Wireless relay system and wireless relay method

Abstract

This invention provides a non-regenerative relay wireless relay system that can achieve high capacity in the feeder link between a relay station master unit connected to multiple base stations and relay station slave units forming multiple cells. [Solution] The wireless relay system comprises a relay station master unit and a relay station slave unit, and relays wireless communication 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 the relay station master unit and the relay station slave unit. The relay station master unit transmits and receives a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station slave unit using MIMO spatial multiplexing. The relay station slave unit transmits and receives a plurality of feeder link signals corresponding to the plurality of cells to and from the relay station master unit using MIMO spatial multiplexing.

Description

[Technical Field]

[0001] This disclosure relates to a non-regenerative relay wireless relay system. [Background technology]

[0002] Conventionally, a non-regenerative relay wireless relay system is known that comprises a relay station master unit installed on a gateway device on land or at sea, and a relay station slave unit installed on an aerial aircraft or floating device, and relays wireless communication between a base station and terminal devices of multiple 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 communication over the feeder link with the relay station master unit and wireless communication over the service link with terminal devices of multiple cells formed toward the ground. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-167539 [Overview of the Initiative]

[0004] A wireless relay system according to one aspect of the present disclosure is a non-regenerative relay wireless relay system comprising a relay station master unit and a relay station slave unit, which relays wireless communication 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 the relay station master unit and the relay station slave unit. The relay station master unit has means for transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells with the relay station slave unit by MIMO (Multiple Input Multiple Output) spatial multiplexing, and the relay station slave unit has means for transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells with the relay station master unit by MIMO spatial multiplexing.

[0005] In the wireless relay system, the relay station master unit may include a frequency conversion unit that receives multiple downlink signals of the same frequency from the multiple base stations to the multiple cells and converts the frequencies of the multiple downlink signals to a feeder link frequency, and a plurality of feeder link antennas that transmit the plurality of feeder link signals having the feeder link frequency to the relay station slave unit. The relay station slave unit may also include a plurality of feeder link antennas that receive the plurality of feeder link signals transmitted from the relay station master unit, a signal separation unit that applies a MIMO spatial multiplexing transmission model to the wireless propagation path of the feeder link between the relay station master unit and the relay station slave unit and separates the plurality of service link signals to the multiple cells from the plurality of received signals received via the plurality of feeder link antennas, a frequency conversion unit that converts the frequencies of the plurality of service link signals separated by the signal separation unit to a service link frequency, and a plurality of service link antennas that transmit the plurality of service link signals having the service link frequency to the plurality of cells.

[0006] In the wireless relay system, the frequency conversion unit of the relay station master unit may convert the frequencies of the multiple downlink signals to the same feeder link frequency, and the multiple feeder link antennas of the relay station master unit may each transmit feeder link signals having the same feeder link frequency toward the relay station slave units.

[0007] In the wireless relay system, each of the multiple cells is divided into a plurality of different cell groups, the frequency conversion unit of the relay station master unit converts the frequencies of the plurality of downlink signals to a plurality of feeder link frequencies that are different for each cell group, and each of the plurality of feeder link antennas of the relay station master unit may transmit feeder link signals having different feeder link frequencies toward the relay station slave units.

[0008] In the aforementioned wireless relay system, the propagation path between the multiple feeder link antennas of the relay station master unit and the multiple feeder link antennas of the relay station slave unit is a line-of-sight (LoS) propagation path, and the MIMO spatial multiplexing transmission model may be an LoS-MIMO spatial multiplexing transmission model.

[0009] In the wireless relay system, the multiple feeder link antennas of the relay station master unit and the relay station slave units are either single-polarization antennas or multi-polarization 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 polarization MIMO spatial multiplexing transmission model.

[0010] Another aspect of the present disclosure relates to a wireless relay method that is a non-regenerative relay method for relaying wireless communication 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 following: the relay station master unit receives multiple downlink signals of the same frequency from the multiple base stations to the multiple cells and converts the frequencies of the multiple downlink signals to a feeder link frequency; the relay station master unit transmits multiple feeder link signals having the feeder link frequency to each of the relay station slave units via multiple feeder link antennas; the relay station slave units receive the multiple feeder link signals transmitted from the relay station master unit via multiple feeder link antennas; the relay station slave units apply a MIMO spatial multiplexing transmission model to the wireless propagation path of the feeder link between the relay station master unit and the relay station slave units and separate multiple service link signals to the multiple cells from multiple received signals received via the multiple feeder link antennas; the relay station slave units convert the frequencies of the multiple service link signals to a service link frequency; and the relay station slave units transmit multiple service link signals having the service link frequency to each of the multiple cells via multiple service link antennas.

[0012] In the aforementioned wireless relay system and wireless relay method, the relay station master unit may be provided on a gateway device on land or at sea, and the relay station slave unit may be provided on an aircraft or floating object in the air. The aircraft or floating object may be a HAPS ("High Altitude Pseudo-Satellite" or "High Altitude Platform Station"), artificial satellites (for example, low Earth orbit (LEO) satellites, medium Earth orbit (MEO) satellites, geostationary orbit communication satellites, etc.), balloons, drones, or unmanned aerial vehicles (UAVs) such as UAS (Unmanned Aircraft Systems).

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

[0014] The programs executed in the aforementioned relay station master unit and relay station slave unit may include a trained model used for machine learning, a newly created trained model using machine learning, or a trained model updated using machine learning. [Brief explanation of the drawing]

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

[0016] Embodiments of this disclosure will be described below with reference to the drawings. Note that each drawing is merely a schematic representation of the shape, size, positional relationships, correspondences, configuration, processing, steps, etc., to the extent that the contents of this disclosure can be understood. Therefore, this disclosure is not limited to the shapes, sizes, positional relationships, correspondences, configurations, processing, steps, and steps exemplified in each drawing. Furthermore, the numerical values ​​exemplified in this disclosure are merely preferred examples, and therefore, this disclosure is not limited to the numerical values ​​exemplified.

[0017] One embodiment of the wireless relay system described herein is a non-regenerative relay multi-cell wireless relay system (hereinafter also referred to as "multi-cell non-regenerative wireless relay system," "non-regenerative wireless relay system," or "wireless relay system") applicable to both aerial systems such as HAPS and drones, and ground systems. In particular, the multi-cell wireless relay system of this embodiment can reduce power consumption and weight of aerial systems with HAPS. Furthermore, in non-regenerative wireless relay systems where it is difficult to increase capacity through MIMO spatial multiplexing, it is possible to increase the capacity of the feeder link between the relay station master unit and the relay station slave unit based on multi-cell wireless relay. The wireless relay system according to this embodiment is suitable for realizing a 3D network in mobile communications compliant with the LTE (Long Term Evolution)-Advanced standard, or in next-generation mobile communications compliant with the fifth generation (hereinafter also referred to as "5GNR") which supports simultaneous connection to a large number of terminal devices and low latency.

[0018] [Non-regenerative multi-cell wireless relay system] Figure 1 is a diagram showing an example of the overall configuration of a non-regenerative relay type multi-cell wireless relay system (hereinafter also referred to as the "wireless relay system") 10 according to the embodiment of this disclosure. The wireless relay system 10 comprises a relay station master unit 21 installed on a gateway device 20 on land or at sea, and a relay station slave unit 31 installed on an aircraft or floating object in the air, and is a non-regenerative relay type wireless relay system that relays wireless communication between a base station 40 having one or more base station devices 41 and terminal devices 50 located in multiple cells 100C(1) to 100C(6) via a feeder link FL between the relay station master unit 21 and the relay station slave unit 31.

[0019] In the wireless relay system of this embodiment, the flying or floating object on which the relay station slave unit 31 is mounted is, for example, a high-altitude platform station ("high-altitude pseudo-satellite", "stratospheric platform") (hereinafter also referred to as "HAPS" or "high-altitude platform (HAPS)") 30 as an airborne wireless relay device. The HAPS 30 is located in the 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 a flying or floating object (for example, a solar plane, airship, drone, balloon) 300 that is controlled by autonomous control or external control to float or fly in the airspace (floating airspace) at a predetermined altitude above the ground or sea surface, with the relay station slave unit 31 mounted on it. Note that the HAPS 30 that can function as an airborne communication relay device may also be an artificial satellite such as a low Earth orbit (LEO) satellite or a geostationary orbit (GEO) satellite on which a relay communication station is mounted.

[0020] Furthermore, the communication system via HAPS30 in 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 HAPS30 communicates, a gateway device (hereinafter also referred to as the "GW station", "gateway station", or "feeder station") 20, or a base station 40. In addition, in the HAPS communication system, the system having the HAPS30 etc. located in the air is the air system, and the system having the GW station 20 etc. located on the ground (or at sea) is the ground system.

[0021] The airspace in which HAPS30 is located is, for example, stratospheric airspace at altitudes of 11 km or more and 50 km or less above ground (or over water such as the sea or a lake). This airspace may also be airspace at altitudes of 15 km to 25 km where meteorological conditions are relatively stable, and may be airspace at an altitude of approximately 20 km in particular.

[0022] Because HAPS30 flies at an altitude lower than that of typical satellites but higher than ground and sea base stations, it can achieve high line-of-sight coverage while having less propagation loss than satellite communications. Due to this characteristic, it is also possible to provide communication services from HAPS30 to user equipment such as ground or sea cellular mobile terminals (mobile stations) 50. By providing communication services from HAPS30, a large area that was previously covered by numerous ground or sea base stations can be covered at once with a small number of HAPS30s, offering the advantage of providing low-cost and stable communication services.

[0023] The HAPS30 relay station slave unit 31 uses a service link antenna (hereinafter referred to as "SL antenna") 33 to form multiple beams directed toward the ground (or sea surface) for wireless communication with the user's terminal equipment (hereinafter referred to as "UE" (user equipment)) 50, thereby forming multiple cells (also called "HAPS cells") 100C(1) to 100C(6) that can communicate wirelessly with the UE 50. The total radius of the service area (also called "HAPS service area") 100A, which consists of the footprints of these cells on land (or sea), is, for example, several tens to 100 kilometers.

[0024] In this embodiment, the relay station slave unit 31 of the HAPS30 forms 6 cells 100C(1) to 100C(6), but the multiple cells formed by the relay station slave unit 31 may be 2 cells, 3 cells, 4 cells, 5 cells, or 7 cells, or 8 cells or more.

[0025] UE50 is a terminal device used by a user on land or at sea. Examples of UE50s include mobile phones, smartphones, and portable personal computers with mobile communication capabilities. They are also called mobile terminals, mobile stations, mobile devices, or portable communication terminals. UE50s may be modular mobile stations incorporated into vehicles such as automobiles, or aircraft such as drones (which are remotely controlled small helicopters), or they may be terminal devices for IoT (Internet of Things) devices. UE50s may also be user devices used by a user inside an aircraft such as an airplane.

[0026] The UE50 can communicate with the base station equipment 41 of the base station 40 connected to the core network equipment 60 of the mobile communication network via the relay station slave unit 31 and GW station 20 of the HAPS30 using the FDD method, the TDD method, or both. The UE50 can also access external communication networks 70 such as the Internet via the base station equipment 41 and the core network equipment 60 of the mobile communication network.

[0027] The HAPS30 repeater slave unit 31 is a repeater slave unit that communicates wirelessly with a repeater master unit (repeater master unit) 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 base station 40 on land (or at sea). The repeater slave unit 31 is connected to the core network device 60 of the mobile communication network via a feeder link antenna (hereinafter referred to as an "FL antenna") 32, which enables wireless communication with the GW station 20 and base station 40 installed on land or at sea.

[0028] The feeder link FL communication between the HAPS30 relay station slave unit 31 and the GW station 20 relay station master unit 21 may be performed by wireless communication using radio waves such as microwave, millimeter wave, or submillimeter wave, 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 as it moves through the air. By having the GW antenna 22 track the HAPS 30, even when using a GW antenna 22 with high directivity such as a parabolic antenna, the deterioration of the communication quality of the feeder link FL due to the movement of the HAPS 30 can be suppressed.

[0030] The base station 40 is equipped with multiple base station devices (e.g., eNodeB, gNodeB) 41 to correspond to multiple 100C(1) to 100C(6). Each of the multiple base station devices 41, for example in the case of an LTE eNodeB, consists of a remote radio head (RRH, also called a remote radio unit (RRU)) and a base band unit (BBU). The RRH and BBU may be connected by optical fiber lines and placed at a distance from each other. Alternatively, multiple BBUs may be consolidated and installed in one location.

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

[0032] Each of the BBUs of the multiple base station devices 41 comprises, for example, a base station control unit, a transmission path interface unit, a timing control unit, and a baseband unit, and is connected to the core network of the mobile communication network via a predetermined interface (for example, the 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® with the core network, and processes a predetermined protocol to send and receive IP packets. The timing control unit generates various clocks used inside the base station based on a reference clock extracted from signals received via the packet transmission path or from GNSS (Global Navigation Satellite System) signals received from artificial satellites. The baseband unit performs conversion (modulation / demodulation) between IP packets sent and received through the transmission path interface unit and OFDM signals (baseband signals), which are radio signals.

[0033] Each HAPS30 may autonomously control the levitation movement (flight) of the HAPS main unit 300 and the processing at the relay station slave unit 31 by executing a control program in a control unit consisting of a computer or the like that is built inside. For example, each HAPS30 may acquire the current location information of the HAPS itself (e.g., GPS location information), pre-stored location control information (e.g., flight schedule information), and location information of other HAPS30 located in the vicinity, and autonomously control the levitation movement (flight) and processing at the relay station slave unit 31 based on this information.

[0034] Furthermore, the levitation and movement (flight) of each HAPS30 and the processing at the relay station slave unit 31 may be controlled by a management device (also called a "remote control device" or "central control server") located in a communication center or the like connected to the core network of the mobile communication network. The management device can be composed of, for example, a computer device such as a PC or a server. In this case, the HAPS30 is equipped with 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 of the management device. The control communication unit may be assigned terminal identification information (e.g., an IP address, a telephone number, etc.) so that it can communicate with the management device. The MAC address of the communication interface may be used to identify the control communication unit of the HAPS30.

[0035] The transmission and reception of control information and monitoring information between HAPS30 and the management device can be performed, for example, via an LTE communication line passing through the core network device 60, base station 40, and GW station 20 of the mobile communication network. Alternatively, the transmission and reception of control information and monitoring information may be performed using a satellite link of mobile communication via an artificial satellite, or using a satellite link via the Internet and an artificial satellite.

[0036] The monitoring information transmitted from HAPS30 may include at least one of the following: information regarding the levitation movement (flight) of the HAPS itself or surrounding HAPS and processing at the relay station slave unit 31; monitoring information including the reception level measured by HAPS30 for the received power of the feeder link between HAPS30 and GW station 20; and information regarding the status of HAPS30 and observation data acquired by various sensors. The monitoring information may also include at least one of the following: the current position and attitude information of HAPS30, flight path information (flight schedule information, flight route history information), airspeed, ground speed and thrust direction, wind speed and direction of the airflow around HAPS30, and atmospheric pressure and temperature around HAPS30. The control information may include flight information such as the target flight route information of HAPS30.

[0037] HAPS30 and the management device may acquire weather forecast information for the area including the feeder link radio propagation path, maintenance schedule information for GW station 20 or base station 40, received level monitor information for the feeder link with GW station 20 measured by HAPS30, flight path information of HAPS30, current location information and attitude information of HAPS30. This information may be obtained, for example, from a server of the core network (mobile communication network) or an Internet server that manages each piece of information. The management device may also acquire maintenance schedule information for GW station 20 or base station 40 from GW station 20 or base station 40 via a predetermined interface (for example, the LTE S1 interface) through the core network device 60 of the mobile communication network, or from a server that manages GW station 20 or base station 40.

[0038] The duplexing method for the uplink and downlink of the service link SL wireless communication between the relay station slave unit 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. Furthermore, the access method for the service link SL wireless communication between the relay station slave unit 31 and the terminal device 50 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. In addition, the wireless communication may utilize MIMO (Multi-Input and Multi-Output) technology, which has functions such as diversity coding, transmit 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 embodiments, the HAPS 30, which has a relay station slave unit 31 that communicates wirelessly with the terminal device 50, is illustrated and described as a solar-powered plane type HAPS; however, the HAPS 30 may also be an unmanned airship type HAPS. Furthermore, the following embodiments can be similarly applied to airborne communication relay devices consisting of other aircraft or floating bodies other than HAPS.

[0040] Furthermore, the link between HAPS30 and base station 40 via GW station 20 is called the "feeder link" (FL), and the link between HAPS30 and terminal equipment 50 is called the "service link" (SL). In particular, the section between HAPS30 and GW station 20 is called the "feeder link radio section." Also, the downlink of communication from GW station 20 to terminal equipment 50 via HAPS30 is called the "forward link," and the uplink of communication from terminal equipment 50 to GW station 20 via HAPS30 is called the "reverse link."

[0041] The relay station slave unit 31 mounted on the HAPS30 main unit (device) 300 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 wireless relay systems for feeder links: the non-regenerative relay system, which relays wireless signals as they are without demodulating them, and the regenerative relay system, which demodulates wireless signals before relaying them.

[0042] In the non-regenerative relay repeater system shown in Figure 2(a), the relay station 301 mounted on the HAPS30 main unit (aircraft) 300 functions as a non-regenerative repeater, directly relaying communication between the base station equipment 41 connected to the core network equipment 60 and the UE50 via a bent-pipe-like path through the GW station 20 and the relay station 301. In the non-regenerative relay system, since the base station equipment 41 that serves as the relay source can be installed on the ground, the equipment (wireless relay equipment) of the relay station 301 mounted on the HAPS30 can be made lighter and simpler.

[0043] On the other hand, in the regenerative relay base station system shown in Figure 2(b), the relay station 302 mounted on the HAPS30 main unit (aircraft) 300 has a base station device 41, and the base station device 41 of the relay station 302 is connected to the core network equipment 60 of the mobile communication network via a backhaul line such as FWA, and regenerates the transmitted and received signals to perform wireless communication with the UE50. In the regenerative relay method, since it is necessary to mount a modem device for modulation and demodulation and all the base station devices 41 for multiple cells that constitute the service link on the HAPS30, the wireless equipment mounted on the HAPS30 becomes heavy and complex, but since the transmitted signal is IP data, frequency utilization efficiency can be improved by data compression.

[0044] [Wireless relay using MIMO spatial multiplexing] In Figure 1, the HAPS communication system, including the wireless relay system 10 of this embodiment, covers a vast area 100A compared to a typical ground base station installed on land (or at sea). The communication links of the HAPS communication system consist of a service link SL connecting the HAPS 30 and the terminal equipment 50, and a feeder link (hereinafter also referred to as "HAPS feeder link") FL connecting the HAPS 30 and the GW station 20 of the ground system. The feeder link FL of the HAPS communication system requires a high-capacity line to transmit and receive all traffic from the terminal equipment 50 of all users located in the vast coverage area 100A.

[0045] As a method for increasing the capacity of the HAPS feeder link in the aerial system shown in Figure 1, spatial multiplexing using MIMO (Multiple Input Multiple Output) (hereinafter also referred to as "MIMO spatial multiplexing") can be considered. However, in non-regenerative wireless relay systems where the HAPS30 in the aerial system can be made to have low power consumption and light weight, the application of MIMO spatial multiplexing is difficult.

[0046] Figure 3 shows an example of MIMO spatial multiplexing transmission. In Figure 3, the MIMO system consists of multiple transmitting antennas 22(1), 22(2) and multiple receiving antennas 32(1), 32(2). In MIMO spatial multiplexing transmission, multiple data streams, each with different data allocated to them, are simultaneously transmitted from multiple transmitting antennas 22(1), 22(2) on radio space channels CH(1), CH(2) of the same frequency. The independence (orthogonality) of radio space channels CH(1), CH(2) is utilized to separate and process these data streams at the receiving end.

[0047] In the non-regenerative relay method shown in Figure 4, the relay station master unit 21 does not demodulate the radio signal (fs) received from the base station device 41 into data, but instead relays it directly to the relay station slave unit 31. Therefore, it is not possible to distribute the data to multiple transmitting antennas 22. Consequently, it is not possible to divide the data stream demodulated by the source relay station master unit 21 into individual paths formed by MIMO spatial multiplexing and transmit them in parallel to the relay station slave unit 31 (simultaneously transmitting different data streams to each transmitting antenna), as is possible in the regenerative relay method shown in Figure 5.

[0048] In this embodiment, in a non-regenerative wireless relay system where increasing capacity through MIMO spatial multiplexing is difficult, a large-capacity feeder link is achieved based on multi-cell wireless relay.

[0049] Figure 6 is an explanatory diagram showing an example of a multi-cell wireless relay system that does not use MIMO spatial multiplexing, as per the reference example. Figure 7 is an explanatory diagram showing an example of a multi-cell wireless relay system that uses MIMO spatial multiplexing according to the embodiment. In Figures 6 and 7, parts common to Figure 1 described above are denoted by the same reference numerals, and their explanations are omitted.

[0050] In the HAPS communication system's Service Link SL, a multi-cell configuration with multiple cells is assumed to increase capacity. In the conventional non-regenerative radio system shown in the reference example in Figure 6, for example, the relay station master unit 21 receives the frequencies f of multiple cells 100C(1) to 100(4) from multiple base station devices 41(1) to 41(4). sThe signal is frequency-converted, and multiple frequencies f are arranged on the frequency axis. f#1 ,f f#2 ,f f#3 ,f f#4 These signals are wirelessly relayed to the relay station slave unit 31 of the HAPS 30 in the air as multiple feeder link signals, each having its own characteristics.

[0051] On the other hand, in the non-regenerative relay system according to this embodiment shown in Figure 7, the relay station master unit 21 has means for transmitting and receiving multiple feeder link signals corresponding to multiple cells 100C(1) to 100C(4) with the relay station slave unit 31 by MIMO spatial multiplexing, and the relay station slave unit 31 has means for transmitting and receiving multiple feeder link signals corresponding to multiple cells 100C(1) to 100C(4) with the relay station master unit 21 by MIMO spatial multiplexing. For example, the relay station master unit 21 receives the frequency f of multiple cells 100C(1) to 100(4) from multiple base station devices 41(1) to 41(4) s The signals are sent at the same feeder link frequency f f The feeder link signal is converted to a different frequency and transmitted from multiple transmitting antennas 22(1) to 22(4) that are different for each cell. The relay station slave unit 31 performs spatial separation processing on the signals (feeder link signals) from multiple cells received by the multiple receiving antennas 32(1) to 32(4) based on the 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 unit 21 and the multiple receiving antennas 32(1) to 32(4) of the relay station slave unit 31 via multiple channels CH(1) to CH(4) that are independent of each other, thereby relaying multi-cell wireless signals non-regeneratively. According to the non-regenerative relaying method of this embodiment, it is possible to reduce the frequency bandwidth by the number of antennas compared to the conventional non-regenerative relaying method according to the reference example described above, and it is possible to increase the capacity of the line when using the same frequency bandwidth.

[0052] The spatial separation processing of the received signal at the relay station slave unit 31 can be performed, for example, by estimating the 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 unit 21, and then applying any signal separation algorithm (e.g., a method using receive weights based on zero-forcing (ZF), a method using receive weights based on least mean squares error (MMSE), a serial canceller (SIC) method, a maximum likelihood detection (MLD) method, etc.) based on that propagation path response H. Here, the estimation and updating of the propagation path response H may be performed, for example, periodically, or when the position of the HAPS 30 having the relay station slave unit 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 unit 31 may be an LoS-MIMO spatial multiplexing transmission model that assumes the propagation path between the multiple feeder link antennas 22 of the relay station master unit 21 and the multiple feeder link antennas 32 of the relay station slave unit 31 is a line-of-sight (LoS) propagation path. Alternatively, the MIMO spatial multiplexing transmission model may be a polarization-MIMO spatial multiplexing transmission model that assumes the multiple feeder link antennas 22 and 32 of the relay station master unit 21 and the relay station slave unit 31 are single-polarization antennas or multi-polarization antennas, and that at least one of the inter-antenna distance and polarization plane is different.

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

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

[0056] The plurality of first frequency conversion units 210(1) to 210(4) each receive the downlink signal of the same frequency (f s1#1~4 ) for each cell transmitted from the plurality of base station (BS) devices 41(1) to 41(4), and convert the signal to a plurality of mutually adjacent frequencies (f b1#1 , f b2#2 , f b3#3 , f b4#4Converts to a baseband signal with multiple frequencies (f b1#1 ,f b2#2 ,f b3#3 ,f b4#4 The baseband signal of ) is combined in the signal combining unit 220, filtered in the signal processing unit 230, and then converted to a predetermined feeder link frequency (f) in the second frequency conversion unit 240. f1#1 ,f f2#2 ,f f3#3 ,f f4#4 It is converted to the feeder link frequency (f f1#1 ,f f2#2 ,f f3#3 ,f f4#4 The feeder link signal, which includes signals destined for each cell having ), is powered to a predetermined level by the transmitting amplifier unit 250, filtered by the transmitting filter unit 260, and then transmitted from the GW antenna 22 to the relay station slave unit 31.

[0057] In Figure 9, the relay station slave unit 31 at 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) from the relay station master unit 21 received via the FL antenna 32 f1#1 ~f f4#4 The signal is filtered by the receiving filter section 310, amplified by the receiving LNA section 320, and then converted to a baseband frequency (f) by the first frequency conversion section 330. b1#1 ~f b4#4 It is converted to ) and then split into multiple baseband signals at the signal branching section 340. Each of the multiple baseband signals is converted to the same frequency band (f) at multiple second frequency conversion sections 350(1) to 350(4). (b1)#1~4 It is converted to (f), filtered by multiple digital filters 361(1) to 361(4) of the signal processing unit 360, and then processed by multiple third frequency conversion units 370(1) to 370(4) to access the service link frequency band (fs1#1~4 It is converted to the service link frequency band (f s1#1~4 Each of the multiple downlink signals is converted to a predetermined power by multiple transmitting amplifier units 380(1) to 380(4), filtered by transmitting filter units 390(1) to 390(4), and then transmitted from multiple SL antennas 33(1) to 33(4) to each cell 100C(1) to 100C(4). Each cell's terminal device 50(1) to 50(4) receives the service link frequency band (f) transmitted from the relay station slave unit 31. s1#1~4 Multiple downlink signals are received via multiple antennas 51(1) to 51(4).

[0059] Figure 11 is a block diagram showing an example of the main components of a relay station master unit 21 in the multi-cell wireless relay system 10 according to the embodiment of Figure 7. Figure 12 is a block diagram showing an example of the main components of a relay station slave unit 31 in the multi-cell wireless relay system according to the embodiment of Figure 7. Although the examples in Figures 11 and 12 describe the case of 4 cells, similar configurations can be extended and applied to cases of 2 cells, 3 cells, 5 cells, and 6 or more cells.

[0060] In Figure 11, the relay station master unit 21, which is the source of the relay, comprises a plurality of first frequency conversion units 210(1) to 210(4), a signal processing unit 230 having 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 transmitting amplifier units 250(1) to 250(4), and a plurality of transmitting filter units 260(1) to 260(4).

[0061] Each of the multiple first frequency converters 210(1) to 210(4) converts the same frequency (f) for each cell transmitted from the multiple base station (BS) devices 41(1) to 41(4). s1#1~4 ) receives the downlink signal and the same frequency (f b1#1 ,f b1#2 ,f b1#3 ,f b1#4 Converts to a baseband signal of the same frequency (f). b1#1 ,f b1#2 ,f b1#3 ,f b1#4The baseband signal of ) is filtered by the signal processing unit 230 and then converted to the same feeder link frequency (f) by multiple second frequency conversion units 240. f1#1 ,f f1#2 ,f f1#3 ,f f1#4 It is converted to the same feeder link frequency (f f1#1 ,f f1#2 ,f f1#3 ,f f1#4 Each feeder link signal destined for a cell having a feeder link is converted to a predetermined power by a plurality of transmitting amplifier units 250(1) to 250(4), filtered by a plurality of transmitting filter units 260(1) to 260(4), and then transmitted from a plurality of GW antennas 22(1) to 22(4) via the feeder link radio propagation path 80 to the relay station slave unit 31.

[0062] In Figure 12, the relay station slave unit 31 at the relay destination comprises 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] Each of the multiple FL antennas 32(1) to 32(4) receives multiple feeder link signals (f) transmitted from the multiple GW antennas 22(1) to 22(4) of the relay station master unit 21 via the feeder link radio propagation path 80. f1#1 ~f f4#4 The mixed signal (f) is received by each of the multiple FL antennas 32(1) to 32(4). f1#1~#4 The signal is filtered by multiple receiving filter sections 310(1) to 310(4), amplified by receiving LNA sections 320(1) to 320(4), and then converted to a baseband frequency (f) by the first frequency conversion section 330(1) to 330(4). b1#1~#4 It is converted to the baseband frequency (f).b1#1~#4 Each of the multiple mixed signals of ) is filtered by multiple digital filters 361(1) to 361(4) of the signal processing unit 360, and then the signal separation unit 362 uses the aforementioned arbitrary signal separation algorithm to filter multiple baseband frequencies (f b1#1~ f b1#4 The multiple baseband signals (f b1#1~ f b1#4 Each of these units uses multiple second frequency conversion units 370(1) to 370(4) to access the service link frequency band (f s1#1~4 It is converted to the service link frequency band (f s1#1~4 Each of the multiple downlink signals is converted to a predetermined power by multiple transmitting amplifier units 380(1) to 380(4), filtered by transmitting filter units 390(1) to 390(4), and then transmitted from multiple SL antennas 33(1) to 33(4) to each cell 100C(1) to 100C(4). Each cell's terminal device 50(1) to 50(4) receives the service link frequency band (f) transmitted from the relay station slave unit 31. s1#1~4 Multiple downlink signals are received via multiple antennas 51(1) to 51(4).

[0064] According to the multi-cell non-regenerative wireless relay system 10 that performs wireless relay by MIMO spatial multiplexing as shown in Figures 11 and 12, it is possible to increase the capacity of the feeder link FL between the relay station master unit 21 connected to multiple base station devices 41(1) to 41(4) and the relay station slave units 31 that form multiple cells 100C(1) to 100C(4). Furthermore, compared to conventional non-regenerative relay methods, it is possible to reduce the frequency bandwidth by the number of antennas, and when using the same frequency bandwidth, it is possible to increase the capacity of the line.

[0065] In the multi-cell non-regenerative wireless relay system 10 shown in Figures 11 and 12, propagation channel information of the feeder link between the relay station master unit 21 and the relay station slave unit 31 (for example, information on the matrix of the propagation path response of the feeder link) may be fed back from the relay station slave unit 31 to the relay station master unit 21. The signal processing unit 230 of the relay station master unit 21 may then use the propagation channel information fed back from the relay station slave unit 31 to control the transmit weight for MIMO spatial multiplexing (for example, calculating the transmit weight and applying it to the transmit signal). As the feedback communication line, for example, a control line separately constructed between the relay station master unit 21 and the relay station slave unit 31 may be used, or a separately constructed inter-relay station cooperation network may be used, or a part of the reverse link communication line of the feeder link from the relay station slave unit 31 to the relay station master unit 21 may be used.

[0066] [Using LoS-MIMO] Figure 13 is an explanatory diagram illustrating an example of normal MIMO communication between multiple antennas 22(1) to 22(3) of the relay station master unit 21 and multiple antennas 32(1) to 32(3) of the relay station slave unit 31 in a multipath-rich environment (multi-wave environment) propagation path 81. Figure 14 is an explanatory diagram illustrating an example of LoS-MIMO communication between multiple antennas 22(1) to 22(3) of the relay station master unit 21 and multiple antennas 32(1) to 32(3) of the relay station slave unit 31 in a line-of-sight (LoS) propagation path 82. The normal MIMO communication in Figure 13 is effective in propagation paths 81, which are multipath-rich environments with many reflections and diffractions outside the line of sight, and have low correlation between antennas. In this case, the eigenvalues ​​of each channel (iid Rayleigh channel) CH(1) to CH(3), which are formed to independently follow a Rayleigh distribution by MIMO, will vary. Therefore, when assigning the signals of each cell 100C(1) to each channel CH(1) to CH(3), variations in quality will occur between cells.

[0067] On the other hand, in the polarization MIMO and line-of-sight (LoS) environment propagation path 82 shown in Figure 14, in LoS-MIMO communication where the antenna spacing (dt,dr) and distance (D) are appropriately considered as shown in Figure 15 and equation (1) below, the eigenvalues ​​of each channel CH(1) to CH(3) can be made to be approximately the same size. Therefore, by assigning the signals of each cell to these channels CH(1) to CH(3), multi-cell wireless relay with less variation in quality between cells becomes possible in MIMO spatial multiplexing.

[0068]

number

[0069] [Combined configuration of frequency multiplexing and MIMO spatial multiplexing] In other embodiments of this disclosure, a group of multiple cells constituting a multicell is configured by frequency multiplexing a number of cells equal to the number of transmitting antennas, and the signals from the multiple cells received by the receiving antenna are subjected to spatial separation processing and frequency division processing to wirelessly relay the multicell wireless signal by LoS spatial multiplexing. For example, the multiple cells are each divided into multiple different cell groups. The frequency conversion unit of the relay station master unit 21 converts the frequency f of the multiple downlink signals s This involves multiple feeder link frequencies f, each with different frequencies for each cell group. f Convert to. Each of the multiple feeder link antennas 22 of the relay station master unit 21 has a different feeder link frequency f f A feeder link signal having the following characteristics is transmitted to the relay station slave unit 31.

[0070] Figure 16 is an explanatory diagram showing an example of a multi-cell wireless relay system using frequency multiplexing transmission according to a reference example. Figure 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 the embodiment. In Figures 16 and 17, parts common to Figures 1, 6 and 7 described above are denoted by the same reference numerals and their descriptions are omitted.

[0071] In the multi-cell wireless relay system shown in Figure 16, the relay station master unit 21 receives the frequencies f of multiple cells 100C(1) to 100(6) from multiple base station devices 41(1) to 41(6). s The signal is frequency-converted, and multiple frequencies f are arranged on the frequency axis. f#1 ,f f#2 ,f f#3 ,f f#4 ,f f#5 ,f f#6 Multiple feeder link signals, each having their own characteristics, are simultaneously transmitted from the GW antenna 22 to the relay station slave unit 31 of the HAPS 30 in the air via the propagation path 82 in the LoS environment for wireless relay.

[0072] On the other hand, in the multi-cell wireless relay system shown in Figure 17, the relay station master unit 21 receives the frequencies f of multiple cells 100C(1) to 100(6) from multiple base station devices 41(1) to 41(6). s Among the signals, the frequency f of multiple cells 100C(1) to 100(3) belonging to the first cell group s The signal is frequency-converted, and multiple frequencies f are arranged on the frequency axis. f#1 ,f f#2 ,f f#3 Multiple feeder link signals, each having one of these characteristics, are simultaneously transmitted from the first GW antenna 22(1) to the relay station slave unit 31 of the HAPS 30 in the air via the propagation path 82 in the LoS environment for wireless relay.

[0073] Furthermore, the relay station master unit 21 controls the frequency f of multiple cells 100C(4) to 100(6) belonging to the second cell group. s The signal is frequency-converted, and multiple frequencies f are arranged on the frequency axis. f#4 ,f f#5 ,f f#6 Multiple feeder link signals, each having one of these characteristics, are wirelessly relayed from the second GW antenna 22(2) to the relay station slave unit 31 of the HAPS 30 in the air via the propagation path 82 in the Loss environment.

[0074] FIG. 18 is an explanatory diagram showing an example of a main configuration of the multi-cell wireless relay system 10 of FIG. 17. In FIG. 18, a first frequency multiplexing unit 23(1) of a relay station base unit 21 outputs a plurality of frequencies f output from a plurality of base station devices (gNB) 41(1) to 41(6) s among downlink signals, frequencies f of a plurality of cells 100C(1) to 100(3) belonging to a first cell group s are frequency-converted to obtain a plurality of frequencies f arranged on a frequency axis f#1 , f f#2 , f f#3 as a plurality of feeder link signals respectively having the above frequencies, the signals are simultaneously transmitted from a first GW antenna 22(1) via a feeder link propagation path 82 in a LoS environment toward a plurality of FL antennas 32(1) and 32(2) of a relay station slave unit 31 of HAPS 30 in the sky.

[0075] In FIG. 18, a second frequency multiplexing unit 23(2) of the relay station base unit 21 handles frequencies f of a plurality of cells 100C(4) to 100(6) belonging to a second cell group s are frequency-converted to obtain a plurality of frequencies f arranged on a frequency axis f#4 , f f#5 , f f#6 as a plurality of feeder link signals respectively having the above frequencies, the signals are simultaneously transmitted from a second GW antenna 22(2) via a feeder link propagation path 82 in a LoS environment toward a plurality of FL antennas 32(1) and 32(2) of the relay station slave unit 31 of HAPS 30 in the sky.

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

[0077] Figure 19 is a block diagram showing an example of the main components of a relay station master unit 21 in the multi-cell wireless relay system 10 according to the embodiment of Figure 17. Figure 20 is a block diagram showing an example of the main components of a relay station slave unit 31 in the multi-cell wireless relay system 10 according to the embodiment of Figure 17. Although the examples in Figures 19 and 20 describe the case of 6 cells, similar configurations can be extended and applied to cases of 4 cells, 5 cells, and 7 or more cells. Furthermore, the number of cell groups may be 3 or more, and the number of cells belonging to each cell group may be 2 or 4 or more.

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

[0079] Each of the multiple first frequency converters 210(1) to 210(6) converts the same frequency (f) for each cell transmitted from the multiple base station (BS) devices 41(1) to 41(6). s1#1~6 ) receives the downlink signal and the same frequency (f b1#1 ,f b1#2 ,f b1#3 ,f b1#4 ,f b1#5 ,f b1#6 Convert to a baseband signal of ). Here, the same frequency (f) is applied to multiple cells 100(1) to 100(3) of the first cell group. s1#1~3 Multiple downlink signals of ) are arranged in a predetermined bandwidth on the frequency axis, with multiple frequencies (f b1#1 ,f b2#2 ,f b3#3 It is converted to a baseband signal of the same frequency (f) for multiple cells 100(4) to 100(6) in the second cell group. s1#1~3 Multiple downlink signals of ) are arranged in the same predetermined bandwidth as the first cell group on the frequency axis, with multiple frequencies (f b1#4 ,f b2#5 ,f b3#6 It is converted to a baseband signal.

[0080] Multiple frequencies (f) corresponding to the first cell group b1#1 ,f b2#2 ,f b3#3 The baseband signal of ) is combined in the signal combining unit 270(1), filtered by the digital filter 232(1) of the signal processing unit 230, and then converted to a feeder link frequency (f) of a predetermined frequency band in the second frequency conversion unit 241(1). f1#1 ,f f2#2 ,f f3#3 It is converted to the feeder link frequency (f) corresponding to the first cell group. f1#1 ,f f2#2 ,f f3#3 Each feeder link signal destined for a cell is given a predetermined power by the transmitting amplifier unit 251(1), filtered by the transmitting filter unit 261(1), and then transmitted from the GW antenna 22(1) to the relay station slave unit 31 via the feeder link radio propagation path 80.

[0081] Multiple frequencies (f) corresponding to the second cell group b1#4 ,f b2#5 ,f b3#6 The baseband signal of the first cell group is combined in the signal combining unit 270(2), filtered by the digital filter 232(2) of the signal processing unit 230, and then converted in the second frequency conversion unit 241(2) to the feeder link frequency (f) of the same predetermined frequency band as the first cell group. f1#4 ,f f2#5 ,f f3#6 It is converted to the feeder link frequency (f) corresponding to the second cell group. f1#4 ,f f2#5 ,f f3#6 Each feeder link signal destined for a cell is given a predetermined power by the transmitting amplifier section 251(2), filtered by the transmitting filter section 261(2), and then transmitted from the GW antenna 22(2) to the relay station slave unit 31 via the feeder link wireless propagation path 80.

[0082] In Figure 20, the relay station slave unit 31 at the relay destination includes a plurality of receiving filter units 311(1), 311(2), a plurality of receiving LNA (low-noise amplifier) ​​units 321(1), 321(2), a plurality of first frequency conversion units 331(1), 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] Each of the multiple FL antennas 32(1), 32(2) receives multiple feeder link signals (f) transmitted from the multiple GW antennas 22(1), 22(2) of the relay station master unit 21 via the feeder link radio propagation path 80. f1#1 ~f f3#3 ,f f1#4 ~f f3#6 The mixed signal (f) is received by each of the multiple FL antennas 32(1) and 32(2). f1#1 ~f f3#3 ,f f1#4 ~f f3#6The signal is filtered by multiple receiving filter units 311(1), 311(2), amplified by receiving LNA units 321(1), 321(2), and then converted to a baseband frequency (f) by first frequency conversion units 331(1), 331(2). b1#1 ~f b3#3 ,f b1#4 ~f b3#6 It will be converted to ).

[0084] The signal processing unit 360 includes a plurality of input-side digital filters 363(1), 363(2), a signal separation unit 364, a plurality of signal branching units 365(1), 365(2), a plurality of second frequency conversion units 366(1) to 366(6), and a plurality of output-side digital filters 367(1) to 367(6). The baseband frequency (f) corresponding to the first cell group b1#1 ~f b3#3 ,f b1#4 ~f b3#6 Each of the multiple mixed signals of ) is filtered by multiple digital filters 363(1) and 363(2) of the signal processing unit 360, and then the signal separation unit 364 uses the aforementioned arbitrary signal separation algorithm to process the multiple baseband frequencies (f) of the first cell group. b1#1 ~f b3#3 Multiple baseband signals each having ) and multiple baseband frequencies (f) of the second cell group b1#4 ~f b3#6 The multiple baseband signals (f) of the first cell group are separated into several baseband signals (f) each having their own characteristics. b1#1 ~f b3#3 ) and multiple baseband signals (f b1#4 ~f b3#6 Each of these is branched by multiple signal branching sections 365(1) and 365(2), and the same frequency f is converted by multiple second frequency conversion sections 366(1) to 366(6). (b1) After being converted to a baseband signal, it is filtered through multiple digital filters 367(1) to 367(6).

[0085] Multiple individual baseband signals (f b1#1 ~f b1#3 ,fb1#4 ~f b1#6 Each of these is a service link frequency band (f s1#1 ~f s1#3 ,f s1#4 ~f s1#6 It is converted to the service link frequency band (f s1#1 ~f s1#3 ,f s1#4 ~f s1#6 Each of the multiple downlink signals is converted to a predetermined power by multiple transmitting amplifier sections 380(1) to 380(6), filtered by transmitting filter sections 390(1) to 390(6), and then transmitted from multiple SL antennas 33(1) to 33(6) to each cell 100C(1) to 100C(6). Each cell's terminal device 50(1) to 50(6) receives the service link frequency band (f) transmitted from the relay station slave unit 31. s1#1 ~f s1#3 ,f s1#4 ~f s1#6 Multiple downlink signals are received via multiple antennas 51(1) to 51(6).

[0086] According to the multi-cell non-regenerative wireless relay system 10, which performs wireless relay using a combined frequency multiplexing and MIMO spatial multiplexing configuration as shown in Figures 19 and 20, it is possible to increase the capacity of the feeder link FL between the relay station master unit 21 connected to multiple base station devices 41(1) to 41(6) and the relay station slave units 31 that form multiple cells 100C(1) to 100C(6). Furthermore, compared to conventional non-regenerative relay methods, it is possible to reduce the frequency bandwidth by the number of antennas, and when using the same frequency bandwidth, it is possible to increase the capacity of the line.

[0087] In addition, in the multi-cell non-regenerative wireless relay system 10 shown in Figures 19 and 20, propagation channel information of the feeder link between the relay station master unit 21 and the relay station slave unit 31 (for example, information on the matrix of the propagation path response of the feeder link) may be fed back from the relay station slave unit 31 to the relay station master unit 21, and the signal processing unit 230 of the relay station master unit 21 may use the propagation channel information fed back from the relay station slave unit 31 to control the transmit weight for MIMO spatial multiplexing (for example, calculating the transmit weight and applying it to the transmit signal).

[0088] As described above, the spatial multiplexing multi-cell non-regenerative wireless relay system according to the embodiment of this disclosure makes it possible to increase the capacity of the feeder link FL between the relay station master unit 21 connected to a plurality of base station devices 41 and the relay station slave unit 31 that forms a plurality of cells 100C.

[0089] Furthermore, the spatial multiplexing multicell non-regenerative wireless relay system according to the embodiment of this disclosure can also be applied when the relay station master unit and the relay station slave units are located on land or at sea, respectively.

[0090] Furthermore, the non-regenerative relay wireless relay system disclosed herein can achieve a large capacity feeder link FL between a relay station master unit 21 connected to multiple base station devices 41 and relay station slave units 31 forming multiple cells, thereby contributing to the achievement of Sustainable Development Goal (SDG) 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0091] The processing steps and components of the wireless relay system described herein can be implemented by various means. For example, these steps and components may be implemented in hardware, firmware, software, or a combination thereof.

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

[0093] Furthermore, with respect to the firmware and / or software implementation, means such as processing units used to realize the above-mentioned components may be implemented in the form of a program (e.g., code such as procedures, functions, modules, instructions, etc.) that performs the functions described herein. Generally, any computer / processor-readable medium that clearly embodies the firmware and / or software code may be used to implement means such as processing units used to realize the above-mentioned processes and components as described herein. For example, the firmware and / or software code may be stored in memory in a control device, for example, and executed by a computer or processor. That memory may be implemented inside the computer or processor, or it may be implemented outside the processor. Also, the firmware and / or software code may be stored in a computer or processor-readable medium such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), electrically erasable PROM (EEPROM), flash memory, floppy disks, compact disks (CDs), digital versatile disks (DVDs), magnetic or optical data storage devices, etc. The code may be executed by one or more computers or processors, and the computers or processors may be made to perform functional embodiments as described herein.

[0094] Furthermore, the medium may be a non-temporary recording medium. Also, the program code may be readable and executable by a computer, processor, or other device or machine, and its format is not limited to a specific format. For example, the program code may be source code, object code, or binary code, or it may be a mixture of two or more of these codes.

[0095] Furthermore, the descriptions of embodiments disclosed herein are provided to enable those skilled in the art to manufacture or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the general principles defined herein are applicable to other variations without departing from the spirit or scope of the disclosure. Therefore, the disclosure is not limited to the examples and designs described herein, but should be accepted in the broadest sense that conforms to the principles and novel features disclosed herein. [Explanation of Symbols]

[0096] 10: Wireless relay system 20: Gateway device (GW station) 21: Relay station master unit 22: Antenna for feeder link (GW antenna) 30: High Altitude Platform Station (HAPS: High Altitude Pseudo-Satellite, Stratospheric Platform) 31: Relay station sub-unit 32: Antenna for feeder link (FL antenna) 33: Service link antenna (SL antenna) 34: Spatial Separation Processing Unit 35: Frequency division section 40:Base station 41:Base station equipment 50: Terminal device 51: Antenna 60: Core network device 70: Communication Network 80: Wireless propagation path 100A: Coverage area (service area) 100C: Cell 210: First frequency conversion unit 220: Signal Synthesis Unit 230: Signal Processing Unit 231: Digital Filter 232: Digital Filter 240: Second frequency conversion section 241: Second frequency conversion unit 250: Transmitter Amplifier Section 251: Transmitter Amplifier Section 260: Transmission filter section 261: Transmission 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 point 350: Second frequency conversion unit 360: Signal Processing Unit 361: Digital Filter 362: Signal separation section 363: Digital Filter 364: Signal separation section 365: Signal branching point 366: Second frequency conversion unit 367: Digital Filter 370: Third frequency conversion section 380: Transmitter Amplifier Section 390: Transmission filter section

Claims

1. A non-regenerative relay wireless relay system comprising a relay station master unit and a relay station slave unit, which relays wireless communication 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 the relay station master unit and the relay station slave unit, The relay station master unit has means for transmitting and receiving multiple feeder link signals corresponding to the multiple cells with the relay station slave unit by MIMO (Multiple Input Multiple Output) spatial multiplexing, The relay station slave unit has means for transmitting and receiving a plurality of feeder link signals corresponding to the plurality of cells with the relay station master unit by MIMO spatial multiplexing. A wireless relay system characterized by the following features.

2. In the wireless relay system of claim 1, The aforementioned relay station master unit is A frequency conversion unit that receives multiple downlink signals of the same frequency from the multiple base stations to the multiple cells and converts the frequencies of the multiple downlink signals to a feeder link frequency, It has a plurality of feeder link antennas that each transmit a plurality of feeder link signals having the aforementioned feeder link frequency toward the relay station slave unit, The aforementioned relay station sub-unit is Multiple feeder link antennas that receive the multiple feeder link signals transmitted from the relay station master unit, A signal separation unit applies the MIMO spatial multiplexing transmission model to the wireless propagation path of the feeder link between the relay master unit and the relay slave unit, and separates multiple service link signals to the multiple cells from multiple received signals received via the multiple feeder link antennas. A frequency conversion unit that converts the frequencies of the plurality of service link signals separated by the signal separation unit into a service link frequency, The system includes a plurality of service link antennas, each transmitting a plurality of service link signals having the aforementioned service link frequency toward the plurality of cells, A wireless relay system characterized by the following features.

3. In the wireless relay system of claim 2, The frequency conversion unit of the relay station master unit converts the frequencies of the multiple downlink signals to the same feeder link frequency. Each of the multiple feeder link antennas of the relay station master unit transmits a feeder link signal having the same feeder link frequency toward the relay station slave unit. A wireless relay system characterized by the following features.

4. In the wireless relay system of claim 2, Each of the aforementioned cells is divided into several different cell groups, The frequency conversion unit of the relay station master unit converts the frequencies of the plurality of downlink signals into a plurality of feeder link frequencies that are different from each other for each cell group. Each of the multiple feeder link antennas of the relay station master unit transmits a feeder link signal having a different feeder link frequency to the relay station slave unit. A wireless relay system characterized by the following features.

5. In the wireless relay system of claim 2, The propagation path between the multiple feeder link antennas of the relay station master unit and the multiple feeder link antennas of the relay station slave unit is a line-of-sight (LoS) propagation path. The aforementioned MIMO spatial multiplexing model is a LoS-MIMO spatial multiplexing model. A wireless relay system characterized by the following features.

6. In the wireless relay system of claim 2, The multiple feeder link antennas of the aforementioned relay station master unit are single-polarization antennas or multi-polarization antennas, and at least one of the distance between the antennas and the polarization plane is different. The aforementioned MIMO spatial multiplexing transmission model is a polarization MIMO spatial multiplexing transmission model. A wireless relay system characterized by the following features.

7. In a wireless relay system according to any one of claims 1 to 6, The aforementioned relay station master unit is installed in a gateway device on land or at sea. The aforementioned relay station sub-unit is installed on an aircraft or floating object in the air. A wireless relay system characterized by the following features.

8. In a wireless relay system according to any one of claims 1 to 6, The aforementioned relay station master unit and relay station slave unit are each located on land or at sea. A wireless relay system characterized by the following features.

9. A non-regenerative relay wireless relay method that relays wireless communication between multiple base stations and terminal devices located in multiple cells corresponding to the multiple base stations via a feeder link between a relay station master unit and a relay station slave unit, The relay station master unit transmits and receives multiple feeder link signals corresponding to the multiple cells with the relay station slave unit by MIMO (Multiple Input Multiple Output) spatial multiplexing, The relay station slave unit transmits and receives multiple feeder link signals corresponding to the multiple cells to and from the relay station master unit by MIMO spatial multiplexing, A wireless relay method characterized by including

10. In the wireless relay method of claim 9, The relay station master unit receives multiple downlink signals of the same frequency from the multiple base stations to the multiple cells, and converts the frequencies of the multiple downlink signals to the feeder link frequency. The relay station master unit transmits multiple feeder link signals having the feeder link frequency to each of the relay station slave units via multiple feeder link antennas. The relay station slave unit receives the multiple feeder link signals transmitted from the relay station master unit via multiple feeder link antennas, The relay station slave unit applies the MIMO spatial multiplexing transmission model to the wireless propagation path of the feeder link between the relay master unit and the relay station slave unit, and separates multiple service link signals to the multiple cells from multiple received signals received via the multiple feeder link antennas, The relay station slave unit converts the frequencies of the multiple service link signals to the service link frequency, The relay station slave unit transmits multiple service link signals having the service link frequency to each of the multiple cells via multiple service link antennas, A wireless relay method characterized by including

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