System including a wide-area cell base station and a terrestrial cell base station

Abstract

Provided is a system that can improve frequency utilization efficiency without degrading the coverage area of a wide-area cell when forming a null in the direction of an antenna of a terrestrial cell base station or the terrestrial cell from a relay communication station in the sky that forms the wide-area cell. 【Solution means】 The wide-area cell base station and the terrestrial cell base station communicate on a service link in the same frequency band using wireless frames that are time-synchronized with each other. The wide-area cell base station acquires information about terrestrial cell base stations that form terrestrial cells overlapping the wide-area cell, and based on the information about the terrestrial cell base stations, determines null scheduling regarding the assignment on the time axis and the frequency axis of the null formed toward the antenna of the terrestrial cell base station or the terrestrial cell, and controls the formation of the directional null based on the null scheduling information.

Description

Technical Field

[0001] The present disclosure relates to a technique for suppressing interference from a relay communication station mounted on an aerial PF such as a HAPS to a terrestrial cell.

Background Art

[0002] Conventionally, a base station that forms a wide-area cell from a repeater-type or base station device-type relay communication station mounted on a high-altitude platform station (HAPS) (also referred to as a "high-altitude pseudo-satellite") located in the sky, a low Earth orbit (LEO) satellite, a geostationary orbit (GEO) satellite, etc. toward the ground or the sea (hereinafter referred to as a "wide-area cell base station") is known. In an environment where such a wide-area cell base station communicates with a UE (terminal) via a service link (hereinafter referred to as an "aerial system"), and an existing terrestrial cell base station communicates with a UE (terminal) via a service link (hereinafter referred to as a "terrestrial system") coexist, when communicating simultaneously using the same frequency band, signals from the relay communication station of the aerial system become interference to the terrestrial system. When this interference from the aerial system occurs, the throughput of the terrestrial system significantly decreases. Similarly, signals from the terrestrial system also become interference to the aerial system. When this interference from the terrestrial system occurs, the throughput of the aerial system decreases.

[0003] Patent Document 1 discloses a technique for suppressing (reducing) interference to the terrestrial system by adjusting the antenna system of a high-altitude platform (HAP) in the sky so as to form a directional beam directed at a null to the terrestrial cell base station based on a map of the eNB (terrestrial cell base station), thereby excluding or avoiding the area covered by the terrestrial cell.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] A system according to one aspect of the present disclosure includes a wide-area cell base station that forms a wide-area cell from a service link antenna of a relay communication station provided on an aerial vehicle or a floating body located in the air toward the ground or the sea, and one or a plurality of terrestrial cell base stations that form terrestrial cells from antennas arranged on the ground or the sea. In this system, the wide-area cell base station and the one or a plurality of terrestrial cell base stations communicate service links in the same frequency band with wireless frames synchronized with each other. The wide-area cell base station acquires information about a terrestrial cell base station that forms a terrestrial cell overlapping the wide-area cell, and based on the information about the terrestrial cell base station, determines null scheduling regarding the allocation of a null formed toward the antenna of the terrestrial cell base station or the terrestrial cell on the time axis and the frequency axis, and controls the formation of the directional null based on the null scheduling information.

[0006] In the system, the wide-area cell base station may acquire traffic information regarding at least one of the service link traffic in the wide-area cell and the service link traffic in the terrestrial cell, and determine the null scheduling based on the traffic information and the information about the terrestrial cell base station.

[0007] In the system, the wide-area cell base station may acquire user distribution information regarding at least one of the geographical distribution of the terminal devices of the users present in the wide-area cell and the geographical distribution of the terminal devices of the users present in the terrestrial cell, and determine the null scheduling based on the user distribution information and the information about the terrestrial cell base station.

[0008] In the system, the wide-area cell base station calculates a selection metric for selecting a terminal device whose communication quality deteriorates due to the formation of the null for each of the terminal devices of a plurality of users located in the wide-area cell, and based on the calculation result of the selection metric for the terminal devices of the plurality of users, selects the terminal devices of one or more users that communicate with the wide-area cell base station via a service link, determines user scheduling for the wide-area cell regarding the allocation of radio resources on the time axis and the frequency axis for the selected terminal devices of the one or more users, and may communicate with the selected terminal devices of the one or more users via the service link based on the user scheduling information of the wide-area cell.

[0009] In the system, the selection metric used by the wide-area cell base station may be a metric using the orthogonality between the channel vector between the wide-area cell base station and the terminal device of a user located in the wide-area cell and the channel vector between the wide-area cell base station and the corresponding point on the ground or at sea corresponding to the direction of the null.

[0010] In the system, the selection metric used by the wide-area cell base station may be a metric using the separation distance and angular direction of the terminal device of a user located in the wide-area cell with respect to the service link antenna of the wide-area cell base station and the separation distance and angular direction of the corresponding point on the ground or at sea corresponding to the direction of the null with respect to the service link antenna of the wide-area cell base station.

[0011] In the system, when the spatial multiplexing number in the radio resources allocated to the selected terminal device of the user is less than the maximum spatial multiplexing number of the wide-area cell, communication with the remaining terminal devices of one or more users may be additionally allocated to the radio resources.

[0012] In the system, the wide-area cell base station may greedily and sequentially select one or more user terminal devices that communicate with the wide-area cell base station via a service link, using a plurality of selection metrics for each of the terminal devices of the plurality of users.

[0013] In the system, the wide-area cell base station may divide the terminal devices of the plurality of users located within the wide-area cell into a first group that uses radio resources forming the null and a second group that selectively uses radio resources that do not form one or more of the nulls, and for each group, individually determine the allocation of radio resources to the terminal devices of the users.

[0014] In the system, the wide-area cell base station may transmit the null scheduling information to the terrestrial cell base station, and the terrestrial cell base station receives the null scheduling information from the wide-area cell base station, determines the user scheduling of the terrestrial cell regarding the allocation of the terminal devices of the users in the radio resources on the time axis and the frequency axis based on the null scheduling information, and may communicate with the terminal devices of the users located within the terrestrial cell via a service link based on the user scheduling information of the terrestrial cell.

[0015] In the system, for each of the terminal devices of the plurality of users located within the terrestrial cell, the terrestrial cell base station calculates a selection metric for selecting a terminal device whose communication quality deteriorates due to the control of the null formation, selects one or more terminal devices that communicate with the terrestrial cell base station via a service link based on the calculation results of the selection metrics for the terminal devices of the plurality of users, and may determine the user scheduling of the terrestrial cell regarding the allocation of radio resources on the time axis and the frequency axis for the selected one or more terminal devices of the users.

[0016] In the system, the selection metric used in the terrestrial cell base station may be a metric using at least one of the channel state between the terrestrial cell base station and the terminal device of the user located in the terrestrial cell, the desired signal power of the terminal device of the user, and the SINR (signal-to-interference-plus-noise ratio) of the terminal device of the user.

[0017] In the system, the selection metric used in the terrestrial cell base station may be a metric using the separation distance and the angular direction of the terminal device of the user located in the terrestrial cell with respect to the service link antenna of the terrestrial cell base station.

[0018] In the system, the terrestrial cell base station may greedily and sequentially select one or more terminal devices of the users that communicate with the terrestrial cell base station via the service link using a plurality of selection metrics for each of the terminal devices of the plurality of users.

[0019] In the system, the terrestrial cell base station divides the terminal devices of the plurality of users located in the terrestrial cell into a first group that uses the radio resources in which the wide-area cell base station forms the null with respect to the local station, and a second group that uses the radio resources in which the wide-area cell base station does not form the null partially or entirely with respect to the local station, and for each group, may individually determine the allocation of radio resources to the terminal devices of the users.

[0020] In the system, a plurality of terrestrial cell base stations may be provided. The null scheduling information may include information on the allocation of the first radio resources that form the null for all of the plurality of terrestrial cell base stations, and information on the allocation of the second radio resources that selectively stop forming the null for each terrestrial cell base station. Each of the plurality of terrestrial cell base stations preferentially allocates the first radio resources to one or more terminal devices of the users based on the calculation results of the selection metrics for the terminal devices of the plurality of users, and after the allocation of the first radio resources is completed, may allocate the second radio resources to the remaining one or more terminal devices of the users.

[0021] In the system, a plurality of terrestrial cell base stations may be provided. The null scheduling information may include information on the allocation of first radio resources for forming the null for all of the plurality of terrestrial cell base stations, and information on the allocation of second radio resources for selectively stopping the formation of the null for each terrestrial cell base station. Each of the plurality of terrestrial cell base stations preferentially allocates the first radio resource and a specific second radio resource for which the null is formed for the station itself, to one or more user terminal devices based on the calculation result of the selection index for the plurality of user terminal devices. After the allocation of the first radio resource and the specific second radio resource is completed, the second radio resource may be allocated to the remaining one or more user terminal devices.

Brief Description of Drawings

[0022]

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Embodiment for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The system according to an embodiment described in this document forms cells toward the ground or the sea, and can perform MU-MIMO communication with a plurality of terminal devices (UEs) present in the cells using a multi-element array antenna. It is an aerial-staying type communication relay device (aerial PF) equipped with a relay communication station of a wide-area cell base station (for example, an aerial PF base station) that can be a flying object or a floating object. This communication system, when a ground cell (second cell) formed by an existing ground cell base station (ground BS) using the same frequency band is located within the aerial PF cell which is a wide-area cell (first cell), can suppress the interference from the relay communication station of the aerial PF to the ground cell by forming a null in the direction of the antenna of the ground cell base station or the ground cell from the relay communication station of the aerial PF. The communication system according to this embodiment is suitable for realizing a three-dimensional network of a next-generation mobile communication such as the fifth generation that can handle simultaneous connection to a large number of terminal devices and low latency.

[0024] In particular, in the system of this embodiment, by on / off switching control of the formation of a null in the direction from the relay communication station of the aerial PF to the antenna of the ground cell base station (ground cell), the occurrence of a coverage hole in the aerial PF cell (wide-area cell) when forming a null in the direction of the antenna of the ground cell base station or the ground cell from the relay communication station of the aerial PF to suppress interference can be suppressed, the deterioration of the communication quality of the terminal device of the user connected to the aerial PF cell can be reduced, and the frequency utilization efficiency of the entire system can be improved.

[0025] FIG. 1 is a schematic configuration diagram showing an example of the overall configuration of a communication system including an aerial PF (aerial staying type communication relay device) according to an embodiment. In FIG. 1, the aerial PF system constituting the communication system of the present embodiment is a high-altitude platform station (hereinafter also referred to as "aerial platform (aerial PF)" or "HAPS") as an aerial staying type communication relay device (radio relay device) mounted on a flying object or a floating object equipped with a relay communication station. (Also referred to as "high-altitude pseudo satellite", "stratospheric platform"). The aerial PF 10 is provided. The aerial PF 10 is located in an airspace at a predetermined altitude and forms a three-dimensional cell (hereinafter also referred to as "aerial PF cell" or "HAPS cell") 100C as a wide-area cell (first cell). The aerial PF 10 is a flying object or a floating object (for example, a solar plane, a flying boat, a drone, a balloon) that is controlled to float or fly in an airspace (floating airspace) at a predetermined altitude from the ground or the sea surface by autonomous control or external control, and is equipped with a relay communication station. Note that the aerial PF 10 that can function as an aerial staying type communication relay device may be an artificial satellite such as a low Earth orbit (LEO) satellite or a geostationary orbit (GEO) satellite equipped with a relay communication station. Further, the communication system of the present embodiment may include one or a plurality of terminal devices with which the aerial PF 10 communicates, or may include a gateway station (feeder station) described later.

[0026] The airspace where the aerial PF 10 is located is, for example, the airspace of the stratosphere at an altitude of 11 [km] or more and 50 [km] or less above the ground (or on water such as the sea or a lake). This airspace may be an airspace at an altitude of 15 [km] or more and 25 [km] or less where the weather conditions are relatively stable, and particularly may be an airspace at an altitude of approximately 20 [km].

[0027] Since the altitude of the stratospheric PF10 is lower than that of general artificial satellites and higher than that of base stations on the ground or at sea, it can ensure a high visibility rate while having a smaller propagation loss than satellite communication. Due to this feature, it is also possible to provide communication services from the stratospheric PF10 to a terminal device (mobile station) 61, which is a user device such as a cellular mobile terminal on the ground or at sea. By providing communication services from the stratospheric PF10, a large area that has been covered by a large number of base stations on the ground or at sea can be covered by a small number of stratospheric PF10s at once, which has the merit of being able to provide low-cost and stable communication services.

[0028] The relay communication station of the stratospheric PF10 forms an upper-air PF cell 100C capable of wireless communication with the UE61 by forming a beam for wireless communication with a user terminal device (hereinafter referred to as "UE" (user device)) toward the ground (or sea surface). The radius of the service area (also referred to as "upper-air PF service area") 100A composed of the footprint 100F of this upper-air PF cell 100C on the ground (or sea) is, for example, several tens [km] to 100 [km].

[0029] In this embodiment, the relay communication station of the stratospheric PF10 may form a plurality of three-dimensional cells (for example, 3 cells or 7 cells) and form a service area 100A composed of a plurality of footprints of the plurality of three-dimensional cells on the ground (or sea).

[0030] The communication system of this embodiment includes an aerial PF10 equipped with a relay communication station in the sky that constitutes a wide-area cell base station (hereinafter also referred to as "aerial PF base station" or "HAPS base station"), and a low-position ground cell base station (hereinafter referred to as "ground BS") 30 that forms a cell to be suppressed from interference and is located on the ground or at sea. In the example of FIG. 1, antennas of a plurality of low-position ground BSs 30 (hereinafter also referred to as "base station antennas") are located inside the aerial PF cell 100C, and inside a service area 100A composed of the footprint 100F of the three-dimensional cell 100C, a cell of the ground BS 30 (hereinafter also referred to as "ground cell") 300C that is smaller than the footprint 100F of the cell 100C is formed.

[0031] The aerial PF base station, which is a wide-area cell base station including the relay communication station mounted on the aerial PF10, and the ground BS (for example, eNodeB, gNodeB) 30 each use a wireless frame synchronized with each other and the same frequency band for wireless communication of the service link between the UE61, 65 located in their own cells 100C, 300C. The ground BS 30 may have a configuration in which a RRH (remote radio head) having a base station antenna and a BBU (baseband unit) are connected by an optical line. In this case, an RRH having a base station antenna is located at the position of the base station 30 in FIG. 1.

[0032] The relay communication station mounted on the aerial PF10 is, for example, a base station (for example, eNodeB, gNodeB) that wirelessly communicates with a gateway station (also referred to as "feeder station") 70 as a relay station having an antenna 71 facing the sky and connected to the core network of the mobile communication network 80 on the ground (or at sea) side. The relay communication station of the aerial PF10 is connected to the core network of the mobile communication network 80 via a feeder station 70 installed on the ground or at sea. The communication between the aerial PF10 and the feeder station 70 may be performed by wireless communication using radio waves such as microwaves, or may be performed by optical communication using laser light or the like.

[0033] The relay communication station (also referred to as the "radio relay station") mounted on the upper air PF10 may be a repeater-type relay communication station or a base station device-type relay communication station. The repeater-type relay communication station is combined with the base station device mounted on the feeder station 70 to form a wide-area cell base station. The base station device-type relay communication station functions as a wide-area cell base station.

[0034] The repeater-type relay communication station has, for example, a repeater and a frequency conversion device. The repeater has a low-noise amplifier that amplifies the received signal of the service link received via the service link antenna, a power amplifier that amplifies the transmission signal transmitted via the service link antenna, etc. The frequency conversion device performs conversion between the frequency of the service link and the frequency of the feeder link. The feeder station 70 has, for example, a base station device and a frequency conversion device. The base station device has a baseband processing device that processes the baseband signal of the service link, a communication interface unit for communicating with the core network via the backhaul line, etc. The frequency conversion device performs conversion between the frequency of the service link signal input / output to / from the base station device and the frequency of the feeder link signal.

[0035] The base station device-type relay communication station has, for example, a base station device and a feeder link transceiver. The base station device has a low-noise amplifier that amplifies the received signal of the service link, a power amplifier that amplifies the transmission signal transmitted via the service link antenna, a baseband processing device that processes the baseband signal of the service link, etc. The feeder link transceiver transmits and receives the signals of the backhaul line transmitted and received with the feeder station 70. The feeder station 70 transmits and receives the signals of the backhaul line transmitted and received with the relay communication station in the upper air.

[0036] The airborne PF10 may autonomously control its floating movement (flight) and the processing at the relay communication station by executing a control program with a control unit composed of a built-in computer or the like. For example, each airborne PF10 may acquire its own current position information (e.g., GPS position information), pre-stored position control information (e.g., flight schedule information), the position information of other airborne PFs located in the vicinity, etc., and autonomously control its floating movement (flight) and the processing at the relay communication station based on such information.

[0037] Also, the floating movement (flight) of the airborne PF10 and the processing at the relay communication station may be controllable by a management device (also referred to as a "remote control device") serving as a management device provided in a communication center or the like of the mobile communication network 80. The management device can be composed of, for example, a computer device such as a PC or a server. In this case, the airborne PF10 is incorporated with a control communication terminal device (e.g., a mobile communication module) so that it can receive control information from the management device and transmit various information such as monitoring information to the management device, and terminal identification information (e.g., IP address, phone number, etc.) is assigned so that it can be identified by the management device. The MAC address of the communication interface may be used for identifying the control communication terminal device. Also, the airborne PF10 may transmit monitoring information such as information regarding the floating movement (flight) of itself or the surrounding airborne PFs and the processing at the relay communication station, information regarding the state of the airborne PF10, and observation data obtained by various sensors to a predetermined transmission destination such as the management device. The control information may include the target flight route information of the airborne PF10. The monitoring information may include at least one of the current position of the airborne PF10, flight route history information, airspeed relative to the air, ground speed, and propulsion direction, the wind speed and wind direction of the airflow around the airborne PF10, and the air pressure and air temperature around the airborne PF10.

[0038] FIG. 2 is a perspective view showing an example of the airborne PF10 used in the communication system of the embodiment. The upper-air PF10 in Fig. 2 is a solar-plane type HAPS, and includes a main wing portion 101 with both longitudinal ends bent upward, and a plurality of motor-driven propellers 103 as propulsion devices of a bus power system at one end edge in the lateral direction of the main wing portion 101. On the upper surface of the main wing portion 101, a solar panel (hereinafter referred to as "solar panel") 102 as a solar power generation portion having a solar power generation function is provided. Further, at two locations in the longitudinal direction on the lower surface of the main wing portion 101, pods 105 as a plurality of equipment accommodation portions for accommodating mission equipment are connected via plate-shaped connecting portions 104. Inside each pod 105, a relay communication station 110 as mission equipment and a battery 106 are accommodated. Further, wheels 107 used at the time of takeoff and landing are provided on the lower surface side of each pod 105. The electric power generated by the solar panel 102 is stored in the battery 106, and the motor of the propeller 103 is rotationally driven by the electric power supplied from the battery 106, and wireless relay processing by the relay communication station 110 is executed.

[0039] Fig. 3 is a side view showing another example of the upper-air PF10 used in the communication system of the embodiment. The upper-air PF10 in Fig. 3 is an unmanned airship type HAPS, and since the payload is large, a large-capacity battery can be mounted. The upper-air PF10 includes an airship main body 201 filled with a gas such as helium gas for floating by buoyancy, a motor-driven propeller 202 as a propulsion device of a bus power system, and an equipment accommodation portion 203 for accommodating mission equipment. Inside the equipment accommodation portion 203, a relay communication station 110 and a battery 204 are accommodated. The motor of the propeller 202 is rotationally driven by the electric power supplied from the battery 204, and wireless relay processing by the relay communication station 110 is executed. Note that a solar panel having a solar power generation function may be provided on the upper surface of the airship main body 201, and the electric power generated by the solar panel may be stored in the battery 204.

[0040] In the following embodiments, an airborne communication relay device (aerial PF) that wirelessly communicates with the UE61 will be illustrated and described for the case of either the solar plane type HAPS or the unmanned airship type HAPS in FIG. 2. However, the following embodiments can be similarly applied to other airborne communication relay devices (aerial PF) other than HAPS.

[0041] Also, the links FL(F) and FL(R) between the aerial PF10 and the gateway station (hereinafter abbreviated as "GW station") 70 serving as a feeder station are referred to as "feeder links", and the link between the aerial PF10 and the UE61 is referred to as a "service link". In particular, the section between the aerial PF10 and the GW station 70 is referred to as the "radio section of the feeder link". Also, the downlink of the communication from the GW station 70 to the UE61 via the aerial PF10 is referred to as the "forward link" FL(F), and the uplink of the communication from the UE61 to the GW station 70 via the aerial PF10 is also referred to as the "reverse link" FL(R).

[0042] In the communication system of this embodiment, the duplexing method of the uplink and downlink of the wireless communication between the ground BS30 and the UE65 is not limited to a specific method. For example, it may be a Time Division Duplex (TDD) method or a Frequency Division Duplex (FDD) method. Also, the access method of the wireless communication between the ground BS30 and the UE65 is not limited to a specific method. For example, it may be an FDMA (Frequency Division Multiple Access) method, a TDMA (Time Division Multiple Access) method, a CDMA (Code Division Multiple Access) method, or an OFDMA (Orthogonal Frequency Division Multiple Access).

[0043] Similarly, the duplexing method for the uplink and downlink of the wireless communication with the UE 61 via the relay communication station 110 is not limited to a specific method. For example, it may be a time-division duplexing (TDD) method or a frequency-division duplexing (FDD) method. Also, the access method for the wireless communication with the UE 61 via the relay communication station 110 is not limited to a specific method. For example, it may be an FDMA method, a TDMA method, a CDMA method, or an OFDMA.

[0044] In addition, the wireless communication of the service link in this embodiment has functions such as diversity coding, transmission beamforming, and spatial division multiplexing (SDM), and uses a massive MIMO (Multiple-Input Multiple-Output) transmission method that performs multi-layer transmission using an array antenna having a large number of antenna elements. In particular, in this embodiment, in the downlink communication from the relay communication station in the sky PF10 to a plurality of UEs 61 within the cell, a MU-MIMO (Multi-User MIMO) technology that transmits signals to a plurality of different UEs 61 at the same time and the same frequency is used. By performing MU-MIMO transmission using an array antenna having a large number of antenna elements, it is possible to direct an appropriate beam for each UE 61 according to the communication environment of each UE 61, so that the communication quality of the entire cell can be improved. Also, since communication can be performed with a plurality of UEs 61 using the same radio resources (time and frequency resources), the system capacity can be expanded.

[0045] FIG. 4 and FIG. 5 are perspective views each showing an example of an array antenna 130 composed of multiple elements that can be used for the MU-MIMO transmission method in the sky PF10 of this embodiment.

[0046] The array antenna 130 in FIG. 4 has a flat antenna substrate, and antenna elements 130a such as a large number of patch antennas are two-dimensionally arranged in the axial directions perpendicular to each other along the planar antenna surface of the antenna substrate, and it is a planar array antenna.

[0047] The array antenna 130 in FIG. 5 has a cylindrical or columnar antenna substrate, and antenna elements 130a such as a number of patch antennas are arranged along the axial direction and the circumferential direction of the circumferential side surface as the first antenna surface of the antenna substrate. It is a cylinder-type array antenna. In the array antenna 130 of FIG. 5, as shown in the figure, antenna elements 130a such as a plurality of patch antennas may be arranged in a circular shape along the bottom surface as the second antenna surface. Further, the antenna substrate in FIG. 5 may be a polygonal cylinder-shaped or polygonal column-shaped antenna substrate.

[0048] Note that the shape of the array antenna 130, as well as the number, type, and arrangement of the antenna elements, are not limited to those illustrated in FIGS. 4 and 5.

[0049] FIG. 6 is an explanatory diagram showing problems in the case of performing beamforming in the MU-MIMO transmission method using the array antenna 130 of the sky PF10. In the service link SL between the array antenna 130 of the sky PF10 in FIG. 6 and the service area 100A (the footprint 100F of the cell 100C), using the MU-MIMO transmission method, according to the communication environment of each UE61, appropriate high-gain beams 100B(1) to 100B(4) are individually directed to each UE61(1) to 61(4), and beamforming is performed to compensate for the long-distance propagation loss and communicate, so that the communication quality can be improved. In particular, when using the MU-MIMO transmission method of communicating with a plurality of UEs 61 using the same radio resource (for example, the same time-frequency resource block (RB)) in the service link SL, the system capacity can be improved.

[0050] However, in an environment where the aerial PF10 and the ground BS30(1), 30(2) are mixed as shown in FIG. 6, when the aerial PF10 and the ground BS30(1), 30(2) use the same frequency band to communicate with the UEs61, 65 camping in each cell simultaneously, the downlink wireless transmission signal transmitted from the aerial PF10 may interfere with the service link communication (hereinafter also referred to as "communication of the ground system") between the ground BS30(1), 30(2) and the UEs65(1), 65(2) camping in the ground cells 300C(1), 300C(2). When this interference from the aerial PF10 occurs, the throughput of the communication between the ground BS30(1), 30(2) and the UE65 will decrease significantly.

[0051] In this embodiment, in the aerial PF10, based on the position information of the base station antennas of the ground BS, beamforming control of the aerial PF cell 100C is performed so that the null of the beam pattern (profile of the spatial distribution of the beam) faces the ground BS (antenna) where the antenna is located within the aerial PF cell 100C. Thereby, a desired signal is transmitted to each of the plurality of UEs61 camping in the aerial PF cell 100C by multi-beams, and the interference caused by the aerial PF10 to the communication of the ground system is suppressed without causing a significant deterioration in communication quality.

[0052] FIG. 7 is an explanatory diagram showing an example of the directive null formed from the aerial PF10 toward the ground BS (antenna) 30. As shown in FIG. 7, when forming the null 100N of the beam pattern from the array antenna 130 of the aerial PF10 toward the ground BS (antenna) 30 located within the aerial PF service area 100A, the interference from the aerial PF10 to the ground cell 300C can be reduced, and the interference caused by the aerial PF10 to the communication of the ground system can be suppressed. However, deterioration of the communication quality of the aerial PF10 cannot be avoided around the ground BS30, and there may be a coverage hole 100H where some of the UEs61' located within the aerial PF service area 100A cannot connect to the aerial PF10.

[0053] FIG. 8 is a diagram showing an example of a coverage hole 100H of an overhead PF cell (wide area cell) 100C that occurs around an antenna of a ground BS30 when forming a null of directivity from an overhead PF10. In the example of FIG. 8, a coverage hole 100H occurs in an area wider than the ground cell 300C, and a UE61 cannot connect to the overhead PF10 (overhead PF cell 100C), or the communication quality (SINR) between the UE61 and the overhead PF10 deteriorates. In particular, in FIG. 8, a UE61' located in a coverage hole 100H located outside the ground cell 300C cannot connect to either the ground BS30 (ground cell 300C) or the overhead PF10 (overhead PF cell 100C).

[0054] FIG. 9 is a diagram showing an example of a coverage hole 100H of an overhead PF cell (wide area cell) 100C that occurs around an antenna of a ground BS30 when performing null sweeping to change the direction of a null formed from an overhead PF10 toward a ground cell 300C. When performing null sweeping, the coverage hole 100H, which is an area where connection to the overhead PF10 (overhead PF cell 100C) is not possible or the communication quality (SINR) deteriorates, also changes with the direction of the null.

[0055] FIG. 10 is a diagram showing an example of the result of an area simulation (computer simulation) including a coverage hole of an overhead PF cell (wide area cell) 100C that occurs when forming a null from an overhead PF10 toward antennas of a plurality of ground BS30(1) to 30(3). In FIG. 10, the overhead PF10 is located above the center of the area of the overhead PF cell 100C and forms a null toward each of the ground cells (areas of white circles in the figure) of the plurality of ground BS30(1) to 30(3). Due to this null formation, the areas shown in high-density gray or black in the figure become coverage holes 100H with deteriorated SINR.

[0056] In this embodiment, in order to achieve co-frequency sharing between the aerial PF system using the aerial PF10 expected from the perspective of effective frequency utilization and the terrestrial system using the terrestrial BS30, the aerial PF10 and the terrestrial BS30 cooperate, and a switching control of null formation and a resource allocation control on the time axis, the frequency axis, or both axes are combined. As a result, the frequency utilization efficiency is improved without degrading the coverage area of the aerial PF10.

[0057] In the following description, the case where the aerial PF10 and the terrestrial BS30 each perform DL (downlink) communication with the UE will be mainly described. However, the switching control of null formation and the resource allocation control of this embodiment can be applied to each of the following multiple combinations A1 to A4 of DL (downlink) communication and UL (uplink) communication. Hereinafter, the UE61 of the user located in the aerial PF cell 100C and connected to the aerial PF10 is also referred to as an "aerial PF user", and the UE65 of the user located in the terrestrial cell 300C and connected to the terrestrial BS30 is also referred to as a "terrestrial BS user".

[0058] A1: The case where the aerial PF10 performs DL communication and the terrestrial BS30 performs DL communication (Main interference: interference from the aerial PF to the terrestrial BS user, interference from the terrestrial BS to the aerial PF user) A2: The case where the aerial PF10 performs UL communication and the terrestrial BS30 performs UL communication (Main interference: interference from the aerial PF user to the terrestrial BS, interference from the terrestrial BS user to the aerial PF) A3: The case where the aerial PF10 performs DL communication and the terrestrial BS30 performs UL communication (Main interference: interference from the aerial PF to the terrestrial BS, interference from the terrestrial BS user to the aerial PF user) A4: The case where the aerial PF10 performs UL communication and the terrestrial BS30 performs DL communication (Main interference: interference from the terrestrial BS to the aerial PF, interference from the aerial PF user to the terrestrial BS user)

[0059] In the aerial PF10 according to this embodiment, for example, as shown in Fig. 11(a), a null ON radio resource (hereinafter also referred to as "null ON resource") that forms a null on the time axis and the frequency axis and a null OFF radio resource (hereinafter also referred to as "null OFF resource") that does not form a null are allocated to perform on / off switching control of null formation.

[0060] When a null is formed in the null ON resource, as shown in Fig. 11(b), a directional null is formed from the aerial PF10 toward the antenna of the ground BS30 or the ground cell 300C. By forming this null, interference from the relay communication station of the aerial PF10 to the ground cell 300C can be suppressed. However, due to the formation of the null, there is a possibility that a coverage hole 100H may occur around the ground BS30. In this coverage hole 100H, there is a risk that communication degradation may occur, such as the UE61' located around the ground cell 300C being unable to connect to the aerial PF10 (aerial PF cell 100C), or the communication quality (SINR) between the UE61' and the aerial PF10 deteriorating. In particular, if the UE61' is located in an area outside the coverage of the ground cell 300C within the coverage hole 100H, the UE61' may not be able to connect to either the aerial PF cell 100C or the ground cell 300C.

[0061] In this embodiment, in order to reduce the communication degradation of the UE61' located around the ground cell 300C, as shown in Fig. 11(a), the switch is made from the null ON resource to the null OFF resource. When the formation of the null is stopped in the null OFF radio resource, as shown in Fig. 11(c), a wide-area aerial PF100 is formed without the occurrence of the coverage hole 100H. Therefore, the UE61' located around the ground cell 300C can connect to the aerial PF10 (aerial PF cell 100C), and the communication quality (SINR) with the aerial PF10 does not deteriorate.

[0062] FIG. 12 is a diagram showing an example of the result of area simulation (computer simulation) when null formation by the aerial PF10 according to the embodiment is stopped. As shown in FIG. 12, by stopping the formation of nulls by the aerial PF10, it is possible to suppress the occurrence of coverage holes (regions shown in high-concentration gray or black in FIG. 10 above) 100H with degraded SINR in the vicinity of each of the plurality of terrestrial BSs 30(1) to 30(3).

[0063] As shown in FIGS. 11(a) to 11(c) and FIG. 12, by allocating null ON resources and null OFF resources in the aerial PF10 and performing on / off switching control of null formation, the frequency utilization efficiency can be improved without impairing the coverage area of the aerial PF10, and it is possible to realize co-frequency sharing between the aerial PF system using the aerial PF10 and the terrestrial system using the terrestrial BS 30 from the viewpoint of effective frequency utilization.

[0064] [Outline of On / Off Switching Control of Null Formation on the Aerial PF Side] FIG. 13(a) is a diagram showing an example of the positional relationship between the antenna of the terrestrial BS 30 and the aerial PF user 61 in the case of null ON in the on / off switching control of null formation by the aerial PF10 according to the embodiment. FIG. 13(b) is a diagram showing an example of the positional relationship between the antenna of the terrestrial BS 30 and the aerial PF user 61 in the case of null OFF in the on / off switching control of null formation by the aerial PF10 according to the embodiment. In FIGS. 13(a) and 13(b), solid arrows indicate the beam directions of downlink (DL) communication from the aerial PF10 to each of the plurality of aerial PF users, and dashed arrows indicate the directions of nulls formed from the aerial PF10 toward each of the plurality of terrestrial BSs 30.

[0065] In the over-air PF10, null ON resources and null OFF resources are preset in the wireless frame. In the null ON resources, as shown in Fig. 13(a), the over-air PF10 forms nulls towards each of the multiple ground BS30s, and by forming these nulls, the interference from the over-air PF10 to the ground cells is suppressed. In the null OFF resources, as shown in Fig. 13(b), the over-air PF10 stops forming nulls so that an over-air PF user who is close to the antenna of the ground BS30 but not within the ground cell 300C can communicate with the over-air PF10.

[0066] Note that the over-air PF10 may be controlled to stop forming nulls towards all the ground BS30s in the null OFF resources, or may be controlled to stop forming nulls only towards some of the ground BS30s.

[0067] Also, the over-air PF10 calculates a selection metric for selecting an over-air PF user whose communication quality deteriorates due to null formation for each of the multiple over-air PF users, selects an over-air PF user who communicates with the over-air PF10 through a service link based on the calculation result of the selection metric, and may determine the user scheduling of the over-air PF cell 100C regarding the allocation of wireless resources on the time axis and the frequency axis for the selected over-air PF user.

[0068] [Cooperation Control between Over-air PF and Ground BS for Null ON / OFF] Fig. 14(a) is a diagram showing an example of the relationship between the direction of the nulls formed in the case of null ON in the on / off switching control of null formation by the over-air PF according to the embodiment, the direction of beamforming to the over-air PF user 61, and the positional relationship between the antenna of the ground BS and the terminal device of the ground BS user. Fig. 14(b) is a diagram showing an example of the relationship between the nulls whose formation is stopped in the case of null OFF in the on / off switching control of null formation by the over-air PF10 according to the embodiment, the beamforming to the over-air PF user 61, and the positional relationship between the antenna of the ground BS and the terminal device of the ground BS user.

[0069] In the case of null ON in Fig. 14(a), interference from the overhead PF10 can be suppressed by null formation by the overhead PF10. Therefore, the ground BS30 can also perform downlink (DL) communication with the ground BS user 65 located at the end of the ground cell 300C.

[0070] On the other hand, in the case of null OFF in Fig. 14(b), the interference from the overhead PF10 becomes large in the null OFF resource. Therefore, the ground BS30 also performs the allocation of ground BS users so as to reduce the influence of interference from the overhead PF10 by cooperative control with the overhead PF10. For example, the ground BS30 preferentially performs user allocation using the null ON resource, and controls to select a ground BS user located at the center of the ground cell where the received power of the desired signal is large when using the null OFF resource.

[0071] [An Example of Resource Allocation Control for Overhead PF] Fig. 15 is a diagram showing an example of the distribution of antennas of a plurality of ground BSs 30 located in the wide-area cell (overhead PF cell) 100C of the overhead PF10 according to the embodiment and a plurality of overhead PF users 61 located around the antennas of each ground BS30. In Fig. 15, within the overhead PF cell 100C, there are a first ground cell 300C(1) of the first ground BS30(1) (hereinafter referred to as "BS1" in the illustration of resource allocation) and a second ground cell 300C(2) of the second ground BS30(2) (hereinafter referred to as "BS2" in the illustration of resource allocation). A plurality of overhead PF users 61(1) to 61(6) (hereinafter referred to as users 1 to 6 in the illustration of user scheduling) are located around the first cell 300C(1), and a plurality of overhead PF users 61(7) to 61(9) (hereinafter referred to as users 7 to 9 in the illustration of user scheduling) are located around the second cell 300C(2).

[0072] FIG. 16 is a diagram showing an example of allocation of radio resources (null ON resources) for forming nulls for all antennas of a plurality of ground BSs from an aerial PF10 and radio resources (null OFF resources) for stopping null formation for antennas of a specific ground BS. In FIG. 16, a radio frame is composed of a total of 24 radio resources (hereinafter also referred to as "resources") to which three different frequencies are allocated on the frequency axis and eight slots are allocated on the time axis. The null OFF resources are composed of a total of eight resources to which eight slots continuous on the time axis are allocated to the same first frequency on the high frequency side, and are resources for stopping null formation for a specific ground BS among the plurality of ground BSs. The null ON resources are composed of a total of 16 resources to which eight slots are allocated to each of the other second and third frequencies, and are resources for forming nulls for all of the plurality of ground BSs.

[0073] FIG. 17 is a diagram showing an example of null scheduling for forming nulls for an antenna of a specific ground BS in the null OFF resources of FIG. 16. In each of the plurality of resources of the null OFF resources in FIG. 17, ground BSs for forming nulls from the aerial PF10 are indicated by bold characters BS1 and BS2 with high density. FIG. 18(a) is a diagram showing an example of null scheduling including null allocation for forming a null for an antenna of a first ground BS30(1) in the null OFF resources of FIG. 16. FIG. 18(b) is a diagram showing an example of null scheduling including null allocation for forming a null for an antenna of a second ground BS30(2) in the null OFF resources of FIG. 16. As shown in FIGS. 17, 18(a), and 18(b), for example, among the plurality of resources of the null OFF resources, in the resource of the leftmost first slot, no null is formed for either BS1 or BS2. Also, in the resource of the second slot, a null is formed only for BS2 and not for BS1. Also, in the resource of the third slot, a null is formed only for BS1 and not for BS2.

[0074] Note that the allocation of null ON resources and OFF resources in FIG. 16 and the null scheduling in FIGS. 17, 18(a), and 18(b) are merely examples, and other allocations of null ON resources and OFF resources and null scheduling may be determined.

[0075] For example, the null scheduling may be determined according to traffic information regarding at least one of the traffic of the service link in the aerial PF cell 100C and the traffic of the service link in the terrestrial cells 300C(1) and 300C(2). Also, the null scheduling may be determined according to user distribution information regarding at least one of the geographical distribution of the aerial PF users 61 in the aerial PF cell 100C and the geographical distribution of the terrestrial BS users in the terrestrial cells 300C(1) and 300C(2).

[0076] FIG. 19 is a diagram showing an example of user scheduling for performing service link communication between the aerial PF 10 and a plurality of aerial PF users 61 in the null OFF resources of FIG. 16. In FIG. 19, for example, among the plurality of resources of the null OFF resources, the resources of the first slot at the left end are allocated to the aerial PF users 1 and 7, the resources of the second slot are allocated to the aerial PF user 2, and the resources of the third slot are allocated to the aerial PF user 8.

[0077] Here, the aerial PF 10 may determine the user scheduling of the aerial PF users 61 by overlappingly allocating a plurality of aerial PF users 61 far from both the terrestrial BSs 30(1) and 30(2) to the same resource so that the spatial multiplexing in the radio resources between the aerial PF 10 and the aerial PF users 61 is less than or equal to the maximum spatial multiplexing of the aerial PF cell 100C.

[0078] In addition, in this embodiment, the units of the frequency domain and the time domain of the resources in the allocation of the null ON resources and the null OFF resources and the null allocation to each terrestrial BS may be the same as the resources in the scheduling of the high-altitude PF users. For example, the unit of the frequency domain of the above resources may be 12 subcarriers corresponding to a resource block in the fifth-generation mobile communication system, and the unit of the time domain of the above resources may be the minimum unit of scheduling such as a slot or an OFDM symbol in the fifth-generation mobile communication system.

[0079] Also, by increasing the unit of the resources in the above null allocation, the number of controls may be reduced and the load may be reduced. For example, the unit of the frequency domain of the above resources may be a group of a plurality of resource blocks, and the unit of the time domain of the above resources may be a group of a plurality of slots, a group of a plurality of subframes, a group of a plurality of radio frames, or the like. Also, the unit of the time domain of the above resources may be in the range of 1 ms to 10 minutes, or may be 10 ms, 100 ms, or 1 s.

[0080] [Example of Resource Control for Terrestrial BS] FIG. 20 is a diagram showing an example of the distribution of antennas of a plurality of terrestrial BSs 30(1), 30(2) located in a wide-area cell (high-altitude PF cell) 100C of the high-altitude PF10 according to the embodiment and a plurality of terrestrial BS users 65 located in terrestrial cells 300C(1), 300C(2) of each terrestrial BS. In FIG. 20, a plurality of terrestrial BS users 65 are located in each of the plurality of terrestrial cells 300C(1), 300C(2).

[0081] In FIG. 20, when only the information on the position of the null OFF resources in the radio frame is shared between the high-altitude PF10 and the plurality of terrestrial BSs 30(1), 30(2) (in the case of sparse cooperation), considering that a null is always formed in its own cell for the null ON resources and it is not known at which time and frequency of the null OFF resources the null is directed to its own cell, for example, user scheduling is performed according to the following steps S11 to S14.

[0082] S11: The ground BSs 30(1) and 30(2) each determine the users to be allocated so that the number of resources to be allocated is less than or equal to the number of resources to be allocated, considering traffic, channel conditions, etc.

[0083] S12: The ground BSs 30(1) and 30(2) each calculate a selection index for each ground BS user 65. Here, the selection index is an index for selecting a ground BS user whose communication quality deteriorates due to null formation control. The selection index is, for example, an index using at least one of the channel condition between the ground BS 30 and the ground BS user 65, the desired signal power of the ground BS user 65, and the SINR (signal-to-interference-plus-noise ratio) of the ground BS user 65. The selection index may be an index using the separation distance and angular direction of the ground BS user based on the ground cell BS 30.

[0084] S13: The ground BSs 30(1) and 30(2) each preferentially allocate resources from the null ON resources according to the calculation results of the selection indexes of the ground BS users.

[0085] S14: After the allocation of the null ON resources is completed by the ground BSs 30(1) and 30(2) respectively, the remaining ground BS users 65 are allocated to the null OFF resources. Since the probability of a large interference effect increases when allocated to the null OFF resources, the allocation to the null OFF resources is avoided as much as possible.

[0086] In FIG. 20, when sharing null scheduling information between the aerial PF10 and the plurality of ground BSs 30(1) and 30(2) (in the case of close cooperation), considering that a null is always formed in its own cell in the null ON resources and it is known at which time and frequency of the null OFF resources the null is directed to its own cell (see FIGS. 18(a) and 18(b)), user scheduling is performed, for example, according to the following procedures S21 to S24.

[0087] S21: The terrestrial BSs 30(1) and 30(2) each determine the users to be allocated so that the number of resources to be allocated is not more than the number of resources to be allocated, considering traffic, channel conditions, etc.

[0088] S22: The terrestrial BSs 30(1) and 30(2) each calculate a selection index for each terrestrial BS user 65. Here, the selection index is an index for selecting a terrestrial BS user whose communication quality deteriorates due to null formation control. The selection index is, for example, an index using at least one of the channel state between the terrestrial BS 30 and the terrestrial BS user 65, the desired signal power of the terrestrial BS user 65, and the SINR (signal-to-interference-plus-noise ratio) of the terrestrial BS user 65. The selection index may be an index using the separation distance and angular direction of the terrestrial BS user with respect to the terrestrial cell BS 30.

[0089] S23: The terrestrial BSs 30(1) and 30(2) each preferentially allocate resources from the null ON resources and the special resources (see FIGS. 18(a) and 18(b)) which are null OFF resources but the own cell has nulls, according to the calculation results of the selection indices of the terrestrial BS users.

[0090] S24: After the allocation of the null ON resources and the special resources is completed for the terrestrial BSs 30(1) and 30(2) respectively, the remaining terrestrial BS users 65 are allocated to the remaining resources of the null OFF resources.

[0091] [Configuration of the Entire System] FIG. 21 is an explanatory diagram showing an example of the overall configuration of a communication system having a ground base station database 82 according to an embodiment. In FIG. 21, the same parts as those in FIG. 1 described above are denoted by the same reference numerals, and the description thereof is omitted. Further, FIG. 21 shows a case where the relay communication station 110 mounted on the upper air PF10 is a base station device type relay communication station having a base station device, but the relay communication station 110 mounted on the upper air PF10 may be a repeater type relay communication station. In this case, base station devices are provided in the relay communication station 110 mounted on the upper air PF10 and the feeder station (gateway station) 70 on the ground, etc., and the wide area cell base station (upper air PF base station) includes the repeater type relay communication station mounted on the upper air PF10 and the base station device on the ground.

[0092] In FIG. 21, the upper air PF10 can notify the ground BS30 via the feeder station (gateway station) 70, the mobile communication network 80, and the backhaul line 81. Further, the upper air PF10 can access the ground base station database 82 via the feeder station (gateway station) 70 and the mobile communication network 80, and acquire information on the ground base station 30.

[0093] The upper air PF10 and the ground BS30 share, for example, information (hereinafter referred to as "notification information") I1 periodically notified from the upper air PF10 to the ground BS30 and information (hereinafter referred to as "DB information") I2 stored in the ground base station database 82.

[0094] The notification information I1 depends on the user scheduling algorithm of the ground base station 30, and is, for example, information (I1-1) related to null and information (I1-2) related to the upper air PF10.

[0095] The information (I1-1) related to null is information on null formation related to the own cell of the ground BS30, and is, for example, the following information (I1-1-1) to (I1-1-3). (I1-1-1) Label for specifying null (I1-1-2) Information on the position corresponding to null For example, information such as the latitude and longitude of the position of the null formation target facing the null on the ground or at sea, values in plane coordinates or polar coordinates, etc. (I1-1-3) Scheduling status of nulls by on / off control of null formation In the above loose cooperation, only the information of null OFF resources (resources facing the null in its own cell are not notified) In the above tight cooperation, the information of null OFF resources and the information of resources facing the null in its own cell among the null OFF resources where any null stops

[0096] The information (I1-2) regarding the over-air PF10 is, for example, the following information (I1-2-1) and (I1-2-2). (I1-2-1) Information regarding the aircraft of the over-air PF10 (for example, position information and attitude information of the aircraft) (I1-2-2) Information on parameters related to the communication of the over-air PF10 (for example, information on antenna configuration, information related to beamforming and null formation)

[0097] The information related to the above beamforming and null formation is, for example, the information of weights applied to the transmission signal or the reception signal, information regarding over-air PF users, and the codebook number when using a codebook.

[0098] The information I2 stored in the ground base station database 82 is the information referenced from the over-air PF10 and is, for example, the following information (I2-1) to (I2-3). (I2-1) Base station specifications such as the position coordinates, antenna height, transmission power, and cell radius of the ground BS30 (I2-2) Traffic demand (I2-1) Geographical distribution of users connected to the ground BS30 (changing according to time)

[0099] [Configuration of the relay communication station of the over-air PF] FIG. 22 is a block diagram showing an example of the main configuration of the base station device type relay communication station 110 mounted on the over-air PF10 in the system of FIG. 21. In FIG. 22, the relay communication station 110 includes an information acquisition unit 1101, a null scheduling unit 1102, a null switching control unit 1103, a null scheduling information transmission unit 1104, and a user scheduling unit 1105 for the over-air PF user 61.

[0100] The information acquisition unit 1101 accesses the ground base station database 82 via the feeder link FL, and acquires information regarding the ground base station 30 that forms the ground cell 300C overlapping with its own service area 100A (over-air PF cell 100C). The information acquisition unit 1101 may further acquire traffic information regarding at least one of the traffic of the service link in the over-air PF cell 100C and the traffic of the service link in the ground cell 300C. The information acquisition unit 1101 may further acquire user distribution information regarding at least one of the geographical distribution of the over-air PF users 61 present in the over-air PF cell 100C and the geographical distribution of the ground BS users present in the ground cell 300C.

[0101] Based on the information of the ground base station 30 acquired from the ground base station database 82, the null scheduling unit 1102 determines null scheduling regarding the assignment on the time axis and the frequency axis of the directive null formed toward the antenna of the ground base station 30 or the ground cell 300C. The null scheduling unit 1102 may determine the null scheduling based on the traffic information and the information regarding the ground base station 30. The null scheduling unit 1102 may determine the null scheduling based on the user distribution information and the information regarding the ground base station 30.

[0102] Based on the information of the above null scheduling, the null switching control unit 1103 controls the formation of the directive null.

[0103] The null scheduling information transmission unit 1104 notifies the null scheduling information to each of the ground base stations 30 via the feeder link FL and the mobile communication network 80.

[0104] The user scheduling unit 1105 of the over-air PF 10 calculates a selection index for selecting an over-air PF user 61 whose communication quality deteriorates due to the formation of a null for each of the plurality of over-air PF users 61 located in the over-air PF cell 100C. Based on the calculation results of the selection index for the plurality of over-air PF users 61, one or more over-air PF users 61 that communicate with the over-air PF 10 via the service link are selected, and user scheduling of the over-air PF cell 100C regarding the allocation of radio resources on the time axis and the frequency axis for the selected one or more over-air PF users 61 may be determined. The over-air PF 10 communicates with the selected one or more over-air PF users 61 via the service link based on the user scheduling information of the over-air PF cell 100C.

[0105] The selection index may be, for example, an index using the orthogonality between the channel vector between the over-air PF 10 and the over-air PF user 61 located in the over-air PF cell 100C and the channel vector between the over-air PF 10 and the corresponding point on the ground or sea corresponding to the direction of the null. Further, the selection index may be an index using the separation distance and angular direction of the over-air PF user 61 based on the over-air PF 10 or its service link antenna and the separation distance and angular direction of the corresponding point on the ground or sea corresponding to the direction of the null based on the over-air PF 10 or its service link antenna.

[0106] When the spatial multiplexing number in the radio resources between the over-air PF 10 and the selected over-air PF user 61 is less than the maximum spatial multiplexing number of the over-air PF cell 100C, the user scheduling unit 1105 of the over-air PF 10 may allocate the communication with the remaining one or more over-air PF users 61 to the radio resources in a duplicated manner.

[0107] The user scheduling unit 1105 of the overhead PF10 may greedily and sequentially select one or more overhead PF users 61 that communicate with the base station of the overhead PF10 via a service link, using a plurality of selection metrics for each of the plurality of overhead PF users 61.

[0108] The user scheduling unit 1105 of the overhead PF user may divide the plurality of overhead PF users 61 present in the overhead PF cell 100C into a first group that uses radio resources forming the null and a second group that selectively uses one or more radio resources that do not form the null, and for each group, individually determine the allocation of radio resources for the overhead PF user 61.

[0109] [Configuration of the Ground Base Station] FIG. 23 is a block diagram showing an example of the main configuration of the ground base station (ground BS) 30 in the communication system of FIG. 21. In FIG. 23, the ground base station 30 includes a null scheduling information receiving unit 3001 and a user scheduling unit 3002 for ground BS users. The null scheduling information receiving unit 3001 receives null scheduling information regarding its own ground base station 30 from the overhead PF10. The user scheduling unit 3002 for ground BS users determines the user scheduling of the ground cell 300C regarding the allocation of ground BS users 65 in the radio resources on the time axis and the frequency axis based on the null scheduling information. The ground base station 30 communicates with the ground BS users 65 present in the ground cell 300C via a service link based on the user scheduling information of the ground cell.

[0110] The user scheduling unit 3002 of the terrestrial BS 30 calculates a selection metric for selecting a terrestrial BS user whose communication quality deteriorates due to the control of null formation for each of a plurality of terrestrial BS users 65 located in the terrestrial cell 300C, and based on the calculation results of the selection metrics for the plurality of terrestrial BS users 65, selects one or more terrestrial BS users that communicate with the terrestrial BS 30 via a service link, and may determine user scheduling of the terrestrial cell regarding the allocation of radio resources on the time axis and the frequency axis for the selected one or more terrestrial BS users.

[0111] The selection metric may be a metric using at least one of the channel state between the terrestrial BS 30 and the terrestrial BS user 65, the desired signal power of the terrestrial BS user 65, and the SINR (signal-to-interference-plus-noise ratio) of the terrestrial BS user 65.

[0112] The selection metric may be a metric using the separation distance and the angular direction of the terrestrial BS user 65 with respect to the service link antenna of the terrestrial BS 30.

[0113] The user scheduling unit 3002 of the terrestrial BS 30 may sequentially select one or more terrestrial BS users 65 that communicate with the terrestrial BS 30 via a service link in a greedy manner using a plurality of selection metrics for each of the plurality of terrestrial BS users 65.

[0114] The user scheduling unit 3002 of the terrestrial BS 30 divides a plurality of terrestrial BS users 65 located in the terrestrial cell 300C into a first group that uses radio resources for which the wide-area cell base station (the aerial PF base station) forms the null with respect to its own station, and a second group that uses radio resources for which the wide-area cell base station (the aerial PF base station) does not form the null, either partially or entirely, with respect to its own station, and may separately determine the allocation of radio resources for the terrestrial BS users 65 for each group.

[0115] The user scheduling unit 3002 of the ground BS 30 may perform user scheduling according to the procedures of S11 to S14 in the case of the aforementioned loose cooperation, or may perform user scheduling according to the procedures of S21 to S24 in the case of the aforementioned tight cooperation.

[0116] [Link control flow] FIG. 24 is a flowchart showing an example of link control in the base station of the sky PF10 and the ground base station 30 when performing beamforming control and service link communication involving null formation in the communication system according to the embodiment.

[0117] In FIG. 24, the sky PF10 accesses the ground base station database 82 via the feeder link FL and acquires information about the ground base station 30 located within its service area 100A (sky PF cell 100C) (S101). The information to be acquired includes the coordinates, cell radius, user distribution, etc. of the ground base station 30.

[0118] Next, the sky PF10 determines the allocation of nulls (null scheduling) including the direction of the nulls and the null ON / OFF information on the time axis and frequency axis based on the information of the ground base station 30 acquired from the ground base station database 82 (S102).

[0119] Next, the sky PF10 notifies each ground BS 30 of the aircraft information of the sky PF10 and the null scheduling information via the feeder link FL and the mobile communication network (network) 80 (S103).

[0120] Next, the sky PF10 acquires user information necessary for selection indicators such as the channel state information between the sky PF user 61, the position information of the sky PF user 61, and the arrival angle of the received radio wave at the sky PF user 61 (S104).

[0121] Next, the airborne PF 10 selects the airborne PF user 61 that utilizes the null OFF resource based on selection metrics such as the aforementioned orthogonality, allocates the null OFF resource (S105), excludes the airborne PF user 61 to which the null OFF resource has been allocated from the null ON resource (S106), and determines user scheduling such that the remaining airborne PF users 61 are allocated to the null ON resource (S107).

[0122] Next, the airborne PF 10 determines whether to perform other interference reduction control (S108) in consideration of the UL-DL combination and interference amount between the airborne PF 10 and the ground BS 30. Here, the other interference reduction control is, for example, transmission power control in the uplink (UL).

[0123] The airborne PF 10 controls null formation (S109 - S111) for each ground BS 30 based on the null scheduling information determined above, and performs service link communication with the airborne PF user 61 based on the user scheduling information determined above (S112).

[0124] On the other hand, the ground BS 30 receives the aircraft information of the airborne PF 10 and the null scheduling information regarding its own cell transmitted from the airborne PF 10 (S201), and acquires user information necessary for selection metrics such as channel state information between the ground BS user 65, the position information of the ground BS user 65, and the angle of arrival of the received radio wave at the ground BS user 65 (S202).

[0125] Next, the ground BS 30 determines user scheduling such that it preferentially allocates to the ground BS users of its own cell from the null ON resource so that the airborne PF 10 is likely to occupy the null OFF resource (S204), and allocates the remaining ground BS users to the null OFF resource (S204) based on selection metrics such as the aforementioned channel state.

[0126] Next, the terrestrial BS 30 determines whether to perform other interference reduction control by considering the combination of UL and DL and the interference amount between the over-air PF 10 and the terrestrial BS 30 (S205). Here, the other interference reduction control is, for example, transmission power control in the uplink (UL), null forming by the terrestrial BS 30, and the like.

[0127] Based on the user scheduling information determined above, the terrestrial BS 30 performs service link communication with the terrestrial BS user 65 (S206).

[0128] [Examples of Null Assignment and Beam Control for Over-Air PF] In the system of this embodiment, the null assignment and beam control of the over-air PF 10 may be performed as follows. For example, the over-air PF 10 forms a plurality (Nn) of nulls while spatially multiplexing a plurality (Nu) of over-air PF users 61 for each radio resource. Here, a single null may cover the entire area of a plurality of terrestrial BS 30 areas (an area including a plurality of terrestrial cells 300C). Also, a plurality of nulls may be directed to the area of a single terrestrial cell 300C of the terrestrial BS 30. Also, the target area for null formation is not necessarily within the service area of the over-air PF 10. Also, weights for performing null formation using, for example, a pseudo inverse matrix or singular value decomposition may be calculated (see, for example, Tashiro et al., IEEE Access, vol. 10, pp. 55675 - 55693, May 2022). Also, the number (Nu) of spatial multiplexing may be changed according to the communication situation.

[0129] The over-air PF 10 may perform control to stop null formation of one or more nulls from among the plurality (Nn) of nulls. Also, depending on the null formation direction, there may be nulls for which switching control is not performed because the influence on the service area of the over-air PF 10 may be minor.

[0130] The over-air PF 10 may change the direction of the nulls in combination with null sweeping (see Japanese Patent No. 7534460).

[0131] FIG. 25(a) is a diagram showing an example of resource allocation for communication with a plurality of aerial PF users 61 in the aerial PF10 according to the reference example and for forming a plurality of nulls. FIGS. 25(b) and 25(c) are diagrams showing an example of resource allocation for communication with a plurality of aerial PF users 61 in the aerial PF10 according to the embodiment and for forming a plurality of nulls. Here, in order to improve the overall communication quality and fairness of the system, as variable parameters, the number Nr of resources (null ON resources) that form all nulls and the number Nr' of resources (null OFF resources) that do not form all or some of the nulls are introduced.

[0132] FIG. 25(a) is a reference example of resource allocation consisting only of null ON resources in the case where Nu (number of users) = 6, Nn (number of nulls) = 6, Nr (number of null ON resources) = 90, and Nr' (number of null OFF resources) = 10.

[0133] FIG. 25(b) is an example of null OFF resource allocation that stops null formation all at once in the case where Nu (number of users) = 6, Nn (number of nulls) = 6, Nr (number of null ON resources) = 90, and Nr' (number of null OFF resources) = 10. The resource allocation in FIG. 25(b) corresponds to the positional relationship between the ground BS30 and the aerial PF user 61 shown in FIGS. 13(a) and 13(b).

[0134] Note that the ratio of the number Nr of null ON resources to the number Nr' of null OFF resources may be determined based on information on the aerial PF10, the ground BS30, the aerial PF user 61, and the ground BS user 65. Also, the number Nr of null ON resources and the number Nr' of null OFF resources may be fixed, and the nulls selected by the null ON / OFF control may be repeated in a certain pattern. Also, the resources for performing the null OFF control may be continuous as shown in FIG. 25(b) or may be dispersed. Also, Nr and Nr' may be changed according to the communication demand that changes with day and night, etc., or the nulls selected by the null ON / OFF control may be changed each time.

[0135] Figure 25(c) shows an example of null OFF resource allocation that partially stops null formation when Nu (number of users) = 6, Nn (number of nulls) = 6, Nr (number of null ON resources) = 90, and Nr' (number of null OFF resources) = 10. The resource allocation in Figure 25(c) corresponds to the positional relationship between the ground BS 30 and the aerial PF user 61 shown in Figures 26(a), 26(b), and 26(c).

[0136] If nulls are stopped all at once in the null OFF resources, there will be a bias in the utilization of the degrees of freedom of the array antenna. Therefore, as shown in Figures 25(c), 26(a), 26(b), and 26(c), nulls may be partially stopped (partial null OFF). This partial null stop can also be referred to as null sweeping across multiple ground cells 300C.

[0137] In partial null OFF, the null allocation may be determined considering information such as the temporal changes or geographical distributions of the traffic demands of the aerial PF 10, the ground BS 30, and both of them. Here, for individual nulls, regarding whether to form or stop them, for example, the control may be as follows. · Change the null allocation to follow the changes in the densities of the aerial PF users 61 and the ground BS users 65 that change in units of several hours, such as day and night. · When the traffic demand is high at the ground BS 30, reduce the number of times nulls protecting that ground BS 30 are stopped. · Adjust so that nulls face multiple times in the direction where the ground BS users 65 are concentrated. · When there are many aerial PF users 61 around the ground cell 300C, increase the number of null stops.

[0138] In the resource allocation of partial null OFF, with the number of null ON resources Nr = 0, some nulls may always be stopped.

[0139] Also, in the resource allocation of partial null OFF, the number of nulls to be stopped is not necessarily constant in the null OFF resources.

[0140] Also, in the partial null-OFF resource allocation, the nulls formed by the null-OFF resources may be selected as a combination of nulls with less degradation to the service area considering the orthogonality of the channel vectors and the like. Here, the nulls may be selected so that they are dispersed within the area so that the channel vectors are orthogonal. Also, in order to improve the communication quality of the over-air PF user 61 surrounded by a plurality of nulls, the nulls formed by the null-OFF resources may be selected so that a plurality of adjacent nulls are stopped simultaneously.

[0141] Note that in FIGS. 25(a) to 25(c), even if the user numbers are the same between different resources, they are not necessarily the same user.

[0142] [Example of Resource Allocation Control on the Over-Air PF Side] The selection of the over-air PF user at the time of null-OFF may be performed, for example, as follows. It is necessary to select a user near the null that is degraded by the null. Therefore, the over-air PF 10 may select the over-air PF user at the time of null-OFF using a selection index using the orthogonality (see the following equation (1)) between the channel vector between the over-air PF and the over-air PF user 61 and the channel vector in the direction of the null n. [Equation]

[0143] Here, in the above equation (1), [Equation] is the channel vector between the over-air PF and the over-air PF user u, and [Equation] is the channel vector between the over-air PF and the null n.

[0144] Regarding the formula (1) for the orthogonality degree, equivalent formula transformations or transformations that do not change the magnitude relationship such as taking the square root may be performed. Also, only the orthogonality degree with a single null may be used as a selection criterion, or the orthogonality degrees with multiple nulls may be included in the selection criterion. Further, when considering the orthogonality degrees with multiple nulls, an orthonormal system may be created from the channel vectors corresponding to the multiple nulls based on the Gram - Schmidt orthonormalization method, and the orthogonality degrees between them and the channel vector of the over - air PF user 61 may be used as the selection criterion.

[0145] Also, when the position information of the over - air PF user 61 and the information on the arrival angle of the received radio wave can be obtained, selection criteria based on the position of the over - air PF user 61 and the ground target position corresponding to the null direction, such as the distance or direction based on the position of the over - air PF 10, may be used.

[0146] Also, after selecting the over - air PF users 61 near the null, if there is room in the spatial multiplexing number, the remaining over - air PF users may be selected. At this time, it may be used in combination with an existing algorithm, or user selection may be performed using the orthogonality degree with the null or the selected over - air PF users.

[0147] Also, usually, the channel vector

Number

[0148] [Example of Algorithm for User Scheduling of Over - air PF] The aerial PF10 may greedily select an aerial PF user 61 with a low orthogonality to the null n as shown below. For example, in a situation where one user is selected only once (the process ends when the set of waiting users becomes an empty set), when Nn (the number of nulls) ≤ Nu (the number of users) and null formation is stopped all at once, the aerial PF user 61 may be selected by the algorithm in FIG. 27, and when Nn (the number of nulls) > Nu (the number of users) and Nu nulls are turned off, the aerial PF user 61 may be selected by the algorithm in FIG. 28, for example. However, 1 ≤ r ≤ Nr are null ON resources, and Nr < r ≤ Nr + Nr' are null OFF resources. Here,

Number

Number

[0149] [Example of Cooperative Control between Aerial PF and Ground BS for Null ON / OFF] The selection of users may be performed as follows, for example, by the cooperative control between the aerial PF and the ground BS.

[0150] For example, the aerial PF10 selects the aerial PF user 61 based on the aforementioned selection index.

[0151] Also, for example, the ground BS30 allocates the ground BS user 65 as exemplified below to reduce the impact of null formation stop. · Preferentially utilize null ON resources. Do not share null OFF resources depending on traffic demand. · For example, allocate users with poor channel conditions from null ON resources, and allocate only users with relatively good conditions to null OFF resources. ·As a selection metric, use SINR etc. that also takes into account channel state, desired signal power, interference between terrestrial BSs (or between sectors), etc. If information on the angle of arrival of the received radio wave and position information can be obtained, these pieces of information may be used as the selection metric.

[0152] Both the aerial PF10 and the terrestrial BS30 may greedily and sequentially select users using the aforementioned selection metric.

[0153] In the cooperative control between the aerial PF and the terrestrial BS, both the aerial PF10 and the terrestrial BS30 may select users using existing scheduling algorithms in combination. For example, after dividing users into groups that use null ON / OFF resources according to the selection metric for user selection, an existing algorithm may be applied to select users. As existing algorithms, for example, proportional fairness, round robin, Semi-orthogonal user selection (see Yoo and Goldsmith, IEEE J. Sel. Areas Commun., vol. 24, pp. 528-542, Mar. 2006.), Angle-based user selection (see Tashiro et al., IEICE Trans. Commun., vol. E105-B, no. 4, pp. 449-460, Apr. 2022.) can be used.

[0154] [Examples of algorithms for user scheduling of terrestrial BS] The terrestrial BS30 may greedily select the terrestrial BS user 65 from the desired power. For example, in a situation where 1 user is selected only once (the process ends when the set of waiting users becomes an empty set), the terrestrial BS user 65 may be selected by the algorithm in Fig. 29. Here, Pu in the algorithm is the desired power of user u,

Equation

[0155] According to the embodiments of the present disclosure, when a terrestrial cell 300C formed by an antenna of a terrestrial BS30 using the same frequency band is located within a cell 100C formed from the aerial PF10 toward the ground or the sea, interference to the terrestrial cell 300C (terrestrial BS30) and a terrestrial BS user (UE) 65 connected to the terrestrial BS30 from the aerial PF10 can be suppressed.

[0156] Further, according to the embodiments of the present disclosure, when forming a directive null from the relay communication station 110 of the aerial PF10 toward the antenna of the terrestrial BS30 or the terrestrial cell 300C to suppress interference, the occurrence of a coverage hole 100H of the aerial PF cell (wide-area cell) 100C can be suppressed, deterioration of the communication quality of an aerial PF user 61 connected to the aerial PF cell 100C can be reduced, and the frequency utilization efficiency of the entire system can be improved.

[0157] The system of the present disclosure can provide a system that reduces deterioration of the communication quality of the aerial PF user 61 and achieves high frequency utilization efficiency without impairing the coverage area, and thus can contribute to the achievement of Sustainable Development Goal (SDG) 9, "Build the infrastructure for industry and innovation."

[0158] Note that the processing steps described in this specification and the components of relay communication stations, feeder stations, gateway stations, management devices, monitoring devices, remote control devices, servers, terminal devices (UE: user devices, mobile stations, communication terminals), base stations, and base station devices such as the aerial PF can be implemented by various means. For example, these steps and components may be implemented by hardware, firmware, software, or a combination thereof.

[0159] For hardware implementation, means such as a processing unit used to implement the above processes and components in an entity (e.g., a relay communication station, a feeder station, a gateway station, a base station, a base station device, a relay communication station device, a terminal device (UE: user device, 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 execute the functions described in this specification, computers, or combinations thereof.

[0160] Also, for firmware and / or software implementations, means such as a processing unit used to implement the above components may be implemented by a program (e.g., code such as a procedure, function, module, instruction, etc.) that executes the functions described in this specification. Generally, any computer / processor-readable medium that clearly embodies the firmware and / or software code may be used for the implementation of means such as a processing unit used to implement the above steps and components described in this specification. For example, the firmware and / or software code may be stored in a memory, for example, in a control device, and executed by a computer or a processor. The memory may be implemented inside the computer or the processor, or may be implemented outside the processor. Also, the firmware and / or software code may be stored in a computer / 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 PROM (EEPROM), flash memory, floppy (registered trademark) 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 also cause the computer or processor to execute the functional aspects described in this specification.

[0161] Also, the medium may be a non-transitory recording medium. Also, the code of the program only needs to be readable and executable by a computer, a processor, or other device or apparatus machine, and its form is not limited to a specific form. For example, the code of the program may be any of source code, object code, and binary code, or a mixture of two or more of these codes.

[0162] Also, the description of the embodiments disclosed in this specification is provided to enable those skilled in the art to manufacture 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 are applicable to other variations without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure should not be limited to the examples and designs described herein, but should be accorded the widest scope that admits to the principles and novel features disclosed herein.

Description of Reference Numerals

[0163] 10: Aerial stay type communication relay device (aerial PF) 30: Ground cell base station (ground base station, ground BS) 61: Aerial PF user 65: Ground BS user 70: Feeder station (GW station) 71: Antenna 80: Mobile communication network 81: Backhaul line 82: Ground base station database 100A: Service area 100B: Beam 100C: Aerial PF cell 100F: Footprint 100H: Coverage hole 100N: Null 110: Relay communication station 300C: Ground cell 1101: Information acquisition unit 1102: Null scheduling unit 1103: Null switching control unit 1104: Null scheduling information transmission unit 1105: User scheduling unit 3001: Null scheduling information reception unit 3002: User scheduling unit

Claims

1. A system comprising: a wide-area cell base station that forms a wide-area cell from a service link antenna of a relay communication station provided in an aircraft or a floating body located in the sky toward the ground or the sea; and a plurality of ground cell base stations that form ground cells from antennas arranged on the ground or the sea, wherein the wide-area cell base station and the plurality of ground cell base stations communicate service link communications in the same frequency band using wireless frames synchronized with each other in time, the wide-area cell base station acquires information regarding a plurality of ground cell base stations that form ground cells overlapping the wide-area cell, determines null scheduling including wireless resources that do not selectively form the directional nulls with respect to a specific ground cell base station regarding the assignment of the directional nulls formed toward the antenna of the ground cell base station or the ground cell on the time axis and the frequency axis, based on the information regarding the plurality of ground cell base stations, controls the formation of the directional nulls based on the null scheduling information including the wireless resources that do not selectively form the directional nulls with respect to the specific ground cell base station, characterized in that it is a system.

2. In the system of Claim 1, the wide-area cell base station acquires at least one of traffic information regarding the traffic of the service link in the wide-area cell and user distribution information regarding the geographical distribution of the terminal devices of the users present in the wide-area cell, determines the null scheduling based on at least one of the traffic information of the wide-area cell and the user distribution information of the wide-area cell and the information regarding the ground cell base station, characterized in that it is a system.

3. In the system of Claim 1, the wide-area cell base station acquires traffic information regarding at least one of the traffic of the service link in the wide-area cell and the traffic of the service link in the ground cell, determines the null scheduling based on the traffic information and the information regarding the ground cell base station, characterized in that it is a system.

4. In the system of Claim 1, the wide-area cell base station acquires user distribution information regarding at least one of the geographical distribution of the terminal devices of the users present in the wide-area cell and the geographical distribution of the terminal devices of the users present in the ground cell, Determining the null scheduling based on the user distribution information and the information regarding the terrestrial cell base station. A system characterized by this.

5. In the system of Claim 1, the wide area cell base station calculates a selection index for selecting a terminal device whose communication quality deteriorates due to the formation of the null for each of the terminal devices of a plurality of users present in the wide area cell, selects one or more terminal devices of users who communicate with the wide area cell base station via a service link based on the calculation results of the selection index for the terminal devices of the plurality of users, and determines the user scheduling of the wide area cell regarding the allocation of radio resources on the time axis and the frequency axis for the selected one or more terminal devices of users, communicates with the selected one or more terminal devices of users via a service link based on the user scheduling information of the wide area cell. A system characterized by this.

6. A system including a wide area cell base station that forms a wide area cell from a service link antenna of a relay communication station provided on a flying object or a floating object located in the air toward the ground or the sea, and one or more terrestrial cell base stations that form a terrestrial cell from an antenna arranged on the ground or the sea, wherein the wide area cell base station and the one or more terrestrial cell base stations communicate with each other via a service link in the same frequency band using wireless frames that are time synchronized with each other, the wide area cell base station acquires information regarding the terrestrial cell base station that forms a terrestrial cell overlapping the wide area cell, determines null scheduling regarding the allocation of the antenna of the terrestrial cell base station or the directional null formed toward the terrestrial cell on the time axis and the frequency axis based on the information regarding the terrestrial cell base station, controls the formation of the directional null based on the null scheduling information, the wide area cell base station calculates a selection index for selecting a terminal device whose communication quality deteriorates due to the formation of the null for each of the terminal devices of a plurality of users present in the wide area cell, selects one or more terminal devices of users who communicate with the wide area cell base station via a service link based on the calculation results of the selection index for the terminal devices of the plurality of users, and determines the user scheduling of the wide area cell regarding the allocation of radio resources on the time axis and the frequency axis for the selected one or more terminal devices of users. Based on the user scheduling information of the wide-area cell, perform communication of the service link with the terminal devices of the selected one or more users. A system characterized by the above. **Claim 7** In the system of Claim 6, The null scheduling is null scheduling that includes radio resources that do not selectively form the directional null for a specific terrestrial cell base station. A system characterized by the above. **Claim 8** In the system of Claim 6, The selection index is an index using the orthogonality between the channel vector between the wide-area cell base station and the terminal device of the user in the wide-area cell and the channel vector between the wide-area cell base station and the corresponding point on the ground or at sea corresponding to the direction of the null. A system characterized by the above. **Claim 9** In the system of Claim 6, The selection index is an index using the separation distance and angular direction of the terminal device of the user in the wide-area cell based on the service link antenna of the wide-area cell base station and the separation distance and angular direction of the corresponding point on the ground or at sea corresponding to the direction of the null based on the service link antenna of the wide-area cell base station. A system characterized by the above. **Claim 10** In the system of Claim 6, When the spatial multiplexing number in the radio resources assigned to the terminal device of the selected user by the wide-area cell base station is less than the maximum spatial multiplexing number of the wide-area cell, the remaining one or more terminal devices of other users are redundantly assigned to communicate with the radio resources. A system characterized by the above. **Claim 11** In the system of Claim 6, The wide-area cell base station greedily and sequentially selects one or more terminal devices that perform communication of the service link with the wide-area cell base station using a plurality of selection indexes for each of the terminal devices of the plurality of users. A system characterized by the above. **Claim 12** In the system of Claim 6, The wide-area cell base station divides the terminal devices of a plurality of users in the wide-area cell into a first group that uses the radio resources that form the null and a second group that selectively uses one or more radio resources that do not form the null, and individually determines the allocation of radio resources to the terminal devices of the users for each group. A system characterized by the above. **Claim 13** In any of the systems of Claims 1 to 12, The wide-area cell base station Transmit the null scheduling information to the terrestrial cell base station, The terrestrial cell base station, Receives the null scheduling information from the wide-area cell base station, Based on the null scheduling information, determines the user scheduling of the terrestrial cell regarding the allocation of user terminal devices in the radio resources on the time axis and the frequency axis, Based on the user scheduling information of the terrestrial cell, communicates with the terminal devices of the users located in the terrestrial cell via the service link, A system characterized by the above.

14. In the system of Claim 13, The terrestrial cell base station, For each of the terminal devices of a plurality of users located in the terrestrial cell, calculates a selection index for selecting a terminal device whose communication quality deteriorates due to the null formation control, Based on the calculation results of the selection indexes for the terminal devices of the plurality of users, selects one or more terminal devices of users that communicate with the terrestrial cell base station via the service link, and determines the user scheduling of the terrestrial cell regarding the allocation of radio resources on the time axis and the frequency axis for the selected one or more terminal devices of users, A system characterized by the above.

15. In the system of Claim 14, The selection index is an index using at least one of the channel state between the terrestrial cell base station and the terminal device of the user located in the terrestrial cell, the desired signal power of the terminal device of the user, and the SINR (signal-to-interference-plus-noise ratio) of the terminal device of the user, A system characterized by the above.

16. In the system of Claim 14, The selection index is an index using the separation distance and the angular direction of the terminal device of the user located in the terrestrial cell with respect to the service link antenna of the terrestrial cell base station, A system characterized by the above.

17. In the system of Claim 14, The terrestrial cell base station sequentially selects one or more terminal devices of users that communicate with the terrestrial cell base station via the service link in a greedy manner using a plurality of selection indexes for each of the terminal devices of the plurality of users, A system characterized by the above.

18. In the system of Claim 14, The terrestrial cell base station, Divide the terminal devices of a plurality of users within the terrestrial cell into a first group that uses only the radio resources for which the wide-area cell base station forms the null with respect to the local station, and a second group that uses radio resources for which the wide-area cell base station does not form the null partially or entirely with respect to the local station. For each of the groups, individually determine the allocation of radio resources to the terminal devices of the users. A system characterized by this.

19. In the system of claim 14, Comprising a plurality of terrestrial cell base stations, The null scheduling information includes information on the allocation of the first radio resources for which the null is formed for all of the plurality of terrestrial cell base stations, and information on the allocation of the second radio resources for which the formation of the null is selectively stopped for each terrestrial cell base station. Each of the plurality of terrestrial cell base stations, Based on the calculation result of the selection index for the terminal devices of the plurality of users, preferentially allocate the first radio resources to one or more terminal devices of the users. After the allocation of the first radio resources is completed, allocate the second radio resources to the remaining one or more terminal devices of the users. A system characterized by this.

20. In the system of claim 14, Comprising a plurality of terrestrial cell base stations, The null scheduling information includes information on the allocation of the first radio resources for which the null is formed for all of the plurality of terrestrial cell base stations, and information on the allocation of the second radio resources for which the formation of the null is selectively stopped for each terrestrial cell base station. Each of the plurality of terrestrial cell base stations, Based on the calculation result of the selection index for the terminal devices of the plurality of users, preferentially allocate the first radio resources and a specific second radio resource for which the null is formed with respect to the local station among the second radio resources to one or more terminal devices of the users. After the allocation of the first radio resources and the specific second radio resource is completed, allocate the second radio resources to the remaining one or more terminal devices of the users. A system characterized by this.

21. A system comprising a wide-area cell base station that forms a wide-area cell from a service link antenna of a relay communication station provided on an aerial vehicle or a floating body located in the air towards the ground or the sea, and one or more terrestrial cell base stations that form a terrestrial cell from an antenna arranged on the ground or the sea. The wide-area cell base station and the one or more terrestrial cell base stations communicate service link communications in the same frequency band using wireless frames that are time-synchronized with each other. The wide-area cell base station acquires information regarding terrestrial cell base stations that form terrestrial cells overlapping the wide-area cell, determines null scheduling regarding the assignment on the time axis and the frequency axis of the nulls formed toward the antennas of the terrestrial cell base stations or the directivity nulls formed toward the terrestrial cells based on the information regarding the terrestrial cell base stations, controls the formation of the directivity nulls based on the null scheduling information, The wide-area cell base station transmits the null scheduling information to the terrestrial cell base stations, The terrestrial cell base station receives the null scheduling information from the wide-area cell base station, determines terrestrial cell user scheduling regarding the assignment of user terminal devices in wireless resources on the time axis and the frequency axis based on the null scheduling information, communicates with the user terminal devices of the users present in the terrestrial cell via a service link based on the terrestrial cell user scheduling information, The terrestrial cell base station calculates a selection metric for selecting, for each of the terminal devices of a plurality of users present in the terrestrial cell, a terminal device whose communication quality deteriorates due to the control of the null formation, selects one or more user terminal devices that communicate with the terrestrial cell base station via a service link based on the calculation results of the selection metrics for the terminal devices of the plurality of users, and determines terrestrial cell user scheduling regarding the assignment of wireless resources on the time axis and the frequency axis for the selected one or more user terminal devices, The terrestrial cell base station divides the terminal devices of the plurality of users present in the terrestrial cell into a first group that uses only the wireless resources in which the wide-area cell base station forms the nulls with respect to the local station, and a second group that uses wireless resources in which the wide-area cell base station does not form the nulls, either partially or entirely, with respect to the local station, individually determines the assignment of wireless resources to the terminal devices of the users for each group, A system characterized by the above. A system comprising a wide-area cell base station that forms a wide-area cell from a service link antenna of a relay communication station provided in an aircraft or a floating body located in the sky toward the ground or the sea, and one or a plurality of terrestrial cell base stations that form terrestrial cells from antennas arranged on the ground or the sea, wherein the wide-area cell base station and the one or a plurality of terrestrial cell base stations communicate a service link in the same frequency band with wireless frames synchronized with each other, the wide-area cell base station acquires information on terrestrial cell base stations that form terrestrial cells overlapping the wide-area cell, determines null scheduling regarding the assignment on the time axis and the frequency axis of a null of directivity formed toward the antenna of the terrestrial cell base station or the terrestrial cell based on the information on the terrestrial cell base station, controls the formation of the directivity null based on the null scheduling information, the wide-area cell base station transmits the null scheduling information to the terrestrial cell base station, the terrestrial cell base station receives the null scheduling information from the wide-area cell base station, determines terrestrial cell user scheduling regarding the assignment of user terminal devices in wireless resources on the time axis and the frequency axis based on the null scheduling information, communicates with the user terminal devices of users present in the terrestrial cell based on the terrestrial cell user scheduling information, the terrestrial cell base station calculates a selection index for selecting a terminal device whose communication quality deteriorates due to the control of the null formation for each of a plurality of user terminal devices present in the terrestrial cell, selects one or a plurality of user terminal devices that communicate with the terrestrial cell base station based on the calculation results of the selection indexes for the plurality of user terminal devices, and determines terrestrial cell user scheduling regarding the assignment of wireless resources on the time axis and the frequency axis for the selected one or a plurality of user terminal devices, including a plurality of terrestrial cell base stations, the null scheduling information includes information on the assignment of first wireless resources for forming the null for all of the plurality of terrestrial cell base stations, and information on the assignment of second wireless resources for selectively stopping the formation of the null for each terrestrial cell base station, each of the plurality of terrestrial cell base stations Based on the calculation results of the selection index for the terminal devices of the plurality of users, preferentially allocate the first radio resource to one or more user terminal devices, After the allocation of the first radio resource is completed, allocate the second radio resource to the remaining one or more user terminal devices, A system characterized by the above.

23. A system comprising a wide-area cell base station that forms a wide-area cell from a service link antenna of a relay communication station provided on an aircraft or a floating body located in the air toward the ground or the sea, and one or more ground cell base stations that form a ground cell from an antenna arranged on the ground or the sea, The wide-area cell base station and the one or more ground cell base stations communicate the service link in the same frequency band with wireless frames synchronized with each other, The wide-area cell base station, Obtain information regarding a ground cell base station that forms a ground cell overlapping the wide-area cell, Based on the information regarding the ground cell base station, determine null scheduling regarding the allocation on the time axis and the frequency axis of the null of the directivity formed toward the antenna of the ground cell base station or the ground cell, Control the formation of the directivity null based on the null scheduling information, The wide-area cell base station, Transmit the null scheduling information to the ground cell base station, The ground cell base station, Receive the null scheduling information from the wide-area cell base station, Based on the null scheduling information, determine the user scheduling of the ground cell regarding the allocation of user terminal devices in the radio resources on the time axis and the frequency axis, Based on the user scheduling information of the ground cell, perform service link communication with the terminal devices of the users in the ground cell, The ground cell base station, For each of the terminal devices of the plurality of users in the ground cell, calculate a selection index for selecting a terminal device whose communication quality deteriorates due to the control of the null formation, Based on the calculation results of the selection index for the plurality of user terminal devices, select one or more user terminal devices that perform service link communication with the ground cell base station, and determine the user scheduling of the ground cell regarding the allocation of radio resources on the time axis and the frequency axis for the selected one or more user terminal devices, Comprising a plurality of the ground cell base stations, The null scheduling information includes information on the allocation of the first radio resources for forming the null for all of the plurality of terrestrial cell base stations, and information on the allocation of the second radio resources for selectively stopping the formation of the null for each terrestrial cell base station. Each of the plurality of terrestrial cell base stations based on the calculation result of the selection index for the plurality of user terminal devices, preferentially allocates one or more user terminal devices to the first radio resources and a specific second radio resource for which the null is formed for the own station among the second radio resources. After the allocation of the first radio resources and the specific second radio resource is completed, the second radio resources are allocated to the remaining one or more user terminal devices. A system characterized by the above.

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