Wireless communication system, relay device and wireless communication method

Abstract

The relay device includes a receiving unit, a storage unit, and a sending unit. The receiving unit receives data wirelessly sent by the first communication device through multiple first antennas. The storage unit wirelessly sends the data received by the receiving unit from multiple second antennas to the second communication device. The second communication device includes a relay data receiving unit. The relay data receiving unit receives data wirelessly sent by the relay device through multiple third antennas.

Description

Technical Field

[0001] The present invention relates to a wireless communication system, a relay device and a wireless communication method. Background Art

[0002] With the development of IoT (Internet of Things) technology, research is being conducted on installing IoT terminals equipped with various sensors in various places. For example, it is also envisioned that IoT is effectively used to collect data in places where it is difficult to install base stations, such as buoys or ships at sea and mountainous areas. On the other hand, there is a technology that uses UAVs (Unmanned Aerial Vehicles) or geostationary satellites to wirelessly communicate with communication devices on the ground (for example, refer to Non-Patent Document 1).

[0003] Prior Art Literature

[0004] Non-patent literature

[0005] Non-patent literature 1: Wei Feng et al., “UAV-aided MIMO communications for 5G Internet of Things,” IEEE Internet of Things Journal, Vol. 6, No. 2, 2018, pp. 1731-1740. Summary of the invention

[0006] Problems to be solved by the invention

[0007] In Non-Patent Document 1, data is collected from IoT terminals using a UAV terminal, but there is no description of transmitting the collected data to a communication device on the ground.

[0008] In view of the above situation, an object of the present invention is to provide a wireless communication system, a relay device and a wireless communication method, which can relay data sent by a communication device to another communication device through a mobile relay device.

[0009] Solutions to Solve Problems

[0010] One embodiment of the present invention is a wireless communication system, which has a first communication device, a second communication device and a mobile relay device, the aforementioned relay device has: a receiving unit, which receives data wirelessly sent by the aforementioned first communication device through multiple first antennas; and a sending unit, which wirelessly sends the aforementioned data received by the aforementioned receiving unit from multiple second antennas to the aforementioned second communication device, the aforementioned second communication device has: a relay data receiving unit, which receives the aforementioned data wirelessly sent by the aforementioned relay device through multiple third antennas.

[0011] One embodiment of the present invention is a relay device, which is the aforementioned relay device in a wireless communication system having a first communication device, a second communication device and a mobile relay device, the aforementioned relay device comprising: a receiving unit, which receives data wirelessly transmitted by the aforementioned first communication device through multiple first antennas; and a transmitting unit, which wirelessly transmits the aforementioned data received by the aforementioned receiving unit from multiple second antennas to the aforementioned second communication device, and the aforementioned second communication device uses multiple third antennas to receive the aforementioned data.

[0012] One embodiment of the present invention is a wireless communication method, which is a wireless communication method performed by a wireless communication system having a first communication device, a second communication device and a mobile relay device, the wireless communication method comprising: a receiving step, the relay device receives data wirelessly sent by the first communication device through multiple first antennas; a sending step, the relay device wirelessly sends the data received in the receiving step from multiple second antennas to the second communication device; and a relay data receiving step, the second communication device receives the data wirelessly sent in the sending step through multiple third antennas.

[0013] One embodiment of the present invention is a wireless communication method, which is a wireless communication method performed by the aforementioned relay device in a wireless communication system having a first communication device, a second communication device and a mobile relay device, and the aforementioned wireless communication method comprises: a receiving step, which receives data sent wirelessly by the aforementioned first communication device through multiple first antennas; and a sending step, which sends the aforementioned data received in the aforementioned receiving step from multiple second antennas to the aforementioned second communication device via wireless, and the aforementioned second communication device uses multiple third antennas to receive the aforementioned data.

[0014] Effects of the Invention

[0015] According to the present invention, data sent by a communication device can be relayed to another communication device through a mobile relay device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a diagram showing the configuration of a wireless communication system according to the first embodiment of the present invention.

[0017] Figure 2 : is a flowchart showing the processing of the wireless communication system according to this embodiment.

[0018] Figure 3 It is a diagram showing the configuration of a wireless communication system according to the second embodiment.

[0019] Figure 4: is a flowchart showing the processing of the wireless communication system according to this embodiment.

[0020] Figure 5 : is a flowchart showing the processing of the wireless communication system according to this embodiment.

[0021] Figure 6 It is a diagram showing the configuration of a wireless communication system according to the third embodiment.

[0022] Figure 7 : is a flowchart showing the processing of the wireless communication system according to this embodiment.

[0023] Figure 8 : is a flowchart showing the processing of the wireless communication system according to this embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] (First embodiment)

[0026] Figure 1 1 is a block diagram of a wireless communication system 1 according to the first embodiment. The wireless communication system 1 includes a mobile relay station 2, a terminal station 3, and a base station 4. The number of mobile relay stations 2, terminal stations 3, and base stations 4 included in the wireless communication system 1 is arbitrary, but it is assumed that the number of terminal stations 3 is a large number.

[0027] The mobile relay station 2 is an example of a relay device, which is mounted on a mobile body and the area in which communication is possible moves over time. For example, a mobile relay station 2 is provided on a LEO (Low Earth Orbit) satellite. The altitude of the LEO satellite is below 2000km, and it takes about 1.5 hours to orbit the earth. The terminal station 3 and the base station 4 are arranged on the earth, on the ground or on the sea, etc. The terminal station 3 is, for example, an IoT terminal. The terminal station 3 collects data such as environmental data detected by sensors, and sends the data to the mobile relay station 2 wirelessly. In this figure, only two terminal stations 3 are shown. The mobile relay station 2 moves above the earth, and simultaneously receives data sent from each of the multiple terminal stations 3 through wireless signals, and wirelessly sends the received data to the base station 4. The base station 4 receives the data collected by the terminal station 3 from the mobile relay station 2.

[0028] As a mobile relay station, it is considered to use a relay station carried by a geostationary satellite or an unmanned aerial vehicle such as a drone or HAPS (High Altitude Platform Station). However, in the case of a relay station carried by a geostationary satellite, although the coverage area (coverage zone) on the ground is wide, due to the high altitude, the link budget for the IoT terminal set on the ground is very small. On the other hand, in the case of a relay station carried by a drone or HAPS, although the link budget is high, the coverage area is narrow. Moreover, drones require batteries, while HAPS require solar panels. In this embodiment, the mobile relay station 2 is carried on a LEO satellite. Therefore, in addition to the link budget falling within the limit, the LEO satellite has no air resistance and consumes less fuel because it orbits outside the atmosphere. In addition, compared with the case where the relay station is carried on a drone or HAPS, the coverage area is also large.

[0029] However, since the mobile relay station 2 mounted on LEO moves at high speed and communicates at the same time, Doppler frequency shift occurs in the wireless signal. In addition, the link budget of the relay station mounted on LEO is smaller than that of the case where the relay station is mounted on a drone or HAPS. Therefore, the mobile relay station 2 receives wireless signals from the terminal station 3 through multiple antennas and sends wireless signals to the base station 4 through multiple antennas. The communication quality can be improved by using the diversity effect and beamforming effect of communication using multiple antennas. In this embodiment, the following situation is taken as an example for explanation: the mobile relay station 2 relays the wireless signal received from the terminal station 3 through multiple antennas to the base station 4 through MIMO (Multiple Input Multiple Output).

[0030] The configuration of each device will be described.

[0031] The mobile relay station 2 includes N antennas 21 (N is an integer greater than or equal to 2), a terminal communication unit 22, a base station communication unit 24, and a plurality of antennas 25. The N antennas 21 are respectively referred to as antennas 21-1 to 21-N.

[0032] The terminal communication unit 22 includes a terminal signal reception processing unit 222 and N receiving units 221. The N receiving units 221 are referred to as receiving units 221-1 to 221-N. The receiving unit 221-n (n is an integer greater than or equal to 1 and less than or equal to N) receives a terminal uplink signal via the antenna 21-n.

[0033] The terminal signal reception processing unit 222 performs reception processing of the terminal uplink signal. The terminal signal reception processing unit 222 has a synthesis unit 224 and N terminal signal demodulation units 223. The N terminal signal demodulation units 223 are recorded as terminal signal demodulation units 223-1 to 223-N. The terminal signal demodulation unit 223-n (n is an integer greater than 1 and less than N) demodulates the terminal uplink signal received by the receiving unit 221-n, and outputs the demodulation result to the synthesis unit 224. The synthesis unit 224 outputs the demodulation information to the base station communication unit 24, and the demodulation information is the demodulation information obtained by synthesizing the demodulation results input from each of the terminal signal demodulation units 223-1 to 223-N.

[0034] The base station communication unit 24 relays the terminal uplink signal to the base station 4 through MIMO. The base station communication unit 24 includes a storage unit 241, a control unit 242, a transmission data modulation unit 243, and a MIMO transmission unit 244. The storage unit 241 stores in advance the weight of each transmission time of the base station downlink signal transmitted from each antenna 25. The transmission time can also be represented by, for example, the time elapsed from the transmission start timing. Based on the orbital information of the LEO satellite and the position of each antenna station 41, the weight of each transmission time is calculated. The orbital information of LEO is information that can obtain the position, speed, moving direction, etc. of the LEO satellite at any time. In addition, a fixed weight can also be used regardless of the transmission time.

[0035] The control unit 242 instructs the MIMO transmission unit 244 to read the weight of each transmission time from the storage unit 241. The transmission data modulation unit 243 inputs the demodulation information output by the synthesis unit 224 as transmission data, and modulates the input transmission data after converting it into parallel signals. The MIMO transmission unit 244 weights the modulated parallel signals using the weights instructed by the control unit 242, and generates a base station downlink signal transmitted from each antenna 25. The MIMO transmission unit 244 transmits the generated base station downlink signal from the antenna 25 by MIMO.

[0036] The terminal station 3 has a data storage unit 31, a transmission unit 32, and one or more antennas 33. The data storage unit 31 stores sensor data, etc. The transmission unit 32 reads the sensor data from the data storage unit 31 as terminal transmission data, and transmits the terminal uplink signal obtained by setting the read terminal transmission data from the antenna 33 by wireless. The transmission unit 32 transmits the signal, for example, through LPWA (Low Power Wide Area). In LPWA, there are 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. In addition, the transmission unit 32 can also transmit by time division multiplexing, OFDM (Orthogonal Frequency Division Multiplexing), MIMO, etc. with another terminal station 3. The transmission unit 32 determines the channel and transmission timing used by this station in the transmission of the terminal uplink signal by a method predetermined in the wireless communication method used. In addition, the transmission unit may perform beam forming of the signals transmitted by the plurality of antennas 33 by a method predetermined in the wireless communication method used.

[0037] The base station 4 includes a plurality of antenna stations 41 , a MIMO receiving unit 42 , a base station signal reception processing unit 43 , and a terminal signal reception processing unit 44 .

[0038] Antenna station 41 is arranged at a position separated from another antenna station 41 so that the difference in the arrival angle of the signals from the plurality of antennas 25 of mobile relay station 2 becomes large. Each antenna station 41 converts the base station downlink signal received from mobile relay station 2 into an electrical signal and outputs it to MIMO reception unit 42.

[0039] The MIMO receiving unit 42 collects base station downlink signals received from multiple antenna stations 41. The MIMO receiving unit 42 stores the weights for each reception time of the base station downlink signals received by each antenna station 41 based on the orbital information of the LEO satellite and the position of each antenna station 41. For example, the reception time can also be represented by the time elapsed from the reception start timing. The MIMO receiving unit 42 multiplies the base station downlink signal input from each antenna station 41 by the weight corresponding to the reception time of the base station downlink signal, and synthesizes the received signal multiplied by the weight. In addition, the same weight can also be used regardless of the reception time. The base station signal reception processing unit 43 demodulates and decodes the synthesized received signal to obtain demodulation information. The base station signal reception processing unit 43 outputs the demodulation information to the terminal signal reception processing unit 44.

[0040] The terminal signal reception processing unit 44 performs reception processing of the terminal uplink signal. The terminal signal reception processing unit 44 includes a terminal signal decoding unit 441. The terminal signal decoding unit 441 decodes the symbol of the terminal uplink signal indicated by the demodulation information, and obtains the terminal transmission data transmitted from the terminal station 3.

[0041] The operation of the wireless communication system 1 will be described.

[0042] Figure 2 1 is a flowchart showing the processing of the wireless communication system 1. The terminal station 3 obtains data detected by a sensor (not shown) provided outside or inside the terminal station 3 at any time, and writes the obtained data to the data storage unit 31 (step S111). The transmission unit 32 reads the sensor data from the data storage unit 31 as the terminal transmission data. The transmission unit 32 wirelessly transmits the terminal uplink signal obtained by setting the terminal transmission data from the antenna 33 at the transmission start timing obtained in advance based on the orbit information of the LEO satellite carrying the mobile relay station 2 (step S112). The terminal station 3 repeats the processing from step S111.

[0043] The receiving units 221-1 to 221-N of the mobile relay station 2 receive the terminal uplink signal transmitted from the terminal station 3 (step S121). Depending on the wireless communication method of the terminal station 3 of the transmission source, there is a case where the terminal uplink signal is received from only one terminal station 3 in time division multiplexing for the same frequency and a case where the terminal uplink signal is received from multiple terminal stations 3 at the same frequency at the same time. The terminal signal reception processing unit 222 demodulates the terminal uplink signal received in step S121 (step S122). Specifically, the terminal signal demodulation unit 223-n determines the wireless communication method based on the information inherent to the wireless communication method included in the terminal uplink signal received by the receiving unit 221-n. The receiving units 221-1 to 221-N demodulate the terminal uplink signal according to the determined wireless communication method and output the demodulation result to the synthesis unit 224. The synthesizing unit 224 outputs demodulation information obtained by adding and synthesizing the demodulation results input from the terminal signal demodulating units 223 - 1 to 223 -N to the transmission data modulating unit 243 .

[0044] Through this addition synthesis, the signal sent by the terminal station 3 is emphasized due to the existence of correlation, but the influence of the randomly added noise is reduced. Therefore, for the terminal uplink signal that the mobile relay station 2 receives from only one terminal station 3 at the same time, a diversity effect is obtained. In addition, for the terminal uplink signals that the mobile relay station 2 receives from multiple terminal stations 3 at the same time, it is equivalent to performing MIMO communication.

[0045] The transmission data modulation unit 243 inputs the demodulation information from the synthesis unit 224 as transmission data. The transmission data modulation unit 243 performs parallel conversion and then modulates the transmission data. The MIMO transmission unit 244 weights the transmission data modulated by the transmission data modulation unit 243 using the weight instructed by the control unit 242, and generates a base station downlink signal to be transmitted from each antenna 25. The MIMO transmission unit 244 transmits the generated base station downlink signal from the antenna 25 by MIMO (step S123). The mobile relay station 2 repeats the processing from step S121.

[0046] Each antenna station 41 of the base station 4 receives a base station downlink signal from the mobile relay station 2 (step S131). Each antenna station 41 outputs a received signal obtained by converting the received base station downlink signal into an electrical signal to the MIMO receiving unit 42. The MIMO receiving unit 42 synchronizes the timing of the received signals received from each antenna station 41. The MIMO receiving unit 42 multiplies the received signals received by each antenna station 41 by weights and adds them up. The base station signal receiving processing unit 43 demodulates the added received signal (step S132). The base station signal receiving processing unit 43 outputs demodulation information obtained by decoding the demodulated received signal to the terminal signal receiving processing unit 44.

[0047] The terminal signal decoding unit 441 of the terminal signal reception processing unit 44 decodes the symbol of the terminal uplink signal indicated by the demodulation information to obtain the terminal transmission data transmitted from the terminal station 3 (step S133). In addition, the terminal signal decoding unit 441 can also use a decoding method with a large calculation load such as SIC (Successive Interference Cancellation). The base station 4 repeats the processing from step S131.

[0048] According to this embodiment, the mobile relay station receives the terminal uplink signal of the terminal station by diversity reception or MIMO reception. Therefore, the link budget between the mobile relay station and the terminal station can be improved. In addition, the mobile relay station transmits the terminal uplink signal MIMO to the base station. Therefore, the mobile relay station can send the terminal uplink signals received from many terminal stations to the base station at once with large capacity and good quality.

[0049] (Second embodiment)

[0050] In this embodiment, the mobile relay station accumulates waveform data of the terminal uplink signal in advance, and wirelessly transmits the base station downlink signal obtained by setting the accumulated waveform data to the base station. This embodiment will be described mainly focusing on the differences from the first embodiment.

[0051] Figure 3 2 is a diagram showing the structure of a wireless communication system 1a according to the second embodiment. Figure 1 The same components of the wireless communication system 1 in the first embodiment are denoted by the same reference numerals, and their description is omitted. The wireless communication system 1a includes a mobile relay station 2a, a terminal station 3, and a base station 4a.

[0052] The mobile relay station 2a carried on the LEO satellite moves at high speed and communicates at the same time. Specifically, if observed on the ground, the mobile relay station 2a passes through the sky in about 10 minutes. Therefore, the time during which each terminal station 3 or base station 4a can communicate with the mobile relay station 2 with high quality is limited, and sometimes the time is different in the terminal station 3 and the base station 4a. In addition, for the terminal station 3, various wireless communication methods of various specifications can be used. Therefore, the mobile relay station 2a of this embodiment receives the terminal uplink signal in advance from the terminal station 3 within the coverage range of its current position during movement, and saves the waveform data of the received terminal uplink signal. At the timing when the base station 4a exists in the coverage range, the mobile relay station 2a wirelessly sends the base station downlink signal obtained after setting the waveform data of the terminal uplink signal to the base station 4a. The base station 4a demodulates the base station downlink signal received from the mobile relay station 2a to obtain the waveform data of the terminal uplink signal. The base station 4 a demodulates and decodes the terminal uplink signal indicated by the waveform data, thereby obtaining the terminal transmission data which is the data transmitted by the terminal station 3 .

[0053] The configuration of each device will be described.

[0054] The mobile relay station 2a is provided with N antennas 21 (N is an integer greater than or equal to 2), a terminal communication unit 22a, a data storage unit 23, a base station communication unit 24a, and a plurality of antennas 25. The terminal communication unit 22a has N receiving units 221 and N receiving waveform recording units 225. The N receiving waveform recording units 225 are recorded as receiving waveform recording units 225-1 to 225-N. The receiving waveform recording unit 225-n (n is an integer greater than or equal to 1 and less than or equal to N) samples the receiving waveform of the terminal uplink signal received by the receiving unit 221-n, and generates waveform data showing the value obtained by sampling. The receiving waveform recording unit 225-n writes the receiving waveform information into the data storage unit 23, in which the antenna identifier of the antenna 21-n, the receiving time of the terminal uplink signal in the antenna 21-n, and the generated waveform data are set. The antenna identifier is information for identifying the antenna 21-n. The data storage section 23 stores reception waveform information including waveform data of terminal uplink signals received by each of the antennas 21 - 1 to 21 -N.

[0055] The base station communication unit 24a includes a storage unit 241a, a control unit 242a, a transmission data modulation unit 243a, and a MIMO transmission unit 244. The storage unit 241a stores the transmission start timing calculated in advance based on the orbit information of the LEO satellite carrying the mobile relay station 2a and the position of the base station 4. In addition, the storage unit 241a stores in advance the weight of each transmission time of the base station downlink signal transmitted from each antenna 25. In addition, a fixed weight may be used regardless of the transmission time.

[0056] The control unit 242a controls the transmission data modulation unit 243a and the MIMO transmission unit 244 so that the reception waveform information is transmitted to the base station 4a at the transmission start timing stored in the storage unit 241a. In addition, the control unit 242a instructs the MIMO transmission unit 244 to read the weight of each transmission time from the storage unit 241a. The transmission data modulation unit 243a reads the reception waveform information from the data storage unit 23 as transmission data, and modulates the read transmission data after converting it into a parallel signal. The transmission data modulation unit 243a outputs the modulated transmission data to the MIMO transmission unit 244.

[0057] The base station 4a includes a plurality of antenna stations 41, a MIMO receiving unit 42, a base station signal receiving processing unit 43, and a terminal signal receiving processing unit 45. The terminal signal receiving processing unit 45 inputs the receiving waveform information decoded by the base station signal receiving processing unit 43, and performs receiving processing of the terminal uplink signal shown in the receiving waveform information. At this time, the terminal signal receiving processing unit 45 performs receiving processing through the wireless communication method used by the terminal station 3 in the transmission to obtain the terminal transmission data. The terminal signal receiving processing unit 45 includes a distribution unit 451, N terminal signal demodulation units 452, a synthesis unit 453, and a terminal signal decoding unit 454. The N terminal signal demodulation units 452 are respectively recorded as terminal signal demodulation units 452-1 to 452-N.

[0058] The distribution unit 451 reads the waveform data of the same receiving time from the received waveform information, and outputs the waveform data to the terminal signal demodulation units 452-1 to 452-N according to the antenna identifier associated with the read waveform data. That is, the distribution unit 451 outputs the waveform data associated with the antenna identifier of the antenna 21-n to the terminal signal demodulation unit 452-n. The terminal signal demodulation units 452-1 to 452-N demodulate the waveform data respectively, and output the symbols obtained by demodulation to the synthesis unit 453. The terminal signal demodulation unit 452-n can also demodulate after processing the signal shown in the waveform data, and the processing is to compensate for the Doppler shift of the terminal uplink signal received by the antenna 21-n of the mobile relay station 2. The Doppler shift borne by the terminal uplink signal received by each antenna 21-n is calculated in advance based on the position of the terminal station 3 and the orbital information of the LEO carrying the mobile relay station 2a. The combining unit 453 adds and combines the symbols input from the terminal signal demodulation units 452-1 to 452-N, and outputs the sum to the terminal signal decoding unit 454. The terminal signal decoding unit 454 decodes the summed symbols to obtain the terminal transmission data transmitted from the terminal station 3.

[0059] The operation of the wireless communication system 1a will be described.

[0060] Figure 4 1 is a flowchart showing the processing of the wireless communication system 1a when an uplink signal is transmitted from the terminal station 3. Figure 2 The same reference numerals are used for the same processing steps as those in the first embodiment. Figure 2 The processing is the same as the processing from step S111 to step S112 in the processing flow of the first embodiment shown.

[0061] The receiving units 221-1 to 221-N of the mobile relay station 2a receive the terminal uplink signal transmitted from the terminal station 3 (step S121). The reception waveform recording unit 225-n writes the reception waveform information that associates the waveform data representing the waveform of the terminal uplink signal received by the receiving unit 221-n, the reception time, and the antenna identifier of the antenna 21-n to the data storage unit 23 (step S221). The mobile relay station 2a repeats the processing from step S121.

[0062] Figure 5 2 is a flowchart showing the processing of the wireless communication system 1a when a base station downlink signal is transmitted from the mobile relay station 2a. Figure 5 In, with Figure 2 The same processing as that shown in the flowchart of the first embodiment is denoted by the same reference numerals.

[0063] When the control unit 242a of the base station communication unit 24a of the mobile relay station 2a detects that it is the transmission start timing stored in the storage unit 241a, it instructs the transmission data modulation unit 243a and the MIMO transmission unit 244 to transmit the reception waveform information (step S311). The transmission data modulation unit 243a reads the reception waveform information stored in the data storage unit 23 as transmission data, and modulates the read transmission data after parallel conversion. The MIMO transmission unit 244 weights the transmission data modulated by the transmission data modulation unit 243a using the weight instructed by the control unit 242a, and generates a base station downlink signal to be transmitted from each antenna 25. The MIMO transmission unit 244 transmits the generated base station downlink signals from the antenna 25 by MIMO (step S312). The mobile relay station 2 repeats the processing from step S311.

[0064] and Figure 2 Similarly to the first embodiment shown, the base station 4a receives the base station downlink signal from the mobile relay station 2a through MIMO (step S131). That is, each antenna station 41 converts the base station downlink signal received from the mobile relay station 2a into an electrical signal and outputs the received signal to the MIMO receiving unit 42. The MIMO receiving unit 42 synchronizes the timing of the received signals received from each antenna station 41. The MIMO receiving unit 42 multiplies the received signals received by each antenna station 41 by weights and adds them up. The base station signal receiving processing unit 43 demodulates the added received signal (step S321). The base station signal receiving processing unit 43 outputs the received waveform information obtained by decoding the demodulated received signal to the terminal signal receiving processing unit 45.

[0065] The terminal signal reception processing unit 45 performs reception processing of the terminal uplink signal indicated by the reception waveform information (step S322). Specifically, the allocation unit 451 reads the waveform data having the same reception time from the reception waveform information, and outputs the waveform data to the terminal signal demodulation units 452-1 to 452-N according to the antenna identifier associated with the read waveform data. The terminal signal demodulation units 452-1 to 452-N respectively determine the wireless communication method used by the terminal station 3 in the transmission of the terminal uplink signal based on the information inherent to the wireless communication method included in the received signal represented by the waveform data. The terminal signal demodulation units 452-1 to 452-N demodulate the received signal represented by the waveform data according to the determined wireless communication method, and output the symbols obtained by demodulation to the synthesis unit 453.

[0066] The synthesizer 453 performs additive synthesis on the symbols input from the terminal signal demodulators 452-1 to 452-N. Through additive synthesis, the signal sent by the terminal station 3 is emphasized due to the existence of correlation, but the influence of the randomly added noise is reduced. Therefore, for the terminal uplink signal received by the mobile relay station 2a from only one terminal station 3 at the same time, a diversity effect is obtained. In addition, for the terminal uplink signal received by the mobile relay station 2a from multiple terminal stations 3 at the same time, it is equivalent to performing MIMO communication. The synthesizer 453 outputs the symbols after additive synthesis to the terminal signal decoding unit 454. The terminal signal decoding unit 454 decodes the symbols after additive synthesis by the synthesizer 453 through the determined wireless communication method to obtain the terminal transmission data sent from the terminal station 3. In addition, the terminal signal decoding unit 454 can also use a decoding method with a large calculation load such as SIC. The base station 4a repeats the processing from step S321.

[0067] According to this embodiment, similarly to the first embodiment, the mobile relay station receives the terminal uplink signal received from the terminal station by diversity reception or MIMO reception. Therefore, the link budget between the mobile relay station and the terminal station can be improved. In addition, the mobile relay station transmits the information of the received waveform of the terminal uplink signal to the base station by MIMO. Therefore, during the period when the base station is included in the area where the mobile relay station can communicate, the received waveform of the terminal uplink received from many terminal stations can be sent together with large capacity and good quality.

[0068] In addition, as described above, in the present embodiment, the mobile relay station does not demodulate the terminal uplink signal received from the terminal station, but stores and accumulates the information of the received signal waveform, and performs MIMO transmission at a timing when communication with the base station can be performed. The base station performs reception processing such as demodulation / decoding on the terminal uplink signal represented by the received signal waveform in the mobile relay station. Therefore, the non-reproduction relay method that does not depend on the communication method can be applied to a wireless communication system using a low-orbit satellite. In addition, since non-reproduction relaying is performed, it is not necessary for the mobile relay station to install the wireless communication method used in the terminal station. For example, even if a terminal station that communicates in a new wireless communication method is added, it is not necessary to change the mobile relay station, as long as the change of the wireless communication method is added to the base station set on the ground. Therefore, it is possible to accommodate various IoT systems at the same time, and it is also possible to easily respond to updates to the IoT system. Furthermore, since the large Doppler shift that each terminal station receives can be processed at the base station instead of at the mobile relay station, it is not necessary to install a complicated nonlinear calculation for compensating for the Doppler shift in the mobile relay station.

[0069] (Third embodiment)

[0070] In the above-mentioned second embodiment, the terminal uplink signal is demodulated and decoded in the base station. In this embodiment, the terminal uplink signal is demodulated and decoded in the mobile relay device. This embodiment is described mainly focusing on the differences from the first and second embodiments.

[0071] Figure 6 1 is a diagram showing the structure of a wireless communication system 1b according to the second embodiment. Figure 1 The wireless communication system 1 in the first embodiment shown and Figure 3 The same components as those of the wireless communication system 1a in the second embodiment are denoted by the same reference numerals, and their description is omitted. The wireless communication system 1b includes a mobile relay station 2b, a terminal station 3, and a base station 4b.

[0072] The mobile relay station 2 b includes antennas 21 - 1 to 21 -N (N is an integer equal to or greater than 2), a terminal communication unit 22 b , a data storage unit 23 , a base station communication unit 24 a , and a plurality of antennas 25 .

[0073] The terminal communication unit 22 b includes receiving units 221 - 1 to 221 -N, a terminal signal reception processing unit 222 b , and a data recording unit 227 .

[0074] The terminal signal reception processing unit 222b performs reception processing of the terminal uplink signal to obtain the terminal transmission data. The terminal signal reception processing unit 222b has N terminal signal demodulation units 223, a synthesis unit 224, and a terminal signal decoding unit 226. The synthesis unit 224 adds and synthesizes the symbols as the demodulation results respectively input from the terminal signal demodulation units 223-1 to 223-N and outputs them to the terminal signal decoding unit 226. The terminal signal decoding unit 226 decodes the symbols added and synthesized by the synthesis unit 224 to obtain the terminal transmission data sent from the terminal station 3.

[0075] The data recording unit 227 writes the terminal transmission data decoded by the terminal signal decoding unit 226 to the data storage unit 23. The data storage unit 23 stores the terminal transmission data transmitted by each terminal station 3. The transmission data modulation unit 243a of the base station communication unit 24a reads the terminal transmission data from the data storage unit 23 as transmission data.

[0076] The base station 4b includes a plurality of antenna stations 41, a MIMO receiving unit 42, and a base station signal receiving processing unit 43. The base station signal receiving processing unit 43 demodulates and decodes the received signal synthesized in the MIMO receiving unit 42 to obtain terminal transmission data.

[0077] The operation of the wireless communication system 1b will be described.

[0078] Figure 7 2 is a flowchart showing the processing of the wireless communication system 1b in the case where an uplink signal is transmitted from the terminal station 3. Figure 7 In, with Figure 2 The same processing as that shown in the flowchart of the first embodiment is denoted by the same reference numerals.

[0079] The processing of the terminal station 3 in steps S111 to S112 is the same as Figure 2 The same as the first embodiment shown. As in the first embodiment, the receiving units 221-1 to 221-N of the mobile relay station 2b receive the terminal uplink signal sent from the terminal station 3 (step S121). The terminal signal reception processing unit 222b performs reception processing of the terminal uplink signal received in step S121 (step S411). Specifically, the terminal signal demodulation unit 223-n determines the wireless communication method based on the information inherent to the wireless communication method included in the terminal uplink signal received by the receiving unit 221-n. The receiving units 221-1 to 221-N demodulate the terminal uplink signal according to the determined wireless communication method, and output the symbols obtained by demodulation to the synthesis unit 224. The synthesis unit 224 performs addition synthesis on the symbols input from the terminal signal demodulation units 223-1 to 223-N respectively. The synthesis unit 224 outputs the symbols after addition synthesis to the terminal signal decoding unit 226. The terminal signal decoding unit 226 decodes the added and synthesized symbols to obtain the terminal transmission data transmitted from the terminal station 3. The data recording unit 227 writes the terminal transmission data obtained by the terminal signal decoding unit 226 decoding the symbols into the data storage unit 23 (step S412).

[0080] Figure 8 2 is a flowchart showing the processing of the wireless communication system 1b in the case where a base station downlink signal is transmitted from the mobile relay station 2b. Figure 8 In, with Figure 2 The same processing as that shown in the flowchart of the first embodiment is denoted by the same reference numerals.

[0081] When the control unit 242a of the base station communication unit 24a of the mobile relay station 2b detects that the transmission start timing stored in the storage unit 241a has arrived, it instructs the transmission data modulation unit 243a and the MIMO transmission unit 244 to transmit the terminal transmission data (step S511). The transmission data modulation unit 243a reads the terminal transmission data stored in the data storage unit 23 as transmission data, and modulates the read transmission data after parallel conversion. The MIMO transmission unit 244 weights the transmission data modulated by the transmission data modulation unit 243a using the weight instructed by the control unit 242a, and generates a base station downlink signal as a transmission signal transmitted from each antenna 25. The MIMO transmission unit 244 transmits the generated base station downlink signals from the antenna 25 by MIMO (step S512). The mobile relay station 2b repeats the processing from step S511.

[0082] As in the first embodiment, the base station 4b receives the base station downlink signal from the mobile relay station 2b by MIMO (step S131). That is, each antenna station 41 converts the base station downlink signal received from the mobile relay station 2b into an electrical signal and outputs the received signal to the MIMO receiving unit 42. The MIMO receiving unit 42 synchronizes the timing of the received signals received from each antenna station 41. The MIMO receiving unit 42 multiplies the received signals received by each antenna station 41 by weights and adds them up. The base station signal reception processing unit 43 demodulates the added received signal and decodes the demodulated received signal to obtain the terminal transmission data (step S521). The base station 4b repeats the processing from step S131.

[0083] According to the above-described implementation mode, the mobile relay station can receive the terminal uplink signal sent by the terminal station through diversity reception or MIMO reception. Therefore, the link budget of the uplink signal from the terminal station can be improved. In addition, the mobile relay station transmits the data received from the terminal station to the base station through multiple antennas MIMO. Therefore, the data collected from multiple terminal stations can be sent together in a short time with good quality. Therefore, even if the area where communication is possible moves with the movement of the relay device, the data received from the communication device can be relayed to other communication devices.

[0084] Furthermore, in the above-described embodiment, the case where the mobile object carrying the mobile relay station is a LEO satellite is described, but it may also be another flying object flying in the sky such as a geostationary satellite, a drone, or a HAPS.

[0085] According to the above-mentioned embodiment, the wireless communication system has a first communication device, a second communication device and a mobile relay device. For example, the first communication device is the terminal station 3 in the embodiment, the second communication device is the base station 4, 4a, 4b in the embodiment, and the relay device is the mobile relay station 2, 2a, 2b in the embodiment.

[0086] The relay device includes a receiving unit and a sending unit. For example, the receiving unit is the terminal communication unit 22, 22a, 22b in the embodiment, and the sending unit is the base station communication unit 24, 24a in the embodiment. The receiving unit receives data wirelessly sent by the first communication device through multiple first antennas. For example, the first antenna is the antenna 21 in the embodiment. The sending unit wirelessly sends the data received by the receiving unit from the multiple second antennas to the second communication device. For example, the second antenna is the antenna 25 in the embodiment. The second communication device includes a relay data receiving unit. The relay data receiving unit receives data wirelessly sent by the relay device through multiple third antennas. The third antenna is the antenna station 41 in the embodiment.

[0087] The relay device may further include a storage unit for storing data received by the receiving unit. The storage unit is the data storage unit 23 in the embodiment. The transmitting unit transmits the data stored in the storage unit from the second antenna via wireless at a timing when communication with the second communication device is possible.

[0088] In addition, the receiving unit may also receive a wireless first signal obtained after setting the data through multiple first antennas. For example, the first signal is a terminal uplink signal in the embodiment. The storage unit stores waveform data showing the waveform of the first signal received by each of the multiple first antennas. The sending unit sends a second signal showing the waveform data stored in the storage unit from multiple second antennas through wireless. For example, the second signal is a base station downlink signal in the embodiment. The relay data receiving unit has a second signal receiving unit, a second signal receiving processing unit, and a first signal receiving processing unit. The second signal receiving unit receives the second signal sent by the relay device through wireless through multiple third antennas. The second signal receiving processing unit synthesizes the second signal received by the first signal receiving unit through each of the multiple third antennas, performs reception processing of the synthesized second signal, and obtains waveform data corresponding to each of the multiple first antennas. The first signal receiving processing unit demodulates the first signal represented by the waveform data obtained by the second signal receiving processing unit, decodes the synthesized signal, and obtains data set as the first signal by the first communication device, wherein the synthesized signal is a signal obtained by synthesizing the demodulation results of the multiple first antennas. For example, the second signal receiving unit is the antenna station 41 and the MIMO receiving unit 42 in the embodiment, the second signal receiving processing unit is the base station signal receiving processing unit 43 in the embodiment, and the first signal receiving processing unit is the terminal signal receiving processing unit 45. In addition, the first signal processing unit can perform receiving processing in a variety of wireless ways.

[0089] The receiving unit may also receive a wireless first signal obtained after setting data from the first communication device through multiple first antennas, and perform reception processing on the received first signal to obtain data. The transmitting unit transmits a second signal obtained after setting data stored in the storage unit through multiple second antennas wirelessly. The relay data receiving unit has a second signal receiving unit and a second signal reception processing unit. The second signal receiving unit receives the second signal wirelessly transmitted by the relay device through multiple third antennas. The second signal reception processing unit synthesizes the second signals received by the first signal receiving unit through each of the multiple third antennas, performs reception processing on the synthesized second signal, and obtains data set as the first signal by the first communication device.

[0090] As mentioned above, the embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to the embodiment and includes designs and the like within the scope that does not depart from the gist of the present invention.

[0091] Explanation of symbols

[0092] 1, 1a, 1b ... wireless communication system,

[0093] 2, 2a, 2b... mobile relay station,

[0094] 3...Terminal Station,

[0095] 4, 4a, 4b...base station,

[0096] 21-1 to 21-N...antennas,

[0097] 22, 22a, 22b ... terminal communication unit,

[0098] 23……Data storage unit,

[0099] 24, 24a……Base station communication unit,

[0100] 25...antenna,

[0101] 31……Data storage unit,

[0102] 32……Sending Department,

[0103] 33...antenna,

[0104] 41...Antenna Station,

[0105] 42……MIMO receiving unit,

[0106] 43……Base station signal receiving and processing unit,

[0107] 44, 45, 222, 222b ... terminal signal receiving and processing unit,

[0108] 221-1 to 221-N ... receiving unit,

[0109] 223-1 to 223-N, 452-1 to 452-N ... terminal signal demodulation unit,

[0110] 224, 453...Synthetic Department,

[0111] 225-1 to 225-N ... receiving waveform recording unit,

[0112] 226, 441, 454...Terminal signal decoding unit,

[0113] 227...Data Recording Department,

[0114] 241, 241a ... storage unit,

[0115] 242, 242a……Control unit,

[0116] 243, 243a ... transmission data modulation unit,

[0117] 244……MIMO transmission unit,

[0118] 451……Distribution Department.

Claims

1. A wireless communication system comprising a first communication device, a second communication device and a mobile relay device, The relay device comprises: a receiving unit, which receives data wirelessly transmitted by the first communication device through a plurality of first antennas; a storage unit that stores the data received by the receiving unit; and a transmitting unit that wirelessly transmits the data stored in the storage unit from the plurality of second antennas to the second communication device, The second communication device comprises: a relay data receiving unit, which receives the data wirelessly transmitted by the relay device through a plurality of third antennas, The receiving unit receives a wireless first signal obtained after setting the data through a plurality of first antennas, The storage unit stores waveform data indicating waveforms of the first signals received by each of the plurality of first antennas. The transmitting unit transmits a second signal indicating the waveform data stored in the storage unit from the plurality of second antennas by wireless. The relay data receiving unit comprises: a second signal receiving unit, which receives the second signal wirelessly transmitted by the relay device through the plurality of third antennas; a second signal receiving processing unit that synthesizes the second signals received by the second signal receiving unit through each of the plurality of third antennas, performs reception processing on the synthesized second signals, and obtains the waveform data corresponding to each of the plurality of first antennas; and A first signal receiving and processing unit demodulates the first signal represented by the waveform data obtained by the second signal receiving and processing unit for each of the plurality of first antennas, and decodes the synthesized signal to obtain the data, wherein the synthesized signal is a signal obtained by synthesizing the demodulation results for the plurality of first antennas.

2. The wireless communication system according to claim 1, wherein: The transmitting unit wirelessly transmits the data stored in the storage unit from the plurality of second antennas at a timing when communication with the second communication device is possible.

3. The wireless communication system according to claim 1 or claim 2, wherein: The first signal reception processing unit can perform the reception processing in a variety of wireless methods.

4. The wireless communication system according to claim 1 or claim 2, wherein: The flying object flying in the sky is equipped with the relay device. The first communication device and the second communication device are set on the earth.

5. The wireless communication system according to claim 4, wherein: The flying object is a low-orbit satellite.

6. A relay device, which is the relay device in a wireless communication system having a first communication device, a second communication device, and a mobile relay device, the relay device comprising: a receiving unit, which receives data wirelessly transmitted by the first communication device through a plurality of first antennas; a storage unit that stores the data received by the receiving unit; and a transmitting unit that wirelessly transmits the data stored in the storage unit from the plurality of second antennas to the second communication device, and the second communication device receives the data using the plurality of third antennas, The receiving unit receives a wireless first signal obtained after setting the data through a plurality of first antennas, The storage unit stores waveform data indicating waveforms of the first signals received by each of the plurality of first antennas. The transmitting unit transmits a second signal indicating the waveform data stored in the storage unit from the plurality of second antennas by wireless. After synthesizing the second signals received by each of the plurality of third antennas, the second communication device performs reception processing to obtain the waveform data corresponding to each of the plurality of first antennas, demodulates the first signal represented by the obtained waveform data, and decodes the synthesized signal to obtain the data, wherein the synthesized signal is a signal obtained by synthesizing the demodulation results of the plurality of first antennas.

7. A wireless communication method, which is a wireless communication method performed by a wireless communication system having a first communication device, a second communication device, and a mobile relay device, the wireless communication method comprising: A receiving step, wherein the relay device receives data wirelessly sent by the first communication device through a plurality of first antennas; a storing step, wherein the relay device stores the data received in the receiving step in a storage unit; a sending step, wherein the relay device wirelessly sends the data stored in the storage unit from a plurality of second antennas to the second communication device; as well as a relay data receiving step, wherein the second communication device receives the data transmitted wirelessly in the transmitting step through a plurality of third antennas, In the receiving step, the relay device receives a wireless first signal obtained by setting the data through a plurality of first antennas. In the storing step, the relay device stores in the storage unit waveform data indicating waveforms of the first signals received by each of the plurality of first antennas. In the transmitting step, the relay device transmits a second signal indicating the waveform data stored in the storage unit from the plurality of second antennas by wireless. The relay data receiving step comprises: A second signal receiving step, wherein the second communication device receives the second signal wirelessly transmitted by the relay device through the plurality of the third antennas; a second signal receiving and processing step, wherein the second communication device synthesizes the second signals received by each of the plurality of third antennas in the second signal receiving step, performs reception processing on the synthesized second signal, and obtains the waveform data corresponding to each of the plurality of first antennas; as well as In the first signal receiving and processing step, the second communication device demodulates the first signal represented by the waveform data obtained for each of the plurality of first antennas in the second signal receiving and processing step, and decodes the synthesized signal to obtain the data, wherein the synthesized signal is a signal obtained by synthesizing the demodulation results for the plurality of first antennas.

8. A wireless communication method, which is a wireless communication method performed by a relay device in a wireless communication system having a first communication device, a second communication device, and a mobile relay device, the wireless communication method comprising: A receiving step, which receives data wirelessly sent by the first communication device through a plurality of first antennas; a storing step, wherein the relay device stores the data received in the receiving step in a storage unit; as well as a sending step, wherein the relay device wirelessly sends the data stored in the storage unit from a plurality of second antennas to the second communication device, and the second communication device receives the data using a plurality of third antennas, In the receiving step, a wireless first signal obtained by setting the data is received through a plurality of first antennas. In the storing step, waveform data showing waveforms of the first signals received by each of the plurality of first antennas is stored in the storage unit. In the transmitting step, a second signal indicating the waveform data stored in the storage unit is transmitted wirelessly from the plurality of second antennas. After synthesizing the second signals received by each of the plurality of third antennas, the second communication device performs reception processing to obtain the waveform data corresponding to each of the plurality of first antennas, demodulates the first signal represented by the obtained waveform data, and decodes the synthesized signal to obtain the data, wherein the synthesized signal is a signal obtained by synthesizing the demodulation results of the plurality of first antennas.

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