Ground base station, communication relay device, remote control device, system, area control method, and program

Abstract

Provided is a system that, when a service area is optimized via beamforming control, can obtain optimal antenna parameters by taking into account the radio wave propagation characteristics of the actual environment, and can lower the calculation load required to optimize the service area. The system pre-calculates and stores radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or more transmission points assumed for a terrestrial base station or an aerial relay type communication relay device and a plurality of reception points assumed for the service area, estimates the locations of a plurality of terminal devices within the service area, optimizes antenna parameters of a service link antenna on the basis of the results of calculating the radio wave propagation characteristics of the plurality of radio wave propagation paths and the results of estimating the locations of the plurality of terminal devices, and applies the optimal values of the antenna parameters to the service link antenna after the optimization is completed.

Description

Terrestrial base station, communication relay device, remote control device, system, area control method and program

[0001] The present invention relates to optimization of service areas through beamforming control in terrestrial mobile network systems and airborne platform systems.

[0002] Conventionally, there has been known an area optimization method for optimizing antenna parameters of a service link (e.g., the direction and width of a beam for forming a cell) 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 float in the air and remain in operation (see Patent Documents 1 to 4 and Non-Patent Documents 1 to 6).

[0003] For example, Non-Patent Document 1 discloses a method for area optimization assuming that user equipment (hereinafter also referred to as "UE") as terminal devices in an area is distributed uniformly. Non-Patent Document 2 discloses a method for performing optimization for each cell when the area is composed of multiple cells so as to obtain a desired communication quality (e.g., throughput) throughout the entire area. Patent Document 4 discloses a method for estimating the positions of multiple terminal devices (UE) located within a service area, dividing the service area into multiple subareas each including multiple cells, and optimizing multiple types of antenna parameters of a service link antenna for each subarea based on the estimation results of the positions of the multiple terminal devices.

[0004] JP 2022-161734 A JP 2022-161742 A Japanese Patent No. 7318047 A Japanese Patent No. 7108737 A

[0005] 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. Y. Shibata, W. Takabatake, K. Hoshino, and A. 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. 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.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. Eren Balevi and Jeffrey G. Andrews ,"A Novel Deep Reinforcement Learning Algorithm for Online Antenna Tuning", in Proc. IEEE Global Communications Conference (GLOBECOM), 2019.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.

[0006] To apply the above-described area optimization to a real environment, optimization taking into account the radio wave propagation characteristics of the real environment is necessary. One possible area optimization method taking into account the radio wave propagation characteristics of the real environment is optimization using a propagation simulator that simulates the radio wave propagation environment, such as topography and vegetation. In this area optimization control, optimal parameters are obtained by repeatedly updating parameters (antenna patterns) and calculating objective functions (e.g., communication capacity and coverage area) using the updated parameters that take into account the radio wave propagation characteristics of the real environment calculated by the propagation simulator. However, there is a problem in that the amount of calculation required to accurately calculate the radio wave propagation characteristics of the real environment using a propagation simulator (e.g., ray tracing) becomes enormous, making it practically difficult to perform optimization by calculating radio wave propagation estimation every time the antenna parameters are updated.

[0007] A terrestrial base station according to one aspect of the present invention is a terrestrial base station that forms a cell for a terrestrial service area, and includes: calculation means for pre-calculating radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or a plurality of transmission points assumed for the terrestrial base station and a plurality of reception points assumed for the service area, storage means for storing calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths pre-calculated by the calculation means, position estimation means for estimating positions of a plurality of terminal devices within the service area, parameter optimization means for optimizing antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of terminal devices, and parameter application means for applying the optimal values ​​of the antenna parameters to the service link antenna after the optimization is completed.

[0008] According to another aspect of the present invention, there is provided a communication relay device of an airborne relay type that forms 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 air, and wirelessly communicates with a plurality of terminal devices located in the cells. The communication relay device includes: a calculation means that pre-calculates radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or more assumed transmission points for the relay communication station and a plurality of assumed reception points for the service area, a storage means that stores the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths pre-calculated by the calculation means, a position estimation means that estimates the positions of a plurality of terminal devices within the service area, a parameter optimization means that optimizes antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of terminal devices, and a parameter application means that applies the optimized antenna parameters to the service link antenna after the optimization is completed.

[0009] According to yet another aspect of the present invention, there is provided a remote control device capable of communicating with an airborne relay-type communication relay device that forms one or more cells toward a terrestrial or marine service area via a service link antenna of a terrestrial base station that forms a cell toward a terrestrial service area or a relay communication station installed on an aircraft located in the air, and that wirelessly communicates with a plurality of terminal devices located in the cells. The remote control device includes: a calculation means that pre-calculates radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or more assumed transmission points of the terrestrial base station or the relay communication station and a plurality of assumed reception points for the service area, a storage means that stores the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths pre-calculated by the calculation means, a position estimation means that estimates the positions of a plurality of terminal devices within the service area, a parameter optimization means that optimizes antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of terminal devices, and a parameter transmission means that transmits the optimized values ​​of the antenna parameters to the terrestrial base station or the communication relay device after the optimization is completed.

[0010] In the terrestrial base station, the communication relay device, and the remote control device, the position estimation means may estimate the positions of multiple terminal devices within the service area before pre-calculating the radio wave propagation characteristics, and the calculation means may pre-calculate the radio wave propagation characteristics for each of the multiple radio wave propagation paths using the estimated positions of the multiple terminal devices within the service area as the multiple receiving points.

[0011] In the terrestrial base station, the communication relay device, and the remote control device, the radio wave propagation characteristics that are pre-calculated and stored may be radio wave propagation characteristics that do not affect the antenna parameters, and the antenna parameters to be optimized may include multiple gains of the service link antenna in the direction of each of the multiple terminal devices.

[0012] In the terrestrial base station, the communication relay device, and the remote control device, the radio wave propagation characteristics that are pre-calculated and stored may include a plurality of angles viewed in the direction of each of the plurality of receiving points relative to the transmitting point of the service link antenna, and propagation losses of a plurality of radio wave propagation paths between the transmitting point of the service link antenna and the plurality of receiving points, and the antenna parameters to be optimized may include a plurality of gains of the service link antenna in the direction of each of the plurality of terminal devices.

[0013] In the terrestrial base station, the communication relay device, and the remote control device, the parameter optimization means may calculate a plurality of signal-to-noise ratios in a plurality of radio wave propagation paths from the service link antenna to the plurality of terminal devices for a plurality of candidate values ​​of the antenna parameter, and determine an optimal value of the antenna parameter to be applied to the service link antenna so as to maximize a median value of the plurality of signal-to-noise ratios calculated for the plurality of terminal devices.

[0014] In the terrestrial base station, the communication relay device, and the remote control device, the parameter optimization means may perform the parameter optimization using a genetic algorithm.

[0015] In the terrestrial base station, the communication relay device, and the remote control device, the parameter optimization means may repeatedly execute the parameter optimization a plurality of times (T times).

[0016] In the terrestrial base station, the communication relay device, and the remote control device, estimation of the positions of the multiple terminal devices, optimization of the antenna parameters, and application of the optimal values ​​of the antenna parameters to the service link antenna may be performed periodically or when a change in the distribution of the terminal devices in the service area becomes greater than a predetermined change.

[0017] In the communication relay device, the relay communication station may be connected to a mobile communication network via a feeder link to a terrestrial gateway station, and may include a base station processing unit that performs baseband processing.

[0018] In the communication relay device, the relay communication station may include a repeater unit that is connected to a base station device via a feeder link with a terrestrial gateway station and performs radio relay.

[0019] A system according to yet another aspect of the present invention includes any of the remote control devices described above and the terrestrial base station or the above.

[0020] A method according to yet another aspect of the present invention is an area control method for a service area consisting of cells formed from a terrestrial base station or an aerial repeating communication relay device toward the ground, the area control method including: pre-calculating radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or more assumed transmission points of the terrestrial base station or the aerial repeating communication relay device and a plurality of assumed reception points in the service area, retaining the pre-calculated calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths, estimating positions of a plurality of terminal devices within the service area, optimizing antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimated positions of the plurality of terminal devices, and applying the optimized values ​​of the antenna parameters to the service link antenna after the optimization is completed.

[0021] According to yet another aspect of the present invention, there is provided a program executed by a computer or processor provided in an aerial repeating communication relay device that forms one or more cells toward a terrestrial or marine service area via a service link antenna of a terrestrial base station that forms a cell toward a terrestrial service area or a relay communication station provided on an aircraft located in the air, and that wirelessly communicates with multiple terminal devices located in the cells. The program includes: program code for pre-calculating radio wave propagation characteristics for each of multiple radio wave propagation paths between one or more transmission points assumed for the terrestrial base station or the aerial repeating communication relay device and multiple reception points assumed for the service area, program code for retaining the pre-calculated calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths, program code for estimating positions of multiple terminal devices within the service area, program code for optimizing antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths and the estimation results of the positions of the multiple terminal devices, and program code for applying the optimized antenna parameters to the service link antenna after the optimization is completed.

[0022] 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 a terrestrial base station or an aerial repeating communication relay device, the program including: program code for pre-calculating radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or more assumed transmission points for the terrestrial base station or the aerial repeating communication relay device and a plurality of assumed reception points for a service area; program code for storing the pre-calculated calculation results of the radio wave propagation characteristics for the plurality of radio wave propagation paths; program code for estimating positions of a plurality of terminal devices within the service area; program code for optimizing antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics for the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of terminal devices; and program code for transmitting the optimized values ​​of the antenna parameters to the terrestrial base station or the communication relay device after the optimization is completed.

[0023] All or part of the program may include a trained model created by machine learning.

[0024] According to the present invention, in optimizing a service area by beamforming control, optimal antenna parameters can be obtained by taking into account the radio wave propagation characteristics of the actual environment, and the amount of calculation required for optimizing the service area can be reduced.

[0025] FIG. 1 is an explanatory diagram showing an example of the overall configuration of a communication system according to an embodiment. FIG. 2A is an explanatory diagram showing an example of cell layout and size before applying area optimization control for each cell in a service area consisting of seven cells according to an embodiment. FIG. 2B is an explanatory diagram showing an example of cell layout and size after applying the area optimization control. FIG. 3A is an explanatory diagram showing an example of cell layout and size before applying area optimization control as viewed from above in FIG. 2A. FIG. 3B is an explanatory diagram showing an example of cell layout and size after applying area optimization control as viewed from above in FIG. 2B. FIG. 4 is an explanatory diagram showing examples of antenna tilt angle, horizontal half width, and vertical half width as antenna parameters used in area optimization control. FIG. 5A is an explanatory diagram showing an example of a cell configuration of a service area consisting of seven cells, with the central cell being small in size. FIG. 5B is an explanatory diagram showing an example of a cell configuration of a service area consisting of seven cells with equal cell sizes. FIG. 6 is a flowchart showing an example of general optimization control using a genetic algorithm according to a reference example. FIG. 7A is an explanatory diagram showing an example of crossover in a genetic algorithm applicable to area optimization control. Fig. 7B is an explanatory diagram showing an example of mutation in the genetic algorithm. Fig. 8A is an explanatory diagram showing an example of radio wave propagation in a line-of-sight environment between a terminal device located in a flat ground area and a terrestrial base station. Fig. 8B is an explanatory diagram showing an example of radio wave propagation in a non-line-of-sight environment between a terminal device located in a mountainous area and a terrestrial base station. Fig. 9 is a flowchart showing an example of area optimization control taking into account radio wave propagation characteristics according to a reference example. Fig. 10 is a flowchart showing an example of area optimization control taking into account radio wave propagation characteristics in a communication system according to an embodiment.

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A system according to the embodiment described herein is a communication system in which a terrestrial base station or an airborne repeater (HAPS) serving as an airborne platform in a terrestrial mobile network system pre-calculates and stores radio wave propagation characteristics for each of multiple radio wave propagation paths between one or more assumed transmission points for the terrestrial base station or the airborne repeater (HAPS) and multiple assumed reception points for a service area, estimates the positions of multiple terminal devices within the service area, and performs area optimization control to optimize antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths and the estimated positions of the multiple terminal devices. This area optimization control enables the terrestrial base station, the airborne repeater (HAPS), or other such system to obtain optimal antenna parameters by controlling beamforming to optimize the service area, taking into account the radio wave propagation characteristics of a real environment, thereby reducing the amount of calculation required for optimizing the service area.

[0027] 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 for fifth-generation or later-generation mobile communications that supports simultaneous connection to a large number of terminal devices (hereinafter referred to as "UEs") 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 beyond the fifth generation.

[0028] 1, the communication system includes, for example, 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 (radio relay device) constituting an airborne platform. The HAPS 10 is an airborne relay-type, airborne station-type, or airborne 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.

[0029] HAPS 10 is an air vehicle or floating body fuselage 100 that is controlled by autonomous control or external control to float or fly in a high-altitude airspace (floating airspace) 100 km or less above ground or sea level, and is equipped with a relay communication station 110. The airspace in which HAPS 10 is located may be, for example, stratospheric airspace with an altitude H of 18 km or more and 50 km or less. This airspace may also be an airspace with an altitude of 15 km or more and 25 km or less where meteorological conditions are relatively stable, and may particularly be an airspace with an altitude of approximately 20 km.

[0030] The cell formation target airspace, which is the target airspace in which a three-dimensional cell is formed by HAPS10, may be an airspace within a predetermined altitude range (e.g., an altitude range of 50 m or more and 1000 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).

[0031] The cell formation target airspace may be above the sea, a river, or a lake. The three-dimensional cell formed by the HAPS 10 may also be formed to reach the ground or sea surface so as to enable communication with UEs 61 located on the ground or sea.

[0032] The HAPS 10 wirelessly communicates with the UE 61 via a service link antenna (also referred to as an "SL antenna") 111 of a relay communication station 110 provided on an airframe 100, such as an aircraft or floating object, located in the sky. The HAPS 10 may be equipped with at least one of a battery and a solar power generation system and fly using electric power. The HAPS 10 may be a solar plane-type HAPS as shown in the figure, or an airship-type HAPS. The HAPS 10 provided with the relay communication station 110 may be an artificial satellite (e.g., a communication satellite), a balloon, or an unmanned aerial vehicle (UAV) such as a drone or a UAS (Unmanned Aircraft Systems). The HAPS 10 may fly using at least one of a battery and an engine as a power source. The UAV may be, for example, an unmanned aircraft that runs on fuel, or a drone that runs on batteries, etc.

[0033] 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 communicate with the UE 61 over the service link SL via the SL antenna 111. The SL antenna 111 is, for example, a beamforming-controllable array antenna that can control the direction and width of each of multiple beams that form multiple 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 three-dimensional cells 20C(1) to 20C(7). Adjacent beams in the cell formation target airspace may partially overlap. Furthermore, the multiple communication areas where the multiple cells 20C(1) to 20C(7) reach the ground (or sea, etc.) are footprints 20F(1) to 20F(7).

[0034] 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.

[0035] 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 also be a massive antenna in which multiple antenna elements are arranged two-dimensionally and capable of controlling beam directivity in the horizontal and vertical directions.

[0036] The relay communication station 110 can communicate over the feeder link FL with a gateway device (also referred to as a "feeder station"; hereinafter referred to as a "GW station") 70 for HAPS installed on land (or 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 also be a massive antenna in which multiple antenna elements are arranged two-dimensionally and whose directivity in the horizontal and vertical directions can be controlled. In the figure, the feeder link FL (F) 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.

[0037] The relay communication station 110 mounted on the HAPS10 aircraft 100 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 that has a base station device that regenerates transmitted and received signals and re-modulates and relays the regenerated signals.

[0038] The repeater-type relay communication station 110 functions as a repeater slave corresponding to the repeater master constituted by the GW station 70, and is, for example, a wireless relay device (hereinafter also referred to as a "frequency converting repeater") that converts the frequency of a feeder link that is different from the frequency 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 the converted frequency 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 the converted frequency to the base station device 80 via the GW station 70.

[0039] The repeater-type relay communication station 110 includes, for example, a repeater and a frequency converter. 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, etc. The frequency converter converts between the frequency of the service link SL and the frequency of the feeder link FL.

[0040] The base station type relay communication station 110 includes a base station device and a frequency conversion device. The base station device includes a baseband processing unit that processes baseband signals of a service link, a communication interface unit for communicating with the 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.

[0041] In the following embodiment, a case will be mainly described in which the relay communication station 110 mounted on the airframe 100 of the HAPS 10 is a repeater-type relay communication station (repeater slave station).

[0042] 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 with 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 into a moving object such as a vehicle such as an automobile, or a drone, which is an aircraft such as a small remotely controlled helicopter, or may be a terminal device for an IoT (Internet of Things) device.

[0043] HAPS 10 may autonomously control its own floating movement (flight) and the processing and control at the relay communication station 110 by executing a control program using a control unit configured with an internally incorporated computer or processor. For example, HAPS 10 may autonomously perform area optimization control, which will be described later. HAPS 10 may also acquire its own current location information (e.g., GNSS (Global Navigation Satellite System) location information such as GPS location information), pre-stored location control information (e.g., flight schedule information), location information of other HAPSs located in the vicinity, and autonomously control its floating movement (flight) and the processing and control at the relay communication station 110 based on this information.

[0044] Information about 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 about 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.

[0045] Furthermore, the levitation and movement (flight) of the HAPS 10 and the processing and control at the relay communication station 110 may be controlled by a remote control device 95 provided in a communication center or the like of the mobile communication network 90. ​​The remote control device 95 may be configured, for example, as a computer device such as a PC, a server, or the like. The HAPS 10 may incorporate 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., an IP address, a telephone number, etc.) so as to be identifiable from the remote control device 95. The MAC address of the communication interface may be used to identify the control communication terminal device.

[0046] The remote control device 95 may perform area optimization control, which will be described later, by cooperating with the HAPS 10 and the terrestrial base station 30, for example.

[0047] Furthermore, the HAPS 10 may transmit monitoring information, such as information relating to the floating movement (flight) of itself or surrounding HAPSes, processing at the relay communication station 110, position information of the HAPS 10, information relating to the status of the HAPS 10, 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 for the HAPS. The monitoring information may include at least one of information relating to the current position of the HAPS 10, flight route history information, airspeed, ground speed and thrust direction, wind speed and direction of air currents around the HAPS 10, and atmospheric pressure and temperature around the HAPS 10.

[0048] The duplexing method for 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. Furthermore, the access method for wireless communication between relay communication station 110 and 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. Furthermore, the wireless communication may use MIMO (Multi-Input and Multi-Output) technology, which 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. The MIMO technology may be SU-MIMO (Single-User MIMO) technology, in which one base station transmits multiple signals to one UE at the same time and frequency, or MU-MIMO (Multi-User 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.

[0049] In the communication system configured as described above, for example, a signal from a base station device 80 is relayed by the GW station 70 and the HAPS 10, and communication services can be provided to UEs (portable terminals) 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 that functions as an airborne platform, can provide ultra-wide area mobile communication services directly to UEs (portable terminals) 61 on the ground from the stratosphere at altitudes of 18 km or more and 50 km or less (particularly, about 20 km). Furthermore, airborne platforms consisting of the HAPS 10 are attracting attention as a new form of communication suitable for use in large-scale disasters and the like.

[0050] In the communication system of this embodiment, area optimization is performed to optimize the antenna parameters of the SL antenna 111 so as to obtain a desired communication quality (e.g., throughput) throughout the entire service area 20A, which is made up of multiple cells 20C(1) to 20C(7) formed toward the ground by an airborne platform such as HAPS 10. For example, in an airborne platform such as HAPS 10 that covers the service area 20A with multiple cells 20C(1) to 20C(7), area optimization control is performed to optimize the direction and width of the beam of each cell according to the population distribution (or user distribution, UE distribution, etc.).

[0051] In the area optimization control, for example, in a multi-cell configuration in which a service area 20A is composed of multiple cells 20C(1) to 20C(7), the placement of each cell is optimized to maximize the communication capacity and coverage area of ​​the entire service area according to population distribution and traffic distribution. A genetic algorithm (GA), for example, can be used as the optimization control algorithm (see Patent Document 4 mentioned above).

[0052] For example, as shown in Figures 2A and 3A, if multiple cells 20C(1) to 20C(7) of the same size are uniformly distributed within a service area 20A without applying area optimization control, coverage and communication capacity may be reduced in the user (UE)-dense area located to the left of the service area 20A in the figures. On the other hand, as shown in Figures 2B and 3B, area optimization control is applied, which optimizes the beam direction and width for each of the multiple cells 20C(1) to 20C(7) based on big data such as the population distribution in the service area 20A. By applying area optimization control in this way, the number of cells covering the user (UE)-dense area located to the left of the service area 20A can be increased to intensively cover the user (UE)-dense area, thereby suppressing a decrease in communication capacity in the user (UE)-dense area. This allows for maximizing coverage and communication capacity in the service area 20A.

[0053] In the area optimization control, for example, in the area optimization of an area consisting of multiple (N) cells, the following four types of antenna parameters A to D are defined and used as multiple types of antenna parameters for any i-th cell i within the area, and a total of 4N antenna parameters are optimized. 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

[0054] As shown in FIG. 4, 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 The 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 a horizontal plane P containing a 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.

[0055] Also, the horizontal direction ω of the i-th cell 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 the HAPS 10 as a reference point.

[0056] The objective function in the area optimization control can be, for example, a function corresponding to 50% of the ideal throughput for multiple terminal devices (users) in the service area consisting of multiple cells. The ideal throughput in the service area can be calculated using, for example, the following equation (1).

[0057] Here, the above formula (1) indicates the throughput for the u-th terminal device (user) of the c-th cell in the service area. In the formula, "c" is the cell number, "u" is the user number, and "γ ｃ，ｕ " is the downlink SINR (signal to noise ratio), and "N ａｖｇ " is the value obtained by dividing the total number of terminal devices (total number of users) in the service area by the number of cells, and "N ｃ " is the number of terminal devices (users) in the cth cell.

[0058] In the above formula (1), is the Shannon capacity, is a weighting factor that takes into account the number of terminal devices (users) per cell. For example, as shown in FIG. 5A, if the cell size of the central cell 20C(1) in a service area 20A consisting of multiple cells is smaller than the surrounding cells 20(2) to 20(7), then the cell 20C(1) On the other hand, if all the cells 20C(1) to 20C(7) in the service area 20A have the same cell size as shown in FIG. 5B, the throughput of the cell 20C(1) is weighted low. Therefore, the weighting value is 1.

[0059] Constraints in area optimization control can be set, for example, so that 99% of terminal devices (users) within the service area 20A satisfy the conditions in Table 1 below (see Non-Patent Document 6 mentioned above).

[0060] 6 is a flowchart showing an example of general optimization control using a genetic algorithm (GA) that can be applied to area optimization control. A genetic algorithm (GA) is an algorithm created by imitating the evolutionary process of living organisms, and performs optimization by repeatedly selecting, crossing over, and mutating "genes," making it possible to discover excellent solutions within a practical time frame.

[0061] In FIG. 6 , for example, the initial population corresponds to multiple sets of antenna parameters for a terrestrial base station or an airborne relay-type communication relay device (HAPS), each individual (parent, child) corresponds to a communication system for the entire service area, and genes correspond to antenna parameters. In FIG. 6 , first, an initial population consisting of multiple sets of individuals is randomly generated (S101). Next, in each generation, the genetic scores of the individuals are evaluated using an "objective function" (S102), parents are selected (S103), and genetic crossover (see FIG. 7A) and mutation (see FIG. 7B) are applied (S104), and the next generation of individuals are determined (S105). Here, mutation can avoid local optima. By repeatedly executing these processes from S102 to S105 until a predetermined number of iterations (number of generations for convergence determination) is reached (S102 to S106), superior genes are inherited to maximize the objective function (genetic scores of the individuals).

[0062] By applying the genetic algorithm (GA) to area optimization control and repeating the change and evaluation of antenna parameters, it is possible to approach the optimal solution for the antenna parameters.

[0063] In order to reflect the above-mentioned area optimization technique in the actual environment of service area 20A of a communication system and obtain an improvement effect in communication capacity (throughput) and coverage, optimization is required that takes into consideration in advance the radio wave propagation characteristics in the actual environment, which is affected by diffraction and reflection due to obstacles 40 such as terrain, buildings, and vegetation, as shown in Fig. 8B, rather than a simple model such as a flat ground as shown in Fig. 8A. As a method for taking into consideration the radio wave propagation characteristics in the actual environment, a method that takes into consideration radio wave propagation in the actual environment in an evaluation after changing parameters can be considered.

[0064] 9 is a flowchart showing an example of area optimization control that takes radio wave propagation characteristics into consideration according to a reference example. In FIG. 9 , initial antenna parameters are set (S201), and then area evaluation (S202) when the antenna parameters are applied, antenna parameter change (S203), and convergence determination (S204) are repeatedly performed to obtain an optimal solution for the antenna parameters. In the area evaluation (S202) of this area optimization control, a propagation simulator is used (S205) to simulate a real environment that is affected by diffraction and reflection due to obstacles 40 such as topography, buildings, and vegetation, and estimate radio wave propagation characteristics using a ray tracing method or the like. An objective function (communication capacity and coverage size) is calculated taking into account the radio wave propagation characteristics of the real environment estimated by the propagation simulator.

[0065] However, estimating radio wave propagation characteristics in a real environment using a propagation simulator (S205) (estimation using a ray tracing method or the like) requires a long calculation time. In particular, when the number of reflections and diffractions of radio waves increases in a real environment as illustrated in FIG. 8B , the calculation time becomes enormous. Furthermore, attempting to estimate radio wave propagation characteristics in a real environment with high accuracy requires a huge amount of calculation. Therefore, it is practically difficult to perform optimization by calculating an objective function (communication capacity or coverage size) that involves estimating radio wave propagation characteristics every time the antenna parameters are updated.

[0066] Therefore, in this embodiment, radio wave propagation characteristics are calculated in advance for each of a plurality of radio wave propagation paths between one or more assumed transmission points for the airborne relay type communication relay device (HAPS) 10 (see FIGS. 1 to 4) and the terrestrial base station 30 (see FIGS. 8A and 8B) and a plurality of assumed reception points for the service area 20A. Then, the positions of a plurality of user equipment (UE) 61 within the service area 20A are estimated, and the antenna parameters of the service link antennas 111, 31 are optimized based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of user equipment (UE) 61.

[0067] Here, before pre-calculating the radio wave propagation characteristics, the positions of multiple terminal devices (UE) 61 within the service area 20A may be estimated, and the estimated positions of the multiple terminal devices (UE) 61 within the service area 20A may be used as the multiple reception points to pre-calculate and store radio wave propagation characteristics for each of the multiple radio wave propagation paths. In this case, radio wave propagation characteristics may be recalculated for some or all of the multiple radio wave propagation paths each time one or more terminal devices (UE) 61 within the service area 20A move. In particular, when one or some of the terminal devices (UE) 61 within the service area 20A move, the radio wave propagation characteristics may be recalculated only for the one or some of the terminal devices (UE) 61 that have moved, thereby improving the efficiency of the calculation. Furthermore, when calculating the radio wave propagation characteristics of the radio wave propagation paths using the estimated positions of the terminal devices (UE) 61 within the service area 20A as reception points, the amount of calculation can be reduced compared to conventional general calculations of radio wave propagation characteristics in which the transmission antenna gain at the transmission point is set in advance.

[0068] Furthermore, for example, the center points of a plurality of small-sized sections that are set by dividing the service area 20A into a mesh pattern may be used as the plurality of receiving points, and the radio wave propagation characteristics may be calculated in advance for each of the plurality of radio wave propagation paths.

[0069] Furthermore, in the case of a system including an aerial repeater type communication repeater (HAPS) 10 (see FIGS. 1 to 4), the area optimization control of this embodiment may be performed in combination with footprint fixation control (see patent application filed by the present applicant (Japanese Patent Application No. 2023-177048)). In footprint fixation control, the direction of the beam formed by the service link antenna (SL antenna 111) or the directivity direction of the service link antenna (SL antenna 111) is controlled so as to fix the position of the footprint of the cell in the service area 20A, based on information on at least one of the position and attitude of the aerial repeater type communication repeater (HAPS) 10. By combining this footprint fixation control, area optimization control can be performed assuming that the aerial repeater type communication repeater (HAPS) 10 is stopped at a fixed point.

[0070] The pre-calculated and stored radio wave propagation characteristics may be radio wave propagation characteristics that do not affect antenna parameters. For example, the pre-calculated and stored radio wave propagation characteristics may include a plurality of angles viewed in the direction of each of a plurality of reception points relative to the transmission point of the service link antenna 111, 31, and propagation losses of a plurality of radio wave propagation paths between the transmission point of the service link antenna and the plurality of reception points. Furthermore, the antenna parameters to be optimized may include a plurality of gains of the service link antenna 111, 31 in the direction of each of a plurality of user equipments (UEs) 61.

[0071] FIG. 10 is a flowchart showing an example of area optimization control that takes into account radio wave propagation characteristics in a communication system according to an embodiment. The area optimization control of FIG. 10 can be applied to both the airborne relaying communication relay device (HAPS) 10 and the terrestrial base station 30. In FIG. 10 , initial antenna parameters are set (S301). Then, for each of a plurality of radio wave propagation paths (paths) between one or more pre-estimated transmission points and a plurality of pre-estimated reception points in the service area 20A, the angle and propagation loss of each path are pre-calculated and stored (S302). Next, the service area (communication area) 20A when the antenna parameters are applied is evaluated based on the pre-calculated and stored calculated values ​​of the angle and propagation loss of each path and the estimated positions of a plurality of terminal devices (UEs) 61 within the service area 20A (S303). For example, the service area (communication area) 20A is evaluated by calculating at least one of the communication capacity and coverage size of the service area (communication area) 20A. Then, the antenna parameters of the service link antennas 111 and 31 are repeatedly changed and the service area (communication area) 20A is repeatedly evaluated (S303 to S304) until the evaluation result of the service area (communication area) 20A satisfies a predetermined convergence condition, thereby obtaining an optimal solution for the antenna parameters.

[0072] After the optimization is completed, the final updated values ​​of the antenna parameters of each cell in the service area 20A are applied as the control setting values ​​of the antenna 31 of the terrestrial base station 30 and the SL antenna 111 at the relay communication station 110 of the HAPS (Airborne Platform) 10.

[0073] The area optimization control illustrated in FIG. 10 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).

[0074] By executing the area optimization control, it is possible to obtain a desired communication quality (for example, throughput) throughout the entire service area 20A made up of a plurality of cells 20C(1) to 20C(7).

[0075] The optimum values ​​of the antenna parameters may be determined by calculating the signal-to-noise ratio (SNR) for each radio wave propagation path as shown below. Here, to simplify the radio wave propagation model, N radio wave propagation paths are formed between one transmitting point of the service link antennas 111, 31 and multiple (N) receiving points, and only one path is considered for transmission and reception. The antenna parameters subject to area optimization control are the antenna gain (beam direction and beam width) for each path of the service link antennas 111, 31.

[0076] In the comparative reference example on flat ground shown in FIG. 8A, the signal-to-noise ratio (SNR(1) to SNR(N)) in each radio wave propagation path (path) is expressed by the following equation (2).

[0077] Here, Pt is the transmission power, G(θ(n)) is the antenna gain at the angle θ(n) in the direction of the terminal device (user) 61(n) (θ is a value uniquely determined by the positional relationship between the interfering station and the terminal device (user)), Ploss is the free space propagation loss for each path, Gr is the receiving antenna gain, and Pn is the noise power on the receiving side. For example, when determining the antenna gain G(θ) that maximizes the median of SNR(1) to SNR(N) in the above equation (2) (maximizing coverage), the antenna gain (beam direction and beam width) for each path of the service link antennas 111 and 31 can be optimized by changing the beam direction, beam width, etc., that is, by changing the antenna gain G(θ) in the direction of the terminal device (user) and repeating the above SNR calculation. If the ground is flat, calculating the angle θ and the free space propagation loss Ploss takes almost no time, so there is no problem in repeating the calculation each time area optimization is performed (each time the antenna parameters are changed).

[0078] On the other hand, when considering propagation loss in an environment affected by diffraction and reflection due to obstacles 40 such as terrain, buildings, and vegetation as shown in FIG. 8B, it is necessary to calculate the free space propagation loss Ploss' and the angle θ' (tilt angle θ' and azimuth angle φ' in a three-dimensional sense). When multiple paths are considered, it is necessary to calculate the propagation losses (Ploss'(1) to Ploss'(N)) for N paths and their corresponding angles (θ'(1) to θ'(N)). In other words, every time the antenna parameters are changed, it is necessary to calculate the angles θ'(1) to θ'(N), the propagation losses Ploss'(1) to Ploss'(N), and the noise power Pn on the receiving side in the following equation (3). This results in an enormous amount of calculation.

[0079] In the area optimization control of this embodiment, the propagation loss Ploss' and angle θ' in the above equation (3) are pre-calculated and stored in a storage unit (storage means) such as a memory, and the calculation is repeated while changing G(θ'), thereby reducing the amount of calculation and enabling area optimization. When multiple (N) paths are taken into consideration, the propagation losses (Ploss'(1) to Ploss'(N)) for N paths and the corresponding angles (θ'(1) to θ'(N)) are pre-calculated and stored.

[0080] In this embodiment, the HAPS 10 also functions as the following means A1 to A5 by having a control unit configured with an internally incorporated computer, processor, or the like execute a control program: A1. Calculation means for pre-calculating radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or a plurality of transmission points assumed for the relay communication station 110 and a plurality of reception points assumed for the service area 20A; A2. Storage means for storing calculation results of the pre-calculated radio wave propagation characteristics of the plurality of radio wave propagation paths; A3. Position estimation means for estimating the positions of a plurality of terminal devices 61(1) to 61(N) within the service area 20A; A4. Parameter optimization means for optimizing antenna parameters of the service link antenna 111 based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of terminal devices 61(1) to 61(N); and A5. Parameter application means for applying the optimal values ​​of the antenna parameters to the service link antenna 111 after the optimization is completed.

[0081] In this embodiment, the terrestrial base station 30 also functions as the following means B1 to B5 by having a control unit configured by an internally incorporated computer, processor, or the like execute a control program: B1. Calculation means for pre-calculating radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or a plurality of transmission points assumed for the terrestrial base station 30 and a plurality of reception points assumed for the service area 20A; B2. Storage means for storing the calculation results of the radio wave propagation characteristics of the pre-calculated plurality of radio wave propagation paths; B3. Position estimation means for estimating the positions of a plurality of terminal devices 61(1) to 61(N) within the service area 20A; B4. Parameter optimization means for optimizing antenna parameters of the service link antenna 31 based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of terminal devices 61(1) to 61(N); and B5. Parameter application means for applying the optimal values ​​of the antenna parameters to the service link antenna 31 after the optimization is completed.

[0082] The remote control device 95 also functions as the following means C1 to C5 by having a control unit configured with an internally incorporated computer, processor, or the like execute a control program: C1. Calculation means for pre-calculating radio wave propagation characteristics for each of multiple radio wave propagation paths between one or multiple assumed transmission points for the terrestrial base station 30 or the relay communication station 110 of the airborne relay type communication relay device (HAPS) 10 and multiple assumed reception points for the service area 20A; C2. Storage means for storing calculation results of the pre-calculated radio wave propagation characteristics for the multiple radio wave propagation paths; C3. Position estimation means for estimating the positions of multiple terminal devices 61(1) to 61(N) within the service area 20A; C4. Parameter optimization means for optimizing antenna parameters of the service link antennas 31, 111 based on the calculation results of the radio wave propagation characteristics for the multiple radio wave propagation paths and the estimated positions of the multiple terminal devices 61(1) to 61(N); and C5. Parameter transmission means for transmitting the optimum values ​​of the antenna parameters after the optimization is completed to the terrestrial base station 30 or the communication relay device (HAPS) 10.

[0083] As described above, according to this embodiment, in optimizing the service area 20A by beamforming control in the terrestrial base station 30 and the relay communication station 110 of the airborne relay communication relay device (HAPS) 10, optimal antenna parameters can be obtained by taking into account the radio wave propagation characteristics of the actual environment, and the amount of calculation required to optimize the service area 20A can be reduced.

[0084] Furthermore, the present invention can build a new communications platform for use in large-scale disasters, etc., that can provide ultra-wide area mobile communications services to terminal devices on the ground 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 resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0085] The process steps described herein and the components of the relay communication station, feeder station, gateway station, remote control device, server, terminal device (user equipment, mobile station, communication terminal), base station, and base station device of a communication relay device such as HAPS can be implemented by various means. For example, these processes and components may be implemented by hardware, firmware, software, or a combination thereof.

[0086] 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, a mobile station, a 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 herein, computers, or combinations thereof.

[0087] Furthermore, with regard to firmware and / or software implementations, the means, such as a processing unit, used to realize the components may be implemented with a program (e.g., code, such as procedures, functions, modules, instructions, etc.) that performs the functions described herein. In general, any computer / processor-readable medium tangibly embodying firmware and / or software code may be used to implement the means, such as a processing unit, used to realize the steps and components described herein. For example, the firmware and / or software code may be stored in a memory and executed by a computer or processor, such as in a controller. The memory may be implemented within the computer or processor, or external to the processor. The firmware and / or software code may also be stored on a computer or processor readable medium such as, for example, random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), flash memory, floppy disk, compact disk (CD), digital versatile disk (DVD), 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.

[0088] The medium may be a non-transitory recording medium. The program code may be in any format as long as it can be read and executed by a computer, processor, or other device or machine. For example, the program code may be in any of source code, object code, and binary code, or may be a mixture of two or more of these codes.

[0089] 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.

[0090] 10: HAPS (airborne relay type communication relay device) 20A: Service area 20C: Cell 20F: Footprint 30: Terrestrial base station 31: Antenna 40: Obstacle 61: UE (terminal device) 70: GW station 71: Wireless relay device 80: Base station device 90: Mobile communication network (core network) 95: Remote control device 100: Aircraft 110: Relay communication station 111: Service link antenna (SL antenna)

Claims

1. A terrestrial base station that forms a cell toward a terrestrial service area, comprising: a calculation means that pre-calculates radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or a plurality of transmission points assumed for the terrestrial base station and a plurality of reception points assumed for the service area; a storage means that stores the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths pre-calculated by the calculation means; a position estimation means that estimates the positions of a plurality of terminal devices within the service area; a parameter optimization means that optimizes antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the plurality of radio wave propagation paths and the estimation results of the positions of the plurality of terminal devices; and a parameter application means that applies the optimal values ​​of the antenna parameters to the service link antenna after the optimization is completed.

2. A terrestrial base station according to claim 1, characterized in that the position estimation means estimates the positions of a plurality of terminal devices within the service area before pre-calculating the radio wave propagation characteristics, and the calculation means pre-calculates the radio wave propagation characteristics for each of the plurality of radio wave propagation paths, using the estimated positions of the plurality of terminal devices within the service area as the plurality of receiving points.

3. A terrestrial base station according to claim 1 or 2, characterized in that the radio wave propagation characteristics that are pre-calculated and stored are radio wave propagation characteristics that do not affect the antenna parameters, and the antenna parameters to be optimized include multiple gains of the service link antenna in the direction of each of the multiple terminal devices.

4. A terrestrial base station according to any one of claims 1 to 3, wherein the radio wave propagation characteristics calculated and stored in advance include a plurality of angles in the direction of each of the plurality of receiving points relative to the transmission point of the service link antenna, and propagation losses of a plurality of radio wave propagation paths between the transmission point of the service link antenna and the plurality of receiving points, and the antenna parameters to be optimized include a plurality of gains of the service link antenna in the direction of each of the plurality of terminal devices.

5. A terrestrial base station according to any one of claims 1 to 4, wherein the parameter optimization means calculates a plurality of signal-to-noise ratios for a plurality of radio wave propagation paths from the service link antenna to the plurality of terminal devices for a plurality of candidate values ​​of the antenna parameters, and determines the optimum value of the antenna parameters to be applied to the service link antenna so as to maximize the median value of the plurality of signal-to-noise ratios calculated for the plurality of terminal devices.

6. An airborne relay-type communication relay device that forms one or more cells toward a terrestrial or marine service area via a service link antenna of a relay communication station installed on an aircraft located in the sky and communicates wirelessly with multiple terminal devices located in the cells, comprising: a calculation means that pre-calculates radio wave propagation characteristics for each of multiple radio wave propagation paths between one or more assumed transmitting points of the relay communication station and multiple assumed receiving points of the service area; a storage means that stores the calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths pre-calculated by the calculation means; a position estimation means that estimates the positions of multiple terminal devices within the service area; a parameter optimization means that optimizes antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths and the estimation results of the positions of the multiple terminal devices; and a parameter application means that applies the optimal values ​​of the antenna parameters to the service link antenna after the optimization is completed.

7. A communication relay device according to claim 6, wherein the position estimation means estimates the positions of a plurality of terminal devices within the service area before pre-calculating the radio wave propagation characteristics, and the calculation means pre-calculates the radio wave propagation characteristics for each of the plurality of radio wave propagation paths, using the estimated positions of the plurality of terminal devices within the service area as the plurality of receiving points.

8. A communication relay device according to claim 6 or 7, characterized in that the radio wave propagation characteristics that are pre-calculated and stored are radio wave propagation characteristics that do not affect the antenna parameters, and the antenna parameters to be optimized include multiple gains of the service link antenna in the direction of each of the multiple terminal devices.

9. A communication relay device according to any one of claims 6 to 8, wherein the radio wave propagation characteristics calculated and stored in advance include a plurality of angles in the direction of each of the plurality of receiving points relative to the transmitting point of the service link antenna, and propagation losses of a plurality of radio wave propagation paths between the transmitting point of the service link antenna and the plurality of receiving points, and the antenna parameters to be optimized include a plurality of gains of the service link antenna in the direction of each of the plurality of terminal devices.

10. A communication relay device according to any one of claims 6 to 9, wherein said parameter optimization means calculates a plurality of signal-to-noise ratios for a plurality of radio wave propagation paths from said service link antenna to said plurality of terminal devices for a plurality of candidate values ​​of said antenna parameters, and determines the optimum value of said antenna parameter to be applied to said service link antenna so as to maximize the median value of said plurality of signal-to-noise ratios calculated for said plurality of terminal devices.

11. A remote control device capable of communicating with an airborne relay-type communication relay device that forms one or more cells toward a terrestrial or marine service area and communicates wirelessly with multiple terminal devices located in the cells via a service link antenna of a terrestrial base station that forms a cell toward a terrestrial service area or a relay communication station installed on an aircraft located in the air, the remote control device comprising: a calculation means that pre-calculates radio wave propagation characteristics for each of multiple radio wave propagation paths between one or more transmission points assumed for the terrestrial base station or the relay communication station and multiple reception points assumed for the service area; a storage means that stores the calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths pre-calculated by the calculation means; a position estimation means that estimates the positions of multiple terminal devices within the service area; a parameter optimization means that optimizes antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths and the estimation results of the positions of the multiple terminal devices; and a parameter transmission means that transmits the optimal values ​​of the antenna parameters to the terrestrial base station or the communication relay device after the optimization is completed.

12. A remote control device according to claim 11, wherein the position estimation means estimates the positions of a plurality of terminal devices within the service area before pre-calculating the radio wave propagation characteristics, and the calculation means pre-calculates the radio wave propagation characteristics for each of the plurality of radio wave propagation paths, using the estimated positions of the plurality of terminal devices within the service area as the plurality of receiving points.

13. A remote control device according to claim 11 or 12, characterized in that the radio wave propagation characteristics include a plurality of angles in the direction of each of the plurality of receiving points relative to the transmitting point of the service link antenna, and propagation losses of a plurality of radio wave propagation paths between the transmitting point of the service link antenna and the plurality of receiving points, and the antenna parameters to be optimized include a plurality of gains of the service link antenna in the direction of each of the plurality of terminal devices.

14. A remote control device according to any one of claims 11 to 13, wherein the parameter optimization means calculates a plurality of signal-to-noise ratios for a plurality of radio wave propagation paths from the service link antenna to the plurality of terminal devices for a plurality of candidate values ​​of the antenna parameters, and determines the optimum value of the antenna parameters to be applied to the service link antenna so as to maximize the median value of the plurality of signal-to-noise ratios calculated for the plurality of terminal devices.

15. A system comprising a remote control device according to any one of claims 11 to 14 and the terrestrial base station or the aerial relay type communication relay device.

16. An area control method for a service area consisting of cells formed from a terrestrial base station or an aerial relay type communication relay device toward the ground, comprising: pre-calculating radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or more assumed transmitting points of said terrestrial base station or said aerial relay type communication relay device and a plurality of assumed receiving points in said service area; storing the pre-calculated calculation results of the radio wave propagation characteristics of said plurality of radio wave propagation paths; estimating the positions of a plurality of terminal devices within said service area; optimizing antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of said plurality of radio wave propagation paths and the estimated positions of said plurality of terminal devices; and applying the optimal values ​​of the antenna parameters to said service link antenna after said optimization is completed.

17. 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 terrestrial or marine service area via a service link antenna of a terrestrial base station that forms a cell toward a terrestrial service area or a relay communication station installed on an aircraft located in the air, and that communicates wirelessly with multiple terminal devices located in the cell, the program comprising: program code for pre-calculating radio wave propagation characteristics for each of multiple radio wave propagation paths between one or more transmission points assumed for the terrestrial base station or the airborne relay type communication relay device and multiple reception points assumed for the service area; program code for storing the pre-calculated calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths; program code for estimating the positions of multiple terminal devices within the service area; program code for optimizing antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of the multiple radio wave propagation paths and the estimation results of the positions of the multiple terminal devices; and program code for applying the optimal values ​​of the antenna parameters to the service link antenna after the optimization is completed.

18. A program executed by a computer or processor provided in a remote control device capable of communicating with a terrestrial base station or an aerial repeater type communication relay device, comprising: program code for pre-calculating radio wave propagation characteristics for each of a plurality of radio wave propagation paths between one or more assumed transmitting points for said terrestrial base station or said aerial repeater type communication relay device and a plurality of assumed receiving points for said service area; program code for storing the pre-calculated calculation results of the radio wave propagation characteristics of said plurality of radio wave propagation paths; program code for estimating the positions of a plurality of terminal devices within said service area; program code for optimizing antenna parameters of a service link antenna based on the calculation results of the radio wave propagation characteristics of said plurality of radio wave propagation paths and the estimation results of the positions of said plurality of terminal devices; and program code for transmitting the optimal values ​​of the antenna parameters to said terrestrial base station or said communication relay device after said optimization is completed.

Images