Relay device, communication system, and communication method

Abstract

A relay device according to an embodiment includes a first communication unit, a second communication unit, and a mapping unit. The first communication unit establishes a first feeder link with a first gateway and establishes a second feeder link with a second gateway. The second communication unit establishes a service link with a terminal device belonging to one of a plurality of cells that are each adjacent to at least one cell. The mapping unit associates, with the first gateway, a first plurality of cells among the plurality of cells and associates, with the second gateway, a second plurality of cells different from the first plurality of cells among the plurality of cells.

Description

Relay device, communication system, and communication method

[0001] FIELD Embodiments of the present invention relate to a relay device, a communication system, and a communication method.

[0002] Non-terrestrial networks (NTNs) are being considered as systems to complement terrestrial communication networks. In NTNs, a communication network is constructed that connects terrestrial stations and terminal devices in a multi-layered manner by using mobile objects as relay stations not only on the ground but also at sea, in the air, and in space. For example, satellite communication systems that use satellites as relay stations and high altitude platform stations (HAPS) that fly in the stratosphere as relay stations are known.

[0003] Improvements in communication quality in NTN are being studied. For example, Patent Literature 1 discloses transmitting data to a terminal device while switching communications between a plurality of satellite communication ground stations and a satellite.

[0004] Japanese Patent Application Publication No. 7-20278

[0005] When a satellite is used as a relay station, the distance between the ground stations is sufficient to allow the communication quality between the ground station and the relay station to be considered independent of each other. However, when a HAPS is used as a relay station, the distance between the ground stations may not be sufficient to allow the communication quality between the ground station and the relay station to be considered independent of each other. As a result, when a HAPS is used as a relay station, the site diversity effect may not be as sufficient as when a satellite is used as a relay station. Therefore, there is room for consideration to improve the communication quality in a HAPS system.

[0006] An object of the embodiments of the present invention is to provide a technique for improving communication quality in a HAPS system.

[0007] A relay device according to a first aspect of the present embodiment includes a first communication unit, a second communication unit, and a mapping unit. The first communication unit establishes a first feeder link with a first gateway and establishes a second feeder link with a second gateway. The second communication unit establishes a service link with a terminal device belonging to any of a plurality of cells, each of which is adjacent to at least one cell. The mapping unit associates a first plurality of cells among the plurality of cells with the first gateway and associates a second plurality of cells among the plurality of cells, which are different from the first plurality of cells, with the second gateway.

[0008] In a second aspect of the embodiment, in the relay device described in the first aspect, the mapping unit associates cells of the plurality of cells that are distant from each other as the first plurality of cells with the first gateway, and associates cells of the plurality of cells that are different from the first plurality of cells and distant from each other as the second plurality of cells with the second gateway.

[0009] In a third aspect of the embodiment, in the relay device described in the first aspect, the mapping unit associates cells among the plurality of cells that use a first polarization with the first gateway as the first plurality of cells, and associates cells among the plurality of cells that use a second polarization different from the first polarization with the second gateway as the second plurality of cells.

[0010] In a fourth aspect of the embodiment, in the relay device according to the first aspect, the first communication unit establishes a third feeder link with a third gateway, and the mapping unit associates a third plurality of cells, which are different from the first plurality of cells and the second plurality of cells, with the third gateway.

[0011] In a fifth aspect of the embodiment, in the relay device according to the first aspect, the relay device is configured to stay in the stratosphere.

[0012] In a sixth aspect of the embodiment, in the relay device according to the first aspect, the first plurality of cells includes a first cell and a second cell, the second plurality of cells includes a third cell and a fourth cell, the first feeder link includes a first slot associated with the first cell and a second slot associated with the second cell, and the second feeder link includes a third slot associated with the third cell and a fourth slot associated with the fourth cell.

[0013] In a seventh aspect of the embodiment, in the relay device according to the sixth aspect, the first slot and the second slot are bands that are separated from each other in Q band, Ka band, or V band, and the third slot and the fourth slot are bands that are separated from each other in Q band, Ka band, or V band.

[0014] In an eighth aspect of the embodiment, the relay device described in the first aspect further includes a power amplifier unit that, when the first feeder link is unavailable, increases the transmission power of the service link corresponding to the second plurality of cells more than when the first feeder link is available.

[0015] A communication system of a ninth aspect of the embodiment is a communication system including a relay device according to any one of the first to eighth aspects, the first gateway, and the second gateway.

[0016] In a tenth aspect of the present invention, in the communication system described in the ninth aspect, the first gateway is configured to increase the transmission power of the first feeder link based on a first reception power at the first gateway or a second reception power at the second gateway of a beacon signal from the relay device.

[0017] A communication method of an eleventh aspect of the present embodiment is a communication method comprising: establishing a first feeder link with a first gateway and establishing a second feeder link with a second gateway; establishing a service link with a terminal device belonging to any of a plurality of cells, each of which is adjacent to at least one cell; associating a first plurality of cells among the plurality of cells with the first gateway; and associating a second plurality of cells among the plurality of cells, which are different from the first plurality of cells, with the second gateway.

[0018] According to the embodiment, it is possible to improve the communication quality in a HAPS system.

[0019] FIG. 1 is a schematic diagram showing an example of the configuration of a HAPS system according to an embodiment. FIG. 2 is a block diagram showing an example of the hardware configuration of a gateway constituting the HAPS system according to the embodiment. FIG. 3 is a block diagram showing an example of the hardware configuration of a HAPS constituting the HAPS system according to the embodiment. FIG. 4 is a diagram showing an example of frequencies assigned to an uplink of a feeder link of the HAPS system according to the embodiment. FIG. 5 is a diagram showing an example of frequencies assigned to a downlink of a feeder link of the HAPS system according to the embodiment. FIG. 6 is a diagram showing an example of a service area provided by a service link of the HAPS system according to the embodiment. FIG. 7 is a block diagram showing an example of the functional configuration of a HAPS constituting the HAPS system according to the embodiment. FIG. 8 is a block diagram showing an example of the hardware configuration of a HAPS constituting a HAPS system according to a first modified example. FIG. 9 is a diagram showing an example of a service area provided by a service link of the HAPS system according to the first modified example. FIG. 10 is a block diagram showing an example of the hardware configuration of a gateway constituting a HAPS system according to a second modified example. FIG. 11 is a block diagram showing an example of the hardware configuration of a HAPS constituting the HAPS system according to the second modified example. FIG. 12 is a diagram showing an example of frequencies assigned to an uplink of a feeder link of a HAPS system according to a third modified example. Fig. 13 is a diagram showing an example of frequencies allocated to the downlink of the feeder link of the HAPS system according to the third modification. Fig. 14 is a diagram showing an example of a service area provided by the service link of the HAPS system according to the third modification.

[0020] The embodiments will be described with reference to the drawings. Note that the scale of each part in the drawings used in the following description of the embodiments may be changed as appropriate. Also, for the sake of explanation, the drawings used in the following description of the embodiments may omit components.

[0021] 1. Embodiment 1.1 HAPS System FIG. 1 is a schematic diagram showing an example of the configuration of a HAPS system according to an embodiment.

[0022] The HAPS system 1 includes, for example, gateways 10-1 and 10-2, a HAPS 20, a terminal device UE, and a core network CN. The HAPS system 1 is a non-terrestrial network (NTN) that establishes communication between the core network CN and the terminal device UE via the gateways 10-1 and 10-2 and the HAPS 20.

[0023] The gateways 10-1 and 10-2 are ground stations responsible for communication between the terrestrial core network CN and the airborne HAPS 20. The distance between the gateways 10-1 and 10-2 is shorter than the distance between ground stations in a satellite communication system. The distance between the gateways 10-1 and 10-2 is, for example, at most 100 km. The gateway 10-1 forms a feeder link FL-1 with the HAPS 20. The gateway 10-2 forms a feeder link FL-2 with the HAPS 20. Each of the feeder links FL-1 and FL-2 is composed of a plurality of slots (channels). For the feeder links FL-1 and FL-2, a wideband wave such as the Q band (38 GHz to 39.5 GHz), the Ka band (26 GHz to 40 GHz), or the V band (40 GHz to 75 GHz) is used.

[0024] The HAPS 20 is an unmanned aerial vehicle that flies in the stratosphere (for example, at an altitude of approximately 20 km). The HAPS 20 functions as an aerial relay station that transmits communications between the gateways 10-1 and 10-2 and the terminal devices UE. The HAPS 20 provides the terminal devices UE on the ground with an area (service area SA) in which communication with the HAPS 20 is possible, and establishes a service link SL with the terminal devices UE within the service area SA. For example, the S-band (2 GHz or more and 4 GHz or less), which is the same frequency band as that of terrestrial networks, is used for the service link SL.

[0025] The terminal device UE is, for example, a mobile device such as a smartphone. The terminal device UE in the service area SA can connect to the core network CN either via a route via the HAPS 20 and the gateway 10-1 or via a route via the HAPS 20 and the gateway 10-2 by establishing a service link SL with the HAPS 20.

[0026] 1.2 Hardware Configuration Next, the main hardware configuration of the HAPS system 1 will be described.

[0027] 1.2.1 Gateways The gateways 10-1 and 10-2 have, for example, the same configuration. In the following, when there is no particular distinction between the gateway 10-1 and the gateway 10-2, they will be referred to as "gateway 10."

[0028] 2 is a block diagram showing an example of the hardware configuration of a gateway constituting the HAPS system according to the embodiment. The gateway 10 includes a base station 11, a U / C 12, an HPA 13, an antenna 14, an LNA 15, and a D / C 16.

[0029] The base station 11 is, for example, a next generation node B (gNB) in a fifth generation mobile communication system (5G). The base station 11 includes a CU 111, a DU 112, and an RU 113.

[0030] The CU 111 is a central unit (CU). The CU 111 is responsible for data communication between the base station 11 and the core network CN, and for controlling the DU 112 and the RU 113. The CU 111 also performs radio resource control (RRC) for the terminal device UE.

[0031] The DU 112 is a distribution unit (DU) that performs signal modulation and demodulation, and controls an upper MAC (medium access control) layer.

[0032] The RU 113 is a radio unit (RU) that performs digital-to-analog conversion of signals and controls the lower MAC layer.

[0033] The U / C 12 is an up-converter. When a data-modulated signal is input from the base station 11, the U / C 12 converts the frequency of the signal to a higher frequency such as Q band, Ka band, or V band. The U / C 12 outputs the frequency-converted signal to the HPA 13.

[0034] The HPA 13 is a high power amplifier. The HPA 13 amplifies the output of the signal input from the U / C 12 to a power level that can be received by the HAPS 20. The HPA 13 may further have a filter function. The filter function selectively passes components of the amplified Q-band, Ka-band, or V-band signal in the uplink frequency band of the feeder link FL, and selectively blocks components outside the uplink frequency band of the feeder link FL (for example, the downlink frequency band of the feeder link FL). The HPA 13 outputs the amplified signal to the antenna 14.

[0035] The antenna 14 is, for example, a parabolic antenna. The antenna 14 converts the signal input from the HPA 13 into a radio wave and transmits the radio wave to the HAPS 20. The antenna 14 also receives the radio wave transmitted from the HAPS 20. The antenna 14 converts the received radio wave into a signal and outputs the signal to the LNA 15.

[0036] The LNA 15 is a low noise amplifier that amplifies the output of the signal input from the antenna 14 to a power level at which the signal can be demodulated, while improving the noise characteristics of the signal. The LNA 15 outputs the amplified signal to the D / C 16.

[0037] The D / C 16 is a down-converter. When a signal is input from the LNA 15, the D / C 16 converts the frequency of the signal from a Q-band, a Ka-band, or a V-band frequency to a lower frequency. The D / C 16 outputs the frequency-converted signal to the base station 11.

[0038] 3 is a block diagram showing an example of the hardware configuration of a HAPS constituting a HAPS system according to an embodiment. The HAPS 20 includes an antenna 21, an LNA 22, a D / C 23, an HPA 24, an antenna 25, an LNA 26, a U / C 27, and an HPA 28.

[0039] The antenna 21 is, for example, an omni-antenna. The antenna 21 is configured to simultaneously transmit and receive radio waves to and from the gateways 10-1 and 10-2. The antenna 21 converts the radio waves received from each of the gateways 10-1 and 10-2 into signals and outputs them to the LNA 22. The antenna 21 also converts signals input from the HPA 28 into radio waves and transmits them to the gateways 10-1 and 10-2.

[0040] The LNA 22 is a low noise amplifier that amplifies the output of the signal input from the antenna 21 while improving the noise characteristics of the signal. The LNA 22 outputs the amplified signal to the D / C 23.

[0041] The D / C 23 is a downconverter. When a signal is input from the LNA 22, the D / C 23 converts the frequency of the signal from a Q-band, Ka-band, or V-band frequency to a lower S-band frequency. The D / C 23 outputs the frequency-converted signal to the HPA 24.

[0042] The HPA 24 is a high-power amplifier. The HPA 24 amplifies the output of the signal input from the D / C 23 to a power level that can be received by the terminal device UE. The HPA 24 may further include a filter function. The filter function selectively passes components of the amplified S-band signal in the downlink frequency band of the service link SL and selectively blocks components outside the downlink frequency band of the service link SL (e.g., the uplink frequency band of the service link SL). The HPA 24 outputs the amplified signal to the antenna 25.

[0043] The antenna 25 is, for example, a beamforming antenna such as a multi-element antenna. The antenna 25 converts signals input from the HPA 24 into radio waves and transmits them to the service area SA. Specifically, the antenna 25 performs beamforming to form multiple beams, each of which locally covers a predetermined region (hereinafter referred to as a cell) within the service area SA. The multiple beams are formed in the same frequency band. Furthermore, the cell and the beam irradiated to the cell are associated with one of the multiple slots constituting the feeder link FL.

[0044] The antenna 25 also receives radio waves transmitted from terminal devices UE within the service area SA. The antenna 25 converts the received radio waves into a signal and outputs the signal to the LNA 26.

[0045] The LNA 26 is a low noise amplifier that amplifies the output of the signal input from the antenna 25 while improving the noise characteristics of the signal. The LNA 26 outputs the amplified signal to the U / C 27.

[0046] The U / C 27 is an up-converter. When a signal is input from the LNA 26, the U / C 27 converts the frequency of the signal to a higher frequency such as a Q band, a Ka band, or a V band. The U / C 27 outputs the frequency-converted signal to the HPA 28.

[0047] The HPA 28 is a high-power amplifier. The HPA 28 amplifies the output of the signal input from the U / C 27 to a power level that can be received by the gateway 10. The HPA 28 may further have a filter function. The filter function selectively passes components of the amplified Q-band, Ka-band, or V-band signal in the downlink frequency band of the feeder link FL, and selectively blocks components outside the downlink frequency band of the feeder link FL (for example, the uplink frequency band of the feeder link FL). The HPA 28 outputs the amplified signal to the antenna 21.

[0048] 1.3 Feeder Link Next, the feeder link FL will be described. In the following, a frequency slot <fx, fy> indicates a band equal to or greater than frequency fx and less than frequency fy (fx<fy).

[0049] Fig. 4 is a diagram illustrating an example of frequencies allocated to the uplink of the feeder link of the HAPS system according to the embodiment. Fig. 5 is a diagram illustrating an example of frequencies allocated to the downlink of the feeder link of the HAPS system according to the embodiment. Figs. 4 and 5 illustrate an example of frequency bands allocated to the feeder links FL-1 and FL-2 shown in Fig. 1, respectively.

[0050] 4, in the uplink, the feeder links FL-1 and FL-2 are assigned an uplink band from frequency f0 to frequency f16, for example, a band around 38 GHz.

[0051] In the uplink, each of the feeder links FL-1 and FL-2 is assigned a plurality of non-overlapping frequency slots. The example of Fig. 4 shows a case where eight frequency slots <f0, f1>, <f2, f3>, <f4, f5>, <f6, f7>, <f8, f9>, <f10, f11>, <f12, f13>, and <f14, f15> are assigned to the feeder link FL-1. The example of Fig. 4 shows a case where eight frequency slots <f1, f2>, <f3, f4>, <f5, f6>, <f7, f8>, <f9, f10>, <f11, f12>, <f13, f14>, and <f15, f16> are assigned to the feeder link FL-2.

[0052] The 16 frequency slots <f0, f1> to <f15, f16> allocated to the uplink are respectively associated with cells (described later in FIG. 6) constituting the service area SA. Specifically, the frequency slots <f0, f1>, <f2, f3>, <f4, f5>, <f6, f7>, <f8, f9>, <f10, f11>, <f12, f13>, and <f14, f15> allocated to the feeder link FL-1 are respectively associated with cells A, B, C, D, E, F, G, and H. The frequency slots <f1,f2>, <f3,f4>, <f5,f6>, <f7,f8>, <f9,f10>, <f11,f12>, <f13,f14>, and <f15,f16> assigned to feeder link FL-2 correspond to cells I, J, K, L, M, N, O, and P, respectively.

[0053] 5, in the downlink, the feeder links FL-1 and FL-2 are assigned a downlink band of frequencies equal to or greater than f20 and equal to or less than f36. The downlink band is, for example, a band around 39.5 GHz.

[0054] Similar to the uplink, in the downlink, each of the feeder links FL-1 and FL-2 is assigned a plurality of non-overlapping frequency slots. The example of Fig. 5 shows a case where eight frequency slots <f20, f21>, <f22, f23>, <f24, f25>, <f26, f27>, <f28, f29>, <f30, f31>, <f32, f33>, and <f34, f35> are assigned to the feeder link FL-1. The example of Fig. 5 shows a case where eight frequency slots <f21, f22>, <f23, f24>, <f25, f26>, <f27, f28>, <f29, f30>, <f31, f32>, <f33, f34>, and <f35, f36> are assigned to the feeder link FL-2.

[0055] The 16 frequency slots <f20, f21> to <f35, f36> allocated to the downlink are respectively associated with the cells constituting the service area SA. Specifically, the frequency slots <f20, f21>, <f22, f23>, <f24, f25>, <f26, f27>, <f28, f29>, <f30, f31>, <f32, f33>, and <f34, f35> allocated to the feeder link FL-1 are respectively associated with cells A, B, C, D, E, F, G, and H. The frequency slots <f21, f22>, <f23, f24>, <f25, f26>, <f27, f28>, <f29, f30>, <f31, f32>, <f33, f34>, and <f35, f36> assigned to feeder link FL-2 correspond to cells I, J, K, L, M, N, O, and P, respectively.

[0056] 1.4 Service Link Next, the service link SL will be described.

[0057] Fig. 6 is a diagram showing an example of a service area provided by a service link in a HAPS system according to an embodiment. In the example of Fig. 6, a service area SA is divided into 16 cells A to P described in Figs. 4 and 5 by 16 beams formed by an antenna 25 in a HAPS 20.

[0058] As shown in FIG. 6 , the 16 cells A to P are arranged so that each cell is adjacent to at least one other cell. "Two cells adjacent" means that the two cells are in contact with each other or have an overlapping area. "Two cells not adjacent" or "two cells separated" means that the two cells are not in contact with each other. Note that the example in FIG. 6 shows a case where adjacent cells have an overlapping area, but adjacent cells do not necessarily have to have an overlapping area. Also, while the example in FIG. 6 shows a case where the cell shape is circular, the cell shape can be any shape, such as a regular polygon.

[0059] Cells associated with feeder link FL-1 are arranged so as not to be adjacent to each other. Cells associated with feeder link FL-2 are arranged so as not to be adjacent to each other. In other words, cells associated with feeder link FL-1 are arranged so as to be adjacent to cells associated with a different feeder link (feeder link FL-2 in the example of FIG. 6). Cells associated with feeder link FL-2 are arranged so as to be adjacent to cells associated with a different feeder link (feeder link FL-1 in the example of FIG. 6).

[0060] Specifically, cell A associated with feeder link FL-1 is arranged adjacent to cells I and K associated with feeder link FL-2. Cell B associated with feeder link FL-1 is arranged adjacent to cells I, J, and L associated with feeder link FL-2. Cell C associated with feeder link FL-1 is arranged adjacent to cells I, K, L, and M associated with feeder link FL-2. Cell D associated with feeder link FL-1 is arranged adjacent to cells J, L, and N associated with feeder link FL-2. Cell E associated with feeder link FL-1 is arranged adjacent to cells K, M, and O associated with feeder link FL-2. Cell F associated with feeder link FL-1 is arranged adjacent to cells L, M, N, and P associated with feeder link FL-2. Cell G associated with feeder link FL-1 is arranged adjacent to cells M, O, and P associated with feeder link FL-2. Cell H associated with feeder link FL-1 is arranged adjacent to cells N and P associated with feeder link FL-2.

[0061] The above-described mapping of cells in the service area SA is set in advance in the hardware configuration within the HAPS 20, for example.

[0062] That is, in the forward link, HAPS 20 forms beams toward cells A, B, C, D, E, F, G, and H, respectively, based on signals in frequency slots <f0, f1>, <f2, f3>, <f4, f5>, <f6, f7>, <f8, f9>, <f10, f11>, <f12, f13>, and <f14, f15> received from gateway 10-1 via feeder link FL-1. The HAPS 20 forms beams toward cells I, J, K, L, M, N, O, and P, respectively, based on signals in frequency slots <f1, f2>, <f3, f4>, <f5, f6>, <f7, f8>, <f9, f10>, <f11, f12>, <f13, f14>, and <f15, f16> received from the gateway 10-2 via the feeder link FL-2.

[0063] Also, in the reverse link, HAPS 20 frequency-converts signals received from terminal devices UE located in cells A, B, C, D, E, F, G, and H via service links SL into signals of frequency slots <f20, f21>, <f22, f23>, <f24, f25>, <f26, f27>, <f28, f29>, <f30, f31>, <f32, f33>, and <f34, f35>, respectively, and transmits them to gateway 10-1 via feeder link FL-1. HAPS20 frequency-converts signals received via service links SL from terminal devices UE located in cells I, J, K, L, M, N, O, and P into signals of frequency slots <f21, f22>, <f23, f24>, <f25, f26>, <f27, f28>, <f29, f30>, <f31, f32>, <f33, f34>, and <f35, f36>, respectively, and transmits them to gateway 10-2 via feeder link FL-2.

[0064] 1.5 Functional Configuration Fig. 7 is a block diagram showing an example of the functional configuration of the HAPS 20 constituting the HAPS system according to the embodiment. Fig. 7 shows an example of the functional configuration of the HAPS 20 for realizing the association of the feeder link FL and the service link SL described above.

[0065] As shown in FIG. 7, the HAPS 20 functions as an FL communication unit 31 , a signal processing unit 32 , and an SL communication unit 33 .

[0066] The FL communication unit 31 is a functional block that performs wireless communication via the feeder link FL. The FL communication unit 31 establishes a feeder link FL-1 with the gateway 10-1, and also establishes a feeder link FL-2 with the gateway 10-2. The FL communication unit 31 inputs signals corresponding to the 16 frequency slots <f0, f1> to <f15, f16> received via the feeder links FL-1 and FL-2 to the signal processing unit 32. The FL communication unit 31 distributes the signals corresponding to the 16 frequency slots <f20, f21> to <f35, f36> input from the signal processing unit 32 to the corresponding feeder links FL-1 and FL-2, and transmits them to the gateways 10-1 and 10-2.

[0067] The signal processing unit 32 is a functional block that performs various processes on the signal input from the FL communication unit 31 and outputs the result to the SL communication unit 33, and performs various processes on the signal input from the SL communication unit 33 and outputs the result to the FL communication unit 31. Specifically, the signal processing unit 32 includes a mapping unit 321, a frequency conversion unit 322, and a power amplification unit 323.

[0068] The mapping unit 321 is a functional block that associates frequency slots assigned to the feeder link FL with cells that constitute the service area SA provided by the service link SL. Among the signals input from the FL communication unit 31, the mapping unit 321 associates signals corresponding to frequency slots <f0, f1>, <f1, f2>, ..., and <f15, f16> with the cells A, I, B, J, C, K, D, L, E, M, F, N, G, O, H, and P. Among the signals input from the SL communication unit 33, the mapping unit 321 associates signals received from terminal devices UE located in the cells A, I, B, J, C, K, D, L, E, M, F, N, G, O, H, and P with the frequency slots <f21, f22>, <f22, f23>, ..., and <f35, f36>, respectively.

[0069] The frequency conversion unit 322 is a functional block that performs frequency conversion of signals between the Q band, Ka band, or V band corresponding to the feeder link FL and the S band corresponding to the service link SL. The frequency conversion unit 322 converts the frequency of a signal input from the FL communication unit 31 from the Q band, Ka band, or V band to the S band. The frequency conversion unit 322 converts a signal input from the SL communication unit 33 from the S band to the Q band, Ka band, or V band. When converting the frequency from the S band to the Q band, Ka band, or V band, the frequency conversion unit 322 frequency-converts signals received from terminal devices UE located in cells A, I, B, J, C, K, D, L, E, M, F, N, G, O, H, and P based on the association by the mapping unit 321, so that the signals become signals of frequency slots <f21, f22>, <f22, f23>, ..., and <f35, f36>, respectively.

[0070] The power amplifier 323 is a functional block that compensates for power loss due to signal relay (transmission) by the HAPS 20. The power amplifier 323 amplifies the power of the signal input from the FL communication unit 31 to a power level that can be received by the terminal device UE. The power amplifier 323 amplifies the power of the signal input from the SL communication unit 33 to a power level that can be received by the gateway 10.

[0071] The SL communication unit 33 is a functional block that performs wireless communication via a service link SL. The SL communication unit 33 establishes a service link SL with a terminal device UE located in any one of cells A to P within the service area SA. The SL communication unit 33 inputs a signal corresponding to any one of cells A to P received via the service link SL to the signal processing unit 32. The SL communication unit 33 distributes the signal corresponding to any one of cells A to P input from the signal processing unit 32 to a corresponding beam and transmits it to the corresponding cell.

[0072] 1.6 Effects of the Embodiment According to the embodiment, the FL communication unit 31 establishes a feeder link FL-1 with the gateway 10-1 and a feeder link FL-2 with the gateway 10-2. The SL communication unit 33 establishes a service link SL with a terminal device UE located in one of multiple cells A to P, each of which is adjacent to at least one cell. The mapping unit 321 associates cells A to H, which are distant from each other among the cells A to P, with the gateway 10-1, and associates cells I to P, which are different from cells A to H and distant from each other among the cells A to P, with the gateway 10-2. This prevents all cells from being affected by the line quality of a single feeder link FL. In addition, even if one of the two feeder links FL-1 and FL-2 becomes unavailable due to bad weather or other reasons, the multiple cells associated with the other feeder link FL are distributed throughout the service area SA, so the impact on line quality caused by the unavailable feeder link FL can be leveled across the entire service area SA.

[0073] Additionally, when multiple cells associated with the same feeder link FL are distant from each other, a terminal device UE located in a cell corresponding to an unavailable feeder link FL is more likely to be able to detect beams corresponding to adjacent cells associated with available feeder links FL than when multiple cells associated with the same feeder link FL are adjacent to each other. This makes it possible to avoid a situation where a specific cell becomes difficult to connect to. This makes it possible to improve communication quality in the HAPS system 1.

[0074] Furthermore, a plurality of frequency slots, each of which is a band separated from each other, are assigned to each of the feeder links FL-1 and FL-2. This makes it possible to suppress interference between frequency slots in the same feeder link FL. As a result, it is possible to suppress deterioration of communication quality of the feeder link FL.

[0075] 2. Modifications, etc. Various modifications can be applied to the above embodiment.

[0076] 2.1 First Modification In the above embodiment, the HAPS 20 amplifies the power at a predetermined gain, but this is not limiting. For example, the HAPS 20 may change the gain based on the received power of a signal received via the feeder link FL.

[0077] Fig. 8 is a block diagram showing an example of the hardware configuration of a HAPS constituting a HAPS system according to Modification 1. Fig. 8 corresponds to Fig. 3 in the embodiment.

[0078] As shown in FIG. 8, the HAPS 20 may further include a V-ATT 29 .

[0079] The V-ATT 29 is a variable attenuator. The V-ATT 29 attenuates the output of the signal input from the D / C 23 at a desired attenuation rate. The V-ATT 29 outputs the attenuated signal to the HPA 24.

[0080] For example, if the power of a signal corresponding to one of the feeder links FL-1 and FL-2 among the signals input from the D / C 23 is significantly lower than the power of the signal corresponding to the other, the V-ATT 29 reduces the attenuation rate applied to the lower-power signal below the normal attenuation rate (the attenuation rate applied to the higher-power signal). This enables automatic level control (ALC) that maintains the power of the signal input to the HPA 24 constant regardless of the difference in communication quality between the feeder links FL-1 and FL-2. This makes it possible to prevent the power of the signal transmitted from the antenna 25 from decreasing due to deterioration in the communication quality of the feeder link FL, and to form cells A to P of uniform size as shown in FIG. 6.

[0081] Furthermore, for example, when a signal corresponding to one of the feeder links FL-1 and FL-2 among the signals input from the D / C 23 is unavailable, the V-ATT 29 applies a lower attenuation factor to the other received signal than the normal attenuation factor. This allows the antenna 25 to increase the transmission power of the service link SL to the cell corresponding to the available feeder link FL. Therefore, the cell corresponding to the available feeder link FL among the cells A to P can be made larger than normal.

[0082] Fig. 9 is a diagram showing an example of a service area provided by a service link of a HAPS system according to Modification 1. Fig. 9 shows a case where, among cells A to P mapped in the same manner as in Fig. 6, feeder link FL-2 corresponding to cells I to P is unavailable.

[0083] As shown in Fig. 9, the HAPS 20 increases the transmission power of the service link SL to cells A to H corresponding to the available feeder link FL-1. This allows the cells A to H to cover a wider range than usual. Therefore, most of the area previously covered by cells I to P can be covered by cells A to H. Therefore, even when the feeder link FL-2 is unavailable, deterioration of communication quality in the HAPS system 1 can be suppressed.

[0084] 2.2 Second Modification Furthermore, for example, the gateway 10 may change the power of the signal transmitted to the HAPS 20 based on the quality of the beacon signal from the HAPS 20 .

[0085] Fig. 10 is a block diagram showing an example of the hardware configuration of a gateway constituting a HAPS system according to the second modified example. Fig. 11 is a block diagram showing an example of the hardware configuration of a HAPS constituting a HAPS system according to the second modified example. Figs. 10 and 11 correspond to Figs. 2 and 3 in the embodiment, respectively. For ease of explanation, Fig. 10 also shows the configurations of gateways 10-1 and 10-2.

[0086] 10, each of the gateways 10-1 and 10-2 may further include a BCNR 17 and a V-ATT 18. As shown in FIG.

[0087] The BCNT 30 is a beacon transmitter that transmits a beacon signal to the gateways 10-1 and 10-2 via the antenna 21.

[0088] The BCNR 17 is a beacon receiver. The BCNR 17 receives a beacon signal transmitted from the HAPS 20 via the antenna 14. The BCNR 17 calculates an attenuation rate based on the reception power of the received beacon signal, and outputs the calculated rate to the V-ATT 18 of the gateway of the own station or the gateway of another station.

[0089] The V-ATT 18 is a variable attenuator. The V-ATT 18 attenuates the output of the signal input from the U / C 12 by a desired attenuation factor. The V-ATT 18 outputs the attenuated signal to the HPA 13.

[0090] For example, if the received power of a beacon signal at the gateway 10-2 is significantly lower than normal, the BCNR 17 of the gateway 10-2 calculates an attenuation rate for the V-ATT 18 of the gateway 10-2 that is lower than the normal attenuation rate. The V-ATT 18 of the gateway 10-2 then attenuates the output of the signal input from the U / C 12 by the attenuation rate input from the BCNR 17 of the gateway 10-2. This increases the power of the signal input to the HPA 13 of the gateway 10-2, enabling uplink power control (UPC) to compensate for the communication quality of the feeder link FL-2. This prevents the power of the signal transmitted from the gateway 10-2 from decreasing due to degradation in the communication quality of the feeder link FL-2, and allows cells A to P of uniform size to be formed, as shown in FIG. 6 .

[0091] Furthermore, for example, when the gateway 10-2 cannot receive a beacon signal, the BCNR 17 of the gateway 10-2 calculates an attenuation rate for the V-ATT 18 of the gateway 10-1 that is lower than the normal attenuation rate. The V-ATT 18 of the gateway 10-1 then attenuates the output of the signal input from the U / C 12 by the attenuation rate input from the BCNR 17 of the gateway 10-2. This increases the power of the signal input to the HPA 13 of the gateway 10-1. Therefore, as shown in FIG. 9 , among cells A to P, cells A to H corresponding to the available feeder link FL-1 can be made larger than normal. Therefore, even when the feeder link FL-2 is unavailable, deterioration of communication quality in the HAPS system 1 can be suppressed.

[0092] 2.3 Third Modification In the above embodiment, a case has been described in which, of cells A to P, cells A to H that are distant from one another are associated with gateway 10-1, and cells I to P that are different from cells A to H and distant from one another are associated with gateway 10-2, but this is not limiting. For example, cells that use different polarizations may be associated with gateways 10-1 and 10-2, respectively. In the following, the symbols (⊥) and (∥) represent vertical polarization and horizontal polarization, respectively.

[0093] Fig. 12 is a diagram showing an example of frequencies allocated to the uplink of a feeder link of a HAPS system according to Modification 3. Fig. 13 is a diagram showing an example of frequencies allocated to the downlink of a feeder link of a HAPS system according to Modification 3. Figs. 12 and 13 correspond to Figs. 4 and 5 in the embodiment, respectively.

[0094] 12, in the third modification, in the uplink, 16 vertically polarized frequency slots (⊥)<f0,f1>, (⊥)<f1,f2>, ..., (⊥)<f15,f16> are allocated to the feeder link FL-1, and 16 horizontally polarized frequency slots (∥)<f0,f1>, (∥)<f1,f2>, ..., (∥)<f15,f16> are allocated to the feeder link FL-2.

[0095] In the uplink, the 16 vertically polarized frequency slots (⊥)<f0, f1> to (⊥)<f15, f16> allocated to the feeder link FL-1 are associated with the cells A to P, respectively. The 16 horizontally polarized frequency slots (∥)<f0, f1> to (∥)<f15, f16> allocated to the feeder link FL-2 are associated with the cells Q to AF (described later in FIG. 14).

[0096] 13, in the third modification, in the downlink, 16 horizontally polarized frequency slots (∥)<f20, f21>, (∥)<f2, f22>, ..., (∥)<f35, f36> are allocated to the feeder link FL-1, and 16 vertically polarized frequency slots (⊥)<f20, f21>, (⊥)<f21, f22>, ..., (⊥)<f35, f36> are allocated to the feeder link FL-2.

[0097] In the downlink, the 16 horizontally polarized frequency slots (∥)<f20, f21> to (∥)<f35, f36> allocated to the feeder link FL-1 are associated with the cells A to P, respectively. The 16 vertically polarized frequency slots (⊥)<f20, f21> to (⊥)<f35, f36> allocated to the feeder link FL-2 are associated with the cells Q to AF, respectively.

[0098] Fig. 14 is a diagram showing an example of a service area provided by a service link in a HAPS system according to the third modification. Fig. 14 corresponds to Fig. 6 in the embodiment. The example of Fig. 14 shows a case where the service area SA is divided into 32 cells A to P described in Figs. 12 and 13.

[0099] 14, 16 cells A to P are respectively arranged in the same positions as 16 cells Q to AF. The 16 cells A to P are cells that use right-hand circular polarization (RHCP) among the beams formed by antenna 25 in HAPS 20. The 16 cells Q to AF are cells that use left-hand circular polarization (LHCP) among the beams formed by antenna 25 in HAPS 20.

[0100] In this way, by associating cells using different polarizations with different gateways 10, the areas that can be covered by gateway 10-1 and gateway 10-2 can be made substantially equivalent. Therefore, even if one of feeder links FL-1 and FL-2 becomes unavailable, the coverage of the service area SA can be prevented from being affected. Furthermore, by configuring the slots of the feeder link FL by a combination of frequency and polarization, it is possible to suppress a decrease in the frequency band that can be used per slot due to an increase in the number of slots.

[0101] 2.4 Others In the above embodiment, the gateway 10 includes one base station 11, but this is not limiting. For example, the gateway 10 may include multiple base stations 11. In this case, each of the multiple base stations 11 may be associated with multiple frequency slots assigned to the gateway 10 to which the multiple base stations 11 belong. In other words, the number of base stations 11 included in a certain gateway 10 may correspond to the number of frequency slots assigned to the gateway 10.

[0102] In the above embodiment, a case has been described in which two gateways 10-1 and 10-2 establish feeder links FL-1 and FL-2, respectively, with the HAPS 20, but this is not limiting. For example, the HAPS 20 may establish feeder links FL with any number of gateways 10 greater than or equal to two. In this case, among the multiple cells constituting the service area SA, multiple cells associated with the same gateway are arranged so as to be spaced apart from each other. As a result, even when the number of gateways is three or more, the impact on line quality due to unavailable feeder links FL can be leveled across the entire service area SA, as in the embodiment.

[0103] In the above embodiment, the HAPS 20 associates the gateways 10-1 and 10-2 with the cells A to P using a preset fixed mapping pattern. However, this is not limiting. For example, the HAPS 20 may store multiple mapping patterns and change the mapping pattern in response to instructions from the gateway 10. Specifically, for example, when the HAPS 20 has established a feeder link FL with three or more gateways 10, the HAPS 20 may change the mapping pattern while maintaining an arrangement in which cells corresponding to the same gateway are not adjacent to each other, so that the optimal set of gateways 10 is associated with the cells A to P according to the area in which the HAPS 20 flies. Furthermore, for example, when the line quality of the feeder link FL-1 deteriorates, the HAPS 20 may cooperate with the gateway 10 to change the mapping pattern from the one shown in FIG. 6 to one that associates all of the cells A to P with the gateway 10-2. This makes it possible to provide the terminal device UE with more stable line quality. Note that the gateway 10 that has been released from its association with the cell may temporarily suspend its communication function with the HAPS 20. This allows the power consumption in the gateway 10 to be reduced.

[0104] In the above embodiment, the HAPS 20 and the gateway 10 change the amplification factor of signals during transmission and reception of the feeder link FL in order to maintain line quality. However, this is not limiting. For example, the gateway 10 may further change the modulation method of the feeder link FL.

[0105] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention.

[0106] 1...HAPS system, 10-1, 10-2...gateway, 11...base station, 12, 27...U / C, 13, 24, 28...HPA, 14, 21, 25...antenna, 15, 22, 26...LNA, 16, 23...D / C, 17...BCNR, 18, 29...V-ATT, 30...BCNT, 31...FL communication unit, 32...signal processing unit, 33...SL communication unit, 111...CU, 112...DU, 113...RU, 321...mapping unit, 322...frequency conversion unit, 323...power amplification unit 323, FL-1, FL-2...feeder link, SL...service link, UE...terminal device, SA...service area, CN...core network.

Claims

1. A relay device comprising: a first communication unit that establishes a first feeder link with a first gateway and a second feeder link with a second gateway; a second communication unit that establishes a service link with a terminal device that belongs to one of a plurality of cells, each of which is adjacent to at least one cell; and a mapping unit that associates a first plurality of cells among the plurality of cells with the first gateway and associates a second plurality of cells among the plurality of cells, which are different from the first plurality of cells, with the second gateway.

2. The relay device according to claim 1, wherein the mapping unit associates cells among the plurality of cells that are distant from one another as the first plurality of cells with the first gateway, and associates cells among the plurality of cells that are different from the first plurality of cells and distant from one another as the second plurality of cells with the second gateway.

3. The relay device according to claim 1, wherein the mapping unit associates cells among the plurality of cells that use a first polarization with the first gateway as the first plurality of cells, and associates cells among the plurality of cells that use a second polarization different from the first polarization with the second gateway as the second plurality of cells.

4. The relay device according to claim 1, wherein the first communication unit establishes a third feeder link with a third gateway, and the mapping unit associates a third plurality of cells among the plurality of cells, which are different from the first plurality of cells and the second plurality of cells, with the third gateway.

5. The relay device according to claim 1, wherein the relay device is configured to stay in the stratosphere.

6. The relay device of claim 1, wherein the first plurality of cells includes a first cell and a second cell, the second plurality of cells includes a third cell and a fourth cell, the first feeder link includes a first slot associated with the first cell and a second slot associated with the second cell, and the second feeder link includes a third slot associated with the third cell and a fourth slot associated with the fourth cell.

7. The repeater device according to claim 6, wherein the first slot and the second slot are bands separated from each other in the Q band, the Ka band, or the V band, and the third slot and the fourth slot are bands separated from each other in the Q band, the Ka band, or the V band.

8. The relay device according to claim 1, further comprising a power amplifier that, when the first feeder link is unavailable, increases the transmission power of the service link corresponding to the second plurality of cells more than when the first feeder link is available.

9. A communication system comprising: a relay device according to any one of claims 1 to 8; the first gateway; and the second gateway.

10. The communication system according to claim 9, wherein the first gateway is configured to increase the transmission power of the first feeder link based on a first reception power at the first gateway or a second reception power at the second gateway of a beacon signal from the relay device.

11. A communication method for a relay device, comprising: establishing a first feeder link with a first gateway and establishing a second feeder link with a second gateway; establishing a service link with a terminal device belonging to any of a plurality of cells, each of which is adjacent to at least one cell; associating a first plurality of cells among the plurality of cells with the first gateway, and associating a second plurality of cells among the plurality of cells, which are different from the first plurality of cells, with the second gateway.

Images