WO2022123902A1

WO2022123902A1 - Communication device, communication method, and communication system

Info

Publication number: WO2022123902A1
Application number: PCT/JP2021/038067
Authority: WO
Inventors: 沢子桐山
Original assignee: ソニーグループ株式会社
Priority date: 2020-12-09
Filing date: 2021-10-14
Publication date: 2022-06-16
Also published as: JPWO2022123902A1

Abstract

Provided is a communication device for receiving a frame from a terrestrial terminal.　The communication device, which orbits the Earth in a predetermined orbit and operates as one of satellite receiving stations to receive a frame from a terrestrial terminal, comprises a receiving unit for performing a receiving process for a frame from the terminal, and a determining unit which, on the basis of frame reception information at the time of reception of the frame from the terminal, a frame transmission interval of the terminal, and the positional relationship of surrounding satellite receiving stations, determines a satellite receiving station suitable for receiving a frame transmitted from the terminal next. The frame reception information includes a frequency error estimation result and a propagation delay estimation result at the time of reception of the frame.

Description

Communication equipment and methods, and communication systems

The technique disclosed in the present specification (hereinafter referred to as "the present disclosure") relates to a communication device and a communication method for receiving a frame wirelessly transmitted from a terminal on the ground, and a communication system including a terminal and a receiving station.

In the wireless sensor network, it is possible to create new services by attaching wireless sensor terminals to people and things and periodically transmitting information acquired from the sensors. For example, by attaching a wireless sensor terminal with GPS (Global Positioning System) to elderly people and children and periodically transmitting location information, a monitoring service becomes possible.

In such a wireless communication system for IoT (Internet of Things), it is necessary to enable communication with many wireless sensor terminals attached to various people and things, and long-distance transmission that enables wide-area communication. It is important to accommodate multiple terminals that enable communication with many terminals per base station. In recent years, LPWA (Low Power Wide Area Area), which has been regarded as a promising wireless communication method for IoT, has made it possible to realize long-distance transmission and multi-terminal accommodation, and it is possible to realize long-distance transmission and multi-terminal accommodation. A long-distance transmission of 100 km is realized (see, for example, Patent Document 1). However, the installation of a receiving station requires securing a site and laying a network for cloud connection, which is costly and time-consuming, which hinders the cost reduction of communication services and the expansion of communication areas.

On the other hand, in recent years, space development by private companies has been actively carried out, and it used to require tens of billions of yen to launch a satellite, but it was developed with the aim of reducing costs to 1/10 to 1/100. Is progressing. In addition, the miniaturization of satellites is progressing, and it is being considered to realize a service that covers the entire earth by launching multiple satellites at once and building a constellation.

With the realization of satellite services, as a method of expanding the communication area of LPWA, it is conceivable to mount a receiver on the satellite and receive the radio waves transmitted by the terminals on the ground on the satellite. LPWA realizes communication of several hundred kilometers even on the ground, and it is considered that low-earth orbit satellites can sufficiently communicate. In addition, since low earth orbit satellites orbit the earth, it is possible to cover the entire earth with a small number of satellites in use cases such as IoT where data is transmitted once every few minutes to several days. Therefore, it is possible to reduce the cost by installing the receiver on the satellite rather than installing many receiving stations on the ground, and it is expected that the cost of the communication service will be reduced and the communication area will be expanded quickly. In addition, it will be possible to acquire information from the ocean, where it is difficult to install a receiving station on the ground, and it will be possible to provide new services.

Japanese Unexamined Patent Publication No. 2019-193306

An object of the present disclosure is to provide a communication device and a communication method that operate as a satellite receiving station that orbits the earth in a predetermined orbit and receives a frame from a terminal on the ground, and a communication system consisting of a terminal on the ground and a satellite receiving station. To provide.

The first aspect of the present disclosure is to orbit the earth in a predetermined orbit and operate as one of the satellite receiving stations that receive frames from terminals on the ground.
A receiving unit that receives and processes frames from the terminal,
Based on the frame reception information at the time of receiving a frame from the terminal, the frame transmission interval of the terminal, and the positional relationship of the surrounding satellite receiving stations, a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal is determined. Judgment unit and
It is a communication device provided with.

The frame reception information includes the frequency error estimation result and the propagation delay estimation result at the time of frame reception. Alternatively, the frame reception information includes the position information of the terminal.

Further, the communication device according to the first aspect exchanges frame reception information with surrounding satellite receiving stations. In this case, the determination unit further determines a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal based on the frame reception information from the surrounding satellite receiving stations.

The communication device according to the first aspect notifies the peripheral satellite receiving stations of the information of the terminals added to the receiving target terminal list based on the frame reception information from the surrounding satellite receiving stations. Further, the communication device according to the first aspect deletes the information of the corresponding terminal from the reception target terminal list of its own station based on the notification from the surrounding satellite receiving stations.

The communication device according to the first aspect notifies the peripheral satellite receiving stations that the determination unit has determined to be suitable for receiving the next frame transmitted from the terminal, and also notifies the reception target terminal registration. The terminal that notified the reception target terminal registration to the nearby satellite receiving stations is excluded from the reception target of the own station. Further, the communication device according to the first aspect targets the terminal to which the reception target terminal registration is notified from the surrounding satellite receiving stations as the reception target of the own station.

When the frame reception information includes the frame transmission interval notified from the terminal, the determination unit predicts the reception of the next frame transmitted from the terminal based on the frame transmission interval and the frequency error estimation result at the time of frame reception. The time is estimated, and a satellite receiving station suitable for receiving the next frame transmitted by the terminal is determined based on the estimated reception time of the frame and the positional relationship of the surrounding satellite receiving stations.

The second aspect of the present disclosure is a communication method that orbits the earth in a predetermined orbit and operates as a satellite receiving station that receives a frame from a terminal on the ground.
A reception step for receiving and processing a frame from the terminal, and
Based on the frame reception information at the time of receiving a frame from the terminal, the frame transmission interval of the terminal, and the positional relationship of the surrounding satellite receiving stations, a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal is determined. Judgment step to do and
It is a communication method having.

The third aspect of the present disclosure consists of a terminal installed on the ground and a plurality of satellite receiving stations each orbiting the earth in a predetermined orbit.
Each of the plurality of satellite receiving stations is based on a receiving unit that receives and processes a frame from the terminal, frame reception information at the time of receiving a frame from the terminal, a frame transmission interval of the terminal, and a positional relationship of surrounding satellite receiving stations. The terminal is provided with a determination unit for determining a satellite receiving station suitable for receiving the next frame to be transmitted.
It is a communication system.

However, the "system" here means a logical assembly of a plurality of devices (or functional modules that realize a specific function), and each device or functional module is in a single housing. It does not matter whether or not it is.

According to the present disclosure, a communication device and a communication method that operates as a satellite receiving station, efficiently acquires information on radio resources of a terminal on the ground, suppresses unnecessary reception and demodulation processing, and receives a frame from the terminal. Further, it is possible to provide a communication system including a terminal on the ground and a satellite receiving station that suppresses unnecessary reception and demodulation processing and receives a frame from the terminal.

It should be noted that the effects described in the present specification are merely examples, and the effects brought about by the present disclosure are not limited thereto. In addition to the above effects, the present disclosure may have additional effects.

Still other objectives, features and advantages of the present disclosure will be clarified by more detailed description based on the embodiments described below and the accompanying drawings.

FIG. 1 is a diagram showing a configuration example of an LPWA wireless communication system. FIG. 2 is a diagram showing an example of a communication sequence between a terminal and a receiving station. FIG. 3 is a diagram showing a functional configuration example of the terminal 100. FIG. 4 is a diagram showing a functional configuration example of the receiving station 200. FIG. 5 is a diagram showing a configuration example of the frame. FIG. 6 is a diagram showing a method of generating a radio resource, preamble and synchronization information, and a scramble pattern used for frame transmission. FIG. 7 is a diagram showing a configuration example of an LPWA wireless communication system using a satellite receiving station. FIG. 8 is a diagram showing an example of a communication sequence between a terminal and a satellite receiving station. FIG. 9 is a diagram showing an example of a communication sequence (first embodiment) between a terminal and a satellite receiving station. FIG. 10 is a diagram showing a functional configuration example of the satellite receiving station 1000. FIG. 11 is a diagram showing a frame configuration example (first embodiment) of the data portion of the frame reception information frame. FIG. 12 is a flowchart showing the processing operation performed by the terminal. FIG. 13 is a flowchart showing a processing procedure (first embodiment) for the satellite receiving station to receive the notification frame. FIG. 14 is a flowchart showing a processing procedure (first embodiment) for the satellite receiving station to receive a data frame. FIG. 15 is a flowchart showing a processing procedure (first embodiment) for the satellite receiving station to receive a frame reception information frame. FIG. 16 is a diagram showing an example of time change of frequency error and propagation delay when the altitude of the satellite is 600 km and the frequency is 2 GHz. FIG. 17 is a diagram showing a frame configuration example (second embodiment) of the data portion of the frame reception information frame. FIG. 18 is a flowchart showing a processing procedure (second embodiment) for the satellite receiving station to receive the frame reception information frame. FIG. 19 is a diagram showing an example of a communication sequence between a terminal and a satellite receiving station (third embodiment). FIG. 20 is a diagram showing a frame configuration example of the data portion of the reception target terminal list registration notification frame. FIG. 21 is a flowchart showing a processing procedure (third embodiment) for the satellite receiving station to receive the frame reception information frame. FIG. 22 is a flowchart showing a processing procedure for the satellite receiving station to receive the reception target terminal list registration notification frame. FIG. 23 is a diagram showing an example of a communication sequence between a terminal and a satellite receiving station (fourth embodiment). FIG. 24 is a diagram showing a frame configuration example (fourth embodiment) of the data portion of the frame reception information frame. FIG. 25A is a flowchart showing a processing procedure (fourth embodiment) for the satellite receiving station to receive the frame reception information frame. FIG. 25B is a flowchart showing a processing procedure (fourth embodiment) for the satellite receiving station to receive the frame reception information frame. FIG. 26 is a diagram showing an example of an adjacent satellite receiving station information list held by the satellite receiving station. FIG. 27 is a diagram showing an example of a communication sequence between a terminal and a satellite receiving station (fifth embodiment). FIG. 28 is a diagram showing a frame configuration example of the data portion of the reception target terminal registration frame. FIG. 29 is a flowchart showing a processing procedure (fifth embodiment) for the satellite receiving station to receive the notification frame. FIG. 30 is a flowchart showing a processing procedure (fifth embodiment) for the satellite receiving station to receive a data frame. FIG. 31 is a flowchart showing a processing procedure for the satellite receiving station to receive the reception target terminal list registration frame. FIG. 32 is a diagram showing an example of a communication sequence between a terminal and a receiving station in a system in which the terminal can arbitrarily transmit a data frame. FIG. 33 is a diagram showing a configuration example (sixth embodiment) of an LPWA wireless communication system using a satellite receiving station. FIG. 34 is a diagram showing an example of a communication sequence between a terminal and a satellite receiving station (sixth embodiment). FIG. 35 is a diagram showing a functional configuration example of the satellite receiving station 3500. FIG. 36 is a diagram showing a configuration example of a data frame. FIG. 37 is a diagram showing a frame configuration example of the data portion of the reception target radio resource information notification frame. FIG. 38 is a flowchart showing the processing operation performed by the terminal. FIG. 39 is a flowchart showing a processing operation for the satellite receiving station to receive the initial data frame. FIG. 40 is a flowchart showing a processing procedure for the satellite receiving station to receive a normal data frame. FIG. 41 is a flowchart showing a processing procedure for the satellite receiving station to receive the reception target radio resource information notification frame.

Hereinafter, this disclosure will be described in the following order with reference to the drawings.

A. Prerequisite system B. System configuration using satellite receiver C. First Example C-1. Communication sequence example C-2. Device configuration C-3. Frame configuration C-4. Terminal processing operation C-5. Processing operation of satellite receiving station D. Second Example D-1. Frame configuration example D-2. Frame reception information Frame reception operation E. Third Example E-1. Communication sequence example E-2. Frame configuration example E-3. Processing operation of satellite receiving station F. Fourth Example F-1. Communication sequence example F-2. Frame configuration example F-3. Adjacent satellite receiving station information list G. Fifth Example G-1. Communication sequence example G-2. Frame configuration example G-3. Processing operation of satellite receiving station H. Effect I. Sixth Example I-1. System configuration I-2. Communication sequence example I-3. Device configuration I-4. Frame configuration example I-5. Terminal processing operation I-6. Processing operation of satellite receiving station I-7. effect

A. In the presupposed system wireless communication system, in order to demodulate the data transmitted by the terminal, the receiving station has information necessary for demodulation such as modulation method, modulation rate, code, and encryption key, and wireless resources used for data transmission. It is necessary to know (time / frequency) for each terminal.

In a wireless communication system capable of bidirectional communication such as LTE (Long Demodulation), the receiving station transmits data to the terminal by performing signaling to exchange necessary information between the terminal and the receiving station before data transmission. It is possible to specify the radio resource (time / frequency) to be used, and then perform demodulation using the modulation method and modulation rate stored in the data transmitted by the specified radio resource (time / frequency). ..

On the other hand, in LPWA, which is a wireless communication method for IoT, it is not desirable to perform signaling from the viewpoint of the power consumption of the terminal. Further, when only one-way communication from the terminal to the receiving station is supported, signaling is not established. Therefore, in the LPWA wireless communication system, a method of grasping the wireless resource used by the terminal for data transmission on the receiving station side will be considered.

FIG. 1 schematically shows a configuration example of an LPWA wireless communication system. In the example shown in the figure, the system is composed of a receiving station and a plurality of terminals. The terminal is a transmitter that periodically transmits information sensed by a built-in sensor or the like. The receiving station receives the data transmitted by the terminal and performs demodulation processing. In addition, the receiving station transmits the demodulation result (user data) to the application server (not shown) on the cloud as needed. In the wireless communication system shown in FIG. 1, it is assumed that the time is synchronized in the system (between the receiving station and each terminal). It is conceivable to use GPS information as a method of time synchronization.

FIG. 2 shows an example of a communication sequence between a terminal and a receiving station in the system shown in FIG.

First, the terminal transmits a notification frame in order to notify its own ID (SEQ201). For the transmission of the notification frame, a radio resource (time / frequency) randomly selected from the radio resources (time / frequency) allocated in advance for the notification frame transmission in the system is used.

The receiving station executes the reception and demodulation processing of the notification frame for the radio resource for transmitting the notification frame (SEQ202). Then, when the demodulation process is successful, the receiving station registers the ID acquired from the notification frame in the reception target terminal list (SEQ203).

The terminal calculates the radio resource (time / frequency) for transmitting the data frame even using its own ID and the code required for data frame generation based on the rules (described later) determined in advance in the system. Generate and transmit a data frame (SEQ204).

Here, it is assumed that the time from notification frame transmission to data frame transmission is sufficiently short, and the next data frame to be transmitted can be received by the same satellite receiving station.

The receiving station uses the ID registered in the list of terminals to be received, and based on the same rules as the terminal, the receiving station uses the radio resource (time / frequency) and the data frame from which the terminal transmits the data frame from the terminal ID. The code required for demodulation is calculated, and the data frame is received and demodulated (SEQ205). In addition, the receiving station transmits the demodulation result (user data) to the application server (not shown) on the cloud as needed.

FIG. 3 shows a functional configuration example of a communication device 100 (hereinafter referred to as a terminal 100) that operates as a terminal in the system shown in FIG. The illustrated terminal 100 includes a wireless communication unit 101, a wireless control unit 102, a frame generation unit 103, a sensor 104, a wireless resource determination unit 105, and a storage unit 106. The functional configuration of the terminal 100 may be the same regardless of whether the receiving station is a ground station or a satellite receiving station.

The wireless communication unit 101 transmits a wireless signal. The wireless communication unit 101 converts the frame generated by the frame generation unit 103 into a wireless signal and transmits it under the control of the wireless control unit 102.

The wireless control unit 102 controls the wireless communication unit 101 so as to transmit a frame at the transmission time and transmission frequency obtained from the wireless resource determination unit 105.

The frame generation unit 103 generates a frame to be transmitted by the terminal 100. The frame generation unit 103 acquires the preamble, synchronization information, and scramble pattern necessary for frame generation from the radio resource determination unit 105. Further, the frame generation unit 103 describes, for example, the sensor information acquired by the sensor unit 104 in the payload of the frame.

The sensor 104 is a sensor that acquires external or internal information of the terminal 100, for example, a temperature sensor or an acceleration sensor.

The radio resource determination unit 105 uses the ID and initial value of the terminal 100 itself obtained from the storage unit 106 to transmit a radio resource (time / frequency) and a preamble required for frame generation necessary for frame generation. Generate synchronization information and scramble pattern.

The storage unit 106 holds the ID and initial value of the terminal 100 itself, which is information necessary for determining the wireless resource. Of course, the storage unit 106 may hold other information.

FIG. 4 shows a functional configuration example of a communication device 200 (hereinafter referred to as a receiving station 200) that operates as a receiving station in the system shown in FIG. The illustrated receiving station 200 includes a radio communication unit 201, a radio control unit 202, a frame detection / demodulation unit 203, a radio resource determination unit 204, and a storage unit 205. The illustrated receiving station 200 assumes a ground station installed on the ground.

The wireless communication unit 201 receives the wireless signal. The wireless communication unit 201 receives radio waves under the control of the wireless control unit 202, converts them into radio signals, and passes them to the frame detection / demodulation unit 203.

The radio control unit 202 controls the radio communication unit 201 so that the frame is received at the reception time and reception frequency obtained from the radio resource determination unit 204.

The frame detection / demodulation unit 203 detects a frame from the received signal and demodulates it. Specifically, the frame detection / demodulation unit 203 generates a known pattern from the preamble, synchronization information, and scramble pattern acquired from the radio resource determination unit 204, calculates the correlation value between the received signal and the known pattern, and correlates. When the value exceeds a certain value, it is determined that the frame has been detected. Then, when the frame detection / demodulation unit 203 succeeds in frame detection, the signal of the portion corresponding to the frame is taken out from the received signal, scrambled, and then the payload is taken out, and the error correction code decoding process and CRC are performed. (CyclicRedundancy Code) is used for error detection. When the frame detection / demodulation unit 203 succeeds in demodulating the frame, the frame detection / demodulation unit 203 notifies the upper layer (not shown) of the demodulated data.

The radio resource determination unit 204 uses the ID and initial value of the terminal 100 obtained from the storage unit 205 to transmit a radio resource (time / frequency) for which the terminal 100 transmits a frame, a preamble required for frame demodulation, synchronization information, and the like. And generate a scramble pattern.

The storage unit 205 holds the ID and initial value of the terminal 100, which is information necessary for determining the wireless resource. Further, the storage unit 205 holds a reception target terminal list holding the ID of the terminal 100 to be received by the reception station 200.

FIG. 5 shows a configuration example of a frame used in the system shown in FIG. The frame contains ID, DATA, and CRC fields. It is assumed that both the notification frame and the data frame transmitted from the terminal have the frame configuration shown in FIG.

In the ID field, an ID which is a unique identifier of the terminal 100 which is the transmission source is stored. Transmission data is stored in the DATA field. In the case of a data frame, data acquired from the sensor 104 or the like is stored. In the case of a notification frame, the transmission interval from the notification frame transmission to the data frame transmission, the transmission interval of the data frame transmitted periodically, and the like are stored. In the CRC field, the CRC value calculated for the information stored in the ID field and the DATA field is stored. On the receiving side, the demodulation success determination is performed using the CRC value.

For the series in which the above ID, DATA, and CRC are concatenated, error correction (Forward Error Correction: FEC) coding and order rearrangement (interleave) are performed to generate a payload. Furthermore, a frame is generated by concatenating the preamble, which is a known pattern used for frame detection and synchronization acquisition, and synchronization information at the beginning of the payload, and then taking an exclusive OR (XOR) with the scramble pattern for each bit. Or.

The radio resources (time / frequency) used for frame transmission, preamble and synchronization information required for frame generation, and the scramble pattern generation method will be described with reference to FIG.

In the system, the radio resources (time / frequency) used for frame transmission, the preamble and synchronization information required for frame generation, and the rules 1 to 4 for determining the scramble pattern generation method are predetermined. .. The time (Time) used for frame transmission is determined by inputting two initial values Seed (T) -1 and Seed (T) -2 for time calculation in Rule 1. The frequency (Freq) used for frame transmission is determined by inputting two initial values Seed (F) -1 and Seed (F) -2 for frequency calculation in Rule 2. The preamble / synchronization information (Preamble / Sync) is determined by inputting two initial values Seed (P) -1 and Seed (P) -2 for calculating the preamble and synchronization information in Rule 3. The scramble pattern is determined by inputting two initial values Seed (S) -1 and Seed (S) -2 for the scramble pattern in Rule 4.

Each initial value is determined in advance in the system, and is held in the storage unit 106 in the terminal 100 and the storage unit 205 in the receiving station 200, respectively. At the time of data frame transmission, the terminal of the data frame source is set to the second initial value (Seed (T) -2, Seed (F) -2, Seed (P) -2, Seed (S) -2). Enter IDs that are 100 unique identifiers. On the other hand, when the notification frame is transmitted, the second initial value (Seed (T) -2, Seed (F) -2, Seed (P) -2, Seed (S) -2) is set in advance for the notification frame. Randomly selected from several assigned initial values and entered.

By using this method, the radio resource (time / frequency) used for frame transmission and the information required for frame demodulation can be obtained only by notifying the terminal ID from the terminal 100 to the receiving station 200.

B. System Configuration Using Satellite Receiving Station FIG. 7 schematically shows a configuration example of an LPWA wireless communication system using a satellite receiving station. In the example shown in the figure, a plurality of receiving stations installed on the ground (hereinafter referred to as "ground stations") and a plurality of satellite receiving stations orbiting the earth (hereinafter, also simply referred to as "satellite receiving stations"). And, it is composed of innumerable terminals scattered on the ground. In the system, it is assumed that all terminals and receiving stations are time-synchronized. It is conceivable to use GPS information as a method of time synchronization. In addition, each satellite receiving station is close to the polar orbit that passes over the sky near the pole, the angle of the light from the sun incident on the orbital plane of the satellite is the same, and the sun that always passes through the equator at the same local time. It orbits the earth in a synchronized orbit.

The terminal is a transmitter that periodically transmits information sensed by the on-board sensor or the like. The satellite receiving station receives the data transmitted by the terminal and performs demodulation processing. Further, the satellite receiving station transmits the demodulation result (user data) to the application server (not shown) on the cloud as needed. In addition, the satellite receiving station enables inter-satellite communication. The communication method between satellite receiving stations is not limited, but it is desirable to use constant connection and high-speed communication. A ground station is a transceiver that communicates with a satellite receiver. The communication method between the satellite receiving station and the ground station is not limited, but high-speed communication is desirable.

In the case of a terrestrial receiving station, if the terminal is a stationary terminal or the movement range is narrow, the receiving station that can receive the data (radio wave) transmitted by the terminal is always the same. Therefore, there is no problem if the terminal transmits the notification frame at a low frequency of about once every few days when the power is turned on and thereafter.

On the other hand, low earth orbit satellites continue to move in orbit at a speed of several kilometers per second, so the receiving station that can receive the data transmitted by the terminal is not fixed. For example, if a terminal is receivable by the satellite receiver 701 when it transmits a notification frame, the satellite receiver 701 will be in the receivable range 711 of the satellite receiver 701 where the terminal is located. The data frame transmitted by the terminal can be received and demodulated. On the other hand, when time elapses and the place where the terminal is located deviates from the receivable range 711 of the satellite receiving station 701 and becomes the receivable range 712 of the subsequent satellite receiving station 702 in the same satellite orbit, the satellite The receiving station 701 cannot receive and demodulate the data frame transmitted by the terminal.

However, in the example shown in FIG. 7, it is assumed that the network design is such that the receivable range 711 and the receivable range 712 of the satellite receiving station 701 and the satellite receiving station 702 adjacent to each other in the satellite orbit do not overlap. The satellite receiving station 701 and the satellite receiving station 702 orbit the same orbit, but may orbit adjacent to each other.

FIG. 8 shows an example of a communication sequence between the satellite receiving station 701 and the satellite receiving station 702 and the terminal 801 adjacent to each other in the satellite orbit. Since the satellite receiving station 701 and the satellite receiving station 702 continue to move in the satellite orbit at a speed of several km per second, the time zone where the terminal 801 is located is the receivable range 711 of the satellite receiving station 701. And, there is a time zone that deviates from the receivable range 711 of the satellite receiving station 701 and becomes the receivable range 712 of the satellite receiving station 702.

First, the terminal 801 transmits (broadcasts) a notification frame in order to notify its own ID (SEQ801). For the transmission of the notification frame, the radio resource (time / frequency) allocated in advance for the notification frame transmission in the system is used. At this point, the terminal 801 is in the receivable range 711 of the satellite receiving station 701. Therefore, the satellite receiving station 701 executes the reception and demodulation processing of the notification frame for the radio resource for transmitting the notification frame (SEQ811), and registers the ID acquired from the notification frame in the reception target terminal list (SEQ812). ). On the other hand, since the notification frame from the terminal 801 does not reach the satellite receiving station 702, the satellite receiving station 702 does not register the ID of the terminal 801 in the reception target terminal list.

Next, the terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system. A data frame is generated and transmitted (broadcast) (SEQ802).

The satellite receiving station 701 uses the ID registered in the reception target terminal list, and is a radio resource (time / frequency) at which the terminal 801 transmits a data frame from the terminal ID based on the same rules 1 to 4 as the terminal 801. ) And the code required for demodulation of the data frame is calculated, and the data frame is received and demodulated (SEQ813).

Further, the terminal 801 calculates the radio resource (time / frequency) for transmitting the next data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system. Then, the next data frame is generated and transmitted (broadcast) (SEQ803).

The satellite receiving station 701 uses the ID registered in the reception target terminal list, and is a radio resource (time / frequency) at which the terminal 801 transmits a data frame from the terminal ID based on the same rules 1 to 4 as the terminal 801. ) And the code required for demodulation of the data frame are calculated, and the reception and demodulation processing of the data frame is attempted (SEQ814). However, since the location where the terminal 801 is located is out of the receivable range 711 and is in the receivable range 712 of the satellite receiving station 702, the demodulation process of the data frame from the terminal 801 fails. Further, the data frame from the terminal 801 reaches the satellite receiving station 702, but since the satellite receiving station 702 does not register the ID of the terminal 801 in the reception target terminal list, the data frame reception / demodulation processing from the terminal 801 is performed. Do not do.

In order to avoid the situation where no satellite receiving station can receive the data frame of the terminal due to the movement of each satellite receiving station in the satellite orbit as shown in FIG. 8, the terminal transmits the notification frame with high frequency. However, it is not desirable from the viewpoint of the power consumption of the terminal and the utilization efficiency of wireless resources. Further, it is not desirable from the viewpoint of resource utilization efficiency of the satellite receiving station to execute the reception / demodulation processing on the terminal outside the receivable area of the satellite receiving station.

Therefore, in the present disclosure, by considering that the satellite receiving station moves in the satellite orbit, even if the terminal does not transmit the notification frame frequently, the place where the terminal is located when the terminal transmits the data frame is determined. We propose a method in which the satellite receiving station within the receivable range targets the terminal.

C. First Example As a first embodiment, in the system configuration as shown in FIG. 7, a satellite that shares frame reception information among a plurality of satellite receiving stations and sets a place where a terminal is located as a receivable range. The method in which the receiving station targets the terminal will be described.

C-1. Example of Communication Sequence FIG. 9 shows an example of a communication sequence between the satellite receiving station 701 and the satellite receiving station 702 and the terminal 801 when the method according to the present disclosure is applied. Since the satellite receiving station 701 and the satellite receiving station 702 continue to move in the satellite orbit at a speed of several km per second, the time zone where the terminal 801 is located is the receivable range 711 of the satellite receiving station 701. And, there is a time zone that deviates from the receivable range 711 of the satellite receiving station 701 and becomes the receivable range 712 of the satellite receiving station 702.

First, the terminal 801 transmits (broadcasts) a notification frame in order to notify its own ID (SEQ901). The terminal 801 uses a radio resource (time / frequency) previously allocated for notification frame transmission in the system for transmission of the notification frame.

At this point, the terminal 801 is in the receivable range 711 of the satellite receiving station 701. Therefore, the satellite receiving station 701 executes the reception and demodulation processing of the notification frame for the radio resource for transmitting the notification frame (SEQ911), and registers the ID acquired from the notification frame in the reception target terminal list (SE912). ).

Then, the satellite receiving station 701 transmits the frame reception information regarding the notification frame received from the terminal 801 to the satellite receiving station 702 located following the same satellite orbit (SEQ913). The frame reception information includes the terminal ID of the transmission source of the notification frame, the data transmission interval, the frequency error estimation result and the propagation delay estimation result measured at the time of receiving the notification frame. The processing procedure for the satellite receiving station to receive the notification frame will be described later (see FIG. 13).

On the other hand, since the notification frame from the terminal 801 does not reach the satellite receiving station 702, the satellite receiving station 702 does not register the ID of the terminal 801 in the reception target terminal list. Further, the satellite receiving station 702 determines whether or not the terminal 801 should be registered in its own reception target terminal list based on the frame reception information received from the satellite receiving station 701 located in front of the same satellite orbit (). SEQ921). The processing procedure for the satellite receiving station to receive the frame reception information frame and the specific determination conditions will be described later (see FIG. 15). In the communication sequence example shown in FIG. 9, since the location where the terminal 801 is located is still outside the receivable range 712 at the timing when the terminal 801 transmits the next data frame, the determination condition is not satisfied. The receiving station 702 does not register the terminal 801 in the receiving target terminal list.

Next, the terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system. A data frame is generated and transmitted (broadcast) (SEQ902).

The satellite receiving station 701 uses the ID registered in the reception target terminal list, and is a radio resource (time / frequency) at which the terminal 801 transmits a data frame from the terminal ID based on the same rules 1 to 4 as the terminal 801. ) And the code required for demodulation of the data frame is calculated, and the data frame is received and demodulated (SEQ 914). Then, the satellite receiving station 701 transmits the frame reception information regarding the data frame received from the terminal 801 to the satellite receiving station 702 located following the same satellite orbit (SEQ915). The processing procedure for the satellite receiving station to receive the data frame will be described later (see FIG. 14).

The satellite receiving station 702 determines whether or not the terminal 801 should be registered in its own reception target terminal list based on the frame reception information received from the satellite receiving station 701 located in front of the same satellite orbit (SEQ922). .. Here, since the location where the terminal 801 is located is within the receivable range 712 at the transmission timing of the next data frame and other determination conditions are satisfied, the satellite receiving station 702 registers the terminal 801 in the reception target terminal list.

Further, the terminal 801 calculates the radio resource (time / frequency) for transmitting the next data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system. Then, the next data frame is generated and transmitted (broadcast) (SEQ903).

The satellite receiving station 701 uses the ID registered in the reception target terminal list, and is a radio resource (time / frequency) at which the terminal 801 transmits a data frame from the terminal ID based on the same rules 1 to 4 as the terminal 801. ) And the code required for demodulation of the data frame are calculated, and the reception and demodulation processing of the data frame is attempted (SEQ915). However, since the location where the terminal 801 is located is out of the receivable range 711 and is in the receivable range 712 of the satellite receiving station 702, the demodulation process of the data frame from the terminal 801 fails.

Also, the data frame from the terminal 801 reaches the satellite receiving station 702. Since the satellite receiving station 702 registers the ID of the terminal 801 in its own reception target terminal list based on the frame reception information received from the terminal 801, the terminal ID is based on the same rules 1 to 4 as the terminal 801. The terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame and the code required for demodulating the data frame, and attempts to receive and demolish the data frame. Since the location where the terminal 801 is located is within the receivable range 712, the satellite receiving station 702 succeeds in demodulating the data frame from the terminal 801 (SEQ 924).

C-2. Even in a system that shares device configuration frame reception information, the terminal configuration may be the same as in FIG. 3, and therefore, the description of the terminal configuration will be omitted in this section C.

FIG. 10 shows an example of a functional configuration of the satellite receiving station 1000 in a system that shares frame reception information. The satellite receiving station 1000 is used by being mounted on a low earth orbit satellite orbiting the earth in any of the satellite orbits shown in FIG. The satellite receiving station 1000 includes an LPWA unit 1200 and an intersatellite communication unit 1300.

The LPWA unit 1200 receives the frame transmitted by the terminal on the ground. The LPWA unit 1200 has the same reference number as that of FIG. 4 for the same components as the receiving station 200 shown in FIG. The LPWA unit 1200 further includes a target terminal determination unit 206. The target terminal determination unit 206 determines whether or not the target terminal should be registered in its own reception target terminal list based on the frame reception information received from the satellite receiving station in front of the same satellite orbit. Further, the frame detection / demodulation unit 203 uses the intersatellite communication unit to obtain the terminal ID of the source of the received notification frame or data frame, the frame transmission interval, the frequency error estimation result and the propagation delay estimation result measured at the time of receiving the notification frame. It is output to the frame generation unit 1303 on the 1300 side.

The intersatellite communication unit 1300 includes a wireless communication unit 1301, a wireless control unit 1302, a frame generation unit 1303, and a frame detection / demodulation unit 1304.

The wireless communication unit 1301 transmits and receives wireless signals. The wireless communication unit 1301 receives radio waves under the control of the wireless control unit 1302, converts them into radio signals, and passes them to the frame detection / demodulation unit 1304. Further, the wireless communication unit 1301 converts the frame generated by the frame generation unit 1303 into a wireless signal and transmits it under the control of the wireless control unit 1302.

The wireless control unit 1302 controls the wireless communication unit 1301 so that frames can be transmitted and received between satellite receiving stations.

The frame generation unit 1303 stores the frame reception information acquired from the frame detection / demodulation unit 203 on the LPWA unit 1200 side in the data, and generates a frame according to a predetermined format.

The frame detection / demodulation unit 1304 detects and demodulates a frame from the received signal of the wireless communication unit 1301. When the frame detection / demodulation unit 1304 succeeds in demodulating the frame, the frame detection / demodulation unit 1304 passes the received data, that is, the frame reception information, to the target terminal determination unit 206.

C-3. Frame Configuration This section describes the frame configuration used in the LPWA wireless communication system according to the present disclosure. However, since the notification frame and the data frame transmitted from the terminal to the satellite receiving station have the same frame configuration as shown in FIG. 5, detailed description thereof will be omitted here.

FIG. 11 shows a frame configuration example of the data part of the frame reception information frame. The format other than the data part shall be according to the communication method used. The frame reception information frame is a frame for notifying a subsequent satellite receiving station in the same satellite orbit of the frame reception information regarding the frame received from the terminal by the satellite receiving station.

In the nSTA field, the number of frame reception information (Frame Rx Info) stored in the data part is stored. The nSTA field is followed by the number of Frame Rx Info fields described in the nSTA field. In each Frame Rx Info field, frame reception information regarding a frame received from each terminal is stored. In the frame configuration example shown in FIG. 11, information indicating the value n is stored in the nSTA field, and n Frame Rx Info fields are stored.

Each Frame Rx Info field includes an ID field, an Ftype field, and Freq. It includes an Error field, a Promotion Delay field, a Data Tx Interval field, and a Next Data Tx Interval field, respectively.

In the ID field, the ID (terminal ID) of the terminal that is the source of the received frame is stored. A value indicating the type of received frame is stored in the Ftype field. Specifically, when the value stored in the Ftype field is 0, a notification frame is indicated, and when it is 1, a data frame is indicated. Freq. The error estimation result of the received frame is stored in the Error field. In the Promotion Delivery field, the propagation delay estimation result of the received frame is stored. The data frame transmission interval is stored in the Data Tx Interval field. The time until the next data frame is transmitted is stored in the Next Data Tx Interval field. The Next Data Tx Interval field is added only when Ftype is 0, that is, when a notification frame is received.

C-4. Processing operation of the terminal FIG. 12 shows the processing operation performed by the terminal in the form of a flowchart.

The terminal first determines whether or not α time has elapsed immediately after the power is turned on or after the previous notification frame is transmitted (step S1201). It is assumed that the transmission interval α of the notification frame is set in advance.

Immediately after the power is turned on or when α time has elapsed since the previous notification frame was transmitted (Yes in step S1201), the terminal executes the notification frame transmission process.

When transmitting a notification frame, the terminal first obtains information such as radio resources (time, frequency) used for transmitting the notification frame, preamble and synchronization information required for frame generation, scramble pattern, and the like, as described in Rules 1 to 4 described above. It is calculated based on (step S1202).

Next, the terminal generates a notification frame using the preamble, synchronization information, and scramble pattern calculated in step S1202 (step S1203).

Next, the terminal determines whether or not the transmission time calculated in step S1202 has been reached (step S1204). Then, when the transmission time of the notification frame arrives (Yes in step S1204), the terminal transmits the notification frame generated in step S1203 using the transmission frequency calculated in step S1202 (step S1205).

On the other hand, if α time has not elapsed since the power was turned on or the previous notification frame was transmitted (No in step S1201), and after the notification frame was transmitted, the terminal has elapsed β time since the previous data frame was transmitted. It is determined whether or not it has been done (step S1206).

When β time has elapsed since the last data frame was transmitted (Yes in step S1206), the terminal uses the radio resource (time / frequency) used to transmit the data frame, the preamble and synchronization information required for frame generation, and the scramble pattern. Information such as is calculated based on the rules 1 to 4 (step S1207).

Next, the terminal generates a data frame using the preamble, synchronization information, and scramble pattern calculated in step S1207 (step S1208).

Next, the terminal determines whether or not the transmission time calculated in step S1207 has been reached (step S1209). Then, when the transmission time arrives (Yes in step S1209), the terminal transmits the data frame generated in step S1208 using the transmission frequency calculated in step S1207 (step S1210).

If β time has not elapsed since the last data frame was transmitted (No in step S1206), and after transmitting the data frame, the process returns to step S1201 and the terminal repeatedly executes the transmission of the notification frame.

C-5. Processing operation of the satellite receiving station In the present disclosure, it is assumed that the satellite receiving station can perform the reception processing of the notification frame, the reception processing of the data frame, and the transmission / reception processing of the frame reception information frame in parallel.

FIG. 13 shows the processing procedure for the satellite receiving station to receive the notification frame in the form of a flowchart.

First, the satellite receiving station refers to the reception target terminal list, and obtains the radio resource (time / frequency) for receiving the notification frame from the registered terminal and the information necessary for demodulating the notification frame in the above-mentioned rules 1 to 4. It is calculated based on (step S1301).

Next, the satellite receiving station determines whether or not the notification frame reception time calculated in step S1301 has been reached (step S1302). When the notification frame reception time arrives (Yes in step S1302), the satellite receiving station detects the notification frame from the corresponding terminal using the preamble and synchronization information calculated in step S1301 (step S1303), and calculates it in step S1301. The received notification frame is demodulated using the scramble pattern (step S1304). Then, the satellite receiving station determines whether or not the demodulation of the notification frame is successful (step S1305).

Here, if the demodulation of the notification frame is successful (Yes in step S1305), the satellite receiving station puts information such as the terminal ID and the data transmission interval stored in the received notification frame into the reception target terminal list. Register (step S1306).

Next, the satellite receiving station has the terminal ID stored in the notification frame, the data transmission interval, the frequency error estimation result and the propagation delay estimation result calculated when the notification frame is detected and demodulated in steps S1303 to S1304, and further. Generates a frame reception information frame using the transmission interval from the notification frame transmission to the data frame transmission (step S1307).

After that, the satellite receiving station transmits a frame reception information frame to a subsequent satellite receiving station in the same satellite orbit (step S1308).

On the other hand, if the demodulation of the notification frame fails (No in step S1305), the satellite receiving station does not register in the reception target terminal list or transmit the frame reception information frame.

In the processing procedure shown in FIG. 13, the satellite receiving station transmits a frame reception information frame each time it receives a notification frame, but the satellite receiving station receives a plurality of notification frames and then collectively receives the frames. Information frames may be transmitted.

FIG. 14 shows the processing procedure for the satellite receiving station to receive the data frame in the form of a flowchart. However, it is assumed that the satellite receiving station can execute the data frame reception processing in parallel for each terminal registered in the reception target terminal list.

First, the satellite receiving station acquires the information of the target terminal such as the terminal ID from the reception target terminal list (step S1401), and performs the radio resource (time / frequency) for receiving the data frame from the target terminal and the data frame demodulation. The required preamble, synchronization information, and scramble pattern are calculated based on the above-mentioned rules 1 to 4 (step S1402).

Next, the satellite receiving station determines whether or not the data frame reception time calculated in step S1402 has been reached (step S1403). When the data frame reception time arrives (Yes in step S1403), the satellite receiving station detects the data frame from the corresponding terminal using the preamble and synchronization information calculated in step S1402 (step S1404), and calculates it in step S1402. The received data frame is demodulated using the scramble pattern (step S1405). Then, the satellite receiving station determines whether or not the demodulation of the data frame is successful (step S1406).

Here, if the demodulation of the data frame is successful (Yes in step S1406), the satellite receiving station estimates the data transmission interval and the frequency error calculated when the data frame is detected and demodulated in steps S1404 to S1405. A frame reception information frame is generated using the result and the propagation delay estimation result (step S1407).

After that, the satellite receiving station transmits a frame reception information frame to a subsequent satellite receiving station in the same satellite orbit (step S1408).

On the other hand, if the demodulation of the data frame fails (No in step S1406), the satellite receiving station does not transmit the frame reception information frame.

In the processing procedure shown in FIG. 14, the satellite receiving station transmits a frame reception information frame each time a data frame is received, but the satellite receiving station receives a plurality of data frames and then collectively receives the frame. Information frames may be transmitted.

FIG. 15 shows the processing procedure for the satellite receiving station to receive the frame reception information frame in the form of a flowchart.

First, the satellite receiving station determines whether or not the frame reception information frame has been received (step S1501). Then, when the satellite receiving station receives the frame reception information frame (Yes in step S1501), the received frame is demodulated (step S1502), and it is determined whether or not the demodulation processing is successful (step S1503). ..

If the demodulation process of the frame reception information frame is successful (Yes in step S1503), the satellite receiving station acquires an nSTA indicating the number of frame reception information stored in the frame reception information frame (step S1504). , The processing of each subsequent frame reception information (Frame Rx Info) is repeatedly executed for the number of frame reception information.

First, the satellite receiving station estimates the remaining time that can be received by the satellite receiving station having the same notification frame or data frame from the frequency error estimation result (Freq.Eror) and the propagation delay estimation result (Propagation Delivery) (step S1505). ).

Next, based on the receivable remaining time estimated in step S1505 and the data transmission interval, it is determined whether or not the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (step S1506). Here, for the data transmission interval, the value stored in the Next Data Tx Interval field is used when Ftype is 0, that is, the received frame is a notification frame, and when Ftype is 1, that is, the received frame is a data frame. The value stored in the Data Tx Interval field is used for.

Then, if the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (Yes in step S1506), the satellite receiving station returns to step S1505 and receives the next frame reception information (Yes). The process of Frame Rx Info) is repeatedly executed.

On the other hand, if the next data frame transmitted from the corresponding terminal cannot be received by the same satellite receiving station (No in step S1506), the satellite receiving station is stored in the frame receiving information (Frame Rx Info). After registering the terminal ID and the data transmission interval in its own reception target terminal list (step S1507), the process returns to step S1505 and the processing of the next frame reception information (Frame Rx Info) is repeatedly executed.

The frequency error estimation and propagation delay estimation in step S1505 in the flowchart shown in FIG. 15 are supplemented. FIG. 16 shows an example of the time change of the frequency error and the propagation delay when the altitude of the satellite is 600 km and the frequency is 2 GHz. FIG. 16 shows an example in which a satellite passes overhead of a terminal, and it is assumed that the satellite receiving station can receive one terminal for 6 minutes from 0 to 6 minutes. For the calculation of the frequency error, the model described in 3GPP TR 38.811 V15.1.0 (Non-Patent Document 1) was referred to. In the example shown in FIG. 16, the satellite receiving station is just above the terminal at the third minute, the propagation delay is minimized, and the sign of the frequency error is inverted.

By comparing the frequency error estimation result and the propagation delay estimation result of the received frame from the terminal with the chart of FIG. 16, it is possible to determine which time corresponds to the 6 minutes in which the frame from the terminal can be received. .. Further, when the satellite receiving station moves over the terminal in one direction at a predetermined speed, the relative positional relationship between the terminal corresponding to the determined time and the satellite receiving station can be estimated.

For example, if the data transmission interval is 3 minutes, the frequency error estimation result notified in the frame reception information frame is 30 kHz, and the propagation delay estimation result is 2.5 milliseconds, it corresponds to the second minute of the receivable 6 minutes. .. Therefore, since the next data frame corresponds to the 5th minute of the 6 minutes that can be received, it can be received by the same satellite receiving station.

On the other hand, when the data transmission interval is 3 minutes, the frequency error estimation result notified in the frame reception information frame is -30 kHz, and the propagation delay estimation result is 2.5 milliseconds, the 5th minute out of the receivable 6 minutes. Equivalent to. Therefore, since the next data frame corresponds to the time when the receivable 6 minutes have elapsed, it cannot be received by the same receiving station. Considering that the satellite receiving station moves in one direction in the satellite orbit in this way, the remaining time that can be received by the satellite receiving station that received the frame from the terminal is estimated by combining the frequency error and the propagation delay. It is possible to do.

In short, in the method according to the first embodiment, each satellite receiving station shares the frame reception information including the frequency error estimation result and the propagation delay estimation result of the frame received from the terminal, and the frequency error estimation result and the propagation delay estimation. Based on the result, the frame transmission interval, and the positional relationship of the adjacent satellite receiving stations, it is determined whether or not the next data frame transmitted from the corresponding terminal can be received by the same satellite receiving station.

According to the first embodiment, the satellite receiving station transmits the frame reception information to the succeeding satellite receiving station in the same orbit, so that the terminal can then send the data even if the terminal does not frequently transmit the notification frame. When transmitting a frame, it is possible to enable a satellite receiving station whose receivable range is the location where the terminal is located to receive and demodulate the data frame from the terminal.

D. Second Example In the above first embodiment, the frequency error estimation result and the propagation delay estimation result of the frame received from the terminal are notified between the satellite receiving stations, and the data frame transmitted from the corresponding terminal is the same. The method of determining whether or not reception is possible at the satellite receiving station has been explained. On the other hand, in the second embodiment, when the terminal is equipped with a GPS receiver, the position coordinates (latitude / longitude) of the terminal are notified between the satellite receiving stations, so that the terminal is transmitted. A method of determining whether or not a data frame can be received by the same satellite receiving station will be described.

D-1. Frame configuration example FIG. 17 shows a frame configuration example of a data portion of a frame reception information frame when notifying the position coordinates of a terminal. The format other than the data part shall be according to the communication method used. As described above, the frame reception information frame is a frame that notifies the subsequent satellite receiving station in the same satellite orbit of the frame reception information regarding the frame received from the terminal by the satellite receiving station.

In the nSTA field, the number of frame reception information (Frame Rx Info) stored in the data part is stored. The nSTA field is followed by the number of Frame Rx Info fields described in the nSTA field. In each Frame Rx Info field, frame reception information regarding a frame received from each terminal is stored. In the frame configuration example shown in FIG. 17, information indicating the value n is stored in the nSTA field, and n Frame Rx Info fields are stored.

Each Frame Rx Info field includes an ID field, an Ftype field, a Longitude field, a Latitude field, a Frame Rx Time field, a Data Tx Interval field, and a Next Data Tx Interval field, respectively.

In the ID field, the ID (terminal ID) of the terminal that is the source of the received frame is stored. A value indicating the type of received frame is stored in the Ftype field. Specifically, when the value stored in the Ftype field is 0, a notification frame is indicated, and when it is 1, a data frame is indicated. The longitude field in which the terminal is located is stored in the Longitude field. The longitude in which the terminal is located is stored in the Latitude field. In the Frame Rx Time field, the time when the frame is received from the terminal is stored. The data frame transmission interval is stored in the Data Tx Interval field. The time until the next data frame is transmitted is stored in the Next Data Tx Interval field. The Next Data Tx Interval field is added only when Ftype is 0, that is, when a notification frame is received.

D-2. Frame reception information frame reception operation FIG. 18 shows a processing procedure for a satellite receiving station to receive a frame reception information frame in the form of a flowchart.

First, the satellite receiving station determines whether or not the frame reception information frame has been received (step S1801). Then, when the satellite receiving station receives the frame reception information frame (Yes in step S1801), the received frame is demodulated (step S1802), and it is determined whether or not the demodulation processing is successful (step S1803). ..

If the demodulation process of the frame reception information frame is successful (Yes in step S1803), the satellite receiving station acquires nSTA indicating the number of frame reception information stored in the frame reception information frame (step S1804). , The processing of each subsequent frame reception information (Frame Rx Info) is repeatedly executed for the number of frame reception information.

First, the remaining time that the notification frame or the data frame can be received by the same satellite receiving station is estimated from the position coordinates of the terminal and the frame reception time from the terminal (step S1805).

Next, based on the receivable remaining time estimated in step S1805 and the data transmission interval, it is determined whether or not the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (step S1806). Here, for the data transmission interval, the value stored in the Next Data Tx Interval field is used when Ftype is 0, that is, the received frame is a notification frame, and when Ftype is 1, that is, the received frame is a data frame. The value stored in the Data Tx Interval field is used for.

Then, if the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (Yes in step S1806), the satellite receiving station returns to step S1805 and returns to the next frame reception information (Yes). The process of Frame Rx Info) is repeatedly executed.

On the other hand, if the next data frame transmitted from the corresponding terminal cannot be received by the same satellite receiving station (No in step S1806), the satellite receiving station is stored in the frame receiving information (Frame Rx Info). After registering the terminal ID and the data transmission interval in its own reception target terminal list (step S1807), the process returns to step S1805, and the processing of the next frame reception information (Frame Rx Info) is repeatedly executed.

Since the satellite receiving station transmits the data received by the LPWA to the ground, it is necessary to communicate with the ground station by satellite communication. Therefore, in general, the satellite receiving station grasps its own position coordinates by GPS or the like.

Also, when constructing a satellite constellation, it holds information on satellite receiving stations that orbit in the same satellite orbit. For example, it is assumed that the satellite has information that it passes through the same point on the ground at intervals of 6 minutes with the satellite in front of the satellite orbit.

Specifically, when the time when the frame reception information frame is received is 12:00, the time when the position information notified by the terminal in the data frame is within the receivable range is 12:05, and the frame reception time is 11:58, the notification frame. Alternatively, the remaining receivable time at the satellite receiving station that received the data frame is 7 minutes. When the data transmission interval is 3 minutes, the next data frame can be received by the same receiving station.

On the other hand, when the time when the frame reception information frame is received is 12:00, the time when the position information notified by the terminal in the data frame is within the receivable range is 12:01, and the frame reception time is 11:59, the notification frame or the data frame. The remaining receivable time at the satellite receiving station that received the message is 2 minutes. If the data transmission interval is 3 minutes, the next data frame cannot be received by the same receiving station.

In this way, considering that the low earth orbit satellite travels in one direction in the satellite orbit and the positional relationship of each satellite receiving station can be grasped by constellation, the position information notified by the terminal and the time when the frame is received are received. From, it is possible to estimate the remaining time that can be received by the receiving station that received the frame.

E. Third Example In the first embodiment (communication sequence example shown in FIG. 9), the satellite receiving station 701 uses the terminal 801 even after the place where the terminal 801 is located has passed its own receivable range 711. It remains registered in its own reception target terminal list, and performs unnecessary reception / demodulation processing on the data frame from the terminal 801. On the other hand, in the third embodiment, a method of preventing the satellite receiving station from performing unnecessary reception / demodulation processing on a terminal that has passed from its own receivable range will be described.

E-1. Communication Sequence Example FIG. 19 shows an example of a communication sequence between the satellite receiving station 701 and the satellite receiving station 702 and the terminal 801 when the method according to the third embodiment is applied. Since the satellite receiving station 701 and the satellite receiving station 702 continue to move in the satellite orbit at a speed of several km per second, the time zone where the terminal 801 is located is the receivable range 711 of the satellite receiving station 701. And, there is a time zone that deviates from the receivable range 711 of the satellite receiving station 701 and becomes the receivable range 712 of the satellite receiving station 702.

First, the terminal 801 transmits (broadcasts) a notification frame in order to notify its own ID (SEQ1901). The terminal 801 uses a radio resource (time / frequency) previously allocated for notification frame transmission in the system for transmission of the notification frame.

At this point, the terminal 801 is in the receivable range 711 of the satellite receiving station 701. Therefore, the satellite receiving station 701 executes the reception and demodulation processing of the notification frame for the radio resource for transmitting the notification frame (SEQ1911), and registers the ID acquired from the notification frame in the reception target terminal list (SE1912). ). Then, the satellite receiving station 701 transmits the frame reception information regarding the notification frame received from the terminal 801 to the satellite receiving station 702 located following the same satellite orbit (SEQ1913). The frame reception information includes the terminal ID of the transmission source of the notification frame, the data transmission interval, the position coordinates of the corresponding terminal, and the reception time of the notification frame. The satellite receiving station 701 performs reception / demodulation of the notification frame and transmission processing of the notification frame according to the processing procedure shown in FIG.

On the other hand, since the notification frame from the terminal 801 does not reach the satellite receiving station 702, the satellite receiving station 702 does not register the ID of the terminal 801 in the reception target terminal list. Further, the satellite receiving station 702 receives and processes the frame reception information frame from the satellite receiving station 701 located in front of the same satellite orbit, and determines whether or not the terminal 801 should be registered in its own reception target terminal list. (SEQ1921). The processing procedure for the satellite receiving station to receive the frame reception information frame will be described later (see FIG. 21). Here, the satellite receiving station 702 determines that the next data frame transmitted from the terminal 801 cannot be received from the receivable remaining time and the data transmission interval estimated based on the frequency error estimation result and the propagation delay estimation result. Judging, the terminal 801 is not registered in its own reception target terminal list.

Next, the terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system. A data frame is generated and transmitted (broadcast) (SEQ1902).

The satellite receiving station 701 uses the ID registered in the reception target terminal list, and is a radio resource (time / frequency) at which the terminal 801 transmits a data frame from the terminal ID based on the same rules 1 to 4 as the terminal 801. ) And the code required for demodulation of the data frame is calculated, and the data frame is received and demodulated (SEQ1914). Then, the satellite receiving station 701 transmits the frame reception information regarding the data frame received from the terminal 801 to the satellite receiving station 702 located following the same satellite orbit (SEQ1915). The satellite receiving station 701 performs reception / demodulation of data frames and transmission processing of notification frames according to the processing procedure shown in FIG.

The satellite receiving station 702 receives and processes the frame reception information frame from the satellite receiving station 701 located in front of the same satellite orbit, and determines whether or not the terminal 801 should be registered in its own reception target terminal list ( SEQ1922). The processing procedure for the satellite receiving station to receive the frame reception information frame will be described later (see FIG. 21). Here, the satellite receiving station 702 receives the data frame to be transmitted next from the terminal 801 at the satellite receiving station 702 from the receivable remaining time and the data transmission interval estimated based on the frequency error estimation result and the propagation delay estimation result. It is determined that it is possible, and the terminal 801 is registered in the reception target terminal list (SEQ1923).

Then, the satellite receiving station 702 transmits a reception target terminal list registration notification frame to the satellite receiving station 701 located in front of the same satellite orbit, and notifies that the terminal 801 is registered in the reception target terminal list. (SEQ1924). When the satellite receiving station 701 receives the reception target terminal list registration notification frame from the satellite receiving station 702, the satellite receiving station 701 deletes the entry of the terminal 801 from its own receiving target terminal list (SEQ1916).

Further, the terminal 801 calculates the radio resource (time / frequency) for transmitting the next data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system. Then, the next data frame is generated and transmitted (broadcast) (SEQ1903).

At this point, the location where the terminal 801 is located is outside the receivable range 711 of the satellite receiving station 701. Since the satellite receiving station 701 has already deleted the terminal 801 from its own list of reception target terminals, it does not perform unnecessary reception / demodulation processing on the data frame from the terminal 801.

Further, since the satellite receiving station 702 registers the ID of the terminal 801 in its own reception target terminal list based on the frame reception information received from the satellite receiving station 701, it is based on the same rules 1 to 4 as the terminal 801. , The terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from the terminal ID and the code required for demodulating the data frame, attempts to receive and demolish the data frame, and succeeds in demolishing (SEQ1925). ).

According to the communication sequence example shown in FIG. 19, the satellite receiving station 701 receives unnecessary reception after the terminal 801 has passed from its own receivable range 711 by the notification from the subsequent satellite receiving station 702 in the same satellite orbit. -It is possible to prevent the demodulation process from being executed.

E-2. Frame configuration example FIG. 20 shows a frame configuration example of the data portion of the reception target terminal list registration notification frame. The format other than the data part shall be according to the communication method used. As shown in FIG. 19, the reception target terminal list registration notification frame sets the terminal into its own reception target terminal list based on the frame reception information received by the satellite receiving station from the satellite receiving station in front of the same satellite orbit. It is a frame to notify that the registration has been made.

In the nSTA field, the number of terminal IDs (STA Rx ID) stored in the data part is stored. The nSTA field is followed by the number of STA ID fields described in the nSTA field. In each STA ID field, information on the terminal ID registered in the reception target terminal list is stored.

E-3. Processing operation of the satellite receiving station FIG. 21 shows a processing procedure for the satellite receiving station to receive a frame reception information frame in the form of a flowchart.

First, the satellite receiving station determines whether or not the frame reception information frame has been received (step S2101). Then, when the satellite receiving station receives the frame reception information frame (Yes in step S2101), the received frame is demodulated (step S2102), and it is determined whether or not the demodulation processing is successful (step S2103). ..

If the demodulation process of the frame reception information frame is successful (Yes in step S2103), the satellite receiving station acquires nSTA indicating the number of frame reception information stored in the frame reception information frame (step S2104). , The processing of each subsequent frame reception information (Frame Rx Info) is repeatedly executed for the number of frame reception information.

First, the remaining time that the notification frame or the data frame can be received by the same satellite receiving station is estimated from the frequency error estimation result (Freq.Eror) and the propagation delay estimation result (Propagation Delivery) (step S2105).

Next, based on the receivable remaining time estimated in step S2105 and the data transmission interval, it is determined whether or not the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (step S2106). Here, for the data transmission interval, the value stored in the Next Data Tx Interval field is used when Ftype is 0, that is, the received frame is a notification frame, and when Ftype is 1, that is, the received frame is a data frame. The value stored in the Data Tx Interval field is used for.

Then, if the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (Yes in step S2106), the satellite receiving station returns to step S2105 and receives the next frame reception information (Yes). The process of Frame Rx Info) is repeatedly executed.

On the other hand, if the next data frame transmitted from the corresponding terminal cannot be received by the same satellite receiving station (No in step S2106), the satellite receiving station is stored in the frame receiving information (Frame Rx Info). After registering the terminal ID and data transmission interval in its own reception target terminal list (step S2107), and then adding the terminal ID of the corresponding terminal to the reception target terminal list registration notification frame (see FIG. 20) (see FIG. 20). Step S2108), returning to step S2105, the processing of the next frame reception information (Frame Rx Info) is repeatedly executed.

When the processing is completed for all the nSTA frame reception information stored in the frame reception information frame received in step S2101, whether or not the satellite receiving station needs to transmit the reception target terminal list registration notification frame. (Step S2109). Then, when it is necessary to transmit the reception target terminal list registration notification frame (Yes in step S2109), the satellite receiving station stores the number of stored reception target terminal list registration IDs in nSTA and receives the reception. The target terminal list registration notification frame is transmitted (step S2110).

FIG. 22 shows a processing procedure for the satellite receiving station to receive the reception target terminal list registration notification frame in the form of a flowchart.

First, the satellite receiving station determines whether or not the reception target terminal list registration notification frame has been received (step S2201). Then, when the satellite receiving station receives the reception target terminal list registration notification frame (Yes in step S2201), the satellite receiving station demodulates the received frame (step S2202) and determines whether or not the demodulation processing is successful (step S2202). Step S2203).

When the satellite receiving station succeeds in demodulating the reception target terminal list registration notification frame (Yes in step S2203), the satellite receiving station outputs nSTA indicating the number of STA ID fields stored in the reception target terminal list registration notification frame. It is acquired (step S2204), and the subsequent processing of each STA ID field is repeatedly executed for the number of nSTAs. In this iterative process, the entry of the terminal ID stored in the reception target terminal list registration notification frame is deleted from its own reception target terminal list (step S2205).

By processing the reception target terminal list registration notification frame according to the processing procedure shown in FIG. 22, the satellite receiving station receives the terminal newly received by the subsequent satellite receiving station in the same satellite orbit. It can be deleted from the target terminal list.

Therefore, according to the communication sequence according to the third embodiment, the satellite receiving station can prevent unnecessary reception / demodulation processing for the terminal that has passed its receivable range.

F. Fourth Example In the first embodiment described above, the next time a terminal to be received by a satellite receiving station transmits a data frame, the place where the terminal is located is on its own or in the same satellite orbit. It is assumed that the range will be within the receivable range of the satellite receiving station in the next orbital order (see, for example, the communication sequence example shown in FIG. 9).

However, if the data transmission interval of a terminal is long, such as several hours, the next time the terminal transmits a data frame, it will be several (two or more) behind in the same satellite orbit from the satellite receiving station that is the target of reception. It is also assumed that it has moved to the receivable range of the satellite receiving station of.

Therefore, in the fourth embodiment, even if the data transmission interval of the terminal is moved to the receivable range of several (two or more) ahead satellite receiving stations in the same satellite orbit, the appropriate satellite is used. The method in which the receiving station can receive the data frame will be described.

F-1. Example of Communication Sequence FIG. 23 shows an example of a communication sequence between the satellite receiving stations 701 to 703 and the terminal 801 when the method according to the fourth embodiment is applied. Since the satellite receiving stations 701 to 703 continue to move in the satellite orbit at a speed of several km per second, the time zone where the terminal 801 is located is in the receivable range 711 of the satellite receiving station 701 and the satellite. Time zone that is out of the receivable range 711 of the receiving station 701 and becomes the receivable range 712 of the satellite receiving station 702, and time that is out of the receivable range 712 of the satellite receiving station 702 and becomes the receivable range 713 of the satellite receiving station 703. There is a band.

The terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system, and the data frame. Is generated and transmitted (broadcast) (SEQ2301).

It is assumed that the terminal 801 is in the receivable range 711 of the satellite receiving station 701, and the satellite receiving station 701 has registered the terminal 801 in its own reception target terminal list. Therefore, the satellite receiving station 701 uses the ID registered in the reception target terminal list, and is a radio resource (time) for which the terminal 801 transmits a data frame from the terminal ID based on the same rules 1 to 4 as the terminal 801. -Frequency) and the code required for demodulation of the data frame are calculated, and the data frame is received and demodulated (SEQ 2311). Here, it is assumed that the satellite receiving station 701 succeeds in receiving and demodulating the data frame.

Then, the satellite receiving station 701 transmits the frame reception information regarding the data frame received from the terminal 801 to the satellite receiving station 702 located following the same satellite orbit (SEQ2312). The frame reception information includes information such as the terminal ID that received the data frame, the frequency error estimation result, the propagation delay estimation result, and the received satellite receiving station ID.

The satellite receiving station 702 receives and processes the frame reception information frame from the satellite receiving station 701 located in front of the same satellite orbit, and determines whether or not the terminal 801 should be registered in its own reception target terminal list ( SEQ2321). Here, the satellite receiving station 702 determines that the next data frame transmitted from the terminal 801 cannot be received from the receivable remaining time and the data transmission interval estimated based on the frequency error estimation result and the propagation delay estimation result. Judging, the terminal 801 is not registered in its own reception target terminal list.

Next, the satellite receiving station 702 determines whether or not this frame receiving information should be transmitted to the satellite receiving station 703 located following the same satellite orbit based on the received frame reception information (SEQ2322). Then, the satellite receiving station 702 transmits the frame reception information to the satellite receiving station 703 based on the determination result (SEQ2323).

The satellite receiving station 703 receives and processes a frame reception information frame from the satellite receiving station 702 located in front of the same satellite orbit, and determines whether or not the terminal 801 should be registered in its own reception target terminal list ( SEQ2331). Here, the satellite receiving station 703 receives the data frame to be transmitted next from the terminal 801 at the satellite receiving station 703 from the receivable remaining time and the data transmission interval estimated based on the frequency error estimation result and the propagation delay estimation result. It is determined that it is possible, and the terminal 801 is registered in the reception target terminal list (SEQ2332).

Then, the satellite receiving station 703 transmits a reception target terminal list registration notification frame to the satellite receiving station 701 that has received the data frame from the terminal 801 to notify that the terminal 801 has been registered in the reception target terminal list. (SEQ2333). When the satellite receiving station 701 receives the reception target terminal list registration notification frame from the satellite receiving station 702, the satellite receiving station 701 deletes the entry of the terminal 801 from its own receiving target terminal list (SEQ2313).

Further, the terminal 801 calculates the radio resource (time / frequency) for transmitting the next data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system. Then, the next data frame is generated and transmitted (broadcast) (SEQ2302).

At this point, the location where the terminal 801 is located is outside the receivable range 711 of the satellite receiving station 701 and the receivable range 712 of the satellite receiving station 702. Since the satellite receiving station 701 has already deleted the terminal 801 from its own list of reception target terminals, it does not perform unnecessary reception / demodulation processing on the data frame from the terminal 801. Further, since the satellite receiving station 702 does not register the terminal 801 in its own reception target terminal list, it does not perform reception / demodulation processing on the data frame from the terminal 801.

Further, since the satellite receiving station 703 registers the ID of the terminal 801 in its own reception target terminal list based on the frame reception information received from the satellite receiving station 702, it is based on the same rules 1 to 4 as the terminal 801. , The terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from the terminal ID and the code required for demodulating the data frame, attempts to receive and demolish the data frame, and succeeds in demolishing (SEQ2334). ).

According to the communication sequence example shown in FIG. 23, when the terminal 801 next transmits a data frame, the receivable range 713 of the satellite receiving station 703 two behind the satellite receiving station 701 whose reception target is the terminal 801 is 713. However, the satellite receiving station 703 can receive the next data frame from the terminal 801. Further, the satellite receiving station 701 prevents the terminal 801 from executing unnecessary reception / demodulation processing after passing from its own receivable range 711 by the notification from the subsequent satellite receiving station 703 in the same satellite orbit. Can be done.

F-2. Frame configuration FIG. 24 shows a frame configuration example of the data portion of the frame reception information frame. The format other than the data part shall be according to the communication method used. The frame reception information frame is a frame for notifying a subsequent satellite receiving station in the same satellite orbit of the frame reception information regarding the frame received from the terminal by the satellite receiving station.

In the nSTA field, the number of frame reception information (Frame Rx Info) stored in the data part is stored. The nSTA field is followed by the number of Frame Rx Info fields described in the nSTA field. In each Frame Rx Info field, frame reception information regarding a frame received from each terminal is stored. In the frame configuration example shown in FIG. 24, information indicating the value n is stored in the nSTA field, and n Frame Rx Info fields are stored.

Each Frame Rx Info field includes an ID field, an Ftype field, and Freq. Includes the Error field, the Propage Delivery field, the Data Tx Interval field, the Next Data Tx Interval field, and the Data Rx SAT ID, respectively.

In the ID field, the ID (terminal ID) of the terminal that is the source of the received frame is stored. A value indicating the type of received frame is stored in the Ftype field. Specifically, when the value stored in the Ftype field is 0, a notification frame is indicated, and when it is 1, a data frame is indicated. Freq. The error estimation result of the received frame is stored in the Error field. In the Promotion Delivery field, the propagation delay estimation result of the received frame is stored. The data frame transmission interval is stored in the Data Tx Interval field. The time until the next data frame is transmitted is stored in the Next Data Tx Interval field. The Next Data Tx Interval field is added only when Ftype is 0, that is, when a notification frame is received. In the Data Rx SAT ID field, the ID (SAT ID) of the satellite receiving station that received the corresponding frame is stored.

F-3. Frame reception information Frame reception operation FIGS. 25A and 25B show a processing procedure for a satellite receiving station to receive a frame reception information frame in the form of a flowchart.

First, the satellite receiving station determines whether or not the frame reception information frame has been received (step S2501). Then, when the satellite receiving station receives the frame reception information frame (Yes in step S2501), the received frame is demodulated (step S2502), and it is determined whether or not the demodulation processing is successful (step S2503). ..

If the demodulation process of the frame reception information frame is successful (Yes in step S2503), the satellite receiving station acquires nSTA indicating the number of frame reception information stored in the frame reception information frame (step S2504). , The processing of each subsequent frame reception information (Frame Rx Info) is repeatedly executed for the number of frame reception information.

As the processing of the frame reception information, the satellite receiving station first, from the frequency error estimation result (Freq.Eror) and the propagation delay estimation result (Propagation Delivery), remains that the notification frame or the data frame can be received by the same satellite receiving station. Estimate the time (step S2505).

Next, based on the receivable remaining time estimated in step S2505 and the data transmission interval, it is determined whether or not the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (step S2506). Here, for the data transmission interval, the value stored in the Next Data Tx Interval field is used when Ftype is 0, that is, the received frame is a notification frame, and when Ftype is 1, that is, the received frame is a data frame. The value stored in the Data Tx Interval field is used for.

Then, if the data frame transmitted from the corresponding terminal can be received by the same satellite receiving station (Yes in step S2506), the satellite receiving station returns to step S2505 and receives the next frame reception information (Yes). The process of Frame Rx Info) is repeatedly executed.

On the other hand, if the next data frame transmitted from the corresponding terminal cannot be received by the same satellite receiving station (No in step S2506), the satellite receiving station determines the remaining receivable time and data transmission estimated in step S2505. Based on the interval, it is further determined whether or not the own station can receive the data frame transmitted from the corresponding terminal next (step S2507).

Then, if the own station can receive the data frame transmitted from the corresponding terminal (Yes in step S2507), the satellite receiving station has the terminal ID stored in the frame reception information (Frame Rx Info). , Register the data transmission interval in its own reception target terminal list (step S2508), then add the terminal ID of the corresponding terminal to the reception target terminal list registration notification frame (step S2509), and then return to step S2505 to perform the next step. The processing of the frame reception information (Frame Rx Info) is repeatedly executed.

On the other hand, if the own station cannot receive the data frame transmitted from the corresponding terminal next (No in step S2507), the satellite receiving station is a frame for transmitting to a subsequent satellite receiving station in the same satellite orbit. After adding the frame reception information to the reception information frame (step S2510), the process returns to step S2505 and the process of the next frame reception information (Frame Rx Info) is repeatedly executed.

When the processing for all the nSTA frame reception information stored in the frame reception information frame received in step S2501 is completed, the satellite receiving station needs to transmit the reception target terminal list registration notification frame. (Step S2511). Then, when it is necessary to transmit the reception target terminal list registration notification frame (Yes in step S2511), the satellite receiving station stores the number of stored reception target terminal list registration IDs in nSTA and receives the reception. The target terminal list registration notification frame is transmitted (step S2512).

Next, the satellite receiving station determines whether or not it is necessary to transmit a frame reception information frame to a subsequent satellite receiving station in the same satellite orbit (step S2513). Then, when it is necessary to transmit the reception target terminal list registration notification frame (Yes in step S2513), the satellite receiving station stores the number of stored reception target terminal list registration IDs in nSTA and frames. The received information frame is transmitted (step S2514).

F-3. Adjacent satellite receiving station information list FIG. 26 shows an example of an adjacent satellite receiving station information list held by the satellite receiving station. The illustrated adjacent satellite receiving station information list registers information on each adjacent satellite receiving station in which the satellite receiving station orbits in the same satellite orbit. The entry of each adjacent satellite receiving station stores the relative position from the own station, the satellite ID that identifies the satellite receiving station, and the distance from the own station. Here, the relative position is information indicating the position of the satellite in the same satellite orbit with respect to the own station. Negative indicates the front in the satellite orbit, and positive indicates the rear in the satellite orbit. Relative position 0 indicates the own station. The interval is information indicating the position interval from the own station. Negative indicates the front in the satellite orbit, and positive indicates the rear in the satellite orbit. Interval 0 indicates own station.

For example, in the examples shown in FIGS. 16 and 26, the data transmission interval is 10 min, the frequency error estimation result notified in the frame reception information frame is -30 kHz, the propagation delay estimation result is 2.5 ms, and the frame is set. When the satellite ID of the received satellite receiving station is 502, the next data frame can be received by the own station.

On the other hand, for example, the data transmission interval is 10 min, the frequency error estimation result notified in the frame reception information frame is -30 kHz, the propagation delay estimation result is 2.5 milliseconds, and the satellite ID of the satellite receiving station that received the frame is 503. In the case of, the next data frame cannot be received by either the same satellite receiving station or the own station, and it is necessary to transmit the frame reception information to the succeeding satellite receiving station.

According to the fourth embodiment, the terminal does not need to transmit the notification frame frequently, even if the terminal moves to the receivable range of several satellite receiving stations ahead in the long data transmission interval of the terminal. , The satellite receiving station whose receivable range is the corresponding terminal can receive and demodulate the data frame from the corresponding terminal.

G. Fifth Example In the first, third, and fourth embodiments described above, each satellite receiving station needs to process the received frame reception information, so that the processing amount of the satellite receiving station may increase. There is. Therefore, in the fifth embodiment, a method in which the satellite receiving station that has received the notification frame or the data frame determines the satellite receiving station that receives the next data frame will be described.

G-1. Example of Communication Sequence FIG. 27 shows an example of a communication sequence between the satellite receiving stations 701 to 703 and the terminal 801 when the method according to the fifth embodiment is applied. Since the satellite receiving stations 701 to 703 continue to move in the satellite orbit at a speed of several km per second, the time zone where the terminal 801 is located is in the receivable range 711 of the satellite receiving station 701 and the satellite. Time zone that is out of the receivable range 711 of the receiving station 701 and becomes the receivable range 712 of the satellite receiving station 702, and time that is out of the receivable range 712 of the satellite receiving station 702 and becomes the receivable range 713 of the satellite receiving station 703. There is a band.

The terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from its own ID and the code required for data frame generation based on the rules 1 to 4 determined in advance in the system, and the data frame. Is generated and transmitted (broadcast) (SEQ2701).

It is assumed that the terminal 801 is in the receivable range 711 of the satellite receiving station 701, and the satellite receiving station 701 has registered the terminal 801 in its own reception target terminal list. Therefore, the satellite receiving station 701 uses the ID registered in the reception target terminal list, and is a radio resource (time) for which the terminal 801 transmits a data frame from the terminal ID based on the same rules 1 to 4 as the terminal 801. -Frequency) and the code required for demodulation of the data frame are calculated, and the data frame is received and demodulated (SEQ2711). Here, it is assumed that the satellite receiving station 701 succeeds in receiving and demodulating the data frame.

Then, the satellite receiving station 701 sets the data frame to be transmitted next from the terminal 801 to the satellite receiving station based on the terminal ID at the time of receiving the data frame, the frequency error estimation result, the propagation delay estimation result, and the adjacent satellite receiving station information. It is determined that the 703 is receivable (SEQ2712), and the reception target terminal registration frame is transmitted to the satellite receiving station 703 (SEQ2713).

The satellite receiving station 703 registers the terminal ID and the data transmission interval stored in the receiving target terminal registration frame received from the satellite receiving station 701 in its own receiving target terminal list (SEQ2731).

Further, since the satellite receiving station 701 has determined that the next data frame transmitted from the terminal 801 cannot be received by its own station (SEQ2712), the entry of the terminal 801 is deleted from the list of its own receiving target terminals (SEQ 2712). SEQ2714).

After that, after a lapse of time, the terminal 801 generates and transmits (broadcasts) the next data frame (SEQ2702).

Further, since the satellite receiving station 703 registers the ID of the terminal 801 in its own receiving target terminal list based on the receiving target terminal registration frame received from the satellite receiving station 701, the same rules 1 to 4 as those of the terminal 801 are applied. Based on this, the terminal 801 calculates the radio resource (time / frequency) for transmitting the data frame from the terminal ID and the code required for demolishing the data frame, attempts to receive and demolish the data frame, and succeeds in demolishing. (SEQ2732).

According to the communication sequence example shown in FIG. 27, when the terminal 801 next transmits a data frame, the receivable range 713 of the satellite receiving station 703 two behind the satellite receiving station 701 whose reception target is the terminal 801 is 713. However, the satellite receiving station 703 can receive the next data frame from the terminal 801 based on the determination processing of the receivable satellite receiving station by the satellite receiving station 701. Further, the satellite receiving station 701 prevents the terminal 801 from executing unnecessary reception / demodulation processing after passing from its own receivable range 711 by the notification from the subsequent satellite receiving station 703 in the same satellite orbit. Can be done.

G-2. Frame Configuration Example FIG. 28 shows a frame configuration example of the data portion of the reception target terminal registration frame. The format other than the data part shall be according to the communication method used. The reception target terminal registration frame is a frame in which the satellite receiving station instructs subsequent satellite receiving stations in the same satellite orbit to register the corresponding terminal in the reception target terminal list.

In the nSTA field, the number of terminal information (STA Info) stored in the data part is stored. The nSTA field is followed by the number of STA Info fields described in the nSTA field. In each STA Info field, terminal information regarding a terminal instructing the satellite receiving station of the transmission destination to be registered in the reception target terminal list is stored. In the frame configuration example shown in FIG. 28, information indicating the value n is stored in the nSTA field, and n STA Info fields are stored.

Each STA Info field includes an ID field and a Data Tx Interval field, respectively. The ID of the terminal to be received is stored in the ID field. In the Data Tx Interval field, the data frame transmission interval of the corresponding terminal is stored.

G-3. Processing operation of the satellite receiving station FIG. 29 shows a processing procedure for the satellite receiving station to receive a notification frame in the form of a flowchart.

First, the satellite receiving station refers to the reception target terminal list, and obtains the radio resource (time / frequency) for receiving the notification frame from the registered terminal and the information necessary for demodulating the notification frame in the above-mentioned rules 1 to 4. It is calculated based on (step S2901).

Next, the satellite receiving station determines whether or not the notification frame reception time calculated in step S2901 has been reached (step S2902). When the notification frame reception time arrives (Yes in step S2902), the satellite receiving station detects the notification frame from the corresponding terminal using the preamble and synchronization information calculated in step S2901 (step S2903), and calculates it in step S2901. The received notification frame is demodulated using the scramble pattern (step S2904). Then, the satellite receiving station determines whether or not the demodulation of the notification frame is successful (step S2905). If the demodulation of the notification frame fails (No in step S2905), the process returns to step S2901 and the satellite receiving station tries to receive the next notification frame.

On the other hand, if the demodulation of the notification frame is successful (Yes in step S2905), the satellite receiving station will transmit the next data frame based on the terminal ID and the data transmission interval stored in the received notification frame. Is determined (step S2906). Then, the satellite receiving station determines whether or not the next data frame transmitted from the corresponding terminal can be received by the own station (step S2907).

Here, when the data frame to be transmitted next from the corresponding terminal can be received by the satellite receiving station itself (Yes in step S2907), the satellite receiving station has a terminal ID stored in the received notification frame. Information such as the data transmission interval is registered in the reception target terminal list (step S2908).

If the satellite receiving station itself cannot receive the next data frame transmitted from the corresponding terminal (No in step S2907), the satellite receiving station generates a reception target terminal registration frame (step S2909), and the satellite receiving station generates a reception target terminal registration frame (step S2909). The reception target terminal registration frame is transmitted to another satellite receiving station that can receive the next transmitted data frame (step S2910).

Next, the satellite receiving station confirms whether or not the corresponding terminal exists in its own reception target terminal list (step S2911), and if it does exist (Yes in step S2911), it corresponds from its own reception target terminal list. Delete the terminal entry (step S2912).

FIG. 30 shows the processing procedure for the satellite receiving station to receive the data frame in the form of a flowchart. However, it is assumed that the satellite receiving station can execute the data frame reception processing in parallel for each terminal registered in the reception target terminal list.

First, the satellite receiving station acquires the information of the target terminal such as the terminal ID from the reception target terminal list (step S3001), and is necessary for the radio resource (time / frequency) for receiving the data frame from the target terminal and the data frame demodulation. Information is calculated based on the above-mentioned rules 1 to 4 (step S3002).

Next, the satellite receiving station determines whether or not the data frame reception time calculated in step S3002 has been reached (step S3003). When the data frame reception time arrives (Yes in step S3003), the satellite receiving station detects the data frame from the corresponding terminal using the preamble and synchronization information calculated in step S3002 (step S3004), and calculates it in step S3002. The received data frame is demodulated using the scramble pattern (step S3005). Then, the satellite receiving station determines whether or not the demodulation of the data frame is successful (step S3006). If the demodulation of the data frame fails (No in step S3006), the process returns to step S3001 and the satellite receiving station tries to receive the next notification frame.

On the other hand, if the demodulation of the data frame is successful (Yes in step S3006), the satellite receiving station selects the next data frame to be transmitted based on the terminal ID and the data transmission interval stored in the data frame. A receivable satellite receiving station is determined (step S3007). Then, the satellite receiving station determines whether or not the next data frame transmitted from the corresponding terminal can be received by the own station (step S3008).

Here, when the data frame to be transmitted next from the corresponding terminal can be received by the satellite receiving station itself (Yes in step S3008), the satellite receiving station has a terminal ID stored in the received data frame. Information such as the data transmission interval is registered in the reception target terminal list (step S3009).

If the satellite receiving station itself cannot receive the next data frame transmitted from the corresponding terminal (No in step S3008), the satellite receiving station generates a reception target terminal registration frame (step S3010), and the satellite receiving station generates a reception target terminal registration frame (step S3010). The reception target terminal registration frame is transmitted to another satellite receiving station that can receive the next transmitted data frame (step S3011).

Then, the satellite receiving station confirms whether or not the corresponding terminal exists in its own reception target terminal list (step S3012), and if it exists (Yes in step S3012), it corresponds from its own reception target terminal list. The terminal entry is deleted (step S3013).

FIG. 31 shows a processing procedure for the satellite receiving station to receive the reception target terminal list registration frame in the form of a flowchart.

First, the satellite receiving station determines whether or not the reception target terminal list registration frame has been received (step S3101). Then, when the satellite receiving station receives the reception target terminal list registration frame (Yes in step S3101), the satellite receiving station demodulates the received frame (step S3102) and determines whether or not the demodulation processing is successful (step). S3103).

When the satellite receiving station succeeds in demodulating the reception target terminal list registration frame (Yes in step S3103), the satellite receiving station acquires nSTA indicating the number of STA Info fields stored in the reception target terminal list registration frame. (Step S2204), the subsequent processing of each STA Info field is repeatedly executed for the number of nSTAs. In this iterative process, terminal information such as the terminal ID and the data frame transmission interval stored in the STA Info field is registered in its own reception target terminal list (step S3105).

The satellite receiving station can register the newly received terminal in its own reception target terminal list by processing the reception target terminal list registration frame according to the processing procedure shown in FIG. 31.

Therefore, according to the fifth embodiment, it is not necessary for the terminal to frequently transmit the notification frame, and the terminal may move to the receivable range of several satellite receiving stations ahead in the long data transmission interval of the terminal. However, the satellite receiving station whose receivable range is the corresponding terminal can receive and demodulate the data frame from the corresponding terminal.

H. Effect In this section H, the effects brought about by the above-mentioned first to fifth embodiments are summarized. According to the first to fifth embodiments, the following effects (1) and (2) can be obtained.

(1) The terminal does not need to send the notification frame frequently. It is possible for a satellite receiving station that can receive data frames periodically transmitted from the terminal to receive and demodulate.
(2) It is possible to prevent the satellite receiving station from performing unnecessary reception and demodulation for a terminal that has passed its receivable range.

It leads to the following effects further than the above (1) and (2).

(3) Lower power consumption and lower cost of terminals (4) Increase the number of units that can be accommodated per receiving station (5) Reduce the number of receiving stations required for the system (6) Reduce the cost of communication services

I. Sixth Example In the first to fifth embodiments described above, in the communication sequence in which the terminal transmits the notification frame and then the data frame is transmitted, the satellite receiving station basically selects the terminal that has received the notification frame. Target for reception. On the other hand, in the sixth embodiment, the terminal transmits the data frame without transmitting the notification frame.

FIG. 32 shows an example of a communication sequence between a terminal and a receiving station in a system in which the terminal can arbitrarily transmit a data frame. The receiving station does not know the radio resource to which the terminal sends the data frame. The radio resource referred to here includes a transmission time, a transmission frequency, and a code used for transmission. Therefore, the receiving station needs to perform reception and demodulation processing for all radio resources (time, frequency, code).

However, if reception and demodulation processing is executed for all wireless resources, the resources (memory usage, calculation amount, etc.) required for reception processing at the receiving station become enormous, and the cost of the receiving station increases, the size increases, and so on. Problems such as increased power consumption arise. In particular, when a receiving station is mounted on a low earth orbit satellite, it is necessary to reduce the size and power consumption of the receiving station.

On the other hand, in the sixth embodiment, the terminal adds information regarding the transmission of the next data frame to the data frame. Then, the satellite receiving station side manages the radio resource that executes the reception and demodulation processing of the next data frame based on the information added to the data frame. Therefore, according to the sixth embodiment, the satellite receiving station can limit the radio resources for performing the reception and demodulation processing, and realizes cost reduction, miniaturization, and low power consumption of the receiving station. It will be easier.

I-1. The system configuration diagram 33 schematically shows a configuration example of the LPWA wireless communication system according to the sixth embodiment. In the example shown in the figure, a plurality of receiving stations installed on the ground (hereinafter referred to as "ground stations") and a plurality of low earth orbit satellite receiving stations orbiting the earth in a low orbit (hereinafter, simply "satellite reception"). It is also called a "station") and consists of innumerable terminals scattered on the ground.

I-2. Communication sequence example In the example shown in FIG. 33, the satellite receiving station 3301 and the satellite receiving station 3302 are adjacent satellite receiving stations orbiting in the same satellite orbit. As the satellite receiving station 3301 and the satellite receiving station 3302 move in the satellite orbit, the receivable range 3311 of the satellite receiving station 3301 and the receivable range 3312 of the satellite receiving station 3302 also move on the ground.

FIG. 34 shows an example of a communication sequence between the terminal 3401 included in either the receivable range 3311 or the receivable range 3312 and the satellite receiving station 3301 and the satellite receiving station 3302.

First, the terminal 3401 transmits (broadcasts) the first data frame (SEQ3401).

The initial data frame refers to the frame when the terminal 3401 transmits for the first time immediately after the power is turned on. The terminal 3401 transmits using the radio resources (time, frequency, and code) that the satellite receiving stations 3301 and 3302 always receive. Further, the terminal 3401 stores the information of the radio resource used for the transmission of the next normal data frame in the initial data frame.

In the example shown in FIG. 34, when the terminal 3401 transmits the first data frame, the location where the terminal 3401 is located is the receivable range 3311 of the satellite receiving station 3301, so that the satellite receiving station 3301 receives the first data frame and receives the first data frame. Successful demodulation (SEQ3411). Next, the satellite receiving station 3301 determines a satellite receiving station that can receive the next normal data frame based on the radio resource for transmitting the next normal data frame stored in the initial data frame. Then, since the satellite receiving station 3301 itself can receive the next normal data frame, the satellite receiving station 3301 registers the information of the radio resource of the normal data frame to be transmitted next to the terminal 3401 in its reception list (). SEQ3412).

On the other hand, when the terminal 3401 transmits the first data frame, the place where the terminal 3401 is located is outside the receivable range 3312 of the satellite receiving station 3302, so that the satellite receiving station 3302 cannot receive the first data frame.

Next, the terminal 3401 transmits a normal data frame using the radio resource stored in the initial data frame (SEQ3402). Further, the terminal 3401 further stores the information of the radio resource used for the transmission of the next normal data frame in the normal data frame.

The satellite receiving station 3301 can receive and demodulate the normal data frame transmitted by the terminal 3401 in a pinpoint manner by executing the reception and demodulation processing based on the radio resources registered in its reception list. SEQ 3413). On the other hand, when the terminal 3401 transmits this normal data frame, the place where the terminal 3401 is located is outside the receivable range 3312 of the satellite receiving station 3302, so that the satellite receiving station 3302 cannot receive this normal data frame.

Further, the satellite receiving station 3301 determines a satellite receiving station that can receive the next normal data frame based on the radio resource for transmitting the next normal data frame stored in the received normal data frame. Then, since the satellite receiving station 3301 itself can receive the next normal data frame, the satellite receiving station 3301 re-registers the terminal 3401 in its receiving list (SEQ3414).

Next, the terminal 3401 transmits the next normal data frame using the radio resource stored in the previous normal data frame (SEQ3403). Further, the terminal 3401 further stores the information of the radio resource used for the transmission of the next normal data frame in the normal data frame.

The satellite receiving station 3301 can receive and demodulate the normal data frame transmitted by the terminal 3401 in a pinpoint manner by executing the reception and demodulation processing based on the radio resources registered in its reception list. SEQ3415). On the other hand, when the terminal 3401 transmits this normal data frame, the place where the terminal 3401 is located is outside the receivable range 3312 of the satellite receiving station 3302, so that the satellite receiving station 3302 cannot receive this normal data frame.

Further, the satellite receiving station 3301 determines a satellite receiving station that can receive the next normal data frame based on the radio resource for transmitting the next normal data frame stored in the received normal data frame. Since the satellite receiving station 3301 cannot receive the next normal data frame, the receiving target radio resource information notification frame is transmitted to the receivable satellite receiving station 3302 (SEQ3416).

The satellite receiving station 3302 registers the information of the radio resource stored in the reception target radio resource information notification frame received from the satellite receiving station 3301 in its own reception list (SEQ3421).

Next, the terminal 3401 transmits the next normal data frame using the radio resource stored in the previous normal data frame (SEQ3404).

The location where the terminal 3401 is located when the next normal data frame is transmitted is within the receivable range 3312 of the satellite receiving station 3302. The satellite receiving station 3302 can receive and demodulate the normal data frame transmitted by the terminal 3401 in a pinpoint manner by executing the reception and demodulation processing based on the radio resource registered in its reception list. SEQ3422). On the other hand, when the terminal 3401 transmits this normal data frame, the place where the terminal 3401 is located has moved out of the receivable range 3312 of the satellite receiving station 3301, so that the satellite receiving station 3301 uses this normal data frame. I can't receive it.

The terminal may transmit the initial data frame not only immediately after the power is turned on but also periodically. Even if the satellite receiving station fails to receive the normal data frame, the terminal will be registered in the receiving list of the satellite receiving station again from the time when the first data frame is successfully received, so that the terminal will periodically receive the first data frame. Is desirable to send.

I-3. Device Configuration Sixth, also in the sixth embodiment, the configuration of the terminal may be the same as that of FIG. 3, and therefore, the description of the terminal configuration will be omitted in this section I.

FIG. 35 shows a functional configuration example of the satellite receiving station 3500 in the system according to the sixth embodiment. The satellite receiving station 3500 is used by being mounted on a low earth orbit satellite orbiting the earth in any of the satellite orbits shown in FIG. 33. The satellite receiving station 3500 includes an LPWA unit 3520 and an intersatellite communication unit 3530.

The LPWA unit 3520 receives a frame transmitted by a terminal on the ground. The LPWA unit 3520 has the same reference number as that of FIG. 4 for the same components as the receiving station 200 shown in FIG. The LPWA unit 3520 further includes a receivable receiving station determination unit 3526. The receivable receiving station determination unit 3526 determines the receiving station that can receive the next data frame based on the next data frame transmission information stored in the data frame received from the terminal.

The intersatellite communication unit 3530 includes a wireless communication unit 3531, a wireless control unit 3532, a frame generation unit 3533, and a frame detection / demodulation unit 3534.

The wireless communication unit 3531 transmits and receives wireless signals. The wireless communication unit 353 receives radio waves under the control of the wireless control unit 3532, converts them into radio signals, and passes them to the frame detection / demodulation unit 3534. Further, the wireless communication unit 3531 converts the frame generated by the frame generation unit 3533 into a wireless signal and transmits it under the control of the wireless control unit 3532.

The wireless control unit 3532 controls the wireless communication unit 3531 so that frames can be transmitted and received between satellite receiving stations.

The frame generation unit 3533 stores the next data frame transmission information acquired from the receivable receiving station determination unit 3526 on the LPWA unit 3520 side, and generates a frame according to a predetermined format.

The frame detection / demodulation unit 3534 detects and demodulates a frame from the received signal of the wireless communication unit 3531. When the frame detection / demodulation unit 3534 succeeds in demodulating the frame, the frame detection / demodulation unit 3534 passes the received data to the storage unit 205 in the LPWA unit 3520. Specifically, the information of the radio resource of the reception target terminal received from the satellite receiving station in front of the same orbit is stored in the reception list in the storage unit 205.

I-4. Frame configuration FIG. 36 shows a configuration example of a data frame transmitted / received between the terminal and the satellite receiving station. However, it is assumed that the frame configuration of the initial data frame and the normal data frame is the same. The data frame includes ID, DATA, Time Interval, Ch, Code, and CRC fields.

In the ID field, an ID which is a unique identifier of the terminal 100 which is the transmission source is stored. Transmission data is stored in the DATA field. In the case of a data frame, data acquired from the sensor 104 or the like is stored. In the Time Interval field, information regarding the transmission interval from the transmission of the data frame to the transmission of the next data frame is stored. The Ch field stores information about the frequency used when transmitting the next data frame. The Code field contains information about the code to be used the next time the data frame is transmitted, specifically preamble, synchronization information (Sync), and information indicating the four initial values needed to generate the scramble pattern. Will be done. In the CRC field, the CRC value calculated for the information stored in the ID field, the DATA field, the Time Interval field, the Ch field, and the Code field is stored. On the receiving side, the demodulation success determination is performed using the CRC value.

FEC coding and order rearrangement (interleave) are performed on the series in which the above ID, DATA, Time Interval, Ch, Code, and CRC are concatenated to generate a payload. Furthermore, a frame is generated by concatenating the preamble, which is a known pattern used for frame detection and synchronization acquisition, and synchronization information at the beginning of the payload, and then taking an exclusive OR (XOR) with the scramble pattern for each bit. Or.

In the system, rules for determining the preamble and synchronization information required for frame generation and the scramble pattern generation method are predetermined. The preamble and synchronization information required for frame generation and the scramble pattern generation method follow Rule 3 and Rule 4 shown in FIG. 6, respectively. The preamble / synchronization information (Preamble / Sync) is determined by inputting two initial values Seed (P) -1 and Seed (P) -2 for calculating the preamble and synchronization information in Rule 3. Further, the scramble pattern is determined by inputting two initial values Seed (S) -1 and Seed (S) -2 for the scramble pattern in Rule 4.

Each initial value is determined in advance in the system and is held in the storage unit 106 in the terminal 100 and the storage unit 3525 in the satellite receiving station 3500. In addition, the initial values that can be used differ between the initial data frame and the normal data frame.

FIG. 37 shows a frame configuration example of the data part of the reception target radio resource information notification frame. The format other than the data part shall be according to the communication method used. The reception target radio resource information notification frame provides the radio resource for the next normal data frame transmission to other satellite receiving stations that can be received when the satellite receiving station determines that the next normal data frame cannot be received by itself. It is a frame to notify.

The data part of the reception target radio resource information notification frame includes an Rx Time field, a Ch field, and a Code field. Information about the reception time of the next data frame is stored in the RxTime field. Information about the reception frequency of the next data frame is stored in the Ch field. The Code field stores information about the receive code of the next data frame, specifically, preamble, synchronization information (Sync), and information indicating the four initial values required to generate the scramble pattern.

I-5. Processing operation of the terminal In FIG. 38, the processing operation performed by the terminal is dead in the form of a flowchart.

First, the terminal determines the radio resource (time, frequency, code) used for transmitting the initial data frame (step S3801).

Next, the terminal determines the radio resource (time, frequency, code) to be used for the transmission of the next normal data frame (step S3802).

Next, the terminal generates the initial data frame (step S3803). In the Time Interval, Ch, and Code fields of the initial data frame, each information of the radio resource used for the transmission of the next normal data frame determined in step S3802 is stored.

Then, when the transmission time of the first data frame arrives (Yes in step S3804), the terminal transmits the first data frame generated in step S3803 using the transmission frequency calculated in step S3801 (step S3805).

Next, the terminal determines whether or not the frame to be transmitted one after another is the first data frame (step S3806).

If the frame to be transmitted one after another is not the first data frame (No in step S3808), the terminal determines the radio resource (time, frequency, code) used for the transmission of the normal data frame one after another (step S3807).

Next, the terminal generates a normal data frame (step S3808). In the Time Interval, Ch, and Code fields of the normal data frame, each information of the radio resource used for transmission of the next normal data frame determined in step S3807 is stored. However, when the data frame to be transmitted next is the first data frame (Yes in step S3806), each field of Time Interval, Ch, and Code of the normal data frame is filled with 0.

Then, when the transmission time of the normal data frame arrives (Yes in step S3809), the terminal transmits the normal data frame generated in step S3803 using the transmission frequency calculated in step S3802 (step S3801).

Next, the terminal determines whether or not the next frame to be transmitted is the first data frame (step S3811). If the frame to be transmitted next time is the first data frame (Yes in step S3811), the terminal returns to step S3801 and repeatedly executes the process for transmitting the first data frame. If the next frame to be transmitted is not the first data frame (No in step S3811), the terminal returns to step S3806 and repeatedly executes the process for transmitting the normal data frame.

I-6. Processing operation of the satellite receiving station FIG. 39 shows the processing operation for the satellite receiving station to receive the initial data frame in the form of a flowchart.

First, the satellite receiving station executes reception and demodulation processing for all frequencies and codes assigned to the transmission of the initial data frame (step S3901).

Then, when the reception and demodulation processing of the initial data frame is successful (Yes in step S3902), the satellite receiving station is based on the transmission interval stored in the Time Interval field in the initial data frame in which the demodulation is successful. , Calculate the expected reception time of the next normal data frame (step S3903).

Next, the satellite receiving station determines whether or not the satellite receiving station that can receive the next normal data frame is itself (step S3904).

If the satellite receiving station that can receive the next normal data frame is itself (Yes in step S3904), the satellite receiving station has the estimated reception time calculated in step S3903, the frequency stored in the first data frame, and the frequency. The code is registered in its own reception list (step S3905).

On the other hand, if the satellite receiving station that can receive the next normal data frame is not itself (No in step S3904), the satellite receiving station sends the satellite receiving station that can receive the next normal data frame to the radio resource to be received. The information notification frame is transmitted (step S3906).

The processing of steps S3903 and S3904 in the flowchart shown in FIG. 39 will be described with reference to FIG.

For example, if the reception time of the first data frame for which the demodulation process was successful in step S3902 is 12:00:01.020 and the Time Interval is 00: 01: 00.000, the expected reception time of the next normal data frame is 12. : 01: 01.020. However, since the distance between the ground and the satellite receiving station is as long as several hundred kilometers, a propagation delay occurs. In addition, since the satellite receiving station moves, it is necessary to consider that the propagation delay amount differs for each data frame.

FIG. 16 shows an example of the time change of the frequency error and the propagation delay when the altitude of the satellite is 600 km and the frequency is 2 GHz. This is an example of the case where the satellite passes overhead of the terminal, and it is assumed that the satellite receiving station can receive for 6 minutes for one terminal. For the calculation of the frequency error, the model described in 3GPP TR 38.811 V15.1.0 (Non-Patent Document 1) was referred to.

For example, it is assumed that the frequency error estimation result at the time of receiving the data frame is 40 kHz. In that case, if the propagation delay amount is 3.5 ms and the Time Interval is 00: 01: 00.000, the propagation delay amount at the time of receiving the next normal data frame is 2.5 ms. Therefore, the expected reception time of the next normal data frame is 12: 01: 01.019.

Subsequently, it is determined whether or not the satellite receiving station that can receive the next normal data frame is itself.

For example, in the example shown in FIG. 16, when the frequency error estimation result at the time of receiving the data frame is 40 kHz and the Time Interval is 00: 01: 00.000, the satellite receiving station capable of receiving the next normal data frame is Be yourself.

On the other hand, if the frequency error estimation result at the time of receiving the data frame is -40 kHz and the Time Interval is 00: 01: 30.000, the satellite receiving station that can receive the next normal data frame orbits the same satellite orbit 1. It will be the satellite receiving station one behind.

FIG. 40 shows the processing procedure for the satellite receiving station to receive a normal data frame in the form of a flowchart. However, the satellite receiving station shall execute this process for each reception target radio resource registered in the reception list.

First, the satellite receiving station acquires the radio resource (time, frequency, code) to be received from the reception list (step S4001). Then, the satellite receiving station determines whether or not the reception target time has come (step S4002).

When the reception target time arrives (Yes in step S4002), the satellite receiving station executes reception and demodulation processing for the reception target frequency using the reception target code (step S4003). Then, the satellite receiving station determines whether or not the demodulation of the normal data frame is successful (step S4004).

If the demodulation of the normal data frame fails (No in step S4004), the satellite receiving station skips all the subsequent processing steps and ends the reception processing of the normal data frame in the radio resource to be received.

On the other hand, if the demodulation of the normal data frame is successful (Yes in step S4004), does the satellite receiving station store the information of the radio resource used for the transmission of the next normal data frame in the demodulated normal data frame? It is determined whether or not (step S4005).

If the demodulated normal data frame does not contain information on the radio resources used to transmit the next normal data frame (No in step S4005), the satellite receiving station skips all subsequent processing steps. The reception processing of the normal data frame in the reception target radio resource is terminated.

When the demodulated normal data frame stores information on the radio resource used for transmission of the next normal data frame (Yes in step S4005), the satellite receiving station determines the reception time of the normal data frame and the normal data frame. Based on the transmission interval stored in the data frame, the estimated reception time of the next normal data frame is calculated (step S4006).

Next, the satellite receiving station determines whether or not the satellite receiving station that can receive the next normal data frame is itself (step S4007).

If the satellite receiving station that can receive the next normal data frame is itself (Yes in step S4007), the satellite receiving station uses the estimated reception time calculated in step S4006 and the normal data frame demodulated in step S4003. Register the stored frequency and code in its own reception list (step S4008).

If the satellite receiving station that can receive the next normal data frame is not itself (No in step S4007), the satellite receiving station sends the satellite receiving station that can receive the next normal data frame to the radio resource to be received. The information notification frame is transmitted (step S4009).

FIG. 41 shows a processing procedure for the satellite receiving station to receive the reception target radio resource information notification frame in the form of a flowchart.

First, the satellite receiving station determines whether or not the reception target radio resource information notification frame has been received from another satellite receiving station (step S4101). Then, when the reception target radio resource information notification frame is received (Yes in step S4101), the satellite receiving station demodulates the reception target radio resource information notification frame (step S4102) and succeeds in demodulating the frame. It is determined whether or not it has been done (step S4103).

If the demodulation of the reception target radio resource information notification frame is successful (Yes in step S4103), the satellite receiving station determines whether or not the frame is addressed to its own station (step S4104).

Then, when the demodulated reception target radio resource information notification frame is addressed to its own station (Yes in step S4104), the satellite receiving station registers the information stored in the frame in its own reception list (step S4105). ).

If the demodulated reception target radio resource information notification frame is not addressed to its own station (No in step S4104), the satellite receiving station transfers the reception target radio resource information notification frame to the corresponding satellite receiving station (step). S4106).

I-7. Effect The effects brought about by the sixth embodiment described in this section I are summarized. According to the sixth embodiment, the following effects (1) and (2) can be obtained.

(1) There is no need for signaling for allocating radio resources between the terminal and the satellite receiving station, and the radio resources for which the satellite receiving station executes reception and demodulation processing can be limited.
(2) There is no need for signaling for radio resource allocation between the terminal and the satellite receiving station, and it is possible to follow even if the satellite receiving station moves and the satellite receiving station that can receive the data frame transmitted by the terminal changes. be.

It leads to the following effects further than the above (1) and (2).

(3) Low power consumption and low cost of terminals (4) Increase in the number of units that can be accommodated per receiving station (5) Miniaturization and low power consumption of receiving stations (6) Reduction of the number of receiving stations required for the system (6) 7) Cost reduction of communication services

The present disclosure has been described in detail with reference to the specific embodiment. However, it is self-evident that a person skilled in the art may modify or substitute the embodiment without departing from the gist of the present disclosure.

Although the present specification has mainly described embodiments in which the present disclosure is applied to the LPWA communication method, the gist of the present disclosure is not limited to this. The present disclosure is similarly applicable to various types of communication systems that communicate between terminals on the ground and satellite receivers orbiting the earth. Further, although the present specification has described an embodiment specialized for a specific satellite constellation for convenience, the present disclosure can be similarly applied to a communication system using another satellite constellation. It can correspond to any number of satellite receiving stations.

In short, the present disclosure has been described in the form of an example, and the contents of the present specification should not be interpreted in a limited manner. In order to judge the gist of this disclosure, the scope of claims should be taken into consideration.

Note that this disclosure can also have the following structure.

(1) Operates as one of the satellite receiving stations that orbit the earth in a predetermined orbit and receive frames from terminals on the ground.
A receiving unit that receives and processes frames from the terminal,
Based on the frame reception information at the time of receiving a frame from the terminal, the frame transmission interval of the terminal, and the positional relationship of the surrounding satellite receiving stations, a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal is determined. Judgment unit and
A communication device equipped with.

(2) The frame reception information includes the frequency error estimation result and the propagation delay estimation result at the time of frame reception.
The communication device according to (1) above.

(3) The frame reception information includes the position information of the terminal.
The communication device according to (1) above.

(4) Exchange frame reception information with nearby satellite receiving stations,
The communication device according to any one of (1) to (3) above.

(5) The determination unit further determines a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal based on the frame reception information from the surrounding satellite receiving stations.
The communication device according to (4) above.

(6) The information of the terminal determined by the determination unit that the own station can receive the next frame to be transmitted is retained in the reception target terminal list, and the information is retained in the reception target terminal list.
The frame to be transmitted next by the terminal is received and processed based on the information held in the reception target terminal list.
The communication device according to (5) above.

(7) Notify the peripheral satellite receiving stations of the information of the terminals added to the receiving target terminal list based on the frame reception information from the surrounding satellite receiving stations.
The communication device according to (6) above.

(8) Based on the above notification from the satellite receiving stations in the vicinity, the information of the corresponding terminal is deleted from the reception target terminal list of the own station.
The communication device according to (7) above.

(9) Exchange the frame reception information with the identification information of the own station with the surrounding satellite reception stations, and
Notify the satellite receiving station whose identification information is shown in the frame receiving information of the information of the terminal added to the receiving target terminal list based on the frame receiving information from the surrounding satellite receiving stations.
The communication device according to (7) above.

(10) Notifying the peripheral satellite receiving stations that the determination unit has determined to be suitable for receiving the next frame transmitted from the terminal to the reception target terminal registration.
The communication device according to (1) above.

(11) The terminal that has notified the satellite receiving stations in the vicinity of the reception target terminal registration is excluded from the reception target of the own station.
The communication device according to (10) above.

(12) The terminal to which the reception target terminal registration is notified from the surrounding satellite receiving stations is set as the reception target of the own station.
The communication device according to any one of (10) and (11) above.

(13) The frame reception information includes the frame transmission interval notified from the terminal.
The determination unit estimates the estimated reception time of the next frame transmitted from the terminal based on the frame transmission interval and the frequency error estimation result at the time of frame reception.
The communication device according to (1) above.

(14) The determination unit is a satellite receiving station suitable for receiving the next frame transmitted by the terminal based on the estimated reception time of the next frame transmitted from the terminal and the positional relationship of the surrounding satellite receiving stations. To judge,
The communication device according to (13) above.

(15) The terminal that the determination unit determines that the next frame to be transmitted can be received by the own station is set as the reception target of the own station.
The communication device according to (14) above.

(16) Notifying the satellite receiving stations in the vicinity that the terminal has determined to be suitable for receiving the frame to be transmitted next, the radio resource information for receiving the frame of the terminal.
The communication device according to (14) above.

(17) In response to the notification of the radio resource information for receiving the frame of the terminal from the surrounding satellite receiving stations, the corresponding terminal is set as the reception target of the own station.
The communication device according to (16) above.

(18) The surrounding satellite receiving stations include at least one of a satellite receiving station moving in the same orbit and a satellite receiving station moving in an adjacent orbit.
The communication device according to any one of (1) to (17) above.

(19) A communication method that orbits the earth in a predetermined orbit and operates as a satellite receiving station that receives frames from terminals on the ground.
A reception step for receiving and processing a frame from the terminal, and
Based on the frame reception information at the time of receiving a frame from the terminal, the frame transmission interval of the terminal, and the positional relationship of the surrounding satellite receiving stations, a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal is determined. Judgment step to do and
Communication method with.

(20) It consists of a terminal installed on the ground and a plurality of satellite receiving stations that orbit the earth in a predetermined orbit.
Each of the plurality of satellite receiving stations is based on a receiving unit that receives and processes a frame from the terminal, frame reception information at the time of receiving a frame from the terminal, a frame transmission interval of the terminal, and a positional relationship of surrounding satellite receiving stations. The terminal is provided with a determination unit for determining a satellite receiving station suitable for receiving the next frame to be transmitted.
Communications system.

100 ... Terminal, 101 ... Wireless communication unit, 102 ... Wireless control unit 103 ... Frame generation unit, 104 ... Sensor 105 ... Radio resource determination unit, 106 ... Storage unit 200 ... Receiving station, 201 ... Wireless communication unit, 202 ... Wireless control Unit 203 ... Frame detection / demodulation unit, 204 ... Radio resource determination unit 205 ... Storage unit 1000 ... Satellite receiving station 1200 ... LPWA unit 1300 ... Intersatellite communication unit 1301 ... Wireless communication unit 1302 ... Wireless control unit 1303 ... Frame Generation unit, 1304 ... Frame detection / demodulation unit 3500 ... Satellite receiving station, 3520 ... LPWA unit 3526 ... Receivable receiving station determination unit 3531 ... Wireless communication unit, 3532 ... Wireless control unit 3533 ... Frame generation unit, 3534 ... Frame detection unit Demodition unit

Claims

It orbits the earth in a predetermined orbit and operates as one of the satellite receiving stations that receives frames from terminals on the ground.
A receiving unit that receives and processes frames from the terminal,
Based on the frame reception information at the time of receiving a frame from the terminal, the frame transmission interval of the terminal, and the positional relationship of the surrounding satellite receiving stations, a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal is determined. Judgment unit and
A communication device equipped with.
The frame reception information includes the frequency error estimation result and the propagation delay estimation result at the time of frame reception.
The communication device according to claim 1.
The frame reception information includes the position information of the terminal.
The communication device according to claim 1.
Exchange frame reception information with nearby satellite receivers,
The communication device according to claim 1.
The determination unit further determines a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal based on the frame reception information from the surrounding satellite receiving stations.
The communication device according to claim 4.
The information of the terminal determined by the determination unit that the own station can receive the next frame to be transmitted is retained in the reception target terminal list, and the information is retained in the reception target terminal list.
The frame to be transmitted next by the terminal is received and processed based on the information held in the reception target terminal list.
The communication device according to claim 5.
Notify the peripheral satellite receiving stations of the information of the terminals added to the receiving target terminal list based on the frame reception information from the surrounding satellite receiving stations.
The communication device according to claim 6.
Based on the above notification from the satellite receiving station in the vicinity, the information of the corresponding terminal is deleted from the reception target terminal list of the own station.
The communication device according to claim 7.
Exchange the frame reception information with the identification information of your own station with the satellite reception stations in the vicinity,
Notify the satellite receiving station whose identification information is shown in the frame receiving information of the information of the terminal added to the receiving target terminal list based on the frame receiving information from the surrounding satellite receiving stations.
The communication device according to claim 7.
Notifying the surrounding satellite receiving stations that the determination unit has determined to be suitable for receiving the next frame transmitted from the terminal, the registration of the reception target terminal is notified.
The communication device according to claim 1.
The terminal that has notified the satellite receiving stations in the vicinity of the reception target terminal registration is excluded from the reception target of the own station.
The communication device according to claim 10.
The terminal to which the reception target terminal registration is notified from the surrounding satellite receiving stations is the reception target of the own station.
The communication device according to claim 10.
The frame reception information includes the frame transmission interval notified from the terminal.
The determination unit estimates the estimated reception time of the next frame transmitted from the terminal based on the frame transmission interval and the frequency error estimation result at the time of frame reception.
The communication device according to claim 1.
The determination unit determines a satellite receiving station suitable for receiving the next frame transmitted by the terminal based on the estimated reception time of the next frame transmitted from the terminal and the positional relationship of the surrounding satellite receiving stations. ,
The communication device according to claim 13.
The terminal that the determination unit determines that the next frame to be transmitted can be received by the own station is set as the reception target of the own station.
The communication device according to claim 14.
Notifies the radio resource information for receiving the frame of the terminal to the surrounding satellite receiving stations determined to be suitable for receiving the frame to be transmitted next by the terminal.
The communication device according to claim 14.
In response to notification of radio resource information for receiving a terminal frame from a nearby satellite receiving station, the corresponding terminal is targeted for reception by the own station.
The communication device according to claim 16.
The surrounding satellite receiving stations include at least one of a satellite receiving station moving in the same orbit and a satellite receiving station moving in an adjacent orbit.
The communication device according to claim 1.
It is a communication method that orbits the earth in a predetermined orbit and operates as a satellite receiving station that receives frames from terminals on the ground.
A reception step for receiving and processing a frame from the terminal, and
Based on the frame reception information at the time of receiving a frame from the terminal, the frame transmission interval of the terminal, and the positional relationship of the surrounding satellite receiving stations, a satellite receiving station suitable for receiving the frame to be transmitted next by the terminal is determined. Judgment step to do and
Communication method with.
It consists of a terminal installed on the ground and multiple satellite receiving stations that orbit the earth in their respective orbits.
Each of the plurality of satellite receiving stations is based on a receiving unit that receives and processes a frame from the terminal, frame reception information at the time of receiving a frame from the terminal, a frame transmission interval of the terminal, and a positional relationship of surrounding satellite receiving stations. The terminal is provided with a determination unit for determining a satellite receiving station suitable for receiving the next frame to be transmitted.
Communications system.