JP2022165729A - Communication relay device, system, and program - Google Patents

Abstract

To direct a beam toward the ground or the sea from an airborne communication relay device to suppress beam interference with respect to an interference suppression target placed in a first cell.SOLUTION: A communication relay device forms a first cell on the ground or on the sea, and performs radio communication with a plurality of terminal devices existing in the first cell. The communication relay device controls beam forming such that the nulls of the beam pattern formed by the array antenna are directed to the antennas targeted for interference suppression on the basis of position information of an array antenna having a plurality of antenna elements forming a beam pattern composed of a plurality of beams in the first cell and an antenna targeted for interference suppression arranged at a position lower than the array antenna to perform downlink communication between the plurality of terminal devices.SELECTED DRAWING: Figure 7

Description

The present invention relates to suppression of interference in wide-area cells formed by airborne communication relay devices.

BACKGROUND ART Conventionally, there are known high-altitude platform stations (HAPS) (also referred to as “high-altitude pseudo satellites”) that can stay in the air while staying in the air (see, for example, Patent Document 1). . Also, as communication between an airborne communication relay device such as HAPS and a plurality of terminal devices (hereinafter also referred to as "UE") located in a cell formed by the airborne communication relay device , massive MIMO (hereinafter also referred to as “mMIMO”) transmission system communication is known. mmMIMO is a wireless transmission technology that achieves high-capacity, high-speed communication by transmitting and receiving data using an array antenna having a large number of antenna elements. Also, a transmission scheme in which beamforming is performed for each of a plurality of UEs at the same time is also called “MU (Multi User)-MIMO”. By performing MU-MIMO transmission using a multi-element array antenna, it is possible to direct appropriate beams for each UE according to the communication environment of each UE for communication, thereby improving the communication quality of the entire cell. Also, since communication with a plurality of UEs can be performed using the same radio resource (time/frequency resource), system capacity can be expanded.

U.S. Patent Application Publication No. 2016/0046387

In order to perform MU-MIMO communication between the above-mentioned airborne communication relay device and multiple UEs on the ground, it is necessary to direct a high-gain beam for each UE using a multi-element array antenna. There is a problem that the high-gain beam interferes with existing terrestrial base stations whose antennas are located in the cell and terrestrial cells including UEs connected to the terrestrial base stations. A similar problem arises when the target for suppressing beam interference from the above-mentioned airborne communication relay device (hereinafter referred to as "interference suppression target") is other than a terrestrial cell (terrestrial base station, UE) (for example, radio astronomical observation). station).

A communication relay device according to an aspect of the present invention forms a first cell on the ground or on the sea, and performs airborne communication in which wireless communication is performed with a plurality of terminal devices residing in the first cell. It is a relay device. This communication relay apparatus includes an array antenna having a plurality of antenna elements forming a beam pattern composed of a plurality of beams in the first cell, and position information of an antenna targeted for interference suppression arranged at a position lower than the array antenna. means for performing downlink communication with the plurality of terminal devices by controlling beamforming so that the nulls of the beam pattern formed by the array antenna are directed to the interference suppression target antenna based on , provided.

In the communication relay device, forming a plurality of beams respectively directed to a plurality of terminal devices that are located in the first cell and connected to the communication relay device, and nulls in the beam pattern are the interference suppression targets. beamforming may be controlled to point to the antenna of

In the communication relay apparatus, a radio resource allocation unit that allocates a plurality of radio resources to be used for downlink communication with the plurality of terminal devices based on channel state information of the plurality of terminal devices; For each of the resources, a plurality of beams directed to each of a plurality of terminal devices are formed, and beamforming control is performed so that nulls of the beam pattern are directed to the interference suppression target antenna, and a transmission signal in the frequency domain a plurality of frequency domain beamforming controllers for generating .

In the communication relay apparatus, a radio resource allocation unit that allocates a plurality of radio resources to be used for downlink communication with the plurality of terminal devices based on channel state information of the plurality of terminal devices; a plurality of frequency-domain beamforming control units that perform beamforming control so as to form a plurality of beams directed to each of a plurality of terminal devices for each of the resources, and generate frequency-domain transmission signals; A time-domain beam for generating a time-domain transmission signal converted from the frequency-domain transmission signal by performing beamforming control so that nulls of the beam pattern are directed to the interference suppression target antenna for the entire radio resource. a forming control unit;

In the communication relay device, the frequency-domain beamforming control unit generates a channel matrix between the array antenna and the antenna to be subjected to interference suppression, and uses the plurality of radio resources based on the channel matrix. calculating the beamforming weights for each, and for each of the plurality of terminal devices, based on the radio resources assigned to the terminal devices and the beamforming weights calculated for the radio resources, in the frequency domain of downlink signals may be generated.

In the communication relay device, so that the plurality of beams directed to the plurality of terminal devices do not interfere with each other, and each of the plurality of beams does not interfere with the base station antenna, The beamforming may be controlled.

The communication relay device may control the beamforming so that the SINR of the terminal device is maximized.

In the communication relay device, under the condition that each of the plurality of beams directed to the plurality of terminal devices does not interfere with the base station antenna, the SINR of the terminal device is maximized. Beamforming may be controlled.

In the communication relay device, first beamforming control for directing a beam to each of the plurality of terminal devices and second beamforming control for directing a null of the beam pattern to the base station antenna are performed independently of each other. good too.

In the communication relay apparatus, the antenna to be subjected to interference suppression is arranged at a position lower than the array antenna, and uses the same frequency band as the first cell to form a second cell within the first cell. or an antenna of a radio astronomical observation station placed at a position lower than the array antenna.

A system according to another aspect of the present invention includes any one of the communication relay devices, and a terminal device that performs MU-MIMO wireless communication with the communication relay device.

A program according to still another aspect of the present invention resides in the first cell via an array antenna having a plurality of antenna elements forming a beam pattern composed of a plurality of beams in the first cell toward the ground or the sea. It is a program executed by a computer or processor provided in an airborne communication relay device that performs wireless communication with a plurality of terminal devices within range. This program performs beamforming so that the nulls of the beam pattern formed by the array antenna are directed toward the object of interference suppression, based on the positional information of the antennas to be subjected to interference suppression arranged at positions lower than the array antenna. and program code for performing downlink communication with the plurality of terminal devices.

Advantageous Effects of Invention According to the present invention, it is possible to suppress beam interference with respect to an interference suppression target arranged in a first cell formed toward the ground or the sea from an airborne communication relay device.

1 is a schematic configuration diagram showing an example of the overall configuration of a communication system including HAPS according to an embodiment; FIG. The perspective view which shows an example of HAPS of embodiment. The side view which shows the other example of HAPS of embodiment. FIG. 2 is a perspective view showing an example of an array antenna for a service link of HAPS according to the embodiment; FIG. 4 is a perspective view showing another example of the array antenna for the HAPS service link of the embodiment; FIG. 2 is an explanatory diagram showing a problem when performing beamforming in MU-MIMO using an HAPS array antenna; FIG. 4 is an explanatory diagram showing an example of beamforming in MU-MIMO using the HAPS array antenna according to the embodiment; FIG. 4 is an explanatory diagram showing an example of allocation of radio resources for downlink communication to each UE in HAPS according to the embodiment; FIG. 2 is an explanatory diagram showing an example of a communication model of downlink communication between a HAPS relay communication station and a plurality of UEs to which the same radio resource is allocated according to the embodiment; FIG. 4 is an explanatory diagram showing an example of a ZF beamforming method in beamforming control according to the embodiment; FIG. 4 is an explanatory diagram showing an example of an MMSE beamforming method in beamforming control according to the embodiment; FIG. 4 is an explanatory diagram showing an example of a hybrid beamforming method in beamforming control according to the embodiment; FIG. 4 is an explanatory diagram showing an example of a separate beamforming method in beamforming control according to the embodiment; 1 is a block diagram showing an example of the main configuration of a HAPS relay communication station according to an embodiment; FIG. FIG. 15 is a block diagram showing an example of the main configuration of a base station processing unit in the relay communication station of FIG. 14; FIG. 16 is an explanatory diagram showing an example of radio resource allocation in the case of full digital BF in the base station processing unit of FIG. 15; FIG. 15 is a block diagram showing another example of the main configuration of the base station processing unit in the relay communication station of FIG. 14; FIG. 18 is an explanatory diagram showing an example of radio resource allocation in the case of hybrid BF in the base station processing unit of FIG. 17;

Embodiments of the present invention will be described below with reference to the drawings.
The system according to the embodiments described in this document forms a cell on the ground or on the sea, and uses a multi-element array antenna between a plurality of terminal devices (UE) located in the cell and MU- A terrestrial cell (second cell) formed by an existing terrestrial base station that uses the same frequency band in the HAPS cell (first cell) and radio astronomy, which is equipped with a high-flying communication relay device (HAPS) that performs MIMO communication. A communication system (HAPS system) that can suppress interference from HAPS to interference suppression targets such as terrestrial cells (terrestrial base stations and UEs connected to terrestrial base stations) when interference suppression targets such as observation stations are located. is. The communication system according to the present embodiment is suitable for realizing a three-dimensional network for next-generation mobile communication such as the fifth generation that supports simultaneous connection to a large number of terminal devices and low delay.

FIG. 1 is a schematic configuration diagram showing an example of the overall configuration of a communication system including a HAPS (aerial communication relay device) according to an embodiment. In FIG. 1, the communication system of the present embodiment (hereinafter also referred to as "HAPS system") includes a high altitude platform station (HAPS) as a communication relay device (radio relay device) that stays in the sky, ("high altitude pseudo satellite ”, also referred to as “stratospheric platform”) 10 . The HAPS 10 forms a three-dimensional cell (hereinafter also referred to as "HAPS cell") 100C as a first cell located in an airspace at a predetermined altitude. HAPS 10 is a floating body (for example, solar plane, airship, drone, balloon) that is controlled to float or fly in an airspace (floating airspace) at a predetermined altitude from the ground or sea surface by autonomous control or external control. is equipped with a relay communication station. Note that the airborne communication relay device may be one in which a relay communication station is mounted on an artificial satellite. Moreover, the communication system of this embodiment may include one or more terminal devices with which the HAPS 10 communicates, and may include a gateway station (feeder station) described later.

The airspace in which the HAPS 10 is located is, for example, a stratospheric airspace at an altitude of 11 [km] or more and 50 [km] or less above the ground (or above 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 in which weather conditions are relatively stable, and may be an airspace at an altitude of approximately 20 [km].

HAPS is lower than the flight altitude of general artificial satellites and flies higher than base stations on the ground or on the sea, so it is possible to secure a high visibility rate with less propagation loss than satellite communications. From this feature, it is also possible to provide communication services from HAPS to a terminal device (mobile station) 61, which is a user device such as a cellular mobile terminal on the ground or on the sea. By providing communication services from HAPS, it is possible to cover a wide area with a small number of HAPS at once, which was previously covered by a large number of base stations on the ground or on the sea. be.

The relay communication station of HAPS 10 can wirelessly communicate with UE 61 by forming a beam toward the ground (or sea surface) for wirelessly communicating with a user's terminal device (hereinafter referred to as "UE" (user device)). to form a single HAPS cell 100C. The radius of the service area 100A consisting of the footprint 100F on the ground (or sea) of the HAPS cell 100C is, for example, several tens [km] to 100 [km].

In addition, in this embodiment, the relay communication station of HAPS 10 forms a plurality of three-dimensional cells (for example, three cells or seven cells), and from a plurality of footprints on the ground (or sea) of the plurality of three-dimensional cells A service area 100A may be formed.

The communication system of the present embodiment includes HAPS 10, which is a communication relay device that stays in the air, and a low-position base station (hereinafter referred to as a "terrestrial base station") 30 that forms a cell that is an object of interference suppression and is located on the ground or on the sea. are in a mixed environment. In the example of FIG. 1, a plurality of antennas of ground base stations 30 (hereinafter also referred to as "base station antennas") are located in a low position inside the HAPS cell 100C, and a service consisting of a three-dimensional footprint 100F of the cell 100C. Inside the area 100A, a cell (hereinafter referred to as "terrestrial cell") 300C of the terrestrial base station 30 smaller than the footprint 100F of the cell 100C is formed. HAPS 10 and terrestrial base station (e.g., eNodeB, gNodeB) 30 use the same frequency band for service link radio communication with UEs 61 and 65 located in their own cells 100C and 300C, respectively. The ground base station 30 may have a configuration in which an 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 with a base station antenna is located at the position of the base station 30 in FIG.

The relay communication station of the HAPS 10 is, for example, a gateway station (also referred to as a "feeder station") 70 as a relay station connected to the core network of the mobile communication network 80 on the land (or sea) side and having an antenna 71 facing the sky. A base station (eg, eNodeB, gNodeB) that wirelessly communicates with the . The relay communication stations of HAPS 10 are connected to the core network of mobile communication network 80 via feeder stations 70 installed on land or at sea. Communication between the HAPS 10 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.

HAPS 10 may autonomously control its own levitation movement (flight) and processing at the relay communication station by executing a control program by a control unit configured by a computer or the like incorporated therein. For example, each HAPS 10 acquires its own current position information (eg, GPS position information), pre-stored position control information (eg, flight schedule information), position information of other HAPS located in the vicinity, etc., and such information Based on this, floating movement (flight) and processing at the relay communication station may be autonomously controlled.

Also, floating movement (flight) of the HAPS 10 and processing at the relay communication station can be controlled by a management device (also referred to as a "remote control device") as a management device provided in a communication center of the mobile communication network 80 or the like. can be The management device can be composed of, for example, a computer device such as a PC, a server, or the like. In this case, the HAPS 10 incorporates a control communication terminal device (for example, 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. Terminal identification information (for example, IP address, telephone number, etc.) may be assigned so that it can be identified from. The MAC address of the communication interface may be used to identify the control communication terminal device. In addition, the HAPS 10 sends monitoring information such as information on floating movement (flight) of itself or surrounding HAPS, processing at the relay communication station, information on the state of the HAPS 10, observation data obtained by various sensors, etc. to a management device or the like. You may make it transmit to a predetermined transmission destination. The control information may include HAPS target flight route information. The monitoring information includes at least one of current position of HAPS 10, flight route history information, airspeed, ground speed and direction of propulsion, wind speed and direction of airflow around HAPS 10, and air pressure and temperature around HAPS 10. It's okay.

FIG. 2 is a perspective view showing an example of HAPS 10 used in the communication system of the embodiment.
The HAPS 10 in FIG. 2 is a solar plane type HAPS, and includes a main wing portion 101 having both longitudinal end portions curved upward, and a plurality of propulsion devices as a bus power system propulsion device at one end portion of the main wing portion 101 in the short side direction. and a motor-driven propeller 103 . A photovoltaic power generation panel (hereinafter referred to as “solar panel”) 102 is provided on the upper surface of the main wing portion 101 as a photovoltaic power generation portion having a photovoltaic power generation function. In addition, pods 105 serving as a plurality of equipment housing sections for housing mission equipment are connected via plate-shaped connecting sections 104 to two locations in the longitudinal direction of the lower surface of the main wing section 101 . Inside each pod 105, a relay communication station 110 as a mission device and a battery 106 are accommodated. Wheels 107 are provided on the underside of each pod 105 for use during takeoff and landing. The power generated by the solar panel 102 is stored in the battery 106, the power supplied from the battery 106 rotates the motor of the propeller 103, and the relay communication station 110 performs wireless relay processing.

FIG. 3 is a perspective view showing another example of HAPS 10 used in the communication system of the embodiment. The HAPS 10 shown in FIG. 3 is an unmanned airship type HAPS, and since it has a large payload, it can be equipped with a large-capacity battery. The HAPS 10 comprises an airship body 201 filled with a gas such as helium gas for floating by buoyancy, a motor-driven propeller 202 as a propulsion device for a bus power system, and an equipment housing section 203 for housing mission equipment. Prepare. The relay communication station 110 and the battery 204 are accommodated inside the device accommodation unit 203 . The electric power supplied from the battery 204 drives the motor of the propeller 202 to rotate, and the relay communication station 110 performs wireless relay processing. A solar panel having a photovoltaic power generation function may be provided on the upper surface of the airship body 201 , and the power generated by the solar panel may be stored in the battery 204 .

In the following embodiment, the case where the airborne communication relay device that wirelessly communicates with the UE 61 is either the solar plane type HAPS 10 or the unmanned airship type HAPS 20 shown in FIG. The unmanned airship type HAPS 10 shown in FIG. 3 may be used as the airborne communication relay device. In addition, the following embodiments can be similarly applied to other airborne communication relay devices other than the HAPS 10 .

Links FL(F) and FL(R) between HAPS 10 and a gateway station (hereinafter abbreviated as "GW station") 70 as a feeder station are called "feeder links", and links between HAPS 10 and UE 61 are referred to as "feeder links". is called "Service Link". In particular, a section between the HAPS 10 and the GW station 70 is called a "feeder link radio section". Further, the downlink of communication from GW station 70 to UE61 via HAPS10 is called "forward link" FL(F), and the uplink of communication from UE61 to GW station 70 via HAPS10 is called "reverse link". Also called FL(R).

In the communication system of the present embodiment, the uplink and downlink duplexing schemes for wireless communication between the ground base station 30 and the UE 65 are not limited to specific schemes, and may be Time Division Duplex (TDD), for example. ) method or a frequency division duplex (FDD) method. In addition, the access method for wireless communication between the ground base station 30 and the UE 65 is not limited to a specific method, and may be, for example, FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), or CDMA (Code Division Multiple Access). Access) method or OFDMA (Orthogonal Frequency Division Multiple Access).

Similarly, the uplink and downlink duplexing schemes for wireless communication with the UE 61 via the relay communication station 110 are not limited to a specific scheme. A division duplex (FDD) system may also be used. Also, the access method for radio communication with the UE 61 via the relay communication station 110 is not limited to a specific method, and may be FDMA, TDMA, CDMA, or OFDMA, for example.

In addition, for the wireless communication of the service link of the present embodiment, an array antenna having functions such as diversity coding, transmission beamforming, spatial division multiplexing (SDM: Spatial Division Multiplexing) and having a large number of antenna elements is used. A massive MIMO (Multiple-Input Multiple-Output) transmission system is used for multi-layer transmission. In particular, in the present embodiment, in the downlink communication from the relay communication station of HAPS10 to a plurality of UE61 in the cell, MU-MIMO (Multi-User MIMO) for transmitting signals at the same time and the same frequency to a plurality of different UE61 using technology. By performing MU-MIMO transmission using an array antenna having a large number of antenna elements, an appropriate beam can be directed to each UE61 according to the communication environment of each UE61 for communication, so the communication quality of the entire cell can be improved. Moreover, since communication with a plurality of UEs 61 can be performed using the same radio resource (time/frequency resource), the system capacity can be expanded.

4 and 5 are perspective views showing an example of an array antenna 130 composed of multiple elements that can be used for the MU-MIMO transmission system in the HAPS 10 of this embodiment.

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

The array antenna 130 of FIG. 5 has a cylindrical or columnar antenna base, and a large number of patch antennas or the like are arranged along the axial direction and the circumferential direction of the circumferential side surface as the first antenna surface of the antenna base. It is a cylindrical array antenna in which antenna elements 130a are arranged. In the array antenna 130 of FIG. 5, as illustrated, 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 base in FIG. 5 may be a polygonal tubular or polygonal cylindrical antenna base.

The shape of the array antenna 130 and the number, types and arrangement of antenna elements are not limited to those illustrated in FIGS.

FIG. 6 is an explanatory diagram showing a problem when performing beamforming in the MU-MIMO transmission system using the array antenna 130 of the HAPS 10. In FIG. In the service link SL between the array antenna 130 of the HAPS 10 and the service area 100A (footprint 100F of the cell 100C) in FIG. 1) to 61(4) are individually directed to appropriate high-gain beams 100B(1) to 100B(4) to compensate for long-distance propagation loss and perform beamforming for communication, thereby improving communication quality. can be improved. In particular, when using the MU-MIMO transmission scheme that communicates with multiple UEs 61 using the same radio resource (for example, the same time/frequency resource block (RB)) in the service link SL, the system capacity is improved. be able to.

However, in an environment where the HAPS 10 and the ground base stations 30(1) and 30(2) coexist as shown in FIG. 6, the HAPS 10 and the ground base stations 30(1) and 30(2) use the same frequency band. When communicating simultaneously with UEs 61 and 65 located in each cell, downlink radio transmission signals transmitted from HAPS 10 are transmitted from terrestrial base stations 30 (1) and 30 (2) and terrestrial cells 300C (1) and 300C ( 2) may interfere with service link communication (hereinafter also referred to as "terrestrial system communication") between UEs 65(1) and 65(2) located in the area. When this interference from HAPS 10 occurs, the throughput of communication between ground base stations 30(1), 30(2) and UE 65 is greatly reduced.

Therefore, in the present embodiment, in the HAPS 10, based on the position information of the base station antenna of the terrestrial base station, a beam pattern (profile of spatial distribution of beam) is generated for the terrestrial base station (antenna) located in the HAPS cell. Beamforming control of the HAPS cell is performed so that the null is directed. As a result, the interference caused by the HAPS 10 to the communication of the ground system is suppressed without causing a large deterioration in the communication quality of transmitting the desired signal by the multi-beam to each of the plurality of UEs 61 located in the HAPS cell. .

FIG. 7 is an explanatory diagram showing an example of beamforming in MU-MIMO using the HAPS array antenna according to the embodiment. In the example of FIG. 7, nulls in the beam pattern (beam spatial distribution profile) are directed toward each of the plurality of ground base stations (antennas) 30(1) and 30(2) located in the HAPS cell 100C. In addition, beam forming control is performed on the HAPS 10 side. This allows the transmission side to suppress the interference that HAPS 10 gives to the communications of the terrestrial systems of terrestrial base stations (antennas) 30(1) and 30(2). (2) and UEs 65(1), 65(2) in terrestrial cells 300C(1), 300C(2) can communicate normally. In addition, since the multi-beam that transmits the desired signal to each of the plurality of UEs 61 (1) to 61 (4) located in the HAPS cell is maintained, from the HAPS 10 to the plurality of UEs 61 (1) to 61 (4) A significant deterioration in communication quality of downlink communication does not occur.

Hereinafter, an example of beamforming control performed so that the nulls of the beam pattern in downlink communication from HAPS 10 according to the present embodiment to a plurality of UEs 61 (1) to 61 (4) are directed toward the ground base station will be described. do.

A processing flow of downlink communication involving beamforming control by the HAPS 10 of the present embodiment can be performed, for example, by the following steps 0 to 3.
Step 0: Preparation processing Step 1: Channel matrix generation processing Step 2: Weight calculation processing Step 3: Downlink communication processing

In the preparation process (step 0), the HAPS 10 acquires or estimates the channel state information (CSI) of all UEs (all users) 61 in the HAPS cell 100C performing downlink communication, and based on the acquisition result or estimation result , allocate radio resources to each UE (each user) 61 . For example, as shown in FIG. 8, based on the CSI of each UE61, all UE61 located in the HAPS cell 100C are divided into K groups of Nu UEs (users). Here, UEs (users) belonging to the same group to which the same radio resource is allocated are selected so that their directions from the HAPS 10 are different, for example. Also, Nu is the number of UEs 61 (number of UEs (number of users) per radio resource) allocated to the same radio resource (same RB) when performing MU-MIMO transmission. The value of Nu may be the same for each radio resource, or may be different for each radio resource.

In the channel matrix generation process (step 1), the HAPS 10 and each of the terrestrial base stations 30(1) and 30(2) are generated based on the positional information of each of the terrestrial base stations 30(1) and 30(2) by, for example, a method described later. 2), a channel matrix H _BS between is generated.

In the weight calculation process (step 2), for example, by any one of a _plurality of methods described later, weights (hereinafter also referred to as "BF weights") used for beamforming control in each radio resource are calculated using the channel matrix H between the UE (HAPS user) 61 determined for each radio resource based on .

In the downlink communication process (step 3), downlink communication is performed with each UE 61 in the HAPS cell 10 by a plurality of beams of a beam pattern formed by beamforming control performed using the BF weight. .

[Generation of channel matrix H _BS ]
The channel matrix HBS between the _HAPS 10 and each terrestrial base station 30 has, for example, location information about the location of the HAPS 10 itself, and the HAPS 10 has location information about the location of the terrestrial base station (base station antenna). On the premise that the location is present or can be estimated, the location can be generated, for example, in the procedure of steps 1-1 and 1-2 below. When the HAPS 10 stays at a predetermined position in the sky or flies around a certain flight route, the generated channel matrix _HBS is saved and used for beamforming control of downlink communication multiple times. good too.

Step 1-1: Define the channel matrix H _BS by the following equations (1) and (2).

“N _b ” in the above equation (1) is the number of terrestrial base stations to which nulls are directed, and “N _t ” is the total number of antenna elements of the array antenna (transmitting antenna). Also, the above equation (2) is a channel vector between the _HAPS 10 and the ground base station b. base station antenna).

は複素数全体の集合を表し、後述の式における

は実数全体の集合を表す。 In addition, in the above formula (1), etc.

represents the set of all complex numbers, and

represents the set of real numbers.

Step 1-2: The direct wave component between all the elements of the array antenna of HAPS 10 and the terrestrial base station b is defined by the following equation (3) and used as the channel vector h _BS,b in the above equation (2).

Here, “ρ _b ” in (3) above is the propagation loss coefficient in the ground base station b, and is represented by the following equation (4) in the case of free space propagation, for example. “D _b ” in equation (4) is the distance between HAPS 10 and terrestrial base station b (base station antenna), and “λ” is the wavelength of the carrier wave.

Further, when the azimuth angle and elevation angle of the ground base station b (base station antenna) viewed from the array antenna of HAPS 10 are φ and θ, respectively, the phase rotation vector “d _b ” and the element gain vector “ g _b ” are represented by the following equations (5) and (6), respectively. “D _b,n ” in equation (5) is the distance between the n-th element of the array antenna of HAPS 10 and the ground base station b (base station antenna). “g(θ _b,n , φ _b,n )” in Equation (6) is a function that returns the amplitude response of the n-th element of the array antenna at elevation angle θ and azimuth angle φ, and “θ _b,n ” is It is the elevation angle of the ground base station b (base station antenna) viewed from the nth element, and "φ _b,n " is the azimuth angle of the ground base station b (base station antenna) viewed from the nth element.

は、アダマール積の演算子である。 In addition, in the above formula (3)

is the Hadamard product operator.

[Communication model]
The downlink communication between the HAPS 10 and the UE (HAPS user) 61 can be modeled separately for each radio resource, for example based on the following communication model.

In a communication model focused on a certain radio resource (time/frequency resource, for example resource block (RB)), the transmission symbol belt s of the transmission signal transmitted from the HAPS 10 is represented by the following equation (7). “s _u ” in equation (7) is the modulation symbol transmitted to the UE of user u, and “Nu” is the number of UEs (number of users) per radio resource.

Here, assuming that the average power of each modulation symbol is normalized as shown in the following equation (8), the transmission power depends only on the diagonal matrix P of the following equation (9).

“E[·]” in the above equation (8) is an ensemble average operator. Also, “p _u ” in the above equation (9) is the power to be allocated to the transmission symbols for the user u to the UE, and has the relationship of the following equation (10) with the total transmission power P _t .

In a communication model focusing on a certain radio resource (time/frequency resource, for example, RB), the channel matrix H of the radio propagation path between the HAPS 10 and the UEs of all users u to which the radio resource is allocated is given by the following equation: (11) and the following equation (12). h _u in equation (12) is the channel vector between the HAPS 10 and the UE of user u, and h _u,n in equation (12) is between the n-th element of the array antenna and the UE of user u. is the channel response of

Note that the above equations (7) to (12) are examples when the number of elements of the UE antenna of the user u is "1", but even when the antenna of the UE of the user u has a plurality of elements Applicable.

FIG. 9 is an explanatory diagram showing an example of a communication model of downlink communication between the relay communication station 110 of the HAPS 10 according to the embodiment and a plurality of UEs 61(1) to 61(Nu) to which the same radio resource is allocated. be. 9, the vector (number of elements: Nu×1) of the transmission signal s (see the above equation (7)) transmitted from the array antenna 130 of the relay communication station 110 of the HAPS 10 and the vector (number of elements: Nu×1) received by the UE of each user u Suppose that the following equation (13) holds between the received signal vector y (the number of elements: Nu×1). "H" in the equation (13) is a channel matrix (number of elements: Nu × Nt) between the array antenna 130 of the HAPS 10 and the UE of the user u represented by the above equations (11) and (12). is. Also, "P" in equation (13) corresponds to power amplification of the transmission signal transmitted from the array antenna 130 of the HAPS 10 represented by the above equations (11) and (12) to the UE of each user u. is a transmission power matrix (number of elements: Nu×Nu).

The received signal vectors y of the UEs of all users u to which the radio resource is allocated in the above equation (13) are expressed by the following equation (14). y _u in equation (14) is the UE received signal of user u.

Vector “n” in the above equation (13) is a noise vector (number of elements: Nu×1) added at the time of reception in the UE of user u, and is represented by the following equation (15). n _u in equation (15) is the Gaussian noise summed at the UE of user u.

The vector "B" in the above formula (13) is a BF weight matrix (number of elements: Nt × Nu) for directing the beam to the UE of each user u during downlink communication, and the following formula (16) and the following formula ( 17). “b _n,u ” in equation (17) is the BF weight applied to the n-th element of array antenna 130 to steer the beam to the UE of user U.

［ビームフォーミング制御］
前述のＨＡＰＳ１０と各地上基地局３０との間のチャネル行列Ｈ_ＢＳ（式（１）及び式（２）参照）と、前述のＨＡＰＳ１０とユーザｕのＵＥとの間のチャネル行列Ｈ（式（１２）及び式（１３）参照）とを生成した後、例えば次の（１）～（４）に例示する複数方式のいずれかによりビームフォーミング制御を行う。 Since there is no power amplification by beamforming (BF) for the UE of each user U, the following equation (18) holds.

[Beamforming control]
The channel matrix H _BS between the HAPS 10 and each ground base station 30 (see equations (1) and (2)) and the channel matrix H between the HAPS 10 and the UE of user u (see equation (12 ) and (see formula (13)) are generated, beamforming control is performed by one of a plurality of methods exemplified in (1) to (4) below, for example.

[Method 1: ZF type]
In ZF (zero-forcing) type scheme 1, as shown in FIG. In addition, beam forming is performed so that each beam does not interfere with each ground base station (see the broken-line interference beams in the figure).

The BF weights used in method 1 can be generated, for example, by following steps 2(1)-1 to 2(1)-3.

Step 2(1)-1: Using the channel matrix H for HAPS user u and the channel matrix H _BS for terrestrial base station b, the extended channel matrix H _EX including terrestrial base station b is obtained by the following equation (19): Define as

Step 2(1)-2: Calculate the pseudo-inverse matrix W of the extended channel matrix H _EX as shown in the following equation (20).

Step 2(1) _-3 : By normalizing the elements w ₁ , w ₂ , . get B.

[Method 2: MMSE type]
In the MMSE (minimum mean square error) type scheme 2, as shown in FIG. beam), and perform beamforming.

The BF weights used in method 2 can be generated, for example, by following steps 2(2)-1 to 2(2)-3.

Step 2(2)-1: Using the aforementioned channel matrix H for HAPS user u and channel matrix H _BS for terrestrial base station b, the extended channel matrix H _EX including terrestrial base station b is expressed by the following equation (22): Define as

Step 2(2)-2: As shown in the following equations (23) and (24), a regularization term R is added when calculating the pseudo-inverse matrix W of the extended channel matrix H _EX . “σ ² ” in Equation (24) is the average noise power, and “I _Nu+Nb ” is a unit matrix of (Nu+Nb)×(Nu+Nb).

Step 2(2)-3: _Normalize the elements w ₁ , w ₂ , . , the BF weight matrix B is obtained.

[Method 3: Hybrid type]
In the hybrid type method 3, as shown in FIG. 12, under the condition that the beams directed to each UE of Nu users connected to the HAPS 10 do not interfere with each terrestrial base station b ( (see solid line desired beam), beamforming is performed so that the SINR at the UE of HAPS user u is maximized.

The BF weights used in method 3 can be generated, for example, by following steps 2(3)-1 to 2(3)-3.

Step 2(3)-1: Using the channel matrix H for HAPS user u and the channel matrix H _BS for terrestrial base station b, the extended channel matrix H _EX including terrestrial base station b is expressed by the following equation (26): Define as

Step 2(3)-2: As shown in the following equations (27) and (28), a regularization term R is added when calculating the pseudo-inverse matrix W of the extended channel matrix H _EX .

Step 2(3)-3: As shown in the following equation (29), the elements w ₁ , _{w 2} , . , the BF weight matrix B is obtained.

[Method 4: Separate type]
In the separate method 4, null formation for the ground base station b and beam formation for the HAPS user u are performed independently. In method 4, a null is formed for the ground base station b as shown in FIG. 13, and any desired beam forming method can be applied to the desired beam (solid line in the figure).

と、ＨＡＰＳユーザｕへビームを形成するための第２ウェイト行列

を互いに独立に生成し、２つのウェイト行列Ｂ_ＮＵＬＬ及びＢ_ＢＦに基づいて次式（３０）に示すように全体のＢＦウェイト行列Ｂを得る。

For example, the first weight matrix to form a null for terrestrial base station b

and a second weight matrix for beamforming to HAPS user u

are generated independently of each other, and based on the two weight matrices B _NULL and B _BF , the entire BF weight matrix B is obtained as shown in the following equation (30).

In addition, as described above, when the HAPS 10 stays at a predetermined position in the sky or flies around a certain flight route, the first weight matrix B _NULL generated in this method 4 is saved, and downlink communication is performed multiple times. may be reused for beamforming control.

The BF weights used in method 4 can be generated, for example, by following steps 2(4)-1 to 2(4)-2.

Step 2(4)-1: Find the first weight matrix B _NULL that satisfies the following equation (31).

The first weight matrix B _NULL is called the null space of the channel matrix H _BS described above _. It becomes the null space of the matrix H _BS .

The first weight matrix B _NULL is obtained by selecting arbitrary M column vectors v _Nb +1, . . . , v _Nt of the right singular matrix V and arranging them. where "M" is any integer in the interval [Nb, Nt-Nb].

Step 2(4)-2: Regard the matrix of the following equation (33) as a new channel matrix, and obtain the aforementioned second weight matrix B _BF based on an arbitrary BF algorithm.

FIG. 14 is a block diagram showing an example of the main configuration of the relay communication station 110 of the HAPS 10 of the embodiment. The relay communication station 110 in FIG. 14 is an example of a base station type relay communication station. The relay communication station 110 includes a service link antenna section 111, a transmission/reception section 112, a feeder link antenna section 113, a transmission/reception section 114, a monitor control section 116, a power supply section 117, a modem section 118, and a base station. A processing unit 119 and a position information acquisition unit 120 are provided.

The service link antenna unit 111 has an array antenna that forms a radial beam toward the ground (or sea), and forms a three-dimensional cell 100C that can communicate with the UE61. The transmitting/receiving unit 112 constitutes a first wireless communication unit together with the service link antenna unit 111, has a duplexer (DUP: DUPplexer), an amplifier, etc. A radio signal is transmitted to the UE 61 located in the area and a radio signal is received from the UE 61 .

The service link antenna unit 111 and the transmitting/receiving unit 112 also function as an uplink (UL) receiving unit that receives uplink signals that can identify the UEs 61 from each of the plurality of UEs 61 via the array antenna 130 .

The feeder link antenna unit 113 has a directional antenna for wireless communication with the ground (or sea) feeder station 70 . The transmitting/receiving unit 114 constitutes a second wireless communication unit together with the feeder link antenna unit 113, has a duplexer (DUP: DUPlexer), an amplifier, etc., and transmits signals to the feeder station 70 via the feeder link antenna unit 113. It transmits radio signals and receives radio signals from feeder stations 70 .

The monitoring control unit 116 is composed of, for example, a CPU and a memory, and monitors the operation processing status of each unit in the HAPS 10 and controls each unit by executing a preinstalled program. In particular, the monitoring control unit 116 executes the control program to control the motor driving unit 141 that drives the propellers 103 and 202 to move the HAPS 10 to the target position and to keep it near the target position. do.

The power supply unit 117 supplies power output from the batteries 106 and 204 to each unit in the HAPS 10 . The power supply unit 117 may have a function of storing electric power generated by a photovoltaic panel or the like or electric power supplied from the outside in the batteries 106 and 204 .

The modem unit 118, for example, executes demodulation processing and decoding processing on the received signal received from the feeder station 70 via the feeder link antenna unit 113 and the transmission/reception unit 114, and outputs data to the base station processing unit 119 side. Generate a signal. Also, the modem unit 118 performs encoding processing and modulation processing on the data signal received from the base station processing unit 119 side, and transmits the data signal to the feeder station 70 via the feeder link antenna unit 113 and the transmission/reception unit 114 . Generate a transmit signal.

The base station processing unit 119 has, for example, a function (for example, e-NodeB, g- functions such as NodeB).

The base station processing unit 119, for example, executes demodulation processing and decoding processing on the received signal received from the UE 61 located in the three-dimensional cell 100C via the service link antenna unit 111 and the transmission/reception unit 112, A data signal to be output to the 118 side is generated. Also, the base station processing unit 119 performs encoding processing and modulation processing on the data signal received from the modem unit 118 side, and transmits the data signal to the UE 61 of the three-dimensional cell 100C via the service link antenna unit 111 and the transmission/reception unit 112. generates a baseband signal (IQ signal) to be transmitted to the

The position information acquisition unit 120 acquires position information of the HAPS 10 based on the output of the GNSS receiver incorporated in the HAPS 10, for example.

15 is a block diagram showing an example of the main configuration of the base station processing section 119 in the relay communication station 110 of FIG. 14. As shown in FIG. FIG. 16 is an explanatory diagram showing an example of radio resource allocation in the case of full digital BF in the base station processing section 119 of FIG. In the configuration example of FIG. 15, all UEs 61 residing in the HAPS cell 100C are divided into K groups by Nu UEs (users), and different radio resources are assigned to each group. This is a configuration example in the case of performing beam forming control by any one of methods (1) to (3). It should be noted that FIG. 15 shows only the main components related to the present embodiment, and the illustration of other components necessary for communication with the UE 61 is omitted.

Base station processing section 119 in FIG. Based on the position information of the current position of HAPS 10 acquired by position information acquisition section 120 and the position information of terrestrial base station (base station antenna) 30, channel matrix generation section 1190 generates a channel matrix between HAPS 10 and terrestrial base station 30. generate a channel matrix H _BS of .

In the configuration example of FIG. 15, since the channel matrix (channel response) H and BF weight B are different for each radio resource as shown in FIG. 16, it can be used only in the configuration of full digital beamforming.

Digital beam forming units 1191(1) to 1191(K) are provided to correspond to a plurality of radio resources 1 to K, respectively. Each digital beamforming unit 1191 (n), for the corresponding radio resource n, to transmit symbols by multiple (Nv) layers (streams) in downlink MU-MIMO communication, beamforming and ground base for each UE61 described above A BF weight B ⁽ⁿ⁾ considering null formation to the station (base station antenna) 30 is applied to generate a transmission signal in the frequency domain.

A plurality of frequency/time converters 1192 are provided for each antenna element of the array antenna 130, and convert frequency-domain transmission signals received from the digital beamforming units 1191(1) to 1191(K) into time-domain transmission signals. and pass it to the same number of RF chains as the number of antenna elements, which are composed of power amplifiers and the like.

FIG. 17 is a block diagram showing another example of the main configuration of base station processing section 119 in relay communication station 110 of FIG. FIG. 18 is an explanatory diagram showing an example of radio resource allocation in the case of hybrid BF in the base station processing unit 119 of FIG. In the configuration example of FIG. 17, all UEs 61 located in the HAPS cell 100C are divided into K groups for each Nu UEs (users), different radio resources are assigned to each group, and the above-described It is a configuration example in the case of performing beam forming control by the method (4). It should be noted that FIG. 17 shows only the main components related to the present embodiment, and the illustration of other components necessary for communication with the UE 61 is omitted.

The base station processing unit 119 in FIG. 17 includes a channel matrix generation unit 1190, a plurality of (K) digital beamforming units 1191(1) to 1191(K), a plurality of frequency/time conversion units 1192, and each radio resource. and an analog beam forming unit 1193 common to . Based on the position information of the current position of HAPS 10 acquired by position information acquisition section 120 and the position information of terrestrial base station (base station antenna) 30, channel matrix generation section 1190 generates a channel matrix between HAPS 10 and terrestrial base station 30. generate a channel matrix H _BS of .

In the configuration example of FIG. 17, as shown in FIG. 18, the channel matrix (channel response) H between the user (UE) and the BF weight B _BF for directing the beam to each user (UE) are different for each radio resource. However, the BF weight B _NULL for directing null to the ground base station (base station antenna) 30 is common to each radio resource. Therefore, not only the configuration of full digital beamforming but also the configuration of hybrid beamforming combining analog-digital can be used.

Digital beam forming units 1191(1) to 1191(K) are provided to correspond to a plurality of radio resources 1 to K, respectively. Each digital beamforming unit 1191 (n) considers only beamforming for each UE 61 described above for transmission symbols by multiple (Nv) layers (streams) in downlink MU-MIMO communication for the corresponding radio resource n. BF weight B _BF ⁽ⁿ⁾ is applied to generate a transmission signal in the frequency domain.

A plurality of frequency/time converters 1192 are provided for each antenna element of array antenna 130, and transmit transmission signals in the frequency domain received from digital beamforming units 1191(1) to 1191(K) in a predetermined number of time domains. It is converted into a signal and passed to an intermediate signal processing RF chain, such as a power amplifier. The number of RF chains for intermediate signal processing is the same number as M (<Nt) selected in scheme (4) above.

The analog beamforming unit 1193 performs beamforming control applying the BF weight B _NULL considering null formation to the terrestrial base station (base station antenna) 30, and generates the same number of time-domain transmission signals as the number of antenna elements Nt. and pass it to the same number of RF chains as the number of antenna elements, which are composed of power amplifiers and the like.

As described above, according to the present embodiment, when a terrestrial cell formed by an antenna of a terrestrial base station using the same frequency band is located in the cell 100C formed from the HAPS 10 in the sky toward the ground or the sea, It is possible to suppress interference to cells (ground base station 30 and UE 65 connected to the ground base station).

In the above embodiment, the interference suppression target for suppressing the beam interference from the HAPS 10 is the ground cell (the ground base station 30 and the UE 65 connected to the ground base station). is not limited to the above ground cells.

For example, the interference suppression technology for suppressing the interference of beams from the HAPS 10 described in the above embodiment can be applied when the interference suppression target is a radio astronomical observation station. Extremely strict power limits are imposed as interference protection regulations for the frequency bands used in radio astronomy services at radio astronomy observation stations. If the HAPS 10 uses a frequency band adjacent to or close to the frequency band used in the radio astronomy business, there is a possibility that the above power limit criteria will not be met due to unwanted emissions (spurious) outside the band used by the HAPS 10. . Therefore, by using the interference suppression technique of the above-described embodiment and always directing the null from the HAPS 10 toward the position of the antenna of the radio astronomical observation station, the interference from the HAPS 10 to the radio astronomical observation station can be suppressed.

In addition, the processing steps described in this specification and the relay communication station, feeder station, gateway station, management device, monitoring device, remote control device, server, terminal device (UE: user device, mobile) of communication relay devices such as HAPS 10 Stations, communication terminals), base stations and base station equipment components may be implemented by various means. For example, these processes and components may be implemented in hardware, firmware, software, or any combination thereof.

For hardware implementation, entities (for example, relay communication stations, feeder stations, gateway stations, base stations, base station equipment, relay communication station equipment, terminal equipment (UE: user equipment, mobile station, communication terminal), management equipment, Means such as processing units used to implement the above steps and components in a monitoring device, remote control device, server, hard disk drive or optical disk drive) consist of one or more application specific ICs ( ASIC), Digital Signal Processor (DSP), Digital Signal Processor (DSPD), Programmable Logic Device (PLD), Field Programmable Gate Array (FPGA), Processor, Controller, Microcontroller, Microprocessor, Electronic Device , other electronic units designed to perform the functions described herein, computers, or combinations thereof.

Also, for firmware and/or software implementations, means such as processing units used to implement said components may be programs (e.g. procedures, functions, modules, instructions) that perform the functions described herein. , etc.). In general, any computer/processor readable medium tangibly embodying firmware and/or software code means, such as a processing unit, used to implement the steps and components described herein. may be used to implement For example, firmware and/or software code may be stored in memory and executed by a computer or processor, such as in a controller. The memory may be implemented within the computer or processor, or external to the processor. The firmware and/or software code may also be, 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 disk, compact disk (CD), digital versatile disk (DVD), magnetic or optical data storage devices, etc. good. The code may be executed by one or more computers or processors and may cause the computers or processors to perform certain aspects of the functionality described herein.

Also, the medium may be a non-temporary recording medium. Also, the code of the program is not limited to a specific format as long as it can be read and executed by a computer, processor, or other device or machine. For example, the program code may be source code, object code, or binary code, or may be a mixture of two or more of these codes.

Moreover, the description of the embodiments disclosed herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to this 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 this disclosure. This disclosure, therefore, is not to be limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

10: HAPS cell 30: Terrestrial base station 80: Mobile communication network 100A: Service area 100B: Beam 100C: HAPS cell (three-dimensional cell)
100F: footprint 110: relay communication station 119: base station processing unit 120: location information acquisition unit 130: array antenna 130a: antenna element 300C: terrestrial cell 1190: channel matrix generation unit 1191: digital beam forming unit 1192: frequency/time Conversion unit 1193: analog beam forming unit

Claims (13)

An airborne communication relay device that forms a first cell facing the ground or the sea and performs wireless communication with a plurality of terminal devices located in the first cell,
an array antenna having a plurality of antenna elements forming a beam pattern consisting of a plurality of beams in the first cell;
Based on positional information of an antenna targeted for interference suppression arranged at a position lower than the array antenna, beam forming is controlled so that a null of the beam pattern formed by the array antenna is directed toward the antenna targeted for interference suppression. and means for performing downlink communication with the plurality of terminal devices;
A communication relay device comprising: In the communication relay device of claim 1,
Forming a plurality of beams respectively directed to a plurality of terminal devices that are located in the first cell and connected to the communication relay device, and that nulls in the beam pattern are directed to the antenna to be subjected to interference suppression. A communication relay device that controls beamforming. In the communication relay device of claim 2,
a radio resource allocation unit that allocates a plurality of radio resources to be used for downlink communication with the plurality of terminal devices based on channel state information of the plurality of terminal devices;
For each of the plurality of radio resources, forming a plurality of beams directed to each of a plurality of terminal devices, and perform beam forming control so that nulls of the beam pattern are directed to the interference suppression target antenna, frequency a plurality of frequency-domain beamforming controllers that generate region transmission signals;
A communication relay device comprising: In the communication relay device of claim 2,
a radio resource allocation unit that allocates a plurality of radio resources to be used for downlink communication with the plurality of terminal devices based on channel state information of the plurality of terminal devices;
a plurality of frequency-domain beamforming control units that perform beamforming control so as to form a plurality of beams directed to each of a plurality of terminal devices for each of the plurality of radio resources, and generate frequency-domain transmission signals; ,
A time to perform beamforming control for all of the plurality of radio resources so that nulls of the beam pattern are directed to the interference suppression target antenna, and to generate a time-domain transmission signal converted from the frequency-domain transmission signal. a region beamforming controller;
A communication relay device comprising: In the communication relay device according to claim 3 or 4,
The frequency domain beamforming control unit includes:
generating a channel matrix between the array antenna and the interference suppression target antenna;
calculating the beamforming weights for each of the plurality of radio resources based on the channel matrix;
For each of the plurality of terminal devices, a frequency domain downlink signal is generated based on the radio resources assigned to the terminal device and the beamforming weights calculated for the radio resources,
A communication relay device characterized by: In the communication relay device according to any one of claims 2 to 5,
The beamforming is controlled so that the plurality of beams directed to the plurality of terminal devices do not interfere with each other and each of the plurality of beams does not interfere with the base station antenna. , a communication relay device characterized by: In the communication relay device according to any one of claims 2 to 5,
A communication relay apparatus, wherein the beamforming is controlled such that the SINR of the terminal apparatus is maximized. In the communication relay device according to any one of claims 2 to 5,
Under the condition that each of the plurality of beams directed to the plurality of terminal devices does not interfere with the base station antenna, the beamforming is controlled so that the SINR of the terminal device is maximized. A communication relay device characterized by: In the communication relay device according to any one of claims 2 to 5,
A communication characterized in that a first beamforming control for directing a beam to each of the plurality of terminal devices and a second beamforming control for directing a null of the beam pattern to the base station antenna are performed independently of each other. Relay device. In the communication relay device according to any one of claims 1 to 9,
The antenna to be subjected to interference suppression is a low-position base station antenna arranged at a position lower than the array antenna and forming a second cell within the first cell using the same frequency band as the first cell. , a communication relay device characterized by: In the communication relay device according to any one of claims 1 to 9,
The communication repeater according to claim 1, wherein the antenna to be subjected to interference suppression is an antenna of a radio astronomical observation station arranged at a position lower than the array antenna. A system comprising: the communication relay device according to any one of claims 1 to 10; and a terminal device that performs MU-MIMO wireless communication with the communication relay device. Wireless communication with a plurality of terminal devices located in the first cell via an array antenna having a plurality of antenna elements forming a beam pattern composed of a plurality of beams in the first cell toward the ground or the sea. A program executed by a computer or processor installed in an airborne communication relay device that performs
Based on positional information of an antenna targeted for interference suppression arranged at a position lower than the array antenna, beam forming is controlled so that a null of the beam pattern formed by the array antenna is directed toward the antenna targeted for interference suppression. and a program code for performing downlink communication with the plurality of terminal devices;
A program characterized by comprising:

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