Wireless relay system and wireless relay method

Abstract

A non-regenerative repeating wireless repeating system is provided that can realize a large capacity feeder link between a relay station master connected to a plurality of base stations and a relay station slave forming a plurality of cells. [Solution] A wireless relay system includes a relay station master and a relay station slave, and relays wireless communications between multiple base stations and terminal devices located in multiple cells corresponding to the multiple base stations via feeder links between the relay station master and the relay station slave. The relay station master transmits and receives multiple feeder link signals corresponding to the multiple cells to and from the relay station slave using MIMO spatial multiplexing. The relay station slave transmits and receives multiple feeder link signals corresponding to the multiple cells to and from the relay station master using MIMO spatial multiplexing.

Description

[Technical Field]

[0001] The present disclosure relates to non-regenerative wireless relaying. [Background technology]

[0002] Conventionally, there has been known a non-regenerative relay type wireless relay system that includes a relay station master unit provided in a gateway device on land or sea and a relay station slave unit provided in an aircraft or floating body in the sky, and that relays wireless communications between a base station and terminal devices of a plurality of cells via a feeder link between the relay station master unit and the relay station slave unit (see, for example, Patent Document 1). The relay station slave unit performs wireless communications over the feeder link with the relay station master unit and wireless communications over service links with terminal devices of a plurality of cells formed toward the ground. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-167539 Summary of the Invention

[0004] A wireless relay system according to one aspect of the present disclosure is a non-regenerative relay system that includes a relay station master and a relay station slave, and relays wireless communications between a plurality of base stations and terminal devices located in a plurality of cells corresponding to the plurality of base stations via feeder links between the relay station master and the relay station slave. The relay station master has means for transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station slave using MIMO (Multiple Input Multiple Output) spatial multiplexing, and the relay station slave has means for transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station master using MIMO spatial multiplexing.

[0005] In the wireless relay system, the relay station master may include a frequency converter configured to receive multiple downlink signals of the same frequency for the multiple cells from the multiple base stations and convert the frequencies of the multiple downlink signals to a feeder link frequency, and multiple feeder link antennas configured to transmit the multiple feeder link signals having the feeder link frequency to the relay station slave. The relay station slave may also include multiple feeder link antennas configured to receive the multiple feeder link signals transmitted from the relay station master, a signal separator configured to apply a MIMO spatial multiplexing transmission model to a wireless propagation path of a feeder link between the relay station master and the relay station slave and separate multiple service link signals for the multiple cells from multiple received signals received via the multiple feeder link antennas, a frequency converter configured to convert the frequencies of the multiple service link signals separated by the signal separator to a service link frequency, and multiple service link antennas configured to transmit the multiple service link signals having the service link frequency to the multiple cells, respectively.

[0006] In the wireless relay system, the frequency conversion unit of the relay station parent device may convert the frequencies of the plurality of downlink signals to the same feeder link frequency, and the plurality of feeder link antennas of the relay station parent device may transmit feeder link signals having the same feeder link frequency to the relay station child device.

[0007] In the wireless relay system, the plurality of cells may be divided into a plurality of mutually different cell groups, the frequency conversion unit of the relay station parent device may convert the frequencies of the plurality of downlink signals into a plurality of mutually different feeder link frequencies for each of the cell groups, and the plurality of feeder link antennas of the relay station parent device may transmit feeder link signals having the mutually different feeder link frequencies to the relay station child device.

[0008] In the wireless relay system, a propagation path between the multiple feeder link antennas of the relay station parent device and the multiple feeder link antennas of the relay station child device is a line-of-sight (LoS) environment, and the MIMO spatial multiplexing transmission model may be a LoS-MIMO spatial multiplexing transmission model.

[0009] In the wireless relay system, the multiple feeder link antennas of each of the relay station parent device and the relay station child device are single-polarized antennas or multi-polarized antennas, and at least one of the distance between the antennas and the polarization plane is different, and the MIMO spatial multiplexing transmission model may be a polarized MIMO spatial multiplexing transmission model.

[0010] A wireless relay method according to another aspect of the present disclosure is a non-regenerative relay method for relaying wireless communications between a plurality of base stations and terminal devices located in a plurality of cells corresponding to the plurality of base stations via a feeder link between a relay station master and a relay station slave. This wireless relay method may include the relay station master transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station slave by MIMO (Multiple Input Multiple Output) spatial multiplexing, and the relay station slave transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station master by MIMO spatial multiplexing.

[0011] The wireless relay method may include the relay station master receiving a plurality of downlink signals of the same frequency for the plurality of cells from the plurality of base stations and converting the frequencies of the plurality of downlink signals to a feeder link frequency; the relay station master transmitting a plurality of feeder link signals having the feeder link frequency to the relay station slave via a plurality of feeder link antennas, respectively; the relay station slave receiving the plurality of feeder link signals transmitted from the relay station master via a plurality of feeder link antennas; the relay station slave applying a MIMO spatial multiplexing transmission model to a wireless propagation path of the feeder link between the relay master and the relay station slave, and separating a plurality of service link signals for the plurality of cells from a plurality of received signals received via the plurality of feeder link antennas; the relay station slave converting the frequencies of the plurality of service link signals to the service link frequency; and the relay station slave transmitting a plurality of service link signals having the service link frequency to the plurality of cells via a plurality of service link antennas, respectively.

[0012] In the wireless relay system and the wireless relay method, the relay station master unit may be provided in a gateway device on land or sea, and the relay station slave unit may be provided in an aircraft or floating body in the sky. The aircraft or floating body may be a HAPS ("High Altitude Pseudolite" or "High Altitude Platform Station"), an artificial satellite (e.g., an artificial satellite in low Earth orbit (LEO), an artificial satellite in medium Earth orbit (MEO), or a communication satellite in geostationary orbit), a balloon, a drone, or an unmanned aerial vehicle (UAV) such as an unmanned aircraft system (UAS).

[0013] In the wireless relay system and the wireless relay method, the relay station master unit and the relay station slave unit may be installed on land or on the sea.

[0014] The programs executed in the relay station parent device and the relay station child device may include a trained model used in machine learning, a trained model newly created by machine learning, or a trained model updated by machine learning. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating an example of the overall configuration of a non-regenerative relay multi-cell wireless relay system according to an embodiment of the present disclosure. [Figure 2] Fig. 2(a) is an explanatory diagram showing an example of a non-regenerative repeating method according to the embodiment, and Fig. 2(b) is an explanatory diagram showing an example of a regenerative repeating method according to a reference example. [Figure 3] FIG. 3 is a diagram illustrating an example of MIMO spatial multiplexing transmission. [Figure 4] FIG. 4 is an explanatory diagram showing an example of a non-regenerative repeating method according to a reference example. [Figure 5] FIG. 5 is an explanatory diagram showing an example of a regenerative relay method using MIMO spatial multiplexing transmission according to a reference example. [Figure 6] FIG. 6 is an explanatory diagram showing an example of a multi-cell wireless relay system according to a reference example that does not use MIMO spatial multiplexing transmission. [Figure 7] FIG. 7 is an explanatory diagram illustrating an example of a multi-cell wireless relay system using MIMO spatial multiplexing transmission according to the embodiment. [Figure 8] FIG. 8 is a block diagram showing an example of a configuration of a main part of a relay station master device in the multi-cell wireless relay system according to the reference example of FIG. [Figure 9] FIG. 9 is a block diagram showing an example of a configuration of a main part of a relay station slave device in the multi-cell wireless relay system according to the reference example of FIG. [Figure 10] Fig. 10(a) is an explanatory diagram showing an example of frequency conversion in a first frequency conversion unit of the relay station slave device of Fig. 9. Fig. 10(b) is an explanatory diagram showing an example of frequency conversion in a second frequency conversion unit of the relay station slave device of Fig. 9. [Figure 11]FIG. 11 is a block diagram showing an example of a configuration of a main part of a relay station master device in the multi-cell wireless relay system according to the embodiment of FIG. [Figure 12] FIG. 12 is a block diagram showing an example of a configuration of a main part of a relay station slave device in the multi-cell wireless relay system according to the embodiment of FIG. [Figure 13] FIG. 13 is an explanatory diagram showing an example of normal MIMO communication between a plurality of antennas of a relay station master device and a plurality of antennas of a relay station slave device in a propagation path in a multipath-rich environment (multiple wave environment). [Figure 14] FIG. 14 is an explanatory diagram showing an example of LoS-MIMO communication between a plurality of antennas of a relay station master device and a plurality of antennas of a relay station slave device in a line-of-sight (LoS) environment. [Figure 15] FIG. 15 is an explanatory diagram showing an example of antenna installation conditions in LoS-MIMO communication. [Figure 16] FIG. 16 is an explanatory diagram showing an example of a multi-cell wireless relay system using frequency division multiplexing transmission according to a reference example. [Figure 17] FIG. 17 is an explanatory diagram illustrating an example of a multi-cell wireless relay system that uses both frequency division multiplexing and LoS-MIMO spatial multiplexing transmission according to the embodiment. [Figure 18] FIG. 18 is an explanatory diagram showing an example of the configuration of the main parts of the multi-cell wireless relay system of FIG. [Figure 19] FIG. 19 is a block diagram showing an example of a configuration of a main part of a relay station master device in the multi-cell wireless relay system according to the embodiment of FIG. [Figure 20] FIG. 20 is a block diagram showing an example of a configuration of a main part of a relay station slave device in the multi-cell wireless relay system according to the embodiment of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each drawing merely schematically illustrates shapes, sizes, positional relationships, corresponding relationships, configurations, processing, steps, procedures, etc., to the extent that the contents of the present disclosure can be understood, and therefore the present disclosure is not limited to only the shapes, sizes, positional relationships, corresponding relationships, configurations, processing, steps, and procedures exemplified in each drawing. Furthermore, the numerical values ​​exemplified in the present disclosure are merely preferred examples, and therefore the present disclosure is not limited to the exemplified numerical values.

[0017] A wireless relay system according to an embodiment of the present disclosure is a multi-cell wireless relay system (hereinafter also referred to as a "multi-cell non-regenerative wireless relay system," "non-regenerative wireless relay system," or "wireless relay system") employing a non-regenerative relaying scheme that can be applied to both airborne systems such as HAPS and drones and terrestrial systems. In particular, the multi-cell wireless relay system of this embodiment can reduce the power consumption and weight of an airborne system equipped with a HAPS. Furthermore, in a non-regenerative wireless relay system where it is difficult to achieve high capacity using MIMO spatial multiplexing, it is possible to achieve high capacity feeder links between relay station masters and relay station slaves, assuming multi-cell wireless relaying. The wireless relay system according to this embodiment is suitable for realizing three-dimensional networks in mobile communications conforming to the Long Term Evolution (LTE)-Advanced standard and next-generation standards such as the fifth generation (5GNR) that supports simultaneous connection to multiple terminal devices and low latency.

[0018] [Non-regenerative multi-cell wireless relay system] 1 is a diagram illustrating an example of the overall configuration of a non-regenerative relay multi-cell wireless relay system (hereinafter also referred to as "wireless relay system") 10 according to an embodiment of the present disclosure. The wireless relay system 10 is a non-regenerative relay wireless relay system that includes a relay station master 21 provided in a terrestrial or marine gateway device 20 and a relay station slave 31 provided in an aircraft or floating body in the sky, and relays wireless communications between a base station 40 having one or more base station devices 41 and terminal devices 50 located in a plurality of cells 100C(1) to 100C(6) via a feeder link FL between the relay station master 21 and the relay station slave 31.

[0019] In the wireless relay system of this embodiment, the air vehicle or floating body on which the relay station slave unit 31 is mounted is, for example, a high-altitude platform station ("high-altitude pseudosatellite" or "stratospheric platform") (hereinafter also referred to as "HAPS" or "airborne platform (HAPS)") 30, which functions as an airborne radio relay device. The HAPS 30 is located in an airspace at a predetermined altitude and forms a three-dimensional cell (also referred to as a "HAPS cell") as a wide-area cell consisting of multiple cells 100C(1) to 100C(6). The HAPS 30 is an air vehicle or floating body (e.g., a solar plane, airship, drone, or balloon) 300 that is controlled by autonomous control or external control to float or fly and position in an airspace (floating airspace) at a predetermined altitude above the ground or sea surface, and on which the relay station slave unit 31 is mounted. Note that the HAPS 30 that can function as an airborne communication relay device may also be a relay communication station mounted on an artificial satellite such as a low Earth orbit (LEO) satellite or a geostationary orbit (GEO) satellite.

[0020] Furthermore, the communication system via the HAPS 30 of this embodiment (hereinafter also referred to as the "HAPS communication system") may include, in addition to the wireless relay system 10, one or more terminal devices 50 with which the HAPS 30 communicates, a gateway device (hereinafter also referred to as the "GW station," "gateway station," or "feeder station") 20, or a base station 40. In the HAPS communication system, a system having the HAPS 30 and other devices located in the sky is an airborne system, and a system having the GW station 20 and other devices located on the ground (or sea) is a terrestrial system.

[0021] The airspace in which HAPS 30 is located is, for example, stratospheric airspace at an altitude of 11 km or more and 50 km or less above the ground (or above water such as the sea or lake). 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.

[0022] HAPS30 flies at a lower altitude than typical artificial satellites but higher than terrestrial or offshore base stations, ensuring high visibility while minimizing propagation loss compared to satellite communications. This feature makes it possible for HAPS30 to provide communication services to terminal devices (mobile stations) 50, which are user devices such as terrestrial or offshore cellular mobile terminals. By providing communication services from HAPS30, a small number of HAPS30 can simultaneously cover a wide area that was previously covered by multiple terrestrial or offshore base stations, offering the advantage of providing stable communication services at low cost.

[0023] The relay station slave device 31 of the HAPS 30 forms multiple beams toward the ground (or sea surface) using a service link antenna (hereinafter referred to as an "SL antenna") 33 for wireless communication with a user terminal device (hereinafter referred to as "UE" (user device)) 50, thereby forming multiple cells (also referred to as "HAPS cells") 100C(1) to 100C(6) that can wirelessly communicate with the UE 50. The overall radius of the service area (also referred to as the "HAPS service area") 100A consisting of the footprints of these cells on the ground (or sea) is, for example, several tens of kilometers to 100 kilometers.

[0024] In this embodiment, the relay station slave device 31 of the HAPS 30 forms six cells 100C(1) to 100C(6), but the number of cells formed by the relay station slave device 31 may be two, three, four, five, seven, or eight or more cells.

[0025] UE 50 is a terminal device used by a user on land or at sea. UE 50 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 50 may be a modular mobile station incorporated in a moving object such as a vehicle such as an automobile, or a drone, which is a small remotely controlled aircraft such as a helicopter, or may be a terminal device for an IoT (Internet of Things) device. UE 50 may also be a user device used by a user in an aircraft such as an airplane.

[0026] The UE 50 can communicate with a base station device 41 of a base station 40 connected to a core network device 60 of a mobile communication network using the FDD method, the TDD method, or both methods via the relay station slave device 31 and the GW station 20 of the HAPS 30. The UE 50 can also access an external communication network 70 such as the Internet via the base station device 41 and the core network device 60 of the mobile communication network.

[0027] The relay station slave device 31 of the HAPS 30 is, for example, a repeater slave device that wirelessly communicates with a relay station master device (repeat master device) 21 mounted on a gateway device (also called a "gateway station" or "feeder station", hereinafter referred to as a "GW station") 20 connected to a terrestrial (or marine) base station 40. The relay station slave device 31 is connected to a core network device 60 of a mobile communication network via the GW station 20 and the base station 40, which are installed on land or sea and are capable of wireless communication via a feeder link antenna (hereinafter referred to as an "FL antenna") 32.

[0028] The communication of the feeder link FL between the relay station slave 31 of the HAPS 30 and the relay station master 21 of the GW station 20 may be carried out by wireless communication using radio waves such as microwaves, millimeter waves, and submillimeter waves, or by optical communication using laser light or the like.

[0029] The GW station 20 may control its own antenna (hereinafter referred to as "GW antenna") 22 to track the HAPS 30 moving in the air. By having the GW antenna 22 track the HAPS 30, it is possible to suppress degradation of communication quality of the feeder link FL due to movement of the HAPS 30, even when a GW antenna 22 with high directivity such as a parabolic antenna is used.

[0030] The base station 40 includes a plurality of base station devices (e.g., eNodeB, gNodeB) 41 corresponding to a plurality of 100C(1) to 100C(6). In the case of an LTE eNodeB, for example, each of the plurality of base station devices 41 is configured with a remote radio unit (RRH (Remote Radio Head), also called an RRU (Remote Radio Unit)) and a baseband processing unit (BBU (Base Band Unit)). The RRH and BBU may be connected to each other by an optical fiber line and may be located separately from each other. Alternatively, the plurality of BBUs may be aggregated and located in one place.

[0031] Each of the RRHs of the multiple base station devices 41 includes, for example, a quadrature modulation / demodulation unit, a transmission unit, a reception unit, a power amplifier (PA (Power Amplifier)), and a low noise receiver (LNA (Low Noise Amplifier)), and is connected to the GW station 20. The quadrature modulation / demodulation unit performs quadrature modulation / demodulation on the OFDM signal processed by the BBU and converts it into an analog signal (RF signal). The transmission unit converts the frequency of the RF signal generated by the quadrature modulation / demodulation unit into a frequency to be transmitted as radio waves. The reception unit converts the frequency of the high frequency signal of the received radio waves into a frequency to be processed by the quadrature modulation / demodulation unit. The power amplifier (PA) power-amplifies the RF signal generated by the transmission unit. The low noise receiver (LNA) amplifies the received weak radio waves and passes them to the reception unit.

[0032] Each of the BBUs of the multiple base station devices 41 includes, for example, a base station control unit, a transmission path interface unit, a timing control unit, and a baseband unit, and is connected to a core network of a mobile communication network via a predetermined interface (for example, an S1 interface). The base station control unit controls the entire base station and performs call control protocols and control monitoring. The transmission path interface unit is connected to a packet transmission path such as Ethernet (registered trademark) between the base station and the core network, and processes a predetermined protocol to exchange IP packets. The timing control unit generates various clocks used within the base station based on a reference clock extracted from a signal received via the packet transmission path or a GNSS (Global Navigation Satellite System) signal received from an artificial satellite. The baseband unit converts (modulates and demodulates) IP packets exchanged via the transmission path interface unit into OFDM signals (baseband signals), which are radio signals.

[0033] Each HAPS 30 may autonomously control the levitation and movement (flight) of the HAPS main body 300 and the processing in the relay station slave unit 31 by executing a control program with a control unit configured with an internally incorporated computer or the like. For example, each HAPS 30 may acquire current location information of the HAPS itself (e.g., GPS location information), pre-stored location control information (e.g., flight schedule information), location information of other HAPS 30 located in the vicinity, and autonomously control the levitation and movement (flight) and the processing in the relay station slave unit 31 based on this information.

[0034] Furthermore, the levitation (flight) of each HAPS 30 and the processing of the relay station slave unit 31 may be controlled by a management device (also referred to as a "remote control device" or "central control server") provided in a communication center or the like connected to the core network of the mobile communication network. The management device may be configured, for example, as a computer device such as a PC, a server, or the like. In this case, the HAPS 30 includes a control communication unit (e.g., a mobile communication module) for receiving control information from the management device and transmitting various information such as monitoring information to a predetermined destination such as the management device. The control communication unit may be assigned terminal identification information (e.g., an IP address, a telephone number, etc.) to enable communication with the management device. The MAC address of the communication interface may be used to identify the control communication unit of the HAPS 30.

[0035] Transmission and reception of control information and monitoring information between HAPS 30 and the management device can be performed, for example, via an LTE communication line passing through a core network device 60 of the mobile communication network, a base station 40, and a GW station 20. Transmission and reception of control information and monitoring information may also be performed using a mobile communication satellite line via an artificial satellite, or using a satellite line via the Internet and an artificial satellite.

[0036] The monitoring information transmitted from the HAPS 30 may include at least one of the following: information about the flight (flight) of the HAPS itself or surrounding HAPSs, information about processing by the relay station slave unit 31, monitoring information including a reception level measured by the HAPS 30 of the received power of the feeder link between the HAPS 30 and the GW station 20, and information about the status of the HAPS 30 and observation data acquired by various sensors. The monitoring information may also include at least one of the following: current position and attitude information of the HAPS 30, flight path information (flight schedule information, flight route history information), airspeed, ground speed and thrust direction, wind speed and direction of air currents around the HAPS 30, and air pressure and temperature around the HAPS 30. The control information may include flight information such as target flight route information of the HAPS 30.

[0037] The HAPS 30 and the management device may acquire weather forecast information for an area including the radio propagation path of the feeder link, maintenance schedule information for the GW station 20 or the base station 40, reception level monitor information for the feeder link with the GW station 20 measured by the HAPS 30, flight path information for the HAPS 30, and current location information and attitude information for the HAPS 30. This information may be acquired, for example, from a server in a core network (mobile communication network) that manages each piece of information or from a server on the Internet. Furthermore, the management device may acquire the maintenance schedule information for the GW station 20 or the base station 40 from the GW station 20 or the base station 40 via a core network device 60 of the mobile communication network using a predetermined interface (for example, an S1 interface of LTE), or may acquire it from a server that manages the GW station 20 or the base station 40.

[0038] The duplexing method for the uplink and downlink of the wireless communication of the service link SL between the relay station slave device 31 and the terminal device 50 is not limited to a specific method, and may be, for example, a time division duplex (TDD) method or a frequency division duplex (FDD) method. The access method for the wireless communication of the service link SL between the relay station slave device 31 and the terminal device 50 is not limited to a specific method, and may be, for example, a frequency division multiple access (FDMA) method, a time division multiple access (TDMA) method, a code division multiple access (CDMA) method, or an orthogonal frequency division multiple access (OFDMA) method. The wireless communication may also use a multi-input and multi-output (MIMO) technology that has functions such as diversity coding, transmission beamforming, and spatial division multiplexing (SDM) and can increase the transmission capacity per unit frequency by simultaneously using multiple antennas for both transmission and reception. Furthermore, the MIMO technology may be SU-MIMO (Single-User MIMO) technology in which one base station transmits multiple signals to one terminal device at the same time and frequency, or MU-MIMO (Multi-User MIMO) technology in which one base station transmits signals to multiple different terminal devices at the same time and frequency.

[0039] In the following embodiment, the HAPS 30 having the relay station slave unit 31 that wirelessly communicates with the terminal device 50 is illustrated and described as a solar plane type HAPS, but the HAPS 30 may also be an unmanned airship type HAPS. The following embodiment can also be applied to a floating communication relay device made up of an air vehicle or floating body other than a HAPS.

[0040] Furthermore, the link between the HAPS 30 and the base station 40 via the GW station 20 is called a "feeder link" FL, and the link between the HAPS 30 and the terminal device 50 is called a "service link" SL. In particular, the section between the HAPS 30 and the GW station 20 is called a "feeder link wireless section." Furthermore, the downlink of communication from the GW station 20 to the terminal device 50 via the HAPS 30 is also called a "forward link," and the uplink of communication from the terminal device 50 to the GW station 20 via the HAPS 30 is also called a "reverse link."

[0041] The relay station slave unit 31 mounted on the main body (airframe) 300 of the HAPS 30 is a non-regenerative type (hereinafter also referred to as "repeater type") relay communication station that relays transmitted and received signals without regenerating them. Generally, there are two types of feeder link wireless relay methods: a non-regenerative relay method that wirelessly relays wireless signals without demodulating them, and a regenerative relay method that demodulates and wirelessly relays wireless signals.

[0042] 2(a), a relay station 301 mounted on the main body (aircraft) 300 of HAPS 30 functions as a non-regenerative repeater, and directly relays communications between a base station device 41 connected to a core network device 60 and UE 50 via a bent-pipe-shaped path via GW station 20 and relay station 301. In the non-regenerative repeater system, the base station device 41 that acts as the relay source can be installed on the ground, so the relay station 301 device (wireless relay device) mounted on HAPS 30 can be lightweight and simple.

[0043] 2(b), a base station system using the regenerative repeating method includes a relay station 302 mounted on the main body (aircraft) 300 of the HAPS 30, which has a base station device 41. The base station device 41 of the relay station 302 is connected to a core network device 60 of the mobile communications network via a backhaul line such as FWA, regenerates transmitted and received signals, and performs wireless communication with the UE 50. The regenerative repeating method requires the HAPS 30 to be equipped with a modem device for modulation and demodulation, and to install all of the base station devices 41 for the multiple cells that make up the service link. This means that the wireless device mounted on the HAPS 30 is heavy and complex. However, because the transmitted signal is IP data, data compression can improve frequency utilization efficiency.

[0044] [MIMO spatial multiplexing wireless relay] 1, the HAPS communication system including the wireless relay system 10 of this embodiment covers a vast area 100A compared to a typical terrestrial base station installed on land (or sea). The communication links of the HAPS communication system are composed of a service link SL that connects the HAPS 30 and terminal devices 50, and a feeder link (hereinafter also referred to as the "HAPS feeder link") FL that connects the HAPS 30 and the GW station 20 of the terrestrial system. The feeder link FL of the HAPS communication system requires a large-capacity line to transmit and receive all traffic from all user terminal devices 50 located in the vast coverage area 100A.

[0045] Spatial multiplexing using MIMO (Multiple Input Multiple Output) (hereinafter referred to as "MIMO spatial multiplexing") is one method of increasing the capacity of the HAPS feeder link in the airborne system shown in Figure 1. However, it is difficult to apply MIMO spatial multiplexing to a non-regenerative radio relay system that can reduce the power consumption and weight of the HAPS 30 in the airborne system.

[0046] Figure 3 is a diagram showing an example of MIMO spatial multiplexing transmission. In Figure 3, the MIMO system is composed of multiple transmitting antennas 22(1) and 22(2) and multiple receiving antennas 32(1) and 32(2). In MIMO spatial multiplexing transmission, multiple data streams, each containing different data, are simultaneously transmitted from the multiple transmitting antennas 22(1) and 22(2) over radio spatial channels CH(1) and CH(2) of the same frequency, and the data streams are separated and processed on the receiving side by utilizing the independence (orthogonality) of the radio spatial channels CH(1) and CH(2).

[0047] 4, relay station parent device 21 wirelessly relays the radio signal (fs) received from base station device 41 to relay station slave device 31 as is without demodulating it into data, and therefore cannot allocate data to multiple transmitting antennas 22. Therefore, it is not possible to divide the data stream demodulated by relay station parent device 21 at the source into individual paths formed by MIMO spatial multiplexing and transmit them in parallel to relay station slave device 31 (simultaneous transmission of different data streams for each transmitting antenna), as in the regenerative repeating method of FIG.

[0048] In this embodiment, in a non-regenerative wireless relay system where it is difficult to achieve a large capacity using MIMO spatial multiplexing, an increase in the capacity of the feeder link is realized on the premise of multi-cell wireless relay.

[0049] Fig. 6 is an explanatory diagram showing an example of a multi-cell wireless relay system that does not use MIMO spatial multiplexing transmission according to a reference example. Fig. 7 is an explanatory diagram showing an example of a multi-cell wireless relay system that uses MIMO spatial multiplexing transmission according to an embodiment. In Fig. 6 and Fig. 7, parts that are common to Fig. 1 above are given the same reference numerals and descriptions thereof will be omitted.

[0050] In the service link SL of the HAPS communication system, a multi-cell configuration having multiple cells is assumed in order to increase capacity. In the conventional non-regenerative wireless system according to the reference example of FIG. 6, for example, the relay station master device 21 receives the frequency f of multiple cells 100C(1) to 100C(4) from multiple base station devices 41(1) to 41(4). sThe signal is frequency converted to multiple frequencies f f#1 , f f#2 , f f#3 , f f#4 The signals are wirelessly relayed to the relay station slave unit 31 of the HAPS 30 in the sky as a plurality of feeder link signals each having the above-mentioned characteristics.

[0051] On the other hand, in the non-regenerative relay system according to the present embodiment of Fig. 7, the relay station master device 21 has a means for transmitting and receiving a plurality of feeder link signals corresponding to a plurality of cells 100C(1) to 100C(4) with the relay station slave device 31 by MIMO spatial multiplexing, and the relay station slave device 31 has a means for transmitting and receiving a plurality of feeder link signals corresponding to a plurality of cells 100C(1) to 100C(4) with the relay station master device 21 by MIMO spatial multiplexing. For example, the relay station master device 21 receives the frequency f s signal on the same feeder link frequency f f and transmits the frequency-converted feeder link signals from multiple transmitting antennas 22(1) to 22(4), which are different for each cell. The relay station slave device 31 performs spatial separation processing on the signals (feeder link signals) of multiple cells received by the multiple receiving antennas 32(1) to 32(4) based on a MIMO spatial multiplexing model. In this way, MIMO spatial multiplexing transmission is performed between the multiple transmitting antennas 22(1) to 22(4) of the relay station master device 21 and the multiple receiving antennas 32(1) to 32(4) of the relay station slave device 31 via multiple channels CH(1) to CH(4), which are independent of each other, thereby relaying the multi-cell radio signals non-regeneratively. The non-regenerative relaying method according to this embodiment makes it possible to reduce the frequency bandwidth by the number of antennas compared to the conventional non-regenerative relaying method according to the above-mentioned reference example, and therefore enables an increase in line capacity when the same frequency bandwidth is used.

[0052] The spatial separation processing of the received signal at the relay station slave device 31 can be performed, for example, by estimating a propagation path response H of the feeder link FL based on the reception result of a known signal such as a reference signal received from the relay station master device 21, and applying any signal separation algorithm (for example, a method using a receiving weight based on a zero-forcing (ZF) standard, a method using a receiving weight based on a minimum mean square error (MMSE) standard, a serial canceller (SIC) method, a maximum likelihood detection (MLD) method, etc.) based on the propagation path response H. Here, the estimation and updating of the propagation path response H may be performed periodically, for example, or when the position of the HAPS 30 having the relay station slave device 31 changes due to movement or rotation.

[0053] Furthermore, the MIMO spatial multiplexing transmission model used for spatial separation processing of the received signal at the relay station slave device 31 may be a LoS-MIMO spatial multiplexing transmission model that assumes that there is a line-of-sight (LoS) propagation path between the multiple feeder link antennas 22 of the relay station master device 21 and the multiple feeder link antennas 32 of the relay station slave device 31. Furthermore, the MIMO spatial multiplexing transmission model may be a polarized MIMO spatial multiplexing transmission model that assumes that the multiple feeder link antennas 22, 32 of the relay station master device 21 and the relay station slave device 31 are single-polarized or multi-polarized antennas, and that at least one of the distance between the antennas and the polarization plane is different.

[0054] FIG. 8 is a block diagram showing an example of the configuration of the main parts of the relay station master device 21 in the multi-cell wireless relay system according to the reference example of FIG. 6. FIG. 9 is a block diagram showing an example of the configuration of the main parts of the relay station slave device 31 in the multi-cell wireless relay system according to the reference example of FIG. 6. In FIG. 8 and FIG. 9, the subscript s1 of the frequency notation f is a symbol indicating the frequency band (the same frequency band in this example) of the service link transmitted from the plurality of base station (BS) devices 41(1) to 41(4) to the terminal device 50. The subscripts b1 to b4 are symbols indicating the baseband frequencies corresponding to the respective cells. The subscripts (b1) to (b4) are symbols indicating that the baseband frequencies of b1 to b4 are symmetrical or central, respectively. The subscripts f1 to f4 are symbols indicating the feeder link frequencies corresponding to the respective cells. The subscripts #1 to #4 are symbols for identifying the signals of the respective cells. In addition, the notation "f" indicating frequency conversion is (b3) →f (b1)#1~4 " indicates that the baseband signal of the frequency band #3 is converted to the same frequency b1 as shown in FIG. 10(a). (b1)#1~4 →f (b1)#3 " indicates that the baseband signal in the frequency band #3 is filtered as shown in FIG. 10(b). The subscripts of the frequency notation f described above also apply to the embodiments in FIGS. 11, 12, 19, and 20 described below.

[0055] 8, the relay station master device 21 of the relay source includes a plurality of first frequency converters 210(1) to 210(4), a signal synthesis unit 220, a signal processing unit 230 having a digital filter and the like, a second frequency converter 240, a transmission amplifier unit 250, and a transmission filter unit 260.

[0056] The plurality of first frequency converters 210(1) to 210(4) convert the same frequency (f s1#1~4 ) downlink signals and multiple adjacent frequencies (f b1#1 ,f b2#2 ,f b3#3 ,f b4#4) baseband signal. b1#1 ,f b2#2 ,f b3#3 ,f b4#4 ) baseband signals are synthesized in the signal synthesis unit 220, filtered in the signal processing unit 230, and then converted to a predetermined feeder link frequency (f f1#1 ,f f2#2 ,f f3#3 ,f f4#4 ) is converted to the feeder link frequency (f f1#1 ,f f2#2 ,f f3#3 ,f f4#4 The feeder link signal including the signal addressed to each cell having the .DELTA..DELTA..DELTA.) is made to a predetermined power by the transmission amplifier unit 250, filtered by the transmission filter unit 260, and then transmitted from the GW antenna 22 to the relay station slave unit 31.

[0057] 9, the relay station slave device 31 of the relay destination includes a receiving filter unit 310, a receiving LNA (low noise amplifier) ​​unit 320, a first frequency conversion unit 330, a signal branching unit 340, a plurality of second frequency conversion units 350(1) to 350(4), a signal processing unit 360, a plurality of third frequency conversion units 370(1) to 370(4), a plurality of transmitting amplifier units 380(1) to 380(4), and a plurality of transmitting filter units 390(1) to 390(4).

[0058] The feeder link signal (f f1#1 ~f f4#4 ) is filtered by the receiving filter unit 310, amplified by the receiving LNA unit 320, and then converted to a baseband frequency (f b1#1 ~f b4#4 ), which are then branched into a plurality of baseband signals by the signal branching unit 340. The plurality of baseband signals are then converted into signals in the same frequency band (f (b1)#1~4 ), which is filtered by a plurality of digital filters 361(1) to 361(4) of the signal processing unit 360, and then converted into a service link frequency band (fs1#1~4 ) is converted into the service link frequency band (f s1#1~4 The plurality of downlink signals in the service link frequency band (f) are respectively set to a predetermined power by the plurality of transmission amplifier units 380(1) to 380(4), filtered by the transmission filter units 390(1) to 390(4), and then transmitted from the plurality of SL antennas 33(1) to 33(4) to the respective cells 100C(1) to 100C(4). The terminal devices 50(1) to 50(4) of the respective cells receive the service link frequency band (f) transmitted from the relay station slave device 31. s1#1~4 ) via a plurality of antennas 51(1) to 51(4).

[0059] Fig. 11 is a block diagram showing an example of the configuration of the main parts of the relay station master device 21 in the multi-cell wireless relay system 10 according to the embodiment of Fig. 7. Fig. 12 is a block diagram showing an example of the configuration of the main parts of the relay station slave device 31 in the multi-cell wireless relay system according to the embodiment of Fig. 7. Note that, although the examples of Figs. 11 and 12 describe a case of four cells, a similar configuration can be extended and applied to cases of two cells, three cells, five cells, and six or more cells.

[0060] In FIG. 11, relay station master device 21, which is the relay source, includes a signal processing unit 230 having a plurality of first frequency conversion units 210(1) to 210(4) and a plurality of digital filters 231(1) to 231(4), a plurality of second frequency conversion units 240(1) to 240(4), a plurality of transmission amplifier units 250(1) to 250(4), and a plurality of transmission filter units 260(1) to 260(4).

[0061] The plurality of first frequency converters 210(1) to 210(4) convert the same frequency (f s1#1~4 ) downlink signal and receive the same frequency (f b1#1 ,f b1#2 ,f b1#3 ,f b1#4 ) baseband signal. b1#1 ,f b1#2 ,f b1#3 ,f b1#4) baseband signal is filtered by the signal processing unit 230 and then converted to the same feeder link frequency (f f1#1 ,f f1#2 ,f f1#3 ,f f1#4 ) is converted to the same feeder link frequency (f f1#1 ,f f1#2 ,f f1#3 ,f f1#4 ) are respectively adjusted to a predetermined power by a plurality of transmission amplifier units 250(1) to 250(4), filtered by a plurality of transmission filter units 260(1) to 260(4), and then transmitted from a plurality of GW antennas 22(1) to 22(4) to the relay station slave unit 31 via the feeder link wireless propagation path 80.

[0062] 12, the relay station slave device 31 of the relay destination includes a plurality of receiving filter units 310(1) to 310(4), a plurality of receiving LNA (low noise amplifier) ​​units 320(1) to 320(4), a plurality of first frequency conversion units 330(1) to 330(4), a signal processing unit 360 having a plurality of digital filters 361(1) to 361(4) and a signal separation unit 362, a plurality of second frequency conversion units 370(1) to 370(4), a plurality of transmitting amplifier units 380(1) to 380(4), and a plurality of transmitting filter units 390(1) to 390(4).

[0063] The plurality of FL antennas 32(1) to 32(4) respectively receive the plurality of feeder link signals (f f1#1 ~f f4#4 ) are mixed together (hereinafter referred to as "mixed signals"). The mixed signals (f f1#1~#4 ) is filtered by the multiple receiving filters 310(1) to 310(4), amplified by the receiving LNAs 320(1) to 320(4), and then converted to a baseband frequency (f b1#1~#4 ) is converted to the baseband frequency (fb1#1~#4 ) are filtered by a plurality of digital filters 361(1) to 361(4) in the signal processing unit 360, and then are separated into a plurality of baseband frequencies (f b1#1~ f b1#4 ) are separated into a plurality of baseband signals each having a baseband frequency (f b1#1~ f b1#4 ) are converted into a service link frequency band (f s1#1~4 ) is converted into the service link frequency band (f s1#1~4 The plurality of downlink signals in the service link frequency band (f) are respectively set to a predetermined power by the plurality of transmission amplifier units 380(1) to 380(4), filtered by the transmission filter units 390(1) to 390(4), and then transmitted from the plurality of SL antennas 33(1) to 33(4) to the respective cells 100C(1) to 100C(4). The terminal devices 50(1) to 50(4) of the respective cells receive the service link frequency band (f) transmitted from the relay station slave device 31. s1#1~4 ) via a plurality of antennas 51(1) to 51(4).

[0064] 11 and 12, the multi-cell unregenerative wireless relay system 10 that performs wireless relay using MIMO spatial multiplexing can realize an increase in the capacity of the feeder link FL between the relay station master 21 connected to multiple base station devices 41(1) to 41(4) and the relay station slave 31 that forms multiple cells 100C(1) to 100C(4). Also, compared to the conventional unregenerative relay system, it is possible to reduce the frequency bandwidth by the number of antennas, and it is possible to increase the line capacity when using the same frequency bandwidth.

[0065] 11 and 12, propagation channel information of the feeder link between the relay station master device 21 and the relay station slave device 31 (e.g., information on a matrix of a propagation path response of the feeder link) may be fed back from the relay station slave device 31 to the relay station master device 21, and the signal processing unit 230 of the relay station master device 21 may control the transmission weight for MIMO spatial multiplexing (e.g., calculate the transmission weight and apply it to the transmission signal) using the propagation channel information fed back from the relay station slave device 31. As the communication line for feedback, for example, a control line separately established between the relay station master device 21 and the relay station slave device 31 may be used, or a separately established inter-relay station cooperation network may be used, or a part of the communication line of the reverse link of the feeder link from the relay station slave device 31 to the relay station master device 21 may be used.

[0066] [Use of LoS-MIMO] Fig. 13 is an explanatory diagram showing an example of normal MIMO communication between multiple antennas 22(1) to 22(3) of relay station master 21 and multiple antennas 32(1) to 32(3) of relay station slave 31 in a propagation path 81 in a multipath-rich environment (multiple wave environment). Fig. 14 is an explanatory diagram showing an example of LoS-MIMO communication between multiple antennas 22(1) to 22(3) of relay station master 21 and multiple antennas 32(1) to 32(3) of relay station slave 31 in a propagation path 82 in a line-of-sight (LoS) environment. The normal MIMO communication in Fig. 13 is effective in a propagation path 81 in a propagation environment where there is low correlation between antennas and where there is a lot of reflection and diffraction and the propagation environment is multipath-rich and out of line-of-sight. In this case, variations occur in the eigenvalues ​​of each channel (iid Rayleigh channel) CH(1) to CH(3) formed by MIMO so as to have an independent Rayleigh distribution, and therefore, when signals from each cell 100C(1) to 100C(3) are assigned to each channel CH(1) to CH(3), variations in quality occur between the cells.

[0067] On the other hand, in the case of polarization MIMO or line-of-sight (LoS) environment propagation path 82 of Fig. 14, in LoS-MIMO communication that appropriately considers the antenna spacing (dt,dr) and distance (D) as shown in Fig. 15 and the following equation (1), the eigenvalues ​​of each channel CH(1) to CH(3) can be made approximately the same magnitude. Therefore, by assigning the signal of each cell to each of these channels CH(1) to CH(3), multi-cell wireless relay with little variation in quality between cells is possible in MIMO spatial multiplexing.

[0068]

number

[0069] [Combined configuration of frequency division multiplexing and MIMO spatial multiplexing] In another embodiment of the present disclosure, a number of groups in which multiple cells constituting a multi-cell are frequency-multiplexed are formed as many as the number of transmitting antennas, and the groups are transmitted from each transmitting antenna. The signals of the multiple cells received by the receiving antennas are subjected to spatial separation processing and frequency division processing, and the multi-cell radio signals are LoS spatially multiplexed and wirelessly relayed. For example, the multiple cells are each divided into multiple different cell groups. The frequency conversion unit of the relay station master device 21 converts the frequency f of the multiple downlink signals into a single frequency group. s is set to multiple feeder link frequencies f f The plurality of feeder link antennas 22 of the relay station master unit 21 are converted into the mutually different feeder link frequencies f f The feeder link signal having the above-mentioned signal is transmitted to the repeater station slave unit 31.

[0070] Fig. 16 is an explanatory diagram showing an example of a multi-cell wireless relay system using frequency multiplexing transmission according to a reference example. Fig. 17 is an explanatory diagram showing an example of a multi-cell wireless relay system using both frequency multiplexing and LoS-MIMO spatial multiplexing transmission according to an embodiment. In Fig. 16 and Fig. 17, parts common to Fig. 1, Fig. 6 and Fig. 7 above are assigned the same reference numerals and description thereof will be omitted.

[0071] In the multi-cell wireless relay system of FIG. 16, the relay station master device 21 receives the frequency f of the plurality of cells 100C(1) to 100C(6) from the plurality of base station devices 41(1) to 41(6). s The signal is frequency converted to multiple frequencies f f#1 , f f#2 , f f#3 , f f#4 , f f#5 , f f#6 are simultaneously transmitted from the GW antenna 22 via a propagation path 82 in the LoS environment to the relay station slave unit 31 of the HAPS 30 in the sky, and are relayed wirelessly.

[0072] On the other hand, in the multi-cell wireless relay system of FIG. 17, the relay station master device 21 receives the frequencies f of the plurality of cells 100C(1) to 100C(6) received from the plurality of base station devices 41(1) to 41(6). s Among the signals, the frequency f s The signal is frequency converted to multiple frequencies f f#1 , f f#2 , f f#3 are simultaneously transmitted from the first GW antenna 22(1) via a propagation path 82 in the LoS environment to the relay station slave unit 31 of the HAPS 30 in the sky, and are relayed wirelessly.

[0073] Furthermore, the relay station master device 21 selects the frequency f of the plurality of cells 100C(4) to 100C(6) belonging to the second cell group. s The signal is frequency converted to multiple frequencies f f#4 , f f#5 , f f#6 are wirelessly relayed from the second GW antenna 22(2) to the relay station slave unit 31 of the HAPS 30 in the sky via a propagation path 82 in the LoS environment.

[0074] Fig. 18 is an explanatory diagram showing an example of the configuration of the main parts of the multi-cell wireless relay system 10 of Fig. 17. In Fig. 18, a first frequency multiplexing unit 23(1) of the relay station master device 21 multiplexes a plurality of frequencies f output from a plurality of base station devices (gNBs) 41(1) to 41(6). s Among the downlink signals of the cells 100C(1) to 100C(3) belonging to the first cell group, s The signal is frequency converted to multiple frequencies f f#1 , f f#2 , f f#3 are simultaneously transmitted from the first GW antenna 22(1) via a feeder link propagation path 82 in an LoS environment to a plurality of FL antennas 32(1), 32(2) of the relay station slave unit 31 of the HAPS 30 in the sky.

[0075] In FIG. 18, the second frequency multiplexing unit 23(2) of the relay station master device 21 multiplexes the frequency f s The signal is frequency converted to multiple frequencies f f#4 , f f#5 , f f#6 are simultaneously transmitted from the second GW antenna 22(2) via the feeder link propagation path 82 in the LoS environment to the multiple FL antennas 32(1), 32(2) of the relay station slave unit 31 of the HAPS 30 in the sky.

[0076] 18, the spatial separation processing unit 34 of the relay station slave device 31 separates a plurality of frequencies f corresponding to a plurality of cells 100C(1) to 100C(3) belonging to the first cell group from the mixed signals received by the plurality of FL antennas 32(1) and 32(2). f#1 , f f#2 , f f#3 a first feeder link signal group having a plurality of feeder link signals of the frequency f corresponding to a plurality of cells 100C(4) to 100C(6) belonging to a second cell group; f#4 , f f#5 , f f#6The first frequency dividing unit 35(1) divides the first feeder link signal group output from the spatial separation processing unit 34 into a plurality of frequency f f#1 , f f#2 , f f#3 The second frequency division unit 35(2) divides the second feeder link signal group output from the spatial separation processing unit 34 into a plurality of frequency f f#4 , f f#5 , f f#6 The frequency f of the plurality of feeder link signals output from the first frequency dividing unit 35(1) and the second frequency dividing unit 35(2) is divided into a plurality of feeder link signals each having a frequency f f#1 , f f#2 , f f#3 , f f#4 , f f#5 , f f#6 are converted to the frequency fs of the service link and transmitted as downlink signals from the service link antenna 33 to the user equipment (UE) 50.

[0077] Fig. 19 is a block diagram showing an example of a configuration of a main part of the relay station master device 21 in the multi-cell wireless relay system 10 according to the embodiment of Fig. 17. Fig. 20 is a block diagram showing an example of a configuration of a main part of the relay station slave device 31 in the multi-cell wireless relay system 10 according to the embodiment of Fig. 17. Note that, although the examples of Figs. 19 and 20 describe a case of six cells, a similar configuration can be extended and applied to cases of four cells, five cells, and seven or more cells. Furthermore, the number of cell groups may be three or more, and the number of cells belonging to each cell group may be two or four or more.

[0078] 19, relay station master device 21, which is the relay source, includes a signal processing unit 230 having a plurality of first frequency conversion units 210(1) to 210(6), a plurality of signal synthesis units 270(1), 270(2), a plurality of digital filters 232(1), 232(2), a plurality of second frequency conversion units 241(1), 241(2), a plurality of transmission amplifier units 251(1), 251(2), and a plurality of transmission filter units 261(1), 261(2).

[0079] The plurality of first frequency converters 210(1) to 210(6) convert the same frequency (f s1#1~6 ) downlink signal and receive the same frequency (f b1#1 ,f b1#2 ,f b1#3 ,f b1#4 ,f b1#5 ,f b1#6 ) baseband signal for the plurality of cells 100(1) to 100(3) of the first cell group. s1#1~3 ) are multiple downlink signals arranged in a predetermined band on the frequency axis. b1#1 ,f b2#2 ,f b3#3 ) baseband signal. In addition, the same frequency (f s1#1~3 ) are multiple downlink signals of multiple frequencies (f b1#4 ,f b2#5 ,f b3#6 ) is converted into a baseband signal.

[0080] Multiple frequencies (f b1#1 ,f b2#2 ,f b3#3 ) baseband signals are synthesized by the signal synthesis unit 270(1), filtered by the digital filter 232(1) of the signal processing unit 230, and then converted into a feeder link frequency (f f1#1 ,f f2#2 ,f f3#3 ) corresponding to the first cell group. f1#1 ,f f2#2 ,f f3#3 ) are each adjusted to a predetermined power by the transmission amplifier unit 251(1), filtered by the transmission filter unit 261(1), and then transmitted from the GW antenna 22(1) to the relay station slave unit 31 via the wireless propagation path 80 of the feeder link.

[0081] Multiple frequencies (f b1#4 ,f b2#5 ,f b3#6 ) baseband signals are combined by the signal combiner 270(2), filtered by the digital filter 232(2) of the signal processor 230, and then converted by the second frequency converter 241(2) to the feeder link frequency (f f1#4 ,f f2#5 ,f f3#6 ) corresponding to the second cell group. f1#4 ,f f2#5 ,f f3#6 ) are each adjusted to a predetermined power by the transmission amplifier unit 251(2), filtered by the transmission filter unit 261(2), and then transmitted from the GW antenna 22(2) to the relay station slave unit 31 via the wireless propagation path 80 of the feeder link.

[0082] In FIG. 20, the relay station slave device 31 of the relay destination includes a plurality of receiving filter units 311(1) and 311(2), a plurality of receiving LNA (low noise amplifier) ​​units 321(1) and 321(2), a plurality of first frequency conversion units 331(1) and 331(2), a signal processing unit 360, a plurality of third frequency conversion units 370(1) to 370(6), a plurality of transmitting amplifier units 380(1) to 380(6), and a plurality of transmitting filter units 390(1) to 390(6).

[0083] The plurality of FL antennas 32(1), 32(2) respectively receive the plurality of feeder link signals (f f1#1 ~f f3#3 , f f1#4 ~f f3#6 ) are mixed together (hereinafter referred to as "mixed signals"). The mixed signals (f f1#1 ~f f3#3 , f f1#4 ~f f3#6) is filtered by a plurality of receiving filters 311(1) and 311(2), amplified by receiving LNA units 321(1) and 321(2), and then converted to a baseband frequency (f b1#1 ~f b3#3 , f b1#4 ~f b3#6 )

[0084] The signal processing unit 360 has a plurality of digital filters 363(1) and 363(2) on the input side, a signal separating unit 364, a plurality of signal branching units 365(1) and 365(2), a plurality of second frequency conversion units 366(1) to 366(6), and a plurality of digital filters 367(1) to 367(6) on the output side. b1#1 ~f b3#3 , f b1#4 ~f b3#6 ) are filtered by a plurality of digital filters 363(1), 363(2) of the signal processing unit 360, and then are separated into a plurality of baseband frequencies (f b1#1 ~f b3#3 ) and a plurality of baseband signals having a second group of baseband frequencies (f b1#4 ~f b3#6 ) into a plurality of baseband signals of the first cell group, each of which has a baseband signal (f b1#1 ~f b3#3 ) and a plurality of baseband signals (f b1#4 ~f b3#6 ) are branched by a plurality of signal branching units 365(1) and 365(2), and converted into the same frequency f by a plurality of second frequency conversion units 366(1) to 366(6). (b1) After being converted into a baseband signal, the signal is filtered by a plurality of digital filters 367(1) to 367(6).

[0085] A plurality of individual baseband signals (f b1#1 ~f b1#3 , fb1#4 ~f b1#6 ) are converted into a service link frequency band (f s1#1 ~f s1#3 , f s1#4 ~f s1#6 ) is converted into the service link frequency band (f s1#1 ~f s1#3 , f s1#4 ~f s1#6 The plurality of downlink signals in the service link frequency band (f) are respectively set to a predetermined power by a plurality of transmission amplifier units 380(1) to 380(6), filtered by transmission filter units 390(1) to 390(6), and then transmitted from a plurality of SL antennas 33(1) to 33(6) to the respective cells 100C(1) to 100C(6). The terminal devices 50(1) to 50(6) of the respective cells receive the service link frequency band (f) transmitted from the relay station slave device 31. s1#1 ~f s1#3 , f s1#4 ~f s1#6 ) via a plurality of antennas 51(1) to 51(6).

[0086] 19 and 20, the multi-cell unregenerative wireless relay system 10 that performs wireless relay using a combined configuration of frequency division multiplexing and MIMO spatial multiplexing can realize an increase in the capacity of the feeder link FL between the relay station master 21 connected to a plurality of base station devices 41(1) to 41(6) and the relay station slave 31 that forms a plurality of cells 100C(1) to 100C(6). Also, compared to the conventional unregenerative relay system, it is possible to reduce the frequency bandwidth by the number of antennas, and it is possible to increase the line capacity when using the same frequency bandwidth.

[0087] 19 and 20, propagation channel information of the feeder link between the relay station master device 21 and the relay station slave device 31 (e.g., information on the matrix of the propagation path response of the feeder link) may be fed back from the relay station slave device 31 to the relay station master device 21, and the signal processing unit 230 of the relay station master device 21 may use the propagation channel information fed back from the relay station slave device 31 to control the transmission weight for MIMO spatial multiplexing (e.g., calculate the transmission weight and apply it to the transmission signal).

[0088] As described above, according to the spatial multiplexing multi-cell non-regenerative wireless relay system according to the embodiment of the present disclosure, it is possible to realize an increase in the capacity of the feeder link FL between the relay station master 21 connected to the plurality of base station devices 41 and the relay station slave 31 forming the plurality of cells 100C.

[0089] The spatial multiplexing multi-cell non-regenerative wireless relay system according to the embodiment of the present disclosure can also be applied to a case where the relay station master and the relay station slave are installed on land or sea.

[0090] Furthermore, the non-regenerative relay wireless relay system disclosed herein can realize an increase in the capacity of the feeder link FL between the relay station parent unit 21 connected to multiple base station devices 41 and the relay station child units 31 that form multiple cells, thereby contributing to the achievement of Goal 9 of the Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

[0091] It should be noted that the process steps and components of the wireless relay system 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.

[0092] For hardware implementation, the processing units and other means used to implement the above steps and components in an entity (e.g., various wireless communication devices, Node Bs, terminals, hard disk drive devices, or optical disk drive devices) may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processors (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, computers, or combinations thereof.

[0093] 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.

[0094] 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.

[0095] 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]

[0096] 10: Radio relay system 20: Gateway device (GW station) 21: Main unit of relay station 22: Feeder link antenna (GW antenna) 30: High Altitude Platform Station (HAPS: High Altitude Pseudo Satellite, Stratospheric Platform) 31: Relay station slave unit 32: Feeder link antenna (FL antenna) 33: Service link antenna (SL antenna) 34: Spatial separation processing section 35: Frequency division section 40:Base station 41:Base station equipment 50: Terminal device 51: Antenna 60: Core network equipment 70: Communication Network 80: Radio propagation path 100A: Coverage area (service area) 100C: Cell 210: First frequency conversion unit 220: Signal synthesis unit 230: Signal processing section 231: Digital filter 232: Digital filter 240: Second frequency conversion unit 241: Second frequency conversion unit 250: Transmitting amplifier section 251: Transmitting amplifier section 260: Transmit filter section 261: Transmit filter section 270: Signal synthesis unit 300: HAPS main unit 310: Receiving filter section 311: Receiving filter section 320: Receiving LNA section 321: Receiving LNA section 330: First frequency conversion unit 331: First frequency conversion unit 340: Signal branching section 350: Second frequency conversion unit 360: Signal processing section 361: Digital filter 362: Signal separation section 363: Digital filter 364: Signal separation section 365: Signal branch 366: Second frequency conversion unit 367: Digital filter 370: Third frequency conversion unit 380: Transmitting amplifier section 390: Transmit filter section

Claims

1. A wireless relay system of a non-regenerative relay type, comprising a relay station master and a relay station slave, and relaying wireless communications between a plurality of base station devices and terminal devices located in a plurality of cells corresponding to the plurality of base station devices via a feeder link between the relay station master and the relay station slave, The relay station master unit a plurality of frequency conversion units provided corresponding to the plurality of base station devices, each of which receives a plurality of downlink signals of the same frequency for the plurality of cells from the plurality of base station devices and converts the frequencies of the plurality of downlink signals into the same feeder link frequency; a plurality of feeder link antennas provided corresponding to the plurality of base station devices, each of which transmits a plurality of feeder link signals having the same feeder link frequency to the relay station slave device; transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station slave device by MIMO (Multiple Input Multiple Output) spatial multiplexing; The relay station slave device a plurality of feeder link antennas provided in the same number as the plurality of feeder link antennas of the relay station master unit, the plurality of feeder link antennas receiving the plurality of feeder link signals transmitted from the relay station master unit; a signal processing unit that applies a MIMO spatial multiplexing transmission model to a radio propagation path of a feeder link between the relay station master device and the relay station slave device, and separates a plurality of service link signals corresponding to each of the plurality of cells from a plurality of received signals received via the plurality of feeder link antennas; a plurality of frequency conversion units provided to correspond to the plurality of cells, each converting the frequency of the plurality of service link signals corresponding to the plurality of cells separated by the signal processing unit into a service link frequency; a plurality of service link antennas provided corresponding to the plurality of cells, each of the plurality of service link signals having the service link frequency being transmitted to the plurality of cells, transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station master device by the MIMO spatial multiplexing; A radio relay system characterized by:

2. In the wireless relay system of claim 1, The relay station master unit converting downlink signals of the same frequency for the plurality of cells received from the plurality of base station devices into a plurality of baseband signals of the same frequency; filtering each of the plurality of baseband signals of the same frequency; converting the frequencies of the filtered baseband signals to the same feeder link frequency; The relay station slave device converting the frequencies of a plurality of mixed signals including the plurality of feeder link signals received via the plurality of feeder link antennas into a baseband frequency; filtering each of the plurality of mixed signals at the baseband frequency; Separating a plurality of baseband signals having a plurality of baseband frequencies respectively from the filtered mixed signals of the baseband frequencies; converting the frequencies of the plurality of baseband signals to the service link frequency; transmitting a plurality of service link signals at the service link frequency via the plurality of service link antennas, respectively; A radio relay system characterized by:

3. A wireless relay system of a non-regenerative relay type, comprising a relay station parent device and a relay station child device, and relaying wireless communications between a plurality of base station devices and terminal devices located in a plurality of cells corresponding to the plurality of base station devices via feeder links between the relay station parent device and the relay station child device, The plurality of cells are divided into a plurality of cell groups different from each other, The relay station master unit a plurality of frequency multiplexing units provided corresponding to each of the plurality of cell groups, each converting a plurality of downlink signals of the same frequency received from a plurality of base station devices corresponding to each of a plurality of cells belonging to the cell group into a plurality of frequency-multiplexed feeder link signals having a plurality of mutually different feeder link frequencies arranged on a frequency axis; a plurality of feeder link antennas provided to correspond to the plurality of cell groups, each of the feeder link antennas transmitting the plurality of frequency-multiplexed feeder link signals to the relay station slave device; transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cell groups to and from the relay station slave device by MIMO (Multiple Input Multiple Output) spatial multiplexing; The relay station slave device a plurality of feeder link antennas provided in the same number as the plurality of feeder link antennas of the relay station master unit, the plurality of feeder link antennas receiving the plurality of feeder link signals transmitted from the relay station master unit; a spatial separation processing unit that applies a MIMO spatial multiplexing transmission model to a wireless propagation path of a feeder link between the relay station master device and the relay station slave device, and separates a plurality of feeder link signal groups corresponding to each of the plurality of cell groups from a plurality of received signals received via the plurality of feeder link antennas; a plurality of frequency division units provided to correspond to each of the plurality of cell groups, and dividing each of the plurality of feeder link signal groups output from the spatial separation processing unit for each of the cell groups into the plurality of feeder link signals each having the plurality of frequencies; a plurality of service link antennas provided corresponding to the plurality of cells, each of which transmits, to the plurality of cells, a plurality of service link signals obtained by converting the frequencies of the plurality of feeder link signals output from the plurality of frequency division units into service link frequencies; transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cell groups to and from the relay station master device by the MIMO spatial multiplexing; A radio relay system characterized by:

4. In the wireless relay system of claim 3, The relay station master unit converting, for each of the plurality of cell groups, a plurality of downlink signals of the same frequency received from a plurality of base station devices corresponding to a plurality of cells belonging to the cell group into a plurality of baseband signals of the same frequency; For each of the plurality of cell groups, the plurality of baseband signals of the same frequency are combined, filtered, and then converted into the plurality of frequency-multiplexed feeder link signals; The relay station slave device converting, for each of the plurality of cell groups, frequencies of a plurality of mixed signals including the plurality of feeder link signals received via the plurality of feeder link antennas into a baseband frequency; filtering each of the plurality of mixed signals at the baseband frequency; Separating a plurality of baseband signal groups, each having a plurality of baseband frequencies corresponding to each of the plurality of cell groups, from the plurality of filtered mixed signals of baseband frequencies; For each of the plurality of cell groups, the plurality of baseband signal groups are branched, converted into baseband signals of the same frequency, and filtered to output a plurality of individual baseband signals corresponding to the plurality of cells; converting the frequency bands of the plurality of individual baseband signals into a service link frequency band; A radio relay system characterized by:

5. In the wireless relay system of any one of claims 1 to 4, When the number of the plurality of feeder link antennas of the relay station master device and the number of the plurality of feeder link antennas of the relay station master device are respectively denoted by n t , the antenna spacing between the plurality of feeder link antennas of the relay station master device is denoted by d t , the antenna spacing between the plurality of feeder link antennas of the relay station slave device is denoted by d r , and the distance between the plurality of feeder link antennas of the relay station master device and the plurality of feeder link antennas of the relay station slave device is denoted by D, the following formula (1) is satisfied: A radio relay system characterized by: [Equation 1]

6. 5. The radio relay system according to claim 1, a propagation path between a plurality of feeder link antennas of the relay station parent device and a plurality of feeder link antennas of the relay station child device is a line-of-sight (LoS) environment; The MIMO spatial multiplexing transmission model is a LoS-MIMO spatial multiplexing transmission model; A radio relay system characterized by:

7. 5. The radio relay system according to claim 1, The plurality of feeder link antennas of the relay station parent unit are single-polarized antennas or multi-polarized antennas, and at least one of the distance between the antennas and the polarization planes is different, The MIMO spatial multiplexing transmission model is a polarization MIMO spatial multiplexing transmission model. A radio relay system characterized by:

8. 5. The radio relay system according to claim 1, The relay station master unit is provided in a gateway device on land or sea, The relay station slave unit is installed on an aircraft or floating body in the sky. A radio relay system characterized by:

9. 5. The radio relay system according to claim 1, The relay station master unit and the relay station slave unit are each installed on land or sea. A radio relay system characterized by:

10. 1. A wireless relay method of a non-regenerative relay system for relaying wireless communications between a plurality of base station devices and terminal devices located in a plurality of cells corresponding to the plurality of base station devices via a feeder link between a relay station master device and a relay station slave device, comprising: the relay station master receives a plurality of downlink signals of the same frequency for the plurality of cells from the plurality of base station devices by a plurality of frequency conversion units provided corresponding to each of the plurality of base station devices, and converts the frequencies of the plurality of downlink signals to the same feeder link frequency; the relay station master unit transmits a plurality of feeder link signals having the same feeder link frequency to the relay station slave unit via a plurality of feeder link antennas provided corresponding to each of the plurality of base station devices; The relay station master device transmits and receives a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station slave device by MIMO (Multiple Input Multiple Output) spatial multiplexing; the relay station slave unit receives the plurality of feeder link signals transmitted from the relay station master unit via a plurality of feeder link antennas; the relay station slave device applies a MIMO spatial multiplexing transmission model to a radio propagation path of a feeder link between the relay station master device and the relay station slave device, and separates a plurality of service link signals corresponding to each of the plurality of cells from a plurality of received signals received via the plurality of feeder link antennas; the relay station slave device converts the frequencies of the plurality of service link signals corresponding to the plurality of cells into service link frequencies by a plurality of frequency conversion units provided to correspond to the plurality of cells, respectively; the relay station slave device transmits a plurality of service link signals having the service link frequency to the plurality of cells via a plurality of service link antennas provided corresponding to the plurality of cells, respectively; the relay station slave device transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station master device by the MIMO spatial multiplexing; A wireless relay method comprising:

11. A wireless relay method of a non-regenerative relay system for relaying wireless communications between a plurality of base station devices and terminal devices located in a plurality of cells corresponding to the plurality of base station devices via feeder links between a relay station parent device and a relay station child device, comprising: The plurality of cells are divided into a plurality of cell groups different from each other, The relay station master converts, by a plurality of frequency multiplexing units provided to correspond to each of the plurality of cell groups, a plurality of downlink signals of the same frequency received from a plurality of base station devices corresponding to each of the plurality of cells belonging to the cell group into a plurality of frequency-multiplexed feeder link signals having a plurality of mutually different feeder link frequencies arranged on a frequency axis; the relay station master device transmits the plurality of frequency-multiplexed feeder link signals to the relay station slave device via a plurality of feeder link antennas provided so as to correspond to each of the plurality of cell groups; The relay station master device transmits and receives a plurality of feeder link signals corresponding to the plurality of cell groups to and from the relay station slave device by MIMO (Multiple Input Multiple Output) spatial multiplexing; the relay station slave unit receives the plurality of feeder link signals transmitted from the relay station master unit via a plurality of feeder link antennas; the relay station slave device applies a MIMO spatial multiplexing transmission model to a radio propagation path of a feeder link between the relay station master device and the relay station slave device, and separates a plurality of feeder link signal groups corresponding to each of the plurality of cell groups from a plurality of received signals received via the plurality of feeder link antennas; the relay station slave device divides, for each of the cell groups, each of the plurality of feeder link signal groups into the plurality of feeder link signals each having the plurality of frequencies by a plurality of frequency division units provided to correspond to each of the plurality of cell groups; the relay station slave device transmits, to the plurality of cells, a plurality of service link signals obtained by converting the frequencies of the plurality of feeder link signals into service link frequencies, by a plurality of service link antennas provided corresponding to the plurality of cells, respectively; the relay station slave device transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cell groups to and from the relay station master device by the MIMO spatial multiplexing; A wireless relay method comprising:

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