Mobile communication system

Abstract

To improve frequency utilization efficiency, prevent a decrease in communication capacity of terminals, and reduce interference in the uplink and downlink service links of each base station in a mobile communication system including an aerial relay base station equipped with an antenna provided on an airborne object (including UAV, HAPS, and communication satellites) and a ground base station.SOLUTION: An airborne relay base station and a ground base station each perform wireless communication of a service link with terminals using a time division duplex (TDD) method that uses the same frequency. The transmission timing and reception timing of wireless communication using the TDD method in the service link are reversed between the airborne relay base station and the ground base station. The ground base station suppresses interference signals from the airborne relay base station included in the received signals on the uplink. The airborne relay base station suppresses interference signals from the ground base station included in the received signals on the uplink.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a mobile communication system including a base station capable of wireless communication with a terminal.

Background Art

[0002] Conventionally, as a flying object or a floating object located in the air, a UAV flying at an altitude of 18 km or less and a HAPS flying in the stratosphere at an altitude of 18 km or more are known. Further, as a first base station that performs wireless communication with a terminal via a service link antenna of a relay communication station provided in a flying object or a floating object such as a UAV or a HAPS (flying object) located in the air, an aerial relay type base station, and a ground base station as a second base station that performs wireless communication with a terminal via an antenna arranged on land or at sea are provided. There is known a mobile communication system in which the same frequency is shared in the service links of the aerial relay type base station and the ground base station so that wireless communication can be performed with a terminal having a common specification.

[0003] As a technique applicable to reducing interference between an aerial relay type base station and a ground base station in a mobile communication system, there is an interference control technique for adjusting and controlling a radio frame in a time domain (subframe unit) on the premise that the aerial relay type base station and the ground base station are time synchronized with each other (see, for example, Patent Document 1 and Non-Patent Document 1). This interference control technique is a technique compliant with the LTE (Long Term Evolution)-Advanced standard and is also called eICIC (enhanced Inter-Cell Interference Coordination).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When applying the above conventional interference control technology, since the airborne relay base station and the ground base station use the frequencies assigned to the service link in a time-division manner, the radio signals used by the airborne relay base station and the ground base station are orthogonal on the time axis, and mutual interference does not occur. However, due to the time-division use of frequencies, both the airborne relay base station and the ground base station cannot use all the frequencies assigned to the service link, so the communication capacity (maximum transmission rate, peak throughput) of the terminals of each service link decreases.

Means for Solving the Problems

[0007] A mobile communication system according to one aspect disclosed in this specification includes an airborne relay base station that wirelessly communicates with a terminal via a service link antenna of a relay communication station provided on an airborne object or a floating object located in the air, and a ground base station arranged on the ground or at sea. The airborne relay base station and the ground base station are a mobile communication system that is time-synchronized with each other. The airborne relay base station and the ground base station each perform wireless communication of a service link with a terminal by a TDD (Time Division Duplex) method using the same frequency. The transmission timing and reception timing of the wireless communication of the TDD method in the service link are made opposite to each other between the airborne relay base station and the ground base station.

[0008] The terrestrial base station branches a downlink transmission signal transmitted from the terrestrial base station and transfers it to the aerial relay-type base station as a transmission replica signal. The terrestrial base station performs correlation processing between a reception signal of an uplink of the terrestrial base station including an interference signal from the aerial relay-type base station that interferes with the uplink of the terrestrial base station and a transmission replica signal transferred from the aerial relay-type base station, estimates a complex reception amplitude of the interference signal from the aerial relay-type base station, and uses the estimation result of the complex reception amplitude of the interference signal from the aerial relay-type base station and the pre-transmission replica signal to generate an interference suppression signal for suppressing the interference signal from the aerial relay-type base station, and synthesizes the reception signal of the uplink of the terrestrial base station and the interference suppression signal, thereby suppressing the interference signal from the aerial relay-type base station included in the reception signal of the uplink of the terrestrial base station.

[0009] The aerial relay-type base station branches a downlink transmission signal transmitted from the aerial relay-type base station and transfers it to the terrestrial base station as a transmission replica signal. The aerial relay-type base station performs correlation processing between a reception signal of an uplink of the aerial relay-type base station including an interference signal from the terrestrial base station that interferes with the uplink of the aerial relay-type base station and a transmission replica signal transferred from the terrestrial base station, estimates a complex reception amplitude of the interference signal from the terrestrial base station, and uses the estimation result of the complex reception amplitude of the interference signal from the terrestrial base station and the transmission replica signal to generate an interference suppression signal for suppressing the interference signal from the terrestrial base station, and synthesizes the reception signal of the uplink of the aerial relay-type base station and the interference suppression signal, thereby suppressing the interference signal from the terrestrial base station included in the reception signal of the uplink of the aerial relay-type base station.

[0010] In the mobile communication system, the aerial relay-type base station and the terrestrial base station may each perform adjustment of transmission timing such that transmissions are reversed using time information acquired by a GNSS (Global Navigation Satellite System) receiver.

[0011] In the mobile communication system, the relay communication station mounted on the aircraft or the floating body may be constituted by a repeater relay device (frequency conversion repeater relay device) that relays without reproducing the transmission and reception signals.

[0012] In the mobile communication system, the relay communication station mounted on the aircraft or the floating body may be constituted by a base station device that reproduces the transmission and reception signals, remodulates the reproduced signals, and relays them.

[0013] The mobile communication system may further include a base station interworking control device that controls between the aerial relay type base station and the ground base station, and the base station interworking control device may transfer the transmission replica signal from the ground base station to the aerial relay type base station and transfer the transmission replica signal from the aerial relay type base station to the ground base station.

[0014] The mobile communication system includes a centralized base station configuration unit in which the ground base station and the aerial relay type base station are installed at the same location or configured within the same device, and the centralized base station configuration unit estimates the complex reception amplitude of the interference signal from the aerial relay type base station in the ground base station, generates the interference suppression signal, and suppresses the interference signal from the aerial relay type base station, and estimates the complex reception amplitude of the interference signal from the ground base station in the aerial relay type base station, generates the interference suppression signal, and suppresses the interference signal from the ground base station.

[0015] The mobile communication system may further include a base station interworking control device that controls between the aerial relay type base station and the ground base station, and the base station interworking control device may use the time information of GNSS (Global Navigation Satellite System) received at the aerial relay type base station via the gateway device and the time information of GNSS (Global Navigation Satellite System) received at the ground base station to adjust the transmission timing so that transmission and reception are reversed.

[0016] In the mobile communication system, the aircraft or the floating body may be a communication satellite, a UAV (Unmanned Aerial Vehicle) flying at an altitude of 18 km or less, or a HAPS flying in the stratosphere at an altitude of 18 km or more.

[0017] According to the mobile communication system disclosed in this document, the interference caused by the downlink transmission signal from the service link antenna (upper air relay type base station antenna) of the relay communication station provided on the aircraft or floating body located in the air to the reception signal of the uplink of the service link antenna (ground base station antenna) of the ground base station can be reduced, and the interference caused by the downlink transmission signal from the ground base station antenna to the reception signal of the uplink of the upper air relay type base station antenna can be reduced.

Brief Description of the Drawings

[0018]

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DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, various embodiments will be described with reference to the drawings. Note that each figure schematically shows the shape, size, and positional relationship only to the extent that the content of the present invention can be understood. Therefore, the present invention is not limited only to the shape, size, and positional relationship illustrated in each figure. Also, the numerical values exemplified hereinafter are merely preferred examples of the present invention, and thus the present invention is not limited to the illustrated numerical values.

[0020] In this embodiment, an example of a mobile communication system that shares the same frequency between a HAPS base station (HAPS cellular system) as an aerial relay type base station and a ground base station (ground cellular system) will be mainly described. However, the present invention can also be applied to a mobile communication system in which the relay communication station of the aerial relay type base station is provided on a flying object or a floating object other than HAPS. Here, the aerial relay type base station may be an aerial communication base station used in an NTN (Non-Terrestrial Network). The NTN may be a network using, for example, an artificial satellite such as a communication satellite described later, and a HAPS or a drone as a stratospheric communication platform that can provide communication services to a wide area by mounting communication devices on an unmanned aircraft flying in the stratosphere.

[0021] FIG. 1 is a diagram showing an example of the configuration of a mobile communication system (mobile phone system) according to an embodiment of the present invention. In FIG. 1, the mobile communication system of this embodiment includes, as a plurality of base stations capable of wireless communication with the terminal 30, a HAPS base station (HAPS cellular system) 10 as a first base station (aerial relay type base station) and a ground base station (ground cellular system) 20 as a second base station.

[0022] The HAPS base station 10 wirelessly communicates with a terminal (hereinafter also referred to as the "HAPS base station terminal") 30(1) via a service link antenna (also referred to as the "HAPS base station antenna") 112 of a relay communication station 11 provided in a HAPS (High-Altitude Pseudo-Satellite or High-Altitude Platform Station) 100 which is a flying object or a floating object located in the sky. The HAPS 100 can fly powered by, for example, at least one of a battery and a solar power generation system. The HAPS 100 may be a solar plane type HAPS in addition to the airship type HAPS as shown in the figure. Further, the flying object or the floating object on which the relay communication station 11 is provided may be, in addition to the HAPS, an artificial satellite (for example, a communication satellite), a balloon, a drone, or an aircraft. The artificial satellite may be, for example, a LEO (Low Earth Orbit) satellite located in an orbit at an altitude of up to 2,000 km from the Earth's surface, a MEO (Medium Earth Orbit) satellite located in an orbit at an altitude higher than 2,000 km and lower than 36,000 km, or a HEO (High Earth Orbit) satellite located in an orbit at an altitude near 36,000 km or higher than 36,000 km. Further, the artificial satellite may be a GEO (Geostationary Orbit) satellite, a quasi-geostationary satellite, a quasi-zenith satellite, or a non-geostationary satellite. Further, the flying object or the floating object on which the relay communication station 11 is provided may be unmanned or manned. For example, the flying object or the floating object may be an unmanned or manned HAPS, an unmanned or manned artificial satellite, an unmanned or manned balloon, an unmanned or manned drone, an unmanned aircraft, or a manned aircraft. Further, the flying object or the floating object may be an unmanned aircraft (UAV: Unmanned Aerial Vehicle) such as an unmanned drone or a UAS (Unmanned Aircraft Systems). Further, the flying object or the floating object may be a moored type moored to another device (mooring device) using a mooring line such as a rope, a cable, a string, or a wire having a predetermined strength. The purpose of mooring with the mooring line may include the purposes of power supply and signal transmission.The other device to which the above-mentioned moored aircraft or floating body is moored may be a device fixedly arranged on the ground, a device provided on a vehicle movable on the ground, a device provided on a ship, a floating object, etc. movable on water such as the sea or a lake, or a device provided on another aircraft or floating body. The mooring line may include a power supply line, a communication line such as an optical fiber, or both the power supply line and the communication line. For example, the above-mentioned moored aircraft or floating body may be one or more wired power supply drones moored by one or more mooring lines (power supply lines). Further, aircraft or floating bodies such as HAPS100, artificial satellites, drones, balloons, airplanes, and UAVs may fly with at least one of a battery and an engine as a power source. The UAV may be, for example, an unmanned aircraft flying with fuel or a drone flying with a battery or the like.

[0023] The HAPS100 equipped with the relay communication station 11 may be controlled, for example, to float or fly in an airspace (floating airspace) with an altitude H of 100 [km] or less from the ground G (or the sea surface) by autonomous control or external control. The airspace where the HAPS100 is located may be, for example, an airspace in the stratosphere with an altitude H of 18 [km] or more and 50 [km] or less. This airspace may be an airspace with an altitude of 15 [km] or more and 25 [km] or less where the weather conditions are relatively stable, and particularly an airspace with an altitude of approximately 20 [km]. Further, the above airspace may be an airspace with an altitude of 0.1 [km] or more and 18 [km] or less for the UAV. Further, the airspace may be an airspace with an altitude of 0.05 [km] or more for the drone.

[0024] The relay communication station 11 includes a feeder link antenna section (hereinafter also referred to as "FL antenna") 111 and a service link antenna section (HAPS base station antenna) 112. The relay communication station 11 can perform feeder link FL communication with a HAPS gateway device (hereinafter referred to as "HAPS-GW") 12 provided on the ground (or at sea) via the FL antenna 111. The FL antenna 111 is, for example, an array antenna whose directivity can be controlled as described later, and may be a Massive antenna in which a large number of antenna elements are two-dimensionally arranged and the directivity in the horizontal and vertical directions can be controlled.

[0025] In addition, the relay communication station 11 can perform service link SL(1) communication with the HAPS base station terminal 30(1) via the HAPS base station antenna 112. The HAPS base station antenna 112 is, for example, an array antenna whose directivity can be controlled, and may be a Massive antenna in which a large number of antenna elements are two-dimensionally arranged and the directivity in the horizontal and vertical directions can be controlled.

[0026] The HAPS-GW 12 is connected to the core network 40 of the mobile communication network by a wired or wireless communication line, and includes a feeder link antenna section (hereinafter also referred to as "FL antenna") 121 composed of a parabolic antenna, a Massive antenna capable of controlling the directivity in the horizontal and vertical directions, etc. The HAPS-GW 12 can perform feeder link FL communication with the relay communication station 11 mounted on the HAPS via the FL antenna 121.

[0027] The terrestrial base station 20 includes an antenna unit (hereinafter also referred to as the "terrestrial base station antenna") 21 and a base station device 22 connected to the core network 40 of the mobile communication network by a wired or wireless communication line such as an optical fiber. The base station device 22 can communicate with a terminal (hereinafter also referred to as the "terrestrial base station terminal") 30(2) via the terrestrial base station antenna 21 over a service link SL(2). The terrestrial base station antenna 21 may be, for example, an array antenna whose directivity can be controlled, in which a large number of antenna elements are two-dimensionally arranged and which is a Massive antenna capable of controlling directivity in the horizontal and vertical directions.

[0028] The HAPS-GW12 of the HAPS base station 10 and the base station device 22 of the terrestrial base station 20 are each connected to a base station interconnection control device (also referred to as the "base station network interconnection control device" or the "system interconnection control device") 50 by a wired or wireless communication line such as an optical fiber in the network cooperation control system. The HAPS base station 10 and the terrestrial base station 20 are time synchronized with each other via the base station interconnection control device 50, and timing control is executed so that the transmission and reception timings of the HAPS base station 10 and the terrestrial base station 20 are opposite.

[0029] The HAPS base station 10 and the terrestrial base station 20 are each configured using hardware such as a computer device having, for example, a CPU and a memory, an external communication interface unit for the core network 40 and the base station interconnection control device 50, and a wireless communication unit. By executing a predetermined program, wireless communication can be performed between the HAPS base station terminal 30(1) and the terrestrial base station terminal 30(2), and communication can be performed with the core network 40 and the base station interconnection control device 50.

[0030] In the mobile communication system of this embodiment, the same radio transmission method is used for the communication of the service link SL(1) of the HAPS base station 10 and the communication of the service link SL(2) of the terrestrial base station 20, and the same frequency is shared to improve the frequency efficiency of the service link. As the same radio transmission method, a TDD (Time Division Duplex) method that transmits and receives by time division at the same frequency is targeted. For example, communication methods such as LTE (Long Term Evolution) and LTE-Advanced, the communication method of the fourth-generation mobile phone, the communication method of the fifth-generation mobile phone, or the communication method of subsequent next-generation mobile phones can be applied as the TDD method.

[0031] The HAPS base station terminal 30(1) that can communicate by connecting to the HAPS base station 10 and the terrestrial base station terminal 30(2) that can communicate by connecting to the terrestrial base station 20 are mobile communication terminals 30 of the same specification. The terminal 30 is a mobile phone, a smartphone, a laptop computer with a mobile communication function, etc., and is also called a mobile terminal, a user equipment (UE), a mobile station, a mobile device, or a portable communication terminal. The terminal 30 may be a modular mobile station incorporated in a vehicle such as an automobile or a moving body such as a drone, or may be a terminal device of an IoT (Internet of Things) device.

[0032] The terminal 30 is configured using hardware such as a computer device having, for example, a CPU and a memory, and a wireless communication unit, and can perform wireless communication and the like with each of the HAPS base station 10 and the terrestrial base station 20 when a predetermined program is executed.

[0033] The HAPS base station 10 of this embodiment is composed of a relay communication station 11 mounted on the HAPS 100 in the sky, or is composed of the relay communication station 11 and the HAPS-GW12 provided on the ground (or at sea).

[0034] FIG. 2(a) is a diagram showing a configuration example of a relay communication station 11 that constitutes an example of a HAPS base station 10 in the mobile communication system of the embodiment. In this configuration example, the relay communication station 11 is a radio relay device (hereinafter referred to as a "frequency conversion repeater") that converts the frequencies of a service link and a feeder link having different frequencies. In the downlink, the relay communication station 11 converts the frequency of the feeder link transmitted from the HAPS-GW 12 to the frequency of the service link and transmits it to the HAPS base station terminal 30(1). On the other hand, in the uplink, the relay communication station 11 converts the frequency of the service link transmitted from the HAPS base station terminal 30(1) to the frequency of the feeder link and transmits it to the HAPS-GW 12.

[0035] The relay communication station 11 of the HAPS base station 10 in this example is composed of a repeater relay device (frequency conversion repeater) having a repeater 113 and a frequency conversion device 114. The repeater 113 includes a low-noise amplifier that amplifies the received signal of the service link SL(1) received via the HAPS base station antenna 112, a power amplifier that amplifies the transmission signal of the service link SL(1) transmitted via the HAPS base station antenna (SL antenna) 12, and the like. The frequency conversion device 114 performs conversion between the frequency of the service link SL(1) and the frequency of the feeder link FL.

[0036] Figure 2(b) is a diagram showing a configuration example of HAPS-GW12 corresponding to Figure 2(a). The HAPS-GW12 in this example includes a base station device (hereinafter also referred to as the "HAPS base station device") 122 and a frequency conversion device 123. The base station device 122 includes a baseband processing device that processes the baseband signal of the service link, a communication interface unit for communicating with the core network 40 via a backhaul line, and the like. The frequency conversion device 123 performs conversion between the frequency of the service link signal input / output to / from the base station device 122 and the frequency of the feeder link signal transmitted / received via the FL antenna 121. In addition, HAPS-GW12 also has a function of communicating with the inter-base station cooperation control device 50 in order to adjust the transmission / reception timing of the service link SL with the terrestrial base station 20 or transfer the position information of HAPS100.

[0037] Figure 3(a) is a diagram showing a configuration example of the relay communication station 11 that constitutes another example of the HAPS base station 10 in the mobile communication system of the embodiment. In this configuration example, the relay communication station 11 of the HAPS base station 10 includes a base station device similar to a normal terrestrial base station, and a feeder link transceiver that uses a frequency different from that of the service link for the feeder link between the relay communication station 11 of the HAPS base station 10 and the HAPS-GW. In the feeder link, unlike the service link, an appropriate optimal wireless transmission method can be selected as appropriate.

[0038] The relay communication station 11 of the HAPS base station 10 in this example includes a base station device 115 equivalent to the base station device (hereinafter also referred to as the "terrestrial base station device") 22 of the terrestrial base station 20, and a feeder link transceiver 116. The base station device 115 includes a low-noise amplifier that amplifies the received signal of the service link SL(1) received via the HAPS base station antenna 112, a power amplifier that amplifies the transmission signal of the service link SL(1) transmitted via the HAPS base station antenna 112, a baseband processing device that processes the baseband signal of the service link, and the like. The feeder link transceiver 116 transmits and receives signals of the backhaul line transmitted / received via the FL antenna 111 to / from the HAPS-GW12.

[0039] Figure 3(b) is a diagram showing a configuration example of HAPS-GW12 corresponding to Figure 3(a). HAPS-GW12 in this example has a feeder link transceiver 124. The feeder link transceiver 124 transmits and receives signals of a backhaul line that are transmitted and received via an FL antenna 121 to and from an aerial relay communication station 11 mounted on HAPS100. Further, the feeder link transceiver 124 communicates with the core network 40 via the backhaul line. In addition, HAPS-GW12 also has a function of communicating with an inter-base station cooperation control device 50 in order to adjust the transmission and reception timing of a service link SL with the terrestrial base station 20 or transfer the position information of HAPS100.

[0040] In a configuration including a HAPS base station 10 and a terrestrial base station 20 as shown in Figure 1, if the HAPS base station 10 and the terrestrial base station 20 transmit radio waves at the same timing in the FDD mode or the TDD mode, or if the HAPS base station terminal 30(1) and the terrestrial base station terminal 30(2) transmit signals at the same timing, there is a possibility of interference occurring between the aerial HAPS cellular system and the terrestrial cellular system. For example, as shown in Figure 4(a), when a signal of a HAPS downlink line is being transmitted from the relay communication station 11 mounted on the aerial HAPS100 to the HAPS base station terminal 30(1), the transmitted signal of the HAPS downlink line may reach the terrestrial base station terminal 30(2) that is receiving a signal of the terrestrial downlink line from the terrestrial base station 20, and there is a possibility of interference from the HAPS downlink line to the terrestrial base station terminal 30(2). Also, as shown in Figure 4(b), when a signal of the terrestrial uplink line is being transmitted from the terrestrial base station terminal 30(2) to the terrestrial base station 20, the transmitted signal of the terrestrial uplink line may reach the relay communication station 11 of the aerial HAPS100 that is receiving a signal of the HAPS uplink line from the HAPS base station terminal 30(1), and there is a possibility of interference from the terrestrial base station terminal 30(2) to the HAPS uplink line of the relay communication station 11 mounted on HAPS100.

[0041] Conventionally, as a technique for controlling interference between a plurality of base stations, an inter-cell interference control technique called eICIC compliant with the above-mentioned LTE-Advanced standard is known.

[0042] FIG. 5 is a diagram showing an arrangement example of time slots of radio resources set in each of the HAPS base station 10 and the terrestrial base station 20 when the inter-cell interference control technique (eICIC) is applied when the HAPS base station is applied to the system configuration of the reference example. As shown in FIG. 5, in the conventional inter-cell interference control technique (eICIC), radio resources of the same frequency are time-divided, and different time slots are assigned to each of the HAPS base station 10 and the terrestrial base station 20. As a result, since the radio resources are orthogonal on the time axis, interference at the same frequency between the HAPS base station 10 and the terrestrial base station 20 can be mutually avoided. However, in the conventional inter-cell interference control technique (eICIC), radio resources (time slots) are time-divided and used in each of the HAPS base station 10 and the terrestrial base station 20. Therefore, the entire frequency (entire time) allocated to the mobile communication system according to the embodiment cannot be used, and the communication capacity (maximum transmission rate, peak throughput) of each service link of the HAPS base station 10 and the terrestrial base station 20 decreases. In particular, the communication capacity of the terrestrial base station terminal connected to the terrestrial base station 20 with a large number of terminals in the cell decreases.

[0043] In the present embodiment, in order to avoid interference between the HAPS base station 10 and the terrestrial base station 20 and prevent a decrease in the communication capacity (maximum transmission rate, peak throughput) of each service link of the HAPS base station 10 and the terrestrial base station 20, as a transmission / reception method of the service link of each base station 10, 20, the TDD (Time Division Duplex) method adopted in a standard specification such as the fifth generation of mobile communication is used.

[0044] In the TDD (Time Division Duplex) mode, the same frequency is used for the uplink and downlink, and time slots are used in a time-division manner for the uplink and downlink. For example, in the terrestrial base station 20, as shown in FIGS. 6(a) and 6(b), the same frequency is used for the uplink and downlink between the terrestrial base station 20 and the terrestrial base station terminal 30(2). Then, as shown in FIG. 6(c), the radio resources (time slots) on the time axis are time-division multiplexed and used between the downlink transmission (base station transmission) from the terrestrial base station 20 to the terrestrial base station terminal 30(2) and the uplink transmission (terminal transmission) from the terrestrial base station terminal 30(2) to the terrestrial base station 20.

[0045] When the TDD (Time Division Duplex) mode is used in the HAPS base station 10 and the terrestrial base station 20 of the present embodiment, by applying the interference reduction technology described below for avoiding interference between the HAPS base station 10 and the terrestrial base station 20, the HAPS base station 10 and the terrestrial base station 20 can completely share the same frequency. Furthermore, since the HAPS base station 10 and the terrestrial base station 20 can use all the frequencies (all times) allocated to the mobile communication system, it is possible to prevent a decrease in the communication capacity of the service links of each base station 10, 20. In particular, it is possible to prevent a decrease in the communication capacity of the terrestrial base station terminals connected to the terrestrial base station 20 where the number of terminals in the cell is large.

[0046] In a system in which a plurality of base stations using the conventional TDD mode share the same frequency, in order to avoid interference between the uplink and downlink of each base station, for example, as shown in FIG. 7, synchronization control is performed so that the transmission timings of the base station transmissions of the downlink from the base station to the terminal coincide between the plurality of base stations 20(1), 20(2), and the transmission timings of the terminal transmissions of the uplink from the terminal to the base station coincide.

[0047] When simultaneously using the communication method of a terrestrial cellular system using a terrestrial base station 20 (hereinafter referred to as the "terrestrial cellular method") and the communication method of a HAPS cellular system using a HAPS base station 10 (hereinafter referred to as the "HAPS cellular method"), as shown in Fig. 8(a), particularly in the downlink of the service link, due to interference waves from the HAPS base station 10 that transmits signals over a wide area, the communication quality of many terrestrial base station terminals 30(2) located in the terrestrial cell 20C deteriorates. As shown in Fig. 8(b), in the uplink, due to signals transmitted by a very large number of terrestrial base station terminals 30(2), the communication quality of the HAPS base station terminal 30(1) located in the HAPS cell 10C may deteriorate. Therefore, in order to simultaneously use the terrestrial cellular method and the HAPS cellular method, it is necessary to reduce interference.

[0048] In the mobile communication system of this embodiment, the transmission timing and the reception timing are reversed between the HAPS base station 10 and the terrestrial base station 20.

[0049] Fig. 9 is a diagram showing an arrangement example of time slots for the uplink and downlink in the case of performing synchronization control to reverse the transmission timing and the reception timing between a terrestrial base station 20 and a HAPS base station 10 using the TDD method in the mobile communication system according to the embodiment. In each of a plurality of consecutive transmission / reception frames (radio frames) shown in Fig. 9, the transmission timing and the transmission period of the downlink from the terrestrial base station 20 to the terrestrial base station terminal 30(2) coincide with the transmission timing and the transmission period of the uplink from the HAPS base station terminal 30(1) to the HAPS base station 10. On the other hand, the transmission timing and the transmission period of the uplink from the terrestrial base station terminal 30(2) to the terrestrial base station 20 coincide with the transmission timing and the transmission period of the downlink from the HAPS base station 10 to the HAPS base station terminal 30(1).

[0050] Here, the terrestrial base station 20 and the HAPS base station 10 may each adjust the transmission timing to be opposite using the time information acquired by a GNSS (Global Navigation Satellite System) receiver.

[0051] As shown in FIG. 9, by making the transmission timings and reception timings of the HAPS base station 10 and the terrestrial base station 20 opposite to each other in the uplink and downlink, the way of receiving interference changes significantly compared to the case where the transmission timings and reception timings of the HAPS base station 10 and the terrestrial base station 20 shown in FIG. 8 are the same in the uplink and downlink.

[0052] As shown in FIG. 10(a), the downlink of the terrestrial base station 20 becomes the uplink of the service link of the HAPS base station 10. Therefore, the radio wave of the downlink transmission transmitted from the terrestrial base station antenna 21 reaches the HAPS base station antenna 112 as shown in the figure, and the downlink of the terrestrial base station 20 becomes interference with the uplink of the service link of the HAPS base station 10.

[0053] Note that the terrestrial base station terminal 30(2) and the HAPS base station terminal 30(1) are located at a relatively large distance from each other and are both located on the ground. Therefore, there are many shielding objects such as buildings between these terminals, and the interference signal power received when the transmission signal of the uplink of the HAPS base station terminal 30(1) reaches the terrestrial base station terminal 30(2) is generally negligibly small.

[0054] On the other hand, as shown in FIG. 10(b), the uplink of the terrestrial base station 20 becomes the downlink of the service link of the HAPS base station 10. Therefore, the radio wave of the downlink transmission of the service link transmitted from the HAPS base station antenna 112 reaches the terrestrial base station antenna 21 as shown in the figure, and becomes interference with the uplink of the terrestrial base station 20.

[0055] Note that the HAPS base station terminal 30(1) and the terrestrial base station terminal 30(2) are located at a relatively large distance from each other and are both located on the ground. Therefore, there are many shielding objects such as buildings between these terminals, and the interference signal power received when the transmission signal of the uplink of the terrestrial base station terminal 30(2) reaches the HAPS base station terminal 30(1) is generally negligibly small.

[0056] When FIGS. 10(a) and 10(b) are combined, as shown in FIG. 10(c), when the terrestrial cellular system and the HAPS cellular system share the same frequency, the interference can be aggregated between the terrestrial base station antenna 21 and the service link antenna 112 of the HAPS base station. That is, if the interference between the terrestrial base station antenna 21 and the service link antenna 112 of the HAPS base station is reduced, the terrestrial cellular system and the HAPS cellular system can share the same frequency.

[0057] In this embodiment, in order to reduce the interference between the terrestrial base station antenna 21 and the service link antenna 112 of the HAPS base station, an interference suppression unit (also referred to as an "interference canceller") for suppressing the interference is provided in each of the terrestrial base station device 22 in the terrestrial base station 20 and the HAPS base station device 122 in the HAPS base station 10. For example, as shown in FIG. 11(a), the interference suppression unit (interference canceller) 220 mounted on the terrestrial base station device 22 suppresses (hereinafter also referred to as "cancels") the pre-interference from the relay communication station 11 of the HAPS base station. Further, as shown in FIG. 11(b), the interference suppression unit (interference canceller) 125 mounted on the HAPS base station device 122 of the HAPS-GW12 suppresses (cancels) the pre-interference from the terrestrial base station 20.

[0058] FIG. 12 is a diagram showing a configuration example of a mobile communication system in which an interference suppression unit (interference canceller) 220 is provided in the terrestrial base station 20 according to the embodiment. In FIG. 12, the same reference numerals are given to the configurations common to FIGS. 1 to 3 described above, and the descriptions thereof are omitted.

[0059] The interference suppression unit (interference canceller) 220 of this configuration example is provided in the base station device 22 of the terrestrial base station 20, and suppresses (cancels) the interference signal transmitted from the relay communication station 11 of the HAPS base station and reaching the terrestrial base station antenna 21.

[0060] In FIG. 12, the transmission signal s H (t) branched into two transmission signals by the branching unit 125.

[0061] Of the two transmission signals branched at the branching unit 125, one transmission signal s H (t) is transmitted to the HAPS base station terminal 30(1) via the FL antenna 121 and the relay communication station 11 as a downlink signal of the service link from the HAPS base station. A part of the downlink signal transmitted from the HAPS base station antenna 112 of the relay communication station 11 reaches the terrestrial base station antenna 21 of the terrestrial base station 20 as an interference signal with respect to the terrestrial terminal signal transmitted from the terrestrial base station terminal 30(2). Also, the uplink signal (terrestrial terminal signal) of the service link transmitted from the terrestrial base station terminal 30(2) reaches the terrestrial base station antenna 21 of the terrestrial base station as a desired signal. The interference signal from the relay communication station 11 and the desired signal from the terrestrial base station terminal 30(2) are received by the terrestrial base station antenna 21 and input to the interference suppression unit 220 as a received signal of the uplink of the service link.

[0062] The other transmission signal s branched at the branching unit 125 H (t) is transferred as a replica of the transmission signal of the service link transmitted from the HAPS base station (hereinafter also referred to as "transmission replica signal") to the interference suppression unit (interference canceller) 220 provided in the base station apparatus 22 of the terrestrial base station via a wired network (for example, an optical fiber) and the inter-base-station cooperation control apparatus 50.

[0063] The branching unit 125 also performs delay time control to delay the transmission replica signal s H (t) by a predetermined delay time so that the two transmission signals (interference signal, transmission replica signal) branched from the same transmission signal reach the interference suppression unit 220 at the same timing.

[0064] The interference suppression unit 220 of the terrestrial base station apparatus 22 combines the received signal including the desired signal (terrestrial terminal signal) and the interference signal h H s H (t) (transmission signal from the HAPS base station) and the transmission replica signal s HTake the correlation with (t) and estimate the complex received amplitude of the interference signal (the transmission signal from the HAPS base station) h (hereinafter also referred to as the "propagation path response"). H Estimate it.

[0065] Furthermore, the interference suppression unit 220 superimposes the complex received amplitude h H and the transmission replica signal s H (t) from the HAPS base station to generate an interference suppression signal (-h H s H (t)). The interference suppression unit 220 synthesizes the received signal (desired signal + interference signal h H s H (t)) and the interference suppression signal (-h H s H (t)) to suppress (cancel) the interference signal h H s H (t) and input only the desired signal (terrestrial terminal signal) to the receiver 230 of the terrestrial base station apparatus 22.

[0066] FIG. 13 is a diagram showing an example of the configuration of the interference suppression unit (interference canceller) 220 of the terrestrial base station 20 in FIG. 12. In FIG. 13, the same reference numerals are given to the configurations common to FIGS. 1 to 3, 12 described above, and the descriptions thereof are omitted.

[0067] In FIG. 13, the interference suppression unit (interference canceller) 220 includes an interference estimation processing unit 2201, an interference suppression signal generation unit 2202, a distribution unit 2203, a delay unit 2204, and a synthesis unit 2205.

[0068] The interference estimation processing unit 2201 calculates the cross-correlation coefficient using the received signal (desired signal + interference signal) received by the terrestrial base station antenna 21 and the transmission replica signal s H (t) transferred via the base station interconnection control device 50, and estimates the complex received amplitude (propagation path response) h H s H of the interference signal h H Estimate it.

[0069] The interference suppression signal generation unit 2202 uses the interference signal h estimated by the interference estimation processing unit 2201 H sH (t) complex received amplitude (propagation path response) h H is multiplied by the transmitted replica signal s H (t) to generate an interference suppression signal (-h H s H (t)).

[0070] The distribution unit 2203 distributes and supplies the received signal (desired signal + interference signal) received by the terrestrial base station antenna 21 to each of the interference estimation processing unit 2201 and the delay unit 2204.

[0071] The delay unit 2204 delays the received signal by a predetermined delay time so that the received signal (desired signal + interference signal h H s H (t)) and the interference suppression signal (-h H s H (t)) generated from the received signal are input to the combining unit 2205 at the same timing.

[0072] The combining unit 2205 combines the interference suppression signal (-h H s H (t)) generated by the interference suppression signal generation unit 2202 with the received signal (desired signal + interference signal h H s H (t)) to suppress (cancel) the interference signal h H s H (t) and demodulate the desired signal.

[0073] FIG. 14 is a diagram showing a configuration example of a mobile communication system in which an interference suppression unit (interference canceller) 126 is provided in the HAPS base station 10 according to the embodiment. In FIG. 14, the same reference numerals are given to the configurations common to FIGS. 1 to 3 described above, and the descriptions thereof are omitted.

[0074] The interference suppression unit (interference canceller) 126 of this configuration example is provided in the HAPS base station device 122 of the HAPS-GW12, and suppresses (cancels) the interference signal transmitted from the terrestrial base station antenna 21 and reaching the service link antenna 112 of the relay communication station 11 of the HAPS base station.

[0075] In FIG. 14, the transmission signal s M (t) output from the terrestrial base station apparatus 22 is branched into two transmission signals at the branching unit 23.

[0076] Of the two transmission signals branched at the branching unit 23, one transmission signal s M (t) is transmitted as a downlink signal of the service link from the terrestrial base station 20 to the terrestrial base station terminal 30(2) via the terrestrial base station antenna 21. A part of the downlink signal transmitted from the terrestrial base station antenna 21 reaches the HAPS base station antenna 112 of the relay communication station 11 of the HAPS base station as an interference signal with respect to the HAPS terminal signal transmitted from the HAPS base station terminal 30(1). Further, the uplink signal (HAPS terminal signal) of the service link transmitted from the HAPS base station terminal 30(1) reaches the HAPS base station antenna 112 of the relay communication station 11 as a desired signal. The interference signal from the terrestrial base station 20 and the desired signal from the HAPS base station terminal 30(1) are received by the HAPS base station antenna 112 of the relay communication station 11 and input to the interference suppression unit 126 as a received signal of the uplink of the service link via the FL antenna 111 of the relay communication station 11 and the FL antenna 121 of the HAPS-GW12.

[0077] The other transmission signal s M (t) branched at the branching unit 23 is transferred as a replica of the transmission signal of the service link (transmission replica signal) transmitted from the terrestrial base station apparatus 22 to the interference suppression unit (interference canceller) 126 provided in the HAPS base station apparatus 122 of the HAPS-GW12 via a wired network (for example, an optical fiber) and the inter-base-station cooperation control device 50.

[0078] The branching unit 23 also performs delay time control to delay the transmission replica signal s M (t) transferred to the inter-base-station cooperation control device 50 by a predetermined delay time so that the two transmission signals (interference signal, transmission replica signal) branched from the same transmission signal reach the interference suppression unit 126 at the same timing.

[0079] The interference suppression unit (interference canceller) 126 of the HAPS base station apparatus 122 correlates the received signal including the desired signal (ground terminal signal) and the interference signal h M s M (t) (transmission signal from the terrestrial base station) with the transmission replica signal s M (t), and estimates the complex received amplitude of the interference signal (transmission signal from the HAPS base station) (hereinafter also referred to as "propagation path response") h M to estimate.

[0080] Furthermore, the interference suppression unit (interference canceller) 126 superimposes the complex received amplitude h M and the transmission replica signal s from the terrestrial base station M (t) to generate an interference suppression signal (-h M s M (t)). The interference suppression unit 126 synthesizes the received signal (desired signal + interference signal h M s M (t)) and the interference suppression signal (-h M s M (t)) to suppress (cancel) the interference signal h M s M (t), and inputs only the desired signal (ground terminal signal) to the receiver 127 of the HAPS base station apparatus 122.

[0081] FIG. 15 is a diagram showing a configuration example of the interference suppression unit (interference canceller) 126 of the HAPS base station 10 in FIG. 14. In FIG. 15, the same reference numerals are given to the configurations common to FIGS. 1 to 3 and FIG. 14 described above, and the descriptions thereof are omitted.

[0082] In FIG. 15, the interference suppression unit (interference canceller) 126 includes an interference estimation processing unit 1261, an interference suppression signal generation unit 1262, a distribution unit 1263, a delay unit 1264, and a synthesis unit 1265.

[0083] The interference estimation processing unit 1261 calculates the cross-correlation coefficient using the received signals (desired signal + interference signal) received by the FL antenna 111 of the relay communication station 11 and the FL antenna 121 of the HAPS-GW 12, and the transmission replica signal s M (t) transferred via the inter-base station cooperation control device 50, and estimates the complex received amplitude (propagation path response) h M s M (t) of the interference signal h M .

[0084] The interference suppression signal generation unit 1262 multiplies the complex received amplitude (propagation path response) h M s M (t) of the interference signal h M estimated by the interference estimation processing unit 1261 by the transmission replica signal s M (t) to generate an interference suppression signal (-h M s M (t)).

[0085] The distribution unit 1263 distributes and supplies the received signal (desired signal + interference signal) received by the FL antenna 121 of the HAPS-GW 12 to each of the interference estimation processing unit 1261 and the delay unit 1264.

[0086] The delay unit 1264 delays the received signal by a predetermined delay time so that the received signal (desired signal + interference signal h M s M (t)) distributed by the distribution unit 1263 and the interference suppression signal (-h M s M (t)) generated from the received signal are input to the combining unit 1265 at the same timing.

[0087] The combining unit 1265 combines the interference suppression signal (-h M s M (t)) generated by the interference suppression signal generation unit 1262 with the received signal (desired signal + interference signal h M s M (t)) to suppress (cancel) the interference signal h M s M (t) and demodulate the desired signal.

[0088] FIG. 16 is a diagram showing a configuration example of a mobile communication system in which interference suppression units (interference cancellers) 220 and 126 are provided in a centralized base station (hereinafter also referred to as “centralized base station component”) 60 according to an embodiment. FIG. 16 shows a configuration example including a centralized base station component 60 in which a terrestrial base station device 22, a HAPS base station device 122, and a centralized interference suppression unit (centralized interference canceller) 600 are installed at the same location or configured within the same device. In FIG. 16, solid arrow lines are downlink transmission signals transmitted from each base station device, broken arrow lines are interference signals, one-dot chain arrow lines are uplink reception signals received by each base station device, and two-dot chain arrow lines are transmission replica signals. In FIG. 16, components common to FIGS. 1 to 3 and FIGS. 12 to 15 described above are denoted by the same reference numerals, and their descriptions are omitted.

[0089] In FIG. 16, the centralized base station component 60 is connected to the HAPS-GW12 of the HAPS base station 10 and the terrestrial base station antenna 21 of the terrestrial base station 20 by a DAS (distributed antenna system) configured using an optical cable or the like. For example, the communication path between the centralized base station component 60 and the HAPS-GW12 of the HAPS base station 10 is composed of a DAS slave unit 61(1), an optical fiber 62(1), and a DAS master unit 601(1) in the centralized base station component 60. Also, the communication path between the centralized base station component 60 and the terrestrial base station antenna 21 of the terrestrial base station 20 is composed of a DAS slave unit 61(2), an optical fiber 62(2), and a DAS master unit 601(2) in the centralized base station component 60.

[0090] In the centralized base station component 60, the downlink transmission signal output from the HAPS base station device 122 passes through a DUP (duplexer) (also referred to as “antenna duplexer”) 602(1), a branching unit 603(1), and a DUP 604(1), and is transmitted via the DAS master unit 601(1), the optical fiber 62(1), and the DAS slave unit 61(1) to reach the HAPS-GW12. The downlink transmission signal branched by the branching unit 603(1) is input as a transmission replica signal of the HAPS base station to the interference suppression unit 220 of the terrestrial base station within the centralized base station component 60.

[0091] The uplink received signal output from HAPS-GW12 (including the interference signal from the terrestrial base station) is transmitted via the DAS slave unit 61(1), the optical fiber 62(1), and the DAS master unit 601(1), and is input to the interference suppression unit 126 of the HAPS base station via DUP604(1). The interference suppression unit 126 outputs the uplink received signal with the interference signal from the terrestrial base station suppressed. The uplink received signal after the interference signal is suppressed and output from the interference suppression unit 126 reaches the receiver of the HAPS base station device 122 via DUP602(1).

[0092] Also, in the centralized base station component 60, the downlink transmission signal output from the terrestrial base station device 22 passes through DUP602(2), the branching unit 603(2), and DUP604(2), and is transmitted via the DAS master unit 601(2), the optical fiber 62(2), and the DAS slave unit 61(2), and reaches the terrestrial base station antenna 21 of the terrestrial base station 20. The downlink transmission signal branched by the branching unit 603(2) is input to the interference suppression unit 126 of the HAPS base station within the centralized base station component 60 as the transmission replica signal of the terrestrial base station.

[0093] The uplink received signal output from the terrestrial base station antenna 21 of the terrestrial base station 20 (including the interference signal from the HAPS base station) is transmitted via the DAS slave unit 61(2), the optical fiber 62(2), and the DAS master unit 601(2), and is input to the interference suppression unit 220 of the terrestrial base station via DUP604(2). The interference suppression unit 220 outputs the uplink received signal with the interference signal from the HAPS base station suppressed. The uplink received signal after the interference signal is suppressed and output from the interference suppression unit 220 reaches the receiver of the terrestrial base station device 22 via DUP602(2).

[0094] In the system equipped with the centralized base station component 60 in FIG. 16, a large-scale inter-network cooperation control system that spans multiple different base stations is not required, and the interference suppression unit (interference canceller) of the HAPS base station and the interference suppression unit (interference canceller) of the terrestrial base station can be simply configured. Also, a large-scale inter-network cooperation control system for matching the transmission and reception timings of the terrestrial base station 20 and the HAPS base station 10 is not required, and synchronization between base stations can be easily established within the centralized base station component 60.

[0095] FIGS. 17 and 18 are diagrams each showing an example of control of the transmission and reception timings between the terrestrial base station 20 and the HAPS base station 10 according to the embodiment. In the mobile communication system of this embodiment, since it is necessary to reverse the transmission and reception timings of the terrestrial base station 20 and the HAPS base station 10, the system interconnection control device 50 adjusts the transmission and reception timings of the terrestrial base station 20 and the HAPS base station 10 so that the transmission and reception frame times of the terrestrial base station 20 and the HAPS base station 10 are reversed. In the example of FIG. 17, the adjustment of the transmission and reception timings is performed by the HAPS-GW12. In the example of FIG. 18, the adjustment of the transmission and reception timings is performed by the relay communication station 11 mounted on the HAPS100.

[0096] As described above, according to this embodiment using the TDD system as the transmission and reception method, it is possible to share the same frequency in each service link between each of the service link antennas (HAPS base station antenna) of the HAPS base station (first base station) and the service link antennas (terrestrial base station antenna) of the terrestrial base station and the terminal, and it is possible to share the same frequency as in the inter-cell interference control technology (eICIC) shown in FIG. 5, but the problem of causing a decrease in the communication capacity of the terminal can be overcome.

[0097] Also, according to this embodiment, by sharing the frequencies of the HAPS service link and the terrestrial base station, the frequency utilization rate can be improved by two times.

[0098] Moreover, according to the present embodiment, it can be realized by changing the transmission and reception timings of the terrestrial base station 20 and the HAPS base station 10 using a normal TDD system (such as 5G) without any special changes.

[0099] Moreover, according to the present embodiment, interference in the uplink and downlink of the service link of each base station is reduced by the terrestrial base station interference canceller (interference suppression unit 220 of the terrestrial base station device 22) and the HAPS base station interference canceller (interference suppression unit 126 of the HAPS base station device 122) provided in each of the terrestrial base station 20 and the HAPS base station 10, and frequency sharing between the terrestrial base station and the HAPS base station can be realized.

[0100] Moreover, according to the present embodiment, for both the terrestrial base station 20 and the HAPS base station 10, array antenna control using a massive antenna or the like is not required to avoid interference.

[0101] Moreover, according to the present embodiment, frequency sharing can be realized when the terrestrial base station antenna 21 and the HAPS base station antenna 112 do not include, for example, a massive antenna and null forming cannot be performed.

[0102] Moreover, according to the present embodiment, interference can be suppressed by applying the terrestrial base station interference canceller (interference suppression unit 220 of the terrestrial base station device 22) and the HAPS base station interference canceller (interference suppression unit 126 of the HAPS base station device 122) using a network cooperation control system (base station - to - base station cooperation control device 50) for both the terrestrial base station 20 and the HAPS base station 10. Moreover, the terrestrial base station interference canceller and the HAPS base station interference canceller have the same configuration.

[0103] In particular, according to the present embodiment, in the centralized base station configuration unit 60 in which one or more terrestrial base station devices 22, the HAPS base station device 122, and the centralized interference suppression unit (centralized interference canceller) 600 are installed at the same location or configured within the same device, a large-scale inter-network cooperation control system (inter-base station cooperation control device) that spans different base stations is unnecessary, and the HAPS base station interference canceller and the terrestrial base station interference canceller can be easily configured.

[0104] Further, according to the present embodiment, no special device or control is required for the terrestrial base station 20 and the HAPS base station 10 to share frequencies.

[0105] Also, according to the present embodiment, the transmission timing adjustment between the terrestrial base station 20 and the HAPS base station 10 can be easily realized by the inter-system (inter-base station) cooperation control device 50.

[0106] The present invention can improve the frequency utilization efficiency in the HAPS base station and the terrestrial base station and prevent a decrease in the communication capacity of the terminal, and can provide a system capable of realizing frequency sharing between the HAPS base station and the terrestrial base station without adding a special device to the HAPS base station and the terrestrial base station, thus contributing to the achievement of Sustainable Development Goal (SDG) 9, "Build the infrastructure for industry and innovation."

[0107] Further, the present invention can also be applied when sharing frequencies between the various systems exemplified in the following (A) to (D) and the terrestrial base station. (A) Frequency sharing between the HAPS base station and the terrestrial base station (B) Frequency sharing between a helicopter-mounted wireless relay system or a UAV-mounted wireless relay system during a disaster and the terrestrial base station (C) Frequency sharing between a drone-mounted wireless relay system and the terrestrial base station (D) Frequency sharing between a satellite communication system in geostationary, medium-earth orbit, or low-earth orbit and the terrestrial base station

[0108] Note that the processing steps described in this specification, as well as the components of the mobile communication system, high-altitude relay base station, HAPS cellular system, terrestrial base station, terrestrial cellular system, relay communication station, HAPS-GW, terminal (user device, mobile station, mobile unit), and base station interworking control device can be implemented by various means. For example, these processing steps and components may be implemented in hardware, firmware, software, or a combination thereof.

[0109] Regarding hardware implementation, means such as processing units used to realize the above steps and components in an entity (for example, various wireless communication devices, wireless relay devices, NodeB, servers, gateways, switches, computers, hard disk drive devices, or optical disk drive devices) 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 a combination thereof.

[0110] In addition, for firmware and / or software implementations, the means used to implement the above components may be a program (e.g., code such as procedures, functions, modules, instructions, etc.) that executes the functions described herein. Generally, any computer / processor-readable medium that clearly embodies the firmware and / or software code may be used to implement means such as processing units for realizing the above steps and components described herein. For example, the firmware and / or software code may be stored in a memory, such as in a control device, and executed by a computer or processor. The memory may be implemented inside the computer or processor, or may be implemented outside the processor. Also, the firmware and / or software code may be stored in a computer or processor-readable medium such as, for example, random access memory (RAM), read only memory (ROM), non-volatile random access memory (NVRAM), programmable read only memory (PROM), electrically erasable 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 cause the computer or processor to execute the functional aspects described herein.

[0111] Also, the description of the embodiments disclosed herein is provided to enable a person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

Description of Reference Numerals

[0112] 10: HAPS Base Station (High Altitude Relay Type Base Station) 10C: HAPS Cell 11: Relay Communication Station 12: HAPS-GW 15: GPS Receiver 20: Ground Base Station 20C: Ground Cell 21: Ground Base Station Antenna (Service Link Antenna) 22: Base Station Equipment 23: Splitter 30: Terminal 30(1): HAPS Base Station Terminal 30(2): Ground Base Station Terminal 40: Core Network 50: Base Station Interconnection Control Device 60: Centralized Base Station Component 600: Centralized Interference Suppression Unit (Centralized Interference Canceler) 100: HAPS 111: FL Antenna 112: HAPS Base Station Antenna (Service Link Antenna) 113: Repeater 114: Frequency Converter 115: Base Station Equipment 116: Feeder Link Transceiver 121: FL Antenna 122: Base Station Equipment 123: Frequency Converter 124: Feeder Link Transceiver 125: Splitter 126: Interference Canceler (HAPS Base Station) 1261: Interference Estimation Processing Unit 1262: Interference Suppression Signal Generation Unit 1263: Distribution Unit 1264: Delay Unit 1265: Combiner 127: Receiver 220: Interference Canceler (Ground Base Station) 2201: Interference Estimation Processing Unit 2202: Interference suppression signal generation unit 2203: Distribution unit 2204: Delay unit 2205: Combining unit 230: Receiver

Claims

【Claim 1】 An aerial relay type base station that performs wireless communication with a terminal via a service link antenna of a relay communication station provided on an aircraft or a floating body located in the sky, and one or more terrestrial base stations that perform wireless communication with the terminal via a service link antenna arranged on the ground or at sea, wherein the aerial relay type base station and the terrestrial base station are a mobile communication system that is time-synchronized with each other, The aerial relay type base station and the terrestrial base station each perform wireless communication of a service link with the terminal by a TDD (Time Division Duplex) method using the same frequency, The transmission timing and reception timing of the wireless communication in the TDD method in the service link are opposite to each other between the aerial relay type base station and the terrestrial base station, The terrestrial base station, Branches a downlink transmission signal transmitted from the terrestrial base station and transfers it to the aerial relay type base station as a transmission replica signal, Performs correlation processing between a reception signal of an uplink of the terrestrial base station including an interference signal from the aerial relay type base station that causes interference to the uplink of the terrestrial base station and the transmission replica signal transferred from the aerial relay type base station, and estimates a complex reception amplitude of the interference signal from the aerial relay type base station, Using the estimation result of the complex reception amplitude of the interference signal from the aerial relay type base station and the transmission replica signal, generates an interference suppression signal for suppressing the interference signal from the aerial relay type base station, By synthesizing the reception signal of the uplink of the terrestrial base station and the interference suppression signal, suppresses the interference signal from the aerial relay type base station included in the reception signal of the uplink of the terrestrial base station, The aerial relay type base station, Branches a downlink transmission signal transmitted from the aerial relay type base station and transfers it to the terrestrial base station as a transmission replica signal, Performs correlation processing between a reception signal of an uplink of the aerial relay type base station including an interference signal from the terrestrial base station that causes interference to the uplink of the aerial relay type base station and the transmission replica signal transferred from the terrestrial base station, and estimates a complex reception amplitude of the interference signal from the terrestrial base station, Using the estimation result of the complex reception amplitude of the interference signal from the terrestrial base station and the transmission replica signal, generates an interference suppression signal for suppressing the interference signal from the terrestrial base station, By synthesizing the received signal of the uplink of the aerial relay base station and the interference suppression signal, the interference signal from the terrestrial base station included in the received signal of the uplink of the aerial relay base station is suppressed. A mobile communication system characterized by the above. **Claim 2** In the mobile communication system according to claim 1, the relay communication station mounted on the aircraft or the floating body is composed of a repeater relay device that relays without reproducing the transmission and reception signals, and is characterized by a mobile communication system. **Claim 3** In the mobile communication system according to claim 1, the relay communication station mounted on the aircraft or the floating body is composed of a base station device that reproduces the transmission and reception signals, remodulates the reproduced signals, and relays them, and is characterized by a mobile communication system. **Claim 4** In the mobile communication system according to any one of claims 1 to 3, further comprising a base station interconnection control device for controlling between the aerial relay base station and the terrestrial base station, The base station interconnection control device uses the time information of GNSS (Global Navigation Satellite System) received by the aerial relay base station via the gateway device and the time information of GNSS (Global Navigation Satellite System) received by the terrestrial base station to adjust the transmission timing so that transmission and reception are reversed, respectively. A mobile communication system characterized by the above. **Claim 5** In the mobile communication system according to any one of claims 1 to 3, further comprising a base station interconnection control device for controlling between the aerial relay base station and the terrestrial base station, The base station interconnection control device transfers the transmission replica signal from the terrestrial base station to the aerial relay base station and transfers the transmission replica signal from the aerial relay base station to the terrestrial base station. A mobile communication system characterized by the above. **Claim 6** In the mobile communication system according to any one of claims 1 to 3, comprising a centralized base station configuration unit in which the terrestrial base station and the aerial relay base station are installed at the same location or configured within the same device, The centralized base station configuration unit estimates the complex received amplitude of the interference signal from the aerial relay base station in the terrestrial base station, generates the interference suppression signal, and suppresses the interference signal from the aerial relay base station, estimates the complex received amplitude of the interference signal from the terrestrial base station in the aerial relay base station, generates the interference suppression signal, and suppresses the interference signal from the terrestrial base station, and A mobile communication system characterized by the above. **Claim 7** In the mobile communication system according to any one of claims 1 to 3, the aircraft or the floating body is a communication satellite, a UAV (Unmanned Aerial Vehicle) flying at an altitude of 18 km or less, or a HAPS flying in the stratosphere at an altitude of 18 km or more, and the mobile communication system is characterized by this.

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