Power control device, gateway, and power control method

Abstract

A power control device according to an embodiment is included in a gateway that establishes a feeder link with a relay device staying in the stratosphere. The power control device comprises: a first acquisition unit that acquires airframe information including a position and attitude of the relay device notified from the relay device without using the feeder link; a second acquisition unit that acquires rainfall information including an amount of rainfall over a propagation path of the feeder link on the basis of the airframe information; a third acquisition unit that acquires, on the basis of the airframe information, cloud information including at least one information item selected from the presence or absence of cloud over the propagation path of the feeder link, a type of cloud, a thickness of the cloud, and water vapor amount; an estimation unit that estimates, on the basis of the airframe information, the rainfall information, and the cloud information, at least one loss selected in a prescribed order from a variation amount of free-space path loss, a variation amount of gain, a rain attenuation amount, and a cloud attenuation amount, occurring in the feeder link; and a determination unit that determines, on the basis of the at least one loss that has been estimated, a control amount of uplink transmission power of the feeder link at a predetermined cycle.

Description

Power control device, gateway, and power control method

[0001] Embodiments of the present invention relate to a power control device, a gateway, and a power control method.

[0002] As a system for supplementing a terrestrial communication network, a non-terrestrial network (NTN: non-terrestrial network) is being considered. In NTN, in addition to the ground, by using mobile bodies as relay stations over the sea, air, and space, a communication network that multilaterally connects a terrestrial station and a terminal device is constructed. For example, a satellite communication system using a satellite as a relay station and a HAPS system using a high altitude platform station (HAPS: high altitude platform station) flying in the stratosphere as a relay station are known.

[0003] Improvement of communication quality in an uplink feeder link from a terrestrial station to a HAPS is being considered. For example, Patent Document 1 discloses that a gateway receives a downlink reference signal from a satellite as a beacon signal for a closed loop, and increases the uplink feeder link power in response to loss of the feeder link due to rainfall or the like.

[0004] Japanese Patent Application Laid-Open No. 9-8719

[0005] However, due to limitations in generated power and mounting weight, a HAPS may sometimes have difficulty mounting a device for transmitting a beacon signal for a closed loop as described above. In this case, it is preferable that the terrestrial station can perform power control without forming a closed loop with the HAPS.

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

[0007] The power control device according to the embodiment is a power control device provided in a gateway that establishes a feeder link with a relay device staying in the air or space for communication with a ground terminal device, and comprises: a first acquisition unit that acquires aircraft information including the position and attitude of the relay device which is reported from the relay device without using the feeder link; a second acquisition unit that acquires rainfall information including the amount of rainfall on the propagation path of the feeder link based on the aircraft information; a third acquisition unit that acquires cloud information including at least one piece of information selected from the presence or absence of clouds, the type of cloud, the thickness of the cloud, and the amount of water vapor on the propagation path of the feeder link based on the aircraft information; an estimation unit that estimates at least one loss selected in a predetermined order from the amount of free-space loss fluctuation, the amount of gain fluctuation, the amount of rainfall attenuation, and the amount of cloud attenuation occurring in the feeder link based on the aircraft information, the rainfall information, and the cloud information; and a determination unit that determines the amount of control of the transmission power of the uplink of the feeder link at a predetermined period based on the estimated at least one loss.

[0008] According to this embodiment, the quality of communication from the ground station to HAPS can be improved.

[0009] Figure 1 is a schematic diagram showing an example of the configuration of a HAPS system according to the embodiment. Figure 2 is a block diagram showing an example of the hardware configuration of a gateway constituting the HAPS system according to the embodiment. Figure 3 is a block diagram showing an example of the hardware configuration of HAPS constituting the HAPS system according to the embodiment. Figure 4 is a block diagram showing an example of the hardware configuration of the power control device of the gateway according to the embodiment. Figure 5 is a block diagram showing an example of the functional configuration of the power control device of the gateway according to the embodiment. Figure 6 is a flowchart showing an example of the control amount determination process in the power control device according to the embodiment. Figure 7 is a diagram showing an example of the magnitude of loss estimated by the power control device according to the embodiment.

[0010] Embodiments will be described with reference to drawings. Note that the scale of the parts in the drawings used in the following description of embodiments may have been appropriately changed. Also, for illustrative purposes, some components may be omitted from the drawings used in the following description of embodiments.

[0011] 1. Configuration 1.1 HAPS System Figure 1 is a schematic diagram showing an example of the configuration of the HAPS system according to the embodiment.

[0012] The HAPS system 1 includes, for example, a gateway 10, HAPS 20, terminal equipment 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 equipment UE via the gateway 10 and HAPS 20.

[0013] Gateway 10 is a ground station responsible for communication between the ground-based core network CN and the airborne HAPS 20. Gateway 10 forms a feeder link FL with HAPS 20. The feeder link FL is composed of multiple slots (channels). Broadband waves such as the Q band (38 GHz to 39.5 GHz), Ka band (26 GHz to 40 GHz), or V band (40 GHz to 75 GHz) are used for the feeder link FL.

[0014] HAPS20 is an unmanned aerial vehicle that flies in the stratosphere (for example, at an altitude of approximately 20 km). HAPS20 functions as an upper-air relay station that transmits communication between Gateway 10 and Terminal Equipment UE. HAPS20 provides a communication area (service area SA) to the ground-based Terminal Equipment UE and establishes a service link SL between itself and the Terminal Equipment UE within the service area SA. For the service link SL, for example, the S-band (2 GHz to 4 GHz), which is the same frequency band as the ground network, is used.

[0015] The terminal device UE is, for example, a mobile device such as a smartphone. The terminal device UE within the service area SA can connect to the core network CN by establishing a service link SL with the HAPS 20, and then via a communication path (i.e., service link SL and feeder link FL) through the HAPS 20 and gateway 10.

[0016] 1.2 Gateway Next, the main configuration of gateway 10 will be described.

[0017] Figure 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, a V-ATT 13, an HPA 14, an antenna 15, an LNA 16, a D / C 17, and a power control device 18.

[0018] Base station 11 is, for example, a gNB (next generation node B) in a fifth-generation mobile communication system (5G). Base station 11 includes CU 111, DU 112, and RU 113.

[0019] CU111 is the CU (central unit). CU111 is responsible for data communication between the base station 11 and the core network CN, as well as controlling DU112 and RU113. CU111 also performs resource management (RRC: radio resource control) for the terminal device UE.

[0020] DU112 is a distribution unit (DU). DU112 performs signal modulation and demodulation, as well as control of the higher MAC (medium access control) layer.

[0021] RU113 is a radio unit (RU). RU113 performs digital-to-analog signal conversion and controls the lower MAC layer, among other functions.

[0022] U / C12 is an up-converter. When U / C12 receives a data-modulated signal from base station 11, it converts the frequency of the signal to a higher frequency, such as the Q-band, Ka-band, or V-band. U / C12 outputs the frequency-converted signal to V-ATT13.

[0023] The V-ATT 13 is a variable attenuator. The V-ATT 13 attenuates the output of the signal input from the U / C 12 by an arbitrary attenuation rate. The attenuation rate is controlled based on a control variable determined by the power control device 18. The V-ATT 13 outputs the attenuated signal to the HPA 14.

[0024] HPA14 is a high-power amplifier. HPA14 amplifies the output of the signal input from V-ATT13 to a power level that can be received by HAPS20. HPA14 may also have a filtering function. The filtering function selectively passes the components of the amplified Q-band, Ka-band, or V-band signal within the uplink frequency band of the feeder link FL, while selectively blocking components outside the uplink frequency band of the feeder link FL (for example, the downlink frequency band of the feeder link FL). HPA14 outputs the amplified signal to antenna 15.

[0025] Antenna 15 is, for example, a parabolic antenna. Antenna 15 converts the signal input from HPA 14 into radio waves and transmits it to HAPS 20. Antenna 15 receives radio waves transmitted from HAPS 20. Antenna 15 converts the received radio waves into a signal and outputs it to LNA 16. Tracking of HAPS 20 by antenna 15 is performed based on the aircraft information of HAPS 20 obtained using ADS-B, which will be described later. In other words, the tracking of HAPS 20 by antenna 15 is performed using an open-loop tracking method, which is different from a closed-loop tracking method that performs peak search using an algorithm that maximizes the reception level of the signal received by antenna 15 from HAPS 20.

[0026] The LNA 16 is a low-noise amplifier. The LNA 16 amplifies the output of the signal input from the antenna 15 to a demodulatorable power level while improving the noise characteristics of the signal. The LNA 16 outputs the amplified signal to the D / C 17.

[0027] D / C17 is a down-converter. When a signal is input from LNA16, D / C17 converts the frequency of the signal from the Q-band, Ka-band, or V-band to a lower frequency. D / C17 outputs the frequency-converted signal to base station 11.

[0028] The power control device 18 is, for example, an information processing device such as a PC (personal computer) or a data server. The power control device 18 is configured to perform a control amount determination process that determines the amount of power to be transmitted to the HAPS 20 in communication with the HAPS 20 via the antenna 15. The control amount determination process is an open-loop process that determines the amount of power to be transmitted from the HAPS 20 without receiving a feedback signal via the antenna 15. The power control device 18 repeatedly performs the control amount determination process at a predetermined update cycle and updates the control amount in real time. The update cycle may be, for example, one second or less. The power control device 18 operates the V-ATT 13 based on the attenuation rate determined by the control amount. Details of the configuration of the power control device 18 will be described later.

[0029] 1.3 HAPS Figure 3 is a block diagram showing an example of the hardware configuration of HAPS constituting the HAPS system according to the embodiment. HAPS20 includes antenna 21, LNA22, D / C23, HPA24, antenna 25, LNA26, U / C27, and HPA28.

[0030] Antenna 21 is, for example, an omnidirectional antenna. Antenna 21 is configured to send and receive radio waves to and from gateway 10. Antenna 21 converts the radio waves received from gateway 10 into a signal and outputs it to LNA 22. Antenna 21 also converts the signal input from HPA 28 into a radio wave and transmits it to gateway 10.

[0031] The LNA22 is a low-noise amplifier. The LNA22 amplifies the output of the signal input from the antenna 21 while improving the noise characteristics of the signal. The LNA22 outputs the amplified signal to the D / C23.

[0032] D / C23 is a downconverter. When a signal is input from LNA22, D / C23 converts the frequency of the signal from a Q-band, Ka-band, or V-band frequency to a lower S-band frequency. D / C23 outputs the frequency-converted signal to HPA24.

[0033] HPA24 is a high-power amplifier. HPA24 amplifies the output of the signal input from D / C23 to a power level that can be received by the terminal device UE. HPA24 may also be equipped with a filtering function. The filtering function selectively passes the component of the amplified S-band signal within the downlink frequency band of the service link SL, while selectively blocking the component outside the downlink frequency band of the service link SL (for example, the uplink frequency band of the service link SL). HPA24 outputs the amplified signal to antenna 25.

[0034] Antenna 25 is, for example, a beamforming antenna such as a multi-element antenna. Antenna 25 converts the signal input from HPA 24 into radio waves and transmits them to the service area SA. Specifically, by beamforming, antenna 25 forms multiple beams, each locally covering a predetermined area (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 onto the cell are associated with one of the multiple slots that constitute the feeder link FL.

[0035] Furthermore, antenna 25 receives radio waves transmitted from terminal equipment UE within the service area SA. Antenna 25 converts the received radio waves into a signal and outputs it to LNA 26.

[0036] LNA26 is a low-noise amplifier. LNA26 amplifies the output of the signal input from antenna 25 while improving the noise characteristics of the signal. LNA26 outputs the amplified signal to U / C27.

[0037] U / C27 is an upconverter. When a signal is input from LNA26, U / C27 converts the frequency of the signal to a higher frequency, such as the Q band, Ka band, or V band. U / C27 outputs the frequency-converted signal to HPA28.

[0038] The HPA28 is a high-power amplifier. The HPA28 amplifies the output of the signal input from the U / C27 to a power level that can be received at the gateway 10. The HPA28 may also be equipped with a filtering function. The filtering function selectively passes the components of the amplified Q-band, Ka-band, or V-band signal within the downlink frequency band of the feeder link FL, while selectively blocking components outside the downlink frequency band of the feeder link FL (for example, the uplink frequency band of the feeder link FL). The HPA28 outputs the amplified signal to the antenna 21.

[0039] In addition to the configuration shown in Figure 3, HAPS20 may also be equipped with, for example, an ADS-B (automatic dependent surveillance - broadcast) device, which is not shown. HAPS20 uses the ADS-B device to broadcast aircraft information, including its own position, speed, and attitude, at short intervals, such as a 1-second cycle. The ADS-B device generates aircraft information, for example, by utilizing a GNSS (global navigation satellite system). That is, the aircraft information of HAPS20 is broadcast independently of the feeder link FL established between it and the gateway 10.

[0040] 1.4 Power Control Device Figure 4 is a block diagram showing an example of the hardware configuration of the power control device of the gateway according to the embodiment.

[0041] As shown in Figure 4, the power control device 18 includes, for example, a control circuit 31, storage 32, a communication module 33, an interface 34, a drive 35, and a storage medium 36.

[0042] The control circuit 31 is a circuit that overall controls each component of the power control device 18. The control circuit 31 includes a CPU (central processing unit), a RAM (random access memory), a ROM (read only memory), and the like. The CPU of the control circuit 31 controls the entire power control device 18 according to a program stored in the ROM of the control circuit 31. The RAM of the control circuit 31 has a working area for the CPU of the control circuit 31. The ROM of the control circuit 31 stores programs and the like used by the power control device 18.

[0043] The storage 32 includes, for example, an HDD (hard disk drive) or an SSD (solid state drive). The storage 32 stores information used in the control amount determination process by the power control device 18.

[0044] The communication module 33 is a circuit used for sending and receiving data between the power control device 18 and a network (not shown). The power control device 18 can acquire various information from the network via the communication module 33.

[0045] The interface 34 is an interface that controls communication with an administrator (not shown) of the power control device 18. The interface 34 includes an input device and an output device. The input device includes, for example, a keyboard, a touch panel, and operation buttons. The output device includes, for example, an LCD (liquid crystal display) or an EL (electroluminescence) display, a printer, and the like.

[0046] The drive 35 is a device for reading software stored in the storage medium 36. The drive 35 includes, for example, a CD (compact disk) drive or a DVD (digital versatile disk) drive.

[0047] The storage medium 36 is a medium that stores software by means of an electrical, magnetic, optical, mechanical, or chemical action. The storage medium 36 may store a program used by the power control device 18.

[0048] FIG. 5 is a block diagram showing an example of the functional configuration of the power control device of the gateway according to the embodiment.

[0049] As shown in FIG. 5, the storage 32 of the power control device 18 stores nominal data 41. Further, the control circuit 31 of the power control device 18 functions as a computer including an aircraft information acquisition unit 42, a rainfall information acquisition unit 43, a cloud information acquisition unit 44, a loss estimation unit 45, and a control amount determination unit 46.

[0050] The nominal data 41 is, for example, information regarding the flight plan of the HAPS 20. Specifically, for example, the nominal data 41 includes the history of time, position, speed, and attitude, etc. in the sky where the HAPS 20 is scheduled to fly. Based on the nominal data 41, the loss estimation unit 45 can estimate the free space loss and the value of the antenna gain in an ideal flight state. Note that the nominal data 41 is not limited to the time history of the position, speed, and attitude of the HAPS 20, and may be fixed values (for example, average values) of the position, speed, and attitude of the HAPS 20.

[0051] The aircraft information acquisition unit 42 is, for example, an ADS - B receiver. The aircraft information acquisition unit 42 acquires the aircraft information notified from the HAPS 20. The reception frequency of the aircraft information is, for example, 1090 MHz. The reception frequency of the aircraft information is an inappropriate frequency as the frequency of the transmission signal used for the uplink of the feeder link FL and the reference signal used for tracking the HAPS 20. The aircraft information acquisition unit 42 outputs the acquired aircraft information to the rainfall information acquisition unit 43, the cloud information acquisition unit 44, and the loss estimation unit 45.

[0052] The rainfall information acquisition unit 43 acquires rainfall information on the straight line connecting the gateway 10 and the HAPS 20 (i.e., the propagation path of the feeder link FL) based on the aircraft information. Specifically, for example, the rainfall information acquisition unit 43 identifies a set of meshes on a map (for example, a predetermined area delimited by latitude and longitude) through which the straight line connecting the gateway 10 and the HAPS 20 passes, based on the aircraft information. Then, the rainfall information acquisition unit 43 accesses a database of rainfall information showing actual or predicted rainfall amounts via an external network and acquires rainfall information corresponding to the identified set of meshes. The rainfall information acquisition unit 43 outputs the acquired rainfall information to the loss estimation unit 45.

[0053] The source of rainfall information is not limited to, but includes high-resolution precipitation nowcast data provided by the Japan Meteorological Agency. For example, if Gateway 10 and HAPS 20 are located outside of Japan, the rainfall information acquisition unit 43 may be configured to access a database that replaces the high-resolution precipitation nowcast data. The rainfall information acquisition unit 43 may also be configured to acquire information from rain gauges located in each mesh.

[0054] The cloud information acquisition unit 44 acquires cloud information on the straight line connecting the gateway 10 and HAPS 20 (i.e., the propagation path of the feeder link FL) based on the aircraft information. Specifically, for example, the cloud information acquisition unit 44 identifies the direction (e.g., a pair of azimuth and elevation angles) connecting the gateway 10 and HAPS 20 based on the aircraft information. Then, the cloud information acquisition unit 44 accesses a database of cloud information showing actual or predicted conditions via an external network and acquires cloud information corresponding to the identified mesh set. The cloud information includes, for example, at least one piece of information selected from the presence or absence of clouds, cloud type, cloud thickness, and water vapor content. Methods for acquiring cloud information include, for example, a method of determining the cloud type and thickness using a 360-degree camera, or a method of using equipment to measure the amount of water vapor in the air. The cloud information acquisition unit 44 outputs the acquired cloud information to the loss estimation unit 45.

[0055] The loss estimation unit 45 estimates the change from the predicted value of the loss that the power of the transmitted signal from the gateway 10 will experience until it is received by the HAPS 20, based on nominal data 41, aircraft information, rainfall information, and cloud information. The loss estimation unit 45 outputs the estimated change from the predicted value of the loss to the control variable determination unit 46. Specifically, the loss estimation unit 45 includes a free-space loss fluctuation estimation unit 51, a gain fluctuation estimation unit 52, a rainfall attenuation estimation unit 53, a cloud attenuation estimation unit 54, and an estimation processing control unit 55.

[0056] In the following, the various loss values ​​calculated based on the planned trajectory corresponding to nominal data 41 will also be referred to as nominal values. Furthermore, the various loss values ​​calculated based on the HAPS 20 aircraft information obtained from ADS-B, etc., will also be referred to as observed values.

[0057] The free-space loss fluctuation estimation unit 51 calculates the nominal value and observed value of the free-space loss based on the nominal data 41 and the aircraft information, respectively. The free-space loss fluctuation estimation unit 51 estimates the difference between the calculated nominal value and the observed value of the free-space loss as the free-space loss fluctuation amount X. The free-space loss fluctuation estimation unit 51 outputs the estimated free-space loss fluctuation amount X to the control variable determination unit 46.

[0058] The gain fluctuation estimation unit 52 calculates the nominal value and observed value of the antenna gain in the direction of the gateway 10 in the HAPS 20, based on the nominal data 41 and the aircraft information. Specifically, for example, the gain fluctuation estimation unit 52 calculates the depression angle when viewing the gateway 10 from the antenna 21 of the HAPS 20, and calculates the antenna gain at that depression angle by referring to the antenna pattern of the antenna 21. The gain fluctuation estimation unit 52 estimates the difference between the calculated nominal value and the observed value of the antenna gain as the gain fluctuation amount Z. The gain fluctuation estimation unit 52 outputs the estimated gain fluctuation amount Z to the control amount determination unit 46.

[0059] The rainfall attenuation estimation unit 53 determines, based on rainfall information, whether or not rainfall is occurring on the propagation path between the gateway 10 and HAPS 20. If no rainfall is occurring on the propagation path, the rainfall attenuation estimation unit 53 estimates that there is no attenuation due to rainfall. If rainfall is occurring on the propagation path, the rainfall attenuation estimation unit 53 estimates the rainfall attenuation Y, taking into account the amount of rainfall at each mesh on the propagation path. Specifically, for example, the rainfall attenuation estimation unit 53 estimates the rainfall attenuation Y based on ITU-R (International Telecommunication Union - Radiocommunication) Recommendations P. 618 and P. 838. The rainfall attenuation estimation unit 53 outputs the estimated rainfall attenuation Y to the control amount determination unit 46. This improves the estimation accuracy compared to estimating the rainfall attenuation solely from information from the rainfall observation device installed on the gateway 10. Specifically, for example, when estimating rainfall attenuation solely from information from a rainfall observation device installed at gateway 10, the rainfall attenuation is estimated by assuming a uniform rainfall situation along the propagation path based on the rainfall intensity at the observation point. In contrast, according to this embodiment, by estimating the rainfall attenuation Y, which takes into account the amount of rainfall at each mesh along the propagation path, more accurate estimation becomes possible. Furthermore, when estimating rainfall attenuation solely from information from a rainfall observation device installed at gateway 10, if heavy rainfall occurs along the propagation path when no rainfall is observed at gateway 10, there is a possibility of confusing the rainfall loss with the loss due to the displacement of the antenna 15 of gateway 10. In contrast, according to this embodiment, by estimating the rainfall attenuation Y, which takes into account the amount of rainfall at each mesh along the propagation path, such confusion can be suppressed. Moreover, according to this embodiment, since there is no need to install individual rainfall observation devices at gateway 10, equipment costs can be reduced.

[0060] The cloud attenuation estimation unit 54 estimates the cloud attenuation S based on cloud information, taking into account at least one piece of information selected from the presence or absence of clouds on the propagation path between the gateway 10 and HAPS 20, the type of cloud, the thickness of the cloud, and the amount of water vapor. Specifically, for example, the cloud attenuation estimation unit 54 estimates the cloud attenuation S based on ITU-R Recommendation P. 618. The cloud attenuation estimation unit 54 outputs the estimated cloud attenuation S to the control amount determination unit 46.

[0061] The estimation processing control unit 55 estimates the processing time required for each of the estimation processes for the free-space loss fluctuation X, gain fluctuation Z, rainfall attenuation Y, and cloud attenuation S. Based on the estimated processing time, the estimation processing control unit 55 selects the estimation processes to be executed within the period allocated to the estimation process. Specifically, when a Q-band is used for the feeder link FL, the estimation processing control unit 55 controls the process so that the estimation processes are executed in the order of rainfall attenuation Y, cloud attenuation S, free-space loss fluctuation X, and gain fluctuation Z. As a result, the estimation processing control unit 55 causes the rainfall attenuation estimation unit 53 to prioritize the estimation of rainfall attenuation Y during the period allocated to the estimation process. In the remaining time after the estimation of rainfall attenuation Y, the estimation processing control unit 55 causes the cloud attenuation estimation unit 54 to prioritize the estimation of cloud attenuation S. In the remaining time after the estimation of cloud attenuation S, the estimation processing control unit 55 causes the free-space loss fluctuation estimation unit 51 to prioritize the estimation of free-space loss fluctuation X. The estimation processing control unit 55 causes the gain fluctuation estimation unit 52 to estimate the gain fluctuation amount Z during the remaining time after estimating the free-space loss fluctuation amount X. The period allocated to the estimation process is set to be less than or equal to the update cycle of the controlled variable.

[0062] The control amount determination unit 46 determines the control amount of the transmitted power to be applied to the control cycle corresponding to the period, based on the values ​​output from the loss estimation unit 45 within the period allocated for estimation processing, among the free-space loss fluctuation amount X, gain fluctuation amount Z, rainfall attenuation amount Y, and cloud attenuation amount S. Specifically, the control amount determination unit 46 calculates the sum of the values ​​output from the loss estimation unit 45 as the total attenuation from the nominal value of the power of the transmitted signal from the gateway 10 to the HAPS 20. The control amount determination unit 46 outputs the calculated total attenuation to the V-ATT 13 as the control amount to be compensated. 2. Operation diagram 6 is a flowchart showing an example of the control amount determination process in the power device according to the embodiment. The control amount determination process shown in Figure 6 corresponds to the control amount determination process for one update cycle.

[0063] As shown in Figure 6, once the update of the control quantity by the previous control quantity determination process is completed (start), the aircraft information acquisition unit 42 acquires aircraft information based on ADS-B from HAPS 20 (S1).

[0064] The rainfall information acquisition unit 43 and the cloud information acquisition unit 44 acquire rainfall information and cloud information, respectively, based on the aircraft information acquired in the processing of S1 (S2). Specifically, the rainfall information acquisition unit 43 acquires information on the amount of rainfall in each of the corresponding mesh sets on the propagation path of the feeder link FL between the gateway 10 and the HAPS 20. The cloud information acquisition unit 44 acquires at least one piece of information selected from the presence or absence of clouds, the type of cloud, the thickness of the cloud, and the amount of water vapor on the propagation path of the feeder link FL between the gateway 10 and the HAPS 20.

[0065] In the processing of S3 to S9, the loss estimation unit 45 estimates the free-space loss fluctuation X, gain fluctuation Z, rainfall attenuation Y, and cloud attenuation S based on the nominal data 41, the aircraft information obtained in the processing of S1, and the rainfall information and cloud information obtained in the processing of S2.

[0066] Specifically, the estimation processing control unit 55 causes the rainfall attenuation estimation unit 53 to prioritize the estimation process of the rainfall attenuation amount Y. The rainfall attenuation estimation unit 53 estimates the rainfall attenuation amount Y based on the aircraft information and the rainfall information (S3).

[0067] After processing in S3, the estimation processing control unit 55 determines whether or not it is possible to estimate the cloud attenuation amount S in the remaining time (S4).

[0068] If the cloud attenuation amount S can be estimated based on the remaining time after estimating the rainfall attenuation amount Y (S4; yes), the estimation processing control unit 55 causes the cloud attenuation amount estimation unit 54 to prioritize the execution of the cloud attenuation amount S estimation process. The cloud attenuation amount estimation unit 54 estimates the cloud attenuation amount S based on the aircraft information and cloud information (S5).

[0069] After processing in S5, the estimation processing control unit 55 determines whether or not it is possible to estimate the free-space loss fluctuation amount X in the remaining time (S6).

[0070] If it is possible to estimate the free-space loss fluctuation X in the remaining time after estimating the cloud attenuation S (S6; yes), the estimation processing control unit 55 causes the free-space loss fluctuation estimation unit 51 to prioritize the estimation of the free-space loss fluctuation X. The free-space loss fluctuation estimation unit 51 estimates the free-space loss fluctuation X based on the aircraft information and nominal data 41 (S7).

[0071] After the processing in S7, the estimation processing control unit 55 determines whether or not it is possible to estimate the gain fluctuation amount Z in the remaining time (S8).

[0072] If the gain fluctuation amount Z can be estimated in the remaining time after estimating the free-space loss fluctuation amount X (S8; yes), the estimation processing control unit 55 causes the gain fluctuation amount estimation unit 52 to perform the gain fluctuation amount Z estimation process. The gain fluctuation amount estimation unit 52 estimates the gain fluctuation amount Z based on the aircraft information and nominal data 41 (S9).

[0073] If the cloud attenuation S cannot be estimated in the remaining time after estimating the rainfall attenuation Y (S4; no), if the free-space loss fluctuation X cannot be estimated in the remaining time after estimating the cloud attenuation S (S6; no), if the gain fluctuation Z cannot be estimated in the remaining time after estimating the free-space loss fluctuation X (S8; no), or after processing S9, the control variable determination unit 46 determines a control variable based on the estimated values ​​of the various losses (S10). Specifically, if the cloud attenuation S cannot be estimated in the remaining time after estimating the rainfall attenuation Y (S4; no), the control variable determination unit 46 considers the rainfall attenuation Y as the loss to be compensated and determines a control variable. If the free-space loss fluctuation X cannot be estimated in the remaining time after estimating the cloud attenuation S, the control variable determination unit 46 considers the sum of the rainfall attenuation Y and the cloud attenuation S as the loss to be compensated and determines a control variable. If the gain fluctuation Z cannot be estimated in the remaining time after estimating the free-space loss fluctuation X, the control variable determination unit 46 considers the sum of the rainfall attenuation Y, cloud attenuation S, and free-space loss fluctuation X as the loss to be compensated and determines the control variable. If all estimation processes have been executed, the control variable determination unit 46 considers the sum of the rainfall attenuation Y, cloud attenuation S, free-space loss fluctuation X, and gain fluctuation Z as the loss to be compensated and determines the control variable.

[0074] After the processing in S10, the control variable determination process ends (end).

[0075] 3. According to the effective embodiment, the aircraft information acquisition unit 42 acquires aircraft information, including the position and attitude of HAPS 20, which is reported from HAPS 20 without using the feeder link FL. The rainfall information acquisition unit 43 acquires rainfall information, including the amount of rainfall on the propagation path of the feeder link FL, based on the aircraft information. The cloud information acquisition unit 44 acquires cloud information, based on the aircraft information, which includes at least one piece of information selected from the presence or absence of clouds on the propagation path of the feeder link FL, the type of cloud, the thickness of the cloud, and the amount of water vapor. The loss estimation unit 45 estimates at least one loss, selected in a predetermined order from the free-space loss fluctuation amount X, gain fluctuation amount Z, rainfall attenuation amount Y, and cloud attenuation amount S occurring in the feeder link FL, based on the aircraft information, rainfall information, and cloud information. The control amount determination unit 46 determines the control amount of the uplink transmission power of the feeder link FL at a predetermined period based on the estimated at least one loss. As a result, the gateway 10 can implement "open-loop UPC (uplink power control)," which stabilizes fluctuations in the uplink of the feeder link FL in an open-loop manner.

[0076] To elaborate, in satellite communications, closed-loop control is sometimes employed to increase transmit power to compensate for attenuation caused by various factors by measuring the drop in the received signal level in the downlink. In addition, ALC (automatic level control) may be applied to stabilize the output level by further compensating for fluctuations in the signal level received by the satellite within the satellite itself. This stabilizes the transponder's output backoff value and suppresses signal distortion to prevent operation in the nonlinear region.

[0077] On the other hand, due to limitations in power generation and payload weight, HAPS20 may have difficulty equipping itself with complex systems such as ALCs or devices for transmitting closed-loop beacon signals. For this reason, it is preferable that HAPS20 can provide comprehensive compensation for the transmission power of the gateway 10 in the feeder link FL, commensurate with the attenuation caused by various factors, without using ALCs or closed-loop devices. Furthermore, while satellite communications employ a method of tracking the satellite by driving the antenna while performing a peak search to maximize the received level of the reference signal, communication with HAPS20 employs an open-loop control method that directs the antenna towards HAPS20 based on the position information of HAPS20 obtained by ADS-B. For this reason, the HAPS system 1 does not require a closed-loop antenna tracking system based on level changes due to the reference signal during tracking.

[0078] According to this embodiment, the power control device 18 estimates the free-space loss variation X, gain variation Z, rainfall attenuation Y, and cloud attenuation S by utilizing information such as ADS-B and high-resolution precipitation nowcast data. Based on the estimated losses, it then determines the control parameters. Furthermore, the antenna 15 tracks the HAPS 20 by utilizing the ADS-B information. This enables the simultaneous achievement of highly accurate UPC and tracking, even in an open-loop configuration.

[0079] Furthermore, the study revealed that when the feeder link FL is Q-band, there are significant differences in the four types of losses mentioned above.

[0080] Figure 7 shows an example of the magnitude of loss estimated by the power control device according to the embodiment. As shown in Figure 7, when the annual cumulative time rate is 95%, both the rainfall attenuation Y and the cloud attenuation S are several dB, and no significant difference is observed between the two. However, when the annual cumulative time rate is 99.9%, the cloud attenuation S is at most about 17 dB, while the rainfall attenuation Y exceeds 40 dB regardless of the elevation angle. Thus, it can be seen that the rainfall attenuation Y is significantly larger than the cloud attenuation S.

[0081] Although not shown in Figure 7, when the elevation angle from gateway 10 to HAPS 20 is 42-50°, the free-space loss variation X is approximately 1.2 dB at its maximum. The gain variation Z varies somewhat depending on the antenna pattern of HAPS 20, but when an omnidirectional antenna is used for antenna 21, it is approximately 1 dB at its maximum. Thus, when the feeder link FL is in the Q band, the rainfall attenuation Y is the largest, followed by the cloud attenuation S, free-space loss variation X, and then the gain variation Z, in decreasing order.

[0082] According to this embodiment, the estimation processing control unit 55 estimates the losses in the order of rainfall attenuation Y, cloud attenuation S, free-space loss fluctuation X, and gain fluctuation Z, and is configured to stop estimating losses that cannot be estimated within the update cycle of the controlled variable. As a result, even in high-frequency updates where the update cycle is less than 1 second, if all losses cannot be estimated within the update period due to constraints such as computing resources, at least the major attenuations can be estimated. Therefore, the deterioration of the accuracy of the controlled variable can be suppressed.

[0083] 4. Modifications, etc. Various modifications can be applied to the above embodiments.

[0084] 4.1 First Modification In the above embodiment, we described the case in which an open-loop UPC is applied to a HAPS system 1 equipped with a relay device that stays in the air, such as in the stratosphere. However, the platform to which an open-loop UPC can be applied is not limited to HAPS 20.

[0085] For example, open-loop UPC can be applied to systems that have relay devices that remain in space, such as artificial satellites. However, when acquiring aircraft information using ADS-B, open-loop UPC can only be applied to satellites at lower altitudes than GNSS.

[0086] Furthermore, for example, an open-loop UPC can also be applied to a system that uses a UAV (unmanned aerial vehicle), such as a drone, as a relay device to fly in an area at an altitude lower than HAPS20. In this case, the aircraft information acquisition unit 42 may acquire aircraft information using a C2 link (command and control link), not limited to ADS-B.

[0087] 4.2 Second Modification In the above embodiment, the case in which both the HAPS 20 and the gateway 10 that establish the feeder link FL are one station has been described, but the invention is not limited to this. For example, the HAPS 20 may establish a feeder link FL with multiple gateways 10. The gateway 10 may establish a feeder link FL with multiple HAPS 20s. In this case, each of the multiple gateways 10 may share the amount of control for the transmission power of the signal from its own station with the other stations.

[0088] Furthermore, the control quantities of each station shared among the multiple gateways 10 are not limited to current values, but may also include predicted values. Specifically, the power control device 18 estimates the position and attitude of HAPS 20 at a time later than the current time based on the nominal data 41 and aircraft information. The power control device 18 may then estimate the free-space loss fluctuation X and gain fluctuation Z at a time later than the current time based on the position and attitude at a time later than the current time. The power control device 18 also identifies a set of meshes on a map through which a straight line connecting the gateway 10 and HAPS 20 at a time later than the current time passes, and acquires rainfall information and cloud information corresponding to that set of meshes. When estimating predicted values, the cloud information may further include information on cloud movement in addition to the information described above. The power control device 18 may then estimate the rainfall attenuation Y and cloud attenuation S at a time later than the current time based on the acquired rainfall information and cloud information. Based on the estimated control values ​​for each station as described above, the multiple gateways 10 may cooperate with each other to select a gateway 10 in which stable received power at HAPS 20 is predicted rather than a gateway 10 in which a decrease in received power at HAPS 20 is predicted. Alternatively, a gateway 10 may select a HAPS 20 in which stable received power is predicted rather than a HAPS 20 in which a decrease in received power is predicted.

[0089] With the above configuration, the feeder link FL can be further stabilized while applying open-loop UPC to multiple gateways 10 and multiple HAPS 20 performing site diversity operations.

[0090] 4.3 Third Modification In addition, in the above embodiment, some or all of the configuration may be calculated using machine learning processing, such as a neural network. Specifically, by outputting the control variable and inputting the data acquired by the aircraft information acquisition unit 42, the rainfall information acquisition unit 43, and the cloud information acquisition unit 44, the loss estimation unit 45 and the control variable determination unit 46 can be made into machine learning estimation units. Furthermore, by outputting values ​​such as free-space loss fluctuation amount X, gain fluctuation amount Z, rainfall attenuation amount Y, and cloud attenuation amount S and inputting the acquired data, estimation can be performed as a substitute for each estimation unit in part. 4.4 Others In addition, in the above embodiment, the case in which the Q band is used for the feeder link FL has been described, and in this case, the order in which the losses are largest is described as rainfall attenuation amount Y, cloud attenuation amount S, free-space loss fluctuation amount X, and gain fluctuation amount Z, but it is not limited to this. For example, when the Ka band or V band is used for the feeder link FL, the order in which the losses are largest may change from the case of the Q band described above. Furthermore, the power control device 18 may be configured to change the order in which losses are estimated preferentially, depending on the frequency band used for the feeder link FL. This allows for the prioritization of large losses, regardless of the frequency band used, and their application to the control variable.

[0091] It should be noted that the present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Furthermore, each embodiment may be combined as appropriate, and in that case, the combined effects can be obtained. Moreover, the above embodiments include various inventions, and various inventions can be extracted by selecting combinations from the multiple constituent elements disclosed. For example, if the problem can be solved and effects obtained even if some constituent elements are deleted from all the constituent elements shown in the embodiment, then the configuration with these deleted constituent elements can be extracted as an invention.

[0092] 1...HAPS system, 10...Gateway, 11...Base station, 12, 27...U / C, 13...V-ATT, 14, 24, 28...HPA, 15, 21, 25...Antenna, 16, 22, 26...LNA, 17, 23...D / C, 31...Control circuit, 32...Storage, 33...Communication module, 34...Interface, 35...Drive, 36...Storage medium, 41...Nominal data, 42...Aircraft information acquisition unit, 43 ...Rainfall information acquisition unit, 44...Cloud information acquisition unit, 45...Loss estimation unit, 46...Control variable determination unit, 51...Free space loss fluctuation estimation unit, 52...Gain fluctuation estimation unit, 53...Rainfall attenuation estimation unit, 54...Cloud attenuation estimation unit, 55...Estimation processing control unit, 111...CU, 112...DU, 113...RU, FL...Feeder link, SL...Service link, UE...Terminal device, SA...Service area, CN...Core network

Claims

1. A power control device for a gateway that establishes a feeder link with a relay device staying in the air or space for communication with a ground terminal device, comprising: a first acquisition unit that acquires aircraft information including the position and attitude of the relay device, which is reported from the relay device without using the feeder link; a second acquisition unit that acquires rainfall information including the amount of rainfall on the propagation path of the feeder link based on the aircraft information; a third acquisition unit that acquires cloud information including at least one piece of information selected from the presence or absence of clouds, the type of cloud, the thickness of the cloud, and the amount of water vapor on the propagation path of the feeder link based on the aircraft information; an estimation unit that estimates at least one loss selected in a predetermined order from the amount of free-space loss fluctuation, the amount of gain fluctuation, the amount of rainfall attenuation, and the amount of cloud attenuation occurring in the feeder link based on the aircraft information, the rainfall information, and the cloud information; and a determination unit that determines the amount of control of the transmission power of the uplink of the feeder link at a predetermined period based on the estimated at least one loss.

2. The power control device according to claim 1, wherein the estimation unit is configured to change the predetermined order according to the frequency band used for the feeder link.

3. The power control device according to claim 1, wherein the estimation unit is configured to estimate losses in the order of rainfall attenuation, cloud attenuation, free-space loss fluctuation, and gain fluctuation when the frequency band used for the feeder link is the Q band, and to discontinue the estimation of losses for which estimation cannot be completed in time within the period.

4. The power control device according to claim 3, wherein the determination unit is configured to determine the control amount based on the sum of losses estimated within the period.

5. The power control device according to claim 4, wherein the period is 1 second or less.

6. The power control device according to claim 1, wherein the aircraft information includes information based on ADS-B (automatic dependent surveillance - broadcast).

7. A gateway comprising a power control device according to any one of claims 1 to 6, configured to update the transmission power of the feeder link at each period based on the controlled amount.

8. The gateway according to claim 7, further comprising an antenna that tracks the relay device based on the aircraft information and outputs a signal to the relay device.

9. A power control method by a power control device provided in a gateway that establishes a feeder link with a relay device staying in the air or space in communication with a ground terminal device, comprising: acquiring aircraft information including the position and attitude of the relay device which is notified by the relay device without using the feeder link; acquiring rainfall information including the amount of rainfall on the propagation path of the feeder link based on the aircraft information; acquiring cloud information including at least one piece of information selected from the presence or absence of clouds, the type of cloud, the thickness of the cloud, and the amount of water vapor on the propagation path of the feeder link based on the aircraft information; estimating at least one loss selected in a predetermined order from the amount of free-space loss fluctuation, the amount of gain fluctuation, the amount of rainfall attenuation, and the amount of cloud attenuation occurring in the feeder link based on the aircraft information, the rainfall information, and the cloud information; and determining a control amount of the transmission power of the uplink of the feeder link at a predetermined period based on the estimated at least one loss.

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