Abstract:
A method of recording the position of a mobile device, wherein the method is used to reduce power consumption, a mobile device having a position recording function, and a recording medium having embodied thereon a program for executing the method. The method includes calculating a moving speed of the mobile device; if the moving speed is not higher than a first speed, decreasing the frequency of recording of position information of the mobile device; if the moving speed is higher than the first speed, increasing the frequency of recording of position information of the mobile device; and if the moving speed is higher than the first speed and not higher than a second speed, exponentially-changing the frequency of recording of the position information of the mobile device according to the moving speed of the mobile device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 2008-82369, filed in the Korean Intellectual Property Office on Aug. 22, 2008, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Aspects of the present invention relate to a method of recording the position of a mobile device, a mobile device having a position recording function, and a recording medium having embodied thereon a program for executing the method. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, mobile devices having a global positioning system (GPS) function for recording position information of the mobile devices have been released. The GPS is a position-tracking system that can track the position of an object that has stopped or is moving by receiving information from a satellite in any place on earth. Accordingly, mobile devices having a GPS function can track and record their present position. However, mobile devices using a battery, such as mobile phones or personal digital assistants (PDAs), require algorithms capable of recording accurate position information and efficiently controlling power. 
       SUMMARY OF THE INVENTION 
       [0006]    Aspects of the present invention provide a method of recording the position of a mobile device, wherein the method is used to reduce power consumption, a mobile device having a position recording function, and a recording medium having embodied thereon a program for executing the method. 
         [0007]    According to an aspect of the present invention, a method of recording the position of a mobile device is provided. The method includes calculating a moving speed of the mobile device; decreasing the frequency of recording position information of the mobile device if the moving speed is not higher than a first speed; increasing the frequency of recording of position information of the mobile device if the moving speed is higher than the second speed; and changing the frequency of the recording of the position information exponentially according to the moving speed of the mobile device if the moving speed is higher than the first speed and not higher than the second speed. 
         [0008]    According to another aspect of the present invention, the increasing, the decreasing, and the exponentially changing of the frequency of recording of the position information are performed by adjusting a first period to determine whether the position information of the mobile device is recorded. 
         [0009]    According to another aspect of the present invention, the method includes receiving an interrupt signal before calculating the moving speed of the mobile device; if the interrupt signal is received after a prior interrupt signal of the interrupt signal is received, determining whether a period of time corresponding to the first period has passed; and if a period of time corresponding to the first period has passed, recording the position information of the mobile device. 
         [0010]    According to another aspect of the present invention, the interrupt signal is received every second period, and the second period is a constant period of time. 
         [0011]    According to another aspect of the present invention, the decreasing of the frequency of recording of the position information includes turning off a position information receiving function and a position information recording function of the mobile device if the moving speed is not higher than the first speed; and after the functions are turned-off, recalculating the moving speed by turning-on the functions when the first period has passed, turning off the position information receiving and the position information recording functions and maintaining a wait state for the first period if the recalculated moving speed is not higher than the first speed, and recording the position information of the mobile device and changing the first period if the recalculated moving speed is higher than the first speed. 
         [0012]    According to another aspect of the present invention, the position information is based on global positioning system (GPS) coordinates. 
         [0013]    According to another aspect of the present invention, a mobile device is provided. The mobile device includes: a position information receiving unit to receive present position information of the mobile device through a network; a storing unit to store the position information; and a controlling unit to calculate a moving speed of the mobile device based on the present position information and prior position information of the mobile device, and to control the position information to be recorded in the storing unit; wherein, if the calculated moving speed is higher than a first speed and not higher than a second speed, the controlling unit changes the frequency of the recording of the position information exponentially according to the moving speed of the mobile device. 
         [0014]    According to another aspect of the present invention, the controlling unit changes the frequency of recording exponentially by adjusting a first period to determine whether the position information of the mobile device is recorded. 
         [0015]    According to another aspect of the present invention, the mobile device further includes a timer interrupt signal generating unit to periodically generate a timer interrupt signal to transfer the timer interrupt signal to the controlling unit; wherein, whenever the timer interrupt signal is received, the controlling unit determines whether a period of time corresponding to the first period has passed after receiving the prior timer interrupt signal, and if a period of time corresponding to the first period has passed, the controlling unit controls the position information of the mobile device to be recorded in the storing unit. 
         [0016]    According to another aspect of the present invention, the controlling unit controls the position information to be recorded in the storing unit by decreasing the frequency of the recording of the position information if the calculated moving speed is not higher than the first speed, and increasing the frequency of the recording of the position information if the calculated moving speed is higher than the second speed. 
         [0017]    According to another aspect of the present invention, the controlling unit turns off power supplied to the position information receiving unit and the storing unit if the moving speed is not higher than the first speed; recalculates the moving speed of the mobile device by turning-on power supplied to the position information receiving unit and the storing unit if a period of time corresponding to the first period has passed after turning off the power; turns off power supplied to the position information receiving unit and the storing unit and maintain a wait state for a period of time corresponding to the first period if the recalculated moving speed is not higher than the first speed; and controls the position information to be recorded in the storing unit and changes the first period if the recalculated moving speed is higher than the first speed. 
         [0018]    According to another aspect of the present invention, the position information receiving unit includes a GPS receiving unit. 
         [0019]    According to another aspect of the present invention, there is provided a computer readable recording medium having embodied thereon a computer program to execute a method of recording a mobile device as described above. 
         [0020]    Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0022]      FIG. 1  is a block diagram illustrating a function of a mobile device according to an embodiment of the present invention; 
           [0023]      FIG. 2  is a graph of a first period function for recording position information, according to an embodiment of the present invention; 
           [0024]      FIG. 3  is a flowchart of a method of recording the position of a mobile device, according to an embodiment of the present invention; 
           [0025]      FIG. 4  is a flowchart of another method of recording the position of a mobile device, according to another embodiment of the present invention; and 
           [0026]      FIGS. 5A and 5B  are flowcharts of still another method of recording the position of a mobile device, according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0027]    Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. 
         [0028]    Exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. 
         [0029]      FIG. 1  is a block diagram illustrating a function of a mobile device  100  according to an embodiment of the present invention. The mobile device  100  includes a controlling unit  101 , a timer interrupt signal generating unit  102 , a position information receiving unit  103 , a storing unit  104 , and a power supplying unit  105 . According to other aspects of the present invention, the mobile device  100  may include additional and/or different units. Similarly, the functionality of two or more of the above units may be integrated into a single component. The mobile device  100  may be an apparatus using a battery, such as a mobile phone, a personal digital assistant (PDA), a portable multimedia system, etc., or may be a navigation system installed in a moving system such as a vehicle, a plane, a ship, etc. 
         [0030]    The controlling unit  101  controls functions of the mobile device  100 . For example, the controlling unit  101  calculates a moving speed of the mobile device  100  in order to record position information of the mobile device  100  in the storing unit  104 . 
         [0031]    Whenever a timer interrupt signal is received, the controlling unit  101  determines whether a period of time corresponding to a first period T 1  has passed since a prior timer interrupt signal was received. The first period T 1  is a period for determining whether the position information of the mobile device  100  is recorded. The first period T 1  may use a default value, but may also vary according to the moving speed of the mobile device  100 . 
         [0032]    The timer interrupt signal generating unit  102  generates a timer interrupt signal every second period T 2 . The second period T 2  may be a constant period. When the power of the mobile device  100  is turned on, the first period T 1  and the second period T 2  may have the same value. The first period T 1  may vary according to the movement of the mobile device  100 ; the second period T 2 , however, may remain constant. 
         [0033]    When the time corresponding to the first period T 1  has passed, the controlling unit  101  calculates a moving speed of the mobile device  100  using the present position information and prior position information of the mobile device  100 . The controlling unit  101  may record the present position information received through the position information receiving unit  103  in the storing unit  104 . 
         [0034]    The position information includes position data and a receiving time of the position data. The controlling unit  101  detects a difference ΔP between present position information P 1  and prior position information P 2  as (P 1 −P 2 =ΔP). The difference ΔP between the detected position data is a moving distance Δd of the mobile device  100 . 
         [0035]    The controlling unit  101  then detects a difference Δt between a receiving time t 1  included in the present position information P 1  and a receiving time t 2  included in the prior position information P 1  (t 1 −t 2 =Δt). The difference Δt between the detected receiving times is the time in which the mobile device  100  moves the moving distance Δd. 
         [0036]    The controlling unit  101  calculates a moving speed (S=Δd/Δt) of the mobile device  100  by dividing the moving distance Δd by the difference Δt between the receiving times. When the moving speed S of the mobile device  100  is calculated, the controlling unit  101  compares the calculated moving speed S with previously established first and second speeds S 1  and S 2 . The first and second speeds S 1  and S 2  may have values as shown in  FIG. 2 . 
         [0037]      FIG. 2  is a graph of a first period T 1  function for recording position information, according to an embodiment of the present invention. As shown in  FIG. 2 , a first speed S 1  has a value based on a speed where the mobile device  100  hardly moves, and a second speed S 2  has a value based on a high speed of the mobile device  100 . The values of the first speed S 1  and the second speed S 2  may be experimentally determined based on operation conditions of the mobile device  100 . 
         [0038]    As a result of the comparison between the calculated speed S and the first and second speeds S 1  and S 2 , when the calculated speed S is not higher than the first speed S 1 , the controlling unit  101  may control the mobile device  100  so that the frequency (or the number of times) of recording of position information of the mobile device  101  is decreased. For example, the controlling unit  101  may decrease the frequency in which the position information of the mobile device  101  is recorded by lengthening the first period T 1 . If a larger value of the first period T 1  than a currently established value of the first period T 1  is established, the first period T 1  is lengthened. Accordingly, when the mobile device  100  does not move for hours, the position information recorded in the storing unit  104  decreases, thereby reducing power consumption according to the recording of the position information and increasing the capability of the storing unit  104 . 
         [0039]    If the calculated moving speed S is not higher than the first speed S 1 , the controlling unit  101  may control the power supplied to the position information receiving unit  103  and the storing unit  104  to be turned off. While the power supplied to the position information receiving unit  103  and the storing unit  104  is turned off, the controlling unit  101  determines whether the time corresponding to the first period T 1  has passed. If a period of time corresponding to the first period T 1  has passed, the controlling unit  101  may control power supplied to the position information receiving unit  103  and the storing unit  104  to be turned on and control the position information received from the position information receiving unit  103  to be recorded in the storing unit  104 , and then recalculate a moving speed of the mobile device  100 . 
         [0040]    If a recalculated moving speed S′ is not higher than the first speed S 1 , the controlling unit  101  turns off power supplied to the position information receiving unit  103  and the storing unit  104  and maintains a wait state for the first period T 1 . While the position information receiving unit  103  and the storing unit  104  are not used, power supplied to the position information receiving unit  103  and the storing unit  104  is turned off, thereby reducing power consumption of the mobile device  100 . 
         [0041]    If the recalculated moving speed S′ is higher than the first speed S 1 , the controlling unit  101  records the position information received from the position information receiving unit  103  in the storing unit  104  and changes the first period T 1 . The first period T 1  may be changed so that the frequency of recording of the position information changes exponentially, as will be described later. 
         [0042]    When the moving speed S or the recalculated moving speed S′ is higher than the first speed S 1  and lower than the second speed S 2 , the controlling unit  101  may change the first period T 1  according to the moving speed of the mobile device  100  and the frequency of recording of the position information. As shown in  FIG. 2 , when the moving speed S or the recalculated moving speed S′ is higher than the first speed S 1  and lower than the second speed S 2 , the controlling unit  101  may change the first period T 1  so that the frequency of recording of the position information changes exponentially. When the moving speed S or the recalculated moving speed S′ is higher than the first speed S 1  and lower than the second speed S 2 , the value of the exponentially-changed first period T 1  is written in a table form, and the value of the exponentially-changed first period T 1  is included in the controlling unit  101  or in the exterior of the controlling unit  101  so that the controlling unit  101  may refer to the value whenever necessary. 
         [0043]    If the moving speed S is higher than the second speed S 2 , the controlling unit  101  may control the mobile device  100  so that the frequency of recording of the position information of the mobile device  100  is increased. For example, the controlling unit  101  may increase the frequency of recording of the position information of the mobile device  100  by shortening the first period T 1 . When a smaller value of the first period T 1  than a currently established value of the first period T 1  is established, the first period T 1  is shortened. Accordingly, when the moving speed of the mobile device  100  is fast, more accurate position information may be recorded in the storing unit  104  by increasing the amount of position information recorded. 
         [0044]    As shown in  FIG. 2 , a value of the first period T 1  is established according to the moving speed S of the mobile device  100 . In particular, by establishing an upper limit and a lower limit in the first period T 1 , the value of the first period T 1  may be prevented from being 0 or diverging. In  FIG. 2 , a default T 1  is a value of the first period T 1  established by default in the mobile device  100  and may be used when power is turned-on. 
         [0045]    The position information receiving unit  103  may receive position information through a network, and may be a global positioning system (GPS) receiving unit. Accordingly, the position information may be based on GPS coordinates. 
         [0046]    The storing unit  104  stores the position information of the mobile device  100  recorded by the controlling unit  101 , and thus stores at least the position information of the mobile device  100 . The storing unit  104  may be a flash memory, although the storing unit  104  is not limited thereto. The storing unit  104  may store a mapping table between the aforementioned moving speed S or recalculated moving speed S′ and the first period T 1 . The power supplying unit  105  may be controlled by the controlling unit  101  and turn on or turn off power supplied to the storing unit  104  and the position information receiving unit  103 . 
         [0047]      FIG. 3  is a flowchart of a method of recording the position of the mobile device  100 , according to an embodiment of the present invention. In operation  301 , a moving speed S of the mobile device  100  is calculated. The moving speed S of the mobile device  100  may be calculated as described with respect to  FIG. 1 . If the moving speed S is not higher than a first speed S 1  in operation  302 , the frequency of recording of the position information of the mobile device  100  is decreased in operation  303 . 
         [0048]    If the moving speed S is higher than a second speed S 2  in operation  304 , the frequency of recording of the position information of the mobile device  100  is increased in operation  305 . If the moving speed S is higher than the first speed S 1  and lower than the second speed S 2  in operation  304 , the frequency of recording of the position information of the mobile device  100  changes exponentially according to the moving speed of the mobile device  100  in operation  306 . Operations  303 ,  305 , and  306  may be performed by adjusting the first period T 1  for determining whether the position information of the mobile device  100  is recorded, as described with respect to  FIG. 1 . 
         [0049]      FIG. 4  is a flowchart of another method of recording the position of a mobile device, according to another embodiment of the present invention. Referring to  FIG. 4 , Operations  404  through  409  of  FIG. 4  are similar to Operations  301  through  306  of  FIG. 3 . The process of  FIG. 4  further includes an operation for receiving an interrupt signal, and for recording the position information of the mobile device  100  by the received interrupt signal, before calculating the moving speed S of the mobile device  100 , as in the embodiment described with reference to  FIG. 3 . 
         [0050]    Referring to  FIG. 4 , the interrupt signal is received in operation  401 . The interrupt signal may be generated in a similar manner to the timer interrupt signal described with reference to  FIG. 1 . The interrupt signal may be received every second period T 2 , which may have a constant period. The relationship between the first period T 1  and the second period T 2  is as explained with reference to  FIG. 1 . When the interrupt signal is received, whether time corresponding to the first period T 1  has passed since the prior interrupt signal of the interrupt signal is received is determined in operation  402 . 
         [0051]    If the time corresponding to the first period T 1  has passed, position information of the mobile device  100  is recorded in operation  403 . Then, operations  404  through  409  are performed in a similar manner to operations  301  through  306  of  FIG. 3 . 
         [0052]      FIG. 5  is a flowchart of still another method of recording the position of a mobile device, according to another embodiment of the present invention. Operations  501  through  508  of  FIG. 5  are similar to operations  401  through  405  and  407  through  409  of  FIG. 4 . The process of  FIG. 5  differs from that of the process of  FIG. 4  when the moving speed S is not higher than the first speed S 1 . 
         [0053]    When the moving speed S is not higher than the first speed S 1 , a position information receiving function and a position information recording function of the mobile device are turned off in operation  509 . After the functions are turned off, if the time corresponding to the first period T 1  has passed in operation  510 , the functions are turned on, and the moving speed is recalculated in operation  511 . 
         [0054]    If the recalculated moving speed S′ is not higher than the first speed S 1 , the functions are turned off, and a wait state is maintained for the first period T 1  in operations  512 ,  509  and  510 . If the recalculated moving speed S′ is higher than the first speed S 1 , the position information of the mobile device  100  is recorded in the storing unit  104 , and the first period T 1  is changed in operation  513 , as explained with reference to  FIG. 1 . 
         [0055]    The position information of  FIGS. 3 through 5  may be based on GPS coordinates. 
         [0056]    Aspects of the present 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 that can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CDs, DVDs, Blu-ray discs, magnetic tapes, floppy disks, and optical data storage devices. Additional aspects of the present invention may be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
         [0057]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.