Signal processing device and signal processing method

Abstract

This signal processing device comprises a Doppler change compensation unit, a filter unit, and a reception beam control unit. The Doppler change compensation unit compensates for a Doppler shift change, which is the change over time in Doppler shift, in waveform data indicating the waveform of a wireless signal that is received by a communication device using each of a plurality of antennas. The filter unit extracts, from a plurality of waveform data in which the Doppler shift change has been compensated for, a narrow-band signal having a bandwidth equal to the bandwidth of a desired signal or equal to the sum of the bandwidth of the desired signal and a prescribed margin. The reception beam control unit performs reception beam control by using an adaptive array on a plurality of narrow-band signals extracted by the filter unit.

Description

[Technical Field]

[0001] The present invention relates to a signal processing device and a signal processing method. [Background technology]

[0002] In recent years, the satellite IoT (Internet of Things) platform (Satellite IoT-PF) has been under study. The satellite IoT-PF uses low-earth orbit satellites to collect sensor data from IoT devices located anywhere on Earth. The locations where IoT devices are installed include areas that are difficult to cover with terrestrial communication networks, such as on the ocean or in mountainous regions.

[0003] FIG. 16 illustrates radio signals received by a low-earth orbit satellite in a satellite IoT-PF. In FIG. 16, solid arrows represent desired signals from satellite IoT terminals, and dashed arrows represent interference signals from terrestrial IoT terminals. The satellite IoT terminals are the targets from which data is collected in the satellite IoT-PF. Low-earth orbit satellites receive not only desired signals transmitted from numerous satellite IoT terminals, but also numerous interference signals from terrestrial IoT terminals widely distributed on the ground. Therefore, the satellite IoT-PF must extract, demodulate, and decode weak desired signals transmitted from the desired satellite IoT terminals amid the interference between these signals. One effective method for achieving this is to equip a low-earth orbit satellite with multiple receiving antennas and use these receiving antennas to control the receiving beam (see, for example, Non-Patent Document 1).

[0004] Furthermore, low-earth orbit satellites are generally required to be small, lightweight, and power-efficient. Meanwhile, there are many types of low-power wide-area (LPWA) technologies used by IoT devices, including LoRa (registered trademark), Sigfox (registered trademark), and ELTRES (registered trademark). Equipping low-earth orbit satellites with receivers that demodulate and decode each LPWA technology increases the receiver's complexity and power consumption. Furthermore, extracting desired signals from multiple desired satellite IoT devices by controlling the receiving beam and then demodulating and decoding the extracted signals requires extensive signal processing within the low-earth orbit satellite, which also increases power consumption. Therefore, a system configuration in which a terrestrial device controls the receiving beam using offline signal processing has been studied (see, for example, Non-Patent Document 2). In this system configuration, a low-earth orbit satellite is equipped with multiple receiving antennas. The low-earth orbit satellite transmits sampled waveform data from each receiving antenna to the ground. The terrestrial device extracts the desired signal from the satellite IoT device by controlling the receiving beam using offline signal processing on the signal obtained from the received waveform data. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] J. Chu, X. Chen, C. Zhong and Z. Zhang, "Robust Design for NOMA-Based Multibeam LEO Satellite Internet of Things", IEEE Internet of Things Journal, vol. 8, no. 3, pp. 1959-1970, 2021. [Non-patent document 2] F. Yamashita, D. Goto, Y. Kojima, M. Matsui, K. Itokawa, K. Yoshizawa, K. Sakamoto, Y. Fujino, C. Kato, and M. Nakadai, "920-MHz IoT platform via LEO satellite employing feeder-link MIMO technology," Proc. 2020 International Conference on Emerging Technologies for Communications (ICETC2020), A1-2, Dec. 2020. Summary of the Invention [Problem to be solved by the invention]

[0006] To extract a desired satellite IoT terminal signal from among the signals of numerous satellite IoT terminals and terrestrial IoT terminals arriving at a low-earth orbit satellite and to demodulate and decode the extracted signal, it is effective to perform receive beam control as described in Non-Patent Document 1. However, in LPWA systems with high receive sensitivity that can be used in satellite IoT-PF, the transmission rate is low, at several hundred bits per second (bps), in order to achieve long-distance communication. Therefore, the transmission time (frame length) per transmission is generally several seconds. Due to the influence of time fluctuations in Doppler shift caused by the high-speed movement of low-earth orbit satellites, the signal bandwidth of a signal transmitted over several seconds spreads over a wide band. Hereinafter, the time fluctuations in Doppler shift are referred to as Doppler shift fluctuations. Doppler shift fluctuations can be obtained by differentiating the Doppler shift.

[0007] For example, suppose a satellite IoT terminal using Sigfox (registered trademark) performs uplink communication in the 920 MHz band and the low-orbit satellite is at an orbital altitude of 570 km. In this case, the maximum Doppler shift variation is 310 Hz / s. Furthermore, the transmission signal bandwidth of the Sigfox (registered trademark) system is 100 Hz wide, and the frame length is approximately 2 seconds. Therefore, the frequency shifts by approximately 600 Hz from the beginning to the end of the frame. In other words, the signal bandwidth when received by the low-orbit satellite is spread to a maximum width of approximately 700 Hz.

[0008] Adaptive arrays such as MMSE (Minimum Mean Square Error) and CMA (Constant Modulus Algorithm) are widely known as receive beam control techniques. These adaptive arrays generate weights for beamforming. The reception level of the desired signal arriving at a low-earth orbit satellite is very low, at around -130 dBm, and is significantly affected by thermal noise. Therefore, it is difficult to generate appropriate weights using only known signal sections, such as the short preamble included at the beginning of an LPWA signal frame. Therefore, it is effective to generate weights using the signal waveform of the entire frame.

[0009] However, as mentioned above, the signal bandwidth is spread several times larger than the original. If the entire frame is used, the number of interfering signals superimposed within the wide frequency bandwidth after spreading increases. This makes it difficult to separate signals in the spatial domain using receive beam control. A specific example will be explained using Figure 17.

[0010] FIG. 17 is a diagram illustrating conventional receive beam control. FIG. 17(a) is a diagram illustrating the positional relationship of wireless stations R1 to R4 with respect to a low-orbit satellite. Wireless station R1 is the desired satellite IoT terminal. FIG. 17(b) is a diagram illustrating the flow of reception processing, and FIG. 17(c) is a diagram illustrating the bands of transmission signals U1 to U4 from wireless stations R1 to R4, respectively. The low-orbit satellite receives received signals U1' to U4' in which the bands of the transmission signals U1 to U4 have been spread due to Doppler shift fluctuations. FIG. 17(d) is a diagram illustrating the bands of received signals U1' to U4'. The higher the elevation angle of the low-orbit satellite as seen from the wireless station, the greater the Doppler shift fluctuations and the wider the signal band.

[0011] In the case of offline beam control, waveform data of the received signals received by each of N receiving antennas #1 to #N of a low-earth-orbit satellite is transmitted to a terrestrial base station. The terrestrial base station performs reception processing as shown in FIG. 17(b). Specifically, the terrestrial base station performs frame detection on the waveform data of each receiving antenna #1 to #N, and filters the detected frames to remove the band of the received signal U1', which is the desired signal. The terrestrial base station performs reception beam control on the filtered frames of each receiving antenna #1 to #N, and then decodes them.

[0012] Figure 17(e) shows a received signal extracted by filtering. As shown in Figures 17(d) and 17(e), the band of received signal U1', which is the desired signal received by a low-earth orbit satellite, is several times wider than the bandwidth of transmitted signal U1. Many interfering signals, such as received signals U2' to U4', leak into this bandwidth. Therefore, even if receive beam control is performed on the filtered received signal, it may not be possible to completely remove the interfering signals, making it difficult to decode the desired signal.

[0013] In view of the above circumstances, an object of the present invention is to provide a signal processing device and a signal processing method that realize receive beam control with good signal separation performance even when Doppler shift fluctuations are large. [Means for solving the problem]

[0014] A signal processing device according to one aspect of the present invention includes a Doppler fluctuation compensation unit that compensates for Doppler shift fluctuation, which is a time variation of the Doppler shift, in waveform data indicating the waveforms of radio signals received by a communication device via each of a plurality of antennas; a filter unit that extracts narrowband signals, which are signals having a bandwidth equal to the bandwidth of a desired signal or a bandwidth that is a predetermined margin added to the bandwidth of the desired signal, from each of the plurality of waveform data in which the Doppler shift fluctuation has been compensated; and a receive beam control unit that performs receive beam control using an adaptive array on the plurality of narrowband signals extracted by the filter unit.

[0015] A signal processing method according to one aspect of the present invention includes a Doppler fluctuation compensation step of compensating for Doppler shift fluctuation in waveform data representing waveforms of radio signals received by a communication device via each of a plurality of antennas; a filtering step of extracting narrowband signals having a bandwidth equal to the bandwidth of a desired signal or a bandwidth obtained by adding a predetermined margin to the bandwidth of the desired signal from the signals represented by each of the plurality of waveform data whose Doppler shifts have been compensated; and a receiving beam control step of performing receiving beam control using an adaptive array on the plurality of narrowband signals extracted in the filtering step. [Effects of the Invention]

[0016] According to the present invention, it is possible to realize receiving beam control with good signal separation performance even when Doppler shift fluctuations are large. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating a functional configuration of a wireless communication system according to an embodiment of the present invention. [Figure 2] 1 is a block diagram showing a configuration of a wireless communication system according to a first embodiment. [Figure 3] FIG. 2 is a block diagram showing the configuration of a base station according to the first embodiment. [Figure 4] FIG. 2 is a block diagram showing the configuration of a signal processing unit according to the first embodiment. [Figure 5] FIG. 3 is a flowchart showing processing of the wireless communication system according to the first embodiment. [Figure 6] FIG. 3 is a flowchart showing processing of the wireless communication system according to the first embodiment. [Figure 7] FIG. 4 is a flowchart showing the processing of a signal processing unit and a terminal signal decoding unit according to the first embodiment. [Figure 8] FIG. 10 is a block diagram showing the configuration of a signal processing unit according to a second embodiment. [Figure 9] FIG. 10 is a flowchart showing the processing of a signal processing unit and a terminal signal decoding unit according to the second embodiment. [Figure 10] FIG. 10 is a block diagram showing the configuration of a signal processing unit according to a modified example of the second embodiment. [Figure 11] FIG. 11 is a block diagram showing the configuration of a mobile relay station according to the third embodiment. [Figure 12] FIG. 11 is a block diagram showing the configuration of a base station according to the third embodiment. [Figure 13] FIG. 10 is a block diagram showing the configuration of a wireless communication system according to a fourth embodiment. [Figure 14] FIG. 10 is a flowchart showing processing of a wireless communication system according to a fourth embodiment. [Figure 15] FIG. 10 is a flowchart showing processing of a wireless communication system according to a fourth embodiment. [Figure 16] FIG. 10 is a diagram showing radio signals received by a low-earth orbit satellite in the satellite IoT-PF. [Figure 17] FIG. 1 is a diagram for explaining conventional reception beam control. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the same parts in the drawings are designated by the same reference numerals, and the description thereof will be omitted.

[0019] FIG. 1 is a diagram showing the functional configuration of a wireless communication system 1 according to an embodiment of the present invention. The wireless communication system 1 includes a terminal station 2, a mobile relay station 3, and a base station 4. The base station 4 is an example of a signal processing device. In the wireless communication system 1, the number of each of the terminal stations 2, mobile relay stations 3, and base stations 4 is arbitrary. It is assumed that there are many terminal stations 2. The mobile relay station 3 moves in the sky above the Earth. The terminal station 2 and the base station 4 are installed on the Earth. The Earth includes land and sea.

[0020] Hereinafter, a radio signal transmitted from the terminal station 2 to the mobile relay station 3 will be referred to as a "terminal uplink signal." Also, a radio signal transmitted from the mobile relay station 3 to the base station 4 will be referred to as a "base station downlink signal."

[0021] The terminal station 2 is, for example, a satellite IoT terminal. The terminal station 2 includes a transmission data storage unit 21 and a transmission unit 22. The transmission data storage unit 21 stores transmission data. The transmission data is, for example, environmental data detected by a sensor. The transmission unit 22 generates a terminal uplink signal that sets the transmission data read from the transmission data storage unit 21. The transmission unit 22 transmits the terminal uplink signal to a mobile relay station 3 moving in the sky using a wireless method used in the satellite IoT platform.

[0022] The mobile relay station 3 is an example of a communication device that moves over time. The mobile relay station 3 moves in the sky by being mounted on a moving object. The mobile relay station 3 is provided, for example, on a LEO (Low Earth Orbit) satellite. The mobile relay station 3 orbits the Earth along a predetermined orbit. The altitude of a LEO satellite is 2000 km or less, and it takes about 1.5 hours to complete one orbit around the Earth. The mobile relay station 3 receives terminal uplink signals from each terminal station 2 while moving in the sky. The mobile relay station 3 stores data received via the terminal uplink signals. The mobile relay station 3 transmits the stored data to the base station 4 using a base station downlink signal when communication with the base station 4 is possible.

[0023] The mobile relay station 3 has an antenna used for wireless communication with the terminal station 2 and an antenna used for wireless communication with the base station 4, and the frequencies used for each wireless communication are generally different. Therefore, the mobile relay station 3 can perform wireless communication with the terminal station 2 and wireless communication with the base station 4 in parallel.

[0024] Mobile relay stations can be implemented using geostationary satellites or relay stations mounted on unmanned aerial vehicles such as drones and high-altitude platform stations (HAPS). However, relay stations mounted on geostationary satellites have a wide terrestrial coverage area (footprint), but their high altitudes mean that the link budget for satellite IoT terminals installed on the ground is very small. On the other hand, relay stations mounted on drones or HAPS have a high link budget but a narrow coverage area. Furthermore, drones require batteries, and HAPS require solar panels. In this embodiment, a mobile relay station 3 is mounted on a LEO satellite. Therefore, the link budget is within the limits, and since LEO satellites orbit outside the atmosphere, there is no air resistance and fuel consumption is low. Furthermore, the footprint is larger than when a relay station is mounted on a drone or HAPS.

[0025] However, because a mobile relay station 3 mounted on a LEO satellite communicates while moving at high speed, the time during which each terminal station 2 and base station 4 can communicate with the mobile relay station 3 is limited. Specifically, from the ground, the mobile relay station 3 passes overhead every few minutes. Therefore, a mobile relay station 3 mounted on a LEO satellite has a smaller link budget than a relay station mounted on a drone or HAPS. Therefore, the mobile relay station 3 receives terminal uplink signals from terminal stations 2 within the coverage area of ​​its current location while moving using multiple receiving antennas, and stores the waveform data obtained by sampling the waveform of the terminal uplink signals received by each receiving antenna.

[0026] For example, MIMO (Multiple Input Multiple Output) is used for reception using multiple receiving antennas. The diversity effect and beamforming effect of communication using multiple receiving antennas can improve communication quality. Hereinafter, waveform data obtained by sampling the waveform of a terminal uplink signal received by a certain receiving antenna will also be referred to as the waveform data of that receiving antenna or received waveform data.

[0027] As shown in FIG. 1, the mobile relay station 3 has receiving units 31-1 to 31-N, waveform sampling units 32-1 to 32-N, and a base station communication unit 34. The mobile relay station 3 has N (N is an integer equal to or greater than 2) receiving antennas (not shown) that receive terminal uplink signals. The N receiving antennas are referred to as receiving antennas #1 to #N. The receiving unit 31-n (n is an integer equal to or greater than 1 and equal to or less than N) receives the terminal uplink signal via the receiving antenna #n. The waveform sampling unit 32-n samples the received waveform of the terminal uplink signal received by the receiving unit 31-n and stores the waveform data obtained by the sampling. The base station communication unit 34 transmits a base station downlink signal, in which waveform data of the receiving antennas #1 to #N has been set, to the base station 4 at a time when the base station 4 is within its coverage area.

[0028] The base station 4 includes a base station receiver 41 and a signal processor 42. The base station receiver 41 obtains waveform data from a base station downlink signal received from a mobile relay station 3. The signal processor 42 obtains data transmitted by the terminal station 2 by performing received signal processing and decoding on the terminal uplink signal represented by the waveform data. In the received signal processing, the signal processor 42 compensates for Doppler shift fluctuation, which is a time variation of the Doppler shift, for each received waveform data. The signal processor 42 extracts narrowband signals, which are signals with the same bandwidth as the desired terminal uplink signal, from each received waveform data compensated for Doppler shift fluctuation, and performs receive beam control using an adaptive array using each extracted narrowband signal. This makes it possible to achieve sufficient signal separation performance even for signals with large Doppler shift fluctuation. The signal processor 42 decodes the received signal after receive beam control. Each embodiment will be described below.

[0029] (First embodiment) In the first embodiment, the Doppler shift fluctuation is estimated using a known signal.

[0030] 2 is a block diagram showing the configuration of a wireless communication system 100 according to the first embodiment. The wireless communication system 100 includes a terminal station 200, a mobile relay station 300, and a base station 400. The wireless communication system 100, the terminal station 200, the mobile relay station 300, and the base station 400 correspond to the wireless communication system 1, the terminal station 2, the mobile relay station 3, and the base station 4 in FIG. 1, respectively.

[0031] The terminal station 200 includes a transmission data storage unit 210, a transmission unit 220, and one or more antennas 230. The transmission data storage unit 210 and the transmission unit 220 correspond to the transmission data storage unit 21 and the transmission unit 22 of the terminal station 2 shown in FIG.

[0032] The transmission data storage unit 210 stores sensor data and the like. The transmission unit 220 reads out the sensor data from the transmission data storage unit 210 as terminal transmission data. The transmission unit 220 wirelessly transmits a terminal uplink signal containing the read terminal transmission data from the antenna 230. The transmission unit 220 transmits the signal using, for example, LPWA (Low Power Wide Area). LPWA includes LoRaWAN (registered trademark), Sigfox (registered trademark), LTE-M (Long Term Evolution for Machines), NB (Narrow Band)-IoT, etc., but any wireless communication method can be used. The transmission unit 220 may also transmit to other terminal stations 200 using time division multiplexing, OFDM (Orthogonal Frequency Division Multiplexing), or the like. The transmission unit 220 determines the channel and transmission timing to be used by its own station to transmit the terminal uplink signal using a method predetermined for the wireless communication method used.

[0033] The mobile relay station 300 includes N (N is an integer of 2 or more) antennas 310, a terminal communication unit 320, a data storage unit 330, a base station communication unit 340, and M (M is an integer of 1 or more) antennas 350. In this embodiment, an example in which M is 2 or more will be described.

[0034] Antenna 310 is a receiving antenna that receives a terminal uplink signal transmitted from terminal station 200. The N antennas 310 are referred to as antennas 310-1 to 310-N. Receiving antenna #n is antenna 310-n that receives the terminal uplink signal.

[0035] Terminal communication unit 320 has N receiving units 321, N frequency conversion units 322, and N received waveform recording units 323. The N receiving units 321 are referred to as receiving units 321-1 to 321-N, the N frequency conversion units 322 are referred to as frequency conversion units 322-1 to 322-N, and the N received waveform recording units 323 are referred to as received waveform recording units 323-1 to 323-N.

[0036] The receiving unit 321-n (n is an integer between 1 and N) receives a terminal uplink signal via the antenna 310-n. The frequency converting unit 322-n converts the frequency of the terminal uplink signal received by the receiving unit 321-n from an RF (Radio Frequency) signal to a baseband signal. A quadrature demodulator or the like is used for the frequency conversion. The receiving unit 321-n and the frequency converting unit 322-n correspond to the receiving unit 31-n in FIG. 1.

[0037] The received waveform recording unit 323-n samples the waveform of the terminal uplink signal frequency-converted by the frequency conversion unit 322-n, and generates waveform data indicating the value obtained by sampling. The received waveform recording unit 323-n writes received waveform information, which sets the antenna identification information of the antenna 310-n, the reception time of the terminal uplink signal at the antenna 310-n, and the generated waveform data, into the data storage unit 330. The antenna identification information is information that identifies each antenna 310. The received waveform recording unit 323-n corresponds to the waveform sampling unit 32-n in FIG. 1. The data storage unit 330 stores the received waveform information generated by the received waveform recording unit 323.

[0038] The base station communication unit 340 transmits a base station downlink signal to the base station 400. The base station communication unit 340 corresponds to the base station communication unit 34 in FIG. 1. The base station communication unit 340 includes a storage unit 341, a control unit 342, a transmission data modulation unit 343, and a transmission unit 344. The storage unit 341 stores a transmission start timing calculated in advance based on the orbital information of the LEO satellite on which the base station is mounted and the position of the base station 400. Furthermore, when there are multiple antennas 350, the storage unit 341 may store in advance a weight for each transmission time of the base station downlink signal transmitted from each antenna 350. The weight for each transmission time is calculated based on the orbital information of the LEO satellite and the position of each antenna station 410 provided in the base station 400. Note that a constant weight may be used regardless of the transmission time.

[0039] The control unit 342 controls the transmission data modulation unit 343 and the transmission unit 344 to transmit a base station downlink signal to the base station 400 at the transmission start timing stored in the storage unit 341. Furthermore, the control unit 342 instructs the transmission unit 344 on the weight for each transmission time read from the storage unit 341. The transmission data modulation unit 343 reads out the received waveform information stored in the data storage unit 330 as transmission data. The transmission data modulation unit 343 converts the transmission data into parallel signals and then modulates them. The transmission unit 344 weights the modulated parallel signals with the weight instructed by the control unit 342, and generates a base station downlink signal to be transmitted from each antenna 350. The transmission unit 344 transmits the generated base station downlink signal from the antenna 350, for example, using MIMO.

[0040] The antenna 350 is a transmitting antenna that transmits a base station downlink signal wirelessly, and may also receive a base station uplink signal wirelessly transmitted from the base station 400.

[0041] When there is one antenna 350, the control unit 342 does not instruct the transmission unit 344 about the weight. The transmission data modulation unit 343 modulates the transmission data into a transmission signal to be transmitted from the single antenna 350. The transmission unit 344 transmits the modulated transmission signal from the antenna 350.

[0042] The base station 400 includes one or more antenna stations 410. The following describes an example in which there are multiple antenna stations 410. The multiple antenna stations 410 are arranged at positions spaced apart so that the difference in the angles of arrival of signals from the multiple antennas 350 of the mobile relay station 300 becomes large.

[0043] 3 is a diagram showing an example configuration of a base station 400. The base station 400 includes a plurality of antenna stations 410, a receiver 420, a base station signal receiving processor 430, and a terminal signal receiving processor 440. The receiver 420 and the base station signal receiving processor 430 correspond to the base station receiver 41 in FIG. 1, and the terminal signal receiving processor 440 corresponds to the signal processor 42 in FIG. 1.

[0044] The antenna station 410 converts the base station downlink signal received from the mobile relay station 300 into an electrical signal and outputs it to the receiver 420. The receiver 420 aggregates the base station downlink signals received from multiple antenna stations 410. The receiver 420 stores weights for each reception time of the base station downlink signal received by each antenna station 410, based on the orbital information of the LEO satellites and the position of each antenna station 410. The receiver 420 multiplies the base station downlink signal input from each antenna station 410 by a weight corresponding to the reception time of that base station downlink signal, and combines the received signals multiplied by the weights. Note that the same weights may be used regardless of the reception time.

[0045] The base station signal reception processing unit 430 receives the received signal combined by the receiving unit 420. If there is one antenna station 410, or if the base station 400 does not have an antenna station 410 but has one antenna, the base station 400 does not have a receiving unit 420, and the base station signal reception processing unit 430 receives the base station downlink signal received from the antenna station 410 or antenna as the received signal. The base station signal reception processing unit 430 demodulates and decodes the received signal and obtains received waveform information. The base station signal reception processing unit 430 outputs the received waveform information to the terminal signal reception processing unit 440.

[0046] The terminal signal reception processing unit 440 performs reception processing of the terminal uplink signal indicated by the received waveform information. The terminal signal reception processing unit 440 performs reception processing using the wireless communication method used for transmission by the terminal station 200 to acquire terminal transmission data. The terminal signal reception processing unit 440 includes a distribution unit 441, a signal processing unit 442, and a terminal signal decoding unit 443.

[0047] The distributor 441 reads out waveform data for each of the receiving antennas #1 to #N at the same reception time from the received waveform information, and outputs the read waveform data to the signal processor 442. The waveform data for the receiving antenna #n is waveform data linked to the antenna identification information of the antenna 310-n. The signal processor 442 performs processing such as frame detection (terminal signal detection), Doppler shift variation compensation, filtering, and receiving beam control on the waveform data for the receiving antennas #1 to #N. In this embodiment, a description of other receiving processing performed by a general wireless communication device will be omitted.

[0048] Frame detection is a process of detecting a section containing a terminal transmission frame of a terminal uplink signal from waveform data. The signal processing unit 442 performs frame detection on the waveform data of each of the receiving antennas #1 to #N. The signal processing unit 442 performs Doppler shift fluctuation compensation on each detected terminal transmission frame to narrow the band of the desired signal, and then filters the frequency domain of the desired signal. The signal processing unit 442 performs receiving beam control using the waveform data of the filtered terminal transmission frame portion of each of the receiving antennas #1 to #N. In receiving beam control, the signal processing unit 442 multiplies the waveform data of the terminal transmission frame portion of each of the receiving antennas #1 to #N by weights that perform amplitude correction and phase correction to constructively combine the desired signals of each reception system while suppressing interference signals, and then adds and combines the results. The signal processing unit 442 outputs the symbols of the received signal obtained from the added and combined waveform data to the terminal signal decoding unit 443.

[0049] The terminal signal decoding unit 443 decodes the symbols output by the signal processing unit 442 to obtain the terminal transmission data transmitted from the terminal station 200. The terminal signal decoding unit 443 can also use a decoding method with a large calculation load, such as SIC (Successive Interference Cancellation).

[0050] 4 is a diagram showing a detailed configuration of signal processing section 442. Signal processing section 442 includes frame detection sections 510-1 to 510-N, Doppler fluctuation compensation sections 520-1 to 520-N, filter sections 530-1 to 530-N, and reception beam control section 540.

[0051] The frame detection unit 510-n (n is an integer between 1 and N) performs frame detection on the waveform data of receiving antenna #n. The frame detection unit 510-n calculates the cross-correlation between the transmitted known signal and the received signal waveform indicated by the waveform data. As a result, the frame detection unit 510-n detects a predetermined position of the received frame in the waveform data of receiving antenna #n. The transmitted known signal is a known signal such as a preamble that is set at a predetermined position, such as the beginning of a frame, within a frame defined by the frame format of each LPWA system used by the satellite IoT terminal accommodated in the satellite IoT-PF.

[0052] Specifically, a plurality of transmission known signals each having a different frequency shift f [Hz] added thereto are prepared in advance. The frequency of the terminal uplink signal and the range of Doppler shift assumed from the orbit information of the mobile relay station 300 are -df max ~df max For example, when a 920 MHz terminal uplink signal is transmitted to a mobile relay station 300 at an orbital altitude of 570 km, the expected range of Doppler shift is approximately -20 [kHz] to 20 [kHz]. step is set to a few Hz, and the frequency shift f=-df max ,-df max +f step ,-df max +2×f step ,...,df max -2×f step ,df max -f step ,df maxA transmitted known signal with each of these added is prepared. These transmitted known signals are stored in advance in a storage unit inside or outside the frame detection unit 510-n. The frame detection unit 510-n calculates the cross-correlation between each transmitted known signal and the received signal waveform indicated by the waveform data. The frame detection unit 510-n searches for a transmitted known signal for which the correlation value of the cross-correlation is maximum or equal to or greater than a threshold, and detects the position of the received signal waveform where this correlation value is obtained as the setting position of the known signal.

[0053] When the frame detection unit 510-n detects the setting position of a known signal in a received frame in the waveform data, it extracts a section of the frame length defined by the frame format from the waveform data, or identifies the end position of the frame based on the frame length information described in the header of the received frame and extracts the frame section.

[0054] The frequency shift added to the searched transmitted known signal is approximately the same as the Doppler shift experienced by the terminal uplink signal of the desired signal. Therefore, the frequency shift added to the searched transmitted known signal may be used as an estimate of the Doppler shift to perform Doppler shift compensation on the waveform data.

[0055] The above describes the case where a transmitted known signal to which different types of frequency shifts are added is used. However, a transmitted known signal to which different types of frequency shifts are also added in addition to the frequency shift may also be used, as in the Doppler shift fluctuation compensation method B described below. That is, the frame detection unit 510-n may prepare in advance multiple transmitted known signals to which different types of frequency shifts and combinations of different types of frequency fluctuations are added, and calculate the cross-correlation between each transmitted known signal and the received signal waveform indicated by the waveform data of the receiving antenna #n. Note that the frequency fluctuation added to the transmitted known signal corresponds to the Doppler shift fluctuation experienced by the terminal uplink signal. For example, as described above, when transmitting a 920 MHz terminal uplink signal to a mobile relay station 300 at an orbital altitude of 570 km, the expected range of Doppler shift fluctuation is approximately -310 Hz / s to -50 Hz / s. Alternatively, the frame detection unit 510-n may use a commonly used method, such as detecting a section in the waveform data of the receiving antenna #n where the time domain waveform has a certain amplitude or more as a section that includes a terminal transmission frame.

[0056] The Doppler shift compensation unit 520-n performs Doppler shift compensation on the received frame extracted by the frame detection unit 510-n. Doppler shift compensation is a process of compensating for Doppler shift fluctuations experienced by a desired signal. In this embodiment, the Doppler shift compensation unit 520-n estimates Doppler shift fluctuations using a known signal in the received frame by either method A or method B below, and performs compensation on waveform data in the received frame section to cancel out the estimated Doppler shift fluctuations. The Doppler shift compensation unit 520-n outputs the received frame with the Doppler shift fluctuation compensated for to the filter unit 530-n.

[0057] (Method A) The Doppler fluctuation compensator 520-n calculates (estimates) the Doppler shift fluctuation based on the amount of phase rotation in a known signal section, such as the beginning of a received frame. The known signal section is a section in which a known signal, such as a preamble, is set in the received frame. The Doppler fluctuation compensator 520-n compensates for the Doppler shift fluctuation by applying a phase rotation that cancels out the calculated Doppler shift fluctuation throughout the entire received frame section. Note that some LPWA systems, such as ELTRES (registered trademark), have known signals distributed throughout the entire packet. In this case, the Doppler shift fluctuation can be estimated and compensated for based on the amount of phase rotation applied to the distributed known signals. As such, this embodiment is not limited to a configuration that uses a preamble at the beginning of a frame.

[0058] (Method B) A plurality of fluctuation detection signals are prepared in advance by adding frequency fluctuations corresponding to different Doppler shift fluctuations to a known signal such as a preamble set at a predetermined position, such as the beginning of a frame, defined by the LPWA frame format. For example, assume that the Doppler shift fluctuation estimated based on the terminal uplink signal frequency, which is the frequency of the terminal uplink signal, and the orbital altitude of the satellite carrying the mobile relay station 300 at each time, is -310 Hz / s to -50 Hz / s. In this case, a plurality of types of fluctuation detection signals are prepared by adding frequency fluctuations in increments of several Hz between -310 Hz / s and -50 Hz / s to the known signal. These multiple types of fluctuation detection signals are stored in an internal or external memory unit of the Doppler fluctuation compensation unit 520-n. The Doppler fluctuation compensation unit 520-n calculates the cross-correlation between the received frame extracted from the waveform data of antenna #n and each fluctuation detection signal. When the correlation value of the cross-correlation is maximum or equal to or greater than a threshold, the Doppler shift compensation unit 520-n uses the frequency fluctuation added to the fluctuation detection signal used to calculate the correlation value as an estimate of the Doppler shift fluctuation.The Doppler shift compensation unit 520-n compensates for the Doppler shift fluctuation by adding a phase rotation that cancels out the estimated Doppler shift fluctuation over the entire reception frame interval obtained from the waveform data of antenna #n.

[0059] The filter unit 530-n filters the received waveform data of the received frame section for which Doppler shift fluctuation compensation has been performed by the Doppler shift fluctuation compensation unit 520-n. Filtering is a process of band-limiting the desired signal, which has been narrowed by Doppler shift fluctuation compensation, using a narrowband filter. By using the narrowband filter to extract only the band surrounding the desired signal, the effects of numerous interfering signals outside the desired signal band are suppressed. The passband width of the narrowband filter is set to be the same as the transmission signal bandwidth of the desired signal defined in the LPWA system to be extracted, or to a bandwidth slightly wider (with a small margin) than that transmission bandwidth. The filter unit 530-n outputs the received waveform data extracted by filtering to the receive beam control unit 540.

[0060] The receiving beam control unit 540 receives received waveform data of the bands surrounding the desired signal extracted by the narrowband filters in each of the filter units 530-1 to 530-N. The receiving beam control unit 540 uses this received waveform data to perform adaptive array processing such as MMSE or CMA. As a result, the receiving beam control unit 540 separates, in the spatial domain, interference signals remaining within the filter band and extracts the desired signal. The receiving beam control unit 540 outputs the extracted desired signal to the terminal signal decoding unit 443.

[0061] For example, suppose that transmission signals U1 to U4 shown in FIG. 17(c) are transmitted from four terminal stations 200 corresponding to wireless stations R1 to R4 shown in FIG. 17(a). Transmission signal U1 is a desired signal transmitted from terminal station 200 corresponding to wireless station R1 of the desired satellite IoT terminal. As shown in the lower left of FIG. 4, receiving antennas #1 to #N of mobile relay station 300 receive received signals U1' to U4' in which the bandwidth of transmission signals U1 to U4 has been spread due to Doppler shift fluctuation, as in FIG. 17(d). Doppler shift compensation units 520-1 to 520-N compensate for the Doppler shift fluctuation suffered by transmission signal U1, which is the desired signal, and therefore received signals U1' to U4' are narrowed in bandwidth to become received signals U1" to U4". Filter units 530-1 to 530-N pass waveform data of the desired signal with a passband width F using narrowband filters, thereby separating received signals in the frequency domain and suppressing interference. Reception beam control unit 540 performs reception beam control on the reception frames in which interference from each of reception antennas #1 to #N has been suppressed, thereby separating the interference signals and obtaining reception signal U1".

[0062] The operation of the wireless communication system 100 will be described. Fig. 5 is a flow diagram showing the processing of the wireless communication system 100 when the terminal station 200 transmits a terminal uplink signal. The terminal station 200 acquires data detected by an external or internal sensor (not shown) as needed, and writes the acquired data to the transmission data storage unit 210 (step S111). The transmission unit 220 reads the sensor data from the transmission data storage unit 210 as terminal transmission data. The transmission unit 220 wirelessly transmits, from the antenna 230, a terminal uplink signal in which the terminal transmission data is set, at a transmission start timing obtained in advance based on, for example, orbital information of the LEO satellite on which the mobile relay station 300 is mounted (step S112). The terminal station 200 repeats the processing from step S111.

[0063] The receiving units 321-1 to 321-N of the mobile relay station 300 receive the terminal uplink signal transmitted from the terminal station 200 (step S121). Note that uplink signals of the same frequency may be transmitted simultaneously from multiple terminal stations 200. In this case, desired signals transmitted at the same frequency at the same time may interfere with each other, but reception beam control separates the signals and makes each signal receivable. The frequency conversion unit 322-n frequency-converts the terminal uplink signal received by the receiving unit 321-n from an RF signal to a baseband signal. The received waveform recording unit 323-n writes received waveform information, which associates waveform data representing the waveform of the terminal uplink signal frequency-converted by the frequency conversion unit 322-n with the reception time and antenna identification information of the antenna 310-n, into the data storage unit 330 (step S122). The mobile relay station 300 repeats the process from step S121.

[0064] 6 is a flow diagram showing the processing of the wireless communication system 100 when a base station downlink signal is transmitted from the mobile relay station 300. When the control unit 342 of the base station communication unit 340 of the mobile relay station 300 detects that it is the transmission start timing stored in the storage unit 341, it instructs the transmission data modulation unit 343 and the transmission unit 344 to transmit received waveform information (step S211).

[0065] The transmission data modulation unit 343 reads out the received waveform information from the data storage unit 330 as transmission data (step S212). The received waveform information that the transmission data modulation unit 343 reads out from the storage unit 341 is received waveform information for which a reception time is set that is later than the reception time set in the received waveform information last read out by the transmission data modulation unit 343. The transmission data modulation unit 343 converts the acquired transmission data into parallel data and then modulates it.

[0066] The transmitter 344 weights the transmission data modulated by the transmission data modulator 343 with the weight instructed by the controller 342, and generates a base station downlink signal that is a transmission signal to be transmitted from each antenna 350. The transmitter 344 transmits each generated base station downlink signal from the antenna 350, for example, by MIMO (step S213). The mobile relay station 300 repeats the process from step S211.

[0067] Each antenna station 410 of the base station 400 receives a base station downlink signal from the mobile relay station 300 (step S221). Each antenna station 410 converts the received base station downlink signal into an electrical signal and outputs the resulting received signal to the receiver 420. The receiver 420 synchronizes the timing of the received signals received from each antenna station 410. The receiver 420 multiplies the received signals received by each antenna station 410 by a weight and adds the multiplied signals. The base station signal reception processor 430 demodulates the added received signal and decodes the demodulated received signal. As a result, the base station signal reception processor 430 obtains received waveform information (step S222). The base station signal reception processor 430 outputs the received waveform information to the terminal signal reception processor 440.

[0068] The terminal signal reception processing unit 440 performs reception processing of the terminal uplink signal indicated by the received waveform information (step S223). Specifically, the distribution unit 441 reads out waveform data having the same reception time from the received waveform information. The distribution unit 441 outputs the read waveform data and the antenna identification information of the waveform data to the signal processing unit 442. The signal processing unit 442 performs frame detection (terminal signal detection), Doppler shift variation compensation, filtering, and offline beam control on the received signal indicated by the waveform data output from the distribution unit 441. The signal processing unit 442 outputs the symbols of the received signal that have been subjected to offline beam control to the terminal signal decoding unit 443. The terminal signal decoding unit 443 decodes the symbols input from the signal processing unit 442 and obtains the terminal transmission data transmitted from the terminal station 200. The base station 400 repeats the processing from step S221.

[0069] Fig. 7 is a flow diagram showing the processing of the signal processing unit 442 and the terminal signal decoding unit 443 of the base station 400. The processing shown in Fig. 7 is performed in the processing of step S223 in Fig. 6. The signal processing unit 442 and the terminal signal decoding unit 443 perform the processing shown in Fig. 7 for each desired signal. The correspondence between the reception time and the desired signal may be calculated in advance based on the orbit information of the LEO satellite on which the mobile relay station 300 is mounted and the position of each terminal station 200.

[0070] The frame detection units 510-1 to 510-N of the signal processing unit 442 respectively receive the waveform data of receiving antennas #1 to #N read by the distribution unit 441. The frame detection unit 510-n performs frame detection processing on the received waveform data to detect frames of the LPWA system to be extracted (step S311). The LPWA system to be extracted is the LPWA system used for the desired signal. In the frame detection processing, the frame detection unit 510-n reads out, from a storage unit internal or external to the frame detection unit 510-n, multiple transmitted known signals to which different types of frequency shifts have been added, or multiple transmitted known signals to which combinations of different types of frequency shifts and different types of frequency fluctuations have been added. These transmitted known signals are known signals defined by the frame format of the LPWA system to be extracted. The frame detection unit 510-n calculates the cross-correlation between each of the multiple read transmitted known signals and the received signal waveform indicated by the waveform data of receiving antenna #n. The frame detector 510-n detects a frame interval in the waveform data of the receiving antenna #n based on the position of the received signal waveform where the maximum correlation value or a correlation value equal to or greater than a threshold value is obtained. The frame detector 510-n extracts the detected frame interval from the waveform data of the receiving antenna #n and outputs it to the Doppler shift compensator 520-n.

[0071] The Doppler fluctuation compensation unit 520-n estimates the Doppler shift fluctuation in the frame interval extracted by the frame detection unit 510-n by the above-mentioned method A or method B using a known signal. The Doppler fluctuation compensation unit 520-n performs compensation on the waveform data in the frame interval to cancel out the estimated Doppler shift fluctuation (step S312). The Doppler fluctuation compensation unit 520-n outputs the waveform data in the frame interval in which the Doppler shift fluctuation has been compensated to the filter unit 530-n.

[0072] The filter unit 530-n performs narrowband filtering on the waveform data of the received frame that has been Doppler shift compensated for by the Doppler shift compensator 520-n (step S313). The passband width of the narrowband filtering is the same as the transmission signal bandwidth of the desired signal defined in the LPWA system to be extracted, or a bandwidth with a small margin added. The filter unit 530-n outputs the narrowband signal extracted by filtering to the receive beam controller 540.

[0073] Reception beam control unit 540 performs reception beam control using an adaptive array on the narrowband signals input from each of filter units 530-1 to 530-N, thereby separating, in the spatial domain, interference signals remaining in the filter bands and extracting desired signals (step S314). Reception beam control unit 540 outputs the extracted desired signals to terminal signal decoding unit 443. Terminal signal decoding unit 443 performs decoding processing on the desired signals input from reception beam control unit 540 to obtain terminal transmission data (step S315).

[0074] As described above, the signal processing unit 442 of the base station 400 narrows the band of the desired signal received by the mobile relay station 300 by compensating for Doppler shift fluctuations. Therefore, the signal processing unit 442 can perform receiving beam control while minimizing the influence of interference signals using a narrow-band filter. Therefore, the signal processing unit 442 can achieve high signal separation performance.

[0075] (Second embodiment) In the first embodiment, Doppler shift fluctuations are estimated and compensated for using known signals. However, known signals such as preambles are signal sequences common to terminals using the same LPWA system. As the number of satellite IoT terminals and terrestrial IoT terminals increases year by year and signal interference between them becomes more frequent, the influence of the same known signals contained in the interfering signals deteriorates the accuracy of Doppler shift fluctuation estimation and compensation, making it difficult to narrow the band of the desired signal. To suppress performance degradation in narrowing the band of the desired signal by compensating for Doppler shift fluctuations even in situations where interference occurs more frequently, in the second embodiment, Doppler shift fluctuations are blindly compensated for without using known signals, and the desired signal is narrowed in band before receive beam control is performed. The second embodiment will be described, focusing on the differences from the first embodiment.

[0076] The configuration of the wireless communication system of the second embodiment is similar to that of the wireless communication system 100 of the first embodiment shown in Fig. 2. The configuration of the base station of the second embodiment is similar to that of the base station 400 of the first embodiment shown in Fig. 3, except for the following points. That is, the base station 400 of the second embodiment includes a signal processing unit 500 and a terminal signal decoding unit 505 shown in Fig. 8, instead of the signal processing unit 442 and the terminal signal decoding unit 443 of the first embodiment shown in Fig. 4.

[0077] 8 is a block diagram showing the configuration of a signal processing unit 500 according to the second embodiment. The signal processing unit 500 processes Δf1(t), Δf2(t), ..., Δf MThe signal processing unit 500 has a first processing unit 501-1 to an M-th processing unit 501-M, which are processing units for compensating for M types of Doppler shift fluctuations (t). For example, assume that the Doppler shift fluctuation estimated based on the terminal uplink signal frequency, which is the frequency of the terminal uplink signal transmitted by the terminal station 200, and the orbital altitude of the satellite carrying the mobile relay station 300 per unit time, is -310 Hz / s to -50 Hz / s. If the range from 50 Hz / s to 310 Hz / s is divided into M types in increments of several Hz, the signal processing unit 500 has first processing units 501-1 to an M-th processing unit 501-M, which are processing units corresponding to the M types of Doppler shift fluctuations. The required increment width differs depending on the characteristics of the LPWA signal to be extracted and is determined in advance by system design. The first processing unit 501-1 to the M-th processing unit 501-M perform processes such as Doppler shift fluctuation compensation, frame detection, filtering, and receiving beam control on the waveform data of the receiving antennas #1 to #N, respectively. Note that a description of the reception processing performed by the signal processing unit 500 and other general wireless communication devices will be omitted.

[0078] The terminal signal decoding unit 505 performs decoding processing on the output of the receiving beam control in each of the M processing planes of the first processing unit 501-1 to the Mth processing unit 501-M. The terminal signal decoding unit 505 outputs the decoding result of a processing plane for which decoding was successful as the processing result of that functional unit. For example, the terminal signal decoding unit 505 determines that decoding was successful when the determination result of a CRC (Cyclic Redundancy Check) is OK.

[0079] The mth processing unit 501-m (m is an integer between 1 and M) includes Doppler fluctuation compensators 550-1-m to 550-Nm, frame detectors 560-1-m to 560-Nm, filter units 530-1-m to 530-Nm, and receive beam controller 540-m.

[0080] The Doppler fluctuation compensation unit 550-nm (n is an integer between 1 and N) on the mth processing surface is Δf mThe frequency fluctuation of (t) is added to the waveform data of the receiving antenna #n. The frame detection unit 560-nm calculates Δf m The frame detector 560-nm receives waveform data from the receiving antenna #n, to which frequency fluctuation (t) has been added. The frame detector 560-nm performs the same processing as the frame detector 510-n in the first embodiment to detect a section containing a terminal transmission frame from the received waveform data and extract the detected frame section. Specifically, the frame detector 560-nm calculates the cross-correlation between multiple transmitted known signals, each with a different type of frequency shift added, and the received signal waveform represented by the waveform data to which frequency fluctuation has been added. The frame detector 560-nm searches for the transmitted known signal for which the correlation value of the cross-correlation is maximum or exceeds a threshold, and detects, for example, the beginning of the received frame based on the position of the received waveform where the correlation value was obtained. Once the frame detector 560-nm detects the beginning of the received frame, it extracts a section of the frame length defined by the frame format from the waveform data, or identifies the frame end position based on the frame length information written in the header of the received frame, and extracts the frame section. As in the first embodiment, the frequency shift added to the searched transmission known signal is approximately the same as the Doppler shift received by the terminal uplink signal of the desired signal. Therefore, the frequency shift added to the searched transmission known signal may be used as an estimated value of the Doppler shift, and the waveform data may be Doppler-shift compensated for. Alternatively, the frame detection unit 560-nm may use a commonly used method, such as detecting a section in which the time-domain waveform has a certain amplitude or more as a section containing a frame transmitted by the terminal station 200.

[0081] The filter unit 530-nm performs filtering using a narrowband filter to limit the band of the waveform data of the received frame extracted by the frame detection unit 560-nm, similar to the filter unit 530-n of the first embodiment shown in Fig. 4. The receiving beam control unit 540-m inputs narrowband signals in the band surrounding the desired signal extracted by each of the filter units 530-1-m to 530-Nm. The receiving beam control unit 540-m uses these input narrowband signals to perform receiving beam control using an adaptive array, similar to the receiving beam control unit 540 of the first embodiment shown in Fig. 4. The receiving beam control unit 540-m outputs the received signal, from which the interference signal has been separated by receiving beam control, to the terminal signal decoding unit 505.

[0082] Terminal signal decoding section 505 decodes the received signals input from first processing section 501-1 to Mth processing section 501-M, and performs CRC check on the decoded results. Terminal signal decoding section 505 outputs the decoded results that are determined to be successful by the CRC check.

[0083] The following describes the operation of the wireless communication system 100 of the second embodiment. The wireless communication system 100 of the second embodiment performs the same processing as the processing of the wireless communication system 100 of the first embodiment shown in FIGS.

[0084] Fig. 9 is a flow diagram showing the processing of the signal processing unit 500 and the terminal signal decoding unit 505 according to the second embodiment. The processing shown in Fig. 9 is performed in the processing of step S223 in Fig. 6. The signal processing unit 500 and the terminal signal decoding unit 505 perform the processing shown in Fig. 9 for each desired signal.

[0085] The signal processing unit 500 inputs waveform data of receiving antennas #1 to #N to the first processing unit 501-1 to the M-th processing unit 501-M. The first processing unit 501-1 to the M-th processing unit 501-M respectively input waveform data Δf1(t), Δf2(t), ..., Δf M The Doppler shift compensation unit 550-nm of the signal processing unit 500-m performs compensation for the Doppler shift (t) fluctuation on the input waveform data (step S411). mThe frequency fluctuation of (t) is added to the waveform data of receiving antenna #n.

[0086] The first processing unit 501-1 to the M-th processing unit 501-M perform a frame detection process to detect an LPWA frame to be extracted from the waveform data of the receiving antennas #1 to #N that has been subjected to Doppler shift fluctuation compensation (step S412). m The frame detector 560-nm receives waveform data from the receiving antenna #n to which a frequency shift (t) has been added. The frame detector 560-nm reads out multiple transmitted known signals, each with a different type of frequency shift added, from an internal or external storage unit of the frame detector 560-nm. These transmitted known signals are known signals defined by the frame format of the LPWA system to be extracted. The frame detector 560-nm calculates the cross-correlation between each of the multiple read transmitted known signals and the received signal waveform indicated by the input waveform data from the receiving antenna #n. The frame detector 560-nm detects a frame section in the input waveform data based on the position of the received signal waveform where the maximum correlation value or a correlation value greater than or equal to a threshold value is obtained. The frame detector 560-nm extracts the frame section detected by frame detection from the input waveform data and outputs it to the filter unit 530-nm.

[0087] First processing unit 501-1 through Mth processing unit 501-M each perform narrowband filtering on the received waveform data of the detected frame (step S413). That is, filter unit 530-nm performs narrowband filtering on the wavelength data of the frame section extracted by frame detection unit 560-nm, with the passband width being the same as the transmission signal bandwidth of the desired signal or a bandwidth with a small margin added. Filter unit 530-nm outputs the narrowband signal extracted by filtering to reception beam control unit 540-m.

[0088] First processing unit 501-1 through M-th processing unit 501-M each perform receive beam control on the narrowband signals obtained by filtering. That is, receive beam control unit 540-m performs receive beam control using an adaptive array on the narrowband signals input from filter units 530-1-m through 530-Nm, thereby separating interference signals remaining in the filter band in the spatial domain and extracting the desired signal (step S414). Receiving beam control unit 540-m outputs the desired signal to terminal signal decoding unit 505.

[0089] The terminal signal decoding unit 505 performs decoding processing on the desired signals input from the receiving beam control units 540-1 to 540-M of the first processing unit 501-1 to the Mth processing unit 501-M (step S415). The terminal signal decoding unit 505 performs CRC checking on the decoded results of the desired signals input from the M processing planes of the first processing unit 501-1 to the Mth processing unit 501-M. If the CRC checking result is OK, the terminal signal decoding unit 505 determines that the decoding is successful. The terminal signal decoding unit 505 outputs the decoding results of the processing planes for which decoding was successful as the processing results (step S416).

[0090] The signal processing unit 500 may perform subsequent processing only on a processing plane where the cross-correlation value of the frame detection is equal to or greater than a threshold value. That is, the frame detection unit 560-nm determines whether one or more of the cross-correlation values ​​calculated when each of the frame detection units 560-1-m to 560-Nm performs frame detection processing on the waveform data of the receiving antennas #1 to #M is equal to or greater than a preset threshold value. If a cross-correlation value equal to or greater than the threshold value is found, the frame detection unit 560-nm outputs the frame detection result to the subsequent filter unit 530-nm. On the other hand, if no cross-correlation value equal to or greater than the threshold value is found, the frame detection unit 560-nm discards the waveform data without inputting it to the filter unit 530-nm. The other processing is the same as that of the signal processing unit 500 described above. This allows for a reduction in the amount of calculation compared to the basic form of the signal processing unit 500.

[0091] Also, as shown in FIG. 10, a configuration may be adopted in which subsequent processing is performed only on a processing plane where the power within the filter band after filtering is equal to or greater than a threshold value.

[0092] Fig. 10 is a diagram showing the configuration of a signal processing unit 502 according to a modification of the second embodiment. In Fig. 10, the same components as those in the signal processing unit 501 shown in Fig. 8 are denoted by the same reference numerals, and their description will be omitted. The signal processing unit 502 processes Δf1(t), Δf2(t), ..., Δf M It has first processing unit 503-1 to M-th processing unit 503-M which are processing units for compensating for M types of Doppler shift fluctuations (t). The m-th processing unit 503-m differs from the m-th processing unit 501-m shown in Fig. 8 in that it further includes power calculation units 570-1-m to 570-Nm.

[0093] Power calculation unit 570-nm receives the narrowband signal of antenna #n that has been narrowband filtered from filter unit 530-nm. Power calculation unit 570-nm calculates the power of the received waveform data. Power calculation unit 570-nm determines whether one or more of the powers of the narrowband signals of receiving antennas #1 to #N calculated by power calculation units 570-1-m to 570-Nm are equal to or greater than a preset threshold. If the power is equal to or greater than the threshold, power calculation unit 570-nm outputs the narrowband signal received from filter unit 530-nm to reception beam control unit 540-m. On the other hand, if the power is not equal to or greater than the threshold, power calculation unit 570-nm discards the narrowband signal without inputting it to reception beam control unit 540-m.

[0094] Alternatively, power calculation units 570-1-m through 570-Nm may output the narrowband signal and calculated power information to reception beam control unit 540-m. Reception beam control unit 540-m performs reception beam control when one or more pieces of input power information are equal to or greater than a preset threshold. Reception beam control unit 540-m may discard the narrowband signal without performing reception beam control when none of the input power information meets the threshold.

[0095] The other processes are the same as those of the above-described signal processing unit 500. This makes it possible to reduce the amount of calculation compared to the signal processing unit 500 in the basic form.

[0096] According to this embodiment, it is possible to realize reception beam control with good signal separation performance even in a situation where interference occurs frequently.

[0097] (Third embodiment) In the first and second embodiments, the frequency conversion of the terminal uplink signal is performed in the mobile relay station, but the frequency conversion may be performed in the base station. In the third embodiment, a wireless communication system in which frequency conversion is performed in the base station will be described, focusing on the differences from the first and second embodiments described above.

[0098] Fig. 11 is a diagram showing the configuration of a wireless communication system 100a according to the third embodiment. In Fig. 11, the same components as those in the wireless communication system 100 according to the first embodiment shown in Fig. 2 are denoted by the same reference numerals, and their description will be omitted. The wireless communication system 100a includes a terminal station 200, a mobile relay station 300a, and a base station 400a.

[0099] 2 in that it includes a terminal communication unit 320a instead of the terminal communication unit 320. The terminal communication unit 320a includes N receivers 321 and N received waveform recorders 324. The received waveform recorder 324 connected to the receiver 321-n is referred to as the received waveform recorder 324-n. The received waveform recorder 324-n samples the received waveform of the terminal uplink signal received by the receiver 321-n as an RF signal, and generates waveform data indicating the value obtained by the sampling. The received waveform recorder 324-n writes received waveform information, which sets the antenna identification information of the antenna 310-n, the reception time of the terminal uplink signal at the antenna 310-n, and the generated waveform data, to the data storage unit 330.

[0100] Fig. 12 is a diagram showing the configuration of base station 400a. In Fig. 12, the same parts as those in base station 400 shown in Fig. 3 are assigned the same reference numerals, and their description will be omitted. Base station 400a shown in Fig. 12 differs from base station 400 shown in Fig. 3 in that it includes terminal signal reception processing unit 440a instead of terminal signal reception processing unit 440. Terminal signal reception processing unit 440a includes distribution unit 441a, N frequency conversion units 444, signal processing unit 442, and terminal signal decoding unit 443. The N frequency conversion units 444 will be referred to as frequency conversion units 444-1 to 444-N, respectively.

[0101] The distribution unit 441a reads out waveform data of the same reception time from the received waveform information, and outputs the read waveform data to frequency conversion units 444-1 to 444-N according to the antenna identification information associated with the waveform data. In other words, the distribution unit 441a outputs the waveform data of receiving antenna #n to frequency conversion unit 444-n. The waveform data of receiving antenna #n is waveform data associated with the antenna identification information of antenna 310-n. The frequency conversion unit 444-n frequency-converts the signal represented by the input waveform data of receiving antenna #n from an RF signal to a baseband signal. A quadrature demodulator or the like is used for the frequency conversion. The frequency conversion units 444-1 to 444-N each output the frequency-converted signal to the signal processing unit 442.

[0102] The wireless communication system 100a of the third embodiment performs the same processing as the processing of the wireless communication system 100 of the first embodiment shown in Fig. 5 and Fig. 6, except for the following points. That is, in step S122 of Fig. 5, the received waveform recording unit 324-n of the mobile relay station 300a writes received waveform information, which associates waveform data representing the waveform of the terminal uplink signal received by the receiving unit 321-n with the reception time and antenna identification information of the antenna 310-n, into the data storage unit 330. Also, in step S223 of Fig. 6, the distribution unit 441a reads out waveform data having the same reception time from the received waveform information. The distribution unit 441a outputs the read waveform data to the frequency conversion units 444-1 to 444-N in accordance with the antenna identification information associated with the waveform data. The frequency conversion unit 444-n frequency-converts the received signal represented by the waveform data of the antenna #n from an RF signal to a baseband signal. The frequency converter 444-n outputs the frequency-converted received signal to the signal processor 442. The processing after the received signals of the antennas #1 to #N are input from the frequency converters 444-1 to 444-N to the signal processor 442 is the same as that in the first embodiment described above.

[0103] Signal processing unit 442 performs the processing of the first embodiment shown in Fig. 7 using the received signals of antennas #1 to #N input from frequency conversion units 444-1 to 444-N, respectively. Alternatively, when mobile relay station 300a is equipped with signal processing unit 500 and terminal signal decoding unit 505 of the second embodiment shown in Fig. 8 or signal processing unit 502 and terminal signal decoding unit 505 of the second embodiment shown in Fig. 10 instead of signal processing unit 442 and terminal signal decoding unit 443, signal processing unit 500 and signal processing unit 502 perform the processing of the second embodiment using the received signals of antennas #1 to #N input from frequency conversion units 444-1 to 444-N, respectively.

[0104] (Fourth embodiment) In the first to third embodiments described above, the terminal uplink signal is decoded in the base station. In this embodiment, the terminal uplink signal is decoded in the mobile relay station. This embodiment will be described focusing on the differences from the first to third embodiments.

[0105] Fig. 13 is a configuration diagram of a wireless communication system 105 according to the fourth embodiment. In the figure, the same components as those in the wireless communication system 100 according to the first embodiment shown in Fig. 2 are denoted by the same reference numerals, and their description will be omitted. The wireless communication system 105 has a terminal station 200, a mobile relay station 305, and a base station 405. The mobile relay station 305 is an example of a signal processing device.

[0106] Mobile relay station 305 includes antennas 310-1 to 310-N (N is an integer of 2 or more), a terminal communication unit 360, a data storage unit 370, a base station communication unit 340, and M antennas 350 (M is an integer of 1 or more).

[0107] The terminal communication unit 360 includes receiving units 321-1 to 321-N, frequency conversion units 322-1 to 322-N, a signal processing unit 361, and a terminal signal decoding unit 362. The signal processing unit 361 and the terminal signal decoding unit 362 have functions similar to those of the signal processing unit 442 and the terminal signal decoding unit 443 of the first embodiment shown in FIG. 4, the signal processing unit 500 and the terminal signal decoding unit 505 of the second embodiment shown in FIG. 8, or the signal processing unit 502 and the terminal signal decoding unit 505 of the second embodiment shown in FIG. 10. The terminal signal decoding unit 362 writes the terminal transmission data obtained as a result of the decoding to the data storage unit 370. The data storage unit 370 stores the terminal transmission data transmitted by each terminal station 200. The transmission data modulation unit 343 of the base station communication unit 340 reads the terminal transmission data from the data storage unit 370 as transmission data.

[0108] The base station 405 includes one or more antenna stations 410, a receiver 420, and a base station signal reception processor 430. The base station signal reception processor 430 demodulates and decodes the received signal combined in the receiver 420 to obtain terminal transmission data.

[0109] The operation of the wireless communication system 105 will now be described. Fig. 14 is a flow diagram showing the processing of the wireless communication system 105 when transmitting an uplink signal from the terminal station 200. In Fig. 14, the same processes as those shown in the flow diagram of the first embodiment shown in Fig. 5 are denoted by the same reference numerals.

[0110] The processing of the terminal station 200 in steps S111 to S112 is the same as that of the first embodiment shown in Fig. 5. The processing of the mobile relay station 305 in step S121 is the same as that of the first embodiment shown in Fig. 5. That is, the receiving units 321-1 to 321-N of the mobile relay station 305 receive the terminal uplink signals transmitted from the terminal station 200 (step S121). The frequency conversion unit 322-n frequency-converts the terminal uplink signals of the receiving antenna #n received by the receiving unit 321-n from an RF signal to a baseband signal. The signal processing unit 361 inputs the terminal uplink signals of the receiving antennas #1 to #N that have been frequency-converted to baseband signals from each of the frequency conversion units 322-1 to 322-N.

[0111] Signal processing unit 361 performs reception processing on terminal uplink signals of receiving antennas #1 to #N input from frequency conversion units 322-1 to 322-N, respectively. Terminal signal decoding unit 362 decodes the symbols that have been reception-processed by signal processing unit 361, and obtains terminal transmission data transmitted from terminal station 200 (step S511). Terminal signal decoding unit 362 writes the terminal transmission data obtained by decoding to data storage unit 370 (step S512).

[0112] In step S511, the signal processing unit 361 and the terminal signal decoding unit 362 use the terminal uplink signals of the receiving antennas #1 to #N to perform, for each desired signal, the same processing as that of the signal processing unit 442 and the terminal signal decoding unit 443 of the first embodiment shown in Fig. 7. Alternatively, in step S511, the signal processing unit 361 and the terminal signal decoding unit 362 use the terminal uplink signals of the receiving antennas #1 to #N to perform, for each desired signal, the same processing as that of the signal processing unit 500 and the terminal signal decoding unit 505 of the second embodiment shown in Fig. 9, or the same processing as that of the signal processing unit 502 and the terminal signal decoding unit 505 of the second embodiment.

[0113] Fig. 15 is a flow diagram showing the processing of the wireless communication system 105 when transmitting a base station downlink signal from the mobile relay station 305. In Fig. 15, the same processes as those shown in the flow diagram of the first embodiment shown in Fig. 6 are denoted by the same reference numerals.

[0114] The mobile relay station 305 performs the same processes as steps S211 to S213 in Fig. 5 (steps S611 to S613). However, in step S611, the control unit 342 instructs the transmission data modulation unit 343 and the transmission unit 344 to transmit terminal transmission data. Also, in step S612, the transmission data modulation unit 343 reads out the terminal transmission data stored in the data storage unit 370 as transmission data. In step S613, the transmission unit 344 transmits, from the antenna 350, a base station downlink signal in which the terminal transmission data is set. The mobile relay station 305 repeats the processes from step S611.

[0115] As in the first embodiment, the base station 405 receives a base station downlink signal from the mobile relay station 305 (step S221). The receiver 420 synchronizes the timing of the received signals received from each antenna station 410. The receiver 420 multiplies the received signals received by each antenna station 410 by a weight and adds them together. The base station signal reception processor 430 demodulates the added received signal and decodes the demodulated received signal to obtain terminal transmission data (step S221). The base station 405 repeats the process from step S221.

[0116] In the above-described embodiment, the mobile relay station 300 and the base station 400, the mobile relay station 300a and the base station 400a, and the mobile relay station 305 and the base station 405 communicate using MIMO, but the present invention is not limited to this. For example, the mobile relay stations 300, 300a, and 305 may transmit base station downlink signals to the base stations 400, 400a, and 405 using a single antenna 350. Similarly, the base stations 400, 400a, and 405 may receive base station downlink signals from the mobile relay stations 300, 300a, and 305 using a single antenna station or a single antenna instead of multiple antenna stations 410.

[0117] In the above embodiment, the mobile body on which the mobile relay station is mounted is described as a LEO satellite, but the mobile body may be a geostationary satellite or another flying body that flies in the sky, such as a drone or HAPS. The above embodiment is also applicable to a case where a stationary relay station receives a radio signal from, for example, a terminal station that moves in a fixed orbit.

[0118] According to the above-described embodiment, it is possible to realize reception beam control that can achieve sufficient signal separation performance even in a satellite IoT-PF with large Doppler shift fluctuations.

[0119] All or part of the functions of the signal processing unit 442 and terminal signal decoding unit 443 of the base station 400, 400a, and the signal processing unit 361 and terminal signal decoding unit 362 of the mobile relay station 305 may be realized by a processor such as a central processing unit (CPU) or a graphics processing unit (GPU) reading and executing a program from a storage unit. Furthermore, all or part of the functions of the signal processing unit 442 and terminal signal decoding unit 443 of the base station 400, 400a, and the signal processing unit 361 and terminal signal decoding unit 362 of the mobile relay station 305 may be realized using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA).

[0120] According to the above-described embodiment, the signal processing device includes a Doppler shift compensation unit, a filter unit, and a receive beam control unit. For example, the signal processing device is the base station 400, 400a, or mobile relay station 305 of the embodiment. The Doppler shift compensation unit compensates for Doppler shift fluctuation, which is a time variation of Doppler shift, in waveform data indicating waveforms of radio signals received by the communication device via each of multiple antennas. For example, the communication device is the mobile relay station 300, 300a, or 305 of the embodiment. The filter unit extracts narrowband signals, which are signals with a bandwidth equal to the bandwidth of a desired signal or a bandwidth that is the bandwidth of the desired signal plus a predetermined margin, from signals indicated by each of the multiple waveform data compensated for Doppler shift. The receive beam control unit performs receive beam control using an adaptive array on the multiple narrowband signals extracted by the filter unit.

[0121] The Doppler shift compensation unit may estimate the Doppler shift fluctuation based on the amount of phase rotation in a known signal section within a signal frame included in the waveform data, and compensate for the Doppler shift fluctuation by applying a phase rotation that cancels out the estimated Doppler shift fluctuation over the section of the signal frame included in the waveform data.

[0122] The Doppler shift compensation unit may calculate the cross-correlation between the waveform data and a transmitted known signal, which is a known signal to which each of multiple types of frequency shifts has been added. The frequency shift corresponds to the Doppler shift shift estimated from the terminal uplink signal frequency and the satellite orbit altitude. The Doppler shift compensation unit compensates for the Doppler shift shift by applying a phase rotation, over the section of the signal frame included in the waveform data, that cancels out the frequency shift added to the transmitted known signal for which the correlation value obtained as a result of the calculation is maximum or equal to or greater than a threshold.

[0123] The signal processing device may further include a frame detection unit. The frame detection unit is, for example, frame detection units 510-1 to 510-N of the embodiment. The frame detection unit detects signal frames included in the waveform data based on a result of calculating cross-correlation between waveform data from each of a plurality of antennas and each of known signals to which different types of frequency shifts have been added or each of known signals to which different types of frequency shifts and different types of frequency fluctuations have been added, and extracts sections of the detected signal frames from the waveform data. The Doppler shift compensation unit compensates for Doppler shift fluctuations in each of the waveform data extracted by the frame detection unit.

[0124] The signal processing device includes a plurality of processing units and a decoding unit. The plurality of processing units are, for example, first processing unit 501-1 to Mth processing unit 501-M and first processing unit 503-1 to Mth processing unit 503-M in the embodiment. Each processing unit includes a Doppler shift compensation unit, a filter unit, and a receiving beam control unit. The decoding unit decodes the received signal. The plurality of processing units correspond to different types of Doppler shift fluctuations. The multiple types of frequency fluctuations are, for example, frequency fluctuations in predetermined increments that cancel out the range of expected Doppler shift fluctuations. The Doppler shift compensation unit included in the processing unit compensates for the Doppler shift fluctuation corresponding to the processing unit in the waveform data of each of the plurality of antennas. The decoding unit decodes the received signal obtained when the receiving beam control unit of each of the plurality of processing units performs receiving beam control, and outputs the decoding result where the decoding was successful.

[0125] Each processing unit may further include a frame detection unit. The frame detection unit is, for example, frame detection units 560-1-1 to 560-NM of the embodiment. The frame detection unit detects signal frames included in the waveform data based on the results of calculation of cross-correlations between waveform data in which the Doppler shift fluctuation has been compensated for by the Doppler shift compensation unit and known signals to which different types of frequency shifts have been added, extracts sections of the detected signal frames from the waveform data, and outputs the extracted sections to the filter unit. Each processing unit may perform processing in the filter unit and receive beam control unit included in the processing unit when one or more of the correlation values ​​resulting from calculation of the cross-correlations in the frame detection unit included in the processing unit is equal to or greater than a threshold value.

[0126] Each processing unit may perform processing of the receiving beam control unit that the processing unit has when the signal power of at least one of the multiple narrowband signals extracted by the filter unit that the processing unit has is greater than or equal to a threshold value.

[0127] Furthermore, at least some of the functions of the signal processing device may be implemented by a computer. In this case, a program for implementing the functions of the signal processing device may be recorded on a computer-readable recording medium, and the program may be read and executed by a computer system. The computer system may include hardware such as a processor, an OS, and peripheral devices. The program for the signal processing device may be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include portable media such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and storage devices such as a hard disk built into a computer system. The program for the signal processing device may be transmitted via a telecommunications line.

[0128] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Explanation of symbols]

[0129] 1, 100, 100a, 105 Wireless communication system 2,200 terminal stations 3, 300, 300a, 305 Mobile relay station 4, 400, 400a, 405 base station 21 Transmission data storage unit 22 Transmitter 31-1~31-N Receiver 32-1~32-N Waveform sampling section 34 Base Station Communication Unit 41 Base station receiver 42 Signal Processing Section 210 Transmission data storage unit 220 Transmitter 230 Antenna 310-1~310-N, 350 Antenna 320, 320a terminal communication unit 321-1~321-N Receiver 322-1~322-N Frequency conversion unit 323-1 to 323-N, 324-1 to 324-N Received waveform recording section 330 Data storage unit 340 Base Station Communication Unit 341 Storage section 342 Control Unit 343 Transmission data modulation section 344 Transmitter 360 Terminal Communication Unit 361 Signal Processing Unit 362 Terminal signal decoding unit 370 Data Storage Unit 400 base stations 410 Antenna Station 420 Receiving unit 430 Base station signal receiving processing unit 440, 440a Terminal signal receiving processing unit 441, 441a distribution section 442 Signal Processing Unit 443 Terminal signal decoding unit 444-1 to 444-N Frequency conversion section 500, 502 signal processing unit 501-1, 503-1 First processing section 501-2, 503-2 Second processing section 501-M, 503-M Mth Processing Section 505 Terminal signal decoding unit 510-1 to 510-N Frame detection section 520-1 to 520-N, 550-1-1 to 550-NM Doppler fluctuation compensation unit 530-1 to 530-M, 530-1-1 to 530-NM filter section 540, 540-1 to 540-M Receiving beam control unit 560-1-1~560-NM Frame detector 570-1-1~570-NM Power calculation section

Claims

1. a Doppler shift compensation unit that compensates for Doppler shift fluctuation, which is a time fluctuation of Doppler shift, with respect to waveform data indicating waveforms of radio signals received by each of a plurality of antennas by the communication device; a filter unit that extracts a narrowband signal, which is a signal having a bandwidth equal to the bandwidth of a desired signal or a bandwidth that is a predetermined margin added to the bandwidth of the desired signal, from each of the plurality of waveform data that have been compensated for Doppler shift fluctuations; a receiving beam control unit that performs receiving beam control using an adaptive array on the plurality of narrowband signals extracted by the filter unit; Equipped with the Doppler shift compensation unit calculates a cross-correlation between the waveform data and a transmitted known signal obtained by adding each of a plurality of types of frequency fluctuations to a known signal of a wireless communication method detected for the waveform data, and compensates for the Doppler shift fluctuation by adding a phase rotation, over a section of a signal frame included in the waveform data, that cancels out the frequency fluctuation added to the transmitted known signal for which the correlation value obtained as a result of the calculation is maximum or equal to or greater than a threshold, as an estimated value of the Doppler shift fluctuation. Signal processing device.

2. the Doppler shift compensator estimates Doppler shift fluctuation based on a phase rotation amount of a known signal section within a signal frame included in the waveform data, and compensates for the Doppler shift fluctuation by applying a phase rotation that cancels out the estimated Doppler shift fluctuation over the section of the signal frame included in the waveform data. The signal processing device according to claim 1 .

3. a frame detection unit that detects signal frames included in the waveform data based on a result of calculating cross-correlation between the waveform data of each of a plurality of antennas and each of known signals to which frequency shifts that are different types of estimated Doppler shifts have been added or each of known signals to which different types of frequency shifts and frequency fluctuations that are different types of estimated Doppler shift fluctuations have been added, and extracts a section of the detected signal frame from the waveform data; the Doppler shift compensation unit compensates for Doppler shift fluctuations in each of the waveform data extracted by the frame detection unit; 3. The signal processing device according to claim 1 or 2.

4. The signal processing device includes: a plurality of processing units including the Doppler fluctuation compensation unit, the filter unit, and the reception beam control unit; a decoding unit that decodes a received signal, the plurality of processing units correspond to different types of Doppler shift fluctuations, respectively; the Doppler shift compensation unit included in the processing unit compensates for the Doppler shift fluctuation corresponding to the processing unit with respect to the waveform data of each of the plurality of antennas; The decoding unit decodes the received signals obtained by performing the receiving beam control by the receiving beam control units of each of the plurality of processing units, and outputs the decoding results of successful decoding. The signal processing device according to claim 1 .

5. the processing unit further includes a frame detection unit that detects a signal frame included in the waveform data based on a result of calculation of a cross-correlation between the waveform data in which the Doppler shift fluctuation has been compensated for by the Doppler shift fluctuation compensation unit and each known signal to which a frequency shift that is a different type of estimated Doppler shift has been added, extracts a section of the detected signal frame from the waveform data, and outputs the extracted section to the filter unit; the processing unit performs processing of the filter unit and the receiving beam control unit included in the processing unit when one or more of the correlation values ​​resulting from the calculation of the cross-correlation in the frame detection unit included in the processing unit is equal to or greater than a threshold value. The signal processing device according to claim 4 .

6. the processing unit performs processing of the reception beam control unit included in the processing unit when the signal power of at least one of the plurality of narrowband signals extracted by the filter unit included in the processing unit is equal to or greater than a threshold value. The signal processing device according to claim 4 .

7. a Doppler shift compensation step of compensating for Doppler shift fluctuation, which is a time fluctuation of Doppler shift, with respect to waveform data indicating waveforms of wireless signals received by each of a plurality of antennas by the communication device; a filtering step of extracting a narrowband signal, which is a signal having a bandwidth equal to the bandwidth of a desired signal or a bandwidth obtained by adding a predetermined margin to the bandwidth of the desired signal, from each of the plurality of waveform data whose Doppler shift fluctuations have been compensated for; a receiving beam control step of performing receiving beam control using an adaptive array on the plurality of narrowband signals extracted in the filtering step; and In the Doppler shift compensation step, a cross-correlation between the waveform data and a transmitted known signal obtained by adding each of a plurality of types of frequency fluctuations to a known signal of a wireless communication method detected for the waveform data is calculated, and the Doppler shift fluctuation is compensated for by adding a phase rotation, over a section of a signal frame included in the waveform data, that cancels out the frequency fluctuation added to the transmitted known signal for which the correlation value obtained as a result of the calculation is maximum or equal to or greater than a threshold, as an estimated value of the Doppler shift fluctuation. Signal processing methods.

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