REMOTE SYSTEM, COMMUNICATION TERMINAL DEVICE, RETRANSMISSION CONTROL METHOD, AND PROGRAM

Abstract

Provided is a remote system that: reliably facilitates retransmission of an uplink message not received by a server, by using LPWA communications; and appropriately deletes uplink messages saved by a communications terminal device. The remote system includes: a communications terminal device mounted on a mobile body; and a server that performs LPWA communications with the communications terminal device. The communications terminal device wirelessly sends an uplink message to the server that includes behavior information that indicates travel completion and history information that indicates the number of uplink messages stored in a history storage unit, if the powering off of the mobile body has been detected. Once the communications terminal device wirelessly receives a downlink message including reception history information from the server, the communications terminal device: confirms the reception history information; resends uplink messages that the server has not received; and, once all resending has been completed, deletes all uplink messages stored in the history storage unit.

Description

[Technical field]

[0001] The present invention relates to a retransmission control method for a case in which a server fails to receive an uplink message wirelessly transmitted from a communication terminal device mounted on a mobile object in low power wide area (LPWA) communication. [Background technology]

[0002] In recent years, various wireless communication standards have been put into practical use, and LPWA communication, which can cover a wide area with low cost and low power consumption, has been attracting particular attention.

[0003] While LPWA communication has the above advantages, it has restrictions such as a limit on the number of communications that can be wirelessly transmitted, or a small amount of data that can be wirelessly transmitted at one time. For example, "SIGFOX (registered trademark)", one of the LPWA communications, has restrictions on the number of upstream messages that can be transmitted a maximum of 140 times per day and the maximum payload that can be wirelessly transmitted at one time being 12 bytes, and on the number of downstream messages that can be transmitted a maximum of 4 times per day and the maximum payload that can be wirelessly transmitted at one time being 8 bytes.

[0004] The following Patent Document 1 discloses a technology in which, in a system in which an upstream message is wirelessly transmitted from a communication terminal device to a server using LPWA communication, the communication terminal device resends an upstream message that the server was unable to receive. The communication terminal device disclosed in Patent Document 1 is mounted on a mobile object, and when it detects that the mobile object has stopped, it requests reception history information from the server. The communication terminal device receives the reception history information from the server in a downstream message, and resends the corresponding upstream message from among the stored upstream messages. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-113943 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is a possibility that the server may not be able to receive the resent upstream message even if the upstream message is resent using the method disclosed in Patent Document 1. For example, if the location where the mobile body is stopped is in a mountainous region, there is a possibility that the radio wave, which is the carrier wave of the upstream message transmitted by the communication terminal device, may not reach the base station.

[0007] Furthermore, if the number of times that downstream messages in the LPWA communication used are limited to a number less than the number of times that upstream messages are transmitted, downstream messages cannot be transmitted and retransmitted multiple times. However, in the retransmission method disclosed in Patent Document 1, even if the number of upstream messages that the server was unable to receive is zero or only one, when the stop of a moving object is detected, the communication terminal device requests reception history information from the server. Then, the server transmits a downstream message including the reception history information. In other words, valuable downstream messages are wasted.

[0008] Furthermore, since the memory capacity of the communication terminal device is limited, the number of upstream messages that can be stored in the memory of the communication terminal device is limited. Therefore, it is necessary to clear the stored upstream messages as appropriate, but Patent Document 1 does not disclose or suggest how to clear the stored upstream messages.

[0009] Therefore, the present invention aims to provide a remote system, a communication terminal device, a retransmission control method, and a program that enable the server to resend unreceived upstream messages resent using LPWA communication, which has limitations on the number of communications and the length of transmitted data, and that properly clears upstream messages stored by the communication terminal device. [Means for solving the problem]

[0010] (1) In order to solve the above problems, a remote system according to one aspect of the present invention includes a communication terminal device mounted on a mobile object, an LPWA communication network, and a server. The communication terminal device includes a detection unit, a conversion unit, a terminal control unit, a terminal communication unit, and a history storage unit. The detection unit detects whether the power supply of the mobile object is on or off. The conversion unit converts information sequentially acquired by a predetermined sensor into sensor data. The terminal control unit generates an upstream message including identification information for identifying the communication terminal device, a sequence number indicating the transmission order, behavior information indicating the behavior of the mobile object based on the power supply on or off detected by the detection unit, and the sensor data. The terminal communication unit wirelessly transmits the upstream message to the LPWA communication network. The history storage unit sequentially stores the upstream messages wirelessly transmitted by the terminal communication unit. When the detection unit detects that the power supply is off, the terminal control unit generates an upstream message including behavior information indicating the end of movement of the mobile object and history information indicating the number of upstream messages stored in the history storage unit.

[0011] The server includes a server receiving unit, a server storage unit, a reception history information generating unit, an acquiring unit, a server control unit, and a server transmitting unit. The server receiving unit receives an upstream message from the terminal communication unit via the LPWA communication network. The server storage unit stores the received upstream message. When the server receiving unit receives an upstream message including behavior information indicating the end of movement of a mobile object, the reception history information generating unit generates reception history information indicating whether or not the reception was successful based on a sequence number included in the upstream message stored in the server storage unit. The acquiring unit acquires communication quality information corresponding to the upstream message. The server control unit determines whether or not to generate a downstream message including the reception history information based on the reception history information, the history information, and the communication quality information. When the server control unit determines to generate a downstream message, the server transmitting unit transmits the downstream message to the terminal communication unit via the LPWA communication network.

[0012] When the terminal communication unit receives a downstream message, the terminal control unit specifies the sequence number of an upstream message not received by the server from reception history information included in the downstream message, reads out the upstream message with the specified sequence number from the history storage unit, has it resent to the terminal communication unit, and deletes all the upstream messages stored in the history storage unit.

[0013] (2) In one aspect of the present invention, in the remote system described above in (1), the server control unit may further determine whether or not to generate a current downstream message based on the elapsed time since the previous downstream message was sent.

[0014] (3) In one aspect of the present invention, in the remote system of (1) or (2) described above, the sensor sequentially acquires location information indicating a location where the moving object was located, the conversion unit calculates differential information indicating a difference between the first location and the second location based on the multiple pieces of location information sequentially acquired by the sensor, and the sensor data is data including information indicating the first location and the differential information.

[0015] (4) In one aspect of the present invention, in the remote system described in (3) above, the sensor may acquire location information expressed in longitude and latitude, and the conversion unit may convert the location information successively acquired by the sensor into sensor data expressed in x-y coordinates with a predetermined position as a reference position.

[0016] (5) In order to solve the above problem, a communication terminal device according to one aspect of the present invention is a communication terminal device mounted on a mobile body, and includes a detection unit, a conversion unit, a terminal control unit, a terminal communication unit, and a history storage unit. The detection unit detects whether the power supply of the mobile body is on or off. The conversion unit converts information sequentially acquired by a predetermined sensor into sensor data. The terminal control unit generates an upstream message including identification information for identifying the communication terminal device, a sequence number indicating the transmission order, behavior information indicating the behavior of the mobile body based on the power supply on or off detected by the detection unit, and the sensor data. The terminal communication unit wirelessly transmits the upstream message to the LPWA communication network and wirelessly receives the downstream message from the LPWA communication network to communicate with the server. The history storage unit stores the upstream message wirelessly transmitted by the terminal communication unit. The downstream message includes reception history information indicating whether reception was successful or not based on the sequence number included in the upstream message received by the server. When the detection unit detects that the power is turned off, the terminal control unit generates an upstream message including behavior information indicating the end of movement of the moving object and history information indicating the number of upstream messages stored in the history storage unit, and causes the terminal communication unit to wirelessly transmit the upstream message. When the terminal communication unit receives a downstream message, the terminal control unit identifies the sequence number of an upstream message not received by the server from the reception history information included in the downstream message, reads out the upstream message with the identified sequence number from the history storage unit, causes the terminal communication unit to resend it, and deletes all upstream messages stored in the history storage unit.

[0017] (6) In order to solve the above problem, a retransmission control method according to one aspect of the present invention is a retransmission control method for an upstream message used in a communication terminal device mounted on a mobile body, the method comprising: a terminal communication unit for communicating with a server by wirelessly transmitting an upstream message including a sequence number indicating a transmission order to an LPWA communication network and wirelessly receiving a downstream message from the LPWA communication network; and a history storage unit for storing the upstream message wirelessly transmitted to the server, the downstream message including reception history information indicating whether the reception was successful or not based on the sequence number received by the server. The retransmission control method includes the steps of: generating and wirelessly transmitting an upstream message including behavior information indicating the end of movement of the mobile body and history information indicating the number of upstream messages stored in the history storage unit when it is detected that the power supply of the mobile body is turned off; identifying the sequence number of an upstream message not received by the server from the reception history information included in the downstream message when the downstream message is received; retransmitting the upstream message having the identified sequence number from the history storage unit to the server; and deleting all the upstream messages stored in the history storage unit.

[0018] (7) In order to solve the above problem, a program according to one aspect of the present invention is a program that causes a communication terminal device mounted on a mobile body and equipped with a CPU and a memory to function as a detection unit that detects the on / off of the power supply of the mobile body, a conversion unit that converts information sequentially acquired by a specific sensor into sensor data, a terminal control unit that generates an upstream message including identification information for identifying the communication terminal device, a sequence number indicating the transmission order, behavior information indicating the behavior of the mobile body based on the on / off of the power supply detected by the detection unit, and the sensor data, a terminal communication unit that wirelessly transmits the upstream message to an LPWA communication network and wirelessly receives the downstream message from the LPWA communication network to communicate with a server, and a history storage unit that stores the upstream message wirelessly transmitted by the terminal communication unit, and causes the communication terminal device to execute a retransmission control process for the upstream message. The downstream message includes reception history information indicating whether reception was successful or not based on the sequence number included in the upstream message received by the server. The retransmission control process includes the steps of: when it is detected that the power of the mobile body has been turned off, generating and wirelessly transmitting an upstream message including behavior information indicating the end of the mobile body's movement and history information indicating the number of upstream messages stored in the history memory unit; when a downstream message is received, the server identifying the sequence number of the unreceived upstream message from the reception history information included in the downstream message; retransmitting the upstream message with the identified sequence number from the history memory unit to the server; and deleting all upstream messages stored in the history memory unit. Effect of the Invention

[0019] The present invention enables a server to resend upstream messages that it was unable to receive reliably, even when using LPWA communication, which has limitations on the number of communications and the length of transmitted data, and can properly clear upstream messages stored in a communication terminal device. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a configuration of a remote system 10. [Diagram 2] FIG. 2 is a functional configuration diagram of the communication terminal device 11. [Diagram 3] 13 is a diagram showing an example of location information temporarily stored in the memory of the terminal control unit 114. FIG. [Figure 4] 13 is a diagram showing an example of temperature information and humidity information temporarily stored in the memory of the terminal control unit 114. FIG. [Diagram 5] FIG. 13 is a diagram showing an example of offset xy coordinates in which a certain region is the range of a plane rectangular coordinate system. [Figure 6] 13A and 13B are diagrams showing specific examples of correspondence between position information expressed in latitude and longitude, converted xy coordinates, offset xy coordinates, and a correspondence between a starting point position and a difference. [Figure 7] 13 is a diagram showing a specific example of sensor data (position information group) transmitted to the server 3. FIG. [Figure 8] FIG. 13 is a diagram illustrating an example of a data structure of an upstream message. [Figure 9] 13 is a diagram showing an example of the data structure of an upstream message generated when a moving object 1 ends its movement. FIG. [Figure 10] FIG. 4 is a diagram showing an example of an operation flow of the communication terminal device 11. [Figure 11] FIG. 13 is a diagram illustrating an example of a data structure of a downstream message. [Figure 12] FIG. 11 is a diagram illustrating an example of an operation flow of the server 3. [Figure 13] FIG. 13 is a diagram showing an example of a table used to determine communication quality information of an upstream message. [Figure 14] 1 is a diagram showing a schematic diagram of positions indicated by position information successively generated by a terminal control unit 114 on the movement route of a moving object 1. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention will be described below with reference to the drawings, in which: As shown in FIG.

[0022] The mobile object 1 includes not only a four-wheeled automobile that travels on a roadway, but also two-wheeled automobiles, bicycles, aircraft that travel in the air, ships that travel on water, and the like. It also includes unmanned mobile objects with no people on board. Although not shown, the mobile object 1 is equipped with a position sensor that uses signals emitted from a group of GNSS (Global Navigation Satellite System) satellites 4 to determine the current position of the mobile object 1. Each satellite of the group of GNSS satellites 4 constantly transmits a signal including the position information of each satellite and the time information of transmission. Although not shown, there are a plurality of mobile objects 1 and communication terminal devices 11 mounted on the mobile object 1.

[0023] The LPWA communication network 2 is a communication network for LPWA communication, and is composed of multiple base stations and a cloud system. LPWA communication is a communication method that realizes wide-range communication with low power consumption. For example, communication methods such as SIGFOX (registered trademark) and LoRa (registered trademark) are applicable.

[0024] The multiple base stations constituting the LPWA communication network 2 are installed so that each covers a predetermined area. The LPWA communication network 2 is a network that connects message exchanges between a communication terminal device 11 that transmits radio signals of the LPWA communication method and a server 3 connected to the LPWA communication network 2. When the LPWA communication network 2 receives an upstream message wirelessly from the communication terminal device 11, it determines communication quality information corresponding to the upstream message based on the received signal strength and the number of base stations that have been wirelessly received. The communication terminal device 11 transmits the communication quality information in response to a request from the server 3.

[0025] The server 3 is connected to the LPWA communication network 2, and receives upstream messages transmitted from the communication terminal device 11 via the LPWA communication network 2. The server 3 transmits downstream messages to the communication terminal device 11 via the LPWA communication network 2.

[0026] A description will now be given of the functional configuration of the server 3. The server 3 includes at least a server communication unit 31, a server control unit 32, and a server storage unit 33. Note that the server 3 may be constructed with a plurality of computers in order to distribute the processing load.

[0027] The server communication unit 31 is composed of a server receiving unit 311, an acquiring unit 312, and a server transmitting unit 313. The server receiving unit 311 sequentially receives upstream messages transmitted from the communication terminal device 11 via the LPWA communication network 2. The acquiring unit 312 acquires communication quality information generated by the LPWA communication network 2 by making a request to the LPWA communication network 2. The server transmitting unit 313 transmits downstream messages generated by the server control unit 32 to the communication terminal device 11 via the LPWA communication network 2.

[0028] The server control unit 32 is configured with a CPU and a memory as hardware. The server control unit 32 sequentially stores the upstream messages sequentially received by the server receiving unit 311 in the server storage unit 33 in association with the identification information included in the upstream messages.

[0029] The server control unit 32 includes a reception history information generating unit 321. The reception history information generating unit 321 has a function of generating reception history information indicating whether the reception was successful or not based on a sequence number included in the upstream message stored in the server storage unit 33 when the server reception unit 311 receives an upstream message including behavior information indicating the end of movement of the moving object 1.

[0030] The server control unit 32 performs downstream message generation decision processing to decide whether or not to generate a downstream message based on reception history information, communication quality information, the time elapsed since the previous transmission of a downstream message, and the like, which will be described later.

[0031] The server storage unit 33 is configured as hardware such as a large-capacity storage medium, such as a hard disk drive. Under the control of the server control unit 32, the server storage unit 33 sequentially stores the upstream messages received in association with the identification information. The server storage unit 33 stores various programs for controlling the server 3. For example, the server storage unit 33 stores a program for performing downstream message generation determination processing.

[0032] The following describes the functional configuration of the communication terminal device 11. The communication terminal device 11 includes at least an external I / F 111, a terminal communication unit 112, a history storage unit 113, a terminal control unit 114, a conversion unit 115, a detection unit 116, and an auxiliary battery 117, as shown in FIG.

[0033] The external I / F 111 is connected to various external sensors and has a function of receiving input information from the various sensors. The various sensors are, for example, a position sensor, a temperature sensor, a humidity sensor, an air pressure sensor, an acceleration sensor, a gyro sensor, etc. The input information from the various sensors is position information obtained by positioning the position sensor, temperature information obtained by measuring the temperature sensor, humidity information obtained by measuring the humidity sensor, air pressure information obtained by measuring the air pressure sensor, and acceleration information measured by the acceleration sensor or gyro sensor.

[0034] The various sensors perform sequential positioning and measurement at a predetermined time interval. The time interval for positioning and measurement can be set arbitrarily. The external I / F 111 sequentially inputs various information received from the various external sensors to a conversion unit 115 included in the terminal control unit 114. The various sensors may be built into the communication terminal device 11. In this case, the various sensors may be directly connected to the terminal control unit 114 without going through the external I / F 111.

[0035] The terminal communication unit 112 has a function of performing wireless communication with the LPWA communication network 2 based on the LPWA communication system. The data structures of the upstream messages to be transmitted and the downstream messages to be received will be described later.

[0036] When the terminal communication unit 112 transmits an upstream message generated by the terminal control unit 114, the history storage unit 113 has a function of storing the upstream message in the order in which it was transmitted, under the control of the terminal control unit 114. When the server 3 is unable to receive an upstream message, it transmits a downstream message including reception history information for resending the corresponding upstream message. By acquiring the reception history information from the server 3, the terminal control unit 114 can identify the corresponding upstream message from the history storage unit 113 based on the reception history information and resend it.

[0037] The terminal control unit 114 is configured as hardware including a CPU and a memory, and controls the overall operation of each functional unit of the communication terminal device 11. A control program for controlling the operation of the communication terminal device 11 is stored in the memory of the terminal control unit 114.

[0038] The terminal control unit 114 generates an upstream message including the sensor data of the various sensors converted by the conversion unit 115. Furthermore, when the terminal communication unit 112 wirelessly receives a downstream message transmitted from the server 3, it performs a retransmission control process based on the reception history information included in the downstream message.

[0039] The conversion unit 115 has a function of converting various information input from the external I / F 111 into sensor data. The sensor data refers to data obtained by processing input information from various sensors into a size suitable for an upstream message in LPWA communication, which has a data length restriction. An example of input information from various sensors converted by the conversion unit 115 is shown in Figs. 3 and 4.

[0040] As shown in Fig. 3, the terminal control unit 114 temporarily stores the location information input from the external I / F 111 at a predetermined time interval in the memory of the terminal control unit 114 in the order of acquisition. Also, as shown in Fig. 4, the temperature information and humidity information input from the external I / F 111 at a predetermined time interval in the memory in the order of acquisition. In this embodiment, the location information from the position sensor is acquired at two and a half minute time intervals and temporarily stored in the memory.

[0041] The terminal control unit 114 stores in memory the position information sequentially input from the external I / F 111 from when the detection unit 116 detects that the ACC power supply of the moving object 1 is turned on until when the detection unit 116 detects that the ACC power supply is turned off. However, when the difference information indicating the difference from the reference position is 0 or smaller than a predetermined value, or when the differences are the same value, the moving object 1 is staying in approximately the same position, so duplicate position information will be transmitted to the server 3. The terminal control unit 114 stops storing such position information in memory. Therefore, the position information acquired while the moving object 1 is stopped is not included in the position information group of the sensor data. Note that sensor information other than the position information (information on temperature, humidity, air pressure, etc.) may be stored in memory regardless of whether the ACC power supply is on or off.

[0042] The detection unit 116 has a function of managing the power supply of the communication terminal device 11. The communication terminal device 11 receives power supply from the ACC power supply of the moving object 1, and has a function of detecting whether the ACC power supply of the moving object 1 is in an on state or an off state. In this embodiment, the terminal control unit 114 judges the behavior of the moving object 1 when the ACC power supply is in an on state as the "start of movement" of the moving object 1. Also, the terminal control unit 114 judges the behavior of the moving object 1 when the ACC power supply is in an off state as the "end of movement" of the moving object 1. The terminal control unit 114 judges the behavior of the moving object 1 from when the ACC power supply is in an on state to when the ACC power supply is in an off state as the "moving" state, and judges the behavior of the moving object 1 from when the ACC power supply is in an off state to when the ACC power supply is in an on state as the "stopped" state. The detection unit 116 may detect the on / off state of the ignition switch in addition to the on / off state of the ACC power supply.

[0043] The detection unit 116 charges the auxiliary battery 117 while receiving power supply from the ACC power supply of the moving object 1. When the ACC power supply of the moving object 1 is turned off, the detection unit 116 stops charging the auxiliary battery 117 and receives power supply from the auxiliary battery 117. Note that the detection unit 116 may always receive power supply from the moving object 1, or may determine the start and end of movement of the moving object by detecting the on / off state of the ACC power supply.

[0044] The auxiliary battery 117 is a rechargeable battery. The auxiliary battery 117 charges while it is receiving power from the ACC power source of the moving object 1. When the power supply from the detection unit 116 stops, the auxiliary battery 117 starts discharging and supplies power that can drive the communication terminal device 11 for a predetermined time.

[0045] Here, a method of converting the position information performed by the conversion unit 115 will be described. As shown in Fig. 3, the position information received by the external I / F 111 from the position sensor is information expressed in latitude and longitude. The conversion unit 115 converts the position information expressed in latitude and longitude into information expressed in planar rectangular coordinates with a predetermined position as a reference position. The position information expressed in latitude and longitude is 8 bytes. By converting the position information expressed in latitude and longitude into information expressed in planar rectangular coordinates, the data size can be compressed to 4 bytes.

[0046] There are various known methods for converting position information expressed in latitude and longitude into x and y coordinates in a plane rectangular coordinate system. In this modified example, the following formula is used as an example:

[0047]

number

number

[0048] The offset values ​​in the constant region shown in FIG. 5 are 894000 for x and 371160 for y.

[0049] The location information of acquisition sequence 1 shown in Figure 6 is expressed in longitude and latitude and is (34°40'50.5"N 135°10'35.7"E). When this location information is converted to planar rectangular coordinates using equations (1) and (2), the value (918018, 416472) is obtained. By subtracting the offset value from the obtained planar rectangular coordinates, the offset coordinates (24018, 45312) are obtained.

[0050] The maximum value of each of the x and y coordinates of the offset coordinates is 65535. That is, the x and y coordinates of the offset coordinates can each be expressed in 2 bytes (16 bits = 0 to 65535). In other words, by converting the location information expressed in longitude and latitude into offset coordinates, the data size can be compressed to 4 bytes. Furthermore, if the offset coordinates are expressed by calculating the difference from the coordinates of the starting position, the x and y coordinates of the offset coordinates can each be expressed in 1 byte (1 bit is +-, 7 bits = 0 to 127). In other words, they can be expressed in a total of 2 bytes.

[0051] The position information of acquisition order 2 shown in Figure 6 is (34°41'06.2"N 135°10'49.7"E). The offset coordinates obtained by converting the position information of acquisition order 2 using equations (1) and (2) and the offset value are (24030, 45296). If the position of acquisition order 1 is taken as starting position 1 and the positions of acquisition orders 2, 3, and 4 acquired following acquisition order 1 are expressed as difference information from the offset coordinates of starting position 1, the position of acquisition order 2 is (12, -16), the position of acquisition order 3 is (54, -41), and the position of acquisition order 4 is (52, -45).

[0052] The position of acquisition order 3 may be expressed as a difference from the position of acquisition order 2.

[0053] 7, the terminal control unit 114 generates sensor data (position information group) including a sequence number indicating the transmission order, behavior information, origin position information, and differences 1 to 3 as the payload of an upstream message. The sequence number is information indicating the transmission order, and the terminal control unit 114 assigns numbers from 0 to 64 incremented by 1 in sequence as the sequence number. After assigning 64 as the sequence number, the terminal control unit 114 assigns 0 as the next sequence number.

[0054] As an example of the payload of an upstream message, the terminal control unit 114 generates sensor data by adding a sequence number 39 and behavior information indicating that the moving object 1 is moving to the above-mentioned group of location information acquired in the order of acquisition 1 to 4, as shown in FIG. 7.

[0055] The data structure of an upstream message is, as shown in Fig. 8, a 10-byte header, a maximum 12-byte payload, and a 4-byte footer. The payload is composed of 2-byte data including a sequence number and behavior information, 4-byte offset coordinates of a starting point position as first position information, and sensor data as a group of position information including three pieces of 2-byte difference information indicating the difference between the first position and the second position, that is, the difference between the starting point position and each of the subsequent positions. The 10-byte header includes identification information (4 bytes) for identifying the communication terminal device 11 from other communication terminal devices 11. The 4-byte footer includes a hash-based message authentication code (HMAC) as an authentication code, and a cyclic redundancy check (CRC) as an error detection code.

[0056] Here, it is assumed that the detection unit 116 detects that the ACC power supply of the moving object 1 is turned off between the acquisition of the location information of the acquisition order 5 and the acquisition of the location information of the acquisition order 6. In this case, the terminal control unit 114 generates an upstream message including behavior information indicating "movement end", the offset coordinates of the acquisition order 5 as the movement end position of the moving object 1, and history information indicating the number of upstream messages stored in the history storage unit 113. A specific example of the payload of the upstream message is the sensor data of sequence number 40 in FIG. 7.

[0057] 9, the payload of the upstream message generated by the terminal control unit 114 at the end of the movement of the moving object 1 is composed of a sequence number and behavior information (2 Bytes), location information at the end of the movement (4 Bytes), and history information (1 Byte). The history information may be information expressed as a ratio to the storable capacity, or may be the number of upstream messages.

[0058] The operation of the retransmission control process of the communication terminal device 11 will be described with reference to Fig. 10 and Fig. 11. Note that the symbol "S" used in the description of the operation flow means a step. As shown in Fig. 10, when the detection unit 116 of the communication terminal device 11 detects that the ACC power supply of the moving object 1 has been turned on (S1: Yes), the conversion unit 115 converts the location information sequentially acquired from the location sensor via the external I / F 111 into sensor data (S2).

[0059] The terminal control unit 114 generates an upstream message including behavior information indicating the start of movement and the sensor data converted by the conversion unit 115 in S2, and causes the terminal communication unit 112 to wirelessly transmit the generated upstream message (S3). After that, when the detection unit 116 detects that the ACC power supply of the moving object 1 has been turned off (S4: Yes), the terminal control unit 114 stops storing the position information sequentially acquired via the external I / F 111 (S5).

[0060] In other words, the location information acquired between when the moving body 1 stops moving and when it starts moving again is not included in the sensor data wirelessly transmitted to the server 3, so the communication terminal device 11 can reduce the wireless transmission of duplicated location information that occurs when the moving body 1 is stopped.

[0061] Next, the terminal control unit 114 generates an uplink message including behavior information indicating the end of the movement of the mobile object 1, history information, and location information at the time of the end of the movement, and causes the terminal communication unit 112 to wirelessly transmit the generated uplink message (S6). The terminal communication unit 112 wirelessly transmits the uplink message by LPWA communication method. The LPWA communication network 2 wirelessly receives the uplink message wirelessly transmitted from the communication terminal device 11, but depending on the environment when the communication terminal device 11 wirelessly transmits the uplink message, it may not be possible to receive the message. For example, this may occur when the mobile object 1 is moving at high speed, when it enters a tunnel, or when there is a large obstruction between the communication terminal device 11 and the base station of the LPWA communication network 2, such as in a mountainous area.

[0062] After the process of S6, when the terminal communication unit 112 wirelessly receives a downlink message (S7: Yes), the terminal control unit 114 checks the reception history information included in the wirelessly received downlink message (S8).

[0063] As shown in Fig. 11, a downstream message is composed of a header (17 bytes), payload (8 bytes), and footer (4 bytes). The payload contains 64 bits of reception history information. The bit sequence of the reception history information corresponds to the sequence number of the upstream message not received by server 3. For example, if upstream messages with sequence numbers 22 and 24 are not received, the 22nd and 24th bits in the bit sequence of the reception history information are set to 1. If the upstream message not received by server 3 is 0, the bit sequence of the reception history information is all 0.

[0064] The sequence number of an upstream message not received by server 3, which is indicated by the reception history information, may be expressed as a numerical position counting backward from the sequence number included in the most recent upstream message received. For example, suppose that the sequence number included in the most recent upstream message is "100", and the upstream messages with sequence numbers "76" and "78" were not received. In this case, the bit sequence of the reception history information will be information in which the 22nd and 24th bits are set to 1.

[0065] If the terminal control unit 114 checks the reception history information included in the downstream message in S8 and identifies an upstream message not received by the server 3 with a bit set to 1 (S9: Yes), it reads out the upstream message with the corresponding sequence number from the history storage unit 113 and causes the terminal communication unit 112 to resend it (S10). If the reception history information in S9 does not contain an upstream message not received by the server with a bit set to 1 (S9: No), the process proceeds to S12.

[0066] After performing the process of S10, if the server 3 confirmed in the reception history information has resent all of the unreceived uplink messages (S11: Yes), the terminal control unit 114 proceeds to the process of S12. If the server 3 confirmed in the reception history information has not yet completed resending the unreceived uplink messages (S11: No) in S11, the terminal control unit 114 returns to the process of S10 and resends the corresponding uplink messages.

[0067] In the process of S12, the terminal control unit 114 deletes all upstream messages stored in the history storage unit 113. That is, the terminal control unit 114 deletes all upstream messages stored in the history storage unit 113, regardless of whether there are any upstream messages that have not been received by the server 3. When the terminal control unit 114 deletes all upstream messages stored in the history storage unit 113, it resets the sequence numbers assigned to the upstream messages to 0.

[0068] If the terminal communication unit 112 does not wirelessly receive a downlink message after the process of S6 (S7: No), the process proceeds to the process of S1.

[0069] In the processing of S4, if the detection unit 116 does not detect that the ACC power supply of the moving body 1 has been turned off (S4: No) and the regular timing for wirelessly transmitting an uplink message arrives (S13: Yes), the terminal control unit 114 generates an uplink message and causes the terminal communication unit 112 to wirelessly transmit the generated uplink message (S14).

[0070] The regular timing is, for example, 10 minutes and 20 seconds. In this case, the position sensor measures the position information every 155 seconds, and the terminal control unit 114 generates an uplink message including four groups of position information at the fourth position measurement, and causes the terminal communication unit 112 to wirelessly transmit the generated uplink message. After the process of S14, the terminal control unit 114 returns to the process of S4. In the process of S13, if it is not the regular timing for wirelessly transmitting the uplink message (S13: No), the terminal control unit 114 returns to the process of S4.

[0071] The operation of the server 3 will be described with reference to Fig. 12. When the server receiving unit 311 receives an upstream message from the communication terminal device 11 via the LPWA communication network 2 (S21: Yes), the server control unit 32 stores the upstream message in the server storage unit 33 (S22).

[0072] Next, if the behavior information included in the received upstream message is behavior information indicating the end of movement (S23: Yes), the server control unit 32 uses the identification information included in the upstream message as a key to check the sequence number of the upstream message containing the same identification information stored in the server memory unit 33.

[0073] The server control unit 32 generates reception history information of a 64-bit array in which the value of the corresponding bit position is set to 0 if there is a sequence number, and in which the value of the corresponding bit position is set to 1 if there is no sequence number (S24). In the process of S23, if the behavior information included in the received upstream message is not behavior information indicating the end of movement (S23: No), the server control unit 32 returns to the process of S21.

[0074] Next, the server control unit 32 acquires communication quality information indicating the communication quality of the uplink message received from the LPWA communication network 2 (S25). The LPWA communication network 2 determines the communication quality information using table information shown in Fig. 13. The communication quality information is determined by the value of received signal strength (RSSI: Received Signal Strength Indicator) and the number of base stations that wirelessly received the uplink message.

[0075] For example, if the received signal strength of the upstream message is -122 dBm or more and the number of base stations that wirelessly received the same upstream message is three, the LPWA communication network 2 determines the communication quality information to be a value of 4, which indicates that the communication quality is in the best state, and transmits it to the server 3. For example, if the received signal strength of the upstream message is -135 dBm or less, the LPWA communication network 2 determines the communication quality information to be a value of 1, which indicates that the communication quality is in the worst state, and transmits it to the server 3.

[0076] The server control unit 32 comprehensively determines whether it is appropriate to transmit a downstream message based on various determination factors such as reception history information, communication quality information, history information, the time elapsed since the previous transmission of a downstream message to the present time, whether past retransmissions have been received successfully, and a predicted stopping time of the mobile unit 1, and determines whether to generate a downstream message (S26). For example, the server control unit 32 determines whether to generate a downstream message using a trained model trained by machine learning using a known CART (Classification And Regression Tree) algorithm.

[0077] For example, suppose that there are two unreceived uplink messages from the reception history information, the communication quality information is 3, the history information is 40%, the reception success rate of past retransmissions is 90%, and the predicted stopping time of the mobile unit 1 is 1 minute. The server control unit 32 inputs these decision factor information into the trained model and determines whether or not to generate a downlink message.

[0078] When the server control unit 32 determines in the process of S26 to transmit a downstream message (S27: Yes), it generates a downstream message and causes the server transmission unit 313 to transmit the downstream message (S28). After the process of S28, the server control unit 32 returns to the process of S21.

[0079] When the server control unit 32 determines in the process of S27 not to generate a downstream message (S27: No), the process returns to the process of S21.

[0080] Although the embodiment of the present invention has been described above, the functional configurations and processes of the communication terminal device 11 and the server 3 are not limited to the above embodiment.

[0081] For example, the communication terminal device 11 may wirelessly transmit measured temperature information, humidity information, atmospheric pressure information, or acceleration information to the server 3 as sensor data instead of location information, and if there is an unreceived uplink message, perform a similar retransmission control process.

[0082] If the ACC power supply of the moving object 1 is on but there is little change in the position information successively acquired by the position sensor, it is assumed that the moving object 1 is caught in traffic or has stopped moving with the engine running. Even in such a case, the terminal control unit 114 may determine that the moving object 1 has stopped moving and wirelessly transmit an uplink message including behavior information to that effect to the server 3.

[0083] In the above embodiment, the position sensor of the communication terminal device 11 measures its location at regular intervals to generate position information, and the terminal communication unit 112 compiles multiple pieces of position information in the order in which they were generated, stores them in one upstream message, and transmits them to the server 3. However, the terminal control unit 114 may select the position information to be transmitted, and store only the selected position information in the upstream message.

[0084] For example, as shown in FIG. 14, on the route traveled by the moving body 1 from the start position to the goal position, the terminal control unit 114 may select and transmit the position information [2], [6], and

[10] which are turning points from among the position information [1] to

[11] successively generated.

[0085] As a method for identifying location information that is a turning point, for example, a turning point may be identified when the angle formed by a first vector composed of consecutive first and second location information and a second vector composed of vectors of consecutive second and third location information is greater than a predetermined angle (e.g., 45 degrees, 60 degrees, 90 degrees, etc.).

[0086] The present invention can be embodied by modifying the components without departing from the spirit and scope of the present invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments.

[0087] The present invention may be, for example, a combination of all the components shown in the embodiments, or a combination of additional components. The present invention may be a communication terminal device constituting a remote system, or a retransmission control method for an upstream message used in the communication terminal device. The present invention may also be a program that causes the communication terminal device to execute a retransmission control process for an upstream message.

[0088] Needless to say, various modifications and applications are possible without departing from the spirit and scope of the invention. [Industrial Applicability]

[0089] The present invention can be applied to a remote system in which a server manages sensor data from various sensors in a mobile object using a communication terminal device equipped with an LPWA communication function. [Explanation of symbols]

[0090] 1. Mobile 2 LPWA communication network 3 Server 4 GNSS satellite constellation 11. Communication terminal equipment 31 Server Communication Department 32 Server control unit 33 Server memory section 311 Server Reception Unit 312 Acquisition Department 313 Server transmission unit 321 Reception history information generation unit 111 External I / F 112 Terminal communication unit 113 History memory section 114 Terminal control unit 115 Conversion unit 116 Detection unit 117 Auxiliary Battery

Claims

1. A remote system including a communication terminal device mounted on a mobile object, an LPWA communication network, and a server, The communication terminal device A detection unit that detects whether a power source of the mobile object is on or off; A conversion unit that converts information sequentially acquired by a predetermined sensor into sensor data; a terminal control unit that generates an upstream message including identification information for identifying the communication terminal device, a sequence number indicating a transmission order, behavior information indicating a behavior of the moving object based on the on / off of the power supply detected by the detection unit, and the sensor data; a terminal communication unit that wirelessly transmits the upstream message to the LPWA communication network; a history storage unit that sequentially stores the upstream messages wirelessly transmitted by the terminal communication unit, the terminal control unit generates the upstream message including the behavior information indicating an end of movement of the moving object and history information indicating the number of the upstream messages stored in the history storage unit when the detection unit detects that the power supply has been turned off; The server, a server receiving unit for receiving the upstream message from the terminal communication unit via the LPWA communication network; a server storage unit for storing the received upstream message; a reception history information generating unit that generates reception history information indicating whether reception was successful or not based on the sequence number included in the upstream message stored in the server storage unit when the server reception unit receives the upstream message including the behavior information indicating the end of movement of the moving object; an acquisition unit for acquiring communication quality information corresponding to the upstream message; a server control unit that determines whether or not to generate a downstream message including the reception history information based on the reception history information, the history information, and the communication quality information; a server transmission unit that transmits the downstream message generated by the server control unit to the terminal communication unit via the LPWA communication network when the server control unit determines to generate the downstream message; when the terminal communication unit receives the downlink message, the terminal control unit specifies the sequence number of the uplink message not received by the server from the reception history information included in the downlink message, reads out the uplink message having the specified sequence number from the history storage unit, and causes the terminal communication unit to retransmit the uplink message. Remote system.

2. 2. The remote system according to claim 1, wherein the server control unit further determines whether or not to generate the current downstream message based on an elapsed time from transmitting the previous downstream message to a current time.

3. The sensor sequentially acquires location information indicating a location where the moving object was present; the conversion unit calculates difference information indicating a difference between a first position and a second position based on the plurality of pieces of position information sequentially acquired by the sensor, and converts the pieces of position information into the sensor data including information indicating the first position and the difference information. A remote system according to claim 1 or claim 2.

4. The sensor acquires the location information expressed in latitude and longitude; The conversion unit converts the position information sequentially acquired by the sensor into the sensor data expressed in x and y coordinates with a predetermined position as a reference position. The remote system of claim 3.

5. A communication terminal device mounted on a moving object, A detection unit that detects whether a power source of the mobile object is on or off; A conversion unit that converts information sequentially acquired by a predetermined sensor into sensor data; a terminal control unit that generates an upstream message including identification information for identifying the communication terminal device, a sequence number indicating a transmission order, behavior information indicating a behavior of the moving object based on the on / off of the power supply detected by the detection unit, and the sensor data; a terminal communication unit that communicates with a server by wirelessly transmitting the upstream message to a LPWA communication network and wirelessly receiving the downstream message from the LPWA communication network; a history storage unit that stores the upstream message wirelessly transmitted by the terminal communication unit, the downstream message includes reception history information indicating whether reception was successful or not based on the sequence number included in the upstream message received by the server, The terminal control unit when the detection unit detects that the power supply has been turned off, the detection unit generates the upstream message including the behavior information indicating the end of movement of the moving object and history information indicating the number of the upstream messages stored in the history storage unit, and wirelessly transmits the upstream message to the terminal communication unit; When the terminal communication unit receives the downstream message, the server identifies the sequence number of the upstream message not received from the reception history information included in the downstream message; reading out the upstream message having the specified sequence number from the history storage unit and causing the terminal communication unit to retransmit the upstream message; A communication terminal device comprising:

6. The communication terminal device described in Claim 5, wherein the terminal control unit further reads out the upstream message of the identified sequence number from the history memory unit, resends it to the terminal communication unit, and then deletes all of the upstream messages stored in the history memory unit.

7. A communication terminal device mounted on a moving object and equipped with a CPU and a memory, A detection unit that detects whether a power source of the mobile object is on or off; A conversion unit that converts information sequentially acquired by a predetermined sensor into sensor data; a terminal control unit that generates an upstream message including identification information for identifying the communication terminal device, a sequence number indicating a transmission order, behavior information indicating a behavior of the moving object based on the on / off of the power supply detected by the detection unit, and the sensor data; a terminal communication unit that communicates with a server by wirelessly transmitting the upstream message to the LPWA communication network and wirelessly receiving the downstream message from the LPWA communication network; a program for making the terminal communication unit function as a history storage unit that stores the uplink message wirelessly transmitted by the terminal communication unit, and for making the communication terminal device execute a retransmission control process for the uplink message, the downstream message includes reception history information indicating whether reception was successful or not based on the sequence number included in the upstream message received by the server, The retransmission control process includes: generating and wirelessly transmitting the upstream message, the upstream message including the behavior information indicating an end of movement of the moving object and history information indicating the number of the upstream messages stored in the history storage unit, when the power off is detected; when the downstream message is received, the server identifies the sequence number of the upstream message not received from the reception history information included in the downstream message; retransmitting the upstream message having the identified sequence number from the history storage unit to the server; Programs including.

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