Wireless communication system, communication device, communication control device, wireless communication method, and communication control method

Abstract

This wireless communication system has a transmission device and a mobile communication device. The wireless communication system furthermore comprises a statistics calculation unit, an information generation unit, and a notification unit. The statistics calculation unit acquires a transmission condition that is transmitted from a transmission device in an area and used in the first wireless signal normally received by a reception unit of the communication device, and generates the statistics information pertaining to the acquired transmission condition. The information generation unit extracts, on the basis of the statistics information, a transmission condition with which the probability of a wireless signal being normally received is high, and generates transmission control information indicating the extracted transmission condition. The notification unit notifies the transmission device in the area of the transmission control information. A transmission control unit of the transmission device determines a transmission condition of wireless signals on the basis of the transmission control information and transmits a second wireless signal under the determined transmission condition from a wireless transmission unit for transmitting wireless signals to the communication device.

Description

Technical Field

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

Background Art

[0002] With the development of IoT (Internet of Things) technology, it has been considered to install IoT terminals equipped with various sensors in various places. The IoT terminal may be installed in a place where it is difficult to install a base station, such as an offshore buoy, a ship, or a mountainous area. Therefore, it has been considered that a communication device mounted on a low-earth orbit satellite receives data collected by IoT terminals installed in various places and relays the received data to a base station installed on the ground.

[0003] It is assumed that a large number of IoT terminals will be installed on the ground. Conventionally, in order to avoid collisions of multi-terminal access by the LPWA (Low Power Wide Area) method, autonomous distributed transmission control for controlling the communication timing of terminals using a phase oscillator model has been performed (see, for example, Non-Patent Document 1). As a result, wireless signals can be normally received from each of a large number of terminals.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventionally, by avoiding collisions between IoT terminals, the communication success rate, which is the ratio at which wireless signals are normally received, has been improved. However, the conditions for a wireless signal transmitted from an IoT terminal to be normally received vary depending on the communication environment.

[0006] In view of the above circumstances, an object of the present invention is to provide a wireless communication system, a communication device, a communication control device, a wireless communication method, and a communication control method that can improve the communication success rate of wireless signals transmitted from terminals in different communication environments to a moving communication device.

Means for Solving the Problem

[0007] One aspect of the present invention is a wireless communication system having a transmission device and a moving communication device, wherein the transmission device includes a wireless transmission unit that transmits a wireless signal to the communication device, and a transmission control unit that determines transmission conditions of the wireless signal and controls the wireless transmission unit to transmit a first wireless signal according to the determined transmission conditions. The communication device includes a reception unit that receives the first wireless signal transmitted from the transmission device. The wireless communication system includes a statistical calculation unit that acquires the transmission conditions used for the first wireless signal transmitted from the transmission device within the area and normally received by the reception unit, and generates statistical information of the acquired transmission conditions; an information generation unit that extracts transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions; and a notification unit that notifies the transmission device within the area of the transmission control information generated by the information generation unit. The transmission control unit determines the transmission conditions of the wireless signal based on the transmission control information, and controls the wireless transmission unit to transmit a second wireless signal according to the determined transmission conditions.

[0008] One aspect of the present invention is a communication device including a receiving unit that receives a wireless signal, a statistical calculation unit that obtains transmission conditions used for transmitting the wireless signal transmitted from a transmission device in an area and normally received by the receiving unit, and generates statistical information of the obtained transmission conditions, an information generation unit that extracts transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions, and a notification unit that notifies the transmission control information generated by the information generation unit to the transmission devices in the area.

[0009] One aspect of the present invention is a communication control device including a statistical calculation unit that obtains transmission conditions used for transmitting a wireless signal transmitted from a transmission device in an area and normally received by a communication device, and generates statistical information of the obtained transmission conditions, an information generation unit that extracts transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions, and a notification unit that notifies the transmission control information generated by the information generation unit to the transmission devices in the area.

[0010] One aspect of the present invention is a wireless communication method executed by a wireless communication system having a transmitting device and a moving communication device, the wireless transmission unit of the transmitting device including a wireless transmission step of transmitting a wireless signal to the communication device, the transmission control unit of the transmitting device determining transmission conditions of the wireless signal and controlling the wireless transmission unit to transmit a first wireless signal according to the determined transmission conditions, the receiving unit of the communication device including a receiving step of receiving the first wireless signal transmitted from the transmitting device, the wireless communication system including a statistical calculation step of obtaining transmission conditions used for the first wireless signal transmitted from the transmitting device within the area and normally received in the receiving step and generating statistical information of the obtained transmission conditions, the wireless communication system including an information generation step of extracting transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information and generating transmission control information indicating the extracted transmission conditions, the wireless communication system including a notification step of notifying the generated transmission control information to the transmitting device within the area, and the transmission control unit determining transmission conditions of the wireless signal based on the transmission control information and controlling the wireless transmission unit to transmit a second wireless signal according to the determined transmission conditions.

[0011] One aspect of the present invention is a wireless communication method including a receiving step of receiving a wireless signal, a statistical calculation step of obtaining transmission conditions used for transmission of the wireless signal transmitted from a transmitting device within the area and normally received in the receiving step and generating statistical information of the obtained transmission conditions, an information generation step of extracting transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information and generating transmission control information indicating the extracted transmission conditions, and a notification step of notifying the generated transmission control information to the transmitting device within the area.

[0012] One aspect of the present invention includes a statistical calculation step of obtaining transmission conditions used for transmitting a radio signal transmitted from a transmission device within an area and normally received by a communication device, and generating statistical information on the obtained transmission conditions; an information generation step of extracting transmission conditions with a high probability of normally receiving a radio signal based on the statistical information, and generating transmission control information indicating the extracted transmission conditions; and a notification step of notifying the generated transmission control information to the transmission device within the area.

Advantages of the Invention

[0013] According to the present invention, it is possible to improve the communication success rate of radio signals transmitted from terminals in different communication environments to a moving communication device.

Brief Description of the Drawings

[0014]

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Figure 10

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each of the embodiments described below, the same components as those in other embodiments may be denoted by the same reference numerals, and redundant descriptions may be omitted.

[0016] (First Embodiment) FIG. 1 is a diagram for explaining the outline of a wireless communication system 1 according to the first embodiment of the present invention. The wireless communication system 1 includes a terminal station 2, a mobile relay station 3, and a base station 4. The number of each of the terminal station 2, the mobile relay 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 2 is large.

[0017] The mobile relay station 3 is an example of a communication device mounted on a moving body and having a communicable area that moves over time. The mobile relay station 3 of the present embodiment is provided on a LEO (Low Earth Orbit) satellite. The altitude of the LEO satellite is 2000 km or less, and it orbits around the earth's upper atmosphere in about 1.5 hours. The terminal station 2 and the base station 4 are installed on the earth such as on the ground or at sea. The terminal station 2 is, for example, an IoT terminal. The wireless signal from the terminal station 2 to the mobile relay station 3 is referred to as a terminal uplink signal, and the wireless signal from the mobile relay station 3 to the terminal station 2 is referred to as a terminal downlink signal. Also, the wireless signal from the mobile relay station 3 to the base station 4 is referred to as a base station downlink signal, and the wireless signal from the base station 4 to the mobile relay station 3 is referred to as a base station uplink signal.

[0018] Since the mobile relay station 3 mounted on the LEO satellite communicates while moving at high speed, the time during which each terminal station 2 and base station 4 can communicate with the mobile relay station 3 is limited. Specifically, when viewed from the ground, the mobile relay station 3 passes over the sky in about a few minutes. The communication destination area A of the mobile relay station 3 changes as the mobile relay station 3 moves. The terminal station 2 collects and stores data such as sensor data detected by the sensor. The terminal station 2 transmits a terminal uplink signal in which the collected data is set at a timing when communication with the mobile relay station 3 is possible. The mobile relay station 3 accumulates the data received from each terminal station 2 by the terminal uplink signal, and wirelessly transmits the accumulated data by a base station downlink signal at a timing when communication with the base station 4 is possible. The base station 4 acquires the data collected by the terminal station 2 from the received base station downlink signal.

[0019] The mobile relay station 3 has an antenna used for wireless communication with the terminal station 2 and an antenna used for wireless communication with the base station 4. Therefore, the mobile relay station 3 can also perform wireless communication with the terminal station 2 and wireless communication with the base station 4 in parallel.

[0020] As the mobile relay station, it is conceivable to use a relay station mounted on a geostationary satellite, a drone, an unmanned aircraft such as a HAPS (High Altitude Platform Station), etc. However, in the case of a relay station mounted on a geostationary satellite, although the ground coverage area (footprint) is large, due to its high altitude, the link budget for IoT terminals installed on the ground is very small. On the other hand, in the case of a relay station mounted on a drone or HAPS, although the link budget is high, the coverage area is narrow. Furthermore, a drone requires a battery and a HAPS requires a solar panel. In this embodiment, the mobile relay station 3 is mounted on a LEO satellite. Therefore, in addition to the link budget being within limits, since the LEO satellite orbits outside the atmosphere, there is no air resistance and fuel consumption is also low. Also, the footprint is larger compared to the case of mounting a relay station on a drone or HAPS.

[0021] On the other hand, the transmission success conditions for the terminal uplink signal from the terminal station 2 to the mobile relay station 3 vary depending on the communication environment. The communication environment includes, for example, the number of surrounding terminal stations 2, the number of interfering terminals, and obstacles such as buildings and mountains. Depending on the communication environment, the antenna elevation angle with a high communication success rate for the terminal uplink signal, the number of transmissions of the same signal, the signal transmission timing, etc. are different. For example, when the antenna elevation angle of the terminal station 2 is directed towards the direction of the obstacle, the communication success rate decreases. Also, for example, in eMTC (enhanced Machine Type Communication) / NB-IoT (Narrow Band Internet of Things), which are LTE (Long Term Evolution) services for IoT, there is a Repetition function to expand coverage by repeatedly transmitting the same signal (see, for example, Reference 1). In Sigfox, which is one of the LPWA services, the same message is always transmitted continuously three times from the terminal (see, for example, Reference 2). When the number of transmissions of the same signal increases, the communication success rate once improves, but if the number of transmissions of the same signal is too large, the communication success rate decreases due to interference. And the communication success rate is high during time periods with less interference and low during time periods with more interference.

[0022] (Reference 1) "Trends in Wireless Systems for LPWA", Ministry of Internal Affairs and Communications, [online], 2018, Internet <URL:https: / / www.soumu.go.jp / main_content / 000543715.pdf>

[0023] (Reference 2) "Introduction to the SIGFOX Network", Ministry of Internal Affairs and Communications, Working Group Materials of the Information and Communication Council, [online], 2016, Internet <URL:https: / / www.soumu.go.jp / main_content / 000450876.pdf>

[0024] Therefore, the mobile relay station 3 creates a distribution of the number of successful communications or the communication success rate for the conditions under which the transmission from the terminal station 2 is successful, for each category based on the location information of the terminal station 2 and the signal transmission timing of the terminal station 2. That the transmission from the terminal station 2 is successful may mean that the mobile relay station 3 can successfully demodulate and decode the terminal uplink signal received from the terminal station 2. Alternatively, the mobile relay station 3 may determine the success of the transmission in the reception processing of the upper layer than the physical layer. For example, the mobile relay station 3 may determine that the transmission is successful when no error is detected in the error detection process using the error correction code in the data link layer, or may determine that the transmission is successful when no error is detected by the error detection function in the transport layer. The transmission conditions of the terminal uplink signal when the transmission from the terminal station 2 is successful are described as the transmission success conditions.

[0025] The finer the granularity of the distribution, the more favorable conditions based on local categories such as areas and time zones can be found. Especially when there are obstacles, the area where the elevation angle with a high communication success rate is common is local. The mobile relay station 3 generates map information indicating the number of successful communications or the communication success rate of each transmission success condition, for each category represented by, for example, an area, a time zone, or a combination of an area and a time zone.

[0026] The mobile relay station 3 obtains a transmission condition with a high number of successful communications or a high communication success rate under the constraint conditions represented by the section, based on the map information generated for each section. The mobile relay station 3 notifies the terminal station 2 of transmission control information indicating the transmission conditions obtained for each section. Note that the map information may be used as the transmission control information as it is. When area information is used in the section, the mobile relay station 3 distributes the transmission control information to the terminal stations 2 within that area. The mobile relay station 3 or the base station 4 may distribute the transmission control information to the terminal station 2 at a predetermined schedule such as periodically, or a manual update command for the transmission control information may be input to the terminal station 2, the mobile relay station 3, or the base station 4 periodically. In this way, the transmission control information is updated automatically or manually. Further, the mobile relay station 3 may transmit the generated map information to the base station 4, and the base station 4 may generate transmission control information based on the map information. The base station 4 notifies the terminal station 2 of the generated transmission control information. The terminal station 2 that is the transmission destination of the transmission control information may be all terminal stations 2 or terminal stations 2 with a high priority. The terminal station 2 determines the transmission conditions based on the transmission control information, and transmits a terminal uplink signal according to the determined transmission conditions.

[0027] FIG. 2 is a configuration diagram of the wireless communication system 1. In FIG. 2, only the functional blocks related to the present embodiment are extracted and shown.

[0028] The terminal station 2 includes one or a plurality of antennas 21, a position detection unit 22, a data storage unit 23, a transmission unit 24, a reception unit 25, a control information storage unit 26, a transmission control unit 27, and a communication unit 28.

[0029] The position detection unit 22 acquires position information indicating the position of its own station. For example, the position detection unit 22 detects the position of its own station by a Global Positioning System (GPS). The position detection unit 22 outputs the acquired position information to the transmission control unit 27. The data storage unit 23 stores sensor data and the like.

[0030] The transmission unit 24 transmits the terminal uplink signal, for example, by LPWA (Low Power Wide Area). The transmission unit 24 reads sensor data from the data storage unit 23 as terminal transmission data. The transmission unit 24 generates a terminal uplink signal with the set terminal transmission data. The transmission unit 24 transmits the terminal uplink signal from the antenna 21 according to the transmission conditions determined by the transmission control unit 27.

[0031] The reception unit 25 performs reception processing of the terminal downlink signal received by the antenna 21. The reception unit 25 writes the transmission control information obtained from the terminal downlink signal through the reception processing into the control information storage unit 26. The control information storage unit 26 stores various data including the transmission control information.

[0032] The transmission control unit 27 determines the transmission conditions of the terminal uplink signal. The transmission conditions include the number of transmissions of the same signal, the transmission number, the transmission interval, the transmission timing, etc. The number of transmissions of the same signal N indicates that the same terminal uplink signal is transmitted a total of N times, and the transmission number n indicates the nth transmission among the number of transmissions of the same signal N. The transmission control unit 27 controls the transmission unit 24 to transmit the terminal uplink signal according to the determined transmission conditions.

[0033] The transmission control unit 27 sets the terminal ID, location information, transmission condition notification information, environmental information, etc. of its own station in the terminal uplink signal transmitted by the transmission unit 24. The terminal ID is terminal identification information for identifying the terminal station 2. The transmission condition notification information indicates the transmission conditions used for transmitting the terminal uplink signal. The environmental information is information about the surrounding environment of the terminal station 2. The environmental information is, for example, weather, noise floor, etc. After receiving the transmission control information, the transmission control unit 27 determines the transmission conditions based on the transmission control information stored in the control information storage unit 26.

[0034] The communication unit 28 communicates with the base station 4 via the network. The network is, for example, a terrestrial communication network.

[0035] The mobile relay station 3 includes one or more antennas 31, a terminal communication unit 32, a data storage unit 33, a data transmission control unit 34, a base station communication unit 35, one or more antennas 36, and an analysis unit 37.

[0036] The terminal communication unit 32 wirelessly communicates with the terminal station 2. The terminal communication unit 32 includes a terminal signal receiving unit 321, a terminal signal demodulating unit 322, a terminal signal modulating unit 323, and a terminal signal transmitting unit 324.

[0037] The terminal signal receiving unit 321 receives, via the antenna 31, the terminal uplink signals transmitted by each terminal station 2. The terminal signal demodulating unit 322 demodulates and decodes the terminal uplink signals received by the terminal signal receiving unit 321, and obtains the terminal ID, location information, transmission condition notification information, environment information, and terminal transmission data transmitted by the terminal station 2. The terminal signal demodulating unit 322 writes the received signal information, which is obtained from these pieces of information and the reception time of the terminal uplink signal and is set with respect to the normally demodulated and decoded terminal uplink signal, into the data storage unit 33.

[0038] The terminal signal modulating unit 323 encodes and modulates the data to be transmitted to the terminal station 2 to generate a terminal downlink signal. The terminal signal transmitting unit 324 transmits, from the antenna 31, the terminal downlink signal generated by the terminal signal modulating unit 323.

[0039] The data storage unit 33 stores the received signal information. The received signal information is information associating the reception time of the terminal uplink signal with the terminal ID, location information, transmission condition notification information, environment information, and terminal transmission data obtained from the terminal uplink signal. When the transmission time is included in the transmission condition notification information, the received signal information may not include the reception time. Further, the received signal information may further include information on the transmission conditions obtained based on the reception time of the terminal uplink signal or the information set in the terminal uplink signal.

[0040] When the mobile relay station 3 becomes communicable with the base station 4, the data transmission control unit 34 outputs transmission data to the base station 4 to the base station communication unit 35. For example, the data transmission control unit 34 reads out the terminal ID, reception time, and terminal transmission data from the reception signal information, and outputs them to the base station communication unit 35 as transmission data to the base station 4.

[0041] The base station communication unit 35 performs encoding and modulation on the transmission data to generate a base station downlink signal, and transmits the generated base station downlink signal from the antenna 36. Also, the base station communication unit 35 receives the base station uplink signal transmitted from the base station 4 by the antenna 36, and performs demodulation and decoding of the received base station uplink signal to obtain the data transmitted by the base station 4.

[0042] The analysis unit 37 includes a statistical calculation unit 371, a storage unit 372, an information generation unit 373, and a notification unit 374. The statistical calculation unit 371 analyzes the reception signal information stored in the data storage unit 33 to generate map information for each category. The statistical calculation unit 371 associates the category information representing the category with the map information generated for that category, and writes it to the storage unit 372. The category information is represented by the value or range of values of one or more classification items. The map information indicates the number of communication successes or the communication success rate for each transmission success condition. The transmission success condition is represented by the value or range of values of one or more analysis items. Information of types that can be obtained from the reception signal information is used for the classification items and the analysis items. The storage unit 372 stores data including map information for each category information and transmission control information for each category information.

[0043] Based on the map information associated with the category information, the information generation unit 373 obtains transmission conditions under which transmission is likely to succeed under the constraint conditions indicated by the category information. The transmission conditions are represented by the value or range of values of one or more analysis items. The information generation unit 373 associates the category information with transmission control information indicating transmission conditions under which transmission is likely to succeed, and writes it to the storage unit 372. Note that the transmission control information may be map information extracted for the range of transmission conditions under which transmission is likely to succeed, or may be the map information as it is.

[0044] The notification unit 374 transmits all of the transmission control information read from the storage unit 372 or transmits it to all or high-priority terminal stations 2. When the classification information associated with the transmission control information includes area information, the notification unit 374 transmits the transmission control information to all or high-priority terminal stations 2 located within that area. For example, the notification unit 374 transmits the transmission control information by means of a terminal downlink signal. Alternatively, the notification unit 374 may transmit the transmission control information to the terminal station 2 via the base station 4. In this case, the notification unit 374 transmits the transmission control information by means of a base station downlink signal from the base station communication unit 35.

[0045] The base station 4 includes one or more antenna stations 41, a base station signal reception processing unit 42, a base station signal transmission processing unit 43, a notification unit 44, and a communication unit 45.

[0046] The antenna station 41 converts the base station downlink signal received from the mobile relay station 3 into an electrical signal and outputs it to the base station signal reception processing unit 42. The base station signal reception processing unit 42 demodulates and decodes the base station downlink signal input from the antenna station 41 to obtain transmission data. The base station signal transmission processing unit 43 encodes and modulates the transmission data to the mobile relay station 3 to generate a base station uplink signal, and transmits the generated base station uplink signal from the antenna station 41.

[0047] When the notification unit 44 receives transmission control information from the mobile relay station 3, it transmits the transmission control information to the terminal station 2. When the classification information associated with the transmission control information includes area information, the notification unit 44 transmits the transmission control information to the terminal station 2 located within that area. When the received transmission control information is map information, the notification unit 44 may obtain conditions that are likely to result in successful transmission from the map information and transmit the transmission control information set with the obtained conditions to the terminal station 2. The communication unit 45 communicates with the terminal station 2 via the network.

[0048] FIG. 3 is a diagram showing an example of received signal information. The received signal information includes the reception time of the terminal uplink signal at the mobile relay station 3, the terminal ID, location information, transmission condition notification information, environment information, sensor data obtained from the terminal uplink signal, and additional acquisition information. The transmission condition notification information indicates the transmission conditions used for the terminal uplink. The transmission condition notification information includes the values of the transmission time, channel, number of channels, number of transmissions of the same signal, transmission number, and transmission interval respectively. The environment information includes the weather and the value of the noise floor. Since the reception time of the terminal uplink signal at the mobile relay station 3 and the transmission time included in the transmission condition notification information are approximately the same, the received signal information may include either of these.

[0049] The additional acquisition information is information obtained by the mobile relay station 3 based on one or both of the reception time and the data included in the terminal uplink signal. The additional acquisition information includes, for example, elevation angle information. Usually, the orbit of the LEO satellite carrying the mobile relay station 3 is predetermined. Therefore, using the orbit information of the LEO satellite, it is possible to calculate the position information of the mobile relay station 3 at the timing when the terminal station 2 transmits the terminal uplink signal. The orbit information is information that can acquire the position of the LEO satellite at each time. On the other hand, the position of the terminal station 2 does not change significantly. Therefore, based on the position of the mobile relay station 3 at the transmission time or reception time and the position of the terminal station 2, it is possible to calculate the elevation angle from the terminal station 2 to the mobile relay station 3.

[0050] Note that the signal reception information may include some of the information shown in FIG. 3. Also, for the transmission condition notification information, environment information, and additional acquisition information, other information may be used as long as it can be used for determining the transmission conditions.

[0051] FIG. 4 is a diagram showing an example of map information. The map information is associated with classification information. The classification information shown in FIG. 4 includes a value range of an area and a value range of a time zone. Further, the map information shown in FIG. 4 shows the number of successful communications for each value range of the elevation angle and the number of successful communications for each value of the same signal transmission number. Note that the map information may be information indicating the number of successful communications for each combination of the value range of the elevation angle and the value of the same signal transmission number. As described above, the number of successful communications for each value or value range of the analysis item may be set in the map information, or the number of successful communications for each combination of values or value ranges of a plurality of analysis items may be set.

[0052] The classification item used for the classification information and the analysis item used for the transmission success condition of the map information can be arbitrarily determined as long as they are information of a type obtained from the received signal information. For example, the classification item is one or more of an area, a time zone, a day of the week, a month, a weather, a noise floor, etc. Further, the analysis item used for the transmission success condition is one or more of an elevation angle, a channel, the number of channels, the same signal transmission number, a transmission interval, a time zone, a day of the week, a month, a weather, a noise floor, etc. However, the same information as the classification item used for the classification information is not used for the analysis item of the transmission success condition. Note that even if they are the same type of information, when the value or value range of the analysis item is a part within the value range of the classification item, it can be used for the transmission success condition. For example, when the time zone 0 to 6 o'clock is included in the classification information, the time zones 0 to 2 o'clock, 2 to 4 o'clock, and 4 to 6 o'clock can be used for the transmission success condition.

[0053] For example, in a time zone where the transmission of the peripheral terminal station 2 is small, the interference is small, so it is assumed that the number of successful communications and the communication success rate will be high. Therefore, the time zone is used as the transmission success condition. The distribution of the number of successful communications or the communication success rate for each time zone represented by the map information can be used for the summary by time zone of the terminal station 2.

[0054] The operation of the wireless communication system 1 will be described. FIG. 5 is a flowchart showing the processing of the wireless communication system 1. The wireless communication system 1 executes the processing of FIG. 5 at a predetermined timing such as every predetermined period, or when an instruction is input manually.

[0055] The position detection unit 22 of the terminal station 2 detects the position of its own station when the terminal station 2 is installed or periodically, and outputs position information indicating the detected position to the transmission control unit 27 (step S101). Note that the terminal station 2 may not be provided with the position detection unit 22. In this case, the position information is registered in the control information storage unit 26 when the terminal station 2 is installed or the like. The terminal station 2 acquires at any time the data detected by a sensor (not shown) provided externally or internally, and writes the acquired data into the data storage unit 23 (step S102).

[0056] On the other hand, the terminal communication unit 32 of the mobile relay station 3 transmits a beacon signal while moving (step S201). The receiving unit 25 of the terminal station 2 receives the beacon signal transmitted from the mobile relay station 3 (step S103). The transmission control unit 27 instructs the transmission unit 24 to generate a terminal uplink signal upon receiving the beacon signal. Note that when the mobile relay station 3 does not transmit a beacon, the orbital information of the LEO satellite equipped with the mobile relay station 3 is stored in advance in the control information storage unit 26. The transmission control unit 27 acquires the time when the mobile relay station 3 passes over its own station based on the orbital information, and determines the time to transmit the terminal uplink signal within that time. The transmission control unit 27 instructs the transmission unit 24 to generate the terminal uplink signal at the determined time.

[0057] The transmission unit 24 reads out sensor data from the data storage unit 23 as terminal transmission data. The transmission unit 24 generates a terminal uplink signal in which the terminal transmission data is set. The transmission control unit 27 determines transmission conditions such as transmission timing, channel, number of transmissions of the same signal, transmission interval when the number of transmissions of the same signal is multiple times, and number of channels when using multiple channels. Further, the transmission control unit 27 acquires the environmental information of its own station. The environmental information is, for example, weather, noise floor of the used band, etc. The transmission control unit 27 may acquire the environmental information by a sensor or the like provided in its own station, or may receive it from another device via a network. For example, the transmission control unit 27 may acquire environmental information of the weather from another device via a network every predetermined time, store it in the control information storage unit 26, and read out the stored environmental information.

[0058] The transmission control unit 27 sets the terminal ID of its own station, the position information, the transmission condition notification information, and the environment information in the terminal uplink signal generated by the transmission unit 24. The transmission condition notification information indicates the transmission conditions used for the terminal uplink signal. The transmission condition notification information includes information such as the transmission time of the terminal uplink signal, the channel, the number of channels, the number of transmissions of the same signal, the transmission number, and the transmission interval. The transmission unit 24 wirelessly transmits the terminal uplink signal from the antenna 21 in accordance with the transmission conditions determined by the transmission control unit 27 for the terminal uplink signal (step S104). If the terminal station 2 has not received the transmission control information (step S105: NO), the process from step S102 is repeated. Note that the terminal station 2 may repeat the process from step S101.

[0059] The terminal signal receiving unit 321 of the mobile relay station 3 receives the terminal uplink signal transmitted from the terminal station 2 in step S104 by the antenna 31. The terminal signal demodulation unit 322 demodulates and decodes the terminal uplink signal to obtain the terminal ID, the position information, the transmission condition notification information, the environment information, and the sensor data. When the terminal uplink signal is normally received, the terminal signal demodulation unit 322 writes the received signal information in which the reception time of the terminal uplink signal, the terminal ID, the position information, the transmission condition notification information, the environment information, and the sensor data are associated with each other into the data storage unit 33 (step S202).

[0060] The data transmission control unit 34 determines whether communication with the base station 4 is possible (step S203). For example, the data transmission control unit 34 may calculate in advance the time during which the mobile relay station 3 can communicate with the base station 4 based on the orbital information of the LEO carrying the mobile relay station 3 and the position of the base station 4. Alternatively, the data transmission control unit 34 may determine that communication is possible when the base station communication unit 35 receives a base station uplink signal from the base station 4. When the data transmission control unit 34 determines that communication with the base station 4 is possible (step S203: YES), it reads out the terminal ID, reception time, and sensor data from the data storage unit 33 as transmission data and outputs them to the base station communication unit 35. The base station communication unit 35 wirelessly transmits a base station downlink signal with the transmission data set from the antenna 36 (step S204). The base station signal reception processing unit 42 of the base station 4 performs reception processing on the base station downlink signal received by the antenna station 41 from the mobile relay station 3 to obtain sensor data.

[0061] When the data transmission control unit 34 determines that communication with the base station 4 is impossible (step S203: NO), or after the processing of step S204, the mobile relay station 3 performs the processing of step S205. Note that the mobile relay station 3 may perform the processing of steps S203 to S204 and the processing after step S205 in parallel. The statistical calculation unit 371 determines whether it has acquired reception signal information of the amount of information necessary for analysis (step S205). For example, the statistical calculation unit 371 determines that it has acquired reception signal information of the amount of information necessary for analysis when it has acquired reception signal information for a predetermined number or more of terminal uplink signals from all the terminal stations 2. Alternatively, the statistical calculation unit 371 may determine that it has acquired reception signal information of the amount of information necessary for analysis when it has acquired reception signal information for a predetermined period of time, etc. When the statistical calculation unit 371 determines that it has not acquired reception signal information of the amount of information necessary for analysis (step S205: NO), it repeats the processing from step S201.

[0062] On the other hand, when the statistical calculation unit 371 determines that it has acquired the received signal information with the amount of information necessary for analysis (step S205: YES), it performs the process of step S206. That is, the statistical calculation unit 371 calculates the statistical information of the terminal uplink signals that have successfully been received for each category using the received signal information stored in the data storage unit 33 (step S206).

[0063] First, the statistical calculation unit 371 acquires additional acquisition information based on the information set in the signal reception information, and sets the acquired additional acquisition information in the signal reception information. For example, the statistical calculation unit 371 reads out the orbital information of the LEO satellite equipped with the mobile relay station 3 from the storage unit 372. The statistical calculation unit 371 calculates the position of the mobile relay station 3 at the reception time or transmission time set in the signal reception information using the orbital information. The statistical calculation unit 371 calculates the elevation angle from the position of the terminal station 2 read from the signal reception information to the calculated position of the mobile relay station 3. The statistical calculation unit 371 sets the calculated elevation angle in the additional acquisition information of the signal reception information.

[0064] Subsequently, the statistical calculation unit 371 reads out the classification information and the transmission success condition from the storage unit 372. Note that the classification information and the transmission success condition stored in the storage unit 372 can be changed at any timing by the base station 4 transmitting the changed classification information and transmission success condition to the mobile relay station 3. Note that instead of the classification information, the generation rule of the classification information and instead of the transmission success condition, the generation rule of the transmission success condition may be stored in the storage unit 372. For example, when an area is used as a classification item of the classification information, the unit for dividing the ground into areas may be stored as a generation rule. Also, when the number of channels is used as an analysis item of the transmission success condition, the fact that the number of channels is each value from 1 to 5 may be recorded as the generation rule of the transmission success condition. The statistical calculation unit 371 generates the classification information and the transmission success condition according to these generation rules.

[0065] The statistical calculation unit 371 classifies the received signal information according to the classification information. The classification items used for the classification information are one or more of, for example, area, time zone, day of the week, month, weather, noise floor, and the like. To classify the received signal information by area, the position information set in the signal reception information is referred to. Also, to classify the signal reception information by time zone, day of the week, or month, the reception time or transmission time set in the signal reception information is referred to.

[0066] For example, assume that the classification item used for the classification information is area. The statistical calculation unit 371 classifies the signal reception information into the signal reception information of area A, area B, etc. based on the classification information indicating the latitude and longitude ranges of area A, the latitude and longitude ranges of area B, and so on. Also, when the classification items used for the classification information are area and time zone, the statistical calculation unit 371 classifies the signal information into the signal reception information of each time zone in area A, each time zone in area B, and so on.

[0067] The statistical calculation unit 371 generates, for each classification information, map information obtained from the received signal information classified into that classification information as statistical information. The map information indicates the number of communication successes or the communication success rate of the terminal uplink signal according to the transmission success condition. The analysis items used for the transmission success condition are one or more of elevation angle, channel, number of channels, number of transmissions of the same signal, transmission interval, time zone, day of the week, month, weather, noise floor, and the like.

[0068] The terminal uplink signal with the signal reception information written in the data storage unit 33 indicates that the reception was successful. Therefore, the statistical calculation unit 371 identifies the reception signal information that meets the transmission success condition among the reception signal information classified based on the classification information, and sets the number of the identified reception signal information as the number of successful communications. Note that the communication success rate is calculated when the same signal transmission number is set in the transmission condition notification information. Specifically, the statistical calculation unit 371 extracts the reception signal information that meets the transmission success condition among the reception signal information classified based on the classification information. Further, the statistical calculation unit 371 identifies the signal reception information in which the same terminal ID is set and the reception time or transmission time included within a predetermined time is set, among the extracted reception signal information. The predetermined time is, for example, the time when the mobile relay station 3 passes over the terminal station 2 or a time slightly longer than that time. The statistical calculation unit 371 calculates the communication success rate by dividing the number of the identified signal reception information by the same signal transmission number set in those signal reception information.

[0069] As described above, for example, the statistical calculation unit 371 can generate map information representing the number of successful communications for each elevation angle of each area, map information representing the number of successful communications for each combination of the elevation angle and the same signal transmission number of each area, and the like. The statistical calculation unit 371 writes the classification information and the map information generated based on the signal reception information classified into the classification information into the storage unit 372 as statistical information.

[0070] The information generation unit 373 obtains, for each classification information, the value range of the analysis item for which the number of communication successes or the communication success rate is higher than a predetermined condition based on the map information (step S207). For example, the predetermined condition can be a value higher than a threshold value. The threshold value may be a predetermined value, or may be a value obtained by multiplying the maximum number of communication successes or the communication success rate by a coefficient α (0 < α < 1). Further, for example, the predetermined condition may be a value within a predetermined range centered on the value of the analysis item for which the maximum number of communication successes or the communication success rate is obtained. The information generation unit 373 extracts the map information of the obtained value range of the analysis item for each classification information and generates transmission control information (step S208). Alternatively, the information generation unit 373 may use the obtained value range of the analysis item as the transmission control information. In this case, the communication success number and the communication success rate are not included in the transmission control information. Further, the information generation unit 373 may use the map information as the transmission control information as it is. The information generation unit 373 writes the transmission control information generated for each classification information into the storage unit 372.

[0071] The notification unit 374 of the mobile relay station 3 reads out from the storage unit 372 the transmission control information to be transmitted to all or high-priority terminal stations 2 included in the current communication area. Information on the high-priority terminal stations 2 is stored in the storage unit 372 in advance. Further, for example, when the area information is included in the classification information, the notification unit 374 reads out the classification information set for the current communication area and the transmission control information associated with the classification information. The notification unit 374 outputs the read classification information and transmission control information as transmission data to the terminal signal modulation unit 323. The terminal signal modulation unit 323 performs encoding and modulation on the transmission data to generate a terminal downlink signal addressed to the terminal station 2. The terminal signal transmission unit 324 transmits the terminal downlink signal generated by the terminal signal modulation unit 323 from the antenna 31 (step S209).

[0072] The receiving unit 25 of the terminal station 2 receives the terminal downlink signal by the antenna 21 (step S105: YES). The receiving unit 25 acquires the classification information and the transmission control information from the received terminal downlink signal. The control information storage unit 26 stores the classification information and the transmission control information acquired by the receiving unit 25. Thereafter, the transmission control unit 27 controls the transmission unit 24 to transmit the terminal uplink according to the transmission conditions determined based on the transmission control information (step S106).

[0073] That is, the transmission unit 24 generates a terminal uplink signal in which the sensor data read from the data storage unit 23 is set as the terminal transmission data. The transmission control unit 27 selects the transmission control information used for determining the transmission conditions according to the classification information added to the transmission control information. For example, the transmission unit 24 specifies the classification information that matches the current situation based on the current time, the current weather, and the current noise floor, and selects the transmission control information associated with the specified classification information. Note that when only the area is used for the classification information and only the transmission control information of that area is distributed to the terminal station 2, the selection by the classification information can be omitted.

[0074] The transmission control unit 27 determines transmission conditions such as transmission timing, channel, number of signals transmitted simultaneously, transmission interval, and number of channels based on the selected transmission control information. Note that the transmission unit 24 determines the transmission conditions not included in the transmission control information based on an arbitrary rule. When the transmission control information indicates the number of successful communications or the communication success rate for each transmission condition represented by the numerical range of each item, the transmission control unit 27 selects the value of each item that becomes the transmission condition with a probability of weighted according to the number of successful communications or the communication success rate from among those numerical ranges, or randomly. Further, the transmission control unit 27 may select the value of each item so that the probability of selecting a value within the numerical range set in the transmission control information is high and the probability of selecting a value outside the numerical range is low.

[0075] For example, in the transmission control information, the transmission conditions indicating the number of signals transmitted simultaneously of 2 to 4 and the number of channels of 1 to 3, and the number of successful communications or the communication success rate p of the number of signals transmitted simultaneously a (a = 2, 3, 4) aand the number of successful communications or the communication success rate k for the number of channels b (b = 1, 2, 3) b be set. In this case, the transmission control unit 27 weights the number of transmissions of the same signal so that the number of transmissions of the same signal a becomes the probability of p a / (p2 + p3 + p4) and selects the number of transmissions of the same signal. Further, the transmission control unit 27 weights the number of transmissions of the same signal so that the number of channels b becomes the probability of p b / (p1 + p2 + p3) and selects the number of transmissions of the same signal. Also, when the number of transmissions of the same signal 2 to 4 and the number of channels 1 to 3 are set in the transmission control information and the number of successful communications and the communication success rate are not set, the transmission control unit 27 may select the number of transmissions of the same signal 2, 3, and 4 with the same probability respectively, and select the number of channels 1, 2, and 3 with the same probability respectively. Further, the transmission control unit 27 may select the number of transmissions of the same signal and the number of channels with the probability weighted so that the weights are higher for the median or the average value respectively.

[0076] Also, when the number of successful communications is set for each combination of a plurality of items in the transmission control information, the transmission control unit 27 determines the transmission conditions in the same manner as described above for those combinations of items. For example, in the transmission control information, the transmission conditions indicating the number of transmissions of the same signal 2 to 4 and the number of channels 1 to 3, and the number of successful communications or the communication success rate of (the number of transmissions of the same signal a, the number of channels b) are each p ab be set. In this case, the transmission control unit 27 sets (the number of transmissions of the same signal a, the number of channels b) to p ab / (p 21 + p 22 + p 23 + p 31 + p 32 + p 33 + p 41 + p 42 + p 43 ) and selects it with that probability.

[0077] Note that when the transmission control unit 27 determines the value of the elevation angle as the transmission condition, based on the position of its own station and the orbital information of the LEO satellite equipped with the mobile relay station 3, it calculates the transmission time at which the elevation angle from its own station to the mobile relay station 3 becomes the determined value. The transmission control unit 27 controls the transmission unit 24 to transmit the terminal uplink signal at the calculated transmission time.

[0078] Also, when the transmission control information includes items that cannot be controlled at the terminal station 2, such as time zone, day of the week, weather, noise floor, etc., the transmission control unit 27 limits the available transmission conditions among the transmission conditions indicated by the transmission control information according to the values of those items. The transmission control unit 27 selects the values of each item that become the transmission conditions with a probability weighted according to the number of communication successes or the communication success rate from within the range of the values of each item indicated by the limited transmission conditions, or randomly.

[0079] For example, in the transmission control information, in the time zone t1 to t2, the number of transmissions of the same signal a1 = 2 to 4, the number of channels b1 = 1 to 3, and the number of communication successes of (the number of transmissions of the same signal a1, the number of channels b1) are each p ab and in the time zone t2 to t3, the number of transmissions of the same signal a2 = 2 to 4, the number of channels b2 = 2 to 3, and the number of communication successes of (the number of transmissions of the same signal a2, the number of channels b2) are each q ab are set. When the current time t is within the time zone t2 to t3, the transmission control unit 27 selects the number of transmissions of the same signal and the number of channels from among the number of transmissions of the same signal a2 = 2 to 4 and the number of channels b2 = 2 to 3 based on the number of communication successes q of (the number of transmissions of the same signal a2, the number of channels b2). ab

[0080] After step S106, the transmission control unit 27 may not set the transmission condition notification information and the environment information in the terminal uplink signal. When the mobile relay station 3 receives the terminal uplink signal transmitted from the terminal station 2, it performs the same operations as in steps S202 to S204. However, the mobile relay station 3 may not acquire the transmission condition information and the environment information.

[0081] ​Note that in step S104, the terminal station 2 does not have to set information that is not used for either the classification items or the analysis items in the terminal uplink signal. Further, the statistical calculation unit 371 of the mobile relay station 3 may generate statistical information for a combination of a plurality of types of classification items and analysis items, and select, as the statistical information for generating transmission control information, the statistical information using the combination of the classification items and the analysis items in which a peak appears in the number of communication successes or the communication success rate.

[0082] In this embodiment, the number of times the terminal uplink signal could not be received normally (hereinafter referred to as failure) and the population of the terminal station 2 cannot be detected. Therefore, when the number of transmissions of the same signal is not set in the terminal uplink signal, or when many terminal uplink signals are transmitted only once, the communication success rate cannot be obtained. For example, when 5 out of 6 terminal stations 2 in a certain area succeed in transmission at elevation angle θ1 and 5 out of 50 terminal stations 2 succeed in transmission at elevation angle θ2, the number of communication successes is the same but the communication success rates are different. However, as follows, if the number of communication successes is obtained, the communication success rate does not have to be obtained.

[0083] In the case of the above example, since the number of communication successes is equal, the probability that the terminal station 2 selects elevation angle θ1 and elevation angle θ2 in the next transmission opportunity is about the same. Then, in the next transmission opportunity, the number of communication successes at elevation angle θ1 increases and the number of communication successes at elevation angle θ2 decreases. If the wireless communication system 1 repeatedly performs the process of FIG. 5 regularly, the population will naturally increase for the conditions with a high communication success rate. Therefore, even if the population or the number of failures is unknown, the terminal station 2 can transmit the terminal uplink signal under the transmission conditions with a high communication success rate. Note that when the access becomes congested, the noise floor of that band rises. Therefore, it is conceivable to generate map information of the number of communication successes using the noise floor as an analysis item.

[0084] Once the statistical information is created, it is also assumed that it may change due to factors such as the increase or decrease of the terminal stations 2 within the wireless communication system 1 and changes in the communication environment. Considering this, the analysis unit 37 may set a finite period during which the statistical information can be used and generate transmission control information using the statistical information of the moving average. Also, the analysis unit 37 may create statistical information for each different environment. For example, the analysis unit 37 may create statistical information for each environmental condition such as the number of terminal stations 2 within the area and the weather.

[0085] In urban areas, since the number of constant transmissions from the terminal stations 2 is large, in other areas, the communication success rate improves when the self - area is within the coverage and the urban area is outside the coverage. In such cases, fixed information such as the number of terminals in other areas may be further used as classification information.

[0086] (Second Embodiment) In the second embodiment, the base station generates transmission condition information. Hereinafter, the description will focus on the differences from the first embodiment.

[0087] FIG. 6 is a configuration diagram of the wireless communication system 11 according to the second embodiment. The wireless communication system 11 includes a terminal station 2, a mobile relay station 5, and a base station 6. The differences between the wireless communication system 11 shown in FIG. 6 and the wireless communication system 1 of the first embodiment shown in FIG. 2 are that it includes a mobile relay station 5 instead of the mobile relay station 3 and a base station 6 instead of the base station 4.

[0088] The difference between the mobile relay station 5 and the mobile relay station 3 of the first embodiment is that it is provided with a data storage unit 51, a data transmission control unit 52, a notification information storage unit 53, and a notification unit 54 instead of the data storage unit 33, the data transmission control unit 34, and the analysis unit 37. The data storage unit 51 stores the same signal reception information as in the first embodiment. However, the signal reception information stored in the data storage unit 51 does not include additional acquisition information. The data transmission control unit 52 outputs the signal reception information stored in the data storage unit 51 to the base station communication unit 35 as transmission data to the base station 6. The notification information storage unit 53 stores the transmission control information received from the base station 6. The notification unit 54 reads out the transmission control information from the notification information storage unit 53 and notifies the terminal station 2 of the read transmission control information by the same process as the notification unit 374 of the first embodiment.

[0089] The difference between the base station 6 and the base station 4 shown in FIG. 2 is that it is provided with a data storage unit 61 and an analysis unit 62 instead of the notification unit 44. The data storage unit 61 stores signal reception information. The analysis unit 62 includes a statistical calculation unit 621, a storage unit 622, an information generation unit 623, and a notification unit 624. The statistical calculation unit 621, the storage unit 622, and the information generation unit 623 each perform the same processes as the statistical calculation unit 371, the storage unit 372, and the information generation unit 373 included in the analysis unit 37 of the mobile relay station 3 of the first embodiment shown in FIG. 2. The notification unit 624 transmits the transmission control information associated with the classification information to the mobile relay station 5. The mobile relay station 5 distributes the received transmission control information to all the terminal stations 2 or the terminal stations 2 with high priority. Alternatively, the notification unit 624 may distribute the transmission control information to each terminal station 2.

[0090] FIG. 7 is a flowchart showing the processing of the wireless communication system 11. In FIG. 7, the same processes as those in the first embodiment shown in FIG. 5 are denoted by the same reference numerals, and the detailed description thereof is omitted. The wireless communication system 11 executes the processing in FIG. 7 at a predetermined timing such as every predetermined period, or when an instruction is input manually.

[0091] The processing of steps S101 to S105 of the terminal station 2 and the processing of steps S201 to S202 of the mobile relay station 5 are the same as those in the first embodiment. However, in step S202, the terminal signal demodulation unit 322 writes the received signal information in which the reception time of the terminal uplink signal, the terminal ID, the position information, the transmission condition notification information, the environment information, and the sensor data are associated with each other into the data storage unit 51.

[0092] The data transmission control unit 52 determines whether communication with the base station 6 is possible by the same processing as in step S203 of FIG. 5 (step S301). When the data transmission control unit 52 determines that communication with the base station 6 is impossible (step S301: NO), it performs the processing from step S201.

[0093] When the data transmission control unit 52 determines that communication with the base station 6 is possible (step S301: YES), it reads the received signal information from the data storage unit 51 and outputs it to the base station communication unit 35. The base station communication unit 35 wirelessly transmits the base station downlink signal in which the received signal information is set from the antenna 36 (step S302). The mobile relay station 5 determines whether transmission control information has been received (step S303). When the mobile relay station 5 has not received the transmission control information (step S303: NO), it repeats the processing from step S201.

[0094] On the other hand, the antenna station 41 of the base station 6 receives the base station downlink signal transmitted in step S302. The base station signal reception processing unit 42 performs reception processing on the base station downlink signal received by the antenna station 41 from the mobile relay station 5 to obtain signal reception information. The base station signal reception processing unit 42 writes the obtained signal reception information into the data storage unit 61 (step S401).

[0095] The analysis unit 62 of the base station 6 performs the same processing as steps S205 to S208 of the analysis unit 37 of the mobile relay station 3 in the first embodiment shown in FIG. 5 (steps S402 to step S405). That is, when the statistical calculation unit 621 determines that the received signal information of the amount of information required for analysis has not been acquired (step S402: NO), the processing from step S401 is repeated. When the statistical calculation unit 621 determines that the received signal information of the amount of information required for analysis has been acquired (step S403: YES), statistical information for each classification information is calculated using the received signal information stored in the data storage unit 61 (step S403). The statistical calculation unit 621 generates, for each classification information, map information indicating the number of communication successes or the communication success rate of the terminal uplink signal for each transmission success condition as statistical information using the information obtained from the received signal information, and writes it to the storage unit 622. The information generation unit 623 obtains, for each classification information, the value range of the analysis item for which the number of communication successes or the communication success rate is higher than a predetermined condition based on the map information (step S404). The information generation unit 623 generates, for each classification information, the map information extracted for the obtained value range of the analysis item, or the transmission control information in which the value range of the calculated analysis item is set (step S405). The information generation unit 623 may use the map information as the transmission control information. The information generation unit 623 writes the transmission control information for each classification information to the storage unit 622.

[0096] When the base station 6 becomes communicable with the mobile relay station 5, the notification unit 624 reads out the transmission control information from the storage unit 622. For example, the notification unit 624 may calculate in advance the time when the base station 6 can communicate with the mobile relay station 5 based on the orbital information of the LEO mounted on the mobile relay station 5 and the position of the base station 6. Alternatively, when the base station signal reception processing unit 42 of the base station 6 receives a beacon from the mobile relay station 5, the notification unit 624 may determine that communication is possible. The notification unit 624 outputs the read transmission control information to the base station signal transmission processing unit 43. The base station signal transmission processing unit 43 generates a base station uplink signal with the transmission control information set, and transmits the generated base station uplink signal from the antenna station 41 (step S406).

[0097] The base station communication unit 35 of the mobile relay station 5 receives the base station downlink signal with transmission control information set by the antenna 36 (step S303: YES). The base station communication unit 35 writes the transmission control information obtained by performing the reception process of the received base station uplink signal into the notification information storage unit 53 (step S304).

[0098] The notification unit 54 transmits the transmission control information to all or the high-priority terminal stations 2 included in the current communication area of the mobile relay station 5 by the same process as step S209 in FIG. 5 (step S305). Information on the high-priority terminal stations 2 is stored in the notification information storage unit 53 in advance. Also, for example, when the area information is included in the classification information, the notification unit 54 reads out from the notification information storage unit 53 the classification information with the current communication area set and the transmission control information associated with the classification information. The notification unit 54 transmits the read classification information and transmission control information from the terminal communication unit 32 by the terminal downlink signal.

[0099] The terminal station 2 receives the terminal downlink signal by the antenna 21 and performs the same process as the first embodiment shown in FIG. 3. That is, the receiving unit 25 of the terminal station 2 receives the terminal downlink signal by the antenna 21 (step S105: YES). The receiving unit 25 stores the classification information and transmission control information obtained from the terminal downlink signal in the control information storage unit 26. Thereafter, the transmission control unit 27 controls the transmission unit 24 to transmit the terminal uplink according to the transmission conditions determined based on the transmission control information (step S106).

[0100] Note that a communication control device, which is an external device connected to the base station 6, may include an analysis unit 62. The communication control device may further include a data storage unit 61. The communication control device may further include a communication unit 45 and distribute the generated transmission control information to the terminal stations 2.

[0101] According to this embodiment, it is possible to generate communication control information while reducing the load on the mobile relay station 5.

[0102] (Third Embodiment) In the third embodiment, the base station demodulates the terminal uplink signal and generates transmission condition information. Below, the description will focus on the differences from the first and second embodiments.

[0103] FIG. 8 is a configuration diagram of a wireless communication system 12 according to the third embodiment. The wireless communication system 12 includes a terminal station 2, a mobile relay station 7, and a base station 8. The difference between the wireless communication system 11 shown in FIG. 8 and the wireless communication system 11 of the second embodiment shown in FIG. 6 is that it includes a mobile relay station 7 instead of the mobile relay station 5 and a base station 8 instead of the base station 6.

[0104] The difference between the mobile relay station 7 and the mobile relay station 5 shown in FIG. 6 is that it includes a terminal communication unit 71, a data storage unit 72, and a data transmission control unit 73 instead of the terminal communication unit 32, the data storage unit 51, and the data transmission control unit 52.

[0105] The terminal communication unit 71 includes a receiving unit 711, a received waveform recording unit 712, a terminal signal modulation unit 323, and a terminal signal transmission unit 324. The receiving unit 711 receives a signal via the antenna 31. The receiving unit 711 down-converts the received signal and frequency-converts the received signal from an RF signal to a baseband signal. The received waveform recording unit 712 samples the received waveform of the received signal frequency-converted by the receiving unit 711 and generates waveform data indicating the values obtained by the sampling. The received waveform recording unit 712 writes received waveform information in which the reception time of the received signal and the waveform data are set into the data storage unit 72. The data storage unit 72 stores the received waveform information generated by the received waveform recording unit 712. The data transmission control unit 73 outputs the received waveform information stored in the data storage unit 72 as transmission data to the base station communication unit 35.

[0106] The difference between base station 8 and base station 6 shown in FIG. 6 is that base station 8 further includes a terminal signal reception processing unit 81. The terminal signal reception processing unit 81 inputs the reception waveform information obtained by the base station signal reception processing unit 42 demodulating and decoding the base station downlink signal. The terminal signal reception processing unit 81 performs reception processing on the reception signal indicated by the reception waveform information. The terminal signal reception processing unit 81 includes a reception processing unit 811 and a demodulation unit 812. The reception processing unit 811 converts the reception signal indicated by the waveform data from an analog signal to a digital signal and then performs FFT. The reception processing unit 811 outputs the FFT'd reception signal to the demodulation unit 812. The demodulation unit 812 performs the same processing as the terminal signal demodulation unit 322 of the mobile relay station 3 in the first embodiment shown in FIG. 2.

[0107] FIG. 9 is a flowchart showing the processing of the wireless communication system 12. In FIG. 9, the same processing as that in the second embodiment shown in FIG. 7 is denoted by the same reference numerals, and the detailed description thereof is omitted. The wireless communication system 12 executes the processing in FIG. 9 at a predetermined timing such as every predetermined period, or when an instruction is input manually.

[0108] The processing of steps S101 to S105 of the terminal station 2 and the processing of step S201 of the mobile relay station 7 are the same as those in the first embodiment. The antenna 31 of the mobile relay station 7 receives the terminal uplink signal transmitted by the terminal station 2 in step S104. The reception unit 711 down-converts the terminal uplink signal received by the antenna 31. The reception waveform recording unit 712 samples the reception waveform of the down-converted terminal uplink signal and generates waveform data indicating the values obtained by the sampling. The reception waveform recording unit 712 writes the reception waveform information in which the reception time of the reception signal and the waveform data are set into the data storage unit 72 (step S501).

[0109] The data transmission control unit 73 determines whether communication with the base station 8 is possible by the same processing as in step S203 of FIG. 5 (step S502). When the data transmission control unit 73 determines that communication with the base station 8 is impossible (step S502: NO), it performs the processing from step S201.

[0110] When the data transmission control unit 73 determines that communication with the base station 8 is possible (step S502: YES), it reads the received waveform information from the data storage unit 72 and outputs it to the base station communication unit 35. The base station communication unit 35 wirelessly transmits the base station downlink signal set with the received waveform information from the antenna 36 (step S503). After the process of step S503, the mobile relay station 7 performs the process from step S303. The processes of the mobile relay station 7 after step S303 and the process of step S106 of the terminal station 2 are the same as those in the second embodiment.

[0111] On the other hand, the antenna station 41 of the base station 8 receives the base station downlink signal transmitted in step S503. The base station signal reception processing unit 42 performs reception processing on the base station downlink signal received by the antenna station 41 from the mobile relay station 3 to obtain received waveform information. The reception processing unit 811 of the terminal signal reception processing unit 81 reads waveform data from the received waveform information. The reception processing unit 811 converts the terminal uplink signal indicated by the waveform data from an analog signal to a digital signal and then performs FFT. The demodulation unit 812 demodulates and decodes the FFTed terminal uplink signal to obtain the terminal ID, location information, transmission condition notification information, environmental information, and sensor data. When the reception processing of the terminal uplink signal is normally performed, the demodulation unit 812 writes the received signal information in which the reception time of the terminal uplink signal obtained from the received waveform information, the terminal ID obtained from the terminal uplink signal, the location information, the transmission condition notification information, the environmental information, and the sensor data are associated with each other into the data storage unit 61 (step S601).

[0112] The subsequent processing of the base station 8 from step S402 is the same as that in the second embodiment. However, in step S402, when the statistical calculation unit 621 determines that it has not acquired the received signal information of the amount of information required for analysis (step S402: NO), it repeats the process from step S601.

[0113] Note that a communication control device, which is an external device connected to the base station 8, may include an analysis unit 62. The communication control device may further include a data storage unit 61. The communication control device may further include a communication unit 45 and distribute the generated transmission control information to the terminal station 2.

[0114] According to the present embodiment, it is possible to generate communication control information while reducing the load on the mobile relay station 7. Further, even when the radio communication method used in the terminal station 2 is changed or added, the radio communication method may be implemented in the base station 8, and the mobile relay station 7 does not need to be updated.

[0115] When the terminal station performs transmission by the autonomous distributed control LPWA method under the condition that the radio communication system of the present embodiment is a communication environment with high periodicity and reproducibility, transmission conditions with a high communication success rate are analyzed based on statistical information. The terminal station uses the analysis result to select transmission conditions such as transmission timing and performs transmission under the selected transmission conditions. This enables highly reliable communication.

[0116] A hardware configuration example of the mobile relay station 3 will be described. FIG. 10 is a device configuration diagram showing a hardware configuration example of the mobile relay station 3. The mobile relay station 3 includes a processor 91, a storage unit 92, a communication interface 93, and a user interface 94.

[0117] The processor 91 is a central processing unit that performs operations and controls. The processor 91 is, for example, a CPU (central processing unit). The storage unit 92 is a storage device such as various memories and hard disks. By the processor 91 reading a program from the storage unit 92 and executing it, the analysis unit 37 is realized. A part of the functions of the analysis unit 37 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The storage unit 92 further has a work area and the like when the processor 91 executes various programs. The communication interface 93 is connected to be communicable with other devices. The communication interface 93 corresponds to the terminal communication unit 32 and the base station communication unit 35. The user interface 94 is an input device such as a keyboard, a pointing device (mouse, tablet, etc.), buttons, a touch panel, etc., and a display device such as a display. An artificial operation is input through the user interface 94.

[0118] The hardware configuration of the terminal station 2 is also the same as that in FIG. 10. By the processor 91 reading a program from the storage unit 92 and executing it, the transmission control unit 27 is realized. The communication interface 93 corresponds to the transmission unit 24 and the reception unit 25.

[0119] The hardware configuration of the base station 6 is also the same as that in FIG. 10. By the processor 91 reading a program from the storage unit 92 and executing it, the analysis unit 62 is realized. The communication interface 93 corresponds to the base station signal reception processing unit 42, the base station signal transmission processing unit 43, and the communication unit 45.

[0120] The hardware configuration of the base station 8 is also the same as that in FIG. 10. By the processor 91 reading a program from the storage unit 92 and executing it, the analysis unit 62 is realized. The communication interface 93 corresponds to the base station signal reception processing unit 42, the base station signal transmission processing unit 43, the communication unit 45, and the terminal signal reception processing unit 81.

[0121] The hardware configuration of the communication control device is also the same as that in FIG. 10. The analysis unit 62 is realized by the processor 91 reading and executing a program from the storage unit 92.

[0122] According to the embodiment described above, it is possible to reduce the amount of data when the relay device relays the data received while moving. In the above embodiment, the case where the moving body on which the mobile relay station is mounted is a LEO satellite has been described, but it may be a stationary satellite, a drone, or another flying body flying in the air such as HAPS.

[0123] According to the above-described embodiments, the wireless communication system includes a transmission device and a moving communication device. For example, the transmission device is the terminal station 2 of the embodiment, and the communication devices are the moving relay stations 3, 5, and 7 of the embodiment. The transmission device includes a wireless transmission unit and a transmission control unit. For example, the wireless transmission unit is the transmission unit of the embodiment, and the transmission control unit is the transmission control unit 27 of the embodiment. The wireless transmission unit transmits a wireless signal to the communication device. The transmission control unit determines the transmission conditions of the wireless signal and controls the wireless transmission unit to transmit a first wireless signal according to the determined transmission conditions. The communication device includes a reception unit. For example, the reception unit is the terminal communication units 32 and 71 of the embodiment. The reception unit receives the first wireless signal transmitted from the transmission device. The wireless communication system includes a statistical calculation unit, an information generation unit, and a notification unit. The statistical calculation unit is the statistical calculation units 371 and 621 of the embodiment, the information generation unit is the information generation units 373 and 623 of the embodiment, and the notification unit is the notification units 374, 624, and 54 of the embodiment. The statistical calculation unit acquires the transmission conditions used for the first wireless signal transmitted from the transmission device within the area and normally received by the reception unit, and generates statistical information on the acquired transmission conditions. The information generation unit extracts transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions. The notification unit notifies the transmission control information generated by the information generation unit to the transmission devices within the area. The notification unit may notify the transmission control information to the transmission device with a high priority among the transmission devices within the area. The transmission control unit determines the transmission conditions of the wireless signal based on the transmission control information, and controls the wireless transmission unit to transmit a second wireless signal according to the determined transmission conditions.

[0124] The transmission conditions may include one or more of the transmission time at the transmission device, the direction of the communication device with respect to the transmission device, the number of signals transmitted, the channel, the number of channels, and the transmission interval. Further, the statistical calculation unit may calculate the direction of the communication device with respect to the transmission device based on the position of the communication device at the transmission time or the time when the reception unit receives the first wireless signal and the position of the transmission device.

[0125] The transmission control unit may set information that can acquire the transmission conditions used for transmitting the first radio signal in the first radio signal. The statistical calculation unit acquires the transmission conditions from the first radio signal normally received by the reception unit.

[0126] The transmission control unit may set information on the surrounding environment of the transmission device in the first radio signal. The statistical calculation unit generates statistical information on the transmission conditions used for the first radio signal normally received by the reception unit and the surrounding environment acquired from the first radio signal normally received by the reception unit. The transmission control unit determines the transmission conditions of the radio signal based on the transmission control information and the information on the surrounding environment of the transmission device, and controls the radio transmission unit to transmit the second radio signal according to the determined transmission conditions. The information on the surrounding environment includes one or both of weather information and noise floor information.

[0127] The transmission control unit may set position information indicating the position of its own device in the first radio signal. The statistical calculation unit specifies the area based on the position information set in the first radio signal.

[0128] The communication device may include a statistical calculation unit, an information generation unit, and a notification unit.

[0129] The communication device may further include a transmission unit. The transmission unit transmits the data received by the reception unit from the transmission device by radio signals to the reception device. In this case, the reception device may include a statistical calculation unit and an information generation unit.

[0130] The wireless communication system may further include a control device. The control device includes a statistical calculation unit, an information generation unit, and a notification unit.

[0131] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and designs and the like within the scope not departing from the gist of the present invention are also included.

Explanation of Signs

[0132] 1, 11, 12... Wireless communication system 2... Terminal station 3, 5, 7... mobile relay stations 4, 6, 8... base stations 21... antenna 22... position detection unit 23... data storage unit 24... transmission unit 25... reception unit 26... control information storage unit 27... transmission control unit 28... communication unit 31, 36... antenna 32... terminal communication unit 33... data storage unit 34... data transmission control unit 35... base station communication unit 37... analysis unit 41... antenna station 42... base station signal reception processing unit 43... base station signal transmission processing unit 44... notification unit 45... communication unit 51... data storage unit 52... data transmission control unit 53... notification information storage unit 54... notification unit 61... data storage unit 62... analysis unit 71... terminal communication unit 72... data storage unit 73... data transmission control unit 81... terminal signal reception processing unit 91... processor 92... storage unit 93... communication interface 94... user interface 321... terminal signal reception unit 322... terminal signal demodulation unit 323... terminal signal modulation unit 324... terminal signal transmission unit 371... statistical calculation unit 372... storage unit 373... information generation unit 374... notification unit 621…Statistical calculation unit, 622…Memory unit, 623…Information generation unit, 624…Notification unit, 711…Receiving unit, 712…Received waveform recording unit, 811…Receiving processing unit, 812…Demodulation unit

Claims

1. A wireless communication system having a transmitting device and a moving communication device, The transmitting device includes: A wireless transmission unit that transmits a wireless signal to the communication device; A transmission control unit that determines transmission conditions of the wireless signal and controls the wireless transmission unit to transmit a first wireless signal according to the determined transmission conditions. The communication device includes: A receiving unit that receives the first wireless signal transmitted from the transmitting device. The wireless communication system includes: A statistical calculation unit that acquires transmission conditions used for the first wireless signal transmitted from the transmitting device within the area and normally received by the receiving unit, and generates statistical information of the acquired transmission conditions; An information generation unit that extracts transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions; A notification unit that notifies the transmitting device within the area of the transmission control information generated by the information generation unit. The transmission control unit determines the transmission conditions of the wireless signal based on the transmission control information, and controls the wireless transmission unit to transmit a second wireless signal according to the determined transmission conditions. Wireless communication system.

2. The transmission conditions include one or more of a transmission time at the transmitting device, a direction of the communication device with respect to the transmitting device, the number of signals transmitted, a channel, the number of channels, and a transmission interval. The wireless communication system according to Claim 1.

3. The statistical calculation unit calculates the direction of the communication device with respect to the transmitting device based on the transmission time or the position of the communication device at the time when the receiving unit receives the first wireless signal and the position of the transmitting device. The wireless communication system according to Claim 2.

4. The transmission control unit sets information that can acquire the transmission conditions used for transmitting the first radio signal in the first radio signal. The statistical calculation unit acquires the transmission conditions from the first radio signal normally received by the reception unit. The wireless communication system according to any one of claims 1 to 3.

5. The transmission control unit sets information on the surrounding environment of the transmission device in the first radio signal. The statistical calculation unit generates statistical information on the transmission conditions used for the first radio signal normally received by the reception unit and the surrounding environment acquired from the first radio signal normally received by the reception unit. The transmission control unit determines the transmission conditions of the radio signal based on the transmission control information and the information on the surrounding environment of the transmission device, and controls the wireless transmission unit to transmit a second radio signal according to the determined transmission conditions. The wireless communication system according to any one of claims 1 to 3.

6. The information on the surrounding environment includes one or both of weather information and noise floor information. The wireless communication system according to claim 5.

7. The transmission control unit sets position information indicating the position of its own device in the first radio signal. The statistical calculation unit identifies the area based on the position information set in the first radio signal. The wireless communication system according to any one of claims 1 to 6.

8. The communication device includes the statistical calculation unit, the information generation unit, and the notification unit. The wireless communication system according to any one of claims 1 to 7.

9. The transmission device is installed on the earth. The communication device is provided in a low-earth orbit satellite. The wireless communication system according to any one of claims 1 to 8.

10. The communication device further includes a transmission unit that transmits data received by the reception unit from the transmission device by a radio signal to a reception device. The reception device includes the statistical calculation unit and the information generation unit. The wireless communication system according to any one of claims 1 to 7.

11. The transmission device and the reception device are installed on the earth. The communication device is provided in a low-earth orbit satellite. The wireless communication system according to claim 10.

12. The notification unit notifies the transmission control information to a transmission device with a high priority among the transmission devices in the area. The wireless communication system according to any one of claims 1 to 11.

13. A reception unit that receives a radio signal; A statistical calculation unit that acquires transmission conditions used for transmission of the radio signal transmitted from a transmission device in an area and normally received by the reception unit, and generates statistical information on the acquired transmission conditions; An information generation unit that extracts transmission conditions with a high probability of normally receiving a radio signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions; A notification unit that notifies the transmission control information generated by the information generation unit to transmission devices in the area; A communication device comprising:

14. A statistical calculation unit that acquires transmission conditions used for transmission of a radio signal transmitted from a transmission device in an area and normally received by a communication device, and generates statistical information on the acquired transmission conditions; An information generation unit that extracts transmission conditions with a high probability of normally receiving a radio signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions; A notification unit that notifies the transmission control information generated by the information generation unit to transmission devices in the area; A communication control device comprising

15. A wireless communication method executed by a wireless communication system having a transmission device and a moving communication device, a wireless transmission step in which a wireless transmission unit of the transmission device transmits a wireless signal to the communication device; a transmission control unit and step in which a transmission control unit of the transmission device determines transmission conditions of a wireless signal and controls the wireless transmission unit to transmit a first wireless signal according to the determined transmission conditions; a reception step in which a reception unit of the communication device receives the first wireless signal transmitted from the transmission device; a statistical calculation step in which the wireless communication system acquires transmission conditions used for the first wireless signal transmitted from the transmission device within an area and normally received in the reception step, and generates statistical information of the acquired transmission conditions; an information generation step in which the wireless communication system extracts transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information, and generates transmission control information indicating the extracted transmission conditions; a notification step in which the wireless communication system notifies the transmission device within the area of the generated transmission control information; a step in which the transmission control unit determines transmission conditions of a wireless signal based on the transmission control information, and controls the wireless transmission unit to transmit a second wireless signal according to the determined transmission conditions; A wireless communication method having

16. a reception step of receiving a wireless signal; a statistical calculation step in which transmission conditions used for transmission of the wireless signal transmitted from a transmission device within an area and normally received in the reception step are acquired, and statistical information of the acquired transmission conditions is generated; an information generation step in which transmission conditions with a high probability of normally receiving a wireless signal are extracted based on the statistical information, and transmission control information indicating the extracted transmission conditions is generated; A notification step of notifying the generated transmission control information to a transmission device within the area; A wireless communication method having the above.

17. A statistical calculation step of obtaining transmission conditions used for transmission of a wireless signal transmitted from a transmission device within an area and normally received by a communication device, and generating statistical information on the obtained transmission conditions; An information generation step of extracting transmission conditions with a high probability of normally receiving a wireless signal based on the statistical information, and generating transmission control information indicating the extracted transmission conditions; A notification step of notifying the generated transmission control information to the transmission device within the area; A communication control method having the above.

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