WO2022137397A1 - 無線通信システム、中継装置、無線通信方法及びプログラム - Google Patents
無線通信システム、中継装置、無線通信方法及びプログラム Download PDFInfo
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- 238000000034 method Methods 0.000 title claims description 104
- 230000005540 biological transmission Effects 0.000 claims abstract description 329
- 230000001678 irradiating effect Effects 0.000 claims description 6
- 238000012545 processing Methods 0.000 description 73
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- 230000007613 environmental effect Effects 0.000 description 23
- 238000012986 modification Methods 0.000 description 22
- 230000004048 modification Effects 0.000 description 22
- 238000010586 diagram Methods 0.000 description 21
- 238000005259 measurement Methods 0.000 description 14
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- 238000005070 sampling Methods 0.000 description 7
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- 238000013480 data collection Methods 0.000 description 3
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- 230000006866 deterioration Effects 0.000 description 2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
Definitions
- the present invention relates to a wireless communication system, a relay device, a wireless communication method and a program.
- the IoT (Internet of Things) system that realizes various applications by connecting a small terminal device to the Internet is widespread.
- IoT Internet of Things
- a system is known in which a plurality of IoT terminals sense environmental information such as temperature, room temperature, acceleration, and luminosity and transmit it as a wireless signal, and the cloud side collects the environmental information.
- IoT terminals equipped with various sensors are installed in various places. It is also envisioned that IoT will be used to collect data from locations where base stations are difficult to install (eg, buoys, ships, and mountainous areas at sea).
- a wireless system that performs wireless communication between multiple communication devices on the ground and the relay station using a communication satellite or an unmanned aerial vehicle (UAV) as a relay station.
- a wireless system using a communication satellite as a relay station a low earth orbit satellite (LEO: Low Earth Orbit) orbiting a low earth orbit around 1,000 km is used, and a geostationary satellite (GEO:) orbiting an altitude of 36,000 km. Geostationary Orbit) may be used.
- Low earth orbit satellites have a shorter signal propagation distance than geostationary satellites. Therefore, when a low earth orbit satellite is used as a relay station, it is possible to realize communication with low delay and low propagation loss.
- the configuration of the high frequency circuit provided in the low earth orbit satellite or the terrestrial communication device becomes simple.
- low earth orbit satellites orbit over the earth, so the direction in which low earth orbit satellites are viewed from ground communication devices constantly changes.
- the visible time per orbit of a low earth orbit satellite in each communication device on the ground is several minutes. Therefore, the time zone in which the low earth orbit satellite and each communication device on the ground can communicate is limited.
- LPWA Low Power Wide Area
- LPWA Low Power Wide Area
- a satellite IoT system including a communication satellite that collects data from an IoT terminal using LPWA is being studied.
- the propagation distance of a radio signal for communication between a communication satellite and a terrestrial communication device is longer than that for wireless communication in which direct communication is performed between a plurality of terrestrial communication devices.
- LPWA can be applied.
- Non-Patent Document 1 describes a method of avoiding a collision at the time of data reception in a base station by autonomously distributed transmission schedule control of terminals in an LPWA network.
- the transmission timing of each terminal is represented by a phase oscillator model.
- Each terminal waits for the phase of its own terminal to become 0 before transmitting data. This method avoids data collision by realizing a reverse phase synchronization state in which the phases of all terminals are evenly spaced from each other.
- the relay station irradiates the beam into the communication target area, and receives the terminal uplink signal from each IoT terminal located in the irradiation range of the beam.
- each IoT terminal may repeat data transmission to the base station a plurality of times. That is, many terminal uplink signals may be transmitted from the IoT terminal. Further, since a large number of IoT terminals transmit data, there may be a transmission opportunity exceeding the number of slots. As described above, in the IoT system, the degree of communication congestion may fluctuate.
- each IoT terminal simply uniformly transmits a terminal uplink signal at different timings given to each IoT terminal. Further, the method does not control the transmission schedule according to the occupancy status of the base station. Therefore, in the method described in Non-Patent Document 1, when the degree of congestion of communication fluctuates, data collision may occur and the reliability of communication may decrease.
- an object of the present invention is to provide a wireless communication system, a relay device, a wireless communication method and a program capable of realizing a wide coverage without increasing the number of beams more than necessary.
- One aspect of the present invention includes one or more first communication devices located in one or more small areas among a plurality of small areas that divide a communication target area, a relay device, and a second communication device.
- the relay device has one or more so as to scan a plurality of small areas with the beam while irradiating the communication target area with one or more beams having an irradiation range narrower than the communication target area.
- An antenna driving unit that drives the antenna, a receiving unit that acquires a first radio signal transmitted from the first communication device located in the irradiation range from the antenna, and a first unit corresponding to the first radio signal. 2
- It is a wireless communication system including a transmission unit that transmits a wireless signal to the second communication device.
- one or more first communication devices and a second communication device located in one or more small areas among a plurality of small areas that divide the communication target area can be moved.
- the relay device scans a plurality of small areas with the beam while irradiating the communication target area with one or more beams having an irradiation range narrower than the communication target area.
- An antenna driving unit that drives one or more antennas, a receiving unit that acquires a first radio signal transmitted from the first communication device located in the irradiation range from the antenna, and the first radio signal.
- one aspect of the present invention includes one or more first communication devices, a relay device, and a second communication device located in one or more small areas among a plurality of small areas that divide a communication target area.
- One or more antennas are driven so as to scan with a beam, and a first radio signal transmitted from the first communication device located in the irradiation range is acquired from the antenna and responds to the first radio signal.
- This is a wireless communication method for transmitting a second wireless signal to the second communication device.
- one aspect of the present invention is a program for operating a computer as a relay device of the above wireless communication system.
- FIG. 1 is a configuration diagram of a wireless communication system 1 according to the first embodiment.
- the wireless communication system 1 has a mobile relay station 2, a terminal station 3, and a base station 4.
- the number of each of the mobile relay station 2, the terminal station 3, and the base station 4 included in the wireless communication system 1 is arbitrary, but it is assumed that the number of the terminal stations 3 is large.
- the wireless communication system 1 is a communication system that transmits information that does not require immediacy.
- the information transmitted from each of the plurality of terminal stations 3 is transmitted via the mobile relay station 2 and collected by the base station 4.
- the mobile relay station 2 is an example of a relay device mounted on a mobile body and in which a communicable area moves with the passage of time.
- the mobile relay station 2 is provided in, for example, a LEO (Low Earth Orbit) satellite.
- the altitude of the LEO satellite is 2000 km or less, and it orbits over the earth in about 1.5 hours.
- the terminal station 3 and the base station 4 are installed on the earth such as on the ground or at sea.
- the plurality of terminal stations 3 exist in different places from each other.
- the terminal station 3 is, for example, an IoT terminal.
- the terminal station 3 collects data such as environmental data detected by the sensor and transmits the data to the mobile relay station 2 by a wireless signal. In the figure, only two terminal stations 3 are shown.
- the mobile relay station 2 receives data transmitted from each of the plurality of terminal stations 3 by wireless signals while moving over the earth.
- the mobile relay station 2 accumulates these received data, and wirelessly transmits the accumulated data to the base station 4 at a timing when communication with the base station 4 is possible.
- the base station 4 receives the data collected by the terminal station 3 from the mobile relay station 2.
- the mobile relay station 2 it is conceivable to use a geostationary satellite or a relay station mounted on an unmanned aerial vehicle such as a drone or HAPS (High Altitude Platform Station).
- a relay station mounted on a geostationary satellite although the coverage area (footprint) on the ground is wide, the link budget for the IoT terminal installed on the ground is very small due to the high altitude.
- the link budget is high, but the coverage area is narrow.
- drones require batteries and HAPS require solar panels.
- the mobile relay station 2 is mounted on the LEO satellite as an example. Therefore, in addition to keeping the link budget within the limit, the LEO satellite has no air resistance and consumes less fuel because it orbits outside the atmosphere.
- the footprint is larger than when a relay station is mounted on a drone or HAPS.
- the mobile relay station 2 mounted on the LEO satellite communicates while moving at high speed, the time during which each terminal station 3 or base station 4 can communicate with the mobile relay station 2 is limited. Specifically, when the terminal station 3 sees the mobile relay station 2 from the ground, the mobile relay station 2 passes over the sky in about 10 minutes. Further, a wireless communication method having various specifications is used for the terminal station 3. Therefore, the mobile relay station 2 on the move receives the terminal uplink signal from the terminal station 3 within the coverage at the current position, and stores the waveform data of the received terminal uplink signal. The mobile relay station 2 wirelessly transmits a base station downlink signal including waveform data of the terminal uplink signal to the base station 4 at the timing when the base station 4 is present in the coverage.
- the base station 4 demodulates the base station downlink signal received from the mobile relay station 2 to obtain waveform data of the terminal uplink signal.
- the base station 4 obtains terminal transmission data which is the data transmitted by the terminal station 3 by demodulating and decoding the terminal uplink signal represented by the waveform data.
- the mobile relay station 2 and the terminal station 3 perform wireless communication using LPWA as an example.
- Each terminal station 3 may transmit the same terminal uplink signal to the mobile relay station 2 a plurality of times in order to ensure the reliability of communication. Further, as described above, it is assumed that the number of terminal stations 3 is large. With such a configuration, the amount of data transmitted from the terminal station 3 to the mobile relay station 2 may increase, and the communication band may become tight.
- the diameter of the beam irradiated to the ground by the mobile relay station 2 is narrowed in order to prevent the communication band from becoming tight.
- the number of IoT terminals that can communicate at the same time decreases, so it is possible to prevent data collisions and suppress deterioration of communication reliability. .. Further, since the communication target area is scanned by the beam, a wide coverage can be realized without increasing the number of beams more than necessary.
- Each terminal station 3 transmits a terminal uplink signal including predetermined data such as environmental data to the mobile relay station 2.
- Each terminal station 3 may transmit a terminal uplink signal including predetermined data such as environmental data and position information indicating the position of its own station to the mobile relay station 2.
- the terminal station 3 is provided with a positioning device such as a GPS (Global Positioning System) receiver, and generates position information indicating the position of its own station.
- GPS Global Positioning System
- the mobile relay station 2 receives the terminal uplink signal from each terminal station 3.
- the mobile relay station 2 measures the degree of communication congestion.
- the degree of communication congestion is, for example, the number of terminal uplink communication accesses (frequency of terminal uplink signal transmission per unit time) per unit time from a plurality of terminal stations 3 in the mobile relay station 2, or terminal up. It is the degree represented by RSSI (Received Signal Strength Indicator) of the frequency band of link communication.
- RSSI Receiveived Signal Strength Indicator
- the mobile relay station 2 may extract position information indicating the position of the terminal station 3 from each terminal uplink signal.
- the mobile relay station 2 changes the scanning speed of the beam scanning the communication target area based on the degree of communication congestion.
- the mobile relay station 2 may change the scanning speed of the beam scanning the communication target area based on the degree of communication congestion and the position information indicating the position of each of the plurality of terminal stations 3.
- the mobile relay station 2 changes the scanning speed so that the degree of communication congestion for each small area that divides the communication target area is made uniform in the plurality of small areas.
- the homogenization referred to here may include an error within a predetermined allowable range, and does not mean that the degree of congestion of communication is completely equal in a plurality of small areas.
- the diameter of the beam is determined, for example, based on the trade-off between the number of terminal stations 3 accommodated and signal interference.
- the shorter the diameter of the beam the more the irradiation range of the beam is spotted), the higher the signal gain, but the number of terminal stations 3 (terminal stations 3 that can be connected to the mobile relay station 2 at the same time) accommodated. Decreases.
- the diameter of each small area that divides the communication target area may be predetermined, for example, to a length substantially equal to the diameter of the beam. That is, the shape and width of the small area and the shape and width of the irradiation range of the beam may be substantially the same.
- the mobile relay station 2 positions a control signal (hereinafter referred to as “transmission permission signal”) indicating that data such as environmental data is permitted to be transmitted to its own mobile relay station 2 within the irradiation range of the beam. It is transmitted to the terminal station 3 which is operating.
- the mobile relay station 2 transmits a terminal downlink signal including a transmission permission signal to a terminal station 3 on the ground while scanning a communication target area with a beam whose irradiation range is spotted.
- the transmission permission signal may further include area information of a small area irradiated with the beam.
- the terminal station 3 When the terminal station 3 receives the transmission permission signal (when its own station is located in the irradiation range of the narrow beam), the terminal station 3 starts transmitting the terminal uplink signal to the mobile relay station 2. When the terminal station 3 does not receive the transmission permission signal (when its own station is not located in the irradiation range of the narrow beam), the terminal station 3 does not transmit the terminal uplink signal to the mobile relay station 2 and stands by. do.
- the terminal station 3 includes data such as environmental data and position information indicating the position of its own station in the terminal uplink signal transmitted to the mobile relay station 2.
- the mobile relay station 2 may derive (predict) the degree of congestion in the next round of the mobile relay station 2 by using the position information of the terminal station 3 in the current round.
- the terminal station 3 may store the longitude and latitude of the range of the small area in advance as area information.
- the terminal station 3 may recognize the area information of the small area including the position of the own station based on the longitude and the latitude of the position of the own station.
- the terminal station 3 has a terminal uplink signal to the mobile relay station 2 when the small area based on the area information included in the transmission permission signal and the small area including the position of the own station match. Start sending.
- the terminal station 3 When the terminal station 3 can recognize the small area including the position of the own station, the terminal station 3 indicates the position of the own station in the terminal uplink signal transmitted to the mobile relay station 2. Instead of including, the area information of the small area including the position of the own station may be included. As a result, the mobile relay station 2 can estimate the number of terminal stations 3 located in the small area.
- the mobile relay station 2 scans the communication target area with a beam so as to cover all the small areas in the communication target area, thereby equalizing the degree of communication congestion and communicating with a plurality of terminal stations 3. It can be carried out.
- transmission control process The details of the configuration and operation of each device in the process for controlling the transmission timing of the terminal uplink signal from the terminal station 3 to the mobile relay station 2 (hereinafter referred to as “transmission control process”) will be described later.
- transmission control process the configuration of each device in the process for the base station 4 to collect data such as environmental data transmitted from each terminal station 3 via the mobile relay station 2 (hereinafter referred to as “data collection process”). And the details of the operation will be described first.
- the mobile relay station 2 includes an antenna 21, a terminal communication unit 22, a data storage unit 23, a base station communication unit 24, and an antenna 25.
- the terminal communication unit 22 has a reception unit 221 and a reception waveform recording unit 222.
- the receiving unit 221 receives the terminal uplink signal by the antenna 21.
- the reception waveform recording unit 222 samples the reception waveform of the terminal uplink signal received by the reception unit 221 and generates waveform data showing the value obtained by the sampling.
- the reception waveform recording unit 222 writes the reception waveform information including the reception time of the terminal uplink signal in the antenna 21 and the generated waveform data to the data storage unit 23.
- the data storage unit 23 stores the received waveform information written by the received waveform recording unit 222.
- the base station communication unit 24 transmits the received waveform information to the base station 4 by the base station downlink signal of any wireless communication method.
- the base station communication unit 24 includes a storage unit 241, a control unit 242, a transmission data modulation unit 243, and a transmission unit 244.
- the storage unit 241 stores the transmission start timing calculated in advance based on the orbit information of the LEO satellite equipped with the mobile relay station 2 and the position of the base station 4.
- the orbit information of LEO is information that can obtain the position, speed, moving direction, etc. of the LEO satellite at an arbitrary time.
- the transmission time may be represented by, for example, the elapsed time from the transmission start timing.
- the control unit 242 controls the transmission data modulation unit 243 and the transmission unit 244 so as to transmit the received waveform information to the base station 4 at the transmission start timing stored in the storage unit 241.
- the transmission data modulation unit 243 reads the received waveform information as transmission data from the data storage unit 23, modulates the read transmission data, and generates a base station downlink signal.
- the transmission unit 244 converts the base station downlink signal from an electric signal to a wireless signal and transmits it from the antenna 25.
- the terminal station 3 includes a data storage unit 31, a transmission unit 32, and one or more antennas 33.
- the data storage unit 31 stores sensor data and the like.
- the transmission unit 32 reads sensor data as terminal transmission data from the data storage unit 31, and transmits a terminal uplink signal including the read terminal transmission data from the antenna 33 by a wireless signal.
- the transmission unit 32 transmits a signal by LPWA.
- LPWA includes LoRaWAN (registered trademark), Sigfox (registered trademark), LTE-M (LongTermEvolution for Machines), NB (NarrowBand) -IoT and the like, and any wireless communication method can be used. Further, the transmission unit 32 may transmit to another terminal station 3 by time division multiplexing or orthogonal frequency division multiplexing (OFDM) or the like.
- the transmission unit 32 determines the channel and transmission timing used by the station to transmit the terminal uplink signal by a method predetermined in the wireless communication method to be used. Further, the transmission unit 32 may form a beam of signals transmitted from a plurality of antennas 33 by a method predetermined in the wireless communication method to be used.
- the base station 4 includes an antenna 41, a receiving unit 42, a base station signal receiving processing unit 43, and a terminal signal receiving processing unit 44.
- the receiving unit 42 converts the base station downlink signal received by the antenna 41 into an electric signal.
- the base station signal reception processing unit 43 demodulates and decodes the received signal converted into an electric signal by the receiving unit 42, and obtains received waveform information.
- the base station signal reception processing unit 43 outputs the received waveform information to the terminal signal reception processing unit 44.
- the terminal signal reception processing unit 44 performs reception processing of the terminal uplink signal indicated by the received waveform information. At this time, the terminal signal reception processing unit 44 performs reception processing by the wireless communication method used for transmission by the terminal station 3 to acquire terminal transmission data.
- the terminal signal reception processing unit 44 includes a terminal signal demodulation unit 441 and a terminal signal decoding unit 442.
- the terminal signal demodulation unit 441 demodulates the waveform data and outputs the symbol obtained by the demodulation to the terminal signal decoding unit 442.
- the terminal signal demodulation unit 441 may perform a process of compensating for the Doppler shift of the terminal uplink signal received by the antenna 21 of the mobile relay station 2 on the signal indicated by the waveform data, and then perform demodulation.
- the Doppler shift received by the terminal uplink signal received by the antenna 21 is calculated in advance based on the position of the terminal station 3 and the orbit information of the LEO on which the mobile relay station 2 is mounted.
- the terminal signal decoding unit 442 decodes the symbol demodulated by the terminal signal demodulation unit 441 and obtains the terminal transmission data transmitted from the terminal station 3.
- FIG. 2 is a diagram showing an example of scanning a beam.
- the antenna 21 irradiates a small area of the communication target area 300 (service area) with a beam having a narrowed irradiation range.
- the terminal communication unit 22 uses the antenna 21 to scan the communication target area 300 with a beam.
- the arrow shown in FIG. 2 represents an example of the scanning direction.
- the terminal station 3-2 does not transmit the terminal uplink signal to the mobile relay station 2 until the terminal station 3-2 enters the irradiation range 301 of the scanned beam.
- the terminal communication unit 22 slows down the scanning speed of the beam when the transmission frequency of the terminal uplink signal is high (when the degree of congestion is high) in the irradiation range 301. That is, the terminal communication unit 22 lengthens the irradiation time of the beam with respect to the irradiation range 301 (small area) in which the terminal station 3 having a high transmission frequency of the terminal uplink signal exists.
- the terminal communication unit 22 may lengthen the irradiation time of the beam with respect to the irradiation range 301 (small area) in which a large number of terminal stations 3 exist.
- the beam is intensively irradiated to a small area where many terminal stations 3 are distributed (such as an urban area where terminal stations 3 are densely packed), so the number of terminal stations 3 that can be accommodated is adapted. It is possible to increase the number.
- FIG. 3 is a flow chart showing the scanning process of the beam.
- the area control unit 224 determines whether or not the mobile relay station 2 has arrived at a predetermined position where the beam can be applied to the communication target area 300. For example, the area control unit 224 determines whether or not the mobile relay station 2 has arrived above the communication target area 300 (step S101). When it is determined that the mobile relay station 2 has not arrived at the predetermined position (step S101 / No), the area control unit 224 re-executes step S101 after the elapse of the predetermined time.
- the antenna drive unit 228 divides the communication target area 300 based on the area information generated by the area control unit 224. A beam is irradiated to one of the small areas of the above using the antenna 21 (step S102).
- the antenna driving unit 228 scans the communication target area 300 with a beam at a scanning speed according to the degree of congestion (step S103).
- the receiving unit 221 receives the terminal uplink signal using the antenna 21.
- the communication status measurement unit 223 derives the degree of communication congestion based on the terminal uplink signal (step S104).
- the antenna drive unit 228 determines whether or not the degree of communication congestion is equal to or higher than the threshold value (step S105). When it is determined that the degree of communication congestion is equal to or higher than the threshold value (step S105 ⁇ Yes), the antenna driving unit 228 drives the antenna 21 so as to slow down the scanning speed of the beam. The antenna driving unit 228 may drive the antenna 21 so as to temporarily stop the scanning of the beam (step S106). When it is determined that the degree of communication congestion is less than the threshold value (step S105 / No), the antenna driving unit 228 drives the antenna 21 so as to increase the scanning speed of the beam (step S107).
- the antenna drive unit 228 records the area information of the small area irradiated with the beam (the small area overlapping the irradiation range 301) in the storage unit 225 as the scanned small area information (step S108). Thereby, the antenna driving unit 228 can distinguish the scanned small area and the unscanned small area in the communication target area 300.
- the antenna drive unit 228 determines whether or not all the small areas in the communication target area 300 have been scanned (step S109). When it is determined that there is an unscanned small area (step S109 / No), the antenna driving unit 228 returns the process to step S103. When it is determined that all the small areas have been scanned (step S109 ⁇ Yes), the antenna driving unit 228 ends the process shown in FIG.
- FIG. 4 is a flow chart showing the processing of the wireless communication system 1 when the terminal uplink signal is transmitted from the terminal station 3 to the mobile relay station 2.
- the terminal station 3 acquires sensor data (for example, environmental data) detected by a sensor (for example, environmental data) provided outside or inside at any time, and writes the acquired sensor data in the data storage unit 31 (step S111).
- the transmission unit 32 reads the sensor data from the data storage unit 31 as terminal transmission data.
- the transmission unit 32 wirelessly transmits the terminal uplink signal including 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 equipped with the mobile relay station 2 (step S112). ..
- the terminal station 3 repeats the process from step S111.
- the receiving unit 221 of the mobile relay station 2 receives the terminal uplink signal transmitted from the terminal station 3 (step S121). Depending on the wireless communication method of the source terminal station 3, there are cases where the terminal uplink signal is received from only one terminal station 3 on a time-division basis for the same frequency, and cases where the terminal uplink signal is received from multiple terminal stations 3 at the same frequency at the same frequency. It may receive a terminal uplink signal.
- the reception waveform recording unit 222 writes the received waveform information in which the waveform data representing the waveform of the terminal uplink signal received by the receiving unit 221 and the reception time are associated with each other in the data storage unit 23 (step S122). The mobile relay station 2 repeats the process from step S121.
- FIG. 5 is a flow chart showing processing of the wireless communication system 1 when a base station downlink signal is transmitted from the mobile relay station 2 to the base station 4.
- the control unit 242 of the base station communication unit 24 of the mobile relay station 2 detects that the transmission start timing stored in the storage unit 241 is the current time, the transmission of the received waveform information is transmitted to the transmission data modulation unit 243 and transmission.
- Instruct unit 244 (step S211).
- the transmission data modulation unit 243 reads the received waveform information stored in the data storage unit 23 as transmission data, modulates the read transmission data, and generates a base station downlink signal.
- the transmission unit 244 transmits the base station downlink signal generated by the transmission data modulation unit 243 from the antenna 25 by a wireless signal (step S212).
- the mobile relay station 2 repeats the process from step S211.
- the antenna 41 of the base station 4 receives the base station downlink signal from the mobile relay station 2 (step S221).
- the receiving unit 42 converts the base station downlink signal received by the antenna 41 into a received signal of an electric signal, and outputs the signal to the base station signal receiving processing unit 43.
- the base station signal reception processing unit 43 demodulates the received signal and decodes the demodulated received signal (step S222).
- the base station signal reception processing unit 43 outputs the reception waveform information obtained by decoding to the terminal signal reception processing unit 44.
- the terminal signal reception processing unit 44 performs reception processing of the terminal uplink signal represented by the waveform data included in the received waveform information (step S223). Specifically, the terminal signal demodulation unit 441 specifies the wireless communication method used by the terminal station 3 to transmit the terminal uplink signal based on the information unique to the wireless communication method included in the received signal represented by the waveform data. .. The terminal signal demodulation unit 441 demodulates the received signal represented by the waveform data according to the specified wireless communication method, and outputs the symbol obtained by the demodulation to the terminal signal decoding unit 442. The terminal signal decoding unit 442 decodes the symbol input from the terminal signal demodulation unit 441 by the specified wireless communication method, and obtains the terminal transmission data transmitted from the terminal station 3. The terminal signal decoding unit 442 can also use a decoding method having a large calculation load, such as SIC (Successive Interference Cancellation).
- the base station 4 repeats the process from step S221.
- the mobile relay station 2 includes a communication status measurement unit 223, an area control unit 224, a storage unit 225, a transmission unit 226, a position information acquisition unit 227, and an antenna drive unit 228. Further prepare.
- the communication status measuring unit 223 measures the communication status of the terminal uplink communication from the plurality of terminal stations 3 in the receiving unit 221.
- the communication status measurement unit 223 generates information indicating the degree of congestion of communication (hereinafter, referred to as "congestion degree information") based on the measurement result.
- the communication status measurement unit 223 measures the number of access to the terminal uplink communication from the plurality of terminal stations 3 per unit time in the reception unit 221 or the reception signal strength in the frequency band of the terminal uplink communication, and is congested. Generate frequency information.
- the congestion degree information may be the information itself indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication. It does not have to be.
- the information indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication is within a predetermined threshold range. It may be information indicating a level determined based on whether or not. That is, for example, the number of access of the terminal uplink communication per unit time from a plurality of terminal stations 3 is level 1 when it is within a certain range, level 2 when it is within a larger range, and even more range. If it is within, the level is uniquely determined, such as level 3. In this case, the information in which the range and the level of the access number and the received signal strength value are associated with each other is stored in advance in, for example, the storage unit 225.
- the location information acquisition unit 227 acquires the location information of each terminal station 3.
- the position information is included in the terminal uplink signal transmitted from each terminal station 3 and received by the receiving unit 221.
- the area control unit 224 controls the timing of transmitting the terminal downlink signal including the transmission permission signal to the terminal station 3.
- the transmission permission signal is a control signal indicating that the terminal station 3 is permitted to transmit data such as environmental data to its own mobile relay station 2.
- the area control unit 224 acquires the congestion degree information generated by the communication status measurement unit 223. Further, the area control unit 224 acquires the position information indicating the position of each terminal station 3 acquired by the position information acquisition unit 227.
- the area control unit 224 changes the scanning speed of the beam by using the antenna drive unit 228 based on the acquired congestion degree information.
- the area control unit 224 may change the scanning speed of the beam by using the antenna drive unit 228 based on the acquired congestion degree information and the position information. As described above, for example, the area control unit 224 changes the scanning speed of the beam so that the degree of congestion of communication with the terminal station 3 included in the divided small areas is made uniform in the plurality of small areas. ..
- the area control unit 224 stores the area information of each small area in the storage unit 225.
- the area control unit 224 refers to the area information recorded in the storage unit 225, and generates a transmission permission signal to be transmitted toward a small area of the irradiation range of the beam (a small area associated with the area information).
- the area control unit 224 controls the timing at which the terminal downlink signal including the transmission permission signal is transmitted to the terminal station 3.
- the area control unit 224 controls the change speed of the direction of the antenna 21 (the scanning speed of the beam) by using the antenna drive unit 228.
- the orientation of the antenna 21 is changed by the antenna drive unit 228 according to the control by the area control unit 224.
- the antenna drive unit 228 changes the direction (beam irradiation direction) of the antenna 21 by using, for example, a mechanical drive mechanism.
- the transmission unit 226 acquires the transmission permission signal generated by the area control unit 224, and transmits the terminal downlink signal including the acquired transmission permission signal from the antenna 21 by a wireless signal.
- the transmission unit 226 transmits a signal by LPWA.
- the transmission unit 226 determines the channel used by the station for transmitting the terminal downlink signal by a method predetermined in the wireless communication method to be used.
- the timing at which the transmission unit 226 transmits the terminal downlink signal is controlled by the area control unit 224.
- the storage unit 225 stores the transmission start timing for each communication target area calculated in advance based on the orbit information of the LEO satellite equipped with the mobile relay station 2 and the position of the communication target area.
- the orbit information of LEO is information that can obtain the position, speed, moving direction, etc. of the LEO satellite at an arbitrary time.
- the transmission time may be represented by, for example, the elapsed time from the transmission start timing.
- the area control unit 224 controls the transmission unit 226 so as to transmit the terminal downlink signal including the transmission permission signal to the ground at the transmission start timing for each communication target area stored in the storage unit 225.
- the mobile relay station 2 is provided, for example, on a LEO satellite that orbits the earth in a predetermined cycle.
- the area control unit 224 scans the beam, for example, based on the degree of communication congestion when receiving terminal uplink signals from a plurality of terminal stations 3 in the communication target area in the past (for example, at a time before one round). Determine the initial value of speed.
- the area control unit 224 determines the scanning speed of the beam based on, for example, the degree of communication congestion when receiving terminal uplink signals from a plurality of terminal stations 3 in the communication target area in the same time zone in the past.
- the initial value may be set.
- the terminal station 3 further includes a receiving unit 34, a transmission control unit 35, and a position information generation unit 36.
- the receiving unit 34 When the receiving unit 34 is located in the irradiation range of the beam, the receiving unit 34 receives the terminal downlink signal by the antenna 33.
- the transmission control unit 35 acquires a transmission permission signal from the terminal downlink signal received by the reception unit 34.
- the position information generation unit 36 is provided with a positioning device such as a GPS receiver, and specifies the position of its own station.
- the position information generation unit 36 generates position information indicating the position of the specified own station.
- the transmission control unit 35 acquires the position information indicating the position of the own station generated by the position information generation unit 36. The transmission control unit 35 determines whether or not the transmission permission signal has been acquired. When the transmission permission signal is not acquired, the transmission control unit 35 stands by without starting the transmission of the terminal uplink signal to the mobile relay station 2.
- the transmission control unit 35 causes the transmission unit 32 to start transmitting the terminal uplink signal to the mobile relay station 2. At this time, the transmission control unit 35 causes the transmission unit 32 to transmit a terminal uplink signal including the position information generated by the position information generation unit 36 in addition to data such as environmental data.
- the transmission unit 32 transmits a terminal uplink signal.
- the transmission unit 32 reads sensor data such as environmental data from the data storage unit 31 as terminal transmission data.
- the transmission unit 32 transmits a terminal uplink signal including the read terminal transmission data and the position information indicating the position of the own station generated by the position information generation unit 36 from the antenna 33 by a wireless signal.
- the transmission unit 32 transmits a signal by LPWA.
- the receiving unit 221 of the mobile relay station 2 receives the terminal uplink signal by the antenna 21.
- the reception waveform recording unit 222 samples the reception waveform of the terminal transmission data included in the terminal uplink signal received by the reception unit 221 and generates waveform data showing the value obtained by the sampling.
- the reception waveform recording unit 222 writes the reception waveform information including the reception time of the terminal uplink signal in the antenna 21 and the selected waveform data to the data storage unit 23.
- the data storage unit 23 stores the received waveform information written by the received waveform recording unit 222.
- FIG. 6 is a flow chart showing transmission control processing by the wireless communication system 1.
- the area control unit 224 of the mobile relay station 2 executes a beam scanning process using the antenna drive unit 228 (step S311).
- the area control unit 224 of the mobile relay station 2 generates a transmission permission signal (step S312).
- the transmission unit 226 acquires the transmission permission signal generated by the area control unit 224, and transmits the terminal downlink signal including the acquired transmission permission signal from the antenna 21 by a wireless signal (step S313).
- the mobile relay station 2 repeats the process from step S311.
- the receiving unit 34 of the terminal station 3 receives the terminal downlink signal by the antenna 33 (step S321).
- the transmission control unit 35 of the terminal station 3 acquires a transmission permission signal from the terminal downlink signal received by the reception unit 34 (step S322).
- the position information generation unit 36 of the terminal station 3 specifies the position of its own station (step S323).
- the position information generation unit 36 generates position information indicating the position of the specified own station.
- the transmission control unit 35 acquires the position information indicating the position of the own station generated by the position information generation unit 36 (step S324).
- the transmission control unit 35 causes the transmission unit 32 to start transmitting the terminal uplink signal. At this time, the transmission control unit 35 causes the transmission unit 32 to transmit a terminal uplink signal including data such as environmental data and position information indicating the position of the own station generated by the position information generation unit 36. The transmission unit 32 transmits a terminal uplink signal (step S325). The terminal station 3 repeats the process from step S321.
- the receiving unit 221 of the mobile relay station 2 receives the terminal uplink signal by the antenna 21 (step S331).
- the reception waveform recording unit 222 of the mobile relay station 2 samples the reception waveform of the terminal uplink signal received by the reception unit 221 and generates waveform data showing the value obtained by the sampling.
- the reception waveform recording unit 222 writes the reception waveform information including the reception time of the terminal uplink signal in the antenna 21 and the selected waveform data to the data storage unit 23.
- the data storage unit 23 stores the reception waveform information written by the reception waveform recording unit 222 (step S332).
- the communication status measurement unit 223 of the mobile relay station 2 measures the communication status of the terminal uplink communication from the plurality of terminal stations 3 in the reception unit 221 (step S333), and generates congestion degree information.
- the position information acquisition unit 227 of the mobile relay station 2 acquires the position information of each terminal station 3 (step S334). The position information is included in the terminal uplink signal transmitted from each terminal station 3 and received by the receiving unit 221.
- the area control unit 224 adjusts the scanning speed of the beam based on the acquired congestion degree information and position information (step S335). As described above, for example, the mobile relay station 2 adjusts the scanning speed so that the degree of congestion of communication with the terminal station 3 included in the divided small areas is made uniform among the plurality of small areas.
- the area control unit 224 stores the area information of the small area scanned by the beam in the storage unit 225 (step S336). The mobile relay station 2 repeats the process from step S331.
- the mobile relay station 2 receives the terminal uplink signals transmitted from each of the plurality of terminal stations 3 and measures the communication status.
- the mobile relay station 2 generates congestion degree information based on the communication status.
- the mobile relay station 2 acquires the position information included in the terminal uplink signals transmitted from the plurality of terminal stations 3, respectively.
- the position information is information indicating the position of each terminal station 3.
- the mobile relay station 2 adjusts the scanning speed of the beam in the communication target area based on the congestion degree information and the position information.
- the mobile relay station 2 permits the transmission of the terminal uplink signal for each terminal station 3 existing in the small area that divides the communication target area during the subsequent laps.
- the mobile relay station 2 transmits a terminal downlink signal including a transmission permission signal toward the ground.
- the terminal station 3 acquires the transmission permission signal indicated by the received terminal downlink signal, and acquires the transmission permission signal.
- the terminal station 3 specifies the position of its own station by, for example, a positioning device or the like.
- the terminal station 3 starts transmitting the terminal uplink signal to the mobile relay station 2.
- the terminal station 3 may transmit a terminal uplink signal including data such as environmental data and position information indicating the position of the own station to the mobile relay station 2.
- the wireless communication system 1 has one or more terminal stations 3 (third) located in one or more small areas among a plurality of small areas that divide the communication target area 300. 1 communication device), a mobile relay station 2 (relay device), and a base station 4 (second communication device).
- the antenna driving unit 228 drives one or more antennas 21 so as to scan a plurality of small areas with the beam while irradiating the communication target area with one or more beams having an irradiation range 301 narrower than the communication target area 300.
- the receiving unit 221 acquires a terminal uplink signal (first radio signal) transmitted from the terminal station 3 located in the irradiation range 301 from one or more antennas 21.
- the transmission unit 244 transmits a base station downlink signal (second radio signal) corresponding to the terminal uplink signal to the base station 4 (second communication device).
- the antenna drive unit 228 drives the direction of the antenna 21 by using, for example, a mechanical drive mechanism so as to scan the communication target area 300 with a beam at a scanning speed according to the degree of congestion.
- the antenna driving unit 228 may drive the antenna 21 so as to slow down the scanning speed when the degree of congestion is equal to or higher than the threshold value.
- the antenna driving unit 228 may drive the antenna 21 so as to increase the scanning speed when the degree of congestion is less than the threshold value.
- the wireless communication system 1 can control the transmission timing of the terminal uplink signal from the terminal station 3 to the mobile relay station 2 for each beam irradiation range.
- the wireless communication system 1 adjusts the scanning speed of the beam so as to make the degree of congestion of communication uniform, for example.
- the wireless communication system 1 can be adjusted so as to make the communication congestion degree uniform even when the communication congestion degree fluctuates, so that the communication reliability deterioration can be suppressed and the communication reliability can be further suppressed.
- Sensor data transmitted from many terminal stations 3 can be transmitted to the base station 4 via the mobile relay station 2.
- the wireless communication system 1 is a system suitable for IoT communication with few communication opportunities because a wide coverage can be developed with a small number of beams.
- the area information indicating a small area may be information indicating a range indicated by latitude and longitude, for example.
- the area information indicating the small area may be, for example, index information for identifying the small area previously divided into predetermined sections according to latitude, longitude, or the like.
- the information indicating the range such as latitude and longitude corresponding to each index information needs to be shared in advance between the mobile relay station 2 and the terminal station 3.
- the transmission unit 32 when the transmission control unit 35 of the terminal station 3 acquires the transmission permission signal, the transmission unit 32 causes the transmission unit 32 to start transmitting the terminal uplink signal. At this time, the transmission control unit 35 does not immediately start the transmission of the terminal uplink signal, but starts the transmission of the terminal uplink signal at the timing when a random time elapses after the transmission permission signal is acquired. You may. This makes it possible to prevent a plurality of terminal stations 3 located in the irradiation range of the beam (within the same small area) from simultaneously starting transmission of the terminal uplink signal to the mobile relay station 2. Therefore, the degree of communication congestion in the mobile relay station 2 is reduced.
- the mobile relay station transmits a base station downlink signal by a plurality of antennas.
- MIMO Multiple Input Multiple Output
- FIG. 7 is a configuration diagram of a wireless communication system 1a according to a modification 1 of the first embodiment.
- the wireless communication system 1a has a mobile relay station 2a, a terminal station 3, and a base station 4a.
- the mobile relay station 2a includes an antenna 21, a terminal communication unit 22, a data storage unit 23, a base station communication unit 26, and a plurality of antennas 25.
- the base station communication unit 26 transmits received waveform information to the base station 4a by MIMO.
- the base station communication unit 26 includes a storage unit 261, a control unit 262, a transmission data modulation unit 263, and a MIMO transmission unit 264.
- the storage unit 261 stores the transmission start timing calculated in advance based on the orbit information of the LEO satellite equipped with the mobile relay station 2a and the position of the base station 4a. Further, the storage unit 261 stores in advance the weight (weighting coefficient) for each transmission time of the base station downlink signal transmitted from each antenna 25. The weight for each transmission time is calculated based on the orbit information of the LEO satellite and the position of each antenna station 410 included in the base station 4a. A constant weight may be used regardless of the transmission time.
- the control unit 262 controls the transmission data modulation unit 263 and the MIMO transmission unit 264 so as to transmit the received waveform information to the base station 4a at the transmission start timing stored in the storage unit 261. Further, the control unit 262 instructs the MIMO transmission unit 264 to wait for each transmission time read from the storage unit 261. The direction of the beam transmitted from the antenna 25 is determined based on the weight.
- the transmission data modulation unit 263 reads the received waveform information as transmission data from the data storage unit 23, converts the read transmission data into a parallel signal, and then modulates the parallel signal.
- the MIMO transmission unit 264 weights the modulated parallel signal by the weight instructed by the control unit 262, and generates a base station downlink signal transmitted from each antenna 25.
- the MIMO transmission unit 264 transmits the generated base station downlink signal from the antenna 25 by MIMO.
- the base station 4a includes a plurality of antenna stations 410, a MIMO receiving unit 420, a base station signal receiving processing unit 430, and a terminal signal receiving processing unit 44.
- the antenna station 410 is arranged at a position away from the other antenna stations 410 so that the arrival angle difference of the radio signals transmitted from the plurality of antennas 25 of the mobile relay station 2a becomes large.
- Each antenna station 410 converts the base station downlink signal received from the mobile relay station 2a into an electric signal, and outputs the electric signal to the MIMO receiving unit 420.
- the MIMO receiver 420 aggregates the base station downlink signals received from the plurality of antenna stations 410.
- the MIMO receiving unit 420 stores the weight for each reception time for the base station downlink signal received by each antenna station 410 based on the orbit information of the LEO satellite and the position of each antenna station 410.
- the MIMO receiver 420 multiplies the base station downlink signal input from each antenna station 410 by the weight corresponding to the reception time of the base station downlink signal, and synthesizes the received signal multiplied by the weight. ..
- the same weight may be used regardless of the reception time.
- the base station signal reception processing unit 430 demodulates and decodes the synthesized received signal to obtain received waveform information.
- the base station signal reception processing unit 430 outputs the received waveform information to the terminal signal reception processing unit 44.
- the processing of the wireless communication system 1a when transmitting the terminal uplink signal from the terminal station 3 is the same as the processing of the wireless communication system 1 of the first embodiment shown in FIG.
- FIG. 8 is a flow chart showing the processing of the wireless communication system 1a when the base station downlink signal is transmitted from the mobile relay station 2a.
- the control unit 262 of the base station communication unit 26 of the mobile relay station 2a detects that the transmission start timing stored in the storage unit 261 is the current time, the transmission of the received waveform information is transmitted to the transmission data modulation unit 263 and the MIMO. Instruct the transmission unit 264 (step S411).
- the transmission data modulation unit 263 reads the received waveform information stored in the data storage unit 23 as transmission data, converts the read transmission data in parallel, and then modulates the transmission data.
- the MIMO transmission unit 264 weights the transmission data modulated by the transmission data modulation unit 263 by the weight instructed by the control unit 262 to generate a base station downlink signal which is a transmission signal transmitted from each antenna 25.
- the MIMO transmission unit 264 transmits each generated base station downlink signal from the antenna 25 by MIMO (step S412).
- the mobile relay station 2a repeats the process from step S411.
- Each antenna station 410 of the base station 4a receives a base station downlink signal from the mobile relay station 2a (step S421).
- Each antenna station 410 outputs a received signal obtained by converting the received base station downlink signal into an electric signal to the MIMO receiving unit 420.
- the MIMO receiving unit 420 synchronizes the timing of the received signal received from each antenna station 410.
- the MIMO receiving unit 420 multiplies and adds the received signal received by each antenna station 410 by a weight.
- the base station signal reception processing unit 430 demodulates the added received signal and decodes the demodulated received signal (step S422).
- the base station signal reception processing unit 430 outputs the reception waveform information obtained by decoding to the terminal signal reception processing unit 44.
- the terminal signal reception processing unit 44 performs reception processing of the terminal uplink signal represented by the waveform data included in the received waveform information by the same processing as in step S223 in the processing flow of the first embodiment shown in FIG. 5 (step). S423). That is, the terminal signal demodulation unit 441 specifies the wireless communication method used by the terminal station 3 to transmit the terminal uplink signal based on the information unique to the wireless communication method included in the received signal represented by the waveform data. The terminal signal demodulation unit 441 demodulates the received signal represented by the waveform data according to the specified wireless communication method, and outputs the symbol obtained by the demodulation to the terminal signal decoding unit 442.
- the terminal signal decoding unit 442 decodes the symbol input from the terminal signal demodulation unit 441 by the specified wireless communication method, and obtains the terminal transmission data transmitted from the terminal station 3.
- the terminal signal decoding unit 442 can also use a decoding method having a large calculation load, such as SIC.
- the base station 4a repeats the process from step S421.
- the mobile relay station 2a collectively collects the stored data received from the plurality of terminal stations 3 at a timing capable of communicating with the base station 4a in a short time. Can be sent with good quality.
- the mobile relay station receives the terminal uplink signal from the plurality of antennas and transmits the terminal downlink signal from the plurality of antennas.
- the difference from the first modification of the first embodiment will be mainly described.
- FIG. 9 is a configuration diagram of a wireless communication system 1b according to a modification 2 of the first embodiment.
- the wireless communication system 1b has a mobile relay station 2b, a terminal station 3, and a base station 4b.
- the mobile relay station 2b includes N antennas 21 (N is an integer of 2 or more), a terminal communication unit 22b, a data storage unit 23, a base station communication unit 26, and a plurality of antennas 25.
- the N antennas 21 are described as antennas 21-1 to 21-N, respectively.
- the terminal communication unit 22b has N reception units 221b and N reception waveform recording units 222b.
- the N receiving units 221b are referred to as receiving units 221b-1 to 221b-N, and the N receiving waveform recording units 222b are referred to as receiving waveform recording units 222b-1 to 222b-N.
- the receiving unit 221b-n (n is an integer of 1 or more and N or less) receives the terminal uplink signal by the antenna 21-n.
- the reception waveform recording unit 222bn samples the reception waveform of the terminal uplink signal received by the reception unit 221bn, and generates waveform data showing the value obtained by sampling.
- the received waveform recording unit 222bn writes the received waveform information including the antenna identifier of the antenna 21-n, the reception time of the terminal uplink signal in the antenna 21-n, and the generated waveform data to the data storage unit 23. ..
- the antenna identifier is information that identifies the antenna 21-n.
- the data storage unit 23 stores received waveform information including waveform data of the terminal uplink signal received by each of the antennas 21-1 to 21-N.
- the base station 4b includes a plurality of antenna stations 410, a MIMO receiving unit 420, a base station signal receiving processing unit 430, and a terminal signal receiving processing unit 450.
- the terminal signal reception processing unit 450 performs reception processing of the terminal uplink signal indicated by the received waveform information. At this time, the terminal signal reception processing unit 450 performs reception processing by the wireless communication method used for transmission by the terminal station 3 to acquire terminal transmission data.
- the terminal signal reception processing unit 450 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 described as terminal signal demodulation units 452-1 to 452-N, respectively.
- the distribution unit 451 reads out waveform data at the same reception time from the received waveform information, and outputs the read waveform data to the terminal signal demodulation units 452-1 to 452-N according to the antenna identifier associated with the waveform data. do. 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.
- Each of the terminal signal demodulation units 452-1 to 452-N demodulates the signal represented by the waveform data, and outputs the symbol obtained by the demodulation to the synthesis unit 453.
- the terminal signal demodulation unit 452-n performs a process of compensating for the Doppler shift of the terminal uplink signal received by the antenna 21-n of the mobile relay station 2 with respect to the signal represented by the waveform data, and then demodulates the signal. May be good.
- the Doppler shift received 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 orbit information of the LEO on which the mobile relay station 2b is mounted.
- the synthesis unit 453 adds and synthesizes the symbols input from each of the terminal signal demodulation units 452-1 to 452-N, and outputs them to the terminal signal decoding unit 454.
- the terminal signal decoding unit 454 decodes the additively synthesized symbol and obtains the terminal transmission data transmitted from the terminal station 3.
- the mobile relay station 2b further includes a communication status measurement unit 223b, an area control unit 224b, a storage unit 225, a transmission unit 226b, and a position information acquisition unit 227b.
- the communication status measuring unit 223b measures the communication status of the terminal uplink communication from the plurality of terminal stations 3 in the receiving units 221b-1 to 221b-N.
- the communication status measurement unit 223b generates information (congestion degree information) indicating the degree of congestion of communication based on the measurement result.
- the communication status measuring unit 223b may use the receiving units 221b-1 to 221b-N as the number of access to the terminal uplink communication per unit time from the plurality of terminal stations 3, or the reception signal in the frequency band of the terminal uplink communication. Measure the intensity and generate congestion information.
- the congestion degree information may be the information itself indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication. It does not have to be.
- the information indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication is within a predetermined threshold range. It may be information indicating a level determined based on whether or not. In this case, the information in which the range and the level of the access number and the received signal strength value are associated with each other is stored in advance in, for example, the storage unit 225.
- the position information acquisition unit 227b acquires the position information of each terminal station 3.
- the position information is included in the terminal uplink signal transmitted from each terminal station 3 and received by the receiving units 221b-1 to 221b-N.
- the area control unit 224b controls the timing of transmitting the terminal downlink signal including the transmission permission signal to the terminal station 3.
- the area control unit 224b acquires the congestion degree information generated by the communication status measurement unit 223b. Further, the area control unit 224b acquires the position information indicating the position of each terminal station 3 acquired by the position information acquisition unit 227b.
- the area control unit 224b changes the scanning speed of the beam based on the acquired congestion degree information.
- the area control unit 224b may change the scanning speed of the beam based on the acquired congestion degree information and position information.
- the mobile relay station 2b changes the scanning speed of the beam so that the degree of congestion of communication with the terminal station 3 included in the divided small areas is made uniform in the plurality of small areas.
- the area control unit 224b stores the area information of each small area in the storage unit 225.
- the area control unit 224b refers to the area information recorded in the storage unit 225 and generates a transmission permission signal to be transmitted toward a small area of the irradiation range of the beam (a small area associated with the area information).
- the area control unit 224b controls the timing of transmitting the terminal downlink signal including the transmission permission signal to the terminal station 3.
- the area control unit 224b controls the change speed of the beam irradiation direction (beam scanning speed).
- the direction of the beam irradiation may be changed by the antenna driving unit 228 without changing the direction of the antenna 21.
- the antenna drive unit 228 changes the irradiation direction of the beam by using, for example, a phased array, according to the control by the area control unit 224.
- the beam is generated for each group of 21 groups of antennas.
- the transmission unit 226b acquires the transmission permission signal generated by the area control unit 224b, and transmits the terminal downlink signal including the acquired transmission permission signal from the plurality of antennas 21 by wireless signal.
- the transmission unit 226b transmits a signal by LPWA.
- the transmission unit 226b determines the channel used by the station for transmitting the terminal downlink signal by a predetermined method in the wireless communication method to be used.
- the timing at which the transmission unit 226b transmits the terminal downlink signal is controlled by the area control unit 224b.
- the storage unit 225 stores the transmission start timing for each communication target area calculated in advance based on the orbit information of the LEO satellite equipped with the mobile relay station 2b and the position of the communication target area.
- the area control unit 224b controls the transmission unit 226b so as to transmit the terminal downlink signal including the transmission permission signal to the ground at the transmission start timing for each communication target area stored in the storage unit 225.
- the area control unit 224b scans the beam, for example, based on the degree of communication congestion when receiving terminal uplink signals from a plurality of terminal stations 3 in the communication target area before (for example, at a time before one round). Determine the initial value of speed.
- the area control unit 224b determines the scanning speed of the beam based on, for example, the degree of communication congestion when receiving terminal uplink signals from a plurality of terminal stations 3 in the communication target area in the same time zone in the past.
- the initial value may be set.
- the terminal station 3 further includes a receiving unit 34, a transmission control unit 35, and a position information generation unit 36.
- the receiving unit 34 receives the terminal downlink signal by the antenna 33.
- the transmission control unit 35 acquires a transmission permission signal from the terminal downlink signal received by the reception unit 34.
- the position information generation unit 36 is provided with a positioning device such as a GPS receiver, and specifies the position of its own station.
- the position information generation unit 36 generates position information indicating the position of the specified own station.
- the transmission control unit 35 acquires the position information indicating the position of the own station generated by the position information generation unit 36. The transmission control unit 35 determines whether or not the transmission permission signal has been acquired. When the transmission permission signal is not acquired, the transmission control unit 35 waits for the terminal station 3 without starting the transmission of the terminal uplink signal to the mobile relay station 2b.
- the transmission control unit 35 causes the transmission unit 32 to start transmitting the terminal uplink signal. At this time, the transmission control unit 35 causes the transmission unit 32 to transmit a terminal uplink signal including data such as environmental data and position information indicating the position of the own station generated by the position information generation unit 36.
- the transmission unit 32 transmits a terminal uplink signal.
- the transmission unit 32 reads sensor data such as environmental data from the data storage unit 31 as terminal transmission data.
- the transmission unit 32 transmits a terminal uplink signal including the read terminal transmission data and the position information indicating the position of the own station generated by the position information generation unit 36 from the antenna 33 by a wireless signal.
- the transmission unit 32 transmits a signal by LPWA.
- the receiving units 221b-1 to 221b-N of the mobile relay station 2b receive the terminal uplink signal by the antennas 21-1 to 21-N.
- the reception waveform recording units 222b-1 to 222b-N sample the reception waveform of the terminal uplink signal received by the reception units 221b-1 to 221b-N, and generate waveform data showing the value obtained by the sampling.
- the received waveform recording units 222b-1 to 222b-N write the received waveform information including the reception time of the terminal uplink signal in the antennas 21-1 to 21-N and the selected waveform data to the data storage unit 23. ..
- the data storage unit 23 stores the reception waveform information written by the reception waveform recording units 222b-1 to 222b-N.
- FIG. 10 is a diagram showing an example of scanning a beam.
- the plurality of antennas 21 constitute a multi-antenna element (massive antenna array).
- the number of antennas 21 is larger than the number of beams radiated to the communication target area 300.
- the plurality of antennas 21 are previously divided (grouped) into clusters.
- a beam is formed by beamforming for each cluster.
- the antenna driving unit 228 moves the position of the irradiation range 301 of each beam by controlling the irradiation direction of each beam by using multi-beam forming by the multi-antenna element.
- the antenna drive unit 228 controls a plurality of antennas 21 by using multi-beam forming by a multi-antenna element so as to scan the communication target area 300 with each beam.
- the arrow shown in FIG. 10 represents an example of the scanning direction.
- the antenna drive unit 228 changes the scanning speed of the beam scanning the communication target area 300 based on the degree of communication congestion. For example, the mobile relay station 2 changes the scanning speed so that the degree of congestion of communication with the terminal station 3 included in each small area is made uniform in a plurality of small areas.
- the antenna driving unit 228 slows down the scanning speed of the beam. That is, the area control unit 224 antenna drives the degree of congestion (parameter) of communication so as to lengthen the irradiation time of the beam for the irradiation range 301 (small area) where the terminal station 3 that transmits many terminal uplink signals exists. Set to unit 228. This makes it possible to improve the gain of the signal transmitted from the terminal station 3 that transmits many terminal uplink signals.
- the antenna driving unit 228 may temporarily set the scanning speed of the beam to 0. That is, when the degree of communication congestion is equal to or higher than the threshold value, the antenna driving unit 228 may temporarily stop scanning the beam.
- the antenna driving unit 228 increases the scanning speed of the beam. As a result, the scanning of the communication target area 300 (all small areas) can be completed in a short time.
- the antenna drive unit 228 may change the scanning speed of the beam scanning the communication target area 300 based on the degree of communication congestion and the position information indicating the positions of the plurality of terminal stations 3. For example, the mobile relay station 2 scans so that the degree of congestion of communication with the terminal station 3 included in each small area and the respective positions of the plurality of terminal stations 3 are uniform in the plurality of small areas. Change the speed.
- the antenna driving unit 228 slows down the scanning speed of the beam. That is, the area control unit 224 sets the communication congestion degree (parameter) in the antenna drive unit 228 so as to lengthen the irradiation time of the beam for the irradiation range 301 (small area) in which a large number of terminal stations 3 exist. This makes it possible to improve the gain of the terminal uplink signal transmitted from many terminal stations 3.
- the antenna driving unit 228 may temporarily set the scanning speed of the beam to zero. That is, when the degree of communication congestion and the number of position information are equal to or greater than the threshold value, the antenna driving unit 228 may temporarily stop scanning the beam.
- the antenna driving unit 228 increases the scanning speed of the beam. As a result, the scanning of the communication target area 300 (all small areas) can be completed in a short time.
- the antenna driving unit 228 drives the antenna 21 so as to scan a plurality of small areas in the communication target area 300 with each beam in a state where the beam irradiation ranges 301 are separated from each other. This makes it possible to prevent the terminal uplink signals from interfering with each other.
- FIG. 11 is a flow chart showing the scanning process of the beam.
- the area control unit 224 determines whether or not the mobile relay station 2 has arrived at a predetermined position where the beam can be applied to the communication target area 300 (step S401). When it is determined that the mobile relay station 2 has not arrived at the predetermined position (step S401 / No), the area control unit 224 re-executes step S401 after the elapse of the predetermined time.
- the antenna drive unit 228 is one or more of a plurality of small areas that divide the communication target area 300 based on the area information.
- the small area of the above is irradiated with a beam using the antenna 21 (step S402).
- the antenna driving unit 228 drives the antenna 21 so that each beam scans the communication target area 300 at a scanning speed according to the degree of congestion.
- the antenna driving unit 228 drives the antenna 21 so as to scan the communication target area 300 with each beam in a state where the irradiation ranges 301 of the beams are separated from each other (step S403).
- the receiving unit 221 receives the terminal uplink signal using the antenna 21.
- the area control unit 224 derives the degree of congestion of communication based on the terminal uplink signal (step S404).
- the antenna drive unit 228 determines whether or not the degree of communication congestion is equal to or higher than the threshold value (step S405). When it is determined that the degree of communication congestion is equal to or higher than the threshold value (step S405 ⁇ Yes), the antenna driving unit 228 drives the antenna 21 so as to slow down the scanning speed of each beam. The antenna drive unit 228 may temporarily stop scanning each beam (step S406). When it is determined that the degree of communication congestion is less than the threshold value (step S405 ⁇ No), the antenna driving unit 228 drives the antenna 21 so as to increase the scanning speed of each beam (step S407).
- the antenna drive unit 228 uses the area information of the small area irradiated with the beam (the small area that overlaps with at least a part of the irradiation range 301) as the information of the scanned small area, and stores the storage unit 225 for each small area. (Step S408). Thereby, the antenna driving unit 228 can distinguish the scanned small area and the unscanned small area in the communication target area 300.
- the antenna drive unit 228 determines whether or not all the small areas in the communication target area 300 have been scanned (step S409). When it is determined that there is an unscanned small area (step S409 / No), the antenna drive unit 228 returns the process to step S403. When it is determined that all the small areas have been scanned (step S409 ⁇ Yes), the antenna driving unit 228 ends the process shown in FIG.
- FIG. 12 is a flow chart showing the processing of the wireless communication system 1b when the terminal uplink signal is transmitted from the terminal station 3 to the mobile relay station 2b.
- the terminal station 3 performs the same processing as the processing of steps S111 to S112 in the processing flow of the first embodiment shown in FIG.
- the terminal station 3 may perform transmission with another terminal station 3 by time division multiplexing, OFDM, MIMO, or the like.
- the receiving units 221b-1 to 221b-N of the mobile relay station 2b receive the terminal uplink signal transmitted from the terminal station 3 (step S521). Depending on the wireless communication method of the source terminal station 3, there are cases where the terminal uplink signal is received from only one terminal station 3 on a time-division basis for the same frequency, and cases where the terminal uplink signal is received from multiple terminal stations 3 at the same frequency at the same frequency. It may receive a terminal uplink signal.
- the received waveform recording unit 222bn provides waveform data representing the waveform of the terminal uplink signal received by the receiving unit 221bn, and received waveform information in which the reception time and the antenna identifier of the antenna 21-n are associated with each other. Write to the data storage unit 23 (step S522). The mobile relay station 2b repeats the process from step S521.
- the processing of the wireless communication system 1b in the case of transmitting the base station downlink signal from the mobile relay station 2b to the base station 4 is the processing flow of the modification 1 of the first embodiment shown in FIG. 8 except for the following processing. Is similar to. That is, in step S423, the terminal signal reception processing unit 450 performs reception processing of the terminal uplink signal indicated by the received waveform information. Specifically, the distribution unit 451 reads out waveform data having the same reception time from the received waveform information, and reads the read waveform data according to the antenna identifier associated with the waveform data, from the terminal signal demodulation unit 452-1 to Output to 452-N.
- the terminal signal demodulation units 452-1 to 452-N each use the wireless communication method used by the terminal station 3 to transmit the terminal uplink signal based on the information unique to the wireless communication method included in the received signal represented by the waveform data. Identify.
- the terminal signal demodulation units 452-1 to 452-N demodulate the received signal represented by the waveform data according to the specified wireless communication method, and output the symbol obtained by the demodulation to the synthesis unit 453.
- the synthesis unit 453 adds and synthesizes the symbols input from each of the terminal signal demodulation units 452-1 to 452-N.
- the signal transmitted by the terminal station 3 is emphasized because it has a correlation, but the influence of randomly added noise is reduced. Therefore, the diversity effect can be obtained for the terminal uplink signal received by the mobile relay station 2b from only one terminal station 3 at the same time. Further, the terminal uplink signal received by the mobile relay station 2b from a plurality of terminal stations 3 at the same time corresponds to performing MIMO communication.
- the synthesis unit 453 outputs the additively synthesized symbol to the terminal signal decoding unit 454.
- the terminal signal decoding unit 454 decodes the symbol added and synthesized by the synthesis unit 453 by the specified wireless communication method, and obtains the terminal transmission data transmitted from the terminal station 3.
- the terminal signal decoding unit 454 can also use a decoding method having a large calculation load, such as SIC.
- FIG. 13 is a flow chart showing transmission control processing by the wireless communication system 1b.
- the area control unit 224b of the mobile relay station 2 executes the beam scanning process by using the antenna drive unit 228 (step S611).
- the area control unit 224b of the mobile relay station 2b generates a transmission permission signal (step S612).
- the transmission unit 226b acquires the transmission permission signal generated by the area control unit 224b, and transmits the terminal downlink signal including the acquired transmission permission signal from the antennas 21-1 to 21-N by wireless signal. (Step S613).
- the mobile relay station 2b repeats the process from step S611.
- the receiving unit 34 of the terminal station 3 receives the terminal downlink signal by the antenna 33 (step S621).
- the transmission control unit 35 of the terminal station 3 acquires a transmission permission signal from the terminal downlink signal received by the reception unit 34 (step S622).
- the position information generation unit 36 of the terminal station 3 specifies the position of its own station (step S623).
- the position information generation unit 36 generates position information indicating the position of the specified own station.
- the transmission control unit 35 acquires the position information indicating the position of the own station generated by the position information generation unit 36 (step S624).
- the transmission control unit 35 causes the transmission unit 32 to start transmitting the terminal uplink signal. At this time, the transmission control unit 35 causes the transmission unit 32 to transmit a terminal uplink signal including data such as environmental data and position information indicating the position of the own station generated by the position information generation unit 36. The transmission unit 32 transmits a terminal uplink signal (step S625). The terminal station 3 repeats the process from step S621.
- the receiving units 221b-1 to 221b-N of the mobile relay station 2b receive the terminal uplink signal by the antennas 21-1 to 21-N (step S631).
- the reception waveform recording units 222b-1 to 222b-N of the mobile relay station 2b sample the reception waveform of the terminal uplink signal received by the reception units 221b-1 to 221b-N, and the waveform showing the value obtained by the sampling. Generate data.
- the received waveform recording units 222b-1 to 222b-N write the received waveform information including the reception time of the terminal uplink signal in the antennas 21-1 to 21-N and the selected waveform data to the data storage unit 23. ..
- the data storage unit 23 stores the reception waveform information written by the reception waveform recording units 222b-1 to 222b-N (step S632).
- the communication status measuring unit 223b of the mobile relay station 2b measures the communication status of the terminal uplink communication from the plurality of terminal stations 3 in the receiving units 221b-1 to 221b-N (step S633), and determines the degree of communication congestion. Generate the information (congestion degree information) to be shown.
- the position information acquisition unit 227b of the mobile relay station 2b acquires the position information of each terminal station 3 (step S334). The position information is included in the terminal uplink signal transmitted from each terminal station 3 and received by the receiving units 221b-1 to 221b-N.
- the area control unit 224b adjusts the scanning speed of the beam based on the acquired congestion degree information and position information (step S635). As described above, for example, the mobile relay station 2b adjusts the scanning speed so that the degree of congestion of communication with the terminal station 3 included in the divided small areas is made uniform among the plurality of small areas.
- the area control unit 224b stores the area information of the small area scanned by the beam in the storage unit 225 (step S636). The mobile relay station 2b repeats the process from step S631.
- the antenna driving unit 228 scans the communication target area 300 with each beam at a scanning speed according to the degree of congestion.
- a phased array is used to drive one or more antennas 21.
- the antenna driving unit 228 drives one or more antennas 21 so as to slow down the scanning speed when the degree of congestion is equal to or higher than the threshold value.
- the antenna driving unit 228 drives the antenna 21 so as to increase the scanning speed when the degree of congestion is less than the threshold value.
- the antenna driving unit 228 may drive one or more antennas 21 so as to scan a plurality of small areas with one or more beams while the irradiation ranges 301 are separated from each other.
- the mobile relay station 2b receives the terminal uplink signal transmitted from the terminal station 3 by diversity reception, MIMO reception, or the like. Therefore, according to the wireless communication system 1b according to this modification, the link budget for communication between the mobile relay station 2b and the terminal station 3 can be improved.
- the second embodiment differs from the first embodiment in that a plurality of mobile relay stations cooperate with each other.
- the difference from the first embodiment will be mainly described.
- one mobile relay station 2 sequentially transmits a transmission permission signal to each of a plurality of small areas in which the communication target area is divided. It was a structure that went on.
- the wireless communication system 1c according to the present embodiment has a plurality of mobile relay stations 2c.
- the wireless communication system 1c performs a process of allocating a small area to any of the mobile relay stations 2c (hereinafter, referred to as “distribution processing”).
- Each mobile relay station 2c transmits a terminal downlink signal to the terminal station 3 located in the irradiation range of the beam by executing the beam scanning process for the small area allocated to the own station.
- the wireless communication system 1c can alleviate the degree of communication congestion in each mobile relay station 2c, and suppresses a decrease in communication reliability even when the degree of communication congestion fluctuates. Can be done.
- FIG. 14 is a configuration diagram of the wireless communication system 1c according to the second embodiment.
- the wireless communication system 1c has a plurality of mobile relay stations 2c, a terminal station 3, and a base station 4a.
- the number of each of the plurality of mobile relay stations 2c, the terminal station 3 and the base station 4 included in the wireless communication system 1c is arbitrary, but it is assumed that the number of the terminal stations 3 is large.
- the wireless communication system 1c is a communication system that transmits information that does not require immediacy. The information transmitted from each of the plurality of terminal stations 3 is transmitted via any one of the plurality of mobile relay stations 2c and is collected by the base station 4.
- the mobile relay station 2c is an example of a relay device in which a communicable area moves with the passage of time.
- the plurality of mobile relay stations 2c are mounted on separate mobile bodies.
- the mobile relay station 2c is provided, for example, in the LEO satellite. Multiple LEO satellites fly in formation, for example, in low earth orbit.
- the terminal station 3 and the base station 4 are installed on the earth such as on the ground or at sea.
- the terminal station 3 is, for example, an IoT terminal.
- the terminal station 3 collects data such as environmental data detected by the sensor and transmits the data to the mobile relay station 2c by a wireless signal. In the figure, only two terminal stations 3 are shown.
- the mobile relay station 2c receives data transmitted from each of the plurality of terminal stations 3 by wireless signals while moving over the earth.
- the mobile relay station 2c accumulates these received data, and wirelessly transmits the accumulated data to the base station 4 at a timing when communication with the base station 4 is possible.
- the base station 4 receives
- the mobile relay station 2c includes an antenna 21, a terminal communication unit 22c, a data storage unit 23, a base station communication unit 24, an antenna 25, a relay station inter-relay communication unit 27, and an antenna 28.
- one specific mobile relay station 2c (hereinafter referred to as “hosted mobile relay station 2c”) among the plurality of mobile relay stations 2c covers each of the plurality of small areas. It is assumed that the processing (distribution processing) for allocating to any of the plurality of mobile relay stations 2c is performed.
- the terminal communication unit 22c of the mobile relay station 2c which is the host, measures the communication status of the terminal uplink communication from the plurality of terminal stations 3.
- the terminal communication unit 22c generates information (congestion degree information) indicating the degree of congestion of communication based on the measurement result. For example, the terminal communication unit 22c measures the number of access to the terminal uplink communication from the plurality of terminal stations 3 per unit time, or the reception signal strength in the frequency band of the terminal uplink communication.
- the congestion degree information may be the information itself indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication.
- the information indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication is within a predetermined threshold range. It may be information indicating a level determined based on whether or not.
- the terminal communication unit 22c acquires position information indicating the position of the terminal station 3 included in the terminal uplink communication transmitted from the plurality of terminal stations 3.
- the terminal communication unit 22c adjusts the scanning speed of the beam based on the acquired congestion degree information and position information. For example, the terminal communication unit 22c adjusts the scanning speed of the beam so that the degree of congestion of communication with the terminal station 3 included in the divided small areas is made uniform among the plurality of small areas.
- the terminal communication unit 22c performs a process (distribution process) of allocating each of the plurality of small areas in which the communication target area is divided to any of the plurality of mobile relay stations 2c.
- the terminal communication unit 22c controls, for example, so that the plurality of mobile relay stations 2c share (for example, evenly) receive the terminal uplink signals transmitted from the plurality of terminal stations 3 existing in the communication target area. ..
- the terminal communication unit 22c generates distribution information indicating the result of the distribution process.
- the distribution information is information in which area information indicating a small area and information for identifying a mobile relay station 2c allocated to the small area are associated with each other.
- the relay station-to-relay communication unit 27 of each mobile relay station 2c can transmit and receive data (inter-satellite communication) to and from each other by the antenna 28.
- data inter-satellite communication
- a communication band of 23 GHz band is used for communication between the mobile relay stations 2c.
- the relay station-to-relay communication unit 27 of the mobile relay station 2c that serves as the host transmits the distribution information generated by the terminal communication unit 22c to another mobile relay station 2c.
- the plurality of mobile relay stations 2c can share the distribution information.
- each mobile relay station 2c can recognize the small area allocated to its own station.
- the terminal communication unit 22c of the mobile relay station 2c that recognizes the small area allocated to its own station generates a transmission permission signal at the timing when communication with the small area becomes possible.
- the transmission permission signal is a control signal indicating that the terminal station 3 is permitted to transmit data such as environmental data to its own mobile relay station 2c.
- the terminal communication unit 22c transmits a terminal downlink signal including the generated transmission permission signal from the antenna 21 as a wireless signal.
- the terminal communication unit 22c transmits a signal by, for example, LPWA.
- the terminal communication unit 22c determines the channel used by the station for transmitting the terminal downlink signal by a method predetermined in the wireless communication method to be used.
- the terminal communication unit 22c stores the transmission start timing for each small area calculated in advance based on the orbit information of the LEO satellite equipped with the mobile relay station 2c and the position of each small area.
- the orbit information of LEO is information that can obtain the position, speed, moving direction, etc. of the LEO satellite at an arbitrary time.
- the transmission time may be represented by, for example, the elapsed time from the transmission start timing.
- the terminal communication unit 22c transmits the terminal downlink signal including the transmission permission signal toward the ground at the transmission start timing of the small area to be communicated.
- the terminal communication unit 22c executes the beam scanning process based on the degree of communication congestion when the terminal uplink signal is received in the communication target area.
- the mobile relay station 2c as a host transmits the distribution information itself to another mobile relay station 2c, but the present invention is not limited to this.
- the mobile relay station 2c as a host may be configured to transmit only the area information corresponding to each of the other mobile relay stations 2c.
- the specific mobile relay station 2c which is the host, performs the distribution processing, but the present invention is not limited to this.
- the mobile relay station 2c as a host may be switched based on a time zone, a position, or the like. Or, for example, even if the base station 4 acquires the congestion degree information and the position information (or area information) indicating the position of the terminal station 3 from at least one mobile relay station 2c and performs the distribution processing. good. In this case, for example, the base station 4 transmits the distribution information generated by the distribution process to the plurality of mobile relay stations 2c.
- FIG. 15 is a flow chart showing distribution processing by the mobile relay station 2c as a host.
- the terminal communication unit 22c of the mobile relay station 2c measures the communication status of the terminal uplink communication from the plurality of terminal stations 3 (step). S712).
- Information for determining whether or not the own station is a host is stored in, for example, in the terminal communication unit 22c in advance. Alternatively, the information for determining whether or not the own station is the host may be configured to be notified from the base station 4 to the mobile relay station 2c at any time.
- the terminal communication unit 22c generates information (congestion degree information) indicating the degree of congestion of communication based on the measurement result. As described above, for example, the terminal communication unit 22c measures the number of access to the terminal uplink communication from the plurality of terminal stations 3 per unit time, or the reception signal strength in the frequency band of the terminal uplink communication. As described above, the congestion degree information may be the information itself indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication. good.
- the information indicating the number of access of the terminal uplink communication from the plurality of terminal stations 3 per unit time or the received signal strength of the frequency band of the terminal uplink communication is within a predetermined threshold range. It may be information indicating a level determined based on whether or not.
- the terminal communication unit 22c acquires position information indicating the position of the terminal station 3 included in the terminal uplink communication transmitted from the plurality of terminal stations 3 (step S713).
- the terminal communication unit 22c performs a process (distribution process) of allocating each of the plurality of small areas in which the communication target area is divided to any of the plurality of mobile relay stations 2c (step S714).
- the terminal communication unit 22c controls, for example, so that the plurality of mobile relay stations 2c share (for example, evenly) receive the terminal uplink signals transmitted from the plurality of terminal stations 3 existing in the communication target area. ..
- the terminal communication unit 22c generates distribution information indicating the result of the distribution process.
- the distribution information is information in which the area information indicating the small area and the information for identifying the mobile relay station 2c allocated to the small area are associated with each other.
- the relay station-to-relay communication unit 27 of the mobile relay station 2c transmits the distribution information generated by the terminal communication unit 22c to another mobile relay station 2c (step S715).
- the terminal communication unit 22c of the mobile relay station 2c identifies a small area allocated to its own station based on the distribution information (step S716).
- the terminal communication unit 22c executes a small area distribution process based on the acquired congestion degree information and location information (step S714).
- the terminal communication unit 22c generates a transmission permission signal at a timing when communication with the small area becomes possible.
- the terminal communication unit 22c transmits a terminal downlink signal including the generated transmission permission signal from the antenna 21 as a wireless signal (step S719).
- the terminal communication unit 22c transmits the terminal downlink signal including the transmission permission signal toward the ground at the transmission start timing of the small area to be communicated.
- the terminal communication unit 22c executes the beam scanning process based on the degree of communication congestion when the terminal uplink signal is received in the same communication target area.
- the mobile relay station 2c serving as a host repeats the process from step S711.
- the terminal communication unit 22c of the mobile relay station 2c is a mobile relay station 2c that is not the host (step S711, No)
- the terminal communication unit 22c receives the distribution information transmitted from the mobile relay station 2c that is the host. Stand by (step S716).
- the terminal communication unit 22c receives the distribution information (step S716 ⁇ Yes)
- the terminal communication unit 22c identifies a small area allocated to its own station based on the distribution information (step S717).
- the terminal communication unit 22c executes a beam scanning process based on the degree of communication congestion when the terminal uplink signal is received (step S718).
- the terminal communication unit 22c generates a transmission permission signal at a timing when communication with the small area becomes possible.
- the terminal communication unit 22c transmits a terminal downlink signal including the generated transmission permission signal from the antenna 21 as a wireless signal (step S719).
- the terminal communication unit 22c transmits the terminal downlink signal including the transmission permission signal toward the ground at the transmission start timing of the small area to be communicated.
- the mobile relay station 2c which is not the host, repeats the process from step S711.
- the wireless communication system 1c performs a process (distribution process) of allocating each of the plurality of small areas to any of the plurality of mobile relay stations 2c.
- Each mobile relay station 2c transmits a transmission permission signal to a small area allocated to its own station.
- the wireless communication system 1c according to the present embodiment can alleviate the degree of communication congestion in each mobile relay station 2c, and suppresses a decrease in communication reliability even when the degree of communication congestion fluctuates. Can be done.
- each mobile relay station 2c includes the transmission permission signal in the terminal downlink signal and transmits the transmission to the terminal station 3.
- the terminal station 3 acquires the transmission permission signal indicated by the received terminal downlink signal, and determines whether or not to start transmission of the terminal uplink signal to the mobile relay station 2c based on the transmission permission signal.
- the wireless communication system 1c can control the transmission timing of the terminal uplink signal from the terminal station 3 to the mobile relay station 2c.
- the wireless communication system 1c moves sensor data transmitted from a larger number of terminal stations 3 while suppressing a decrease in communication reliability even when the degree of communication congestion fluctuates. It can be transmitted to the base station 4 via the relay station 2c.
- the points of autonomously controlling the transmission timing of each terminal station 3d located in the irradiation range 301 of the beam and the terminal uplink signal are the first embodiment and the second embodiment. It differs from the form. In the third embodiment, the differences between the first embodiment and the second embodiment will be mainly described.
- the mobile relay station 2 (2a, 2b, 2c) is a terminal transmitted from a plurality of terminal stations 3. It was configured to receive an uplink signal and measure the communication status. Then, in the wireless communication system 1 (1a, 1b, 1c), the mobile relay station 2 (2a, 2b, 2c) has a congestion degree status based on the measured communication status and each terminal included in the terminal uplink signal. The scanning speed of the beam is changed based on the position information indicating the position of the station 3. Then, the mobile relay station 2 (2a, 2b, 2c) is configured to allow the terminal station 3 to transmit the terminal uplink signal by using the spotted beam for each divided small area.
- the mobile relay station 2 (2a, 2b, 2c) is the terminal uplink signal by the terminal station 3. It was configured to control the transmission timing of.
- each terminal station 3d located in the irradiation range 301 of the beam autonomously controls the transmission timing of the terminal uplink signal.
- FIG. 16 is a configuration diagram of the wireless communication system 1d according to the third embodiment.
- the same components as those of the wireless communication system 1 in the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.
- the wireless communication system 1d has a mobile relay station 2d, a terminal station 3d, and a base station 4.
- the number of each of the mobile relay station 2d, the terminal station 3d, and the base station 4 included in the wireless communication system 1d is arbitrary, but it is assumed that the number of the terminal stations 3d is large.
- the wireless communication system 1d is a communication system that transmits information that does not require immediacy. The information transmitted from each of the plurality of terminal stations 3d is transmitted via the mobile relay station 2d and collected by the base station 4.
- the mobile relay station 2d is an example of a relay device mounted on a mobile body and whose communicable area moves with the passage of time.
- the mobile relay station 2d is provided, for example, in the LEO satellite.
- the altitude of the LEO satellite orbits over the earth.
- the terminal station 3d and the base station 4 are installed on the earth such as on the ground or at sea.
- the plurality of terminal stations 3d exist in different places from each other.
- the terminal station 3d is, for example, an IoT terminal.
- the terminal station 3d collects data such as environmental data detected by the sensor and transmits the data to the mobile relay station 2d by a wireless signal. In the figure, only two terminal stations 3d are shown.
- the mobile relay station 2d receives data transmitted from each of the plurality of terminal stations 3d by wireless signals while moving over the earth.
- the mobile relay station 2d accumulates these received data, and wirelessly transmits the accumulated data to the base station 4 at a timing when communication with the base station 4 is possible.
- the base station 4 receives the data collected by the terminal station 3d from the mobile relay station 2d.
- the mobile relay station 2d it is conceivable to use a relay station mounted on a geostationary satellite or an unmanned aerial vehicle such as a drone or HAPS.
- the mobile relay station 2d is mounted on a LEO satellite. And. Since the mobile relay station 2d mounted on the LEO satellite communicates while moving at high speed, the time during which each terminal station 3d or base station 4 can communicate with the mobile relay station 2d is limited.
- the mobile relay station 2d receives the terminal uplink signal from the terminal station 3d within the coverage at the current position during movement, and stores the waveform data of the received terminal uplink signal.
- the mobile relay station 2d wirelessly transmits a base station downlink signal including waveform data of the terminal uplink signal to the base station 4 at the timing when the base station 4 exists in the coverage.
- the base station 4 demodulates the base station downlink signal received from the mobile relay station 2d to obtain waveform data of the terminal uplink signal.
- the base station 4 obtains terminal transmission data which is the data transmitted by the terminal station 3d by demodulating and decoding the terminal uplink signal represented by the waveform data.
- the mobile relay station 2d and the terminal station 3d are configured to perform wireless communication using LPWA as an example.
- each terminal station 3d may be configured to transmit the same terminal uplink signal to the mobile relay station 2d a plurality of times.
- the wireless communication system 1d controls the transmission timing in the transmission of data from the terminal station 3d to the mobile relay station 2d in order to prevent the communication band from becoming tight.
- the transmission timing control is autonomously performed in each terminal station 3d based on the trajectory of the mobile relay station 2d and the position where the terminal station 3d exists.
- each terminal station 3d stores information indicating the trajectory of the mobile relay station 2d (hereinafter, referred to as "orbit information") in advance. Further, the terminal station 3d is provided with a positioning device such as a GPS receiver, and can generate position information indicating the position of its own station and measure the current time.
- a positioning device such as a GPS receiver
- the terminal station 3d specifies a time zone in which communication with the mobile relay station 2d is possible (hereinafter, referred to as a “communication possible time zone”) based on the orbit information and the position information indicating the position of the own station. ..
- the terminal station 3d determines a time (hereinafter, referred to as “transmission start time”) for starting transmission of the terminal uplink signal to the mobile relay station 2d based on the specified communicable time zone.
- the terminal station 3d measures the current time and starts transmitting the terminal uplink signal to the mobile relay station 2d at the timing when the transmission start time is reached.
- the mobile relay station 2d determines, for example, a time randomly selected from the communicable time zones as the transmission start time. This prevents the transmission of the terminal uplink signal from the large number of terminal stations 3d to the mobile relay station 2d at the same time even when a large number of terminal stations 3d are present at positions close to each other. be able to. Thereby, the wireless communication system 1d according to the present embodiment can prevent the communication band of the mobile relay station 2d from becoming tight.
- the terminal station 3d does not determine a time randomly selected from the communicable time zones as the transmission start time, but instead determines, for example, the position (for example, latitude and longitude) of its own station obtained by the positioning device.
- the time calculated based on a predetermined calculation rule may be determined as the transmission start time.
- the mobile relay station 2d includes an antenna 21, a terminal communication unit 22d, a data storage unit 23, a base station communication unit 24, and an antenna 25.
- the terminal communication unit 22d has a reception unit 221 and a reception waveform recording unit 222.
- the receiving unit 221 receives the terminal uplink signal by the antenna 21.
- the reception waveform recording unit 222 samples the reception waveform of the terminal uplink signal received by the reception unit 221 and generates waveform data showing the value obtained by the sampling.
- the reception waveform recording unit 222 writes the reception waveform information including the reception time of the terminal uplink signal in the antenna 21 and the generated waveform data to the data storage unit 23.
- the data storage unit 23 stores the received waveform information written by the received waveform recording unit 222.
- the configuration of the base station communication unit 24 and the base station 4 of the mobile relay station 2d is the same as the configuration of the base station communication unit 24 and the base station 4 of the mobile relay station 2 of the wireless communication system 1 according to the first embodiment described above. be.
- the terminal station 3d includes a data storage unit 31, a transmission unit 32, one or more antennas 33, a transmission control unit 35d, a position information generation unit 36, and an orbit information storage unit 37.
- the data storage unit 31 stores sensor data and the like.
- the transmission unit 32 reads sensor data from the data storage unit 31 as terminal transmission data, and transmits a terminal uplink signal including the read terminal transmission data from the antenna 33 by a wireless signal.
- the transmission unit 32 transmits a signal by, for example, LPWA.
- the transmission unit 32 determines the channel and transmission timing used by the station to transmit the terminal uplink signal by a method predetermined in the wireless communication method to be used. Further, the transmission unit 32 may form a beam of signals transmitted from a plurality of antennas 33 by a method predetermined in the wireless communication method to be used.
- the orbit information storage unit 37 stores in advance information (orbit information) indicating the orbit of the mobile relay station 2d.
- the position information generation unit 36 includes a positioning device such as a GPS receiver, and specifies the position of its own station.
- the position information generation unit 36 generates position information indicating the position of the specified own station.
- the transmission control unit 35d includes the transmission unit 32 and the mobile relay station 2d based on the orbit information stored in the orbit information storage unit 37 and the position information indicating the position of the own station specified by the position information generation unit 36. Specify the time zone (communication possible time zone) when communication is possible.
- the transmission control unit 35d determines a time (transmission start time) at which transmission of the terminal uplink signal to the mobile relay station 2d is started based on the specified communicable time zone.
- the transmission start time is determined within the range of the communicable time zone.
- the transmission control unit 35d measures the current time and controls the transmission unit 32 so as to start the transmission of the terminal uplink signal to the mobile relay station 2d at the timing when the transmission start time is reached.
- the transmission unit 32 starts transmitting the terminal uplink signal to the mobile relay station 2d under the control of the transmission control unit 35d.
- the mobile relay station 2d determines, for example, a time randomly selected within the communicable time zone as the transmission start time.
- the mobile relay station 2d scans the communication target area with a beam according to the transmission start time.
- the wireless communication system 1d according to the present embodiment can prevent the communication band of the mobile relay station 2d from becoming tight.
- the terminal station 3d may determine, for example, a time calculated based on the position (for example, latitude and longitude) of its own station obtained by the positioning device and a predetermined calculation rule as the transmission start time. good.
- FIG. 17 is a flow chart showing a transmission timing control process of the terminal uplink signal by the terminal station 3d.
- the transmission control unit 35d of the terminal station 3d acquires the orbit information stored in the orbit information storage unit 37 (step S811).
- the receiving unit 34 of the terminal station 3 receives the terminal downlink signal by the antenna 33 (step S812).
- the transmission control unit 35 of the terminal station 3 acquires a transmission permission signal from the terminal downlink signal received by the reception unit 34 (step S813).
- the position information generation unit 36 of the terminal station 3d specifies the position of its own station by, for example, a positioning device such as a GPS receiver (step S814).
- the position information generation unit 36 generates position information indicating the position of the specified own station.
- the transmission control unit 35d sets a time zone (communication possible time zone) during which communication between the transmission unit 32 and the mobile relay station 2d is possible based on the orbit information and the position information generated by the position information generation unit 36. Specify (step S815).
- the transmission control unit 35d determines a time (transmission start time) at which transmission of the terminal uplink signal to the mobile relay station 2d is started (transmission start time) based on the specified communicable time zone (step S816).
- the transmission control unit 35d measures the current time and waits until the current time reaches the transmission start time (step S817 / No).
- the transmission control unit 35d receives the terminal uplink signal to the mobile relay station 2d.
- the transmission unit 32 is controlled so as to start transmission.
- the transmission unit 32 starts transmitting the terminal uplink signal to the mobile relay station 2d (step S818).
- the terminal station 3d repeats the processes after step S811.
- each terminal station 3d autonomously controls the transmission timing of the terminal uplink signal.
- Each terminal station 3d specifies a communicable time zone for communication with the mobile relay station 2d based on the track information indicating the trajectory of the mobile relay station 2d and the position information indicating the position of its own station.
- the terminal station 3d determines the transmission start time of the terminal uplink signal based on the specified communicable time zone. At this time, the terminal station 3d randomly determines, for example, the transmission start time within the range of the communicable time zone.
- the wireless communication system 1d can realize a wide coverage without increasing the number of beams more than necessary.
- the wireless communication system 1d can reduce the degree of communication congestion in the mobile relay station 2d. As a result, the wireless communication system 1d can suppress a decrease in communication reliability even when the degree of communication congestion fluctuates.
- the terminal station 3d stores in advance the correspondence information associated with the specific mobile relay station 2d for each area (for example, the above-mentioned small area).
- the terminal station 3d recognizes the area including the specified position of its own station by specifying the position of its own station.
- the terminal station 3d identifies the mobile relay station 2d corresponding to the area including the position of its own station by referring to the above correspondence information.
- the terminal station 3d transmits the terminal uplink signal to the specified mobile relay station 2d.
- the terminal station 3d specifies the communicable time zone for communication with the mobile relay station 2d based on the track information of the specified mobile relay station 2d and the position information indicating the position of the own station.
- the terminal station 3d determines the transmission start time of the terminal uplink signal to the mobile relay station 2d within the specified communicable time zone.
- the terminal station 3d randomly determines, for example, the transmission start time within the range of the communicable time zone.
- the wireless communication system 1d can realize a wide coverage without increasing the number of beams more than necessary.
- the wireless communication system 1d can reduce the degree of communication congestion in the mobile relay station 2d. As a result, the wireless communication system 1d can suppress a decrease in communication reliability even when the degree of communication congestion fluctuates.
- the mobile relay station 2d transmits, for example, a beacon or the like toward the ground at predetermined intervals.
- each terminal station 3d estimates the position of the mobile relay station 2d based on the beacon or the like.
- the terminal station 3d corrects the track information of the mobile relay station 2d stored in the track information storage unit 37 based on the estimated position of the mobile relay station 2d and the current time.
- the terminal station 3d specifies a communicable time zone for communication with the mobile relay station 2d based on the corrected orbit information and the position information indicating the position of the own station.
- the terminal station 3d determines the transmission start time of the terminal uplink signal based on the specified communicable time zone. At this time, the terminal station 3d randomly determines, for example, the transmission start time within the range of the communicable time zone.
- the wireless communication system according to this modification further improves the accuracy in calculating the communicable time zone of communication between the mobile relay station 2d and each terminal station 3d. Can be made to.
- a relay device (movable relay device) provided in a mobile body and a plurality of communication devices existing at different locations communicate wirelessly with each other.
- the relay device is a mobile relay station 2, 2a, 2b, 2c, 2d in the embodiment
- the first communication device is the terminal station 3 in the embodiment
- the second communication device is the base station 4 in the embodiment. ..
- the relay device includes a relay device receiving unit, a measuring unit, a relay device control unit, and a relay device transmitting unit.
- the relay device receiving unit is the antenna 21 and the receiving units 221 and 221b in the embodiment
- the measuring unit is the communication status measuring unit 223 and 223b in the embodiment
- the relay device control unit is the area control in the embodiment. It is a unit 224, 224b
- the relay device transmission unit is an antenna 21 and a transmission unit 226, 226b.
- the relay device receiving unit receives signals transmitted from a plurality of communication devices and including position information indicating the position of the communication device.
- the signal is a terminal uplink signal in the embodiment.
- the measuring unit measures the degree of communication congestion in the relay device receiving unit.
- the relay device control unit divides the communication target area into a plurality of small areas based on the positions of the plurality of communication devices and the degree of communication congestion, and generates area information indicating the positions of the small areas.
- the relay device transmission unit transmits a plurality of area information in order when the own device is located within a communicable range with the communication device.
- the communication device includes a storage unit, a communication device receiving unit, a communication device control unit, and a communication device transmission unit.
- the storage unit is the data storage unit 31 in the embodiment
- the communication device receiving unit is the antenna 33 and the receiving unit 34 in the embodiment
- the communication device control unit is the transmission control unit 35 in the embodiment.
- the communication device transmission unit is the antenna 33 and the transmission unit 32 in the embodiment.
- the storage unit stores transmission data to be transmitted to the relay device.
- the transmission data is data such as environmental data in the embodiment.
- the communication device receiving unit receives the area information.
- the communication device control unit determines whether or not the self-position is included in the small area based on the area information.
- the communication device transmission unit transmits a signal including transmission data and position information indicating the self-position to the relay device.
- the signal is a terminal uplink signal in the embodiment.
- the relay device control unit may divide the communication target area into a plurality of small areas where the degree of communication congestion is uniform.
- the degree of communication congestion may be information indicating the number of signal accesses per unit time in the relay device receiving unit and information indicating the signal reception signal strength.
- the signal is a terminal uplink signal in the embodiment.
- the relay device is provided in a moving body that orbits the earth, and the relay device transmission unit may transmit the area information generated in the previous orbit to the communication device.
- the moving body is a low earth orbit satellite
- the communication device is provided in the terminal device including the sensor
- the signal may be a signal indicating the sensor data measured by the terminal device.
- the wireless communication system may further have a base station device that wirelessly communicates with the relay device.
- the base station device is the base station 4 in the embodiment.
- the relay device may transmit a signal based on the signal transmitted from each of the plurality of communication devices to the base station device when the own device is located within a range in which the own device can communicate with the base station device.
- a signal based on a signal transmitted from each of a plurality of communication devices is a base station downlink signal in the embodiment.
- the communication device that wirelessly communicates with the relay device provided in the mobile body includes a storage unit, a control unit, and a transmission unit.
- the storage unit is the data storage unit 31 and the orbital information storage unit 37 in the embodiment
- the control unit is the transmission control unit 35d in the embodiment
- the transmission unit is the antenna 33 and the transmission unit 32 in the embodiment. be.
- the storage unit stores transmission data to be transmitted to the relay device and trajectory information indicating the trajectory of the moving object.
- the transmission data is data such as environmental data in the embodiment.
- the control unit identifies a communicable time zone, which is a time zone in which communication with the relay device is possible, based on the orbit information and the self-position.
- the transmission unit transmits transmission data to the relay device during the communicable time zone.
- the transmitting unit may transmit transmission data at a randomly determined time within the range of the communicable time zone.
- the mobile body on which the mobile relay station is mounted is a LEO satellite has been described, but a geostationary satellite, a drone, a HAPS, or the like has been described. It may be another aircraft flying over the sky.
- FIG. 18 is a diagram showing a hardware configuration example of a functional unit of the mobile relay station 2 according to each embodiment.
- a part of the mobile relay stations 2, 2a, 2b, 2c, 2d, the terminal stations 3, 3d, and the base stations 4, 4a, 4b in each of the above-described embodiments may be realized by a computer.
- a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed.
- the term "computer system” as used herein includes hardware such as an OS and peripheral devices.
- the "computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, and a storage device such as a hard disk built in a computer system.
- a “computer-readable recording medium” is a communication line for transmitting a program via a network such as the Internet or a communication line such as a telephone line, and dynamically holds the program for a short period of time. It may also include a program that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or a client in that case.
- the above program may be for realizing a part of the above-mentioned functions, and may be further realized for realizing the above-mentioned functions in combination with a program already recorded in the computer system. It may be realized by using a programmable logic device such as FPGA (Field Programmable Gate Array).
- FPGA Field Programmable Gate Array
- a part or all of each functional unit of the wireless communication system is stored in a memory 102 in which a processor 100 such as a CPU (Central Processing Unit) has a non-volatile recording medium (non-temporary recording medium). It is realized as software by executing the program.
- the program may be recorded on a computer-readable recording medium.
- Computer-readable recording media include, for example, flexible disks, magneto-optical disks, portable media such as ROM (ReadOnlyMemory) and CD-ROM (CompactDiscReadOnlyMemory), and storage of hard disks built into computer systems. It is a non-temporary recording medium such as the device 101.
- each functional part of the wireless communication system is, for example, an electronic circuit (electronic) using an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), an FPGA, or the like. It may be realized by using hardware including circuit or circuitry).
- Memory unit, 262 Control unit, 263 ... Transmission data modulation unit, 264 ... MIMO transmitter, 300 ... Communication target area, 301 ... Irradiation range, 410 ... Antenna station, 420 ... MIMO receiver, 430 ... Base station signal reception processing unit, 441 ... Terminal signal demodulation unit, 442 ... Terminal signal decoding unit, 450 ... Terminal signal reception processing unit, 451 ... Distributor, 452, 452-1 to 452-N ... Terminal signal demodulation unit, 453 ... Synthetic unit, 454 ... Terminal signal decoding unit
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Abstract
Description
図1は、第1の実施形態による無線通信システム1の構成図である。無線通信システム1は、移動中継局2と、端末局3と、基地局4とを有する。無線通信システム1が有する移動中継局2、端末局3及び基地局4のそれぞれの数は任意であるが、端末局3の数は多数であることが想定される。無線通信システム1は、即時性が要求されない情報の伝送を行う通信システムである。複数の端末局3からそれぞれ送信された情報は、移動中継局2を介して伝送され、基地局4によって収集される。
データ収集処理における各装置の構成を説明する。
移動中継局2は、アンテナ21と、端末通信部22と、データ記憶部23と、基地局通信部24と、アンテナ25とを備える。
図2は、ビームの走査例を示す図である。アンテナ21は、照射範囲が絞られたビームを、通信対象エリア300(サービスエリア)の小エリアに照射する。これによって、ビームの照射範囲301に位置している端末局3-1のみが、端末アップリンク信号を移動中継局2に送信する。端末通信部22は、アンテナ21を用いて、通信対象エリア300をビームで走査する。図2に記載の矢印は走査方向の例を表す。走査されたビームの照射範囲301に端末局3-2が入るまで、端末局3-2は、端末アップリンク信号を移動中継局2に送信しない。
図3は、ビームの走査処理を示すフロー図である。エリア制御部224は、通信対象エリア300に対してビームを照射することが可能となる所定位置に移動中継局2が到着したか否かを判定する。例えば、エリア制御部224は、通信対象エリア300の上空に移動中継局2が到着したか否かを判定する(ステップS101)。所定位置に移動中継局2が到着していないと判定された場合(ステップS101・No)、エリア制御部224は、所定時間の経過後に、ステップS101を再実行する。
移動中継局2の基地局通信部24が有する制御部242は、記憶部241に記憶された送信開始タイミングが現在時刻であることを検出すると、受信波形情報の送信を送信データ変調部243及び送信部244に指示する(ステップS211)。送信データ変調部243は、データ記憶部23に蓄積していた受信波形情報を送信データとして読み出し、読み出した送信データを変調し、基地局ダウンリンク信号を生成する。送信部244は、送信データ変調部243が生成した基地局ダウンリンク信号を無線信号によりアンテナ25から送信する(ステップS212)。移動中継局2は、ステップS211からの処理を繰り返す。
送信制御処理における各装置の構成を説明する。
移動中継局2の構成について説明する。図1に示されるように、移動中継局2は、通信状況測定部223と、エリア制御部224と、記憶部225と、送信部226と、位置情報取得部227と、アンテナ駆動部228とをさらに備える。
送信制御部35は、受信部34によって受信された端末ダウンリンク信号から送信許可信号を取得する。
図6は、無線通信システム1による送信制御処理を示すフロー図である。移動中継局2のエリア制御部224は、アンテナ駆動部228を用いて、ビームの走査処理を実行する(ステップS311)。移動中継局2のエリア制御部224は、送信許可信号を生成する(ステップS312)。送信部226は、エリア制御部224によって生成された送信許可信号を取得し、取得された送信許可信号を含む端末ダウンリンク信号を、アンテナ21から無線信号により送信する(ステップS313)。移動中継局2は、ステップS311からの処理を繰り返す。
本変形例では、移動中継局は、複数本のアンテナにより基地局ダウンリンク信号を送信する。以下では、基地局ダウンリンク信号の送信に、MIMO(Multiple Input Multiple Output)を用いる場合を例にして、第1の実施形態との差分を中心に説明する。
端末局3から端末アップリンク信号を送信する場合の無線通信システム1aの処理は、図4に示す第1の実施形態の無線通信システム1の処理と同様である。
本変形例では、移動中継局は、複数のアンテナにより端末アップリンク信号を受信し、複数のアンテナにより端末ダウンリンク信号を送信する。以下では、第1の実施形態の変形例1との差分を中心に説明する。
図11は、ビームの走査処理を示すフロー図である。エリア制御部224は、通信対象エリア300に対してビームを照射することが可能となる所定位置に移動中継局2が到着したか否かを判定する(ステップS401)。所定位置に移動中継局2が到着していないと判定された場合(ステップS401・No)、エリア制御部224は、所定時間の経過後に、ステップS401を再実行する。
第2の実施形態では、複数の移動中継局が連携するという点が、第1の実施形態と相違する。第2の実施形態では、第1の実施形態との差分を中心に説明する。
エリア情報のみを送信する構成であってもよい。
図15は、ホストとなる移動中継局2cによる振分処理を示すフロー図である。
移動中継局2cの端末通信部22cは、自局がホストとなる移動中継局2cである場合(ステップS711・Yes)、複数の端末局3からの端末アップリンク通信の通信状況を測定する(ステップS712)。なお、自局がホストであるか否かを判定するための情報は、例えば予め端末通信部22cに記憶されている。又は、自局がホストであるか否かを判定するための情報は、基地局4から移動中継局2cへ随時通知される構成であってもよい。
第3の実施形態では、ビームの照射範囲301に位置している各々の端末局3d、端末アップリンク信号の送信タイミングを自律的に制御するという点が、第1の実施形態及び第2の実施形態と相違する。第3の実施形態では、第1の実施形態及び第2の実施形態との差分を中心に説明する。
図16に示されるように、移動中継局2dは、アンテナ21と、端末通信部22dと、データ記憶部23と、基地局通信部24と、アンテナ25とを備える。
図17は、端末局3dによる端末アップリンク信号の送信タイミング制御処理を示すフロー図である。
端末局3dは、ステップS811以降の処理を繰り返す。
移動中継局2dが複数存在する場合には、以下のような構成にすることも考えられる。
移動中継局2dから端末局3dへ、例えばビーコン等の、位置情報を推定可能な信号(以下、「ビーコン等」という。)を送信することができる場合には、以下のような構成にすることも考えられる。
2、2a、2b、2c、2d…移動中継局,
3、3d…端末局,
4、4a、4b…基地局,
21、21-1~21-N…アンテナ,
22、22b、22c、22d…端末通信部,
23…データ記憶部,
24…基地局通信部,
25…アンテナ,
26…基地局通信部,
27…中継局間通信部,
28…アンテナ,
31…データ記憶部,
32…送信部,
33…アンテナ,
34…受信部,
35、35d…送信制御部,
36…位置情報生成部,
41…アンテナ,
42…受信部,
43…基地局信号受信処理部,
44…端末信号受信処理部,
100…プロセッサ,101…記憶装置,102…メモリ,
221、221b、221b-1~221b-N…受信部,
222、222b、222b-1~222b-N…受信波形記録部,
223、223b…通信状況測定部,
224、224b…エリア制御部,
225…記憶部,
226、226b…送信部,
227、227b…位置情報取得部,
228…アンテナ駆動部,
241…記憶部,
242…制御部,
243…送信データ変調部,
244…送信部,
261…記憶部,
262…制御部,
263…送信データ変調部,
264…MIMO送信部,
300…通信対象エリア,301…照射範囲,
410…アンテナ局,
420…MIMO受信部,
430…基地局信号受信処理部,
441…端末信号復調部,
442…端末信号復号部,
450…端末信号受信処理部,
451…分配部,
452、452-1~452-N…端末信号復調部,
453…合成部,
454…端末信号復号部
Claims (7)
- 通信対象エリアを分割する複数の小エリアのうちの1以上の小エリアに位置している1以上の第1通信装置と、中継装置と、第2通信装置とを有する無線通信システムであって、
前記中継装置は、
前記通信対象エリアよりも狭い照射範囲の1以上のビームを前記通信対象エリアに照射しながら前記複数の小エリアを前記ビームで走査するように1以上のアンテナを駆動するアンテナ駆動部と、
前記照射範囲に位置している前記第1通信装置から送信された第1無線信号を前記アンテナから取得する受信部と、
前記第1無線信号に応じた第2無線信号を前記第2通信装置に送信する送信部とを備える、
無線通信システム。 - 前記第1無線信号の送信頻度に基づいて通信の混雑度を導出する通信状況測定部を備え、
前記アンテナ駆動部は、前記混雑度に応じた走査速度で前記通信対象エリア内をビームで走査するように前記アンテナを駆動する、請求項1に記載の無線通信システム。 - 前記アンテナ駆動部は、前記混雑度が閾値以上である場合に前記走査速度を遅くするように前記アンテナを駆動し、前記混雑度が閾値未満である場合に前記走査速度を速くするように前記アンテナを駆動する、請求項2に記載の無線通信システム。
- 前記アンテナ駆動部は、前記照射範囲同士を離した状態で、前記複数の小エリアを1以上の前記ビームで走査するように、前記アンテナを駆動する、請求項1から請求項3のいずれかの一項に記載の無線通信システム。
- 通信対象エリアを分割する複数の小エリアのうちの1以上の小エリアに位置している1以上の第1通信装置と、第2通信装置と、移動可能な中継装置とを有する無線通信システムにおける前記中継装置であって、
前記通信対象エリアよりも狭い照射範囲の1以上のビームを前記通信対象エリアに照射しながら前記複数の小エリアを前記ビームで走査するように1以上のアンテナを駆動するアンテナ駆動部と、
前記照射範囲に位置している前記第1通信装置から送信された第1無線信号を前記アンテナから取得する受信部と、
前記第1無線信号に応じた第2無線信号を前記第2通信装置に送信する送信部と
を備える中継装置。 - 通信対象エリアを分割する複数の小エリアのうちの1以上の小エリアに位置している1以上の第1通信装置と、中継装置と、第2通信装置とを有する無線通信システムが実行する無線通信方法であって、
前記中継装置は、
前記通信対象エリアよりも狭い照射範囲の1以上のビームを前記通信対象エリアに照射しながら前記複数の小エリアを前記ビームで走査するように1以上のアンテナを駆動し、
前記照射範囲に位置している前記第1通信装置から送信された第1無線信号を前記アンテナから取得し、
前記第1無線信号に応じた第2無線信号を前記第2通信装置に送信する、
無線通信方法。 - 請求項1から請求項4のいずれか一項に記載の無線通信システムの中継装置としてコンピュータを機能させるためのプログラム。
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Citations (7)
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JPH0759152A (ja) * | 1993-08-11 | 1995-03-03 | Nippon Telegr & Teleph Corp <Ntt> | マルチビーム無線通信用無線局装置 |
JPH07321721A (ja) * | 1994-05-23 | 1995-12-08 | Tasada Kosakusho:Kk | 単一波マルチポイント衛星通信方法 |
JPH10145275A (ja) * | 1996-10-30 | 1998-05-29 | Motorola Inc | トラフィック要求に応答するインテリジェント・ビーム形成方法およびシステム |
WO2001041531A2 (en) * | 1999-12-10 | 2001-06-14 | Motorola, Inc. | Digital beamforming acquisition system |
JP2009526501A (ja) * | 2006-02-09 | 2009-07-16 | イーグル リヴァー ホールディングス リミテッド ライアビリティ カンパニー | 時分割複信を利用する通信のためのシステム及び方法 |
WO2011139991A1 (en) * | 2010-05-02 | 2011-11-10 | Viasat, Inc | Flexible capacity satellite communications system |
JP2013012976A (ja) * | 2011-06-30 | 2013-01-17 | Mitsubishi Electric Corp | 制御局、中継器、送信器、通信システムおよび通信方法 |
-
2020
- 2020-12-23 WO PCT/JP2020/048234 patent/WO2022137397A1/ja active Application Filing
- 2020-12-23 US US18/267,486 patent/US20240048224A1/en active Pending
- 2020-12-23 JP JP2022570859A patent/JP7498409B2/ja active Active
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
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JPH0759152A (ja) * | 1993-08-11 | 1995-03-03 | Nippon Telegr & Teleph Corp <Ntt> | マルチビーム無線通信用無線局装置 |
JPH07321721A (ja) * | 1994-05-23 | 1995-12-08 | Tasada Kosakusho:Kk | 単一波マルチポイント衛星通信方法 |
JPH10145275A (ja) * | 1996-10-30 | 1998-05-29 | Motorola Inc | トラフィック要求に応答するインテリジェント・ビーム形成方法およびシステム |
WO2001041531A2 (en) * | 1999-12-10 | 2001-06-14 | Motorola, Inc. | Digital beamforming acquisition system |
JP2009526501A (ja) * | 2006-02-09 | 2009-07-16 | イーグル リヴァー ホールディングス リミテッド ライアビリティ カンパニー | 時分割複信を利用する通信のためのシステム及び方法 |
WO2011139991A1 (en) * | 2010-05-02 | 2011-11-10 | Viasat, Inc | Flexible capacity satellite communications system |
JP2013012976A (ja) * | 2011-06-30 | 2013-01-17 | Mitsubishi Electric Corp | 制御局、中継器、送信器、通信システムおよび通信方法 |
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US20240048224A1 (en) | 2024-02-08 |
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