Abstract:
Provided is a method and apparatus for acquiring time information from a CDMA system in a mobile communication terminal. The method includes: searching for a CDMA channel in a predetermined manner when a CDMA modem or module is activated; receiving a sync channel signal via the searched CDMA channel and extracting time information from the sync channel signal; and setting a time of the mobile communication terminal using the extracted time information. Therefore, even when the mobile communication terminal communicates with a system that does not provide time information, the mobile communication terminal can precisely maintain its time by acquiring time information from a CDMA system.

Description:
PRIORITY  
       [0001]     This application claims priority under 35 U.S.C. § 119 to an application filed in the Korean Intellectual Property Office on Mar. 31, 2006 and allocated Serial No. 2006-29421, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to a mobile communication terminal, and more particularly, to a method and an apparatus for acquiring time information from a synchronous system such as a code division multiple access system.  
         [0004]     2. Description of the Related Art  
         [0005]     The second generation (2G) mobile communication system and method mainly involves voice services and includes a Global System for Mobile communications (GSM) and an Interim Standard 95 (IS-95). The GSM service has been commercialized mainly in Europe since 1992. The GSM service is based on a Time Division Multiple Access (TDMA) method. The IS-95 service has been commercialized mainly in Korea and the U.S.A. using a Code Division Multiple Access (CDMA) method.  
         [0006]     Meanwhile, the third generation (3G) mobile communication system and method supports packet services as well as voice services. The third generation mobile communication service is based on the CDMA method. The third generation mobile communication method includes a 3rd Generation Project Partnership (3GPP) or Wideband Code Division Multiple Access (WCDMA) method, and 3rd Generation Project Partnership 2 (3GPP2) or CDMA2000 method. The 3GPP or WCDMA method utilizes asynchronous inter-base station operation and is selected as a standard 3 G communication method in Europe and Japan. The 3GPP2 or CDMA2000 method utilizes synchronous inter-base station operation and is selected as a standard 3 G communication method in the U.S.A. The 3GPP proposes Frequency Division Duplex (FDD) and Time Division Duplex (TDD) for uplink/downlink transmission in order to efficiently use limited channel resources.  
         [0007]     With the development of communication technologies, various mobile communication systems employing various communication schemes have been commercialized. That is, the current mobile communication environment is subjected to various communication schemes. For this reason, terminals compatible with a plurality of communication schemes have been developed. For example, referring to  FIG. 1 , a WCDMA cell  100  and a CDMA cell  110  overlap each other, and a mobile terminal  101  compatible with WCDMA and CDMA methods has been developed for use in that communication environment.  
         [0008]     Meanwhile, the time of a mobile communication terminal can be set manually by a user or automatically set using time information contained in an air message received from a communication service provider. In a mobile communication terminal compatible with at least one communication method, for example, a mobile communication terminal compatible with WCDMA and CDMA methods, an operation for calculating and setting time is performed each time the terminal switches between WCDMA and CDMA since WCDMA and CDMA systems provide different time information.  
         [0009]     Although the CDMA system sends exact time information to the mobile communication terminal, the WCDMA system may not send time information to the mobile terminal or may send non-exact time information. Therefore, it is difficult for the mobile communication terminal to precisely maintain its time while operating in the WCDMA mode.  
         [0010]     Further, in the case of a mobile communication terminal supporting GSM/GPRS (General Packet Radio Service), a user must manually set the time of the mobile communication terminal since the GSM/GPRS system does not provide time information.  
       SUMMARY OF THE INVENTION  
       [0011]     An object of the present invention is to substantially solve at least the above problems and/or disadvantages and to provide at least the advantages below. Accordingly, an object of the present invention is to provide a method and an apparatus for acquiring time information from a CDMA system in a mobile communication terminal.  
         [0012]     Another object of the present invention is to provide a method and an apparatus for acquiring time information from a CDMA system in a mobile communication terminal having at least one modem chip compatible with CDMA and GSM/GPRS/WCDMA systems. Although the GSM/GPRS/WCDMA system does not always provide time information, the mobile communication terminal can precisely maintain its time while operating in GSM/GPRS/WCDMA mode by acquiring time information from the CDMA system.  
         [0013]     A further another object of the present invention is to provide a method and an apparatus for acquiring time information from a CDMA system, periodically or when a call is set up or when power is applied, in a mobile communication terminal.  
         [0014]     A still further another object of the present invention is to provide a method and an apparatus for a mobile communication terminal to use time information of a CDMA system prior to use of time information of a GSM/GPRS/WCDMA system.  
         [0015]     According to one aspect of the present invention, a method of acquiring time information from a CDMA (Code Division Multiple Access) system in a mobile communication terminal includes searching for a CDMA channel in a predetermined manner when a CDMA modem or module is activated; receiving a sync channel signal via the searched CDMA channel and extracting time information from the sync channel signal; and setting a time of the mobile communication terminal using the extracted time information.  
         [0016]     According to another aspect of the present invention, a method of acquiring time information from a CDMA system in a mobile communication terminal includes when the mobile communication terminal operates in a call mode and receives a handover command message containing information about a CDMA channel from a network, determining whether a call ends; if so, activating a CDMA modem or module; receiving a sync channel signal via the CDMA channel and extracting time information from the sync channel signal; and setting a time of the mobile communication terminal using the extracted time information.  
         [0017]     According to a further another aspect of the present invention, a method of setting a time of a mobile communication terminal depending on a type of acquired time information includes when time information is received from a CDMA system, setting the time of the mobile communication terminal using the time information; and if time information is not received from a CDMA system, determining whether time information is received from another system, and if so, setting the time of the mobile communication terminal using the time information received from another system. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:  
         [0019]      FIG. 1  shows an example of a mobile communication environment using different communication methods;  
         [0020]      FIGS. 2A and 2B  are block diagrams of mobile communication terminals each compatible with different mobile communication systems according to the present invention;  
         [0021]      FIG. 3  is a flowchart illustrating a method of acquiring time information from a CDMA system in a mobile communication terminal according to a first embodiment of the present invention;  
         [0022]      FIG. 4  is a flowchart illustrating a method of acquiring time information from a CDMA system in a mobile communication terminal according to a second embodiment of the present invention; and  
         [0023]      FIG. 5  is a flowchart for explaining a method of setting the time of a mobile communication terminal based on the type of acquired time information according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Preferred embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.  
         [0025]     Hereinafter, a method of acquiring time information from a CDMA system in a mobile communication terminal will now be more fully described according to the present invention. CDMA system is a synchronous system and sends exact time information to the mobile communication terminal.  
         [0026]      FIGS. 2A and 2B  are block diagrams of mobile communication terminals each compatible with different mobile communication systems according to the present invention. Referring to  FIG. 2A , the mobile communication terminal includes at least one modem chip supporting a single communication method such that the mobile communication terminal can be used for at least one communication method. Referring to  FIG. 2B , the mobile communication terminal includes a single modem chip supporting at least one communication method such that the mobile communication terminal can be used in at least one communication method.  
         [0027]     For example, the mobile communication terminal of  FIG. 2A  includes two modem chips, one for GSM/GPRS/WCDMA and the other for CDMA. Hereinafter, this mobile communication terminal will be referred to as a two-chip mobile communication terminal. In detail, the two-chip mobile communication terminal includes a GSM/GPRS/WCDMA connection module  210  and a CDMA connection module  220 . The GSM/GPRS/WCDMA connection module  210  includes a first RF/IF unit  201  and a GSM/GPRS/WCDMA modem chip  203  so as to support the GSM/GPRS/WCDMA method. The CDMA connection module  220  includes a second RF/IF unit  211  and a CDMA modem chip  213  so as to support the CDMA method.  
         [0028]     In another example, the mobile communication terminal of  FIG. 2B  uses only one modem chip for GSM/GPRS/WCDMA and CDMA methods. Hereinafter, this mobile communication terminal will now be referred to as a single-chip mobile communication terminal. In detail, the single-chip mobile communication terminal includes a GSM/GPRS/WCDMA/CDMA connection module  230  supporting both the GSM/GPRS/WCDMA and CDMA methods. The GSM/GPRS/WCDMA/CDMA connection module  230  includes a GSM/GPRS/WCDMA/CDMA modem chip  223  and an RF/IF unit  221 . The GSM/GPRS/WCDMA/CDMA modem chip  223  includes a GSM/GPRS/WCDMA module  225  and a CDMA module  227 .  
         [0029]     When the mobile communication terminals are in a particular communication service area such as a GSM/GPRS/WCDMA service area or a CDMA service area, a corresponding connection chip  210 ,  220 , or  230  transmits and receives signals using its modem chip  203 ,  213 , or  223  according to the particular communication method. For example, referring to  FIG. 2A , when the two-chip mobile communication terminal is powered-on or is carried into a particular communication service area, one of the modem chips  203  and  213  corresponding to the current communication service is booted, and the connection module  210  or  220  having the booted modem chip is activated to transmit and receive signals. In another example, referring to  FIG. 2B , when the single-chip mobile communication terminal is powered-on in a particular communication service area, the modem chip  223  is booted, and one of the modules  225  and  227  of the connection module  230  corresponding to the current communication service is activated to transmit and receive signals in accordance with the current communication service.  
         [0030]     Each of the RF/IF units  201 ,  211 , and  221  decreases the frequency of a RF (radio frequency) signal received through an antenna, performs de-spreading and channel-decoding on the signal, and then sends the signal to a corresponding modem chip  203 ,  213 , or  223 . Further, each of the RF/IF units  201 ,  211 , and  221  performs channel coding and spreading on a signal, increases the frequency of the signal, and then transmits the signal through the antenna.  
         [0031]      FIG. 3  is a flowchart illustrating a method of acquiring time information from a CDMA system in a mobile communication terminal according to a first embodiment of the present invention. The current embodiment describes the time information acquiring method when the mobile communication terminal is in, for example, a non-CDMA service area (serving cell) such as a WCDMA service area. Further, the current embodiment describes the time information acquiring method for a two-chip mobile communication terminal compatible with WCDMA and CDMA methods, for example. However, the present invention is not limited to this embodiment. For example, the method of the present invention can be used for various mobile communication terminals such as a single-chip mobile communication terminal that has at least one chip compatible with multiple mobile communication methods.  
         [0032]     Referring to  FIG. 3 , it is determined whether the mobile communication terminal is powered-on in step  301 . If so, the mobile communication terminal is initialized in step  303 . In the initialization of the mobile communication terminal, to operate in the WCDMA mode, the GSM/GPRS/WCDMA connection module  210  is activated by booting the GSM/GPRS/WCDMA modem chip  203 . That is, the mobile communication terminal is ready for operating in WCDMA mode. In case of the single-chip mobile communication terminal supporting GSM/GPRS/WCDMA/CDMA methods, the GSM/GPRS/WCDMA/CDMA connection module  230  is activated by booting the GSM/GPRS/WCDMA/CDMA modem chip  223  for initialization. Here, the single-chip mobile communication terminal boots only the GSM/GPRS/WCDMA module  225  for operating in GSM/GPRS/WCDMA mode.  
         [0033]     In step  305 , the CDMA connection module  220  is activated by booting the CDMA modem chip  213 . In case of the single-chip mobile communication terminal supporting GSM/GPRS/WCDMA/CDMA methods, the CDMA module  227  of the GSM/GPRS/WCDMA/CDMA modem chip  223  is activated.  
         [0034]     In step  307 , the mobile communication terminal searches for a CDMA channel to find a surrounding CDMA system. The mobile communication terminal can search for the CDMA channel using three methods. In a first method, since the frequency band of the CDMA service in one country is largely different from one service provider to another, all frequency ranges used for CDMA are searched at predetermined intervals corresponding to the representative width of frequency bands of CDMA service providers. Further, since only predetermined portions of each CDMA frequency band are used for CDMA channels, the mobile communication terminal finds an available CDMA channel by searching a CDMA frequency band having at least one operating frequency. In other words, the mobile communication terminal detects the frequency bands of CDMA providers and determines the first CDMA channel found in the detected frequency bands as the available CDMA channel of the surrounding CDMA system. Here, since the width of the frequency bands of CDMA service providers are different from one country to another, the representative width of the frequency bands of CDMA service providers are determined by the bandwidth of a most frequently used frequency band of the communication service providers.  
         [0035]     In a second method, CDMA channel lists are stored in the mobile communication terminal for each CDMA service providing country, and the mobile communication terminal receiving the GSM/GPRS/WCDMA service determines the current country using a Mobile Country Code (MCC) and a Mobile Network Code (MNC). Then, the mobile communication terminal finds an available CDMA channel using the CDMA channel list corresponding to the current country.  
         [0036]     When the use of the mobile communication terminal is limited to a domestic area or a particular country, the mobile communication terminal stores a Preferred Roaming List (PRL) containing CDMA channel information. Therefore, in a third method, the mobile communication terminal searches for an available CDMA channel by starting with a channel having the highest priority in the PRL.  
         [0037]     In step  309 , the mobile communication terminal receives signals from the searched CDMA system through a pilot channel, a sync channel, and a paging channel. In step  311 , the mobile communication terminal detects time information from the sync channel signal received from the CDMA system and sets its time using the detected CDMA system time. In step  313 , the CDMA connection module  220  is deactivated. In the case of the single mobile communication terminal supporting the GSM/GPRS/WCDMA/CDMA methods, the CDMA module  227  of the GSM/GPRS/WCDMA/CDMA modem chip  223  may be deactivated to deactivate the GSM/GPRS/WCDMA/CDMA connection module  230 .  
         [0038]     In step  315 , the mobile communication terminal determines whether a predetermined time period has elapsed. If so, the mobile communication terminal proceeds back to step  305  where the CDMA connection module  220  is activated. The mobile communication terminal performs the next steps in the same way to receive CDMA system time and reset its time using the newly received CDMA system time. After that, the mobile communication terminal terminates the process shown in  FIG. 3 .  
         [0039]      FIG. 4  is a flowchart illustrating a method of acquiring time information from a CDMA system in a mobile communication terminal according to a second embodiment of the present invention. The current embodiment describes the case where a mobile communication terminal ends a call and acquires CDMA system time when the mobile communication terminal receives a handover command to a CDMA cell from a network in call mode. The current embodiment describes the time information acquiring method when the mobile communication terminal is in, for example, a non-CDMA service area (serving cell) such as a WCDMA service area. Further, the current embodiment describes the time information acquiring method for a two-chip mobile communication terminal compatible with WCDMA and CDMA methods, for example. However, the present invention is not limited to this embodiment. For example, the method of the present invention can be used for various mobile communication terminals such as a single-chip mobile communication terminal that has at least one chip compatible with multiple mobile communication methods.  
         [0040]     Referring to  FIG. 4 , in step  401 , the mobile communication terminal operates in call mode (dedicated state) upon a user key input. Here, the mobile communication terminal periodically sends a measurement reporting message to a connected network. The network checks the call quality of the mobile communication terminal using the measurement reporting message, such that the network can determine whether a handover occurs. The measurement reporting message contains information about a serving cell and neighboring cells. In detail, from the measurement reporting message, the network acquires information about the frequency of the serving cell, the Rx signal level and Rx signal quality level from the serving cell, the number of the neighboring cells, the Rx signal level at a frequency of each of the neighboring cells, and Base Station Identity Codes (BSIC).  
         [0041]     In step  403 , it is determined whether the mobile communication terminal receives a handover command message for transferring to a CDMA cell from the network. In detail, when the network determines that the call quality of the mobile communication terminal is not good, the network selects a neighboring cell to which the mobile communication terminal is handed over with reference to the measurement reporting message and sends the handover-command to the mobile communication terminal to transfer the mobile communication terminal to another cell. The handover-command message contains newly allotted channel information for the mobile communication terminal. If the mobile communication terminal does not receive the handover command message, the mobile communication terminal continues to operate without change.  
         [0042]     If the mobile communication terminal receives the handover command message, the mobile communication terminal proceeds to step  405  where the mobile communication terminal boots the CDMA modem chip  213  and waits in a low power mode. Meanwhile, in the case of a single-chip mobile communication terminal compatible with GSM/GPRS/WCDMA/CDMA methods, the single-chip mobile communication terminal boots the GSM/GPRS/WCDMA/CDMA modem chip  223  when it is powered-on. It is not required for the single-chip mobile communication terminal to boot the CDMA chip  227  in this step. Here, in a GSM/GPRS/WCDMA cell, the single-chip mobile communication terminal activates only the GSM/GPRS/WCDMA module  225  of the GSM/GPRS/WCDMA/CDMA modem chip  223 .  
         [0043]     In step  407 , it is determined whether a key input occurs for ending the call. If so, the mobile communication terminal activates the CDMA modem chip  213  to activate the CDMA connection module  220  in step  409 . In step  411 , the mobile communication terminal receives signals from a pilot channel, a sync channel, and a paging channel that are allotted to the mobile communication terminal by the network. The sync channel signal contains information about CDMA system time. Meanwhile, in the case of the single-chip mobile communication terminal compatible with GSM/GPRS/WCDMA/CDMA methods, the CDMA module  227  of the GSM/GPRS/WCDMA/CDMA modem chip  223  may be activated to activate the CDMA connection module  230 .  
         [0044]     In step  413 , the mobile communication terminal extracts the time information from the sync channel signal and sets its time using the extracted time information. In step  415 , the CDMA connection module  220  is deactivated. In the case of the single mobile communication terminal supporting the GSM/GPRS/WCDMA/CDMA methods, the CDMA module  227  of the GSM/GPRS/WCDMA/CDMA modem chip  223  may be deactivated to deactivate the GSM/GPRS/WCDMA/CDMA connection module  230 .  
         [0045]     In step  417 , the mobile communication terminal determines whether a predetermined time period has elapsed. If so, the mobile communication terminal proceeds back to step  409  where the CDMA connection module  220  is activated. The mobile communication terminal performs the next steps in the same way to receive CDMA system time and reset its time using the newly received CDMA system time. After that, the mobile communication terminal terminates the process shown in  FIG. 4 .  
         [0046]      FIG. 5  is a flowchart for explaining a method of setting the time of a mobile communication terminal based on the type of acquired time information according to the present invention.  
         [0047]     Referring to  FIG. 5 , in step  501 , it is determined whether the mobile communication terminal receives time information from a WCDMA, GSM, or GPRS system. If not, the mobile communication terminal proceeds to step  509  where the time of the mobile communication terminal is manually set by a user using keys.  
         [0048]     If so, the mobile communication terminal determines whether the time information is from a CDMA system in step  503 . If so, the mobile communication terminal sets its time with the time information of the CDMA system in step  507 . If not, the mobile communication terminal proceeds to step  505  where the time of the mobile communication terminal is set using the time information received from the WCDMA, GSM, or GPRS system. After that, the process of  FIG. 5  ends.  
         [0049]     As described above, the time acquiring method of the present invention applies to a mobile communication terminal compatible with the CDMA method and the GSM/GPRS/WCDMA method. According to the time acquiring method of the present invention, the mobile communication terminal can acquire time information from a CDMA system while operating in GSM/GPRS/WCDMA mode. Therefore, although the GSM/GPRS/WCDMA method does not always provide time information, the mobile communication terminal can precisely maintain its time while operating in GSM/GPRS/WCDMA mode since time information can be acquired from the CDMA system.  
         [0050]     While the invention has been shown and described with reference to certain preferred 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.