Communication method and communication terminal device

Abstract

To provide a communication method for including location information of a mobile body in an uplink message and transmitting it to a server by using a communication system with limitations on the number of times of communication and the capacity of wirelessly transmitted data.SOLUTION: A communication terminal device mounted on a mobile body sequentially calculates and acquires latitude and longitude information which is location information expressed in latitude and longitude, stores the latitude and longitude information in the acquired order, converts the stored latitude and longitude information into offset coordinates which are location information expressed in xy coordinates with a predetermined position as a reference position and have a smaller data size than the latitude and longitude information, and generates and transmits an upstream message including multiple offset coordinates together.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a technology for transmitting location information indicating the current location of a mobile object from a communication terminal device mounted on the mobile object to a server, and particularly to a communication method that is useful when using a communication system that has limitations on the number of communications and the amount of data that can be transmitted. [Background technology]

[0002] In recent years, various wireless communication standards have been put into practical use, and in particular, LPWA (Low Power Wide Area) communication, which covers a wide area with low cost and low power consumption, has attracted attention.

[0003] While LPWA communication has the above advantages, it also has limitations such as restrictions on the number of times wireless transmissions can be made, and the amount of data that can be wirelessly transmitted at one time is limited. For example, "Sigfox (registered trademark)," one type of LPWA communication, has a limit of up to 140 transmissions per day and a maximum of 12 bytes of data that can be wirelessly transmitted at one time.

[0004] For this reason, LPWA communication is generally adopted in systems that only need to wirelessly transmit information a few times a day, such as systems that detect the presence or absence of abnormalities in equipment and wirelessly transmit the presence or absence of abnormalities to a server (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-62311 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the low cost of LPWA communication is a major attraction, and there is a growing demand to apply LPWA communication to management systems that have previously been run using mobile phone networks.

[0007] For example, car leasing services that operate and manage many vehicles want to collect the mileage of leased vehicles on a server and use the information for vehicle maintenance. Until now, vehicle maintenance has been performed after a certain period of time has passed. However, depending on the vehicle's operating status, there are some vehicles that do not require maintenance even after the certain period has passed, and some vehicles that require maintenance before the certain period has passed. The information that serves as a guide to whether a vehicle requires maintenance is the mileage.

[0008] A vehicle's mileage is estimated by measuring the number of wheel rotations within the vehicle itself, but this value varies depending on the condition of the tires, tire size, etc. It is possible to obtain mileage information from the vehicle, but this requires additional work to connect to the ECU (Electronic Control Unit) that manages the vehicle's mileage.

[0009] Therefore, without taking on such hassle, a system can be considered in which the on-board device sequentially acquires the vehicle's location information using GNSS (Global Navigation Satellite System), and wirelessly transmits the acquired location information to a server, which then calculates the vehicle's mileage.

[0010] However, when using LPWA communication, which has a transmission limit, vehicle location information cannot be transmitted wirelessly frequently, so it is necessary to estimate a distance close to the vehicle's actual traveling distance from a limited number of location information.

[0011] The present invention aims to provide a communication method and a communication terminal device that transmits location information of a moving object such as a vehicle in an upstream message to a server using a communication method that has limitations on the number of communications and the amount of data that can be transmitted. [Means for solving the problem]

[0012] (1) In order to solve the above problem, one aspect of the present invention is a communication method for transmitting location information indicating the current location of a mobile body in an uplink message generated by a communication terminal device mounted on the mobile body, the communication terminal device comprising a location information acquisition unit, a memory, a terminal control unit, and a communication unit, the location information acquisition unit sequentially calculating and acquiring latitude and longitude information, which is the location information expressed in latitude and longitude, the terminal control unit storing the latitude and longitude information in the memory in the order acquired, converting the stored latitude and longitude information into offset coordinates, which is location information expressed in x and y coordinates with a predetermined position as a reference position and has a data size smaller than the latitude and longitude information, generating the uplink message containing multiple offset coordinates, and the communication unit transmitting the generated uplink message at a predetermined timing.

[0013] The communication method (1) above allows multiple pieces of mobile object location information to be sent together in an upstream message, so that even when a communication method with limitations on the number of communications and the amount of data that can be sent is used, the mobile object location information can be sent appropriately to the server.

[0014] (2) In the communication method of (1) above, the terminal control unit may further calculate the difference between first location information represented by the converted offset coordinates and second location information represented by the converted offset coordinates following the first location information, and generate the upstream message containing the first location information and the difference as offset coordinates representing the second location information.

[0015] The communication method (2) described above allows multiple pieces of mobile object location information to be sent together in an upstream message using differential data with even smaller data sizes, so that even when a communication method with limitations on the number of communications and the amount of data that can be sent is used, the mobile object location information can be sent appropriately to the server.

[0016] (3) In the communication method described in (1) or (2) above, the communication terminal device may further include a detection unit that detects the start and end of movement of the moving body, and the terminal control unit may further generate the upstream message containing behavior information representing the detected start or end of movement.

[0017] (4) In the communication method described in (3) above, after the detection unit detects the end of the movement and the communication unit transmits the upstream message carrying the behavior information indicating the end of the movement, the terminal control unit may stop operating until the detection unit detects the start of the movement.

[0018] (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, characterized in that it comprises: a location information acquisition unit that sequentially calculates and acquires latitude and longitude information, which is location information indicating the current location of the mobile body, expressed in latitude and longitude; a terminal control unit that converts the latitude and longitude information in the order of acquisition into offset coordinates, which is location information expressed in x and y coordinates with a predetermined position as a reference position and has a smaller data size than the latitude and longitude information, and generates an uplink message containing multiple offset coordinates; and a communication unit that transmits the generated uplink message at a predetermined timing. [Effects of the Invention]

[0019] The present invention makes it possible to appropriately transmit the location information of a mobile object to a server even when a communication method that has limitations on the number of communications and the amount of data that can be transmitted is used. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing the configuration of a travel distance estimation system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a functional configuration diagram of a communication terminal device according to the present embodiment. [Figure 3] 10 is a diagram showing an example of position information sequentially stored in memory 113. FIG. [Figure 4]10 is a diagram showing an example of position information stored in a storage unit 33. FIG. [Figure 5] FIG. 10 is a diagram illustrating an example of an operation flow of a travel distance estimation process according to the present embodiment. [Figure 6] 10A and 10B are diagrams for explaining an example of route candidates identified by the shortest route search method according to the embodiment; [Figure 7] FIG. 10 is a diagram showing an example of an operation flow of another travel distance estimation process according to the present embodiment. [Figure 8] FIG. 10 is a schematic diagram for explaining another travel distance estimation process according to the present embodiment. [Figure 9] FIG. 10 is a schematic diagram for explaining another travel distance estimation process according to the present embodiment. [Figure 10] FIG. 10 is a diagram showing an example of a location information transmission operation flow of the communication terminal device according to the present embodiment. [Figure 11] FIG. 10 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 12] 10A and 10B are diagrams showing specific examples of correspondence relationships between position information expressed in latitude and longitude, converted xy coordinates, offset xy coordinates, and a starting point position and a difference. [Figure 13] FIG. 10 is a diagram showing a specific example of an upstream message transmitted to the server 3. [Figure 14] FIG. 10 is a diagram illustrating an example of a data structure of an upstream message. [Figure 15] FIG. 10 is a diagram illustrating an example of an operation flow of the communication terminal device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 shows an example of the configuration of a travel distance estimation system according to this embodiment. The system is composed of a communication terminal device 11 mounted on a mobile object 1, a base station group 2, a server 3, and a GNSS satellite group 4.

[0022] The mobile object 1 is a mobile object capable of traveling on roadways. The mobile object 1 includes not only four-wheeled automobiles but also two-wheeled automobiles, bicycles, etc. The mobile object 1 also includes unoccupied mobile objects. The communication terminal device 11 mounted on the mobile object 1 has a location information acquisition function using GNSS and a Sigfox communication function, as will be described in detail later. The base station group 2 is a plurality of base stations capable of receiving radio waves based on the Sigfox communication method. The server 3 receives and collects information (data) identified from the radio waves received by the base station group 2. The GNSS satellite group 4 is a GNSS satellite group, and each satellite constantly transmits its location information and the time information it transmitted.

[0023] Although not shown, this system assumes that there are multiple mobile objects 1 and the communication terminal devices 11 mounted thereon. The base station group 2 is arranged so that the reception areas under the jurisdiction of each base station overlap. A technical feature adopted by Sigfox communication is space diversity. This means that instead of only one base station receiving Sigfox communication compatible radio waves, all base stations that are capable of receiving Sigfox communication receive the radio waves, and the server 3 manages the data received by each base station as a single piece of data.

[0024] The server 3 includes at least the following functional units: a server communication unit 31, a control unit 32, a storage unit 33, a route information storage unit 34, and a distance estimation unit 35. Although not shown, the server 3 is a computer group made up of multiple computers for the purpose of distributing the processing load.

[0025] The server communication unit 31 is composed of a communication module and the like. It has a function of sequentially receiving location information sequentially transmitted from the communication terminal device 11 via the base station group 2. The control unit 32 is composed of a CPU as hardware. The control unit 32 has a function of organizing the location information sequentially received by the server communication unit 31 and recording the location information in the storage unit 33 in the order of reception and in consecutive order.

[0026] The storage unit 33 is configured as hardware using a large-capacity storage medium such as a hard disk drive. The storage unit 33 stores the position information that is sequentially received under the control of the control unit 32. The storage unit 33 stores a program for estimating the travel distance of the moving object 1.

[0027] The route information storage unit 34 is configured as hardware in the form of a large-capacity storage medium such as a hard disk drive. The route information storage unit 34 stores so-called map data. The map data includes route information relating to routes (also called links) and intersections (also called nodes). The route information includes type information indicating the route type (for example, national road, prefectural road, expressway, general road, etc.), name information indicating the name of the route, as well as road width, cost, and location information of the route and intersections.

[0028] Cost is a numerical value that quantifies the "difficulty of travelling" of a route, and is an evaluation value used in route searches. There are various methods for determining cost, and different evaluation costs are generally used depending on the purpose of the search. For example, if you want to search for the shortest route, the length of the route will be a major evaluation factor in determining cost, but if you are searching for a route to reach your destination in the shortest time, not only distance but also road width, frequency of traffic congestion, etc. will be included as evaluation factors.

[0029] The distance estimation unit 35 is a functional unit that is virtually realized by the CPU executing a program. The distance estimation unit 35 has a function of estimating a value that is as close as possible to the actual traveled distance between two consecutive points, using the position information of two consecutive points recorded in the storage unit 33 and the route information stored in the route information storage unit 34. There are multiple methods for estimating the traveled distance according to the present invention. The specific operations of each distance estimation process will be described later.

[0030] 2 is a diagram showing an example of functional blocks of communication terminal device 11. Communication terminal device 11 includes at least a location information acquisition unit 111, a communication unit 112, a memory 113, a behavior detection unit 114, a terminal control unit 115, a detection unit 116, and an auxiliary battery 117.

[0031] The location information acquisition unit 111 has a function of receiving multiple pieces of location information and transmitted time information from each satellite, which is transmitted from the GNSS satellite group 4 at any time. If radio waves from the satellites can be received, that is, if the number of satellites that can be captured is four or more, the location information acquisition unit 111 can calculate and acquire location information indicating the location of the device itself using the information from these satellites. The location information acquisition unit 111 sequentially acquires location information every second, and the terminal control unit 115 controls so that the acquired location information is stored in the memory 113 in the order in which it was acquired.

[0032] 3 is a diagram showing an example of location information sequentially stored in memory 113. As shown in the diagram, terminal control unit 115 stores the latitude and longitude information calculated and acquired by location information acquisition unit 111 in memory 113 in the order in which it was acquired.

[0033] The communication unit 112 has a function of creating transmission data including location information in accordance with the Sigfox communication method. Since Sigfox imposes a limit on the number of communications per day (maximum 140 times), the communication unit 112 transmits location information by setting a cycle (interval) that matches the purpose and the limit on the number of communications. The transmission cycle of location information can be changed when an event is detected or by an instruction from the server 3.

[0034] In this embodiment, a transmission cycle in minutes, such as 4 minutes or 10 minutes, is set in the communication unit 112. For example, when a transmission cycle of 4 minutes is set, the communication unit 112 can transmit the location information to the server 3 15 times per hour, for approximately 9 hours. On the other hand, when transmission is set at 10 minutes intervals, the communication unit 112 can transmit the location information to the server 3 6 times per hour, for approximately 24 hours. The transmission cycle may be changed depending on the traveling state of the mobile object 1.

[0035] The mobile object 1 equipped with the communication terminal device 11 moves at an average speed ranging from 30 km to 60 km per hour, depending on the road conditions. In this case, the distance that the mobile object 1 moves in one minute is 500 m to 1 km. Therefore, if one piece of location information is sent every four minutes, the distance between the positions indicated by each successive piece of location information will be 2 km to 4 km. If the area that the mobile object 1 moves in is an urban area, there are many intersections, and if the range is 2 km to 4 km, the mobile object 1 may turn at multiple intersections in four minutes.

[0036] If the server 3 can acquire only a small amount of location information, it cannot identify at which intersection the moving object 1 turned. If the moving object 1 turns at multiple intersections, the distance between the positions indicated by the location information will be longer than the straight line connecting the positions. Thus, in order to estimate the travel distance close to the actual measurement, it is desirable that the communication terminal device 11 acquires as much location information as possible and sends it to the server 3.

[0037] However, Sigfox communication can only transmit a small amount of data at one time, only 12 bytes. Location information expressed in latitude and longitude has a data size of 8 bytes. With 8 bytes, Sigfox communication can only transmit one piece of location information wirelessly per transmission. As mentioned above, if location information is transmitted wirelessly at four-minute intervals, the distance between positions that can be obtained by server 3 will be 2 to 4 km, so depending on the area traveled, even if distance is estimated, there is a high possibility that the value will deviate significantly from the actual travel distance.

[0038] Here, the accuracy of the location information decreases, but the data size of the location information can be reduced to 6 bytes. Since Sigfox communication wirelessly transmits 12 bytes per transmission, two pieces of location information can be wirelessly transmitted in one wireless transmission with a data size of 6 bytes. In addition, by taking the difference between the two pieces of location information, the data volume of the location information can be compressed. In this case, for a single transmission capacity of 12 bytes, one piece of regular location information (6 bytes) and the difference information between the two pieces of location information (3 bytes x 2) can be wirelessly transmitted. Note that the accuracy of the location information will decrease, but it is also possible to compress it further.

[0039] By wirelessly transmitting two or three pieces of location information at four-minute intervals, it is possible to shorten the distance interval between each piece of location information used when estimating distance in the server 3. This makes it possible to estimate a number closer to the actually measured distance in the distance estimation process described below.

[0040] The communication unit 112 has a function of wirelessly transmitting a plurality of pieces of location information stored in the memory 113 to the server 3 in a lump.

[0041] There are several possible ways to select the multiple pieces of location information to send together. The location information is acquired sequentially by the location information acquisition unit 111 in units of seconds. Therefore, if the transmission interval for location information is four minutes, ideally 240 pieces of location information will be acquired in four minutes. However, depending on the satellite capture conditions, the location information may not be acquired correctly. When selecting three pieces of location information from this and transmitting them wirelessly, it is desirable that the distance between each piece of location information is appropriately separated, or that the location information at the time of an event is appropriately selected. Another possible method is to select the location information acquired at the time the behavior was detected when the behavior detection unit 114, which will be described later, detects the behavior of the mobile object 1.

[0042] Furthermore, when the difference between one piece of reference location information and the next piece of acquired location information is calculated, there may be cases where the difference information becomes 0 or a value close to 0. For example, this may occur when the mobile object 1 is stuck in traffic and is unable to move at all, or when the mobile object 1 is parked in a parking lot to rest. In such cases, since there is no change in distance and there is also a limit to the number of communications, it may be possible to perform control such that the location information is not wirelessly transmitted in the current cycle, but is wirelessly transmitted the next time there is a change in the location information.

[0043] When wirelessly transmitting location information to the server 3, the communication unit 112 assigns identification information that identifies that the communication terminal device 11 wirelessly transmitted the location information and a sequence number that indicates the order in which the location information was obtained. The identification information allows the server 3 to identify which communication terminal device wirelessly transmitted the location information. In addition, by assigning a sequence number, the server 3 can identify the order in which the location information is transmitted when retransmitting the location information.

[0044] The behavior detection unit 114 is configured as hardware such as an acceleration sensor or a gyro sensor, and has a function of detecting the behavior of the mobile object 1 equipped with the communication terminal device 11. Detectable behaviors of the mobile object 1 include acceleration, a change in the direction of movement of the mobile object 1, a sudden stop, a sudden start, a collision, a right turn or left turn at an intersection, and driving on a sloped road. When the behavior detection unit 114 detects such behavior, the terminal control unit 115 stores the detected behavior information in the memory 13 together with the position information acquired at the time of detection.

[0045] The terminal control unit 115 is configured as hardware with a CPU, and controls the overall operation of each functional unit of the communication terminal device 11. 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 from an ACC (Accessory) power supply of the mobile object 1, and has a function of detecting when the ACC power supply of the mobile object 1 is turned on or off. The detection unit 116 distributes power to the auxiliary battery 117. When the ACC power supply of the mobile object 1 is turned off, the detection unit 116 receives power supply from the auxiliary battery 117. The auxiliary battery 117 is a rechargeable battery. By receiving power distribution from the detection unit 116, the auxiliary battery 117 stores enough power to drive the communication terminal device 11 for a predetermined time even when the ACC power supply of the mobile object 1 is turned off.

[0046] The operation of the server 3 will now be described. Fig. 4 is a diagram showing an example of location information with sequence numbers stored in the storage unit 33. The server 3 performs processing to estimate the travel distance of the moving object 1 using the location information stored in the storage unit 33 at regular intervals or when requested. There are a number of optimal methods for estimating the traveled distance in the present invention. Among these, two methods for estimating the traveled distance that are expected to have particularly significant effects will be described below with reference to the drawings.

[0047] 5 is a diagram showing an example of the operation flow of the first travel distance estimation process. Note that the symbol "S" used in the explanation of the operation flow means a step. When a request for travel distance estimation process for the moving object 1 is received, the distance estimation unit 35 of the server 3 extracts two points of location information with consecutive sequence numbers to which identification information indicating the communication terminal device 11 mounted on the moving object 1 is assigned, and performs a route search between the two points (S1).

[0048] The route search method itself uses known techniques. For example, there is a shortest route search method that selects a combination of routes that minimizes the sum of the costs assigned to the routes. There are also several known algorithms for shortest route search methods. For example, there are the Dijkstra algorithm, the Bellman-Ford algorithm, and the A* algorithm.

[0049] FIG. 6 is a diagram illustrating an example of route candidates identified by a shortest route search method. In a known route search, when a route search is performed after determining a start point and an end point, multiple candidate routes that a mobile object 1 can take as the shortest route are presented, allowing the user to select one. In the travel distance estimation process of the present invention, a predetermined number (e.g., three) of candidate routes are extracted, and the distances of the extracted three candidate routes are added together to calculate an average value. Note that the server 3 may or may not display the route candidates shown in FIG. 6.

[0050] The benefits of the distance estimation process described above will be explained using Figure 6. When estimating the distance between points A and B shown in Figure 6, the straight-line distance between the two points is simply calculated to be 3.3 km. On the other hand, when three candidate routes between points A and B are identified using a shortest path search method, candidate 1 is 3.8 km, candidate 2 is 3.8 km, and candidate 3 is 4.1 km. The actual route traveled by mobile object 1 remains unknown from the location information. However, there is a high possibility that mobile object 1 will use one of the three candidate routes, or will travel by piecing together fragments of routes included in each candidate route.

[0051] The distance estimation unit 35 calculates the estimated distance as 3.9 km, which is the average value (average distance) of the sum of the distances of these three candidate routes (S2). By using the first travel distance estimation process, even if the actual travel route is unknown, it is possible to reduce large discrepancies by selecting multiple routes that are likely to have been traveled and taking the average value (average distance) of these.

[0052] 7 is a diagram showing an example of the operation flow of the second travel distance estimation process. The distance estimation unit 35 of the server 3 functions as the second distance estimation unit. When a request for travel distance estimation process for the mobile object 1 is received, two consecutive points of position information (A, B) to which identification information indicating the communication terminal device 11 mounted on the mobile object 1 is assigned are extracted, and a route close to the positions of these two points is extracted from the route information stored in the route information storage unit 34, and an intersection X close to the positions of A and B is identified from among the intersections connected to the route (S11).

[0053] Here, a method for identifying intersection X will be described with reference to Figures 8 and 9. In the schematic diagram of Figure 8, the solid line route connecting point A, intersection X1, intersection X3, intersection X5, and point B is the actual travel route of moving object 1. The travel distance of moving object 1 is 0.6 km between A and X1, 1 km between X1 and X3, 1.4 km between X3 and X5, and 1 km between X5 and B, totaling 4 km. In contrast, the distance between point A and point B in a straight line is approximately 2.8 km. In other words, it can be seen that simply connecting the acquired location information in a straight line will result in a significant difference from the actual distance.

[0054] 9 is a schematic diagram illustrating distance estimation using intersections identified by the second travel distance estimation process according to this embodiment. The distance estimation unit 35 extracts Y1 and Y2 as routes close to A, and Y5 and Y6 as routes close to B. Each of the routes Y1, Y2, Y5, and Y6 includes route position information. The distance estimation unit 35 compares the route position information of each of the routes Y1, Y2, Y5, and Y6 with the position information of points A and B to extract routes that are close to points A and B.

[0055] Next, the distance estimation unit 35 extracts intersections connected to routes Y1, Y2, Y5, and Y6. Route Y1 is connected to intersection X1. Route Y2 is connected to intersection X2. Route Y5 is connected to intersection X5. Route Y6 is connected to intersection X6.

[0056] The route information storage unit 34 stores intersection position information as route information for intersections X1, X2, X5, and X6. By comparing the position information of points A and B with the intersection position information of each intersection, it is possible to identify intersections whose intersection position information is closest to points A and B. In the example of FIG. 9, intersections X1 and X6 are identified as intersections closest to points A and B. As a result, the distance estimation unit 35 calculates an estimated distance of 3.4 km in total for the route including the identified intersections X1 and X6, since the distance between A and X1 is 0.6 km, the distance between X1 and X6 is 2.1 km, and the distance between X6 and B is 0.7 km (S12).

[0057] The advantages of the second mileage estimation process are explained below. In the first mileage estimation process, a route search function was used to identify multiple candidate routes. However, when the distance between two points is short and there are many road intersections, such as in urban areas, a route that would not normally be taken may be extracted as a candidate. This problem may also be caused by errors in the acquired location information. To solve this problem, it is desirable to use a different distance estimation method instead of the first mileage estimation process. By selectively using the first mileage estimation process and the second mileage estimation process depending on the area in which the mobile object 1 travels and the distance in the acquired location information, it is possible to reduce the discrepancy with the actual mileage.

[0058] Furthermore, the third travel distance estimation process may involve identifying a frequently used route as a route between two points in the acquired location information, and estimating the distance of the identified route as the distance between the two points. When the distance estimation unit 35 functions as the third distance estimation unit, the route information storage unit 34 may further store route information and frequency information indicating the frequency of route use in association with each other. Based on the location information of the two points stored in the storage unit 33, the distance estimation unit 35 extracts, from the route information storage unit 34, route information associated with the most frequently used usage frequency information, and estimates the route information as the distance between the two points.

[0059] The third mileage estimation process can be combined with the first mileage estimation process and the second mileage estimation process and used depending on the conditions to reduce the discrepancy with the actual mileage. That is, the control unit 32 may select the estimated distance estimated by the distance estimation unit 35 in the first mileage estimation process, the second estimated distance estimated by the second distance estimation unit in the second mileage estimation process, or the third estimated distance estimated by the third distance estimation unit, and use the selected distance as the distance between the two points.

[0060] A modified example of the operation of the communication terminal device 11 according to the present invention will be described with reference to FIG. 10. FIG. 10 is a diagram showing an example of a location information transmission operation flow of the communication terminal device 11. 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 (S21: Yes). The terminal control unit 115 stores movement start information indicating the start of movement as behavior information of the moving object 1 in the memory 113, in association with the location information acquired at the time of detection. The communication unit 112 wirelessly transmits the location information including the movement start information as behavior information as "on-time content" (S22). When the detection unit 116 detects that the ACC power supply of the moving object 1 has been turned off (S23: Yes), the terminal control unit 115 stores movement end information indicating the end of movement as behavior information of the moving object 1 in association with the location information acquired at the time of detection in the memory 113. The communication unit 112 wirelessly transmits the location information including the movement end information as behavior information as "off-time content" (S26).

[0061] When a predetermined time has elapsed and the regular timing arrives (S24: Yes), the communication unit 112 selects multiple pieces of location information stored in the memory 113, generates "regular content", and wirelessly transmits it to the server 3 (S25). The server 3 can determine that the distance from the location information including the movement start information to the location information including the movement end information is one travel route of the mobile object 1, and calculate an estimated distance.

[0062] The terminal control unit 115 may convert the location information expressed in latitude and longitude sequentially acquired by the location information acquisition unit 111 into information expressed in x and y coordinates with a predetermined position as a reference position, and transmit the converted information to the server 3. As described above, the data size of location information expressed in latitude and longitude is 8 bytes. By converting the location information expressed in latitude and longitude into information expressed in planar rectangular coordinates, the data size can be compressed to 4 bytes.

[0063] 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, as an example, the following formula is used:

[0064]

number

number

[0065] The offset values ​​in the fixed region shown in FIG. 11 are 894000 for x and 371160 for y.

[0066] The location information of acquisition order 1 shown in Figure 12 is expressed in longitude and latitude and is (34°40'50.5"N 135°10'35.7"E). When this location information is converted into plane rectangular coordinates using equations (1) and (2), the value (918018, 416472) is obtained. By subtracting the offset value from the obtained plane rectangular coordinates, the offset coordinates (24018, 45312) are obtained.

[0067] The maximum value for each of the x and y coordinates of the offset coordinates is 65535. In other words, 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 location information expressed in longitude and latitude into offset coordinates, the data length can be compressed to 4 bytes. Furthermore, if the offset coordinates are expressed as the difference from the coordinates of the starting point, 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.

[0068] The position information of acquisition order 2 shown in Figure 12 is (34°41'06.2"N 135°10'4 9.7"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 after acquisition order 1 are expressed as the difference 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).

[0069] The position of acquisition order 3 may be expressed as a difference from the position of acquisition order 2.

[0070] 13, the terminal control unit 115 generates, as the payload of an upstream message, sensor data (a group of position information) including a sequence number indicating the transmission order, behavior information, origin position information, and differences 1 to 3. The sequence number is information indicating the transmission order, and the terminal control unit 115 assigns numbers from 0 to 64 incremented by 1 in order as the sequence number. After assigning 64 as the sequence number, the terminal control unit 115 assigns 0 as the next sequence number.

[0071] As an example of the payload of an upstream message, the terminal control unit 115 generates data in which the sequence number 39 and behavior information indicating that the moving body 1 is moving are assigned to the location information group in acquisition orders 1 to 4 described above, as shown in FIG. 13.

[0072] As shown in Fig. 14, the data structure of an upstream message is a 10-byte header, a maximum 12-byte payload, and a 4-byte footer. The payload is composed of 2 bytes of data including a sequence number and behavior information, 4 bytes of offset coordinates of the origin position which is first position information, and sensor data which is a group of position information including three 2-byte differences between the origin position and each of the subsequent positions. The 10-byte header includes identification information (4 bytes) of the communication terminal device 11. The 4-byte footer also includes an authentication code, HMAC (Hash-based Message Authentication Code), and an error detection code, CRC (Cyclic Redundancy Check).

[0073] From the time when the detection unit 116 detects that the ACC power supply of the moving object 1 is turned on until the time when the detection unit 116 detects that the ACC power supply is turned off, the terminal control unit 115 stores the location information successively acquired by the location information acquisition unit 111 in the memory 113. However, if the difference information, which is the difference from the reference location, is 0 or smaller than a predetermined value, or if the differences are the same value, this means that the moving object 1 is staying in approximately the same location, and therefore duplicate location information will be sent to the server 3. The terminal control unit 115 does not include such location information in the location information group of the uplink message it generates.

[0074] The communication terminal device 11 performs transmission control processing of an uplink message in accordance with the operational flow shown in Fig. 15. The processing of S32 and S33 in the operational flow shown in Fig. 15 corresponds to the processing of S22 in the operational flow shown in Fig. 10, and the processing of S35 and S36 in the operational flow shown in Fig. 15 corresponds to the processing of S26 in the operational flow shown in Fig. 10.

[0075] When the detection unit 116 of the communication terminal device 11 detects that the ACC power supply of the mobile object 1 has been turned on (S31: Yes), the terminal control unit 115 stores the location information successively acquired by the location information acquisition unit 111 in the memory 113 (S32).

[0076] Next, the terminal control unit 115 generates an uplink message including a sequence number indicating the transmission order, movement start information indicating the start of movement as behavior information of the moving object 1 since the ACC power supply of the moving object 1 is on, and a location information group specifying multiple locations based on the acquired location information, and stores the generated message in the memory 113. The communication unit 112 wirelessly transmits the generated uplink message as "on-time content" (S33). Note that the uplink message including the movement start information may be transmitted immediately when the start of movement is detected, or may be transmitted at the timing when the uplink message including the location information group is generated.

[0077] Following the process of S33, when the detection unit 116 detects that the ACC power supply of the moving object 1 has been turned off (S34: Yes), the terminal control unit 115 stops storing the location information successively acquired by the location information acquisition unit 111 in the memory 113 (S35). Next, the terminal control unit 115 generates an uplink message including a sequence number indicating the transmission order, movement end information indicating the end of movement as behavior information of the moving object 1 since the ACC power supply of the moving object 1 is turned off, and a group of location information specifying multiple locations based on the acquired location information, and stores this in the memory 113. The communication unit 112 wirelessly transmits the generated uplink message as "off-time content" (S36). After performing the process of S36, the terminal control unit 115 terminates its operation.

[0078] In S34, if the detection unit 116 does not detect that the ACC power has been turned off (S34: No) and it is the regular timing for wirelessly transmitting an upstream message (S37: Yes), the terminal control unit 115 wirelessly transmits an upstream message generated based on the location information stored in memory 113 to the server 3 (S38). After the processing of S38, the terminal control unit 115 returns to the processing of S34. If it is not the regular timing in S37 (S37: No), the terminal control unit 115 returns to the processing of S34.

[0079] The terminal control unit 115 of this modified example does not store in the memory 113 the location information successively acquired by the location information acquisition unit 111 from the time when it detects that the ACC power supply of the moving object 1 has been turned off until it detects that the ACC power supply has been turned on.

[0080] In other words, the location information acquired between the time when the moving body 1 stops moving and the time when it starts moving again is not included in the uplink message sent to the server 3, so the communication terminal device 11 can reduce the transmission of duplicate location information that occurs when the moving body 1 is stopped and is not necessary for estimating the traveled distance.

[0081] The distance estimation unit 35 estimates the distance traveled by the moving object 1 based on the uplink message received from the communication terminal device 11. The x and y coordinates included in the uplink message can be converted into location information expressed in the original latitude and longitude. The distance estimation unit 35 estimates the distance between each position based on the converted location information.

[0082] Although the embodiments of the present invention have been described above, the functional configurations and processes of the communication terminal device 11 and the server 3 are not limited to the above-described embodiments.

[0083] For example, in the above embodiment, several events are considered. For example, if the change in the sequentially acquired location information is small or zero, it is assumed that the moving object 1 is stopped. In this case, the wireless transmission of the location information may be stopped, and wireless transmission may be resumed when the difference information of the sequentially acquired location information becomes zero or greater.

[0084] The present invention can be embodied by modifying the components within the scope of the gist of the present invention in the implementation stage. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments.

[0085] The present invention may be, for example, an appropriate combination of all the components shown in the embodiments, an appropriate combination of additional components, a communication terminal device constituting a mileage estimation system, an upstream message transmission method used in the communication terminal device, or a program that causes a computer to execute an upstream message transmission process.

[0086] It goes without saying that various modifications and applications are possible within the scope of the invention. [Industrial Applicability]

[0087] The present invention can be applied to a service in which location information of mobile objects is collected by a server. [Explanation of symbols]

[0088] 1. Mobile 2 base station group 3 Server 4 GNSS satellite constellation 11. Communication terminal equipment 31 Server Communication Department 32 Control Unit 33 Storage area 34 Route information storage unit 35 Distance estimation unit 111 Location information acquisition unit 112 Communications Department 113 memory 114 Behavior detection unit 115 Terminal control unit 116 Detection unit 117 Auxiliary Battery

Claims

1. A communication method using an LPWA communication method, which has limitations on the number of communications and the amount of data that can be sent in one wireless transmission, in which location information indicating the current location of a mobile object is transmitted in an uplink message generated by a communication terminal device mounted on the mobile object, the communication terminal device includes a location information acquisition unit, a memory, a terminal control unit, and a communication unit; the location information acquisition unit sequentially calculates and acquires latitude and longitude information, which is the location information expressed in latitude and longitude; The terminal control unit storing the latitude and longitude information in the memory in the order of acquisition; converting the latitude and longitude information in the order in which it was stored into offset coordinates, which are position information expressed in x-y coordinates with a predetermined position as a reference position, and which have a data size smaller than that of the latitude and longitude information and a data size that allows multiple pieces of position information to be stored in a single transmission data capacity of the LPWA communication method; calculating a difference between first position information represented by the converted offset coordinates and second position information represented by the converted offset coordinates subsequent to the first position information; generating the uplink message including the first location information and the difference as offset coordinates representing the second location information; the communication unit transmits the generated upstream message at a predetermined timing. A communication method comprising:

2. 2. The communication method according to claim 1, The communication method, wherein the terminal control unit stops the communication unit from transmitting the upstream message when the difference is zero.

3. A communication terminal device mounted on a mobile body that communicates using an LPWA communication method, which has limitations on the number of communications and the amount of data that can be sent in one wireless transmission, a location information acquisition unit that sequentially calculates and acquires latitude and longitude information, which is location information indicating a current location of the mobile object, and is expressed in latitude and longitude; a memory for storing the latitude and longitude information in the order of acquisition; a terminal control unit that converts the latitude and longitude information in the stored order into offset coordinates, which are position information expressed in x and y coordinates with a predetermined position as a reference position, and has a data size smaller than the latitude and longitude information and a data size that allows multiple pieces of position information to be stored in a single transmission data capacity of the LPWA communication method, calculates a difference between first position information expressed by the converted offset coordinates and second position information expressed by the converted offset coordinates subsequent to the first position information, and generates the uplink message that includes the first position information and the difference as offset coordinates that represent the second position information; a communication unit that transmits the generated upstream message at a predetermined timing; A communication terminal device characterized by:

Images