Non-Patent Document 2] Yohei Shibata, Wataru Takabatake, Kenji Hoshino, and Atsushi Nagate, "HAPS Dynamic Cell Control Algorithm Considering User Distribution in Multi-Cell Configurations," IEICE Technical Report, vol. 120, no. 322, RCS2020-185, pp. 170-175, January 2021. [Non-Patent Document 3] Shaoshuai Fan, Hui Tian1 and Cigdem Sengul, "Self-optimization of coverage and capacity based on a fuzzy neural network with cooperative reinforcement learning", EURASIP Journal on Wireless Communications and Networking 2014. [Non-Patent Document 4] Rubayet Shafin, Hao Chen, Young Han Nam, Sooyoung Hur, Jeongho Park, Jianzhong (Charlie) Zhang, Jeffrey Reed, and Lingjia Liu "Self-Tuning Sectorization: Deep Reinforcement Learning Meets Broadcast Beam Optimization", IEEE Transactions on Wireless Communications, 2020. [Non-Patent Document 5] Eren Balevi and Jeffrey G. Andrews ,"A Novel Deep Reinforcement Learning Algorithm for Online Antenna Tuning", in Proc. IEEE Global Communications Conference (GLOBECOM), 2019. [Non-Patent Document 6] Yohei Shibata, Wataru Takabatake, Kenji Hoshino, Atsushi Nagate and Tomoaki Ohtsuki, "Two-Step Dynamic Cell Optimization Algorithm for HAPS Mobile Communications", IEEE Access, vol. 10, pp.68085-68098, 2022. Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional area optimization methods, it takes time to obtain the user distribution (distribution of terminal devices) in a service area and to perform calculations for area optimization. Therefore, when a platform (communication relay device) such as HAPS in the sky moves, turns, or changes its attitude at high speed, the user distribution (distribution of terminal devices) seen from the aircraft moves or rotates at high speed, and the process of optimizing antenna parameters for forming cells that cover the service area cannot be completed in time, which may prevent the coverage and communication capacity of the service area from being maximized. [Means for solving the problem]

[0007] A communication relay device according to one aspect of the present invention is an airborne relay-type communication relay device that forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air, and wirelessly communicates with a plurality of terminal devices present in the cells. This communication relay device includes an area optimization control unit that performs area optimization control to optimize antenna parameters of the service link antenna so as to form the cells in accordance with the distribution of the plurality of terminal devices in the service area, based on information on the positions of the plurality of terminal devices, and a footprint fixing control unit that performs footprint fixing control to control the direction of the beam formed by the service link antenna or the directivity direction of the service link antenna, based on information on at least one of the position and attitude of the aircraft, so as to fix the position of the footprint of the cell in the service area.

[0008] A remote control device according to another aspect of the present invention is a remote control device capable of communicating with an airborne relay-type communication relay device that forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air and wirelessly communicates with a plurality of terminal devices present in the cells. This remote control device includes an area optimization control unit that executes area optimization control to optimize antenna parameters of the service link antenna so as to form the cells in accordance with the distribution of the plurality of terminal devices in the service area based on information on the positions of the plurality of terminal devices, and a footprint fixing control unit that executes footprint fixing control to control the direction of the beam formed by the service link antenna or the directivity direction of the service link antenna so as to fix the position of the footprint of the cell in the service area based on information on at least one of the position and attitude of the aircraft.

[0009] In the communication relay device and the remote control device, the area optimization control unit may estimate positions of the multiple terminal devices in the service area, optimize antenna parameters of the service link antenna based on the estimated positions of the multiple terminal devices, and apply to the service link antenna an optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value based on an initial value of the antenna parameter.

[0010] In the communication relay device and the remote control device, the service link antenna may be a beamforming controllable array antenna having a plurality of antenna elements, and the antenna parameters to be optimized may include a horizontal beam direction, a vertical beam direction, and a beam width of a beam formed from the service link antenna toward the cell. Here, the area optimization control unit may calculate a plurality of antenna weights corresponding to the plurality of antenna elements based on the optimal values ​​of the antenna parameters, and apply the plurality of antenna weights to a plurality of signals transmitted and received by the plurality of antenna elements.

[0011] In the communication relay device and the remote control device, the antenna parameters to be optimized may include a horizontal beam direction and a vertical beam direction of a beam formed from the service link antenna toward the cell, and the area optimization control unit may drive and control the service link antenna so as to change the directional direction of the service link antenna based on the optimal values ​​of the antenna parameters.

[0012] In the communication relay device and the remote control device, the area optimization control may be performed at a fixed or variable interval, and the footprint fixing control may be performed more frequently or continuously than the area optimization control.

[0013] The communication relay device and the remote control device may each include a memory unit, and the area optimization control unit may estimate positions of the multiple terminal devices in the service area, optimize antenna parameters of the service link antenna based on the estimated positions of the multiple terminal devices, and store in the memory unit an optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value based on an initial value of the antenna parameter, and the footprint fixation control unit may control a direction of the beam formed by the service link antenna or a directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on information on at least one of the position and attitude of the aircraft and the optimal value of the antenna parameter or the offset value stored in the memory unit.

[0014] In the communication relay device and the remote control device, the service link antenna may be a beamforming controllable array antenna having a plurality of antenna elements, and the antenna parameters to be optimized may include a horizontal beam direction, a vertical beam direction, and a beam width of a beam formed from the service link antenna toward the cell. Here, the footprint fixing control unit may calculate a steering direction of the beam formed from the service link antenna toward the cell based on at least one of information on the position and attitude of the aircraft, calculate a plurality of antenna weights corresponding to the plurality of antenna elements based on the calculation result of the steering direction of the beam and the optimal value or the offset value of the antenna parameter stored in the storage unit, and apply the plurality of antenna weights to a plurality of signals transmitted and received by the plurality of antenna elements.

[0015] In the communication relay device and the remote control device, the antenna parameters to be optimized may include a horizontal beam direction and a vertical beam direction of a beam formed from the service link antenna toward the cell, wherein the footprint fixing control unit may calculate a steering direction of the beam formed from the service link antenna toward the cell based on at least one of information on the position and attitude of the aircraft, and drive and control the service link antenna to change the directivity direction of the service link antenna based on the calculation result of the steering direction of the beam and the optimal value or the offset value of the antenna parameter stored in the storage unit.

[0016] In the communication relay device and the remote control device, the relay communication station mounted on the aircraft may be a repeater-type relay communication station that relays transmitted and received signals without regenerating them, or it may be a base station-type relay communication station having a base station device that regenerates transmitted and received signals and re-modulates the regenerated signals before relaying them.

[0017] A system according to yet another aspect of the present invention includes any of the remote control devices described above, and an airborne relay-type communication relay device that forms one or more cells toward a service area on the ground or sea via a service link antenna of a relay communication station installed on an aircraft located in the air, and wirelessly communicates with multiple terminal devices located in the cells.

[0018] A method according to yet another aspect of the present invention is an antenna control method for forming one or more cells toward a terrestrial or marine service area via a service link antenna of a relay communication station provided on an aircraft located in the sky, the antenna control method including: executing area optimization control for optimizing antenna parameters of the service link antenna so as to form the cells in accordance with a distribution of the plurality of terminal devices in the service area, based on information on positions of the plurality of terminal devices; and executing footprint fixing control for controlling a direction of a beam formed by the service link antenna or a directivity direction of the service link antenna, based on information on at least one of a position and an attitude of the aircraft, so as to fix a position of a footprint of the cell in the service area.

[0019] The antenna control method may include estimating positions of the plurality of terminal devices in the service area, optimizing antenna parameters of the service link antenna based on the estimated positions of the plurality of terminal devices, and applying the optimal values ​​of the antenna parameters after the optimization is completed to the service link antenna.

[0020] The antenna control method may include performing the area optimization control at a fixed or variable frequency, and performing the footprint fixed control more frequently or continuously than the area optimization control.

[0021] The antenna control method may include estimating positions of the plurality of terminal devices in the service area, optimizing antenna parameters of the service link antenna based on the estimated positions of the plurality of terminal devices, storing optimal values ​​of the antenna parameters after the optimization is completed or an offset value of the optimal values ​​based on initial values ​​of the antenna parameters, and controlling a direction of a beam formed by the service link antenna or a directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on information on at least one of a position and attitude of the aircraft and the stored optimal values ​​of the antenna parameters or the offset value.

[0022] In the antenna control method, the service link antenna may be a beamforming controllable array antenna having a plurality of antenna elements, and the antenna parameters to be optimized may include a horizontal beam direction, a vertical beam direction, and a beam width of a beam formed from the service link antenna toward the cell. Here, the antenna parameter control method may include calculating a plurality of antenna weights corresponding to the plurality of antenna elements based on optimal values ​​of the antenna parameters, and applying the plurality of antenna weights to a plurality of signals transmitted and received by the plurality of antenna elements.

[0023] In the antenna control method, the antenna parameters to be optimized may include a horizontal beam direction and a vertical beam direction of a beam formed from the service link antenna toward the cell, and the antenna control method may include driving and controlling the service link antenna so as to change a directivity direction of the service link antenna based on the optimal values ​​of the antenna parameters.

[0024] A program according to yet another aspect of the present invention is a program executed by a computer or processor provided in an airborne relay-type communication relay device that forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air and wirelessly communicates with a plurality of terminal devices present in the cells. This program includes: program code for optimizing antenna parameters of the service link antenna so as to form the cells in accordance with the distribution of the plurality of terminal devices in the service area based on information on positions of the plurality of terminal devices; and program code for executing footprint fixing control that controls the direction of a beam formed by the service link antenna or the directivity direction of the service link antenna so as to fix the position of the footprint of the cell in the service area based on information on at least one of the position and attitude of the aircraft.

[0025] A program according to yet another aspect of the present invention is a program executed by a computer or processor provided in a remote control device capable of communicating with an airborne relay-type communication relay device that forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air and wirelessly communicates with a plurality of terminal devices present in the cells. This program includes: a program code for executing area optimization control that optimizes antenna parameters of the service link antenna so as to form the cells in accordance with the distribution of the plurality of terminal devices in the service area based on information on the positions of the plurality of terminal devices; and a program code for executing footprint fixing control that controls the direction of a beam formed by the service link antenna or the directivity direction of the service link antenna so as to fix the position of the footprint of the cell in the service area based on information on at least one of the position and attitude of the aircraft.

[0026] The program may include program code for estimating positions of the plurality of terminal devices in the service area, program code for optimizing antenna parameters of the service link antenna based on the estimation results of the positions of the plurality of terminal devices, and program code for applying optimal values ​​of the antenna parameters after the optimization is completed to the service link antenna.

[0027] In the program, the service link antenna may be a beamforming controllable array antenna having a plurality of antenna elements, and the antenna parameters to be optimized may include a horizontal beam direction, a vertical beam direction, and a beam width of a beam formed from the service link antenna toward the cell. Here, the program may include a program code for calculating a plurality of antenna weights corresponding to the plurality of antenna elements based on optimal values ​​of the antenna parameters, and a program code for applying the plurality of antenna weights to a plurality of signals transmitted and received by the plurality of antenna elements.

[0028] In the program, the antenna parameters to be optimized may include a horizontal beam direction and a vertical beam direction of a beam formed from the service link antenna toward the cell, and the program may include program code for driving and controlling the service link antenna so as to change the directional direction of the service link antenna based on optimal values ​​of the antenna parameters.

[0029] The program may include program code for executing the area optimization control at a fixed or variable interval frequency, and program code for executing the footprint fixing control more frequently or continuously than the area optimization control.

[0030] The program may include: program code for estimating positions of the plurality of terminal devices in the service area; program code for optimizing antenna parameters of the service link antenna based on the estimation results of the positions of the plurality of terminal devices; program code for storing an optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value based on an initial value of the antenna parameter; and program code for controlling a direction of a beam formed by the service link antenna or a directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on information on at least one of a position and attitude of the aircraft and the optimal value of the antenna parameter or the offset value stored in the memory unit.

[0031] In the program, the service link antenna may be a beamforming controllable array antenna having a plurality of antenna elements, and the antenna parameters to be optimized may include a horizontal beam direction, a vertical beam direction, and a beam width of a beam formed from the service link antenna toward the cell. Here, the program may include: a program code for calculating a steering direction of a beam formed from the service link antenna toward the cell based on at least one of information on a position and an attitude of the aircraft, a program code for calculating a plurality of antenna weights corresponding to the plurality of antenna elements based on a calculation result of the steering direction of the beam and an optimal value or the offset value of the antenna parameter stored in the storage unit, and a program code for applying the plurality of antenna weights to a plurality of signals transmitted and received by the plurality of antenna elements.

[0032] In the program, the antenna parameters to be optimized may include a horizontal beam direction and a vertical beam direction of a beam formed from the service link antenna toward the cell. Here, the program may include: a program code for calculating a steering direction of a beam formed from the service link antenna toward the cell based on at least one of information on a position and an attitude of the aircraft; and a program code for driving and controlling the service link antenna to change a directivity direction of the service link antenna based on a calculation result of the steering direction of the beam and the optimal value or the offset value of the antenna parameter stored in the storage unit.

[0033] All or a part of the program may include a trained model created by machine learning. Effect of the Invention

[0034] According to the present invention, it is possible to maximize the coverage of a service area and communication capacity even in an environment in which the airborne relay type communication relay device's airframe moves, rotates, or changes in attitude at high speed. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of the overall configuration of a communication system according to an embodiment. [Diagram 2] Fig. 2(a) is an explanatory diagram showing an example of the layout and size of cells before applying area optimization control for each cell in a service area consisting of seven cells, and Fig. 2(b) is an explanatory diagram showing an example of the layout and size of cells after applying the area optimization control. [Diagram 3] FIG. 3 is an explanatory diagram showing an example of an antenna tilt angle, a horizontal half width, and a vertical half width as antenna parameters used in the area optimization control. [Figure 4] FIG. 4 is a flowchart showing an example of an area optimization control algorithm according to a reference example. [Diagram 5] Fig. 5(a) is an explanatory diagram showing an example of cell arrangement in a service area consisting of seven cells before applying FP locking control, and Fig. 5(b) is an explanatory diagram showing an example of cell arrangement after applying the same FP locking control. [Figure 6] FIG. 6 is a diagram illustrating an example of a combination of area optimization control and FP fixing control in the control system according to the embodiment. [Figure 7] FIG. 7 is an explanatory diagram showing an example of changes in cell placement and size by combining area optimization control and FP fixing control when taking into account the yaw rotation of the communication relay device (HAPS) according to the embodiment. [Figure 8] FIG. 8 is a flowchart showing an example of overall control including area optimization control and FP fixing control according to the embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of the FP fixing control in the overall control of FIG. [Figure 10] FIG. 10 is a flowchart showing an example of area optimization control in the overall control of FIG. [Figure 11] FIG. 11 is a flowchart showing another example of the overall control including the area optimization control and the FP fixing control according to the embodiment. [Figure 12] FIG. 12 is an explanatory diagram illustrating an example of a device configuration of a control system according to an embodiment. [Figure 13] FIG. 13 is an explanatory diagram showing another example of the device configuration of the control system according to the embodiment. [Figure 14] FIG. 14 is an explanatory diagram showing yet another example of the device configuration of the control system according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The system according to the embodiment described in this specification is a communications system that includes a control system that uses footprint fixing control (hereinafter also referred to as "FP fixing control") to fix the footprints of multiple cells in a service area formed from an airborne relay-type communications relay device (HAPS) as an airborne platform toward the ground or sea, thereby compensating for movement and rotation of cells as seen from the aircraft due to high-speed movement, rotation, or attitude changes of the communications relay device, and that uses area optimization control to optimize antenna parameters for forming cells that cover the service area, thereby maximizing the coverage and communication capacity of the service area even in an environment where high-speed movement, rotation, or attitude changes of the aircraft occur. In particular, the system according to this embodiment is a communications system including a control system that shares antenna parameters used for each control between FP fixing control and area optimization control via a storage device such as a memory, executes area optimization control, which requires more time for processing, at a lower frequency than FP fixing control, stores the optimum values ​​of the antenna parameters or their offset values ​​obtained by the area optimization control, and executes FP fixing control to fix cells to be formed toward a service area more frequently or continuously than the area optimization control, while referring to the optimum values ​​of the antenna parameters or their offset values ​​stored by executing the area optimization control.

[0037] 1 is an explanatory diagram showing an example of the overall configuration of a communication system according to an embodiment. The communication system according to this embodiment is suitable for realizing a three-dimensional network of fifth-generation or subsequent generations of mobile communication that supports simultaneous connection to a large number of terminal devices (hereinafter referred to as "UE") 61 and low latency. Furthermore, mobile communication standards applicable to the communication system, radio relay station, base station, repeater, and UE disclosed in this specification include fifth-generation mobile communication standards and next-generation mobile communication standards after the fifth generation.

[0038] As shown in Fig. 1, the communication system includes a high altitude platform station (HAPS) (also called a "high altitude pseudo satellite" or "stratospheric platform") 10 as an airborne relay type communication relay device (wireless relay device) constituting an airborne platform. The HAPS 10 is an airborne or levitating type communication relay device that is located in an airspace at a predetermined altitude and forms a three-dimensional cell (three-dimensional area) in a cell formation target airspace at the predetermined altitude toward a target service area 20A.

[0039] HAPS10 is an air vehicle or floating body fuselage 100 that is controlled to float or fly in a high altitude airspace (floating airspace) at 100 km or less above ground or sea level by autonomous control or external control, and is equipped with a relay communication station 110. The airspace in which HAPS10 is located may be, for example, a stratospheric airspace with an altitude H of 18 km or more and 50 km or less. This airspace may be an airspace with an altitude of 15 km or more and 25 km or less where the weather conditions are relatively stable, and may particularly be an airspace with an altitude of approximately 20 km.

[0040] The cell formation target airspace, which is the target airspace in which a three-dimensional cell is to be formed by HAPS10, may be an airspace within a predetermined altitude range (e.g., an altitude range of 50 m or more and 1,000 m or less) located between the airspace in which HAPS10 is located and a cell formation area near the ground covered by a base station such as a conventional macrocell base station (e.g., an LTE eNodeB or a next-generation gNodeB).

[0041] The cell formation target airspace may be above an ocean, a river, or a lake. The three-dimensional cell formed by HAPS 10 may also be formed to reach the ground or sea surface so that communication can be performed with UE 61 located on the ground or sea.

[0042] The HAPS10 wirelessly communicates with the UE61 via a service link antenna (also referred to as an "SL antenna") 111 of a relay communication station 110 provided on an aircraft 100 such as an aircraft or a floating body located in the sky. The HAPS10 is equipped with at least one of a battery and a solar power generation system, for example, and can fly using electric power. The HAPS10 may be an airship-type HAPS, in addition to the solar plane-type HAPS shown in the figure. The HAPS10 provided with the relay communication station 110 may be an artificial satellite (for example, a communication satellite), a balloon, or an unmanned aerial vehicle (UAV) such as a drone or an unmanned aircraft system (UAS). The HAPS10 may fly using at least one of a battery and an engine as a power source. The UAV may be, for example, an unmanned aerial vehicle that flies using fuel, or a drone that flies using a battery or the like.

[0043] The relay communication station 110 includes a service link antenna (SL antenna) 111 and a feeder link antenna (hereinafter also referred to as an "FL antenna") 112. The relay communication station 110 can perform service link SL communication with the UE 61 via the SL antenna 111. The SL antenna 111 is, for example, a beamforming controllable array antenna capable of controlling the direction and width of each of a plurality of beams that form a plurality of cells 20C(1) to 20C(7) in the target service area 20A. The areas through which the beams pass in the cell formation target airspace are the three-dimensional cells 20C(1) to 20C(7). The adjacent beams in the cell formation target airspace may partially overlap each other. Also, the plurality of communication areas where the plurality of cells 20C(1) to 20C(7) reach the ground (or sea, etc.) are the footprints 20F(1) to 20F(7).

[0044] In the illustrated example, seven cells 20C(1) to 20C(7) are formed via the SL antenna 111, but the number of cells 20C may be one, two to six, or eight or more.

[0045] The SL antenna 111 is, for example, a single or multiple array antennas in which multiple antenna elements are arranged two-dimensionally or three-dimensionally and capable of forming multiple beams toward the ground. The SL antenna 111 may be a massive antenna in which many antenna elements are arranged two-dimensionally and capable of controlling beam directivity in the horizontal and vertical directions.

[0046] The relay communication station 110 can perform communication of the feeder link FL with a gateway device (also called a "feeder station"; hereinafter, called a "GW station") 70 for HAPS installed on land (or on the sea, etc.) via the FL antenna 112. The FL antenna 112 is, for example, an array antenna capable of controlling directivity (direction of a directional beam). The FL antenna 112 is, for example, a single or multiple array antennas in which multiple antenna elements are arranged two-dimensionally or three-dimensionally. The FL antenna 112 may be a massive antenna in which multiple antenna elements are arranged two-dimensionally and capable of controlling directivity in the horizontal and vertical directions. The feeder link FL (F) in the figure is a forward link from the GW station 70 to the UE 61 via the HAPS 10, and the feeder link FL (R) is a reverse link from the UE 61 to the GW station 70 via the HAPS 10.

[0047] The relay communication station 110 mounted on the aircraft 100 of HAPS10 may be a repeater-type relay communication station that relays transmitted and received signals without regenerating them, or may be a base station-type relay communication station having a base station device that regenerates transmitted and received signals and re-modulates and relays the regenerated signals.

[0048] The repeater-type relay communication station 110 functions as a repeater slave corresponding to the repeater master consisting of the GW station 70, and is, for example, a wireless relay device (hereinafter also referred to as a "frequency conversion repeater") that converts the frequency of a feeder link having a different frequency from that of a service link. In the downlink, the relay communication station 110 converts the frequency of the feeder link transmitted from the base station device 80 via the GW station 70 to the frequency of the service link, and transmits it to the UE 61. On the other hand, in the uplink, the relay communication station 110 converts the frequency of the service link transmitted from the UE 61 to the frequency of the feeder link, and transmits it to the base station device 80 via the GW station 70.

[0049] The repeater-type relay communication station 110 includes, for example, a repeater and a frequency conversion device. The repeater includes, for example, a low noise amplifier that amplifies a service link SL reception signal received via the SL antenna 111, a power amplifier that amplifies a service link SL transmission signal transmitted via the SL antenna 111, and the like. The frequency conversion device converts between the frequency of the service link SL and the frequency of the feeder link FL.

[0050] The base station type relay communication station 110 has a base station device and a frequency conversion device. The base station device has a baseband processing device that processes a baseband signal of a service link, a communication interface unit for communicating with a core network of the mobile communication network 90 via a backhaul line via the GW station 70, and the like. The frequency conversion device converts between the frequency of a service link signal input / output to / from the base station device in the relay communication station 110 and the frequency of a feeder link signal transmitted / received via the FL antenna 112.

[0051] In the embodiment described below, a case will be mainly described in which the relay communication station 110 mounted on the aircraft 100 of the HAPS 10 is a repeater-type relay communication station (repeater slave unit).

[0052] The UE (user equipment) 61 is a terminal device used by a user on land or sea. The UE 61 is, for example, a mobile phone, a smartphone, a portable personal computer having a mobile communication function, etc., and is also called a mobile terminal, a mobile station, a mobile device, or a portable communication terminal. The UE 61 may be a modular mobile station incorporated in a moving object such as a vehicle such as an automobile, or a drone that is an aircraft such as a small remotely controlled helicopter, or may be a terminal device of a device for IoT (Internet of Things).

[0053] HAPS10 may autonomously control its own levitation movement (flight) and the processing and control at the relay communication station 110 by executing a control program with a control unit configured with an internally built computer or processor, etc. For example, HAPS10 may autonomously perform area optimization control and FP fixing control, which will be described later. HAPS10 may also acquire its own current position information (e.g., GNSS (Global Navigation Satellite System) position information such as GPS position information), pre-stored position control information (e.g., flight schedule information), position information of other HAPS located in the vicinity, and autonomously control its levitation movement (flight) and the processing and control at the relay communication station 110 based on that information.

[0054] Information on the position and attitude of the HAPS 10 may be acquired based on the output of a GPS receiver, a gyro sensor, an acceleration sensor, an inertial sensor, and the like incorporated in the HAPS 10. For example, information on the position and attitude of the HAPS 10 may be acquired based on the output of a GNSS inertial navigation system (GNSS / INS) that combines a GNSS system and an inertial measurement unit (IMU) incorporated in the HAPS 10.

[0055] The levitation (flight) of HAPS 10 and the processing and control at relay communication station 110 may be controlled by a remote control device 95 provided in a communication center of mobile communication network 90 or the like. Remote control device 95 may be configured, for example, as a computer device such as a PC, a server, or the like. HAPS 10 may be incorporated with a control communication terminal device (e.g., a mobile communication module) so as to receive control information from the remote control device 95 and transmit various information such as monitoring information to the remote control device 95, and may be assigned terminal identification information (e.g., IP address, telephone number, etc.) so as to be identifiable by the remote control device 95. The MAC address of the communication interface may be used to identify the control communication terminal device.

[0056] The remote control device 95 may cooperate with the HAPS 10 to perform area optimization control and FP fixing control, which will be described later.

[0057] Furthermore, HAPS10 may transmit monitoring information, such as information relating to the floating movement (flight) of itself or surrounding HAPS and processing at the relay communication station 110, position information of HAPS10, information relating to the status of HAPS10, and observation data acquired by various sensors, to a predetermined destination such as the remote control device 95. The control information may include target flight route information of the HAPS. The monitoring information may include at least one of information on the current position of HAPS10, flight route history information, airspeed, ground speed, and thrust direction, wind speed and direction of air currents around HAPS10, and air pressure and temperature around HAPS10.

[0058] The duplexing method of the uplink and downlink of the wireless communication between the relay communication station 110 and the UE 61 is not limited to a specific method, and may be, for example, a time division duplex (TDD) method or a frequency division duplex (FDD) method. The access method of the wireless communication between the relay communication station 110 and the UE 61 is not limited to a specific method, and may be, for example, a frequency division multiple access (FDMA) method, a time division multiple access (TDMA) method, a code division multiple access (CDMA) method, or an orthogonal frequency division multiple access (OFDMA) method. The wireless communication may use a multi-input and multi-output (MIMO) technology that has functions such as diversity coding, transmission beamforming, and spatial division multiplexing (SDM) and can increase the transmission capacity per unit frequency by simultaneously using multiple antennas for both transmission and reception. Furthermore, the MIMO technology may be a single-user MIMO (SU-MIMO) technology in which one base station transmits multiple signals to one UE at the same time and frequency, or a multi-user MIMO (MU-MIMO) technology in which one base station transmits signals to multiple different UEs at the same time and frequency, or multiple different base stations transmit signals to one UE at the same time and frequency.

[0059] In the communication system configured as above, for example, a signal from a base station device 80 is relayed by the GW station 70 and the HAPS 10, and a communication service can be provided to a UE 61 on the ground. In particular, according to the communication system of this embodiment, the HAPS 10, which serves as an airborne relay type communication relay device functioning as an airborne platform, can provide an ultra-wide area mobile communication service directly to a UE (portable terminal) 61 on the ground from the stratosphere at an altitude of 18 km or more and 50 km or less (particularly about 20 km). In addition, an airborne platform consisting of the HAPS 10 is attracting attention as a new form of communication for use in large-scale disasters and the like.

[0060] In the communication system of this embodiment, area optimization is performed to optimize antenna parameters of the SL antenna 111 so as to obtain a desired communication quality (e.g., throughput) in the entire service area 20A consisting of multiple cells 20C(1)-20C(7) formed toward the ground by an airborne platform such as HAPS10. For example, in an airborne platform such as HAPS10 that covers the service area 20A with multiple cells 20C(1)-20C(7), area optimization control is performed to optimize the beam direction and width of each cell according to the population distribution (or user distribution, UE distribution, etc.).

[0061] For example, as shown in FIG. 2(a), when multiple cells 20C(1)-20C(7) of the same size are formed so as to be uniformly distributed in the service area 20A without applying the area optimization control, the coverage and communication capacity in the user (UE) dense area located on the left side of the service area 20A in the figure may be reduced. On the other hand, in FIG. 2(b), the area optimization control is applied to optimize the direction and width of the beam for each of the multiple cells 20C(1)-20C(7) based on big data such as the population distribution in the service area 20A. By applying the area optimization control in this way, the number of cells covering the user (UE) dense area located on the left side of the service area 20A is increased so as to cover the user (UE) dense area intensively, and the reduction in the communication capacity in the user (UE) dense area can be suppressed. This makes it possible to maximize the coverage and communication capacity in the service area 20A.

[0062] In the area optimization control, for example, in area optimization of an area consisting of N cells, the following four types of antenna parameters A to D are defined and used as multiple types of antenna parameters for an arbitrary i-th cell i within the area. A. Tilt angle θ tilt,i B. Vertical half width θ 3dB,i C. Horizontal half width φ 3dB,i D. Cell horizontal direction ω i

[0063] As shown in FIG. 3, the tilt angle θ tilt,i is the angle from the horizontal direction H of the vector Vc directed from the SL antenna 111 of the HAPS 10 toward the center of the i-th cell 20C(i) of interest. 3dB,i is a vertical plane P including a vector Vc pointing to the center of the i-th cell 20C(i). V Horizontal half-width φ is the angular width between two points where the beam gain is reduced by 3 dB from the maximum gain at the center of the main beam. 3dB,i is the horizontal plane P containing the vector Vc pointing to the center of the i-th cell 20C(i). HThis is the angular width between two points where the beam gain is reduced by 3 dB from the maximum gain at the center of the main beam.

[0064] Also, the horizontal direction of the i-th cell, ω i is the angle of the direction passing through the center of the target cell from a predetermined reference horizontal direction Hs on a horizontal plane including the position of the SL antenna 111 of HAPS 10 as the reference point.

[0065] Fig. 4 is a flowchart showing an example of an area optimization control algorithm according to a reference example (see Patent Document 1 mentioned above). In Fig. 4, the area optimization control includes a UE position estimation step (S110), a sequential area optimization step (S120), and a parameter application step (S130) of applying optimization parameters to the actual environment.

[0066] In the UE position estimation step (S110), the position of each UE 61 in the service area 20A is estimated by some method, and the estimation result (for example, coordinate data of the position of each UE 61) is output. The position of each UE 61 can be estimated by using, for example, GNSS position information or MR (measurement report) fed back from each UE 61.

[0067] Next, in the sequential area optimization step (S120), the estimation result of the position of each UE 61 (for example, coordinate data of the position of each UE 61) output in the UE position estimation step (S110) is input, and the optimal value of the antenna parameter of each cell optimized for each subarea is output. For example, the service area 20A in which N cells are formed is divided into M subareas, and each subarea is optimized in turn by the following procedure.

[0068] First, the service area 20A is divided into a plurality of (M) subareas so that the interdependence between the subareas is reduced (S121). Next, the contribution degree x i Depending on the granularity of each sub-area, f(x i ) (S122). Next, the above-determined granularity is set as f(x i), a predetermined number of antenna parameters are optimized by a genetic algorithm or the like (S123). Next, the antenna parameter values ​​for the entire service area 20A are updated with the optimized parameter values ​​(S123). Note that the above processes of S121 to S123 for all subareas may be repeated T times (T≧1).

[0069] In the parameter application step (S130), the final updated values ​​of the antenna parameters of each cell in the service area 20A after the completion of the sequential area optimization step (S120) are applied as control setting values ​​of the SL antenna 111 in the relay communication station 110 in the actual environment.

[0070] The area optimization control illustrated in FIG. 4 may be performed periodically (for example, periodically every hour or every two hours), or may be performed whenever there is a significant change in the UE distribution within the service area 20A (for example, when the change in the number of UEs within a specified monitoring area exceeds a specified threshold).

[0071] By executing the above-mentioned area optimization control, it is possible to obtain a desired communication quality (e.g., throughput) throughout the entire service area 20A consisting of multiple cells 20C(1) to 20C(7) formed by HAPS (airborne platform) 10 toward the ground.

[0072] However, the above-mentioned area optimization control takes several minutes to several tens of minutes to obtain the population distribution (or user distribution, UE distribution, etc.) and perform optimization calculation processing, and therefore, although it is applicable when the aircraft 100 of the HAPS (airborne platform) 10 is hovering at a fixed point, when the user distribution (or UE distribution) seen from the aircraft 100 moves or rotates due to high-speed movement, turning, or attitude change of the aircraft 100, the area optimization control may not be able to keep up with the changes in distribution.

[0073] In this embodiment, the movement of the cells 20C(1)-20C(7) due to the turning of the aircraft 100 is compensated for by FP (footprint) fixed control, and the beams of each cell 20C(1)-20C(7) are corrected by area optimization control. In particular, in this embodiment, the movement of the cells 20C(1)-20C(7) due to the turning of the aircraft 100 is compensated for by using FP (footprint) fixed control that can be controlled at high frequency, and the beams of each cell are corrected by using area optimization control that is controlled at low frequency, thereby realizing beam optimization by optimizing antenna parameters even in an environment where the aircraft 100 moves at high speed, turns, or changes its attitude. As a result, it is possible to maximize the coverage and communication capacity of the service area 20A even in an environment where the aircraft 100 of the HAPS (aerial platform) 10 moves at high speed, turns, or changes its attitude.

[0074] That is, as shown in Table 1, the area optimization control can accommodate changes in user (UE) distribution, but cannot accommodate high-speed movement, turning, and attitude changes of the aircraft 100 of HAPS10. On the other hand, the FP fixed control can accommodate high-speed movement, turning, and attitude changes of the aircraft 100 of HAPS10, but cannot accommodate changes in user (UE) distribution. Therefore, in this embodiment, by combining the area optimization control and the FP fixed control, it is possible to accommodate both the high-speed movement, turning, and attitude changes of the aircraft 100 of HAPS10 and changes in user (UE) distribution. [Table 1]

[0075] 5(a) and 5(b) are explanatory diagrams showing an example of cell arrangement before and after application of FP lock control in a service area 20A consisting of seven cells 20C(1) to 20C(7). The illustrated example shows an example of movement of footprints 20F(1) to 20F(7) of cells 20C(1) to 20C(7) due to rotational motion (yaw rotation) and translational motion of HAPS 10.

[0076] In the HAPS10, the airframe 100 may move at high speed (translational movement), turn (rotational movement), or change its attitude due to the influence of air currents and atmospheric pressure in the stratosphere and the like. Therefore, in a multi-cell configuration as shown in Fig. 5(a), it is assumed that a large number of UEs (terminal devices) located at cell boundaries in the service area 20A will simultaneously perform handover (HO) due to the movement of footprints 20F(1)-20F(7) of cells 20C(1)-20C(7) formed on the ground (or on the sea, etc.), and this may cause an increase in control signals due to HO or communication interruption due to HO failure. In addition to HO, the influence of a decrease in the received power at the UE (moving out of the coverage area) may also be considered.

[0077] Therefore, in the FP fixed control of this embodiment, as a measure against frequent HOs and a drop in reception power due to the high-speed movement, rotation, or attitude change of the aircraft, control is performed so that the footprints 20F(1) to 20F(7) on the ground (or on the sea, etc.) do not move even if the aircraft 100 of the HAPS10 moves, turns, or changes its attitude at high speed, as shown in Fig. 5(b). For example, a digital beamforming (DBF) controllable array antenna having multiple antenna elements is used as the SL antenna 111, and the amplitude and phase of the signal transmitted and received by each antenna element of the SL antenna 111 are controlled by adjusting the antenna weight applied to the signal transmitted and received by each antenna element based on at least one of information on the position and attitude (e.g., attitude with respect to a predetermined direction) of the HAPS10. In addition, an antenna having a predetermined directional characteristic is used as the SL antenna 111, and the SL antenna 111 is mechanically controlled to adjust the directivity direction of the SL antenna 111 based on at least one of information on the position and attitude (e.g., attitude with respect to a predetermined direction) of the HAPS10.

[0078] Fig. 6 is an explanatory diagram of an example of a combination of area optimization control and FP fixing control in the control system according to this embodiment. In Fig. 6, the beam is fixed toward each cell in the service area 20A by FP fixing control S220 that is executed frequently (or always continuously), and the area optimization control S210 is executed less frequently than the FP fixing control, and the values ​​of control parameters such as antenna parameters are shared in the storage devices (storage units) 115 and 950, thereby achieving both the area optimization control and the FP fixing control.

[0079] The storage devices 115, 950 are configured, for example, by a memory or a register on a control board such as a BF board that performs beamforming control, and are provided in the relay communication station 110 or the remote control device 95. For example, when a control device (control unit) that performs area optimization control and FP fixing control is provided in the relay communication station 110 of the HAPS 10 in the sky, the storage device 115 is provided in the relay communication station 110. When a control device (control unit) that performs area optimization control and FP fixing control is provided in the remote control device 95, the storage device 950 is provided in the remote control device 95.

[0080] The storage devices 115 and 950 store information such as the initial values ​​(default values) of the position information of the aircraft 100 shown in Table 2, the initial values ​​(default values) of the antenna parameters, and offset values ​​of the optimal values ​​of the antenna parameters after the area optimization control. In the example of Table 2, the position information of the aircraft 100 is the altitude (h def ), latitude (x def,i ) and longitude (y def,i The initial values ​​of the antenna parameters are information on the horizontal beam direction, horizontal beam width, vertical beam direction and vertical beam width (φ def_str,i , φ def_3dB,i , θ def_str,i , θ def_3dB,i The offset value of the optimal value of the antenna parameter is the amount of change from the initial value of the antenna parameter, and is the offset value (Δφdc_str,i , Δφ dc_3dB,i , Δθ dc_str,i , Δθ dc_3dB,i ) where i (=1 to 7) is the cell ID (cell identification number). [Table 2]

[0081] Instead of the offset value of the optimum value of the antenna parameter, the optimum value of the antenna parameter itself after the area optimization control may be stored. The storage devices 115 and 950 also store the value of the array factor (fixed parameter) that takes into account the element pattern of the SL antenna 111 as setting information used in the FP fixing control S220.

[0082] 7 is an explanatory diagram showing an example of changes in cell placement and size by combining area optimization control and FP fixing control when taking into account the yaw rotation of the communication relay device (HAPS) 10 according to the embodiment. Black circles in FIG. 7 indicate user distribution (UE distribution).

[0083] In the area optimization control S310 and S320 in FIG. 7, the width of the beam for each of the multiple cells 20C(i) is adjusted by optimization control of antenna parameters taking into account the user distribution (UE distribution) in the service area 20A, and the beam is adjusted by a predetermined offset value Δφ in the horizontal beam direction. dc_str,i The control rotates it by only 100 degrees.

[0084] In the FP fixing control S330 and S340 in FIG. 7, the beam for each of the plurality of cells 20C(i) is fixed at a predetermined angle φ fp_str,i By controlling the rotation of the aircraft 100 by only 100 degrees, the rotation of the aircraft 100 is cancelled out.

[0085] In the combined control S350 of the area optimization control and the FP fixed control in FIG. 7, the beam for each of the multiple cells 20C(i) is rotated at a predetermined angle φ fp_str,i +Δφ dc_str,iBy controlling the rotation by only 150 degrees, it is possible to simultaneously perform area optimization that takes into account the user distribution (UE distribution) in the service area 20A and FP fixing.

[0086] Fig. 8 is a flowchart showing an example of the overall control including the area optimization control and the FP fix control according to the embodiment. Fig. 8 shows an example of using the beam forming control (digital control) for controlling the direction of the beam formed by the SL antenna 111 in the FP fix control S220. The control in Fig. 8 is executed by a control device (control device) functioning as an area optimization control device and an FP fix control device provided in the relay communication station 110 or the remote control device 95. This control device corresponds to the FP fix control device 951 and the area optimization control device 952 provided in the remote control device 95 in the device configuration examples in Figs. 12 and 13 described later, and also corresponds to the FP fix control device 116 and the area optimization control device 117 provided in the relay communication station 110 in the device configuration example in Fig. 14. In the following description of Figs. 8 to 11, the devices performing these controls will be referred to as "control devices" without distinction.

[0087] 8, the overall control according to this embodiment includes an area optimization control S210 that is executed infrequently and shares antenna parameters via the storage devices 115 and 950, and an FP fixing control S220 that is executed frequently (or continuously). In the area optimization control S210, the antenna parameters of the SL antenna 111 are optimized so as to form each cell 20C(1) to 20C(7) in accordance with the distribution of the plurality of UEs 61 in the service area 20A based on information on the positions of the plurality of UEs 61 acquired from the base station device 80, etc. In the FP fixing control S220, the direction of the beam formed by the SL antenna 111 is controlled so as to fix the positions of the footprints 20F(1) to 20F(7) of the cells 20C(1) to 20C(7) in the service area 20A based on at least one of information on the position and attitude of the aircraft 100 acquired from a sensor (e.g., a gyro sensor) mounted on the HAPS 10, etc.

[0088] Fig. 9 is a flowchart showing an example of internal processing of FP lock control S220 in the overall control of Fig. 8. In FP lock control S220, first, the control device acquires position and attitude information of the aircraft 100 from a sensor (e.g., a gyro sensor) mounted on the HAPS 10 (S221). The position information of the aircraft 100 is, for example, the coordinates (x, y, z) of the aircraft 100 based on an initial position in a predefined Cartesian coordinate system (with the origin as the origin). The attitude information of the aircraft 100 is the yaw angle y, pitch angle p, and roll angle r of the aircraft based on the movement direction of the initial attitude.

[0089] Next, the control device reads out from the storage device 115, 950 the offset values ​​of the optimal values ​​of the antenna parameters after the most recent optimization by the area optimization control is completed (S222). For example, the control device reads out the offset values ​​(Δφ dc_str,i , Δφ dc_3dB,i , Δθ dc_str,i , Δθ dc_3dB,i ) is read from the storage device 115, 950. The information read from the storage device 115, 950 may include the initial values ​​of the position information of the aircraft 100 and the initial values ​​of the antenna parameters exemplified in Table 2 above.

[0090] Next, the control device determines the steering direction of the beam for the cell 20C(i) according to the position and attitude of the aircraft 100 (horizontal beam direction: φ fp_str,i and vertical beam direction: θ fp_str,i ) is calculated (S223).

[0091] Next, the control device adds offset values ​​of the horizontal beam direction, horizontal beam width, vertical beam direction and vertical beam width after the area optimization control read from the storage device 115, 950 (S224). For example, the control device adds the calculated value of the steering direction (horizontal beam direction: φ fp_str,i and vertical beam direction: θ fp_str,i ), the offset value (Δφ dc_str,i , Δθ dc_str,i) to obtain the desired horizontal and vertical beam direction target values ​​(φ str,i =φ fp_str,i +Δφ dc_str,i , θ str,i =θ fp_str,i +Δθ dc_str,i ) is obtained. In addition, the initial value of the beam width (horizontal beam width: φ def_3dB,i and vertical beam width: θ def_3dB,i ), the horizontal beam width and vertical beam width offset value (Δφ dc_3dB,i , Δθ dc_3dB,i ) to obtain the desired horizontal and vertical beam width target values ​​(φ 3dB,i =φ def_3dB,i +Δφ dc_3dB,i , θ 3dB,i =θ def_3dB,i +Δθ dc_3dB,i ) is obtained.

[0092] Next, the control device calculates the desired horizontal beam direction and vertical beam target value (φ str,i , θ str,i ) and the desired horizontal and vertical beamwidth targets (φ 3dB,i , θ 3dB,i ) is taken into consideration, an antenna weight for each antenna element of the SL antenna 111 is calculated (S225). In calculating the antenna weight, an array factor (fixed parameter) that takes into consideration the element pattern of the SL antenna 111 read from the storage device 115, 950, 950 is used.

[0093] Next, the control device applies the antenna weight calculated for each antenna element of the SL antenna 111 as a setting value for beamforming control of the SL antenna 111 in the relay communication station 110 in the actual environment.

[0094] The control device repeatedly executes the above-mentioned FP fixing control (S221 to S226) at time intervals that are shorter than the execution intervals of the area optimization control (S211 to S213) described below.

[0095] Fig. 10 is a flowchart showing an example of internal processing of area optimization control S210 in the overall control of Fig. 8. In the area optimization control S210 of Fig. 10, first, the control device acquires or estimates information on the positions (terminal position information) of multiple UEs 61 present in the service area 20A from the base station device 80 or the like (S211).

[0096] Next, the control device executes beam optimization calculation by area optimization based on information on the positions (terminal position information) of the multiple UEs 61 acquired or estimated from the base station device 80, etc. (S212). In the beam optimization calculation, for example, the offset values ​​(Δφ) of the horizontal beam direction, horizontal beam width, vertical beam direction, and vertical beam width corresponding to each cell 20C(i) are calculated by optimizing the antenna parameters taking into account the user distribution (UE distribution) in the service area 20A. dc_str,i , Δφ dc_3dB,i , Δθ dc_str,i , Δθ dc_3dB,i ) to calculate

[0097] Next, the control device writes and stores the results of the beam optimization calculation in the storage device 115, 950 as optimal values ​​of the antenna parameters (S213). For example, the control device stores the offset values ​​(Δφ dc_str,i , Δφ dc_3dB,i , Δθ dc_str,i , Δθ dc_3dB,i ) is written and stored in the storage device 115, 950.

[0098] Here, if the result of the previous beam optimization calculation (e.g., the offset value of the antenna parameters) has already been saved in the storage device 115, 950, it is updated with the newly calculated result of the beam optimization calculation (e.g., the offset value of the antenna parameters). If an error occurs when writing the result of the calculation, writing is not performed and the value already saved in the storage device 115, 950 is not updated. The result of the beam optimization calculation (e.g., the offset value of the antenna parameters) written to the storage device 115, 950 may be changed gradually so that the amount of change does not exceed a certain level.

[0099] The control device repeatedly executes the area optimization control (S211 to S213) at time intervals longer than the execution intervals of the FP fixing control (S221 to S226) described above.

[0100] Fig. 11 is a flowchart showing another example of overall control including area optimization control and FP fixing control according to the embodiment. Fig. 11 shows an example of mechanically controlling the directivity direction of the SL antenna 111 in the FP fixing control S220. In Fig. 11, parts common to Figs. 8 to 10 described above are given the same reference numerals and descriptions thereof will be omitted.

[0101] In the area optimization control S210 of FIG. 11, the control device optimizes the offset values ​​(Δφ) of the horizontal beam direction and the vertical beam direction corresponding to each cell 20C(i) by the optimization control of the antenna parameters taking into account the user distribution (UE distribution) in the service area 20A. dc_str,i , Δθ dc_str,i The control device calculates the offset values ​​(Δφ) of the horizontal and vertical beam directions as the optimal values ​​of the antenna parameters (S212'). dc_str,i , Δθ dc_str,i ) is written and stored in the storage device 115 (S213'). The storage device 115 in this control example is, for example, a memory provided in the relay communication station 110 of the HAPS 10 in the sky, or a register on a control board. In this control example, the offset values ​​(Δφ dc_3dB,i , Δθ dc_3dB,i) does not need to be calculated and stored.

[0102] In the FP fixing control S220 in FIG. 11, the control device determines the offset values ​​(Δφ dc_str,i , Δθ dc_str,i ) from the storage device 115 (S222'). In addition, the control device converts the offset values ​​of the horizontal beam direction and the vertical beam direction after the area optimization control read from the storage device 115 into the calculated value of the steering direction (horizontal beam direction: φ fp_str,i and vertical beam direction: θ fp_str,i ) to obtain the desired horizontal and vertical beam direction target values ​​(φ str,i =φ fp_str,i +Δφ dc_str,i , θ str,i =θ fp_str,i +Δθ dc_str,i ) is obtained (S224'). In addition, the control device obtains the target values ​​(φ str,i , θ str,i ) is applied as a setting value for mechanical control of the directivity direction of the SL antenna 111 in the relay communication station 110 in the actual environment (S225'). In this control example, the offset values ​​(Δφ dc_3dB,i , Δθ dc_3dB,i ) is not necessary, and the target values ​​of the horizontal and vertical beam widths (φ 3dB,i , θ 3dB,i ) and application to a real environment are not required.

[0103] Fig. 12 is an explanatory diagram showing an example of the device configuration of a control system according to this embodiment. The control system in Fig. 12 is a device configuration applicable to a communication system including a remote control device 95 capable of executing FP fixing control and area optimization control.

[0104] 12, a remote control device 95 provided on the ground (or sea) includes a storage device (storage unit) 950, an FP fixing control device (footprint fixing control unit) 951, and an area optimization control device (area optimization control unit) 952. The storage device 950 stores offset values ​​of the above-mentioned antenna parameters, etc. The FP fixing control device 951 executes a control program pre-installed therein to perform the above-mentioned FP fixing control. The area optimization control device 952 executes a control program pre-installed therein to perform the above-mentioned area optimization control. The antenna weight for each antenna element calculated by the FP fixing control device 951 is applied in the wireless relay device 71 of the GW station 70 to signals transmitted and received between the wireless relay communication station 110 of the HAPS 10 in the sky.

[0105] The relay communication station 110 of the HAPS 10 in the sky is a repeater-type relay communication station. The wireless relay device (wireless transceiver device) 113 of the relay communication station 110 transmits the signal, to which the antenna weight for each antenna element has been applied, received from the wireless relay device 71 of the GW station 70, to each antenna element of the SL antenna 111. The wireless relay device 113 also transmits the signal received from each antenna element of the SL antenna 111 to the wireless relay device 71 of the GW station 70.

[0106] Fig. 13 is an explanatory diagram showing another example of the device configuration of the control system according to the embodiment. The control system of Fig. 13 is a device configuration applicable to a communication system including a remote control device 95 capable of executing FP fixing control and area optimization control. In Fig. 13, the same reference numerals are used for parts common to Fig. 12 described above, and the description of those parts is omitted. In Fig. 13, the feeder link communication of user data between the GW station 70 and the relay communication station 110 of the HAPS 10 in the sky is omitted.

[0107] 13, the antenna weight for each antenna element calculated by the FP fixed control device 951 is transmitted to the relay communication station 110 of the HAPS 10 in the sky via the wireless relay device 71 of the GW station 70. The relay communication station 110 of the HAPS 10 in the sky is a base station type relay communication station having a base station device 114. The wireless relay device 113 of the relay communication station 110 receives the antenna weight for each antenna element transmitted from the wireless relay device 71 of the GW station 70. The wireless relay device 113 applies the antenna weight to the received signal received by each antenna element of the SL antenna 111 and transmitted to the base station device 114, and applies the antenna weight to the transmitted signal generated by the base station device 114 and transmitted to each antenna element of the SL antenna 111.

[0108] Fig. 14 is an explanatory diagram showing yet another example of the device configuration of the control system according to the embodiment. In Fig. 14, the feeder link communication of the backhaul line between the GW station 70 and the relay communication station 110 of the HAPS 10 in the sky is omitted.

[0109] 14, a relay communication station 110 of a HAPS 10 in the sky includes a base station device 114, a storage device (storage unit) 115, an FP fixation control device (footprint fixation control unit) 116, and an area optimization control device (area optimization control unit) 117. The storage device 115 stores offset values ​​of the above-mentioned antenna parameters, etc. The FP fixation control device 116 executes a control program that is pre-installed to perform the above-mentioned FP fixation control. The area optimization control device 117 executes a control program that is pre-installed to perform the above-mentioned area optimization control. The antenna weight for each antenna element calculated by the FP fixation control device 116 is applied to signals transmitted and received between the base station device 114 and the SL antenna 111.

[0110] As described above, according to this embodiment, it is possible to maximize the coverage and communication capacity of the service area 20A even in an environment where the aircraft 100 of HAPS10, which is an aerial relay-type communication relay device, moves at high speed, turns, or changes in attitude.

[0111] In addition, the present invention can construct a new communications platform for use in large-scale disasters, etc., that can provide ultra-wide area mobile communications services to ground terminal devices from the stratosphere at an altitude of about 20 km, thereby contributing to the achievement of Goal 9 of the Sustainable Development Goals (SDGs), which is to "build infrastructure for industry, innovation and infrastructure."

[0112] The process steps described in this specification and the components of the relay communication station, feeder station, gateway station, remote control device, server, terminal device (user device, mobile station, communication terminal), base station, and base station device of a communication relay device such as a HAPS can be implemented by various means. For example, these processes and components may be implemented by hardware, firmware, software, or a combination thereof.

[0113] With regard to hardware implementation, means such as processing units used to realize the above steps and components in an entity (e.g., a wireless relay station, a feeder station, a gateway station, a base station, a base station device, a wireless relay station device, a terminal device (user equipment, mobile station, communication terminal), a management device, a monitoring device, a remote control device, a server, a hard disk drive device, or an optical disk drive device) may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described in this specification, computers, or combinations thereof.

[0114] Also, for firmware and / or software implementations, the means such as processing units used to realize the components may be implemented with programs (e.g., codes such as procedures, functions, modules, instructions, etc.) that execute the functions described herein. In general, any computer / processor readable medium tangibly embodying firmware and / or software codes may be used to implement the means such as processing units used to realize the steps and components described herein. For example, the firmware and / or software codes may be stored in a memory and executed by a computer or processor, for example in a controller. The memory may be implemented within the computer or processor, or may be implemented externally to the processor. Also, the firmware and / or software codes may be stored in a computer or processor readable medium, such as a random access memory (RAM), a read-only memory (ROM), a non-volatile random access memory (NVRAM), a programmable read-only memory (PROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory, a floppy disk, a compact disk (CD), a digital versatile disk (DVD), a magnetic or optical data storage device, etc. The code may be executed by one or more computers or processors and may cause the computers or processors to perform certain aspects of the functionality described herein.

[0115] The medium may be a non-transitory recording medium. The code of the program may be in any format as long as it can be read and executed by a computer, a processor, or another device or machine, and the format is not limited to a specific format. For example, the code of the program may be any of source code, object code, and binary code, or may be a mixture of two or more of these codes.

[0116] Moreover, the description of the embodiments disclosed herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. [Explanation of symbols]

[0117] 10: HAPS (Airborne Repeater System) 20A: Service area 20C: Cell 20F: Footprint 61: UE (Terminal Equipment) 70: Golden Week Station 71: Radio repeater 80:Base station equipment 90: Mobile communication network (core network) 95: Remote control device 100: Aircraft 110: Relay communication station 111: Service link antenna (SL antenna) 112: Feeder link antenna (FL antenna) 113: Radio repeater 114:Base station equipment 115: Storage device 116: FP fixed control device 117: Area optimization control device 950: Storage device 951 : FP fixed control device 952: Area optimization control device

Claims

1. An airborne relay-type communication relay device forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air, and wirelessly communicates with a plurality of terminal devices present in the cells, an area optimization control unit that executes area optimization control to optimize antenna parameters of the service link antenna so as to form the cells in accordance with a distribution of the plurality of terminal devices in the service area based on information on the positions of the plurality of terminal devices; a footprint fixing control unit that executes footprint fixing control to control a direction of a beam formed by the service link antenna or a main directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on at least one of information on a position and an attitude of the aircraft; A storage unit, The area optimization control unit: estimating locations of the plurality of terminal devices within the service area; optimizing antenna parameters of the service link antenna based on the estimated positions of the terminal devices; storing in the storage unit the optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value based on the initial value of the antenna parameter; the footprint fixation control unit controls the direction of the beam formed by the service link antenna or the main directivity direction of the service link antenna so as to fix the position of the footprint of the cell in the service area based on at least one of information on the position and attitude of the aircraft and the optimal value or the offset value of the antenna parameter stored in the storage unit; A communication relay device comprising:

2. 2. The communication relay device according to claim 1, The area optimization control is performed at a fixed or variable interval frequency; The footprint fixing control is executed more frequently or continuously than the area optimization control. A communication relay device comprising:

3. In the communication relay device of claim 1, the service link antenna is a beamforming controllable array antenna having a plurality of antenna elements, The antenna parameters to be optimized include a horizontal beam direction, a vertical beam direction, and a beam width of a beam formed from the service link antenna toward the cell, The footprint fixing control unit is Calculating a steering direction of a beam formed from the service link antenna toward the cell based on at least one of information on the position and attitude of the aircraft; calculating a plurality of antenna weights corresponding to the plurality of antenna elements based on the calculation result of the steering direction of the beam and the optimal value or the offset value of the antenna parameter stored in the storage unit; applying the plurality of antenna weights to a plurality of signals transmitted and received by the plurality of antenna elements; A communication relay device comprising:

4. 2. The communication relay device according to claim 1, the antenna parameters to be optimized include a horizontal beam direction and a vertical beam direction of a beam formed from the service link antenna toward the cell; The footprint fixing control unit is Calculating a steering direction of a beam formed from the service link antenna toward the cell based on at least one of information on the position and attitude of the aircraft; driving and controlling the service link antenna so as to change a main directivity direction of the service link antenna based on a calculation result of the steering direction of the beam and the optimal value or the offset value of the antenna parameter stored in the storage unit; A communication relay device comprising:

5. 5. The communication relay device according to claim 1, A communication relay device, characterized in that the relay communication station mounted on the aircraft is a repeater-type relay communication station that relays transmitted and received signals without regenerating them.

6. 5. The communication relay device according to claim 1, A communication relay device characterized in that the relay communication station mounted on the aircraft is a base station type relay communication station having a base station device that regenerates transmitted and received signals and re-modulates and relays the regenerated signals.

7. A remote control device capable of communicating with an airborne relay type communication relay device that forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air and wirelessly communicates with a plurality of terminal devices present in the cells, an area optimization control unit that executes area optimization control to optimize antenna parameters of the service link antenna so as to form the cells in accordance with a distribution of the plurality of terminal devices in the service area based on information on the positions of the plurality of terminal devices; a footprint fixing control unit that executes footprint fixing control to control a direction of a beam formed by the service link antenna or a main directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on at least one of information on a position and an attitude of the aircraft; A storage unit, The area optimization control unit: estimating locations of the plurality of terminal devices within the service area; optimizing antenna parameters of the service link antenna based on the estimated positions of the plurality of terminal devices; storing in the storage unit the optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value based on the initial value of the antenna parameter; the footprint fixation control unit controls the direction of the beam formed by the service link antenna or the main directivity direction of the service link antenna so as to fix the position of the footprint of the cell in the service area based on at least one of information on the position and attitude of the aircraft and the optimal value or the offset value of the antenna parameter stored in the storage unit; 13. A remote control device comprising:

8. 8. The remote control device of claim 7, The area optimization control is performed at a fixed or variable interval frequency; The footprint fixing control is executed more frequently or continuously than the area optimization control.

13. A remote control device comprising:

9. 9. A system comprising: a remote control device according to claim 7 or 8; and an airborne relay-type communication relay device which forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air, and wirelessly communicates with a plurality of terminal devices located in the cells.

10. An antenna control method for forming one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the sky, comprising: Executing area optimization control to optimize antenna parameters of the service link antenna so as to form the cells in accordance with a distribution of the terminal devices in the service area based on information on the positions of the terminal devices; Executing footprint fixing control to control a direction of a beam formed by the service link antenna or a main directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on at least one of information on the position and attitude of the aircraft; estimating locations of the plurality of terminal devices in the service area; optimizing antenna parameters of the service link antenna based on the estimated positions of the terminal devices; storing the optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value based on an initial value of the antenna parameter; Controlling the direction of the beam formed by the service link antenna or the main directivity direction of the service link antenna so as to fix the position of the footprint of the cell in the service area based on at least one of information on the position and attitude of the aircraft and the stored optimal value of the antenna parameter or the offset value; 13. An antenna control method comprising:

11. The antenna control method according to claim 10, Executing the area optimization control at a fixed or variable interval frequency; Executing the footprint fixing control more frequently or continuously than the area optimization control; 13. An antenna control method comprising:

12. A program executed by a computer or processor installed in an airborne relay-type communication relay device that forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station installed on an aircraft located in the air, and wirelessly communicates with multiple terminal devices located in the cells, a program code for executing area optimization control for optimizing antenna parameters of the service link antenna so as to form the cells in accordance with a distribution of the plurality of terminal devices in the service area based on information on the positions of the plurality of terminal devices; a program code for executing footprint fixing control for controlling a direction of a beam formed by the service link antenna or a main directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on at least one of information on a position and an attitude of the aircraft; program code for estimating locations of the terminal devices in the service area; program code for optimizing antenna parameters of the service link antenna based on the estimation results of the positions of the plurality of terminal devices; a program code for storing an optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value relative to an initial value of the antenna parameter; program code for controlling a direction of a beam formed by the service link antenna or a main directivity direction of the service link antenna so as to fix a position of a footprint of the cell in the service area based on at least one of information on a position and an attitude of the aircraft and the stored optimal value of the antenna parameter or the offset value; A program comprising:

13. A program executed by a computer or processor provided in a remote control device capable of communicating with an airborne relay type communication relay device that forms one or more cells toward a ground or sea service area via a service link antenna of a relay communication station provided on an aircraft located in the air and wirelessly communicates with multiple terminal devices located in the cells, a program code for executing area optimization control for optimizing antenna parameters of the service link antenna so as to form the cells in accordance with a distribution of the plurality of terminal devices in the service area based on information on the positions of the plurality of terminal devices; a program code for executing footprint fixing control for controlling a direction of a beam formed by the service link antenna or a main directivity direction of the service link antenna so as to fix a position of the footprint of the cell in the service area based on at least one of information on a position and an attitude of the aircraft; program code for estimating locations of the terminal devices in the service area; program code for optimizing antenna parameters of the service link antenna based on the estimation results of the positions of the plurality of terminal devices; a program code for storing an optimal value of the antenna parameter after the optimization is completed or an offset value of the optimal value relative to an initial value of the antenna parameter; program code for controlling a direction of a beam formed by the service link antenna or a main directivity direction of the service link antenna so as to fix a position of a footprint of the cell in the service area based on at least one of information on a position and an attitude of the aircraft and the stored optimal value of the antenna parameter or the offset value; A program comprising:

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