[0001]     This application claims the benefit of the Korean Patent Application No. 2005-0078434, filed on Aug. 25, 2005, which is hereby incorporated by reference as if fully set forth herein.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a location based service system and a position information updating method thereof, and more particularly, to a location based service system and a position information updating method thereof in which the number of times a message is transmitted to a position information server and the number of times a database in the position information server is updated are minimized.  
         [0004]     2. Discussion of the Related Art  
         [0005]      FIG. 1  is an exemplary view illustrating a basic configuration of a related art location based service system. Referring to  FIG. 1 , the related art location based service system includes a mobile communication terminal  10 , receiving position information provided from a plurality of satellites  20 , and a position information server  40  receiving position message transmitted from the mobile communication terminal  10  in a wireless mode through a base station  30 .  
         [0006]     With the development of mobile communication terminals provided with a global positioning system (GPS), various types of location based services (LBS) are being developed. A position information server is required for location based services. The position information server acquires and manages user (i.e., mobile communication terminal) location.  
         [0007]     Each moving object basically derives its position (i.e., location) and transmits the position result to the position information server through a wireless communication network to continuously update a position value in the server, so that the position information server maintains a position value having a desired accuracy level. Since the server always maintains the user&#39;s current position, the user can promptly be informed of traffic jam, accident, and emergency situations. Additionally, the user&#39;s position can quickly be acquired.  
         [0008]     To allow the position information server to acquire the user&#39;s position, the related art provides a method for periodically (i.e., specified time intervals) requesting the user&#39;s position, and a method for acquiring the user&#39;s position following a request depending on the types of services.  
         [0009]      FIG. 2  is a flow chart illustrating a related art position information updating method. Referring to  FIG. 2 , a current position value is calculated at a predetermined time t def  in step S 21 . The mobile communication terminal  10  then transmits the calculated position value to the position information server  40  in step S 22 . Then, in accordance with decision step S 23 , a determination is made as to whether time t is equal to the predetermined time t def . If time t is not equal to t def , in accordance with the “NO” path out of decision step  23 , the method proceeds by looping back and continually checkup whether time t is equal to t def . If, however, time t is equal to t def , in accordance with the “YES” path out of decision step S 23 , the mobile communication terminal  10  calculates its current position based on global positioning system data per step S 21 .  
         [0010]      FIG. 3  is a block diagram illustrating the data format of a position message transmitted by the mobile communication terminal  10  to the position information server in accordance with the related art. Referring to  FIG. 3 , the message includes a mobile communication terminal identifier msid  11 , the position acquisition time_stamp  12 , and the position coordinate value coord(x,y,z)  13 .  
         [0011]      FIG. 4  is a flow chart illustrating another related art position information updating method. This method is identical with the periodically updating method in that the mobile communication terminal  10  derives its position at a constant time interval ‘t’. However, in the method of  FIG. 4 , the mobile communication terminal  10  does not always transmit the derived position value to the server. Instead, the mobile communication terminal calculates the difference between the current position and the position registered in the server (i.e., the previous position transmitted to the server). If the difference is within (e.g., less than) a threshold value, the derived position value is not transmitted to the server. If the difference is beyond (e.g., greater than) the threshold value, the position value is transmitted to the server to update the position value stored therein. The message is transmitted to the server in the same manner as the periodically updating method.  
         [0012]     Accordingly, and as shown in  FIG. 4 , the mobile communication terminal  10  derives the current position value and stores the value in a memory therein. Then, the mobile communication terminal  10  registers this position value in the server in step S 41 . After the lapse of a certain period of time, the mobile communication terminal  10  derives the current position value again in step S 42 , and compares the derived value with the value previously stored in the memory. If the difference between the derived value and the previous value exceeds an allowable threshold value (i.e., error range) as shown by the “YES” path out of step S 43 , the mobile communication terminal  10  transmits a position message containing the current position to the position information server to update the position value stored in the server, as shown by step S 44 . At this time, the position message transmitted to the server is also stored in the memory inside the mobile communication terminal  10 .  
         [0013]     Frequent message transmission and frequent updating of the database in the server are required so that the position information server can maintain a high degree of position accuracy. If the position value is periodically updated, the server should be updated at a period of a certain time ‘t’ as much as the number of moving objects for position collection. A threshold value based position is updated only if the current position is varied at a threshold value or greater than the previous position. Therefore, in case of a vehicle having high mobility per time, frequent update of the server is required. In this regard, it would be highly beneficial to have a method that reduces the number of times message transmission is required, and the number of times the database at the server must be updated.  
       SUMMARY OF THE INVENTION  
       [0014]     Accordingly, the present invention is directed to a location based service system and a position information updating method thereof, which substantially obviate one or more problems due to limitations and disadvantages of the related art.  
         [0015]     An object of the present invention is to provide a location based service system and a position information updating method thereof in which the number of times message transmission is required, and the number of times the database at the position information server must be updated are reduced.  
         [0016]     Another object of the present invention is to provide a location based service system and a position information updating method thereof in which a position information server maintains user position values within a given error range.  
         [0017]     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the methods and structures particularly pointed out in the written description, including the drawings, and the claims.  
         [0018]     In accordance with one aspect of the present invention, the above-identified and other advantages are achieved by a position information updating method that involves calculating a predicted position of a mobile communication terminal and calculating an actual position of the mobile communication terminal based on global positioning system signals received by the mobile communication terminal. The actual position and the predicted position are then compared and, based on the result of the comparison, position related information is transmitted to a position information server.  
         [0019]     In accordance with another aspect of the present invention, the above-identified and other advantages are achieved by a location based service system. The system includes a position information server and a mobile communication terminal in wireless communication with the position information server. The position information server is configured to receive position information relating to the actual position of the mobile communication terminal and, after the lapse of a certain amount of time, calculate a predicted position value of the mobile communication terminal based on the received position. The mobile communication terminal, in turn, comprises a global positioning system and a controller, where the global positioning system is configured to derive actual mobile communication terminal position and the controller is configured to calculate a predicted position value, in the same manner as the position information server. The controller is further configured to compare the predicted position value to a current, actual position value. The mobile communication terminal is configured to transmit to the position information server, depending on the result of the comparison, updated position information relating to the current, actual position of the mobile communication terminal.  
         [0020]     In accordance with still another aspect of the present invention, the above-identified and other advantages are achieved by a mobile communication terminal. The mobile communication terminal includes a global positioning system configured to calculate, at a first time, actual mobile communication terminal position based on signals received from Global Positioning System satellites. The mobile communication terminal further includes a controller configured to predict, at a second time subsequent to said first time, the position of the mobile communication terminal based on the calculated actual position, and based on mobile communication terminal velocity and motion angle. The controller is also configured to compare the predicted position with an updated, actual position of the mobile communication terminal. The mobile communication terminal further includes a transmitter transmitting position related information to a position information server based on the result of the comparison.  
         [0021]     In yet another aspect of the present invention, the above-identified and other advantages are achieved by a position information updating method. The method involves receiving first position related information for a mobile communication terminal and calculating a predicted position for the mobile communication terminal based on the first position related information. The method then involves determining whether second position related information from the mobile communication terminal has been received and setting a current position of the mobile communication terminal equal to the predicted position if it is determined that the second position related information has not been received. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:  
         [0023]      FIG. 1  is an exemplary view illustrating a basic configuration of a related art location based service system;  
         [0024]      FIG. 2  is a flow chart illustrating a related art position information updating method;  
         [0025]      FIG. 3  is a block diagram illustrating the data format of a position message transmitted to a position information server in accordance with the related art;  
         [0026]      FIG. 4  is a flow chart illustrating another related art position information updating method;  
         [0027]      FIG. 5  is a flow chart illustrating a position information updating method for a mobile communication terminal according to a first exemplary embodiment of the present invention;  
         [0028]      FIG. 6  is a block diagram illustrating the data that may be contained in a position related message according to the first exemplary embodiment of the present invention;  
         [0029]      FIG. 7  is a diagram illustrating an example of position prediction according to exemplary embodiments of the present invention;  
         [0030]      FIG. 8  is a flow chart illustrating a position information updating method for a mobile communication terminal according to the first exemplary embodiment of the present invention from the perspective of a position information server;  
         [0031]      FIG. 9  is a diagram illustrating links along a roadway according to a second exemplary embodiment of the present invention;  
         [0032]      FIG. 10  is a block diagram illustrating the data that may be contained in a position related message according to the second exemplary embodiment of the present invention;  
         [0033]      FIG. 11  is a diagram illustrating an example of road network based position prediction according to the second exemplary embodiment of the present invention; and  
         [0034]      FIG. 12  is a block diagram illustrating a mobile communication terminal according to exemplary embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0036]     In the present invention, a mobile communication terminal and a position information server each calculate a predicted position value “pred_pos,” based on the same previously calculated actual position value, and in the same way, in a synchronized manner. Thus, the position information server calculates a predicted position value at some point in time after receiving actual position data from the mobile communication terminal, where the server registers the actual position data upon receiving it from the mobile communication terminal, and where the server recognizes the predicted position value as the current position value. Likewise, the mobile communication terminal calculates a predicted position value based on the same actual position value that was transmitted to and registered in the server. The mobile communication terminal then compares the predicted position value with an updated (i.e., current) actual position value and, if the difference between the updated actual position value and the predicted position value exceeds a threshold value, the mobile communication terminal transmits a position message to the position information server, where the message contains, among other things, information that reflects the updated, actual position value of the mobile communication terminal, wherein the position information server then registers the updated, actual position value upon receipt.  
         [0037]     Unlike the existing threshold value based position updating method, in the present invention, determining whether to update the position registered at the server is based on the amount of error between the predicted position value and the actual, current position value. Therefore, the accuracy of the predicted position determines the efficiency of the method according to the present invention. Three exemplary methods employing position prediction, in accordance with the present invention, are now described herein below.  
         [0000]     1. Method for Predicting Position Based on Velocity and Motion Angle  
         [0038]      FIG. 5  is a flow chart illustrating a position information updating method according to a first exemplary embodiment of the present invention.  
         [0039]     After the actual, calculated position of a mobile communication terminal is registered at the position information server at a certain time “r” (time_stamp=r) in step S 51 , the mobile communication terminal calculates a predicted position value at a time “r+t” based on the previously calculated, actual position value, as well as the velocity and motion angle of the mobile communication terminal, which the mobile communication terminal derives from GPS data, per step S 52 . When the position message containing the information relating to the actual, calculated position was transmitted to and registered at the position information server, the position message, as illustrated in  FIG. 6 , also contained the same velocity  24  and motion angle  25  information. Thus, the position information registered in the position information server includes velocity and motion angle. As such, the server can, at the time “r+t”, calculate a predicted position value for the mobile communication terminal assuming constant velocity and constant motion angle from the time “r” to the time “r+t”, in the same manner the predicted position value was calculated by the mobile communication terminal in step S 52 .  
         [0040]     It is noted that the position related message, as illustrated in  FIG. 6 , further comprises position related information including position information coord(x,y,z). This position information coord(x,y,z) may comprise the actual, current position coordinates of the mobile communication terminal, as calculated by the mobile communication terminal or, alternatively, the position information coord(x,y,z) may comprise error data, where the error data represents, for example, the difference between the previously calculated position coordinates of the mobile communication terminal and the current or present calculated position coordinates. In the latter case, the actual, current position coordinates can be obtained by adding the error data to the previous position coordinates.  
         [0041]     Referring back to  FIG. 5 , the mobile communication terminal then calculates an updated (i.e., current) actual position value based on signals received from GPS satellites, as set forth in step S 53 .  
         [0042]     The mobile communication terminal then calculates the difference between the predicted position, calculated in step S 52 , and the updated actual position value calculated in step S 53 . The mobile communication terminal then compares the difference with a threshold value corresponding to an allowable error range in step S 54 .  
         [0043]     If the calculated difference value is greater than the threshold value, in accordance with the YES path out of step S 54 , the mobile communication terminal transmits a position message to the position information server, as shown by step S 55 , to update the position value registered at the position information server, per step S 51 .  
         [0044]      FIG. 7  is an exemplary diagram illustrating the position prediction and update method based on constant velocity and motion angle. Referring to  FIG. 7 , “cur_pos” represents an actual, calculated position value of the mobile communication terminal at various time intervals “r+nt”; “reg_pos” represents a position value of the mobile communication terminal transmitted to and registered in the server; and “pred_pos” represents a predicted position value of the mobile communication terminal at the same time intervals “r+nt”. Each black dot represents an actually position, while each white dot represents a predicted position. If the position value “reg_pos(r)” of the mobile communication terminal has been registered in the position information server at the time interval “r”, the predicted position value “pred_pos” and the current position value “cur_pos” are obtained at various “n” intervals of time “t”. At each interval, a determination is made as to whether the difference between the two position values “pred_pos(r+t)” and “cur_pos(r+t)” is greater than the threshold value. The period “t” may be set in inverse proportion to motion velocity as the case may be. If, for example, it is determined that the difference between the two position values “pred_pos(r+t)” and “cur_pos(r+t)” is greater than the threshold value at, for example, time interval “r+4t”, a position message is transmitted to the position information server.  
         [0045]      FIG. 8  is a flow chart illustrating the position information updating method according to the first exemplary embodiment, from the perspective of the position information server. As illustrated, the position information server receives the position message from the mobile communication terminal in step S 81 , and stores the received position value in a memory or database in step S 82 . Subsequently, the position information server calculates a predicted position value for the mobile communication terminal in the same way, and at the same or substantially the same time interval as the mobile communication terminal, as shown in step S 83 , and in a synchronized manner.  
         [0046]     The position information server then determines whether a new position message has been received from the mobile communication terminal in step S 84 . If a new position message has been received from the mobile communication terminal, in accordance with the YES path out of step S 84 , the position information server sets the position value contained in the received position message as the current position value, as shown in step S 85 . If no position message has been received from the mobile communication terminal, in accordance with the NO path out of step S 84 , the position information server uses the predicted position value as the current position value in step S 86 .  
         [0000]     2. Method for Predicting Position Using a Road Network Database Based Position  
         [0047]     In accordance with this exemplary embodiment, the position of the mobile communication terminal is predicted based on information relating to a road on which the mobile is located. In this embodiment, roads are segmented into units called links.  FIG. 9  illustrates three such links: link_a, link_b, and link_c which surround an intersection. To this end, the position information server and the mobile communication terminal possess the same road network database. Moreover, the mobile communication terminal and the position information server recognize the corresponding link on which the mobile is currently positioned, through map matching techniques. Therefore, the position message transmitted to the position information server will preferably include link related information message, such as link_id  36 , as shown in  FIG. 10 .  
         [0048]     To further illustrate this exemplary embodiment, the position “reg_pos(r)” of the mobile communication terminal is registered with the position information server at time “r”. The mobile is, at time “r”, positioned on link_a and advancing along the arrow as shown in  FIG. 9 . In accordance with this embodiment, the predicted position value of the mobile is calculated based on an assumption that the mobile is moving along link_a at a constant velocity and a constant motion angle. After calculating the predicted position value, the mobile communication terminal compares the predicted position value with a current, actual position value. If the difference between the predicted position value and the actual position value exceeds a threshold value corresponding to an allowable error range, the mobile communication terminal transmits a position message conveying information relating to the actual, current position to the position information server, so as to update the position value registered at the position information server. In the interim, the position information server also calculates a predicted position value for the mobile in the same manner.  
         [0049]      FIG. 11  is a diagram illustrating position prediction as the mobile communication terminal moves along link_a, through the intersection and onto link_c. As illustrated in  FIG. 11 , the mobile communication terminal and the position information terminal may, in predicting the position of the mobile communication terminal, assume that the mobile moves from link_a to link_b. However, in this example, the mobile actually moves from link_a to link_c. When, for example, at time “r+4t”, the difference between the predicted position value “pred_pos(r+4t)” and the current, actual position value “cur_pos(r+4t)” exceeds a threshold value, updated, actual position information in the form of a position message, such as the position message illustrate in  FIG. 10 , is transmitted to the position information server.  
         [0050]     To minimize the error between the predicted position value and the actual position value, it is necessary to more accurately predict the direction (i.e., which link) the mobile will travel along as it goes through the intersection as illustrated, for example, in  FIG. 9 . To this end, there are two preferred methods as follows.  
         [0051]     A: Prediction based on the relative size of the road, wherein the prediction involves selecting the link (road), that is largest (e.g., widest) among all the links accessible from the intersection. The assumption is, the larger the road, the more likely it is the mobile communication terminal will follow that link as opposed to the other links.  
         [0052]     B: Prediction based on the straightest link, where more specifically, prediction involves selecting the link having an angle closest to 180° relative to the current link (i.e., the link on which the mobile communication terminal is currently located) as compared to the other links accessible from the intersection.  
         [0000]     3. Method for Predicting Traffic Pattern  
         [0053]     In this exemplary embodiment, it is assumed that the mobile communication terminal and the position information server have the same traffic pattern database as each other. Further in accordance with this embodiment, the predicted position of the mobile is based on a velocity which, in turn, is based on traffic pattern information. More specifically, to enhance the accuracy of the position prediction, the position information server and the mobile communication terminal employ a more accurate velocity. To this end, both the mobile communication terminal and the position information server predict position based on a velocity value associated with the current link and predefined traffic patter data corresponding to the current link.  
         [0054]     Table 1 illustrates timed traffic pattern data for the three exemplary links, link_a, link_b and link_c.  
                               TABLE 1                       Link_id   07:00˜09:00   09:00˜17:00   17:00˜21:00   21:00˜07:00                   Link_a   40%   90%   60%   100%       Link_b   50%   90%   70%   100%       Link_c   70%   80%   70%   100%                  
 
         [0055]     Table 2 illustrates timed timing traffic pattern data that may be used in predicting position when the mobile communication terminal passes through an intersection, such as the intersection illustrated in  FIG. 9 .  
                               TABLE 2                       Branch   07:00˜09:00   09:00˜17:00   17:00˜21:00   21:00˜07:00                   link_a −&gt;   30%   70%   40%   100%       link_b       link_a −&gt;   50%   90%   70%   100%       link_c                  
 
         [0056]     The symbol “%” in the traffic pattern tables 1 and 2 indicates that the velocity used in predicting the position of the mobile is a certain percentage (as shown) of a predetermined or average velocity for a given link at a given time. If the mobile advances from link_a to link_b as shown in  FIG. 11 , the velocity of the mobile in link link_b is assumed based on the predefined traffic pattern information. For example, if the mobile advances from link_a to link_c during the morning rush hour between 07:00 and 09:00, it is assumed that the speed of the mobile is maintained, for example, at 40 km/h which corresponds to 50% of a predetermined or average speed for link_c, for example, 80 km/h.  
         [0057]     To update the position information, the mobile communication terminal may be constructed as shown in  FIG. 12 . The mobile communication terminal includes a global positioning system  110  extracting position and timing information based on a plurality of signals received from GPS satellites, a controller  120  predicting a subsequent position value depending on velocity and motion angle, and generating a control signal for updating the position information if an error between the predicted position value and a current position value provided by the global positioning system  110  is greater than a threshold value. The mobile communication terminal would also comprise a memory  130  temporarily storing information required for the operation of the controller  120 . In addition, the mobile would have a transmitter  140  transmitting a position message including the current position value to the position information server depending on the control signal generated by the controller  120 .  
         [0058]     With regard to the aforementioned embodiments that rely on road network and/or traffic pattern data, it would be advantageous to incorporate into the mobile communication terminal the ability to turn ON and OFF any mode that specifically utilizes this information to calculate the position of the mobile communication terminal. Thus, for example, if the user of the mobile communication terminal is not traveling along a roadway, the user has the option of turning OFF any such mode, whereby the mobile communication terminal would cease to employ any location based service or, alternatively, the mobile communication terminal may automatically or upon selection by the user, provide location based services in accordance with the first exemplary embodiment described above in section  1 , which does not use or rely upon road network and/or traffic pattern data.  
         [0059]     As described above, the location based service system and the position information updating method described herein, according to the present invention, have the following advantages. The number of times the mobile must transmit a position message to the position information server and the number of times position information server must update the database are reduced, therefore reducing the load on the overall system.  
         [0060]     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
A location based service system and a position information updating method thereof are disclosed. The position information updating method includes the steps of positioning an actual position through a global positioning system inside a mobile communication terminal, calculating predicted motion position of the mobile communication terminal, comparing the actual position extracted through the global positioning system with the calculated predicted motion position, and transmitting position related information obtained by the compared result to a position information server.