WO2022118403A1 - 無線通信装置及び無線通信方法 - Google Patents
無線通信装置及び無線通信方法 Download PDFInfo
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- 238000012545 processing Methods 0.000 description 50
- 238000013500 data storage Methods 0.000 description 19
- 238000006243 chemical reaction Methods 0.000 description 15
- 230000007613 environmental effect Effects 0.000 description 10
- 238000005259 measurement Methods 0.000 description 10
- 238000012986 modification Methods 0.000 description 10
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- 238000001514 detection method Methods 0.000 description 6
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- 101100172132 Mus musculus Eif3a gene Proteins 0.000 description 3
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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
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18513—Transmission in a satellite or space-based system
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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
- H04B7/155—Ground-based stations
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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 device and a wireless communication method.
- IoT terminals Internet of Things terminal stations
- a plurality of terminal stations may be installed at a position where it is difficult to install a base station.
- Locations that are difficult to install are, for example, buoys or ships on the sea, or mountainous areas.
- Multiple terminal stations use sensors at their respective locations to generate environmental information (eg, temperature, room temperature, acceleration or luminosity information).
- the plurality of terminal stations transmit the generated environmental information to the device on the cloud side by a wireless signal.
- the device on the cloud side collects environmental information at a plurality of locations where it is difficult to install a base station from a plurality of terminal stations.
- LPWA Low Power Wide Area
- LPWA Low Power Wide Area
- a communication satellite system (hereinafter referred to as "satellite IoT system") that collects data from a terminal station using wireless communication such as LPWA has been studied.
- satellite IoT system a low earth orbit satellite may be used as a communication satellite.
- the low earth orbit satellite moving over the sky gives a control signal (hereinafter referred to as "transmission permission signal") indicating that the terminal uplink signal is permitted to be transmitted to a large number of terminals on the ground.
- transmission permission signal a control signal
- Each terminal station that has received the transmission permission signal transmits a radio signal including data such as environmental information to a low earth orbit satellite as a terminal uplink signal.
- the terminal uplink signals may collide with each other because the terminal uplink signals are transmitted at the same timing.
- the CSMA / CA method is a method adopted in a wireless LAN system standardized by 802.11.
- the backoff counter value is updated by subtracting the subtraction value from the backoff counter value.
- FIG. 10 is a diagram showing an example of a conventional relationship between the position of the mobile relay station 20 with respect to each terminal station 30 and each variable value (each subtraction value) used for subtracting the backoff counter value.
- the elevation angle of the mobile relay station 20 seen from the terminal station 30-5 is larger than the elevation angle of the mobile relay station 20 seen from the terminal station 3-M (this "M" is an integer of 10 or more).
- the terminal station 30 when the terminal station 30 receives the transmission permission signal, the terminal station 30 sets a random number uniformly distributed in the range from 0 to CW (Contention Window) as the backoff counter value, and the unit time is set. The subtraction value is subtracted from the backoff counter value each time. This subtraction value (integer value) is 1. The value "1" described in each terminal station 30 shown in FIG. 10 represents each subtraction value.
- the terminal station 30 transmits the terminal uplink signal 100 (radio signal) to the low earth orbit satellite at the timing when the backoff counter value becomes 0. This makes it possible to uniformly distribute the transmission timings of a large number of terminal stations 30 and reduce the probability of collision between the terminal uplink signals 100.
- Multiple terminal uplink signals transmitted from multiple terminal stations arrive at the relay device mounted on the low earth orbit satellite from different directions.
- the relay device controls the direction of the received beam by using the receiving array antenna of the low earth orbit satellite.
- the relay device separates terminal uplink signals transmitted from a plurality of terminal stations at the same timing by controlling the direction of the received beam.
- the accuracy with which the relay device separates the terminal uplink signals transmitted from the terminal stations close to each other differs depending on the direction of the terminal uplink signals arriving at the receiving array antenna surface of the low earth orbit satellite.
- the accuracy of separating the terminal uplink signal 100-9 and the terminal uplink signal 100-M by the relay device is almost the same in the arrival direction, so that the terminal uplink signal 100-5 and the terminal uplink signal are separated. It is low compared to the accuracy with which the relay device separates 100-7. Therefore, in the transmission timing control disclosed in Non-Patent Document 1, the accuracy of separating the terminal uplink signals from each other by the relay device is insufficient. As described above, it may not be possible to improve the accuracy of separating the radio signals received from a plurality of terminal stations.
- an object of the present invention is to provide a wireless communication device and a wireless communication method capable of improving the accuracy of separating wireless signals received from a plurality of terminal stations.
- One aspect of the present invention is a radio including a transmission control unit that determines an earlier transmission timing as the elevation angle of the relay device seen from the own wireless communication device is larger, and a transmission unit that transmits a radio signal to the relay device at the transmission timing. It is a communication device.
- One aspect of the present invention is a wireless communication method executed by a wireless communication device, which is a transmission control step that determines a transmission timing that is faster as the elevation angle of the relay device as seen from the own wireless communication device is larger, and a wireless signal at the transmission timing.
- a wireless communication method including a transmission step of transmitting to the relay device.
- FIG. 1 is a diagram showing a configuration example of the wireless communication system 1 in the 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 is arbitrary.
- it is assumed that the number of terminal stations 3 is large.
- the wireless communication system 1 wirelessly communicates information that does not require immediacy. Data such as environmental information transmitted from each of the plurality of terminal stations 3 is collected by the base station 4 via the mobile relay station 2 (relay device).
- the mobile relay station 2 is mounted on the mobile body.
- the mobile relay station 2 moves with the movement of the moving body.
- the area (communication target area) to be communicated by the mobile relay station 2 is determined according to the position of the mobile body.
- the moving object is, for example, a LEO (Low Earth Orbit) satellite or an unmanned aerial vehicle.
- the altitude of the LEO satellite is, for example, 2000 km or less.
- the LEO satellite orbits the earth in about 1.5 hours per orbit.
- the mobile relay station 2 and the terminal station 3 execute wireless communication using LPWA as an example.
- LPWA includes wireless communication such as LoRaWAN (registered trademark) and Sigfox (registered trademark), but any wireless communication method can be used.
- 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.
- the mobile relay station 2 transmits a transmission permission signal indicating that the terminal uplink signal (wireless signal from the terminal station to the mobile relay station) is permitted to be transmitted, and the terminal downlink signal (from the mobile relay station to the terminal station). It is transmitted in advance to the terminal station 3 using a wireless signal).
- the terminal downlink signal contains information on the upper limit.
- This upper limit is, for example, the value of the contention window.
- the upper limit value is set as one of (1) to (4) shown below, for example.
- An upper limit is set as a value obtained by dividing the total number of terminal stations 3 in a plurality of communication target areas in which the mobile relay station 2 passes over the sky by the length of time.
- This predetermined period is, for example, the period of the number of return days of the mobile relay station 2 orbiting the earth.
- the upper limit value in (1) above is the length of time that the mobile relay station 2 passes over the plurality of communication target areas in a predetermined period, and the total number of terminal stations 3 in the plurality of communication target areas is the total number. The value of the result of division.
- the upper limit value in (2) above is the length of time that the mobile relay station 2 passes over the communication target area, and is the value obtained by dividing the total number of terminal stations 3 in the communication target area. be.
- An upper limit is set as the value of the result of multiplying the number of signals (hereinafter referred to as "separable number") and the value of the result of division in (1) or (2) above.
- This predetermined range is, for example, a range of about 20 degrees with respect to the front direction of the plurality of antennas 21 (array antennas).
- the separable number is predetermined based on the result of prediction (simulation) or actual measurement of signal separation.
- the upper limit value in (3) above is a radio signal that can be separated from a plurality of radio signals simultaneously arriving at the mobile relay station 2 from each terminal station 3 uniformly distributed in a predetermined range in the communication target area. It is the value of the result of multiplying the number of and the value of the result of division in the above (1) or (2).
- the upper limit value of (3) above may be corrected according to the amount of interference of the interference signal with respect to the terminal uplink signal. For example, an interference signal arriving from a predetermined communication station other than the terminal station 3 (for example, another terminal station using the IoT platform on the ground) reduces the separable number of terminal uplink signals (desired signals). Therefore, the value obtained by correcting the upper limit value of the above (3) by the number of reductions due to the interference signal is determined as the corrected upper limit value. For example, the upper limit value after this correction is set to a larger value as the amount of interference increases.
- the upper limit value in (4) above is a value corrected according to the amount of interference with the radio signal.
- the terminal station 3 and the base station 4 are installed on the ground or at sea.
- the terminal station 3 is, for example, an IoT terminal.
- Each terminal station 3 is installed at a different position from each other, for example.
- the terminal station 3 collects data such as environmental information detected by using a sensor at the installed position.
- the terminal station 3 transmits the terminal uplink signal to the mobile relay station 2 according to the information of the upper limit value included in the terminal downlink signal and the elevation angle of the mobile relay station 2 seen from the terminal station 3. Adjust (Transmission frequency).
- the terminal station 3 transmits a terminal uplink signal (wireless signal) including data such as environmental information to the mobile relay station 2.
- the mobile relay station 2 receives the terminal uplink signals transmitted from each of the plurality of terminal stations 3 while moving over the earth.
- the mobile relay station 2 receives a terminal uplink signal from each terminal station 3 within the coverage at the current position during movement.
- the mobile relay station 2 mounted on the LEO satellite communicates while moving at high speed. Therefore, the time during which each terminal station 3 or base station 4 and the mobile relay station 2 can communicate with each other is limited. Further, the terminal station 3 uses wireless communication methods having various specifications. Therefore, the mobile relay station 2 stores the waveform data of the received terminal uplink signal. That is, the mobile relay station 2 accumulates the received waveform of the received radio signal. The mobile relay station 2 transmits the accumulated received waveform to the base station 4 using the base station downlink signal at the timing when communication with the base station 4 is possible.
- the base station 4 acquires the received waveform of the terminal uplink signal in the mobile relay station 2 from the mobile relay station 2.
- the base station 4 executes signal processing and decoding processing on the received waveform transmitted from the terminal station 3 using the base station downlink signal. As a result, the base station 4 obtains data such as environmental information transmitted from the terminal station 3.
- FIG. 2 is a diagram showing a configuration example of the wireless communication system 1 in the embodiment.
- the mobile relay station 2 includes a plurality of antennas 21 (array antennas), a terminal communication unit 22, a data storage unit 23, a base station communication unit 24, and a plurality of antennas 25 (array antennas).
- the terminal communication unit 22 includes a plurality of reception units 221, a plurality of reception waveform recording units 222, a communication status measurement unit 223, a timing control unit 224, a storage unit 225, a transmission unit 226, and a plurality of frequency conversion units. It is equipped with 227.
- the receiving unit 221 receives a terminal uplink signal from each terminal station 3 in the coverage by MIMO (Multi Input Multi Output) communication using a plurality of antennas 21.
- the frequency conversion unit 227 executes frequency conversion of the received waveform (RF (Radio Frequency) signal) of the terminal uplink signal by an orthogonal demodulator or the like.
- RF Radio Frequency
- the received waveform recording unit 222 executes sampling processing on the result of frequency conversion for the received waveform (RF signal) of the terminal uplink signal.
- the receiving unit 221 generates waveform data representing a digital value obtained by sampling processing.
- the terminal station 3 When the terminal station 3 transmits the terminal uplink signal for each sensor data a plurality of times, a plurality of waveform data corresponding to the same terminal uplink signal may be generated.
- the reception waveform recording unit 222 records the reception waveform information including the reception time information of the terminal uplink signal in the antenna 21 and the generated waveform data in the data storage unit 23.
- the data storage unit 23 stores the received waveform information.
- the received waveform recording unit 222 may select, for example, the waveform data having the best reception state from a plurality of waveform data corresponding to the same terminal uplink signal.
- the reception waveform recording unit 222 may record the reception waveform information including the reception time information of the terminal uplink signal and the selected waveform data in the data storage unit 23.
- the received waveform recording unit 222 may record, for example, received waveform information including the average of a plurality of waveform data corresponding to the same terminal uplink signal in the data storage unit 23.
- the communication status measuring unit 223 measures the communication status of the terminal uplink signals transmitted from the plurality of terminal stations 3 in the receiving unit 221. This communication status is arbitrary information that quantitatively represents the degree of congestion of communication. For example, the communication status measuring unit 223 measures the number of terminal uplink signals received per unit time in the receiving unit 221. The communication status measuring unit 223 may measure the received signal strength of the frequency band of the terminal uplink signal in the receiving unit 221. The communication status measurement unit 223 outputs the measurement result of the communication status to the timing control unit 224.
- the timing control unit 224 acquires the measurement result of the communication status from the communication status measurement unit 223.
- the timing control unit 224 generates information on the upper limit value based on the measurement result of the communication status.
- the timing control unit 224 generates a transmission permission signal including information on the upper limit value.
- the timing control unit 224 controls the timing at which the terminal station 3 transmits the terminal uplink signal by using the terminal downlink signal including the transmission permission signal.
- the storage unit 225 stores the transmission timing derived based on the orbit information of the mobile relay station 2. This transmission timing is, for example, the transmission timing of the terminal downlink signal.
- the timing control unit 224 can obtain the position, speed, and moving direction of the mobile relay station 2 (LEO satellite) at any time based on the orbit information of the mobile relay station 2.
- the storage unit 225 may store the terminal identification information of the terminal station 3 and the position information of the terminal station 3 in advance.
- the timing control unit 224 may determine the terminal station 3 (terminal station 3 in coverage) to be notified of the transmission permission signal based on the position of the mobile relay station 2 and the position of the terminal station 3.
- the timing control unit 224 may specify the terminal identification information of the determined terminal station 3.
- the timing control unit 224 may include the specified terminal identification information in the transmission permission signal.
- the transmission unit 226 acquires the terminal downlink signal generated by the timing control unit 224.
- the transmission unit 226 transmits the terminal downlink signal from one or a plurality of antennas 21.
- the terminal downlink signal includes a transmission permission signal and information on the upper limit value.
- the transmission timing of the terminal downlink signal is controlled by the timing control unit 224 based on the orbit information of the mobile relay station 2.
- 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 timing derived based on the orbit information of the mobile relay station 2 (LEO satellite). This transmission timing is, for example, the transmission timing of the base station downlink signal.
- the control unit 242 controls the transmission data modulation unit 243 and the transmission unit 244 so that the received waveform information is transmitted to the base station 4 at the derived transmission timing.
- the transmission data modulation unit 243 reads the received waveform information as transmission data from the data storage unit 23.
- the transmission data modulation unit 243 modulates the read transmission data to generate a base station downlink signal (electrical signal).
- the transmission unit 244 converts the base station downlink signal (electrical signal) into a radio signal.
- the plurality of antennas 25 transmit a base station downlink signal (radio signal) to the base station 4.
- the configuration of the terminal station 3 will be described.
- the terminal station 3 includes a plurality of antennas 31, a receiving unit 32, a transmission control unit 33, a data storage unit 34, and a transmission unit 35.
- the data storage unit 34 stores sensor data and the like.
- the receiving unit 32 receives the terminal downlink signal from the mobile relay station 2 by using one or more antennas 31.
- the transmission control unit 33 extracts a transmission permission signal from the terminal downlink signal received by the reception unit 32.
- the transmission control unit 33 extracts the information of the upper limit value from the transmission permission signal.
- the upper limit is, for example, the value of the contention window.
- the transmission control unit 33 derives the backoff counter value "x" based on the information of the upper limit value extracted from the transmission permission signal.
- the initial value of the backoff counter value "x" is a value of 0 or more.
- the transmission control unit 33 selects the backoff counter value “x” from the random numbers uniformly distributed in the range in which the upper limit value included in the transmission permission signal is the upper limit value.
- the transmission control unit 33 stores the orbit information of the mobile relay station 2 in advance.
- the transmission control unit 33 derives the elevation angle of the mobile relay station 2 as seen from the own terminal station 3 based on the orbit information of the mobile relay station 2. For example, the transmission control unit 33 derives a subtraction value (countdown value) to a larger value as the elevation angle of the mobile relay station 2 seen from the own terminal station 3 is larger.
- the transmission control unit 33 subtracts the subtraction value from the backoff counter value “x” at a predetermined cycle. As a result, the transmission control unit 33 updates the backoff counter value.
- the transmission control unit 33 may acquire the terminal identification information included in the extracted transmission permission signal. When the acquired terminal identification information is the identification information associated with the own terminal station, the transmission control unit 33 may extract the information of the upper limit value from the transmission permission signal. If the acquired terminal identification information is not the identification information associated with the own terminal station, the transmission control unit 33 may suspend the transmission of the terminal uplink signal from the transmission unit 35 to the mobile relay station 2. good.
- the transmission unit 35 When it is determined that the backoff counter value "x" is 0 or less, the transmission unit 35 reads the sensor data as terminal transmission data from the data storage unit 34.
- the transmission unit 35 transmits a terminal uplink signal (wireless signal) including the read terminal transmission data from one or a plurality of antennas 31.
- the transmission unit 35 transmits a signal by LPWA.
- the transmission unit 35 determines the channel and transmission timing used by the own terminal station to transmit the terminal uplink signal by a method predetermined in the wireless communication method to be used. Further, the transmission unit 35 may form a transmission beam of a terminal uplink signal transmitted from one or a plurality of antennas 31 by a predetermined method in the wireless communication method to be used.
- the transmission unit 35 starts transmitting the terminal uplink signal.
- the transmission unit 35 reads the sensor data as terminal transmission data from the data storage unit 34.
- the transmission unit 35 transmits a terminal uplink signal including the read terminal transmission data from the antenna 31.
- the transmission unit 35 executes communication with a predetermined communication station (for example, another terminal station 3) by a wireless method such as time division multiplexing or orthogonal frequency division multiplexing (OFDM). good.
- a predetermined communication station for example, another terminal station 3
- OFDM orthogonal frequency division multiplexing
- the base station 4 includes a plurality of antenna stations 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 using the plurality of antenna stations 41 into an electric signal.
- the base station signal reception processing unit 43 obtains received waveform information including waveform data and reception time information by executing signal processing and decoding processing on the converted electric signal.
- 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 executes reception processing of received waveform information.
- the terminal signal reception processing unit 44 executes a decoding process on the waveform data included in the received waveform information, so that the environment information (sensor data) and the like transmitted from the terminal station 3 using the terminal uplink signal and the like are used. Get the data of.
- the terminal signal reception processing unit 44 includes a distribution unit 441, a signal processing unit 442, and a terminal signal decoding unit 443.
- the distribution unit 441 reads out waveform data at the same reception time from the received waveform information.
- the distribution unit 441 outputs the read waveform data to the signal processing unit 442 according to the antenna identifier associated with the waveform data. That is, the distribution unit 441 outputs each waveform data associated with the antenna identifier of the antenna 21 to the signal processing unit 442.
- the signal processing unit 442 executes processing such as frame detection (terminal uplink signal detection), Doppler shift compensation, and offline beam control for each waveform data.
- the signal processing unit 442 outputs the resulting symbol to the terminal signal decoding unit 443.
- frame detection is a process of detecting a section including a signal (terminal transmission frame) transmitted from a terminal station from waveform data.
- the offline beam control is not the received beam control executed by the mobile relay station 2, but the received beam control executed by the base station 4 as post-processing when the waveform data recorded by the mobile relay station 2 is transmitted to the base station 4. Is.
- the terminal signal decoding unit 443 obtains terminal transmission data by executing a decoding process on the symbol.
- FIG. 3 is a diagram showing an example of the relationship between the position of the mobile relay station 2 with respect to each terminal station 3 and each variable value (each subtraction value) used for subtracting the backoff counter value.
- the mobile relay station 2 is mounted on a low earth orbit satellite moving over the communication target area.
- the mobile relay station 2 irradiates the communication target area on the ground with the transmission permission signal including the information of the upper limit value by using the terminal downlink signal.
- M terminal stations 3 are located in the communication target area.
- the elevation angle of the mobile relay station 2 seen from the terminal station 3-7 is larger than the elevation angle of the mobile relay station 2 seen from the terminal station 3-9.
- the elevation angle of the mobile relay station 2 seen from the terminal station 3-5 is larger than the elevation angle of the mobile relay station 2 seen from the terminal station 3-7.
- the terminal station 3-5 transmits the terminal uplink signal 101-5 to the mobile relay station 2.
- the terminal station 3-7 transmits the terminal uplink signal 101-7 to the mobile relay station 2.
- the terminal station 3-9 transmits the terminal uplink signal 101-9 to the mobile relay station 2.
- the separation of the terminal uplink signal 101 transmitted from each terminal station 3 becomes easier as the elevation angle of the mobile relay station 2 seen from the terminal station 3 is larger. In FIG. 3, it is easier to separate the terminal uplink signal 101-5 and the terminal uplink signal 101-7 than to separate the terminal uplink signal 101-7 and the terminal uplink signal 101-9.
- the transmission control unit 33 increases the transmission probability of the terminal uplink signal 101 as the elevation angle of the mobile relay station 2 seen from the terminal station 3 increases. For this purpose, the transmission control unit 33 sets a subtraction value (countdown value) as a larger value as the elevation angle of the mobile relay station 2 is larger.
- the value described in each terminal station 3 shown in FIG. 3 represents an example of each subtraction value.
- the subtraction value is, for example, a real value in the range of 0 to 1.
- the subtraction value of the terminal station 3-5 is "1.0" as an example.
- the subtraction value of the terminal station 3-7 is “1.0” as an example.
- the subtraction value of the terminal station 3-9 is "0.5” as an example.
- the subtraction value of the terminal station 3-M is "0.2" as an example. Therefore, the transmission probability of the terminal uplink signal 101-M is lower than the transmission probability of the terminal uplink signal 101-9.
- FIG. 4 is a diagram showing an example of a decrease rate of the backoff counter value of each terminal station.
- the rate of decrease of the backoff counter value is different between the terminal stations 3 having different elevation angles of the mobile relay stations 2. For example, even if the terminal station 3 has a large backoff counter value determined by using random numbers, the reduction rate of the backoff counter value is fast when the elevation angle of the mobile relay station 2 as seen from the terminal station 3 is large. Therefore, the transmission probability of the terminal uplink signal 101 is high. That is, the larger the elevation angle of the mobile relay station 2 as seen from the terminal station 3, the higher the transmission probability of the terminal uplink signal 101 in the terminal station 3.
- FIG. 1 the rate of decrease of the backoff counter value of each terminal station.
- the transmission probability of the terminal uplink signal 101 is the highest in the terminal station 3 “# 3” at the position where the elevation angle of the mobile relay station 2 is large. Further, in the terminal station 3 "# 1" at a position where the elevation angle of the mobile relay station 2 is small, the transmission probability of the terminal uplink signal 101 is the lowest.
- FIG. 5 is a flowchart showing a data collection process.
- the sensor acquires sensor data (environmental information) at any time.
- the data storage unit 34 stores the acquired sensor data (step S111).
- the transmission unit 35 acquires the sensor data as terminal transmission data from the data storage unit 34.
- the transmission unit 35 wirelessly transmits a terminal uplink signal including terminal transmission data from the antenna 31 at the transmission timing derived by the transmission control unit 33 (step S112).
- the terminal station 3 repeats the process from step S111.
- the receiving unit 221 receives the terminal uplink signal transmitted from the terminal station 3 (step S121).
- the reception waveform recording unit 222 records the reception waveform information in which the waveform data representing the waveform of the terminal uplink signal and the reception time information 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. 6 is a flowchart showing the control process of downlink transmission.
- the control unit 242 detects that the derived transmission timing and the current time are equal to each other, the control unit 242 instructs the transmission data modulation unit 243 and the transmission unit 244 to transmit the received waveform information (step S211).
- the transmission data modulation unit 243 reads the received waveform information stored in the data storage unit 23 as transmission data.
- the transmission data modulation unit 243 generates a base station downlink signal by modulating the read transmission data.
- the transmission unit 244 transmits a base station downlink signal (radio signal) from the plurality of antennas 25 (step S212).
- the mobile relay station 2 repeats the process from step S211.
- the antenna station 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 station 41 into an electric signal.
- the receiving unit 42 outputs the converted electric signal as a receiving signal to the base station signal receiving processing unit 43.
- the base station signal reception processing unit 43 performs signal processing and decoding processing on the received signal.
- the base station signal reception processing unit 43 outputs the reception waveform information obtained by the signal processing and the decoding processing to the terminal signal reception processing unit 44 (step S222).
- the terminal signal reception processing unit 44 executes reception processing of the terminal uplink signal indicated by the received waveform information.
- the terminal signal reception processing unit 44 obtains sensor data (environmental information) transmitted from the terminal station 3 by executing decoding processing on the waveform data included in the received waveform information (step S223).
- the base station 4 repeats the process from step S221.
- FIG. 7 is a flowchart showing a control example of the transmission timing of the terminal uplink signal.
- Step S328 shown in FIG. 7 corresponds to S112 shown in FIG.
- Step S333 shown in FIG. 7 corresponds to S122 shown in FIG.
- the communication status measuring unit 223 measures the communication status of the terminal uplink signal in the receiving unit 221 (step S311).
- the timing control unit 224 generates information on the upper limit value (for example, the value of the contention window) based on the communication status measured by the communication status measurement unit 223 (step S312).
- the timing control unit 224 generates a transmission permission signal including information on the upper limit value.
- the timing control unit 224 may generate a transmission permission signal including the terminal identification information of the terminal station 3 to be notified of the transmission permission signal and the information of the upper limit value.
- the transmission unit 226 acquires a transmission permission signal from the timing control unit 224.
- the transmission unit 226 transmits a terminal downlink signal including a transmission permission signal from the plurality of antennas 21 (step S313).
- the mobile relay station 2 repeats the process from step S311.
- the receiving unit 32 receives the terminal downlink signal including the transmission permission signal from the mobile relay station 2 by the antenna 31 (step S321).
- the transmission control unit 33 derives the backoff counter value “x” based on the upper limit value included in the transmission permission signal (step S322).
- the transmission control unit 33 derives a subtraction value (countdown value) to a larger value as the elevation angle of the mobile relay station 2 seen from the own terminal station 3 is larger (step S324).
- the transmission control unit 33 subtracts the subtraction value “CD” from the backoff counter value “x”.
- the transmission control unit 33 determines whether or not the backoff counter value “x” is 0 or less.
- the transmission control unit 33 may determine whether or not the backoff counter value is 0 (step S326).
- the transmission control unit 33 updates the time variable value "t" to "t + 1" (step S327).
- the terminal station 3 returns the process to step S325.
- step S326 When it is determined that the backoff counter value "x" is 0 or less (step S326: Yes), the transmission unit 35 reads the sensor data as terminal transmission data from the data storage unit 34. The transmission unit 35 transmits a terminal uplink signal including the read terminal transmission data from the antenna 31 (step S328). The terminal station 3 repeats the process from step S321.
- the transmission control unit 33 may return the process from step S326 to step S321 at a predetermined cycle. In this case, the backoff counter value may not be updated in step S322 following step S321.
- the receiving unit 221 of the mobile relay station 2 receives the terminal uplink signal transmitted from the terminal station 3 a plurality of times by the antenna 21 (step S331).
- the reception waveform recording unit 222 samples the reception waveforms of the plurality of terminal uplink signals received by the reception unit 221.
- the received waveform recording unit 222 generates waveform data indicating the values obtained by sampling.
- the received waveform recording unit 222 selects, for example, the waveform data having the best reception state from a plurality of waveform data corresponding to the same terminal uplink signal (step S332).
- the reception waveform recording unit 222 records the reception waveform information including the reception time information of the terminal uplink signal in the antenna 21 and the selected waveform data in the data storage unit 23 (step S333).
- the mobile relay station 2 repeats the process from step S331.
- the transmission control unit 33 determines the earlier transmission timing as the elevation angle of the relay device as seen from the own wireless communication device is larger. For example, when the elevation angle of the mobile relay station 2 as seen from the terminal station 3 is large, the rate of decrease of the backoff counter value is high, so that the transmission probability of the terminal uplink signal 101 is high.
- the transmission unit 35 transmits the terminal uplink signal to the mobile relay station 2 (relay device) at the transmission timing.
- a MAC (Media Access Control) protocol that reduces the transmission probability of a terminal uplink signal is feasible when the elevation angle of the mobile relay station 2 as seen from the terminal station 3 is small.
- the mobile relay station 2 transmits the transmission permission signal and the information of the upper limit value to the terminal station 3 by using the terminal downlink signal.
- the transmission permission signal and the information of the upper limit value are transmitted to the terminal station 3 from other than the mobile relay station 2. That is, the transmission permission signal and the information of the upper limit value may be transmitted to the terminal station 3 by using a wireless signal or a wired signal other than the terminal downlink signal.
- a surrounding ground station may transmit a transmission permission signal and information on an upper limit value to a predetermined terminal station 3 by a wireless signal.
- the transmission control unit 33 of the terminal station 3 does not have to store the orbit information of the mobile relay station 2 in advance.
- the timing control unit 224 of the mobile relay station 2 receives information on the current position of the mobile relay station 2, information on the position advanced by the width (distance) of the communication target area in the moving direction from the current position, information on the time, and information on the time.
- the transmission permission signal and the upper limit value are transmitted by the terminal downlink signal.
- the transmission control unit 33 of the terminal station 3 is based on the current position of the mobile relay station 2, the information of the position advanced by the width (distance) of the communication target area in the moving direction from the current position, and the time information.
- the elevation angle of the mobile relay station 2 as seen from the own terminal station may be derived for each time.
- the transmission control unit 33 derives a subtraction value (countdown value) to a larger value as the elevation angle of the mobile relay station 2 seen from the own terminal station 3 is larger.
- the timing control unit 224 uses the two-line orbital elements (Two Line Elements: TLE) of the mobile relay station 2 as a terminal downlink signal instead of transmitting information on the position advanced by the width of the communication target area and information on the time. May be transmitted to the terminal station 3.
- the transmission control unit 33 of the terminal station 3 may derive the elevation angle of the mobile relay station 2 as seen from the own terminal station for each time based on the two-line orbital element of the mobile relay station 2.
- the transmission control unit 33 derives a subtraction value to a larger value as the elevation angle of the mobile relay station 2 seen from the own terminal station 3 is larger.
- FIG. 8 is a diagram showing a configuration example of the wireless communication system 1a in the third modification of the embodiment.
- the base station has a frequency conversion unit instead of the mobile relay station having a frequency conversion unit.
- 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 a plurality of antennas 21 (array antennas), a terminal communication unit 22a, a data storage unit 23, a base station communication unit 24, and a plurality of antennas 25 (array antennas).
- the terminal communication unit 22a includes a plurality of reception units 221, a plurality of reception waveform recording units 222, a communication status measurement unit 223, a timing control unit 224, a storage unit 225, and a transmission unit 226.
- the received waveform recording unit 222 executes sampling processing on the received waveform (RF signal) of the terminal uplink signal.
- the base station 4a includes a plurality of antenna stations 41, a receiving unit 42, a base station signal receiving processing unit 43, and a terminal signal receiving processing unit 44.
- the terminal signal reception processing unit 44 includes a distribution unit 441, a signal processing unit 442, a terminal signal decoding unit 443, and a plurality of frequency conversion units 444.
- the distribution unit 441 reads out the waveform data at the same reception time from the received waveform information.
- the distribution unit 441 outputs the read waveform data to the signal processing unit 442 according to the antenna identifier associated with the waveform data. That is, the distribution unit 441 outputs the waveform data associated with the antenna identifier of the antenna 21 to the plurality of frequency conversion units 444.
- the frequency conversion unit 444 executes frequency conversion using an orthogonal demodulator or the like for the waveform data (RF signal) of the terminal uplink signal.
- the frequency conversion unit 444 outputs the result of frequency conversion for the waveform data to the signal processing unit 442.
- the signal processing unit 442 executes processing such as frame detection (detection of terminal uplink signal), Doppler shift compensation, and offline beam control for the result of frequency conversion for waveform data.
- the signal processing unit 442 outputs a symbol obtained as a result of processing such as frame detection, Doppler shift compensation, and offline beam control to the terminal signal decoding unit 443.
- the mobile body on which the mobile relay station is mounted is a low earth orbit satellite (LEO satellite) has been described, but other than geostationary satellites, drones, HAPS, etc. It may be a flying object.
- LEO satellite low earth orbit satellite
- the base station and the mobile relay station communicate with each other by MIMO, but the present invention is not limited to this, and at least one of the base station and the mobile relay station uses one antenna. It may be one that communicates.
- the wireless communication device is the terminal station 3 in the embodiment
- the relay device is the mobile relay station 2 in the embodiment
- the base station device is the base station in the embodiment. It is 4.
- FIG. 9 is a diagram showing an example of the hardware configuration of the mobile relay station 2.
- a part or all of each functional unit of the mobile relay station 2 is stored in a memory 202 in which a processor 200 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 201.
- each functional unit of the mobile relay station 2 is, for example, an electronic circuit 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 electronic circuit or circuitry).
- Communication status measurement unit 224 ... Timing control unit, 225 ... Storage unit, 226 ... Transmission unit, 227 ... Frequency conversion unit, 241 ... Storage unit, 242 ... Control unit, 243 ... Transmission data modulation unit, 244 ... Transmission unit, 41 ... Antenna station, 42 ... Reception Unit, 43 ... Base station signal reception processing unit, 44 ... Terminal signal reception processing unit, 441 ... Distribution unit, 442 ... Signal processing unit, 443 ... Terminal signal decoding unit, 444 ... Frequency conversion unit
Abstract
Description
図1は、実施形態における、無線通信システム1の構成例を示す図である。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において、移動中継局2、端末局3及び基地局4のそれぞれの台数は、任意である。ここで、端末局3の台数は多数であることが想定される。
図2は、実施形態における、無線通信システム1の構成例を示す図である。移動中継局2は、複数のアンテナ21(アレーアンテナ)と、端末通信部22と、データ記憶部23と、基地局通信部24と、複数のアンテナ25(アレーアンテナ)とを備える。
端末通信部22は、複数の受信部221と、複数の受信波形記録部222と、通信状況測定部223と、タイミング制御部224と、記憶部225と、送信部226と、複数の周波数変換部227とを備える。
端末局3は、複数のアンテナ31と、受信部32と、送信制御部33とデータ記憶部34と、送信部35とを備える。データ記憶部34は、センサデータなどを記憶する。
基地局4は、複数のアンテナ局41と、受信部42と、基地局信号受信処理部43と、端末信号受信処理部44とを備える。
図3は、各端末局3に対する移動中継局2の位置と、バックオフカウンタ値の減算に使用される各変数値(各減算値)との関係例を示す図である。図3では、通信対象エリアの上空を移動中の低軌道衛星に、移動中継局2が搭載されている。移動中継局2は、上限値の情報を含む送信許可信号を、端末ダウンリンク信号を用いて、地上の通信対象エリアに照射する。
図5は、データ収集処理を示すフローチャートである。端末局3において、センサはセンサデータ(環境情報)を随時取得する。データ記憶部34は、取得されたセンサデータを記憶する(ステップS111)。
上記の実施形態では、移動中継局2が、送信許可信号と上限値の情報とを、端末ダウンリンク信号を用いて端末局3に送信している。第1変形例では、送信許可信号と上限値の情報とは、移動中継局2以外から、端末局3に送信される。すなわち、送信許可信号と上限値の情報とは、端末ダウンリンク信号以外の無線信号又は有線信号を用いて、端末局3に送信されてもよい。
端末局3の送信制御部33は、移動中継局2の軌道情報を、予め記憶していなくてもよい。例えば、移動中継局2のタイミング制御部224は、移動中継局2の現在位置と、その現在位置から移動方向に通信対象エリアの幅(距離)だけ進んだ位置の情報と、時刻の情報と、送信許可信号と、上限値とを、端末ダウンリンク信号で送信する。
図8は、実施形態の第3変形例における、無線通信システム1aの構成例を示す図である。第3変形例では、移動中継局が周波数変換部を備える代わりに、基地局が周波数変換部を備える。
Claims (7)
- 自無線通信装置から見た中継装置の仰角が大きいほど早い送信タイミングを定める送信制御部と、
前記送信タイミングにおいて無線信号を前記中継装置に送信する送信部と
を備える無線通信装置。 - 上限値を取得する受信部を備え、
前記送信制御部は、減算に用いられる変数値である減算値を前記仰角が大きいほど大きい値に導出し、前記上限値に基づいて導出された0以上のバックオフカウンタ値から前記減算値を減算し、前記バックオフカウンタ値が0以下となったタイミングを前記送信タイミングと定める、
請求項1に記載の無線通信装置。 - 前記上限値は、所定期間において複数の通信対象エリアの上空を前記中継装置が通過する時間の長さで、前記複数の通信対象エリアにおける無線通信装置の総数が除算された結果の値である、
請求項2に記載の無線通信装置。 - 前記上限値は、通信対象エリアの上空を前記中継装置が通過する時間の長さで、前記通信対象エリアにおける無線通信装置の総数が除算された結果の値である、
請求項2に記載の無線通信装置。 - 前記上限値は、前記通信対象エリアにおける所定範囲に一様分布する各無線通信装置から前記中継装置に同時に到来した複数の無線信号のうちで分離可能である前記無線信号の数と、前記除算された結果の値とが乗算された結果の値である、
請求項3又は請求項4に記載の無線通信装置。 - 前記上限値は、前記無線信号に対する干渉量に応じて補正された値である、
請求項5に記載の無線通信装置。 - 無線通信装置が実行する無線通信方法であって、
自無線通信装置から見た中継装置の仰角が大きいほど早い送信タイミングを定める送信制御ステップと、
前記送信タイミングにおいて無線信号を前記中継装置に送信する送信ステップと
を含む無線通信方法。
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Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS55107356A (en) * | 1979-02-09 | 1980-08-18 | Mitsubishi Electric Corp | Synchronizing control system |
JPH10509851A (ja) * | 1994-11-18 | 1998-09-22 | インターナショナル モービル サテライト オーガニゼイション | ローカル及びグローバルネットワークを備えた移動衛星通信システム |
WO2018016471A1 (ja) * | 2016-07-19 | 2018-01-25 | 三菱電機株式会社 | 人工衛星の自律運用計画システムおよび人工衛星の運用計画装置 |
WO2020065469A1 (en) * | 2018-09-27 | 2020-04-02 | Telefonaktiebolaget Lm Ericsson (Publ) | Systems and methods for timing adaptation for satellite communications |
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Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
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JPS55107356A (en) * | 1979-02-09 | 1980-08-18 | Mitsubishi Electric Corp | Synchronizing control system |
JPH10509851A (ja) * | 1994-11-18 | 1998-09-22 | インターナショナル モービル サテライト オーガニゼイション | ローカル及びグローバルネットワークを備えた移動衛星通信システム |
WO2018016471A1 (ja) * | 2016-07-19 | 2018-01-25 | 三菱電機株式会社 | 人工衛星の自律運用計画システムおよび人工衛星の運用計画装置 |
WO2020065469A1 (en) * | 2018-09-27 | 2020-04-02 | Telefonaktiebolaget Lm Ericsson (Publ) | Systems and methods for timing adaptation for satellite communications |
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