Abstract:
A method and apparatus enhances a location update success rate in a mobile communication terminal. The method includes trying the location update, determining whether a reject cause is a major cause when the location update is rejected, retrying the location update using a current location indicator when the reject cause is the major cause, and retrying the location update using a different location indicator when the retried location update is rejected.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     The present application is related to and claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Jan. 10, 2011 and assigned Serial No. 10-2011-0002158, the entire disclosure of which is hereby incorporated by reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a mobile communication system. 
     BACKGROUND OF THE INVENTION 
     As techniques have been developed, a variety of mobile communication terminals which gradually specialize for persons have been provided. In this mobile communication environment, in order to classify communication entities and provide services according to the classified communication entities, the most basic process is performed. That is, a mobile communication terminal is normally recognized on a network to allow a user to use all services provided from the mobile communication terminal. 
     In this example, a method basically used for classifying the user and services the user joins uses a registration process which is performed between the mobile communication terminal and the network during a process of booting the mobile communication terminal after the user inserts a Subscriber Identity Module (SIM) card into the mobile communication terminal. 
     If the registration process is normally performed, it is authenticated that the user is an authorized user and the mobile communication terminal may use services. 
     There is a location update process during this registration process. If the mobile communication terminal must normally perform the location update process, it may use a voice telephone service, a video telephone service, a Short Message Service (SMS), and all the other services well. 
     However, even though the user uses a normal SIM card and a normal mobile communication terminal, there is a problem in that a location update is not normally performed by unknown cause and the mobile communication terminal is shifted to a limited service state due to reject of the location update. 
     Therefore, a method and apparatus for allowing a mobile communication terminal to be not shifted to the limited service state is needed. 
     SUMMARY OF THE INVENTION 
     To address the above-discussed deficiencies of the prior art, it is a primary object to provide at least the advantages described below. Accordingly, a primary aspect of the present disclosure is to provide a method and apparatus for performing a location update in a mobile communication system. 
     Another aspect of the present disclosure is to provide a method and apparatus for providing a normal service to a user by preventing reject of a location update intermittently generated by a network problem even though the user uses a normal SIM card and a normal mobile communication terminal and preventing a limited service state of the mobile communication terminal due to the reject of the location update in a mobile communication system. 
     Another aspect of the present disclosure is to provide a method and apparatus for preventing a service disable state from being generated in a mobile communication terminal when a location update is temporarily rejected due to major cause by a network even though the mobile communication terminal uses a normal International Mobile Subscriber Identity (IMSI) and a normal International Mobile Equipment Identity (IMEI) in a mobile communication system. 
     In accordance with an aspect of the present disclosure, a method of performing, a location update of a mobile communication is provided. The method includes trying the location update, determining whether a reject cause is a major cause when the location update is rejected, retrying the location update using a current location indicator when the reject cause is the major cause, and retrying the location update using a different location indicator when the retried location update is rejected. 
     In accordance with another aspect of the present disclosure, an apparatus for performing a location update of a mobile communication terminal is provided. The apparatus includes a modem for communicating with a different node and a controller for trying the location update through the modem, determining whether a reject cause is a major cause when the location update is rejected, retrying the location update using a current location indicator when the reject cause is the major cause, and retrying the location update using a different location indicator when the retried location update is rejected. 
     Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG. 1  illustrates location update processes which are classified according to an embodiment of the present disclosure; 
         FIG. 2  illustrates a process of performing a location update according to an embodiment of the present disclosure; 
         FIG. 3  illustrates a process of performing a location update using a different location area identity (LAI) according to an embodiment of the present disclosure; and 
         FIG. 4  is a block diagram illustrating a structure of a mobile communication terminal according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 through 4 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system. 
     Hereinafter, a method and apparatus for performing a location update in a mobile communication system according to an embodiment of the present disclosure will be described in detail. 
     The present disclosure relates to a method and apparatus for enhancing a location update success rate in a mobile communication terminal. 
       FIG. 1  illustrates location update processes which are classified according to an embodiment of the present disclosure. 
     Referring to  FIG. 1 , in accordance with the standard, a location update process performed for registering a mobile communication terminal may be classified into the following three processes. 
     Firstly, there is a general location update process  100 . The general location update process  100  may be a location update process performed such that the mobile communication terminal registers its own location on a network. The general location update process  100  may correspond to a process of booting the mobile communication terminal after a user inserts a SIM card into the mobile communication terminal. 
     Secondly, there is a periodic location update process  110 . The periodic location update process  110  may be a location update process performed such that the mobile communication terminal informs its own location to the network at intervals of timer T3212 values defined on the network. 
     Thirdly, there is an IMSI attachment location update process  120 . The IMSI attachment location update process  120  is a process performed for informing the network that an IMSI of the mobile communication terminal is in an active state. The IMSI attachment location update process  120  indicates that an active update state of an inserted SIM card is an updated state and a stored location indicator, that is, a stored LAI is equal to a selected LAI. 
       FIG. 2  illustrates a process of performing a location update according to an embodiment of the present disclosure. 
     Referring to  FIG. 2 , in general, a mobile communication terminal tries a location update for registering its own location after being booted (step  210 ). 
     If the location update succeeds (step  220 ), the mobile communication terminal operates in an idle state and provides a normal service to a user (step  230 ). 
     If the location update does not succeed (step  220 ), the mobile communication terminal operates in a limited service state (step  240 ). The mobile communication terminal may only transmit an emergency call in the limited service state. That is, only the emergency call may be possible. 
     In accordance with the standard, a reject cause of a location update received from a network when a location update of the mobile communication terminal is rejected is classified into the following two general types. 
     Firstly, by way of example, and without limitation, there may be the following causes when the reject cause is a major cause. 
     1) An IMSI is unknown in a Home Location Register (HLR). That is, the HLR determines that an IMSI value of a SIM card is not valid. 
     2) The mobile communication terminal is an illegal Mobile Station (MS). That is, a problem occurs in an IMEI value of the mobile communication terminal or an IMSI value of the SIM card. In this example, the IMSI value or the IMEI value is not valid. 
     3) The mobile communication terminal is illegal Mobile Equipment (ME). That is, a problem occurs in an IMEI value of the mobile communication terminal. That is, the IMEI value is not valid. 
     Secondly, for example, without limitation, there may the following causes when the reject cause is not a major cause, that is, when the location update is rejected by a minor cause. 
     1) A Public Land Mobile Network (PLMN) where the mobile communication terminal is positioned is not permitted at the mobile communication terminal. 
     2) A location area where the mobile communication terminal is positioned is not permitted at the mobile communication terminal. 
     3) Roaming where the mobile communication is positioned is not permitted at the mobile communication terminal. 
     4) A cell suitable for the mobile communication terminal does not exist. 
     If the reject cause is the minor cause (step  250 ), the mobile communication terminal may perform a network registration process according to the respective causes (step  270 ). That is, if the mobile communication terminal discovers a new PLMN or location area, it retries a location update. 
     However, when the reject cause is the major cause (step  250 ), the mobile communication terminal immediately operates in a limited service state. The mobile communication terminal remains in a recovery disable state until a user turns on or off the mobile communication terminal or until the user attaches a SIM card after detaching it (step  260 ). 
     However, even through a problem does not occur in the IMSI of the SIM card and the IMEI of the mobile communication terminal, it occurs temporarily from a network by an unspecified cause. 
       FIG. 3  illustrates a process of performing a location update using a different LAI according to an embodiment of the present disclosure. 
     Referring to  FIG. 3 , a mobile communication terminal tries a location update (step  305 ). 
     If the location update succeeds (step  310 ), the mobile communication terminal operates in an idle state and provides a normal service to a user (step  315 ). 
     If the location update does not succeed (step  310 ) and a reject cause of the location update is not a major cause (that is, a minor cause) (step  320 ), the mobile communication terminal operates according to the standard (step  325 ). 
     If the location update does not succeed (step  310 ) and the reject cause of the location update is the major cause (step  320 ), the mobile communication terminal retries the location update using a current LAI and increases a counter by 1 (e.g., LU Retry Count_Major++;) (step  330 ). Herein, it is assumed that an initial value of the counter is 0. 
     If the retried location update succeeds (step  335 ), the mobile communication terminal operates in the idle state and provides the normal service to the user (step  315 ). 
     However, the retried location update does not succeed (step  335 ), the mobile communication terminal retries the location update using a different LAI until the counter value is 3 (step  340 ), that is, until the total number of times to retry the location update is 4 when the different LAI exists (steps  355  and  360 ). 
     If the location update succeeds during these repeated processes (step  335 ), the mobile communication terminal operates in the idle state and provides the normal service to the user (step  315 ). 
     If the location update does not succeed although these location update processes are repeated, the mobile communication terminal operates in a limited service state (step  345 ). It is possible for the mobile communication terminal to transmit only an emergency call in the limited service state. 
     Before this location update process, the mobile communication terminal determines validity of its own IMSI and IMEI. If the IMSI and IMEI are valid, the mobile communication terminal performs the location update process described above. 
       FIG. 4  illustrates a structure of a mobile communication terminal according to an embodiment of the present disclosure. 
     Referring to  FIG. 4 , the mobile communication terminal includes a modem  410 , a controller  420 , a storage unit  430 , and a location update unit  440 . 
     The modem  410  is a module for communicating with a different device. The modem  410  includes a radio frequency processor, a baseband processor, etc. The radio frequency processor converts a signal received through an antenna into a baseband signal and provides the baseband signal to the baseband processor. The radio frequency processor converts a baseband signal from the baseband processor into a radio frequency signal to be transmitted on a real radio path and transmits the radio frequency signal through the antenna. Radio access technology of the modem  410  is not limited. 
     The controller  420  controls an overall operation of the mobile communication terminal. Particularly, the controller controls the location update unit  440  according to an embodiment of the present disclosure. 
     The storage unit  430  stores programs for controlling the overall operation of the mobile communication terminal and temporary data generated while the programs are executed. 
     The location update unit  440  performs a location update. If the location update succeeds, the location update unit  440  operates in an idle state and provides a normal service to a user. 
     If the location update does not succeed and a reject cause of the location update is not a major cause, the location update unit  440  operates according to the standard. 
     If the location update does not succeed and the reject cause of the location update is the major cause, the location update unit  440  retries the location update using a current LAI. 
     If the retried location update succeeds, the location update unit  440  operates in the idle state and provides the normal service to the user. 
     However, if the retried location update does not succeed, the location update unit  440  retries the location update using a different LAI until the total number of times to retry the location update is 4 when the different LAI exists. 
     If the location update succeeds during these repeated processes, the location update unit  440  operates in the idle state and provides the normal service to the user 
     If the location update does not succeed although these location update processes are repeated, the location update unit  440  operates in a limited service state. It is possible for the mobile communication terminal to transmit only an emergency call in the limited service state. 
     Before the location update process, the location update unit  440  determines validity of its own IMSI and IMEI. If the IMSI and IMEI are valid, the location update unit  440  performs the location update process described above. 
     In the structure described above, the controller  420  may perform the function of the location update unit  440 . The present disclosure includes the controller  420  and the location update unit  440  separately to differentially describe the respective functions thereof. 
     Therefore, when the present disclosure is implemented as a real product, all functions of the location update unit  440  may be performed in the controller  420 . Only some of the functions of the location update unit  440  may be performed in the controller  420 . 
     The present disclosure has an advantage in that the mobile communication terminal may be successfully registered on a network using a different LAI when a location update of the mobile communication terminal is temporarily rejected by a network problem. 
     Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.