Abstract:
In existing moving object tracking, there is a great communication load between a terminal and a platform, because the terminal should report its location to the platform every second or every minute and the platform should frequently process the location form the terminal. It is possible to reduce the great communication load on the server, by calculating an error between the current GPS location and the estimated location at a specific time on the basis of the estimated arrival time of the moving object. It allows that the terminal report its location to the server only when the error between current GPS location and the estimated location is greater than a predetermined threshold value.

Description:
TECHNICAL FIELD 
     The present invention relates to a system and a method for reducing a communication load of a platform for tracking a moving object, and more particularly, to a system and a method for reducing a communication load of a tracking platform in which an estimated arrival time for a moving object to move from a current location to an arrival location (destination) is calculated and then a communication path between the moving object to be tracked and the tracking platform is disconnected when the calculation of the estimated arrival time is completed. 
     BACKGROUND ART 
     There are known three tracking methods. In the first method, a terminal of a moving object reports an own location to a tracking server (hereinafter, referred to as “tracking platform” or “platform”) at constant time intervals. In the second method, the platform requests the terminal to send the location of the moving object. In the third method, when road network data is available, the terminal reports the location of the moving object to the platform based on road segment information only if road segments are changed. 
     In the first method, the terminal reports its location to the platform every second or every minute and the platform processes data on the reported location. Accordingly, an excessive overloading of communication data load between the terminal and the platform can be caused. Therefore, the first method is not suitable for urgent cases with the need for urgency and accuracy. 
     In the second method, when the time interval at which the platform acquires the location of the terminal decreases, the platform requests the location of the terminal more frequently, and the terminal has to collect, calculate, and report the location information in response to the request. Accordingly, the excessive overloading of communication data load between the terminal and the platform may be caused as the first method. In addition, the platform needs to track the location of the terminal in real time, which is not supported by the second method. 
     In the third method, the terminal has to report the location of the terminal to the platform every road segment. In this method, the frequency of reporting the location is less than that of the first or second method and the platform can track the terminal in real time. However, if the road network is consisted of a number of small road segments, the communication load between the terminal and the platform may be increased as the first and second methods. The reason is, as the number of road segments increases, the number of issuing updates also increases. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a system according to an exemplary embodiment of the present invention. 
         FIG. 2  is a flowchart of a method according to an exemplary embodiment of the present invention. 
         FIG. 3  shows an example of the present invention in relation to a path (road). 
     
    
    
     BRIEF SUMMARY OF THE INVENTION 
     Technical Goal of the Invention Problem 
     The present invention provides a system and a method for reducing a communication load of a platform for tracking a moving object by reducing the frequency of communications for reporting a location of a terminal of the moving object. 
     Disclosure of the Invention Technical Solution 
     A moving object occupant (a terminal user) inputs a current location and an arrival location of the moving object by the use of a terminal having a location detection module and reports the current location and the arrival location to a platform. The platform searches a geographic information database (DB) for location information on the current location and the arrival location, extracts all the possible paths, and calculates an estimated arrival time. The platform transmits the extracted paths and the estimated arrival time to the moving object (terminal). 
     The terminal calculates a difference in distance between the current location and an estimated location of the moving object detected in real time by the location estimation module built in the moving object on the basis of all the possible paths, the estimated arrival time, and the current location information of the moving object detected in real time by the location detection module. At this time, the current location of the moving object is reported only when the difference in distance is greater than a predetermined threshold value. 
     Advantageous Effect of the Invention 
     According to the present invention, it is possible to drastically reduce the frequency of communication between the terminal and the server and communication load on the server. The reason is that location update from terminal to server is happened only if predefined threshold is exceed at predefined location at a specific time, on the basis of the estimated arrival time of the moving object. 
     In addition, according to the present invention, it is possible for the server to estimate the location of the moving object by the use of a location estimation algorithm, without any additional communication between the terminal and server. Therefore, when location based service providers request the server for the location of the moving object, the server can provide the location of the moving object in real time on the basis of the estimation data without any additional communication with the terminal. 
     DETAILED DESCRIPTION OF THE INVENTION 
     According to an aspect of the present invention, there is a provided system for reducing a communication load of a platform for tracking a moving object, the system including: an estimated arrival time calculating unit receiving a current location and an arrival location of the moving object from the moving object, calculating estimated arrival time for the moving object to reach the arrival location, and transmitting the estimated arrival time to the moving object; a terminal which is located in the moving object, receiving the estimated arrival time and determining an estimated location; and a communication path on-off controlling unit inactivating a communication path for reporting the current location and the arrival location from the moving object when the terminal receives the estimated arrival time is received, and activating the communication path when the estimated arrival time has to be newly calculated again. 
     According to an aspect of the present invention, there is provided a method of reducing a communication load of a platform for tracking a moving object, the method including: (a) receiving a current location and an arrival location of the moving object, calculating an estimated arrival time for the moving object to reach the arrival location, and transmitting the estimated arrival time to the moving object; (b) transmitting the estimated arrival time to a terminal of the moving object and allowing the terminal, which is located in the moving object, to determine an estimated location of the moving object; and (c) inactivating a communication path for reporting the current location and the arrival location from the moving object when the terminal receives the estimated arrival time. In addition, the method may further include (d) activating the communication path when the estimated arrival time has to be newly calculated again. 
     Mode for Invention Embodiments 
     Hereinafter, the present invention will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements. 
       FIG. 1  shows an exemplary embodiment of a system according to the present invention and  FIG. 2  shows an embodiment of a method according to the present invention. 
     A location-tracking platform  11  corresponds to the aforementioned platform. The location-tracking platform  11  extracts paths between the current location and the arrival location of a moving object  10  by receiving the current location and the arrival location from the terminal  101 . Then the location-tracking platform  11  calculates the estimated arrival time to move from an arbitrary location on the extracted path to the arrival location. 
     For this, the location-tracking platform  11  includes a path generation requesting unit  111 , a path extracting unit  112  and an estimated arrival time calculating unit  113 . When a current location and an arrival location of a moving object  10  are reported from a terminal  101  located in a moving object  10  (S 201 ), all the possible paths between the current location and the arrival location are extracted on the basis of the reported current location and arrival location and the estimated arrival time is calculated and transmitted to the terminal  101  (S 202 ). Alternatively, the location-tracking platform  11  further includes a moving object location estimating unit  114  with a real-time location estimation algorithm and estimates the location of the moving object  10 . The estimated arrival time is calculated based on the estimated location. 
     Hereinafter, a function of tracking the moving object  10  performed by the path generation requesting unit  111 , the path extracting unit  112 , the estimated arrival time calculating unit  113 , and the moving object location estimating unit  114 , will be described in detail. The path generation requesting unit  111  receives the current location and the arrival location from the terminal  101  located in the moving object  10 , makes a request message for generating paths between both locations and transmits the request message to the path extracting unit  112 . 
     The path extracting unit  112  receives the request message from the path generation requesting unit  111 , accesses to a geographic database (DB), extracts all the possible paths between both locations, and transmits the extracted paths to the estimated arrival time calculating unit  113 . 
     The estimated arrival time calculating unit  113  calculates the estimated arrival time to move from the arbitrary location to the arrival location of the moving object  10  with reference to the extracted paths and an estimated location of the moving object  10  estimated by the moving object location estimating unit  114  in real time and then transmits the calculation result together with the extracted path information to the terminal  101 . 
     An exemplary embodiment of the present invention will be described in detail with reference to  FIGS. 1 and 2 . 
     The location-tracking platform  11  receives the current location and the arrival location from the terminal  101  located in the moving object  10  through the reporting path and transmits the current location and the arrival location to the path generation requesting unit  111 . The reporting paths a and b will be described clearly in the following. The terminal  101  includes an own current location detecting unit  1101  detecting the current location (real location) of the moving object  10  in real time, and the terminal user inputs the current location detected by the current location detecting unit  1101  and the arrival location of the terminal user through the terminal  101  and then transmits the inputs to the location-tracking platform  11 . 
     The path generation requesting unit  111  makes the request message for generating paths including information on the current location and arrival location and transmits the request message to the path extracting unit  112 . When the path extracting unit  112  extracts all the possible paths between both locations from the geographic DB (S 2021 ), the path extracting unit  112  converts the information on the current location and arrival location into coordinate data, transmits the converted data to the path information DB, receives the information on all the possible paths between the current location and the arrival location, and extracts the paths between both locations. 
     The estimated arrival time calculating unit  113  receives all the possible paths extracted by the path extracting unit  112 , accesses to a real-time traffic condition providing server  12 , and receives current traffic conditions. In addition, the estimated arrival time calculating unit  113  refers to the estimated location of the moving object  10  estimated by the moving object location estimating unit  114  in real time, calculates the estimated arrival time for the moving object  10  to reach the arrival location from an arbitrary location, and transmits the calculation result together with the extracted path information to the terminal  101  (S 2202 ). 
     At this time, an estimated location determining unit  1012  built in the terminal  101  located in the mobile object  10  and the moving object location estimating unit  114  estimates the location of the moving object  10  interactively. Specifically, the estimated location determining unit  1012  estimates a location of the moving object  10  at an arbitrary location based on all the possible paths to the arrival location received from the location-tracking platform  11 , the estimated arrival time, and the current location of the terminal  101  detected by the current location detecting unit  1101  in real time. 
     When all the possible paths to the arrival location, the estimated arrival time, and so on are transmitted to the terminal  101 , a communication path on-off controlling unit  13  inactivates the reporting paths a and b as a normal neutral state (the state at which both paths are not activated). The communication path on-off controlling unit  13  will be described more clearly in the following. 
     A distance difference measuring unit  1013  compares the current location detected by the current location detecting unit  1011  in real time with the estimated location detected by the estimated location determining unit  1012  in real time and measures the difference in distance between the current location and the estimated location in real time (S 204 ). 
     When the difference in distance between the current location and the estimated location is greater than the predetermined threshold value, the distance difference measuring unit  1013  makes the communication path on-off controlling unit  13  activate the communication path (reporting path) b for reporting that the difference in distance is greater than the threshold value (S 205 ). The distance difference measuring unit  1013  reports the current location through the reporting path b to the location tracking platform  11  when the difference in distance between the current location and the estimated location is greater than the predetermined threshold value (S 206 ). 
     The path from the new current location received from the distance difference measuring unit  1013  to the arrival location are newly extracted, and the estimated arrival time is newly calculated (S 207 ) and transmitted to the terminal  101 , by the function modules of the tracking platform  11  as described above. After being transmitted to the terminal  101 , the aforementioned operations are performed as described above (S 208 ). The terminal  101  and the location tracking platform  11  estimates and tracks the location of the moving object  10  continuously by the use of the location estimation algorithm on the basis of the new path and estimated arrival time in real time until the moving object  10  reaches the arrival location. 
     The communication path on-off controlling unit  13  is used for activating one of the reporting communication paths a and b and is included so as to reduce the communication load. 
     That is, the communication path on-off controlling unit  13  activates the reporting path a when a terminal user reports the current location and the arrival location to the location tracking platform  11  through the terminal  101 . The communication path on-off controlling unit  13  activates the reporting path b when the difference in distance is greater than the predetermined threshold value. The communication path on-off controlling unit  13  inactivates both reporting paths a and b in the other cases. Therefore, communication path on-off controlling unit  13  can suppress unnecessary communications between the terminal  101  and the location tracking platform  11 . 
     When the extraction of the path and the calculation of the estimated arrival time are requested from the communication path on-off controller  13 , that is, the aforementioned report is requested, the communication path on-off controlling unit  13  detects the report event and holds the communication state for reporting the current location and the arrival location from the terminal  101  to the location tracking platform  11  to reduce the communication load. The report event according to an embodiment of the present invention occurs only when the user inputs the current location and the arrival location and requests the tracking location platform  11  to track the moving object or the difference in distance is greater than the predetermined threshold value, or so the location tracking platform  11  has to calculate the estimated arrival time. 
       FIG. 3  shows an example according to the present invention in relation to a path (road). 
     For example, when the moving object  10  having the terminal  101  desires to move from a predetermined starting location to the arrival location, the terminal  101  detects the current location through the current location detecting unit  1011  and transmits the detection result together with current speed information to the tracking platform  11 , and the path extracting unit  112  in the location tracking platform  11  accesses to the geographic DB and extracts all the possible paths between the starting location and the arrival location. 
     In a case where the terminal  101  reports the current location of the moving object  10  to the location tracking platform  11  and the location of the terminal  101  is estimated only when the segment is changed based on the road segment (A-&gt;B-&gt;C-&gt;D-&gt;E) information, that is, in case of the aforementioned third method, though the moving object  10  does not deviates from the range of the threshold value, the difference in distance between the current location and the estimated location of the moving object  10  is smaller than the predetermined threshold value, the current location of the moving object  10  has to be reported to the server whenever the segment is changed. 
     However, according to the method of the present invention, the report event occurs only when the difference in distance between the current location at a predetermined time and the estimated location at the predetermined time is greater than the threshold value (threshold distance) regardless of the road configuration. Accordingly, when the difference in distance is not greater than the threshold value, the location tracking platform  11  estimates the location of the moving object  10  in real time without additional location reports, in interaction with the estimated location determining unit  1012 . Therefore, the present invention has the great advantage to reduce the communication load, specifically when the number of the segments constituting the road is large. 
     The invention can also be embodied as computer readable codes on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. 
     Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 
     The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.