Wireless communication apparatus and communication system

Abstract

To provide a radio communication device capable of reducing a guard time when performing communication of a TDD system.SOLUTION: A radio communication device performs radio communication of a TDD (time division duplex) system. The wireless communication device includes means for setting a time length of a transmission and reception period in which a transmission period for transmitting a signal to a target device and a reception period for receiving a signal from the target device in wireless communication of a TDD scheme are continuous to the same time length as a round-trip delay time of a wireless signal between the wireless communication device and the target device, and means for periodically performing transmission to the target device and reception from the target device by repeating the transmission and reception period.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a wireless communication device and a communication system. [Background technology]

[0002] Conventionally, there have been known radio relay devices that can stay in the sky, such as high altitude platform stations (HAPS) (also called "high altitude pseudo satellites") (see, for example, Patent Document 1). The communication line in this radio relay device is composed of a feeder link (relay radio section) between the radio relay device and a gateway (GW) device on the mobile communication network side, and a service link between the radio relay device and a terminal device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2016 / 0046387 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned airborne radio communication devices such as radio repeaters and gateways (GW) there is a need to reduce the guard time when performing TDD (Time Division Duplex) communications. [Means for solving the problem]

[0005] A wireless communication device according to one aspect of the present invention is a wireless communication device that performs wireless communication using a TDD (Time Division Duplex) system, and includes: means for setting a duration of a transmission / reception period, in which a transmission period for transmitting a signal to a target device and a reception period for receiving a signal from the target device are consecutive, to the same duration as a round-trip delay time of a wireless signal between the wireless communication device and the target device; and means for periodically transmitting to and receiving from the target device by repeating the transmission / reception period.

[0006] The wireless communication device may further include means for changing the transmission / reception period in response to a change in the round-trip delay time, wherein the transmission / reception period may be changed in response to a change in at least one of a distance between the wireless communication device and the target device and a delay time of a wireless signal between the wireless communication device and the target device.

[0007] In the wireless communication device, a ratio between the transmission period and the reception period in the transmission / reception period may be a fixed ratio.

[0008] The wireless communication device may further comprise means for changing a ratio between the transmission period and the reception period in the transmission / reception period.

[0009] The wireless communication device may be provided with a means for adjusting the signal length of a transmission signal to be transmitted to the target device based on at least one of the distance between the wireless communication device and the target device and the delay time of the wireless signal between the wireless communication device and the target device.

[0010] The wireless communication device may further include means for setting a guard time, the guard time having a time length corresponding to the difference between a maximum delay time and a minimum delay time of the wireless signal between the wireless communication device and the target device, before and after the transmission / reception period. Here, the wireless communication device may further include means for adjusting the guard time based on at least one of a distance between the wireless communication device and the target device and a delay time of the wireless signal between the wireless communication device and the target device.

[0011] The wireless communication device may include a transmit / receive switching timing signal generation unit that generates a transmit / receive switching timing signal that switches between transmitting to the target device and receiving from the target device so that the length of a transmission / reception period in which a transmission period for transmitting a signal to the target device and a reception period for receiving a signal from the target device in the TDD wireless communication are consecutive is set to the same length as the round-trip delay time of the wireless signal between the wireless communication device and the target device, and a transmit signal timing adjustment unit that adjusts the transmission timing of transmitting a transmission signal to the target device based on the transmit / receive switching timing signal so that the transmission / reception period is repeated to periodically transmit to and receive from the target device.

[0012] The wireless communication device may be a non-regenerative wireless relay device that relays FDD (Frequency Division Duplex) communication between a base station device and a terminal device. Here, the wireless relay device (wireless communication device) may include means for converting between the FDD signal transmitted and received in a wireless section of a service link between the terminal device and the wireless relay device and a TDD (Time Division Duplex) signal transmitted and received in a relay wireless section between the base station device and a gateway device connected to the base station device, and may transmit and receive wireless signals in the TDD system in the relay wireless section between the gateway device and the wireless relay device.

[0013] The wireless communication device may be a gateway device connected to a base station device and capable of wireless communication with a non-regenerative wireless relay device that relays FDD (Frequency Division Duplex) communication between the base station device and a terminal device. Here, the gateway device (wireless communication device) may include means for converting between an FDD signal transmitted to and received from the base station device and a TDD (Time Division Duplex) signal transmitted to and received in a relay wireless section between the gateway device and the wireless relay device, and may transmit and receive wireless signals in the TDD system in the relay wireless section between the gateway device and the wireless relay device.

[0014] The wireless communication device may be a base station-type wireless relay device having a base station device connected to a core network of a mobile communication network via a backhaul line of a relay wireless section between the base station device and a gateway device, and transmitting and receiving wireless signals in the relay wireless section using the TDD method.

[0015] The wireless communication device may be a gateway device that is connected to a core network of a mobile communication network and transmits and receives wireless signals in the TDD system over a backhaul line of a relay wireless section between the wireless communication device and a base station type wireless communication device.

[0016] A communication system according to another aspect of the present invention may include the wireless relay device and the gateway device.

[0017] In the communication system, the radio relay device may be an airborne relay type radio relay device that is installed on the body of an aircraft or floating body located in the sky, and that forms one or more cells toward a service area on the ground or sea via a service link antenna and communicates wirelessly with one or more terminal devices located in the cell.

[0018] In the communication system, the frequency band of the TDD radio signal and the frequency band of the FDD radio signal may be different from each other.

[0019] In the communication system, the frequency band of the TDD radio signal may be a millimeter wave frequency band of 20 GHz or more and 300 GHz or less, and the frequency band of the FDD radio signal may be the frequency band of 10 GHz or less.

[0020] In the radio relay device, the frequency band of the TDD radio signal and the frequency band of the FDD radio signal may be different from each other.

[0021] In the radio relay device, the frequency band of the TDD radio signal may be a millimeter wave frequency band of 20 GHz or more and 300 GHz or less, and the frequency band of the FDD radio signal may be the frequency band of 10 GHz or less.

[0022] In the wireless relay device, known signals and control data used to control the wireless relay device and known signals and control data used to control the gateway device may be placed in a guard time between a communication band time of a forward link and a communication band time of a reverse link that are alternately repeated in the relay wireless section.

[0023] The radio relay device may be an airborne relay type radio relay device that is installed on the body of an aircraft or floating body located in the sky, and forms one or more cells toward a service area on the ground or sea via a service link antenna, and communicates wirelessly with one or more terminal devices located in the cell.

[0024] The radio relay device may form multiple cells using the same frequency corresponding to multiple base station devices in the service link, and may time-multiplex radio signals corresponding to the multiple cells in the relay radio section in the feeder link.

[0025] A gateway device according to still another aspect of the present invention is a gateway device connected to a base station device and capable of wireless communication with a non-regenerative wireless relay device that relays FDD (Frequency Division Duplex) communications between the base station device and a terminal device, the gateway device having means for converting between FDD signals transmitted to and received from the base station device and TDD (Time Division Duplex) signals transmitted to and received in a relay wireless section between the gateway device and the wireless relay device, and transmitting and receiving wireless signals in the TDD system in the relay wireless section between the gateway device and the wireless relay device.

[0026] In the gateway device, the frequency band of the TDD radio signal and the frequency band of the FDD radio signal may be different from each other.

[0027] In the gateway device, the frequency band of the TDD radio signal may be a millimeter wave frequency band of 20 GHz or more and 300 GHz or less, and the frequency band of the FDD radio signal may be the frequency band of 10 GHz or less.

[0028] In the gateway device, known signals and control data used to control the wireless relay device and known signals and control data used to control the gateway device may be arranged in a guard time between a communication band time of a forward link and a communication band time of a reverse link that are alternately repeated in the relay wireless section.

[0029] The program that performs at least one of the processes of setting the time length of the transmission / reception period, changing the transmission / reception period, changing the ratio of the transmission period to the reception period in the transmission / reception period, adjusting the signal length of the transmission signal, setting the guard time, adjusting the guard time, generating the transmission / reception switching timing signal, and adjusting the transmission timing of the transmission signal may include a machine-learned model. [Effects of the Invention]

[0030] According to the present invention, it is possible to reduce the guard time when performing TDD communication in a wireless communication device such as a wireless relay device and a gateway device that relays communication between a base station device and a terminal device. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of the overall configuration of a communication system with a single cell configuration corresponding to a single base station device according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram illustrating an example of communication bands of the FDD system in the base station device and the terminal device of the communication system according to the embodiment. [Figure 3] FIG. 3 is an explanatory diagram showing an example of a communication band of the TDD system in a feeder link (relay wireless section) of the communication system according to the embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing an example of a known control signal arranged in a guard time between a communication band time of a downlink (forward link) and a communication band time of an uplink (reverse link) of a TDD system in a feeder link (relay wireless section) in a communication system according to an embodiment. [Figure 5] FIG. 5 is an explanatory diagram illustrating an example of the overall configuration of a communication system with a multi-cell configuration corresponding to a plurality of base station devices according to the embodiment. [Figure 6] FIG. 6 is an explanatory diagram showing an example of time variations in the communication bands of the FDD downlink (forward link) and uplink (reverse link) in a plurality of base station devices in the communication system of FIG. 5, the TDD downlink and uplink in the feeder link (relay wireless section), and the FDD communication band in the service link. [Figure 7] FIG. 7 is an explanatory diagram showing an example of an AGC pilot signal and supervisory control data arranged in a guard time between a communication band time of a downlink (forward link) and a communication band time of an uplink (reverse link) of a TDD system in a feeder link (relay wireless section) in the communication system of FIG. 5. [Figure 8] FIG. 8 is an explanatory diagram showing an example of the positional relationship between a gateway device (terrestrial GW) and a HAPS in a communication system according to an embodiment. [Figure 9] FIG. 9 is an explanatory diagram showing an example of transmission and reception timing of forward link signals and reverse link signals between a gateway device (terrestrial GW) and a HAPS in a communication system according to a reference example. [Figure 10] FIG. 10 is an explanatory diagram showing an example of transmission and reception timing of forward link signals and reverse link signals between a gateway device (terrestrial GW) and a HAPS in the communication system of FIG. [Figure 11] FIG. 11 is an explanatory diagram showing another example of transmission and reception timing of forward link signals and reverse link signals between the gateway device (terrestrial GW) and the HAPS in the communication system of FIG. [Figure 12]FIG. 12 is an explanatory diagram showing an example of changing the time ratio between the transmission period of the forward link signal and the reception period of the reverse link signal in the communication system of FIG. [Figure 13] FIG. 13 is an explanatory diagram showing an example of the positional relationship between a gateway device (terrestrial GW) and a HAPS that moves, turns, rotates, etc. in the sky in a communication system according to an embodiment. [Figure 14] FIG. 14 is an explanatory diagram showing an example of the transmission and reception timing of the forward link signal and the reverse link signal when the distance between the gateway device (terrestrial GW) and the HAPS in the communication system of FIG. 13 is short (d1). [Figure 15] FIG. 15 is an explanatory diagram showing an example of the transmission and reception timing of the forward link signal and the reverse link signal when the distance between the gateway device (terrestrial GW) and the HAPS in the communication system of FIG. 13 is long (d2>d1). [Figure 16] FIG. 16 is an explanatory diagram showing an example of changing the time ratio between the transmission period of the forward link signal and the reception period of the reverse link signal in the communication system of FIG. [Figure 17] FIG. 17 is an explanatory diagram showing another example of the transmission and reception timing of the forward link signal and the reverse link signal when the distance between the gateway device (terrestrial GW) and the HAPS in the communication system of FIG. 13 is short (d1). [Figure 18] FIG. 18 is an explanatory diagram showing another example of transmission and reception of forward link signals and reverse link signals when the distance between the gateway device (terrestrial GW) and the HAPS in the communication system of FIG. 13 is long (d2>d1). [Figure 19] FIG. 19 is an explanatory diagram showing an example of changing the time length of the transmission and reception period depending on the distance between the gateway device (terrestrial GW) and the HAPS in the communication system of FIG. [Figure 20] FIG. 20 is an explanatory diagram showing another example of changing the time ratio between the transmission period of the forward link signal and the reception period of the reverse link signal in the communication system of FIG. [Figure 21]FIG. 21 is a block diagram showing an example of the configuration of the main parts of a terrestrial feeder link device provided in a gateway device (terrestrial GW) and an aerial feeder link device provided in a radio relay device of a HAPS in a communication system according to an embodiment. [Figure 22] 22(a) is an explanatory diagram showing an example of a transmit / receive switching timing signal applicable to a terrestrial feeder link device of a gateway device (terrestrial GW) in a communication system according to an embodiment. FIG. 22(b) is an explanatory diagram showing an example of a transmit / receive switching timing signal applicable to an overhead feeder link device of a HAPS wireless repeater device in a communication system according to an embodiment. [Figure 23] 23(a) is an explanatory diagram showing another example of a transmit-receive switching timing signal applicable to a terrestrial feeder link device of a gateway device (terrestrial GW) in the communication system according to the embodiment. FIG. 23(b) is an explanatory diagram showing another example of a transmit-receive switching timing signal applicable to an overhead feeder link device of a HAPS radio relay device in the communication system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A communication system according to an embodiment described in this specification includes a wireless relay device (wireless communication device) that converts a relay wireless section (feeder link) to a TDD (time division duplex) system and relays the FDD (frequency division duplex) system wireless relay between a base station and a terminal device, in which the transmission frequency and reception frequency are different from each other, and a gateway device (wireless communication device) that performs TDD wireless communication with the wireless relay device via the relay wireless section (feeder link).

[0033] 1 is an explanatory diagram showing an example of the overall configuration of a communication system with a single cell configuration corresponding to a single base station device 80 according to an embodiment. Note that the communication system according to this embodiment is suitable for realizing a three-dimensional network of fourth-generation or later-generation mobile communications that supports simultaneous connection to multiple terminal devices (hereinafter also referred to as "UE" (user equipment)) 60, low latency, etc. Also, mobile communication standards applicable to the communication system, radio relay device, base station device, gateway device, and terminal device disclosed in this specification include fourth-generation mobile communication standards and fourth-generation or later-generation mobile communication standards.

[0034] As shown in Fig. 1, the communication system includes a high altitude platform station (HAPS) (also called a "high altitude pseudo satellite" or "stratospheric platform") 10 having an airborne radio relay device that constitutes an airborne platform. The HAPS 10 is an airborne or levitating communication platform that is located in an airspace at a predetermined altitude and forms a three-dimensional cell (three-dimensional area) in a cell formation target airspace at the predetermined altitude toward a target service area 20A.

[0035] HAPS10 is an air vehicle or floating body 100 that is controlled by autonomous or external control to float or fly in a high-altitude airspace (floating airspace) at 100 km or less above ground or sea level, and is equipped with a wireless relay device (wireless communication device) (hereinafter also referred to as a "relay communication station") 110. The airspace in which HAPS10 is located may be, for example, stratospheric airspace at an altitude of 18 km or more and 50 km or less. This airspace may also be an airspace with relatively stable weather conditions at an altitude of 15 km or more and 25 km or less, and particularly may be an airspace at an altitude of approximately 20 km.

[0036] The cell formation target airspace, which is the target airspace in which HAPS10 will form a three-dimensional cell, may be an airspace within a predetermined altitude range (e.g., an altitude range of 50 m or more and 1000 m or less) located between the airspace in which HAPS10 is located and the cell formation area near the ground covered by a base station such as a conventional macrocell base station (e.g., an LTE eNodeB or a next-generation gNodeB).

[0037] The target airspace for cell formation may be above the sea, a river, or a lake. The 3D cell formed by HAPS 10 may also be formed to reach the ground or sea surface to enable communication with UE (terminal equipment) 60 located on the ground or sea.

[0038] The HAPS 10 communicates wirelessly with the UE 60 via a service link antenna (also referred to as an "SL antenna") 111 of a relay communication station (wireless communication device) 110 provided on an airframe 100, such as an air vehicle or a floating body, located in the sky. The HAPS 10 is equipped with at least one of a battery and a solar power generation system, for example, and can fly using electric power. The HAPS 10 may be a solar plane-type HAPS as shown in the figure, or an airship-type HAPS. The HAPS 10 provided with the relay communication station 110 may be an artificial satellite (e.g., a communication satellite), a balloon, or an unmanned aerial vehicle (UAV) such as a drone or unmanned aircraft systems (UAS). The HAPS 10 may be equipped with at least one of a battery and an engine as a power source. The UAV may be, for example, an unmanned aerial vehicle that runs on fuel or a drone that runs on a battery or the like.

[0039] The relay communication station 110 includes a service link antenna (SL antenna) 111 and a feeder link antenna (hereinafter also referred to as an "FL antenna") 112. The relay communication station 110 can perform service link SL communication with the UE 60 via the SL antenna 111. The SL antenna 111 is, for example, a beamforming controllable array antenna that can control the direction and width of a beam that forms a cell 20C in the target service area 20A. The area through which the beam passes in the cell formation target airspace is the three-dimensional cell 20C. The multiple communication areas that the cell 20C reaches on the ground (or over the sea, etc.) are the footprint 20F.

[0040] The SL antenna 111 may be a beamforming controllable array antenna capable of controlling the direction and width of each of a plurality of beams that form a plurality of cells (e.g., three cells or seven cells) in the target service area 20A. Adjacent beams in the cell formation target airspace may partially overlap each other.

[0041] The SL antenna 111 is, for example, a single or multiple array antennas in which multiple antenna elements are arranged two-dimensionally or three-dimensionally and capable of forming multiple beams toward the ground. The SL antenna 111 may also be a massive antenna in which many antenna elements are arranged two-dimensionally and capable of controlling beam directivity in the horizontal and vertical directions.

[0042] The relay communication station 110 can perform feeder link FL communication with a gateway device (also referred to as a "feeder station"; hereinafter referred to as a "GW station" or "terrestrial GW") 70, which is a wireless communication device for HAPS installed on land (or sea, etc.), via an FL antenna 112. The FL antenna 112 is, for example, an array antenna whose directivity (direction of a directional beam) can be controlled. The FL antenna 112 is, for example, a single or multiple array antennas in which multiple antenna elements are arranged two-dimensionally or three-dimensionally. The FL antenna 112 may also be a massive antenna in which many antenna elements are arranged two-dimensionally and whose directivity can be controlled in the horizontal and vertical directions.

[0043] The GW station 70 can perform feeder link FL communication with the relay communication station 110 via a feeder link antenna (hereinafter also referred to as "FL antenna") 71. The FL antenna 71 is, for example, an antenna whose directivity (direction of a directional beam) can be controlled. The FL antenna 71 is, for example, a single or multiple array antennas in which multiple antenna elements are arranged two-dimensionally or three-dimensionally. The FL antenna 71 may also be a massive antenna in which many antenna elements are arranged two-dimensionally and whose directivity can be controlled in the horizontal and vertical directions.

[0044] In Fig. 1, the feeder link FL(F) and the service link SL(F) are forward links (hereinafter also referred to as "downlinks") from the GW station 70 to the UE 60 via the HAPS 10. The feeder link FL(R) and the service link SL(R) are reverse links (hereinafter also referred to as "uplinks") from the UE 60 to the GW station 70 via the HAPS 10.

[0045] UE 60 is a terminal device used by a user on land or at sea. UE 60 is, for example, a mobile phone, a smartphone, a portable personal computer with a mobile communication function, or the like, and is also called a mobile terminal, a mobile station, a mobile device, or a portable communication terminal. UE 60 may be a modular mobile station incorporated into a moving object such as a vehicle such as an automobile, or a drone, which is an aircraft such as a small remotely controlled helicopter, or may be a terminal device for an IoT (Internet of Things) device.

[0046] UE 60 can communicate with base station device 80 connected to core network 85 of the mobile communication network by FDD method via relay communication station 110 and GW station 70. UE 60 can also access external communication network 90 such as the Internet via base station device 80 and core network 85 of the mobile communication network.

[0047] In the communication system of this embodiment, communication is performed between a base station device 80 and a UE (terminal device) 60 using an FDD (Frequency Division Duplex) method. Therefore, the duplex method for the downlink (forward link) and uplink (reverse link) of the service link between a relay communication station 110 and the UE 60 is the FDD (Frequency Division Duplex) method. The duplex method for the downlink (forward link) and uplink (reverse link) between the base station device 80 and a GW station 70 is also the FDD (Frequency Division Duplex) method. On the other hand, the duplex method for the downlink (forward link) and uplink (reverse link) between the relay communication station 110 and the GW station 70 is the TDD (Time Division Duplex) method.

[0048] The relay communication station 110 and the GW station 70 have a function of converting the duplexing method because they need to relay communications using different duplexing methods. For example, the relay communication station 110 has a means for converting between an FDD signal transmitted and received in the wireless section of the service link with the UE 60 and a TDD signal transmitted and received in the relay wireless section of the feeder link with the GW station 70. The GW station 70 also has a means for converting between an FDD signal transmitted and received with the base station device 80 and a TDD signal transmitted and received in the relay wireless section of the feeder link with the relay communication station 110. This allows the relay communication station 110 and the GW station 70 to transmit and receive radio signals in the TDD method in the relay wireless section of the feeder link.

[0049] The access method for wireless communication between the base station device 80 and the UE 60 via the relay communication station 110 and the GW station 70 is not limited to a specific method, and may be, for example, an FDMA (Frequency Division Multiple Access) method, a TDMA (Time Division Multiple Access) method, a CDMA (Code Division Multiple Access) method, or an OFDMA (Orthogonal Frequency Division Multiple Access) method.

[0050] Furthermore, the wireless communication of the service link between relay communication station 110 and UE 60 may use MIMO (Multi-Input and Multi-Output) technology, which has functions such as diversity coding, transmit beamforming, and spatial division multiplexing (SDM) and can increase transmission capacity per unit frequency by simultaneously using multiple antennas for both transmission and reception. Furthermore, the MIMO technology may be SU-MIMO (Single-User MIMO) technology, in which one base station transmits multiple signals to one UE at the same time and frequency, or MU-MIMO (Multi-User MIMO) technology, in which one base station transmits signals to multiple different UEs at the same time and frequency, or multiple different base stations transmit signals to one UE at the same time and frequency.

[0051] In the communication system configured as described above, for example, a signal from a base station device 80 is relayed by the GW station 70 and the relay communication station 110 of the HAPS 10, and communication services can be provided to UEs 60 on the ground. In particular, according to the communication system of this embodiment, the HAPS 10, which functions as an airborne platform, can provide ultra-wide area mobile communication services directly to UEs (terminal devices) 60 on the ground from the stratosphere at altitudes of 18 km or more and 50 km or less (particularly around 20 km). Furthermore, airborne platforms consisting of the HAPS 10 are attracting attention as a new form of communication suitable for use in large-scale disasters and the like.

[0052] The relay communication station (wireless relay device) 110 mounted on the aircraft 100 of HAPS10 is a non-regenerative type (hereinafter also referred to as a "repeater type") relay communication station that relays transmitted and received signals without regenerating them. Generally, wireless relay systems using the relay communication station 110 of HAPS10 include a repeater system and a base station system. In a repeater system, the relay communication station 110 mounted on the aircraft 100 of HAPS10 is a relay station that functions as a non-regenerative repeater, and directly relays communications between a base station device 80 and a UE 60 via a bent-pipe-shaped path via a GW station 70 and the relay communication station 110. In a base station system, the relay communication station 110 mounted on the aircraft 100 of HAPS10 has a base station device 80, and the base station device 80 of the relay communication station 110 is connected to a core network 85 of a mobile communication network via a backhaul line such as an FWA, and regenerates transmitted and received signals to perform wireless communications with the UE 60. In a base station system, the equipment configuration of the relay communication station becomes complicated, and multi-operator operation is difficult.

[0053] In the following embodiments, the wireless communication device according to the present invention will be mainly described as a non-regenerative (repeater type) relay communication station (wireless relay device) and gateway device that perform TDD wireless communication with each other in a feeder link of the repeater system, but the wireless communication device according to the present invention can also be applied to a base station type relay communication station (wireless relay device) and gateway device that perform TDD wireless communication with each other in a feeder link (backhaul line) of the FWA or the like of the base station system. Furthermore, the present invention can be applied not only to wireless relay devices such as relay communication stations and gateway devices, but also to wireless communication devices that perform TDD wireless communication and have a long transmission / reception distance.

[0054] The communication system of this embodiment uses a repeater system that uses a repeater-type relay communication station 110 for multi-operator operation, which has a simple device configuration. Furthermore, as described above, the repeater system of this embodiment uses the TDD method as the duplex method in the relay wireless section of the feeder link between the relay communication station 110 and the GW station 70. In the communication system of this embodiment, the frequency band of the TDD wireless signal in the feeder link and the frequency band of the FDD wireless signal in the service link are different frequency bands. For example, the frequency band of the TDD wireless signal in the relay wireless section of the feeder link is a millimeter-wave frequency between 20 GHz and 300 GHz. On the other hand, the uplink frequency band and the downlink frequency band of the FDD wireless signal in the service link SL are frequency bands of 10 GHz or less (for example, low band, mid band, or Sub6 band). Here, the low band is a frequency band of 3.5 GHz or less (for example, the 900 MHz band), and the mid band is a frequency band higher than 3.5 GHz and lower than 6 GHz (for example, the 3.7 GHz band or the 4.5 GHz band). The low band and mid band are collectively called the Sub6 band. The frequency band of the TDD-type radio signal of the feeder link FL is a millimeter-wave frequency band of 20 GHz or higher and 300 GHz or lower (for example, the 28 GHz band, the 31 GHz band, the 38 GHz band, or the 39 GHz band).

[0055] 2 is an explanatory diagram showing an example of communication bands in the FDD scheme in a base station device 80 and a UE (terminal device) 60 of the communication system according to the embodiment. In the FDD scheme, a communication band 912 (DL) of a downlink (forward link) and a communication band 912 (UL) of an uplink (reverse link) are set to different frequency bands.

[0056] 3 is an explanatory diagram showing an example of a communication band of the TDD method in a feeder link (relay wireless section) of a communication system according to an embodiment. In the TDD method of the feeder link, a communication band time 911 (UL) of the uplink (reverse link) and a communication band time 911 (DL) of the downlink (forward link) of the feeder link (relay wireless section) are repeatedly arranged at a predetermined period on the time axis. A guard time 931 of a predetermined time (for example, 1 / 24 millisecond) is provided between the uplink communication band time 911 (UL) and the downlink communication band time 911 (DL) to prevent interference with each other.

[0057] 4 is an explanatory diagram showing an example of a control known signal arranged in a guard time between a communication bandwidth time of a downlink (forward link) and an uplink (reverse link) in a TDD scheme of a feeder link (relay wireless section) in the communication system according to the embodiment. As shown in FIG. 4, a control known signal (e.g., a pilot signal or a reference signal) may be arranged in guard times 931(DL) and 931(UL) between a downlink communication bandwidth time 911(DL) and an uplink communication bandwidth time 911(UL). For example, a gateway device (GW station) 70 may transmit a known signal (DL) in the guard time 931(DL) preceding the downlink communication bandwidth time 911(DL), and a wireless relay device (relay communication station) 110 may control the gain of a receiving amplifier of the feeder link or a transmitting amplifier of the service link based on a reception result of the known signal (DL). For example, the wireless relay device (relay communication station) 110 may transmit a known signal (UL) in a guard time 931 (UL) preceding the uplink communication band time 911 (UL), and the gateway device (GW station) 70 may control the gain of the receiving amplifier of the feeder link based on the reception result of the known signal (UL).

[0058] 5 is an explanatory diagram showing an example of the overall configuration of a communication system having a multi-cell configuration corresponding to a plurality of base station devices 80(1) to 80(3) according to an embodiment. Note that in FIG. 5, components similar to those in FIG. 1 are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0059] 5, relay communication station 110 forms multiple cells 20C(1) to 20C(3) in target service area 20A via SL antenna 111. Multiple communication areas where multiple cells 20C(1) to 20C(3) reach on land (or sea, etc.) are footprints 20F(1) to 20F(3). Note that the illustrated example shows a case where three cells 20C(1) to 20C(3) are formed via SL antenna 111, but the number of cells 20C may be two, four or more.

[0060] The GW station 70 is connected to a plurality of base station devices 80(1) to 80(3) corresponding to a plurality of cells 20C(1) to 20C(3). The plurality of base station devices 80(1) to 80(3) are connected to a core network 85 of the mobile communication network of the telecommunications carrier. UEs 60 located in the ranges of the plurality of cells 20C(1) to 20C(3) can communicate with the base station devices 80(1) to 80(3) connected to the core network 85 of the mobile communication network by FDD via the relay communication station 110 and the GW station 70.

[0061] Fig. 6 is an explanatory diagram showing an example of time variations in the communication bands of the FDD downlink (forward link) and uplink (reverse link) in the plurality of base station devices 80(1) to 80(3) in the communication system of Fig. 5, and the communication bands of the FDD downlink and uplink in the feeder link (relay wireless section) and the service link in the FDD system. In the FDD system before cell multiplexing of Fig. 6, in each of the plurality of base station devices 80(1) to 80(3), the communication bands 912(1)(DL) to 912(3)(DL) that are the same frequency band in the downlink (forward link) and the communication bands 912(1)(UL) to 912(3)(UL) that are the same frequency band in the uplink (reverse link) are set to different frequency bands.

[0062] In the relay wireless section of the feeder link between the GW station (gateway device) 70 and the relay communication station (wireless relay device) 110, signals transmitted and received over the feeder link for each of the multiple base station devices 80(1) to 80(3) are combined using a TDD cell multiplexing method, and the downlink (forward link) and uplink (reverse link) between the relay communication station 110 and the GW station 70 are multiplexed. In the illustrated feeder link TDD method, a communication bandwidth time 911(UL) of the uplink (reverse link) of the feeder link (relay wireless section) and a communication bandwidth time 911(DL) of the downlink (forward link) are repeatedly arranged at a predetermined period on the time axis in the order of the base station devices 80(1), 80(2), and 80(3). A guard time of a predetermined time (e.g., 1 / 24 millisecond) is provided between the uplink communication bandwidth time 911(UL) and the downlink communication bandwidth time 911(DL) to prevent interference with each other.

[0063] In the service link between the relay communication station (wireless relay device) 110 and UE 60 residing in each of the plurality of cells 20C(1) to 20C(3), downlink (forward link) and uplink (reverse link) signals multiplexed by a TDD cell multiplexing method are separated, and the downlink (forward link) communication bands 913(1)(DL) to 913(3)(DL) and the uplink (reverse link) communication bands 913(1)(UL) to 913(3)(UL) are set to different frequency bands. Furthermore, since the beams directed from the relay communication station (wireless relay device) 110 to the multiple cells 20C(1) to 20C(3) are in different directions, the downlink (forward link) communication bands 913(1)(DL) to 913(3)(DL) of the same frequency band are multiplexed by spatial multiplexing, and the uplink (reverse link) communication bands 913(1)(UL) to 913(3)(UL) of the same frequency band are multiplexed.

[0064] 7 is an explanatory diagram showing an example of an AGC pilot signal and supervisory control data arranged in a guard time between a communication bandwidth time of a downlink (forward link) and a communication bandwidth time of an uplink (reverse link) in a TDD system of a feeder link (relay wireless section) in the communication system of FIG. 5. As shown in FIG. 7, a pilot signal for AGC control and supervisory control data may be arranged in the guard time between a downlink communication bandwidth time 911 (DL) and an uplink communication bandwidth time 911 (UL). For example, a wireless relay device (relay communication station) 110 may transmit an AGC control pilot signal Sp (UL) in the guard time preceding a first uplink communication bandwidth time 911 (UL), and transmit supervisory control data Dmc (UL) in the guard times preceding second and third uplink communication bandwidth times 911 (UL). A gateway device (GW station) 70 can control the gain of a receiving amplifier of the feeder link based on the reception results of the AGC control pilot signal Sp (UL) and supervisory control data Dmc (UL). Furthermore, for example, the gateway device (GW station) 70 may transmit an AGC control pilot signal Sp(DL) in a guard time preceding a first downlink communication band time 911(DL), and may transmit supervisory control data Dmc(DL) in guard times preceding the second and third downlink communication band times 911(DL). In this case, the wireless relay device (relay communication station) 110 can control the gain of the receiving amplifier of the feeder link or the transmitting amplifier of the service link based on the reception results of the AGC control pilot signal Sp(DL) and the supervisory control data Dmc(DL).

[0065] As shown in Fig. 7, AGC that is independent of the relay wireless system can be realized by transmitting and receiving an AGC pilot signal and supervisory control data in the guard time in the feeder link (relay wireless section) of the TDD system. Also, in the uplink (reverse link) from the wireless relay device (relay communication station) 110 to the gateway device (GW station) 70, the gain of the feeder link receiving amplifier in the gateway device (GW station) 70 can be controlled. Furthermore, because supervisory control data can be transmitted and received by utilizing the guard time between the communication band time 911 (DL) of the downlink (forward link) and the communication band time 911 (UL) of the uplink (reverse link), the number of external control lines can be reduced.

[0066] According to the embodiment shown in the above-mentioned FIGS. 1 to 7, by converting the relay wireless section (feeder link) of the feeder link between the wireless relay device (relay communication station) 110 and the gateway device (GW station) 70 to a TDD (Time Division Duplex) system and relaying it, it is possible to reduce the influence of phase noise in the relay wireless section while maintaining FDD system communication between the base station device 80 and the user equipment (UE) 60.

[0067] FIG. 8 is an explanatory diagram showing an example of the positional relationship between a gateway device (GW station) (hereinafter also referred to as a "terrestrial GW") 70 and the HAPS 10 in the communication system according to the embodiment. As shown in FIG. 8, as the altitude h of the HAPS 10 increases (for example, at an altitude of about 20 km), the distance (communication distance) d between the HAPS 10 and the terrestrial GW 70 increases, and the delay time of wireless signals transmitted and received between the HAPS 10 and the terrestrial GW 70 increases. Even when the distance (communication distance) d between the HAPS 10 and the terrestrial GW 70 increases in this way, in TDD-scheme feeder link communications using the same frequency band, a guard time TG is required that takes into account the delay time t of wireless signals, which increases with the distance (communication distance) d between the HAPS 10 and the terrestrial GW 70, to prevent interference between transmission and reception of forward link signals from the terrestrial GW 70 to the HAPS 10 and transmission and reception of reverse link signals from the HAPS 10 to the terrestrial GW 70.

[0068] Fig. 9 is an explanatory diagram showing an example of transmission and reception timing of a forward link (FWD) signal and a reverse link (REV) signal between a gateway device (terrestrial GW) 70 and HAPS 10 in a communication system according to a reference example. In Fig. 9, "T(FWD)" and "R(REV)" respectively represent the transmission period (transmission signal length) of the forward link signal and the reception period (reception signal length) of the reverse link signal in TDD communication by the terrestrial GW 70, and "T(REV)" and "R(FWD)" respectively represent the transmission period (transmission signal length) of the reverse link signal and the reception period (reception signal length) of the forward link signal in TDD communication by HAPS 10 (the same applies to the following Figs. 10 to 12, 14 to 20, 22, and 23).

[0069] As shown in the reference example of Figure 9, in general, to prevent interference between the transmission and reception of forward link signals and the transmission and reception of reverse link signals in TDD communications, a guard time TG equivalent to a round-trip delay time (t × 2), which is twice the one-way delay time t, is required between the transmission period T(FWD) of the forward link signal and the reception period R(REV) of the reverse link signal in the terrestrial gateway 70. Furthermore, a guard time TG equivalent to a round-trip delay time (t × 2), which is twice the communication delay time t, is required between the transmission period T(REV) of the reverse link signal and the reception period R(FWD) of the forward link signal in the HAPS 10. For example, if the altitude h of the HAPS 10 is approximately 20 km and the communication distance d between the HAPS 10 and the terrestrial gateway 70 is approximately 30 km, and the speed of light is c, the communication delay time t (= d / c) between the HAPS 10 and the terrestrial gateway 70 is approximately 0.1 ms, and a guard time TG equivalent to a round-trip delay time (0.2 ms), which is twice the communication delay time t, is required. However, if the set time of the guard time TG, which is set according to the distance (communication distance) d between the HAPS 10 and the terrestrial GW 70, becomes long, there is a risk that the speed of TDD feeder link communication will decrease.

[0070] In this embodiment, in TDD feeder link communication, the guard time TG is reduced by setting the time length of the transmission / reception period in which the transmission period of the forward link signal and the reception period of the reverse link signal in the terrestrial GW70 are consecutive and the time length of the transmission / reception period in which the transmission period of the reverse link signal and the reception period of the forward link signal in the HAPS10 are consecutive to a predetermined time length that takes into account the delay time t of the wireless signal, which changes depending on the distance (communication distance) d between HAPS10 and the terrestrial GW70.

[0071] Fig. 10 is an explanatory diagram showing an example of the transmission and reception timing of forward link signals and reverse link signals between a gateway device (terrestrial GW) 70 and HAPS 10 in the communication system of Fig. 8. In the example of Fig. 10, in TDD feeder link communication, the time length of the transmission and reception period in which the forward link signal transmission period T(FWD) and the reverse link signal reception period R(REV) continue in the terrestrial GW 70 is set to the same time length as the round-trip delay time (t × 2), which is twice the one-way delay time t. In addition, the time length of the transmission and reception period in which the forward link signal reception period R(FWD) and the reverse link signal transmission period T(REV) continue in the HAPS 10 is set to the same time length as the round-trip delay time (t × 2). For example, if the communication delay time t (= d / c) is 0.1 ms, the time length of the transmission and reception period (T(FWD) + R(REV)) at the terrestrial GW 70 and the time length of the transmission and reception period (R(FWD) + T(REV)) at HAPS 10 are set to 0.2 ms, which is the same time length as the round trip delay time (t × 2).

[0072] The terrestrial GW 70 repeats a transmission / reception period set to the same time length as the round trip delay time (t × 2) to periodically transmit a forward link signal to the wireless relay device (target device) 110 of HAPS 10 and receive a reverse link signal from the wireless relay device (target device) 110 of HAPS 10. Furthermore, the wireless relay device 110 of HAPS 10 repeats a transmission / reception period set to the same time length as the round trip delay time (t × 2) to periodically transmit a reverse link signal to the terrestrial GW (target device) 70 and receive a forward link signal from the terrestrial GW 70.

[0073] 10, the transmission period T(FWD) of the forward link signal is equal to the reception period R(REV) of the reverse link signal in TDD communication of the terrestrial GW 70, and the reception period R(FWD) of the forward link signal is equal to the transmission period T(REV) of the reverse link signal in TDD communication of the HAPS 10. That is, in the example of FIG. 10, the ratio of the time between transmission and reception in the transmission and reception period in the TDD communication is 5:5, and the ratio of the signal length of the forward link signal to the signal length of the reverse link signal in the transmission and reception period is 5:5.

[0074] In Fig. 10, the transmitting side of TDD communication starts radio wave transmission of a transmission signal of a predetermined length and then transmits the next radio wave when a round-trip delay time (t × 2) has elapsed. For example, the terrestrial gateway 70 starts radio wave transmission of a forward link signal and then transmits the next radio wave when a round-trip delay time (t × 2) has elapsed, i.e., when radio wave reception of the reverse link signal from the HAPS 10 is completed. Also, the radio repeater device 110 of the HAPS 10 starts radio wave transmission of a reverse link signal and then transmits the next radio wave when a round-trip delay time (t × 2) has elapsed, i.e., when radio wave reception of the forward link signal from the terrestrial gateway 70 is completed. By transmitting and receiving the forward link signal and the reverse link signal at the transmission and reception timings shown in Fig. 10, it is possible to maintain TDD feeder link communication in the same frequency band while reducing the guard time TG.

[0075] Fig. 11 is an explanatory diagram showing another example of the transmission and reception timing of forward link signals and reverse link signals between the gateway device (terrestrial GW) 70 and the HAPS 10 in the communication system of Fig. 8. Note that in Fig. 11, parts similar to those in Fig. 10 above are given the same reference numerals, and their description will be omitted.

[0076] The time ratio between the transmission period and the reception period in the above-mentioned transmission and reception period may be set to any ratio under the condition that the above-mentioned transmission and reception period has the same time length as the round-trip delay time (t × 2). For example, in the example of Fig. 11, the ratio between the transmission period T(FWD) and the reception period R(REV) in the transmission and reception period of the terrestrial GW 70 is set to 7:3, and the ratio between the reception period R(FWD) and the transmission period T(REV) in the transmission and reception period of the HAPS 10 is set to 7:3.

[0077] The ratio between the transmission period and the reception period in the transmission and reception period may be a fixed ratio, or may be changed to an arbitrary ratio. For example, as shown in FIG. 12, under the condition that the transmission and reception period has the same time length as the round-trip delay time (t × 2), the ratio (T:R) between the transmission period T(FWD) and the reception period R(REV) in the transmission and reception period of the terrestrial GW 70 may be changed from 5:5 to 7:3. Furthermore, in response to this change in the transmission and reception ratio in the terrestrial GW 70, under the condition that the transmission and reception period has the same time length as the round-trip delay time (t × 2), the ratio (R:T) between the reception period R(FWD) and the transmission period T(REV) in the transmission and reception period of the HAPS 10 may be changed from 5:5 to 7:3.

[0078] 13 is an explanatory diagram showing an example of the positional relationship between a gateway device (terrestrial GW) 70 and a HAPS 10 that moves, turns, rotates, etc. in the sky in a communication system according to an embodiment. As shown in FIG. 13, when the distance (communication distance) d1, d2 between the terrestrial GW 70 and the HAPS 10 changes due to the movement, turning, or rotation of the HAPS 10, which has a wireless relay device (relay communication station), the delay times t1 (= d1 / c) and t2 (= d2 / c) of wireless signals transmitted and received between the HAPS 10 and the terrestrial GW 70 change. For example, when the distance (communication distance) between the terrestrial GW 70 and the HAPS 10 changes from d1 (= 30 km) to d2 (= 45 km) due to the movement, turning, or rotation of the HAPS 10, the delay time changes from t1 (= 0.1 ms) to t2 (= 0.15 ms).

[0079] If the distance (communication distance) and delay time between the ground GW70 and HAPS10 fluctuate due to the movement, rotation, or turning of HAPS10, a guard time that can absorb the fluctuations in distance and delay time may be set, as shown below, or the transmission and reception period (transmission and reception signal period) may be adaptively changed to match the fluctuations in distance and delay time.

[0080] Figures 14 and 15 are explanatory diagrams showing examples of the transmission and reception timing of forward link signals and reverse link signals when the distance between the gateway device (terrestrial GW) 70 and the HAPS 10 in the communication system of Figure 13 is short (d1) and long (d2>d1), respectively. Note that in Figures 14 and 15, parts similar to those in Figure 10 above are given the same reference numerals, and their description will be omitted.

[0081] 14, when the distance between the terrestrial GW 70 and HAPS 10 is short (d1), in TDD feeder link communications, the time length of the transmission / reception period in which the transmission period T(FWD) of the forward link signal and the reception period R(REV) of the reverse link signal are consecutive in the terrestrial GW 70 is set to the same time length as the round-trip delay time (t1 × 2), which is twice the one-way delay time t1 at short distances. Also, the time length of the transmission / reception period in which the transmission period T(REV) of the reverse link signal and the reception period R(FWD) of the forward link signal are consecutive in HAPS 10 is set to the same time length as the round-trip delay time (t1 × 2). For example, if the communication delay time t1 (= d1 / c) is 0.1 ms, the time length of the transmission and reception period (T(FWD) + R(REV)) at the terrestrial GW70 and the time length of the transmission and reception period (T(REV) + R(FWD)) at HAPS10 are set to 0.2 ms, which is the same time length as the round-trip delay time (t1 × 2).

[0082] Furthermore, in the case of the short distance (d1) in FIG. 14 , a guard time TG having a time length equal to the difference (t2-t1) between the maximum delay time (t2) and the minimum delay time (t1) of the radio signal between the terrestrial gateway 70 and the HAPS 10, whose position fluctuates in the sky, is set before and after the transmission / reception period. For example, if the maximum delay time t2 is 0.15 ms and the minimum delay time t1 is 0.1 ms, the time length (t2-t1) of the guard time TG is 0.05 ms. When the distance between the terrestrial gateway 70 and the HAPS 10 is short (d1=30 km), the terrestrial gateway 70 sets a guard time TG having the above-mentioned predetermined time length (t2-t1=0.05 ms) before and after the transmission / reception period (T(FWD)+R(REV)), and the HAPS 10 sets a guard time TG having the above-mentioned predetermined time length (t2-t1) before and after the transmission / reception period (T(REV)+R(FWD)).

[0083] In the case of the short distance (d1) in Fig. 14, the terrestrial GW 70 periodically transmits a forward link signal to the wireless relay device (target device) 110 of HAPS 10 and receives a reverse link signal from the wireless relay device (target device) 110 of HAPS 10 by repeating a transmission / reception period set to the same time length as the round-trip delay time (t1 × 2) with a guard time TG having the above-mentioned predetermined time length (t2 - t1) illustrated in Fig. 14 set. Furthermore, the wireless relay device 110 of HAPS 10 periodically transmits a reverse link signal to the terrestrial GW (target device) 70 and receives a forward link signal from the terrestrial GW 70 by repeating a transmission / reception period set to the same time length as the round-trip delay time (t1 × 2) with a guard time TG having the above-mentioned predetermined time length (t2 - t1) illustrated in Fig. 14 set.

[0084] On the other hand, as shown in FIG. 15, when the distance between the terrestrial GW 70 and the HAPS 10 is long (d2), the time length of the transmission / reception period in which the reception period R(REV) of the reverse link signal and the transmission period T(FWD) of the forward link signal are consecutive at the terrestrial GW 70 is set to the same time length as the round-trip delay time (t1 × 2), which is twice the one-way delay time t1 at the short distance (d1). Furthermore, the time length of the transmission / reception period in which the reception period R(FWD) of the forward link signal and the transmission period T(REV) of the reverse link signal are consecutive at the HAPS 10 is set to the same time length as the round-trip delay time (t1 × 2). For example, when the communication delay time t1 (= d1 / c) is 0.1 ms, the time length of the transmission / reception period (R(REV) + T(FWD)) at the terrestrial GW 70 and the time length of the transmission / reception period (R(FWD) + T(REV)) at the HAPS 10 are set to 0.2 ms, which is the same time length as the round-trip delay time (t1 × 2).

[0085] 15, a guard time TG having a time length equal to the difference (t2-t1) between the maximum delay time (t2) and the minimum delay time (t1) of the wireless signal between the terrestrial GW 70 and HAPS 10 is set before and after the transmission and reception period. For example, when the distance between the terrestrial GW 70 and HAPS 10 is a long distance (d2=45 km), the terrestrial GW 70 sets a guard time TG having the predetermined time length (t2-t1=0.05 ms) before and after the transmission and reception period (R(REV)+T(FWD)), and HAPS 10 sets a guard time TG having the predetermined time length (t2-t1) before and after the transmission and reception period (R(FWD)+T(REV)).

[0086] In the case of the long distance (d2) in Fig. 15, the terrestrial GW 70 periodically transmits a forward link signal to the wireless relay device (target device) 110 of HAPS 10 and receives a reverse link signal from the wireless relay device (target device) 110 of HAPS 10 by repeating a transmission / reception period set to the same time length as the round-trip delay time (t1 × 2) with a guard time TG having the above-mentioned predetermined time length (t2 - t1) illustrated in Fig. 15 set. Furthermore, the wireless relay device 110 of HAPS 10 periodically transmits a reverse link signal to the terrestrial GW (target device) 70 and receives a forward link signal from the terrestrial GW 70 by repeating a transmission / reception period set to the same time length as the round-trip delay time (t1 × 2) with a guard time TG having the above-mentioned predetermined time length (t2 - t1) illustrated in Fig. 15 set.

[0087] 14 and 15, the transmitting side of TDD communications starts radio wave transmission of a transmission signal of a predetermined length and performs the next radio wave transmission when the total time of the guard time TG of the predetermined time length (t2-t1) and the round trip delay time (t1 x 2) has elapsed. For example, the terrestrial gateway 70 starts radio wave transmission of a forward link signal and performs radio wave transmission of the next forward link signal when the total time of the guard time TG (t2-t1) and the round trip delay time (t1 x 2) has elapsed, i.e., after radio wave reception of the reverse link signal from the HAPS 10 has been completed. Also, the radio relay device 110 of the HAPS 10 starts radio wave transmission of a reverse link signal and performs radio wave transmission of the next reverse link signal when the total time of the guard time TG (t2-t1) and the round trip delay time (t1 x 2) has elapsed, i.e., after radio wave reception of the forward link signal from the terrestrial gateway 70 has been completed. By transmitting and receiving the forward link signal and the reverse link signal at the transmission and reception timings shown in Figures 14 and 15, it is possible to maintain TDD feeder link communication in the same frequency band, and also to reduce the guard time TG by setting the guard time TG to the predetermined time length (t2-t1).

[0088] 14 and 15, even if the distance (communication distance) and delay time between the terrestrial GW70 and HAPS10 vary due to movement, turning, or rotation of HAPS10, the variations in distance and delay time can be absorbed, and interference between the transmission and reception of forward link signals from the terrestrial GW70 to HAPS10 and the transmission and reception of reverse link signals from HAPS10 to the terrestrial GW70 can be prevented in TDD feeder link communications using the same frequency band. In particular, the method of setting the guard time TG having the above-mentioned predetermined time length (t2-t1) as shown in Figures 14 and 15 is suitable when the flight pattern of HAPS10 is predetermined, such as the turning of an airplane, and there is little variation in the distance (communication distance) between the terrestrial GW70 and HAPS10.

[0089] 14 and 15, the ratio between the transmission period and the reception period in the transmission and reception period may be a fixed ratio, or may be changed to an arbitrary ratio. For example, as shown in FIG. 16, under the condition that the transmission and reception period has the same time length as the round-trip delay time (t1×2) at a short distance, the ratio (T:R) between the transmission period T(FWD) and the reception period R(REV) in the transmission and reception period of the terrestrial GW 70 in FIG. 14 may be changed from 5:5 to 7:3. Furthermore, in response to this change in the transmission and reception ratio in the terrestrial GW 70, the ratio (R:T) between the reception period R(FWD) and the transmission period T(REV) in the transmission and reception period of the HAPS 10 may be set from 5:5 to 7:3. In addition, the ratio (R:T) of the reception period R(REV) to the transmission period T(FWD) in the transmission and reception period of the terrestrial GW70 in Figure 15 may be changed from 5:5 to 7:3, and the ratio (R:T) of the transmission period T(REV) to the reception period R(FWD) in the transmission and reception period of the HAPS10 may be set from 5:5 to 7:3.

[0090] 14 and 15, the guard time TG (for example, time length) may be adjusted based on at least one of the distance (communication distance) d between the terrestrial GW70 and HAPS10 and the delay time t of the wireless signal between the terrestrial GW70 and HAPS10.

[0091] 17 and 18 are explanatory diagrams showing other examples of the transmission and reception timing of forward link signals and reverse link signals when the distance between the gateway device (terrestrial GW) 70 and HAPS 10 in the communication system of FIG. 13 is short (d1) and long (d2>d1), respectively. FIGS. 17 and 18 show examples of changing the transmission and reception period in accordance with changes in the round-trip delay time (t1×2, t2×2). FIG. 19 is an explanatory diagram showing an example of changing the time length of the transmission and reception period in accordance with the distance d between the gateway device (terrestrial GW) 70 and HAPS 10 in the communication system of FIG. 13. In FIGS. 17, 18, and 19, parts similar to those in FIG. 10 are designated by the same reference numerals, and their description will be omitted.

[0092] As shown in FIG. 17, when the distance between the terrestrial GW 70 and the HAPS 10 is short (d1), the time length of the transmission and reception period at the terrestrial GW 70 is set to the same time length as the round-trip delay time (t1 × 2) at the short distance (d1). Also, the time length of the transmission and reception period at the HAPS 10 is set to the same time length as the round-trip delay time (t1 × 2) at the short distance (d1). For example, as shown in FIG. 19, when the communication delay time t1 (= d1 / c) at the short distance (d1) is 0.1 ms, the time length of the transmission and reception period (T(FWD) + R(REV)) at the terrestrial GW 70 and the time length of the transmission and reception period (R(FWD) + T(REV)) at the HAPS 10 are each set to 0.2 ms, which is the same time length as the round-trip delay time (t1 × 2) at the short distance (d1).

[0093] When the distance between the terrestrial GW 70 and the HAPS 10 is short (d1), the terrestrial GW 70 repeats a transmission / reception period set to the same time length as the round-trip delay time (t1 × 2) to periodically transmit a forward link signal to the wireless relay device (target device) 110 of the HAPS 10 and receive a reverse link signal from the wireless relay device (target device) 110 of the HAPS 10. Furthermore, the wireless relay device 110 of the HAPS 10 repeats a transmission / reception period set to the same time length as the round-trip delay time (t1 × 2) to periodically transmit a reverse link signal to the terrestrial GW (target device) 70 and receive a forward link signal from the terrestrial GW 70.

[0094] In FIG. 17, the transmitting side of TDD communication starts radio wave transmission of a transmission signal of a predetermined length and performs the next radio wave transmission when the round-trip delay time (t1×2) at the short distance (d1) has elapsed. For example, the terrestrial gateway 70 starts radio wave transmission of a forward link signal and performs radio wave transmission of the next forward link signal when the round-trip delay time (t1×2) has elapsed, i.e., when radio wave reception of the reverse link signal from the HAPS 10 has been completed. Also, the radio repeater 110 of the HAPS 10 starts radio wave transmission of a reverse link signal and performs radio wave transmission of the next reverse link signal when the round-trip delay time (t1×2) at the short distance (d1) has elapsed, i.e., when radio wave reception of the forward link signal from the terrestrial gateway 70 has been completed. By transmitting and receiving the forward link signal and the reverse link signal at the transmission and reception timings shown in FIG. 17, it is possible to maintain TDD feeder link communication in the same frequency band over the short distance and reduce the guard time TG.

[0095] On the other hand, as shown in FIG. 18, when the distance between the terrestrial GW 70 and the HAPS 10 is a long distance (d2>d1), the time length of the transmission and reception period at the terrestrial GW 70 is set to the same time length as the round trip delay time (t2×2) at the long distance (d2). Also, the time length of the transmission and reception period at the HAPS 10 is set to the same time length as the round trip delay time (t2×2) at the long distance (d2). For example, as shown in FIG. 19, when the communication delay time t2 (=d2 / c) at the long distance (d2) is 0.15 ms, the time length of the transmission and reception period (T(FWD)+R(REV)) at the terrestrial GW 70 and the time length of the transmission and reception period (R(FWD)+T(REV)) at the HAPS 10 are each set to 0.3 ms, which is the same time length as the round trip delay time (t2×2) at the long distance (d2).

[0096] When the distance between the terrestrial GW 70 and the HAPS 10 is long (d2>d1), the terrestrial GW 70 repeats a transmission / reception period set to the same time length as the round-trip delay time (t2×2) to periodically transmit a forward link signal to the wireless relay device (target device) 110 of the HAPS 10 and receive a reverse link signal from the wireless relay device (target device) 110 of the HAPS 10. Furthermore, the wireless relay device 110 of the HAPS 10 repeats a transmission / reception period set to the same time length as the round-trip delay time (t2×2) to periodically transmit a reverse link signal to the terrestrial GW (target device) 70 and receive a forward link signal from the terrestrial GW 70.

[0097] In FIG. 18, the transmitting side of TDD communication starts radio wave transmission of a transmission signal of a predetermined length and performs the next radio wave transmission when the round-trip delay time (t2 × 2) at the long distance (d2) has elapsed. For example, the terrestrial gateway 70 starts radio wave transmission of a forward link signal and performs radio wave transmission of the next forward link signal when the round-trip delay time (t2 × 2) at the long distance (d2) has elapsed, i.e., when radio wave reception of the reverse link signal from the HAPS 10 is completed. Also, the radio repeater 110 of the HAPS 10 starts radio wave transmission of a reverse link signal and performs radio wave transmission of the next reverse link signal when the round-trip delay time (t2 × 2) at the long distance (d2) has elapsed, i.e., when radio wave reception of the forward link signal from the terrestrial gateway 70 is completed. By transmitting and receiving the forward link signal and the reverse link signal at the transmission and reception timings shown in FIG. 18, it is possible to maintain TDD feeder link communication in the same frequency band over the long distance and reduce the guard time TG.

[0098] In particular, by transmitting and receiving forward link signals and reverse link signals at the transmission and reception timings shown in Figures 17, 18, and 19, it is possible to prevent interference between transmission and reception of forward link signals from the terrestrial GW 70 to the HAPS 10 and transmission and reception of reverse link signals from the HAPS 10 to the terrestrial GW 70 in TDD feeder link communications using the same frequency band, even if the distance (communication distance) and delay time between the terrestrial GW 70 and the HAPS 10 vary due to movement, rotation, or turning of the HAPS 10. Moreover, in the examples of Figures 17 and 18, guard time TG is not required, and the guard time TG can be reduced.

[0099] 17 to 19, the ratio between the transmission period and the reception period in the transmission and reception period may be a fixed ratio, or may be changed to an arbitrary ratio. For example, as shown in FIG. 20, under the condition that the transmission and reception period has the same time length as the round-trip delay time (t1×2 to t2×2), the ratio (T:R) between the transmission period T(FWD) and the reception period R(REV) in the transmission and reception period of the terrestrial GW 70 may be changed from 5:5 to 7:3. Furthermore, in response to this change in the transmission and reception ratio in the terrestrial GW 70, the ratio (R:T) between the reception period R(FWD) and the transmission period T(REV) in the transmission and reception period of the HAPS 10 may be set from 5:5 to 7:3.

[0100] 17 to 19, the time length of the transmission and reception period may be adjusted based on at least one of the distance (communication distance) d between the terrestrial GW 70 and the HAPS 10 and the delay time t of the wireless signal between the terrestrial GW 70 and the HAPS 10.

[0101] 21 is a block diagram showing an example of the configuration of the main parts of a terrestrial feeder link device 700 provided in a gateway device (terrestrial GW) 70 and an overhead feeder link device 1100 provided in a radio relay device 110 of HAPS 10 in a communication system according to an embodiment. The terrestrial feeder link device 700 is a component in the terrestrial GW 70 that performs TDD feeder link communication with HAPS 10. The overhead feeder link device 1100 is a component in the radio relay device (relay communication station) 110 of HAPS 10 that performs TDD feeder link communication with the terrestrial GW 70.

[0102] In FIG. 21 , the terrestrial feeder link device 700 includes a transmission / reception signal processing unit 7001, a transmission / reception distance (delay time) acquisition / calculation unit 7004, a guard time / transmission / reception signal length calculation unit 7005, a GNSS (Global Navigation Satellite System) receiver or the like 7006, a transmission / reception switching timing signal generation unit 7007, a transmission signal timing adjustment unit 7008, a transmission / reception switching control unit 7009, and a transmission / reception switch 7010.

[0103] The transmission / reception signal processing unit 7001 includes a signal transmission unit 7002 that generates a transmission signal (forward link signal) of a predetermined frequency band based on an FDD transmission signal received from the base station device 80, and a signal reception unit 7003 that processes a TDD reception signal (reverse link signal) received via the FL antenna 71 used for both transmission and reception to generate an FDD reception signal of a predetermined frequency band.

[0104] The transmission / reception distance (delay time) acquisition / calculation unit 7004 acquires or calculates information on the distance d between the terrestrial GW70 (or the FL antenna 71 of the terrestrial GW70) and the HAPS10 (or the antenna 112), and calculates the delay time t of the radio waves transmitted and received between the terrestrial GW70 (or the FL antenna 71 of the terrestrial GW70) and the HAPS10 (or the antenna 112) based on the information on the distance d.

[0105] Based on the calculation result of the delay time t, the guard time / transmission signal length calculation unit 7005 calculates the transmission and reception signal length, i.e., the time length of the transmission and reception period (transmission period + reception period) for TDD communication in the terrestrial GW 70. Furthermore, the guard time / transmission signal length calculation unit 7005 calculates the individual time lengths of the transmission period and reception period in the transmission and reception period (signal length of the transmission signal and signal length of the reception signal), and the ratio between the transmission period and the reception period, as necessary. The guard time / transmission signal length calculation unit 7005 calculates the time length of the guard time TG to be set for TDD communication in the terrestrial GW 70 as necessary.

[0106] The GNSS receiver etc. 7006 outputs time information and a synchronization signal used for synchronization processing of TDD communication between the terrestrial GW 70 and the HAPS 10 based on a signal received from a GNSS satellite (for example, a GPS satellite).

[0107] The transmit / receive switching timing signal generator 7007 generates a transmit / receive switching timing signal for switching between transmission and reception in TDD communications at the terrestrial GW 70, based on information such as the time length of the transmit / receive period output from the guard time / transmit / receive signal length calculator 7005 and the time information and synchronization signal output from the GNSS receiver, etc. 7006. For example, the transmit / receive switching timing signal generator 7007 generates the transmit / receive switching timing signal shown in FIG. 22(a) when the transmit / receive signal length (the signal length of the transmit signal and the receive signal) is fixed or when the distance between the terrestrial GW 70 and the HAPS 10 is long. Furthermore, the transmit / receive switching timing signal generator 7007 generates the transmit / receive switching timing signal shown in FIG. 23(a) when the transmit / receive signal length (the signal length of the transmit signal and the receive signal) is variable or when the distance between the terrestrial GW 70 and the HAPS 10 is short.

[0108] The transmission signal timing adjustment unit 7008 adjusts the transmission timing of the transmission signal (forward link signal) output from the signal transmission unit 7002 based on the transmission / reception switching timing signal generated by the transmission / reception switching timing signal generation unit 7007 .

[0109] The transmit / receive switching control unit 7009 controls the transmit / receive switch 7010 to switch between transmission and reception in TDD communication at the terrestrial GW 70 based on the transmit / receive switching timing signal generated by the transmit / receive switching timing signal generation unit 7007.

[0110] The transmit / receive switch 7010 is connected to an FL antenna 71 for both transmission and reception, and switches between the transmission path of a TDD transmission signal (forward link signal) via the FL antenna 71 and the reception path of a TDD reception signal (reverse link signal) based on a control signal from the transmit / receive switching control unit 7009.

[0111] In the terrestrial feeder link device 700, the transmission / reception distance (delay time) acquisition / calculation unit 7004, the guard time / transmission / reception signal length calculation unit 7005, the GNSS receiver etc. 7006, and the transmission / reception switching timing signal generation unit 7007 also function as the following means A1 to A6. A1. A means for setting the time length of a transmission / reception period in which a transmission period for transmitting a signal to a HAPS (target device) 10 and a reception period for receiving a signal from the HAPS 10 in TDD wireless communication to be the same as the round-trip delay time of a wireless signal between a terrestrial GW 70 and the HAPS 10. A2. Means for changing the transmission / reception period in accordance with changes in the round-trip delay time A3. Means for changing the ratio of the transmission period and the reception period in the transmission and reception period A4. Means for adjusting the signal length of a transmission signal transmitted to HAPS 10 based on at least one of the distance d between the terrestrial GW 70 and HAPS 10 and the delay time t of a wireless signal between the terrestrial GW 70 and HAPS 10 A5. Means for setting a guard time TG having a time length that is the difference between the maximum delay time and the minimum delay time of the radio signal between the terrestrial GW 70 and the HAPS 10 before and after the transmission and reception period A6. Means for adjusting the guard time TG based on at least one of the distance d between the terrestrial gateway 70 and the HAPS 10 and the delay time of the radio signal between the terrestrial gateway 70 and the HAPS 10

[0112] In addition, in the ground feeder link device 700, the transmission / reception signal processing unit 7001, the transmission / reception switching timing signal generating unit 7007, the transmission signal timing adjusting unit 7008, the transmission / reception switching control unit 7009, and the transmission / reception switch 7010 also function as the following means A7. A7. Means for periodically transmitting to and receiving from HAPS 10 by repeating the transmission and reception period in TDD feeder link communication with HAPS 10

[0113] In FIG. 21, the aerial feeder link device 1100 includes a transmission / reception signal processing unit 1111, a transmission / reception distance (delay time) acquisition / calculation unit 1114, a guard time / transmission / reception signal length calculation unit 1115, a GNSS receiver etc. 1116, a transmission / reception switching timing signal generation unit 1117, a transmission signal timing adjustment unit 1118, a transmission / reception switching control unit 1119, and a transmission / reception switching switch 1120.

[0114] The transmission / reception signal processing unit 1111 has a signal transmission unit 1112 that generates a transmission signal (reverse link signal) of a predetermined frequency band based on an FDD transmission signal received from the terminal device 60, and a signal reception unit 1113 that processes a TDD reception signal (forward link signal) received via the transmission / reception antenna 112 to generate an FDD reception signal of a predetermined frequency band.

[0115] The transmission / reception distance (delay time) acquisition / calculation unit 1114 acquires or calculates information on the distance d between the terrestrial GW70 (or the FL antenna 71 of the terrestrial GW70) and the HAPS10 (or the antenna 112), and calculates the delay time t of the radio waves transmitted and received between the terrestrial GW70 (or the FL antenna 71 of the terrestrial GW70) and the HAPS10 (or the antenna 112) based on the information on the distance d.

[0116] Based on the calculation result of the delay time t, the guard time / transmission signal length calculation unit 1115 calculates the transmission and reception signal length, i.e., the time length of the transmission and reception period (transmission period + reception period) for FDD communications in HAPS 10. Furthermore, the guard time / transmission signal length calculation unit 1115 calculates the individual time lengths of the transmission period and reception period in the transmission and reception period (signal length of the transmission signal and signal length of the reception signal), and the ratio between the transmission period and the reception period, as necessary. The guard time / transmission signal length calculation unit 1115 calculates the time length of the guard time TG to be set for TDD communications in HAPS 10 as necessary.

[0117] The GNSS receiver etc. 1116 outputs time information and a synchronization signal used for synchronization processing of TDD communication between the terrestrial GW 70 and the HAPS 10 based on a signal received from a GNSS satellite (for example, a GPS satellite).

[0118] The transmit / receive switching timing signal generator 1117 generates a transmit / receive switching timing signal for switching between transmission and reception in TDD communications at HAPS 10, based on information such as the time length of the transmit / receive period output from the guard time / transmit / receive signal length calculator 1115 and the time information and synchronization signal output from the GNSS receiver, etc. 1116. For example, the transmit / receive switching timing signal generator 1117 generates the transmit / receive switching timing signal shown in FIG. 22(b) when the transmit / receive signal length (the signal length of the transmit signal and the receive signal) is fixed or when the distance between the terrestrial gateway 70 and HAPS 10 is long. Furthermore, the transmit / receive switching timing signal generator 1117 generates the transmit / receive switching timing signal shown in FIG. 23(b) when the transmit / receive signal length (the signal length of the transmit signal and the receive signal) is variable or when the distance between the terrestrial gateway 70 and HAPS 10 is short.

[0119] The transmission signal timing adjustment unit 1118 adjusts the transmission timing of the transmission signal (reverse link signal) output from the signal transmission unit 1112 based on the transmission / reception switching timing signal generated by the transmission / reception switching timing signal generation unit 1117 .

[0120] The transmit / receive switching control unit 1119 controls the transmit / receive switch 1120 to switch between transmission and reception in TDD communication in HAPS10 based on the transmit / receive switching timing signal generated by the transmit / receive switching timing signal generation unit 1117.

[0121] The transmit / receive switch 1120 is connected to the FL antenna 112, which is used for both transmission and reception, and switches between the transmission path of the TDD transmission signal (reverse link signal) via the FL antenna 112 and the reception path of the TDD reception signal (forward link signal) based on a control signal from the transmit / receive switching control unit 1119.

[0122] In the aerial feeder link device 1100, the transmission / reception distance (delay time) acquisition / calculation unit 1114, the guard time / transmission / reception signal length calculation unit 1115, the GNSS receiver etc. 1116, and the transmission / reception switching timing signal generation unit 1117 also function as the following means B1 to B6. B1. Means for setting the time length of a transmission / reception period in which a transmission period for transmitting a signal to a terrestrial GW (target device) 70 and a reception period for receiving a signal from the terrestrial GW 70 in TDD wireless communication are consecutive to the time length of the round-trip delay time of the wireless signal between the terrestrial GW 70 and the HAPS 10 B2. Means for changing the transmission / reception period in response to changes in the round-trip delay time B3. Means for changing the ratio of the transmission period to the reception period in the transmission / reception period B4. Means for adjusting the signal length of a transmission signal transmitted to the terrestrial GW 70 based on at least one of the distance d between the terrestrial GW 70 and the HAPS 10 and the delay time t of a wireless signal between the terrestrial GW 70 and the HAPS 10 B5. Means for setting a guard time TG having a time length that is the difference between the maximum delay time and the minimum delay time of the radio signal between the terrestrial GW 70 and the HAPS 10 before and after the transmission and reception period B6. Means for adjusting the guard time TG based on at least one of the distance d between the terrestrial gateway 70 and the HAPS 10 and the delay time of the radio signal between the terrestrial gateway 70 and the HAPS 10

[0123] In addition, in the overhead feeder link device 1100, the transmit / receive signal processing unit 1111, the transmit / receive switching timing signal generating unit 1117, the transmit signal timing adjusting unit 1118, the transmit / receive switching control unit 1119, and the transmit / receive switching switch 1120 also function as the following means B7. B7. Means for periodically transmitting to and receiving from the terrestrial GW 70 by repeating the transmission and reception period in TDD feeder link communication with the terrestrial GW 70

[0124] As described above, according to this embodiment, in wireless communication devices such as the wireless relay device (communication relay station) 110 and gateway device (terrestrial GW) 70 of HAPS 10 that relay communications with the base station device 80 and the terminal device 60, it is possible to maintain TDD feeder link communications in the same frequency band while reducing or shortening the guard time TG when performing TDD communications.

[0125] The present invention can maintain TDD feeder link communications in the same frequency band while reducing or minimizing guard time (TG) when conducting TDD communications, thereby contributing to the achievement of Goal 9 of the Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

[0126] It should be noted that the process steps and communication system components described herein may be implemented by various means. For example, these steps and components may be implemented in hardware, firmware, software, or a combination thereof.

[0127] With regard to hardware implementation, means such as processing units used to realize the above steps and components in an entity (e.g., various wireless communication devices, base stations, base station equipment, gateway equipment, wireless relay equipment, terminal equipment, various nodes of a network, hard disk drive equipment, or optical disk drive equipment) may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described in this specification, computers, or combinations thereof.

[0128] Furthermore, with regard to firmware and / or software implementations, the means, such as a processing unit, used to realize the above components may be implemented with a program (e.g., code, such as procedures, functions, modules, instructions, etc.) that performs the functions described herein. In general, any computer / processor-readable medium tangibly embodying firmware and / or software code may be used to implement the means, such as a processing unit, used to realize the above steps and components described herein. For example, the firmware and / or software code may be stored in a memory and executed by a computer or processor, such as in a controller. The memory may be implemented within the computer or processor or external to the processor. Furthermore, the firmware and / or software code may be stored in a computer- or processor-readable medium, such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), flash memory, floppy disk, compact disk (CD), digital versatile disk (DVD), magnetic or optical data storage device, etc. The code may be executed by one or more computers or processors and may cause the computers or processors to perform certain aspects of the functionality described herein.

[0129] The medium may be a non-transitory recording medium. The program code may be in any format as long as it can be read and executed by a computer, processor, or other device or machine. For example, the program code may be in any of source code, object code, and binary code, or may be a mixture of two or more of these codes.

[0130] Moreover, the description of the embodiments disclosed herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. [Explanation of symbols]

[0131] 10:HAPS 20A: Service area 20C: Cell 20F: Footprint 60: Terminal device 70: GW station (terrestrial GW, gateway equipment) 71:FL Antenna 80:Base station equipment 85: Core Network 100: Aircraft 110: Relay communication station (radio relay device) 111:SL Antenna 112:FL Antenna 700: Ground feeder link device 1100: Aerial feeder link device

Claims

1. A wireless communication device that performs wireless communication using a TDD (Time Division Duplex) method, a means for setting a time length of a transmission / reception period in which a transmission period for transmitting a signal to a target device and a reception period for receiving a signal from the target device are consecutive in the TDD wireless communication to the same time length as a round-trip delay time of a wireless signal between the wireless communication device and the target device; means for periodically transmitting to and receiving from the target device by repeating the transmission / reception period; A wireless communication device comprising:

2. 2. The wireless communication device of claim 1, means for changing the transmission and reception period in response to a change in the round trip delay time; A wireless communication device comprising:

3. 2. The wireless communication device of claim 1, a ratio of the transmission period to the reception period in the transmission and reception period is a fixed ratio; A wireless communication device comprising:

4. 2. The wireless communication device of claim 1, A wireless communication device comprising: means for changing a ratio of the transmission period to the reception period in the transmission / reception period.

5. 2. The wireless communication device of claim 1, A wireless communication device characterized by comprising a means for adjusting the signal length of a transmission signal to be transmitted to the target device based on at least one of the distance between the wireless communication device and the target device and the delay time of the wireless signal between the wireless communication device and the target device.

6. 2. The wireless communication device of claim 1, a means for setting a guard time having a time length equal to the difference between a maximum delay time and a minimum delay time of a wireless signal between the wireless communication device and the target device before and after the transmission / reception period; A wireless communication device comprising:

7. 7. The wireless communication device of claim 6, A wireless communication device characterized by comprising a means for adjusting the guard time based on at least one of the distance between the wireless communication device and the target device and the delay time of the wireless signal between the wireless communication device and the target device.

8. 2. The wireless communication device of claim 1, a transmission / reception switching timing signal generating unit that generates a transmission / reception switching timing signal that switches between transmission to the target device and reception from the target device so that a time length of a transmission period in which a transmission period for transmitting a signal to the target device and a reception period for receiving a signal from the target device in the TDD wireless communication is consecutive is set to the same time length as a round-trip delay time of the wireless signal between the wireless communication device and the target device; a transmission signal timing adjustment unit that adjusts a transmission timing for transmitting a transmission signal to the target device based on the transmission / reception switching timing signal so that transmission to and reception from the target device are periodically performed by repeating the transmission / reception period; A wireless communication device comprising:

9. 9. The wireless communication device according to claim 1, The wireless communication device A non-regenerative wireless relay device that relays FDD (Frequency Division Duplex) communications between a base station device and a terminal device, a means for converting between the FDD signal transmitted and received in a wireless section of a service link between the terminal device and the base station device and a TDD (Time Division Duplex) signal transmitted and received in a relay wireless section between the base station device and a gateway device connected to the base station device, transmitting and receiving radio signals in the relay radio section between the gateway device and the gateway device in the TDD system; A wireless communication device comprising:

10. 9. The wireless communication device according to claim 1, The wireless communication device a gateway device that is connected to a base station device and is capable of wireless communication with a non-regenerative wireless relay device that relays communication between the base station device and a terminal device using an FDD (Frequency Division Duplex) method; a means for converting between an FDD signal transmitted to and received from the base station device and a TDD (Time Division Duplex) signal transmitted to and received in a relay wireless section between the base station device and the wireless relay device; transmitting and receiving radio signals in the relay radio section between the radio relay device and the radio relay device in the TDD system; A wireless communication device comprising:

11. 1. A communication system comprising: A communication system comprising: a wireless relay device according to claim 9; and a gateway device according to claim 10.

12. 12. The communication system of claim 11, The non-regenerative radio relay device is an airborne relay type radio relay device that is installed on the body of an aircraft or floating body located in the sky, forms one or more cells toward a ground or sea service area via a service link antenna, and wirelessly communicates with one or more terminal devices located in the cell. A communication system comprising:

13. 9. The wireless communication device according to claim 1, The wireless communication device is characterized in that it has a base station device connected to a core network of a mobile communication network via a backhaul line of a relay wireless section between the base station device and a gateway device, and is a base station-type wireless relay device that transmits and receives wireless signals using the TDD method in the relay wireless section.

14. 9. The wireless communication device according to claim 1, The wireless communication device is characterized in that it is a gateway device connected to a core network of a mobile communication network and transmits and receives wireless signals using the TDD method in a backhaul line of a relay wireless section between a base station-type wireless communication device.

15. 1. A communication system comprising: A communication system comprising: a wireless communication device according to claim 13; and a gateway device according to claim 14.

16. 16. The communication system of claim 15, The base station type radio relay device is an airborne relay type radio relay device that is installed on the body of an aircraft or floating body located in the sky, forms one or more cells toward a ground or sea service area via a service link antenna, and wirelessly communicates with one or more terminal devices located in the cell. A communication system comprising:

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