JP2005064687A - Data communication method of in-vehicle information terminal and in-vehicle information terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data communication method of an in-vehicle information terminal by which a data content suitable for a communication state can be distributed. <P>SOLUTION: When a request of data distribution from an in-vehicle machine 100 to an information distribution center 400 is given, the communication state of radio communication at that time is detected in the in-vehicle machine 100, and it is informed to the information distribution center 400 from the in-vehicle machine 100. The information distribution center 400 requests the data content corresponding to the communication state of a map distribution server 403, a route searching server 404 or a position information retrieval server 405 from a request reception server 402, and distributes returned data to the in-vehicle machine 100. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a system for distributing various types of information such as map data from an information distribution center to an in-vehicle information terminal.

  A system is known in which map data of various locations is stored in a database server, and map data in a requested range is distributed from the database server to the in-vehicle terminal. In this system, distribution of map data is performed mainly using wireless communication of a mobile phone (Patent Document 1).

JP-A-10-255022

  In wireless communication using a mobile phone, the line capacity changes depending on the communication state at that time, such as the connection state and communication method of the line. However, in the system of Patent Literature 1, map data having the same content is distributed using wireless communication of a mobile phone regardless of the difference in communication state. Therefore, depending on the communication state, the line capacity may be insufficient for the map data to be distributed.

The data communication method of the in-vehicle information terminal according to the invention of claim 1 transmits various requests from the information terminal mounted on the vehicle to the information distribution center, and transmits various data distributed from the information distribution center according to the contents of the request. Applied to the data communication method of the in-vehicle information terminal received by the information terminal using wireless communication and provided to the user. The information terminal transmits a request and detects the communication state of the wireless communication to the information distribution center. The contact and information distribution center changes the contents of the data to be distributed based on the communicated communication state.
According to a second aspect of the present invention, in the data communication method of the in-vehicle information terminal according to the first aspect, the communication state of the wireless communication detected by the information terminal includes at least one of a communication method, an exchange method, and a received electric field strength. .
According to a third aspect of the present invention, in the data communication method for the in-vehicle information terminal according to the second aspect, the switching method includes circuit switching and packet switching, and the information terminal determines the received electric field strength for each of the circuit switching and the packet switching. It is to detect.
According to a fourth aspect of the present invention, in the data communication method of the in-vehicle information terminal according to the third aspect, when the received electric field strength detected for packet switching is equal to or less than a predetermined value, the information terminal uses the wireless communication by circuit switching to distribute information. It receives various data distributed from the center.
An in-vehicle information terminal according to a fifth aspect of the present invention is the information terminal according to any one of the first to fourth aspects, comprising communication means for performing wireless communication and display means for displaying received data as an image.

  According to the present invention, when a data distribution request is made from the in-vehicle information terminal to the information distribution center, the communication state of the wireless communication is detected at the information terminal, and the information distribution center is notified. The information distribution center extracts the data contents corresponding to the communication state, and changes the data contents distributed to the information terminal. Since it did in this way, the data content suitable for a communication state can be delivered to an information terminal.

  An embodiment of a car navigation device to which an in-vehicle information terminal according to the present invention is applied will be described using the map information distribution system shown in FIG. A communication terminal 200 is connected to a car navigation device (hereinafter referred to as an in-vehicle device) 100 that is an embodiment of the present invention mounted on a vehicle 1. Communication terminal 200 is wirelessly connected to mobile communication network 300, and information distribution center 400 is connected to mobile communication network 300. Thus, the in-vehicle device 100 and the information distribution center 400 are connected via the communication terminal 200 and the mobile communication network 300. Note that a radio base station (not shown) is used when the mobile communication network 300 performs radio communication with the communication terminal 200. The wireless base stations can wirelessly communicate with the communication terminals 200 in a predetermined communication area around the wireless base stations, and are scattered throughout the country.

  The system in FIG. 1 transmits various requests from the in-vehicle device 100 to the information distribution center 400 by connecting the in-vehicle device 100 and the information distribution center 400 in this way. The information distribution center 400 distributes various data such as map data to the in-vehicle device 100 according to the request contents. The in-vehicle device 100 receives the distributed various data using wireless communication performed between the mobile communication network 300 and the communication terminal 200, and provides it to the user by image display or the like.

  Various mobile phones, PDAs (Personal Digital Assistance), and the like are used for the communication terminal 200, and various communication methods are used for communication with the mobile communication network 300 depending on the type. As this communication system, for example, a CDMA system capable of high-speed data communication, a TDMA system such as GSM or PDC, which is widely used in mobile phones, and an analog mobile phone are used. There is an FDMA system. In each communication method, two types of switching methods, circuit switching and packet switching, are used. Depending on the communication method, only one of the exchange methods may be supported. For example, in the case of the FDMA system, only data communication using a modem by circuit switching is supported.

  In circuit switching, after first establishing a communication line, data communication is performed in a state where the communication line is established. Therefore, it is necessary to secure a channel from the start to the end of communication. On the other hand, in packet switching, it is not necessary that data is sequentially transmitted divided into packet units and a channel is not always secured from the start to the end of communication. In general, packet switching enables data communication at a higher speed than circuit switching.

  The communication terminal 200 supports at least circuit switching when circuit switching is used for data communication in the communication method. Further, when the communication terminal 200 is compatible with packet communication, it is possible to select and use either circuit switching or packet switching by setting in advance by the user.

  The communication terminal 200 measures the received electric field strength of the radio wave transmitted from the mobile communication network 300 at a constant period, and outputs the result to the in-vehicle device 100. Even if the communication method is the same, different radio base stations may be used in the mobile communication network 300 if the exchange method is different. Therefore, the received electric field strength may differ depending on the exchange method. Therefore, when the communication terminal 200 also supports packet communication, the received electric field strength is measured for both circuit switching and packet switching, and the measurement result is output to the in-vehicle device 100.

  In addition to being used for connection between the in-vehicle device 100 and the information distribution center 400, the communication terminal 200 is connected to another communication terminal, a fixed telephone, or the like via the mobile communication network 300, and between them. Voice and various information can be transmitted and received. The connection between the in-vehicle device 100 and the communication terminal 200 is not limited to a wired connection using a cable or the like, and a wireless connection may be used.

  FIG. 2 is a system block diagram showing the configuration of the in-vehicle device 100. Hereafter, each structure is demonstrated in order. The current location detection device 101 that detects the current location of the vehicle 1 includes, for example, a gyro 101a that detects the traveling direction of the vehicle 1, a vehicle speed sensor 101b that detects a vehicle speed, a GPS sensor 101c that detects a GPS signal from a GPS satellite, and the like. The control circuit 102 includes a microprocessor and its peripheral circuits, and performs various controls by executing a control program stored in the ROM 103 using the RAM 104 as a work area.

  The image memory 105 stores image data to be displayed on the display monitor 106. This image data includes road map drawing data and various graphic data. The in-vehicle device 100 displays map information on the display monitor 106 by using the image data stored in the image memory 105 based on the map data transmitted from the information distribution center 400 of FIG. The display monitor 106 also displays various setting screens for the in-vehicle device 100, such as a setting screen for a communication terminal to be used. A touch panel is used as the display monitor 106, and the user performs an operation of selecting an arbitrary position on the screen with a finger or the like, thereby performing input of a destination of the vehicle, selection of various processes, and the like. Of course, in addition to the touch panel, an operation using a hardware SW or a joystick, or an operation using a remote control is also possible. Further, by adding an operation program to the communication terminal, it is possible to operate the communication terminal itself.

  The nonvolatile memory 107 is a memory that stores various types of information such as map data received from the information distribution center 400. The nonvolatile memory 107 can hold the stored data even when the power of the in-vehicle device 100 is turned off. For this, for example, a flash memory or the like is used.

  FIG. 3 is a system block diagram showing the configuration of the information distribution center 400. The external interface 401 is a part that performs an interface for connecting the information distribution center 400 and the mobile communication network 300. The information distribution center 400 can be connected to the mobile communication network 300 via the external interface 401. The request reception server 402 receives various requests such as a route search from the in-vehicle device 100 received from the mobile communication network 300, and in response to the request, a route search and a map each of which is responsible for each server described later. Request to execute processing such as clipping. Then, the processing result output from each server is output to the mobile communication network 300 via the external interface 401. Thereby, the processing result data such as the requested route search is transmitted from the mobile communication network 300 to the communication terminal 200 and distributed to the in-vehicle device 100.

  The map distribution server 403 stores map data of various places in the country on a storage medium such as a hard disk. Then, according to the map request from the request reception server 402, the map data of the corresponding area is searched from among the map requests and output to the request reception server 402. The route search server 404 stores information regarding road connections throughout the country, searches for a route (recommended route) corresponding to the route search request from the request reception server 402, and outputs the result to the request reception server 402. . In this route search, information on the vehicle position searched by the position information search server 405 described below, a database of current traffic information stored in the traffic information server 406, and the like are used.

  The position information search server 405 searches for the vehicle position on the map. When the in-vehicle device 100 issues a route search request, information related to the vehicle position detected by the current location detection device 101 in FIG. 2 is also transmitted from the in-vehicle device 100. Based on this information, the vehicle position can be made to correspond on the map. The location information search server 405 stores the address and name of various facilities and the like in various parts of the country, and also stores various information related to the facilities. And based on such information, a function for creating a list of search information (search information list creation function) used for the user to specify a destination when requesting a route search is provided. This function will be described in detail later.

  The traffic information server 406 stores a database of current traffic information. For this traffic information, for example, information collected at a road traffic information center is used. At this time, in the case of traffic information with empirical regularity such as rush hour, depending on the distance from the own vehicle position, inferred from the current traffic information when the distance is close, or past information when far from the own vehicle position The traffic information at the time of passing through the position can also be used. The customer DB server 407 holds personal data of customers who own the vehicle-mounted device 100 and updates the personal data according to the usage status of the information distribution center 400. The personal data here includes, for example, billing information.

  FIG. 4 shows an example of the data flow when the user requests a route search from the in-vehicle device 100 to the information distribution center 400. Here, a description will be given on the assumption that the user designates a route search destination from a list. The user first operates the display monitor 106 in FIG. 2 to specify the type of facility or the like desired as the destination, the area where the facility or the like is located, and the like. The in-vehicle device 100 requests the search information, that is, the list of destinations by transmitting information such as the type of facility and the region designated by the user in this way to the information distribution center 400. The search information request is transmitted via the communication terminal 200 and the mobile communication network 300 as described with reference to FIG.

  When the in-vehicle device 100 transmits a request for search information to the information distribution center 400, the in-vehicle device 100 detects the communication state at that time. The communication state detected here is a communication state of wireless communication performed between the communication terminal 200 and the mobile communication network 300. This includes the communication method and switching method described above, the received electric field strength at the communication terminal 200, and the like. included. Then, the detected communication state information is transmitted to the information distribution center 400 via the communication terminal 200 and the mobile communication network 300 in the same manner as the search information request transmitted earlier. In this way, the communication state from the in-vehicle device 100 to the information distribution center 400 is notified. The contents of the communication state notified at this time will be described in detail later with reference to FIG.

  A request for search information transmitted from the in-vehicle device 100 to the information distribution center 400 is received by the request reception server 402. When the request reception server 402 receives the search information request, the request reception server 402 determines the content of the search information requested from the position information search server 405 based on the communication state notified from the in-vehicle device 100 thereafter. At this time, when the communication method to be used is the CDMA method or the switching method is packet switching, etc., high-speed data communication is possible, and if the received electric field strength is sufficiently high, the communication Judge that the condition is good. In this case, for example, a facility corresponding to the type or region designated by the user is requested together with various information regarding the facility in addition to its address and name. When it is determined that the communication state is not good, only the address and name of the facility are requested.

  A specific example of the contents described above will be described. For example, it is assumed that a search information request for a hotel is made by a user. At this time, when the communication state is good, not only the address and name of the hotel but also information such as the accommodation fee and the number of rooms is requested from the request reception server 402 to the location information search server 405. To do. Further, for example, if the location information search server 405 updates the accommodation reservation status periodically, the information may also be requested. Further, for example, when a search request for a commercial facility is requested from a user and the communication state is good, the location information search server 405 is notified of business hours, regular holidays, etc. according to the address and name. Request information.

  The location information search server 405 creates a search information list using the search information list creation function described above according to the content of the search information requested from the request receiving server 402 as described above. At this time, from the information of various facilities, etc., in various locations throughout the country stored in the location information search server 405, information such as facilities corresponding to the type or region designated by the user is searched and extracted, and the extracted facilities And so on. A list of search information created in this way is returned from the position information search server 405 to the request reception server 402, and is distributed from there to the in-vehicle device 100 via the mobile communication network 300 and the communication terminal 200.

  When the list of search information is distributed as described above, the in-vehicle device 100 displays the list on the display monitor 106. Next, the user selects a destination from this list by operating the display monitor 106. When the destination is selected from the list by the user, the in-vehicle device 100 issues a route search request from the current location to the destination. The route search request issued by the in-vehicle device 100 is transmitted to the information distribution center 400 via the communication terminal 200 and the mobile communication network 300 in the same manner as the search information request described above. In the information distribution center 400, the route search request is received by the request reception server 402.

  When the in-vehicle device 100 transmits the route search request to the information distribution center 400 as described above, the in-vehicle device 100 detects the communication state at that time as in the case of transmitting the search information request described above. Then, the communication status information is transmitted from the in-vehicle device 100 to the information distribution center 400 by transmitting the communication status information to the information distribution center 400. At this time, the same items as described above, that is, information such as the communication method and exchange method, and the received electric field strength at the communication terminal 200 are detected and transmitted.

  When receiving a route search request from the in-vehicle device 100, the request reception server 402 first makes a route search request to the route search server 404. In response to this route search request, the route search server 404 performs a route search based on the vehicle position information from the position information search server 405 and the traffic information from the traffic information server 406. Then, the guidance data of the recommended route is returned to the request reception server 402 as the route search result. Note that the content of the route search result does not change depending on the communication state.

  Upon receiving the recommended route guidance data from the route search server 404, the request reception server 402 then outputs a map request for the recommended route to the map distribution server 403. At this time, the request reception server 402 determines the content of the map request made to the map distribution server 403 based on the communication state notified from the in-vehicle device 100 after the route search request. Then, the better the communication state is, the more detailed map is requested from the map distribution server 403. For example, when the communication state is good, a map is requested for all roads included in a certain range along the recommended route.

  When a part of the communication state is not good when the above-mentioned state is good, that is, when the communication method to be used is the TDMA method, the switching method is the circuit switching, or the reception electric field strength is not sufficiently high. If it is a value, it is determined that the communication state is medium. In this case, with respect to the range along the same recommended route as that in the case where the communication state is good, only the major roads included in the range, such as highways, national roads, and prefectural roads, are sent to the map distribution server 403. Request a map.

  When the communication state does not apply to any of the above, that is, when the communication method to be used is the FDMA method, or when the received electric field strength is a predetermined value or less, it is determined that the communication state is bad. In this case, the map is not requested to the map distribution server 403. As a result, only the guidance data of the recommended route is transmitted from the information distribution center 400 to the in-vehicle device 100. In the in-vehicle device 100, the distance from the current location to the intersection serving as the guidance point and the traveling direction are displayed on the screen based on the transmitted guidance data of the recommended route. A specific example of the map difference as described above will be described in detail later with reference to FIG.

  The map distribution server 403 cuts out a certain range along the recommended route according to the contents of the map request made from the request receiving server 402 as described above, and uses the method described later with reference to FIG. Is extracted from the stored map data. The extracted map data is returned to the request reception server 402.

  In this manner, recommended route guidance data and map data along the recommended route (except when the communication state is bad) are returned to the request reception server 402. The request reception server 402 transmits these data to the in-vehicle device 100 via the mobile communication network 300 and the communication terminal 200. The in-vehicle device 100 provides a route search result to the destination selected by the user by displaying the transmitted data as an image. In this way, a series of processing for route search is completed.

  FIG. 5 shows a method of cutting out a map in a cutout region within a predetermined range along the recommended route set by the route search server 404, that is, within a predetermined distance from the recommended route, in the map distribution server 403. As described above, when a destination is set in the in-vehicle device 100 and a route search request to the information distribution center 400 is issued from the in-vehicle device 100, the route search server 104 sends a route search to the route search server 104. Requests are made. In response to this route search request, the route search server 404 sets the current location 52 and the destination 53, and sets a recommended route 54 connecting between them by a well-known route search calculation process.

  The map distribution server 403 sets a cutout range 55 within a certain range from the recommended route 54 as indicated by, for example, shading in the figure. A wider range is set around the current location 52 and the destination 53 than on other routes. In addition, when a waypoint is set in the middle, a wider range is set around the route point than on other routes. Map data in the area of the cutout range 55 is extracted for each mesh 51 of the mesh 51 obtained by dividing the map into predetermined ranges. The extracted map data is distributed from the request reception server 402 to the in-vehicle device 100 via the communication terminal 200 and the mobile communication network 300.

  FIG. 6 shows an example of data contents transmitted when the communication status is notified from the in-vehicle device 100 to the information distribution center 400. Here, the communication method, the circuit switching reception field strength, and the packet communication reception field strength are each represented by 2-byte data. The communication method data column denoted by reference numeral 61 represents a communication method used in wireless communication performed between the communication terminal 200 and the mobile communication network 300. For example, in the case of wireless communication using the CDMA system, the content of the first byte of the data column 61 is set to 1, and similarly, 2 for a TDMA system such as GSM, and 3 for an FDMA system. . Even if the communication method is the same, if the data communication speed differs depending on, for example, the communication carrier, the contents of the data column 61 are set to different numerical values in order to distinguish them.

  The difference between the communication method and the exchange method as described above is determined based on information output from the communication terminal 200 to the in-vehicle device 100 when the communication terminal 200 is connected to the in-vehicle device 100. Or you may make it judge a communication system with the cable used for the connection of the communication terminal 200 and the vehicle equipment 100. FIG. Alternatively, in-vehicle device 100, may be set by the user to the method of using the transmission method and a switching system in advance, it may instruct the vehicle-mounted device 100 to the communication terminal 200.

  If the communication method supports both circuit switching and packet switching, which communication method is used in the communication terminal 200 is shown in the data column of this communication method. For example, when circuit switching is used, the content of the second byte of the data column 61 is set to 1, and when packet switching is used similarly, it is set to 2.

  The data field of the received field strength for circuit switching indicated by reference numeral 62 represents the received field strength of the radio waves for circuit switching transmitted from the mobile communication network 300. The received electric field strength is measured based on information measured at the communication terminal 200 and output from the communication terminal 200 to the in-vehicle device 100. For example, the content of the data column 62 is set to 0 when the measured received electric field strength is lower than the value of the received electric field strength (represented as Emin) corresponding to the minimum receiving sensitivity of the communication terminal 200. Then, the case where it is within +2 dB from Emin is set to 1, and the case where it is within +4 dB is set to 2. Similarly, every time the received electric field strength increases in increments of 2 dB, the content of the data column 62 is increased by one.

  Similarly to the case of the above-described circuit switching, the data field of the packet switching reception electric field strength indicated by reference numeral 63 represents the reception electric field strength of the packet-switching radio wave transmitted from the mobile communication network 300. If the communication method represented by the contents of the data column 61 does not support packet switching, the data column 63 is fixed to a predetermined content. The content at this time may be anything. In this case, the contents of the data column 63 are ignored at the information distribution center 400.

  FIG. 7 shows a specific example of the difference depending on the communication state regarding the map distributed from the information distribution center 400 to the vehicle-mounted device 100 and displayed on the display monitor 106. FIG. 7A is an example of a map when the communication state is good. In this case, for the map acquisition range cut out as described with reference to FIG. 5 along the recommended route 71 from the current location 70, maps for all the roads are distributed from the information distribution center 400 and displayed on the display monitor. 106. As a result, in addition to the recommended route 71 and the main road represented by the road 72, roads other than the main road represented by the road 73 are also displayed. In FIG. 7A, the recommended route 71 is represented by the thickest line, the next thickest line is the main road, and the thinnest line is the road other than the main road. The main roads here are expressways, national roads, prefectural roads, etc. as described above. Here, the difference in the road is represented by the difference in the thickness of the line, but it may be represented by the difference in the display color.

  FIG. 7B is an example of a map when the communication state is medium as described above. In this case, within the map acquisition range, a map for only the recommended route 71 and the main road represented by the road 72 is distributed from the information distribution center 400. This map is displayed on the display monitor 106 as shown in FIG. Therefore, roads represented by roads 73 other than the main road are not displayed in this case.

  FIG. 7C shows an example of a case where the communication state is bad as described above. In this case, map data is not distributed from the information distribution center 400, but only guidance data of recommended routes is distributed. For this reason, it is not possible to display a map as in the above two examples. Therefore, in this case, information based on the guidance data is displayed. Specifically, the distance to each intersection serving as a guidance point and the traveling direction are displayed on the screen as shown in FIG. The user can advance the recommended route by referring to the screen display.

  FIG. 8 shows a flowchart of processing executed in the vehicle-mounted device 100 and the information distribution center 400 in the series of route search processing described above. (A) shows a processing flow executed in the vehicle-mounted device 100, and (b) shows a processing flow executed in the information distribution center 400, respectively. Hereinafter, these processing flows will be described. First, the processing flow of the in-vehicle device 100 in (a) will be described.

  The in-vehicle device 100 executes the processing flow of FIG. 8A when the type or area of the facility or the like desired to be the destination is designated by the user's operation. In step S <b> 1, a search information request is transmitted to the information distribution center 400. Thereafter, in step S2, a communication state of wireless communication is detected, and in step S3, the detected communication state is notified to the information distribution center 400.

  In step S4, a list of search information transmitted from the information distribution center 400 is received. This list of search information is transmitted from the information distribution center 400 in step S23 of FIG. 8B described later in response to the search information request transmitted in step S1. In the next step S5, the search information list is displayed on the display monitor 106. In step S6, it is determined whether the user has operated the display monitor 106 to select a destination from the displayed search information list.

  If it is determined in step S6 that the destination has been selected, information on the current location is acquired in step S7, and a route search request from the current location to the destination is transmitted to the information distribution center 400 in step S8. Thereafter, the communication state of the wireless communication is detected in step S9, and the detected communication state is notified to the information distribution center 400 in step S10.

  In step S11, the recommended route guidance data and map data transmitted from the information distribution center 400 are received. The recommended route guidance data and map data are transmitted from the information distribution center 400 in step S27 of FIG. 8B described later in response to the route search request transmitted in step S8. If it is determined that the communication state is poor in the information distribution center 400, map data is not distributed as described above, and therefore only the guidance data for the recommended route is received in step S11.

  In step S12, a map is displayed on the display monitor 106 based on the recommended route guidance data received in step S11 and map data (except when the communication state is bad). After execution of step S12, the processing flow of FIG.

  Next, the processing flow of the information distribution center 400 of (b) is demonstrated. When a request for search information is transmitted from the in-vehicle device 100 and further notification of the communication state is performed, the information distribution center 400 executes the processing flow of FIG. Note that the request for search information and the notification of the communication state from the in-vehicle device 100 are performed in steps S1 and S3 in FIG. In step S21, the search information request and the communication state transmitted from the in-vehicle device 100 are received. In step S22, a list of search information corresponding to the communication state is created according to the content of the received search information. In step S23, the created search information list is transmitted to the in-vehicle device 100.

  In step S24, the route search request and the communication state transmitted from the in-vehicle device 100 are received. These are transmitted in steps S8 and S10 in FIG. 8A as described above. In step S25, a route search is performed based on the current location and destination specified in the received route search request, and as a result, recommended route guidance data is acquired. In step S26, a map of a certain range along the recommended route is extracted based on the communication state received in step S24. At this time, if it is determined that the communication state is bad, the map data is not extracted.

  In step S27, the recommended route guidance data acquired in step S25 and the map data extracted in step S26 (except when the communication state is bad) are transmitted to the in-vehicle device 100. These data are received by the in-vehicle device 100 in step S11 of FIG. After execution of step S27, the processing flow of FIG.

According to the embodiment described above, the following operational effects can be obtained.
(1) When requesting data distribution from the in-vehicle device 100 to the information distribution center 400, the communication state of the wireless communication at that time is detected in the in-vehicle device 100 and notified to the information distribution center 400. The information distribution center 400 extracts the data content corresponding to the communication state, and changes the data content distributed to the in-vehicle device 100. Since it did in this way, the data content suitable for a communication state can be delivered to the vehicle equipment 100. FIG.

(2) The in-vehicle device 100 detects the communication method, the exchange method, and the received electric field strength as the communication state of the wireless communication. Further, the switching system includes circuit switching and packet switching, and the received electric field strength is detected for each of the circuit switching and the packet switching. Since it did in this way, in the information delivery center 400, the data content to deliver can be changed according to each received electric field strength of circuit switching and packet switching.

(3) When the received field strength of the detected packet exchange is less than or equal to the predetermined value, the vehicle-mounted device 100 receives data from the information distribution center 400 using circuit exchange. Since it did in this way, even when data cannot be received by packet switching, data can be received using circuit switching.

  In the above-described embodiment, an example in which map data is distributed from the information distribution center 400 to the vehicle-mounted device 100 has been described. However, the present invention is not limited to this content, and various other content data is distributed. It can also be applied to the case.

  Further, in the above embodiment, the in-vehicle device 100 determines the communication method and the exchange method, and further detects the communication state in the in-vehicle device 100 from the measurement result of the received electric field strength output from the communication terminal 200, and the detection. The example in which the result is notified to the information distribution center 400 has been described. However, these communication states may be detected by the communication terminal 200, and the communication state may be directly notified to the information distribution center 400 without using the in-vehicle device 100. Or it is good also as a structure which integrated the vehicle equipment and the communication terminal by incorporating a communication terminal in the vehicle equipment.

  The present invention is not limited to the above embodiment. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

It is a block diagram which shows the structure of the map information delivery system by one Embodiment of this invention. It is a block diagram which shows the structure of a vehicle equipment. It is a block diagram which shows the structure of an information delivery center. It is a figure which shows the flow of the data at the time of a route search request | requirement. It is a figure which shows the method of cutting out the map in the fixed range along a path | route. It is a figure which shows the example of the data content transmitted when notifying a communication state from an onboard equipment to an information delivery center. It is a figure which shows the specific example of the difference in the map by a communication state, (a) is a case where a communication state is favorable, (b) is a case where a communication state is medium, (c) is a case where a communication state is bad. It is a specific example of each. It is a flowchart which shows the flow of the process performed by route search, (a) shows the process flow performed in an onboard equipment, (b) shows the process flow performed in an information delivery center, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 100 In-vehicle apparatus 200 Communication terminal 300 Mobile communication network 400 Information distribution center

Claims (5)

Various types of data are transmitted from the information terminal mounted on the vehicle to the information distribution center, and various data distributed from the information distribution center according to the contents of the request are received by the information terminal using wireless communication. In the data communication method of the in-vehicle information terminal provided to
The information terminal transmits the request, detects the communication state of the wireless communication, and contacts the information distribution center,
The information distribution center changes the content of the data to be distributed based on the communicated communication state. The data communication method of the in-vehicle information terminal according to claim 1,
The communication state of wireless communication detected by the information terminal includes at least one of a communication method, an exchange method, and a received electric field strength. The data communication method of the in-vehicle information terminal according to claim 2,
The switching method includes circuit switching and packet switching,
A data communication method for an in-vehicle information terminal, wherein the information terminal detects the received electric field strength for each of circuit switching and packet switching. In the data communication method of the in-vehicle information terminal according to claim 3,
When the received electric field strength detected for the packet switching is less than or equal to a predetermined value, the information terminal receives various data distributed from the information distribution center using wireless communication based on circuit switching. The data communication method of the terminal. In the information terminal in any one of Claims 1-4,
A communication means for performing the wireless communication;
An in-vehicle information terminal comprising display means for displaying the received data as an image.

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