Patent Publication Number: US-7899490-B2

Title: Call control method for dual-mode mobile terminals and a dual-mode mobile terminal using the same

Description:
PRIORITY 
     This application is a continuation application of U.S. patent application Ser. No. 10/929,259, filed on Aug. 30, 2004, and claims priority to an application entitled “CALL CONTROL METHOD FOR DUAL-MODE MOBILE TERMINALS AND DUAL-MODE MOBILE TERMINAL USING THE SAME”, filed in the Korean Intellectual Property Office on Jan. 14, 2004 and assigned Ser. No. 2004-0002662, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mobile terminal, and more particularly to a dual-mode mobile terminal that supports both synchronous and asynchronous modes. 
     2. Description of the Related Art 
     The use of mobile terminals has been rapidly increasing around the world. Mobile communication systems, which provide communication services to the mobile terminals, can be mainly divided into a GSM mobile communication system that is primarily used in Europe and a CDMA mobile communication system that is primarily used in North America. The CDMA mobile communication system employs a synchronous data transmission mode and the GSM mobile communication system employs an asynchronous data transmission mode. The synchronous mode achieves synchronization between a transmitter and a receiver using a GPS satellite signal, whereas the asynchronous mode achieves the synchronization using a special chip or software. 
     In some areas, both the synchronous CDMA mobile communication system and the asynchronous GSM mobile communication system provide overlapping mobile communication services. In such areas where the CDMA and GSM mobile communication systems are used together, users need to have CDMA terminals if they wish to receive CDMA services or GSM terminals if they wish to receive GSM services. Dual-mode mobile terminals, which can access both the synchronous CDMA and asynchronous GSM mobile communication systems to receive communication services therefrom, are under development to meet this need. 
     The dual-mode mobile terminal generally operates in one of the synchronous and asynchronous communication modes, and switches between the synchronous and asynchronous communication modes according to user selection. 
     Another dual-mode mobile terminal, which can access both the synchronous CDMA and asynchronous GSM mobile communication systems and operate in the synchronous and asynchronous communication modes at the same time, is also under development. 
     Although dual mode terminals are known in the art, there has been suggested no method or technology for controlling calls in the dual-mode mobile terminals, which can operate in the synchronous and asynchronous communication modes simultaneously, when the terminal receives calls from both the CDMA and GSM mobile communication systems at the same time. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a call control method for mobile terminals and a mobile terminal using the method. 
     In accordance with the present invention, the above and other objects can be accomplished by the provision of a dual-mode mobile terminal capable of accessing a synchronous mobile communication system and an asynchronous mobile communication system, the terminal including a key input unit including a call switching key for switching between a call from the synchronous mobile communication system and a call from the asynchronous mobile communication system and a call end key for ending calls from the mobile communication systems; and a controller for determining, during a communication of one call received from one of the synchronous and asynchronous mobile communication systems in a general communication mode, whether another call is received from the other mobile communication system, and notifying a user of the terminal of the receipt of the other call if it is determined that the other call has been received from the other mobile communication system, and preparing a communication environment for communication of the other call if the call switching key is pressed by the user to allow the user to perform the communication of the other call while maintaining a communication channel that has been established for the communication of the one call. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram showing service areas of mobile communication systems that can be accessed by a dual-mode mobile terminal according to the present invention; 
         FIG. 2  is a block diagram showing the configuration of a dual-mode mobile terminal according to an embodiment of the present invention; 
         FIGS. 3A and 3B  are diagrams showing in detail the configuration of first and second switches provided in the dual-mode mobile terminal of  FIG. 2 , respectively; 
         FIG. 4  is a control flow diagram showing how call control is performed in the dual-mode terminal according to an embodiment of the present invention; and 
         FIG. 5  is an example of a screen of a display unit when call control is performed in the dual-mode terminal according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention unclear. 
       FIG. 1  is a diagram showing service areas of mobile communication systems that can be accessed by a dual-mode mobile terminal according to the present invention. A dual-mode mobile terminal  100  is positioned in a service area covered by both a synchronous mobile communication system  10  and an asynchronous mobile communication system  20 . In the present invention, it is assumed that the dual-mode terminal  100  can simultaneously gain access to synchronous and asynchronous communication systems and receive communication services therefrom. Specifically, the dual-mode terminal  100  can receive calls from the synchronous and asynchronous communication systems  10  and  20 . The dual-mode terminal  100  can also receive SMS messages and various other information from the synchronous and asynchronous mobile communication systems  10  and  20  at the same time. The user of the dual-mode terminal  100  can select a desired one of the synchronous and asynchronous communication systems  10  and  20  and transmit a call to the selected system. 
     In the present invention, while the dual-mode terminal  100  performs the communication of a call received from one of the synchronous CDMA and asynchronous GSM communication systems, if the terminal  100  receives an incoming call from the other system, the terminal  100  notifies the user of the receipt of the incoming call from the other system. When the user is notified of the receipt of the incoming call, the user can then press a call end key or a call switching key. The call end key may be embodied as a call end key for ending a call from the asynchronous mobile communication system and a call end key for ending a call from the synchronous mobile communication system. The call switching key allows the user to suspend current communication of a call received from one of the synchronous and asynchronous communication systems and then to respond to another call received from the other system. 
     According to the present invention, the dual-mode terminal  100  determines whether the user has pressed the call end key or the call switching key, and then performs an operation corresponding to the pressed key. If a call end key is pressed, the dual-mode terminal  100  ends a call received from a mobile communication system (for example, one of the asynchronous and synchronous mobile communication systems) corresponding to the pressed call end key, and transmits a call end message to the mobile communication system. On the other hand, if the call switching key is pressed, the dual-mode terminal  100  suspends current communication of one call and prepares a communication environment for communication of another call by controlling a speaker and a microphone while maintaining a communication channel that has been established for the current communication. The configuration of such a dual-mode terminal will now be described with reference to  FIG. 2 . 
     As shown in  FIG. 2 , the dual-mode terminal  100  includes a synchronous CDMA module  2 , an asynchronous GSM module  4 , a controller  30 , a display unit  40  and a key input unit  42 . The dual-mode terminal  100  further includes a microphone  50 , a speaker  60  and first and second switches  52  and  62  connected respectively to the microphone  50  and the speaker  60 . The first and second switches  52  and  62  respectively, are controlled by control signals from the controller  30 . 
     The controller  30  controls the overall operation of the synchronous CDMA module  2  and the asynchronous GSM module  4 . The synchronous CDMA module  2  includes a CDMA antenna  11 , a transmission/reception separator  12 , a receiver  14 , a transmitter  16  and a CDMA modem  18 . The CDMA antenna  11  is used to transmit and receive radio signals to and from the synchronous CDMA mobile communication network  10  ( FIG. 1 ), and is designed to be sensitive to frequencies used in the CDMA mobile communication network. If a radio signal is received from the CDMA mobile communication network  10  through the CDMA antenna  11 , the received signal is input to the transmission/reception separator  12  in the CDMA module  2 . The transmission/reception separator  12  in the CDMA module  2  outputs the received signal from the CDMA antenna  11  to the receiver  14 . When the transmission/reception separator  12  receives a transmission signal from the CDMA modem  18  via the transmitter  16 , the separator  12  outputs the transmission signal to the CDMA antenna  11 . The transmitter  16  modulates data output from the CDMA modem  18 , and transmits an RF signal carrying the modulated data through the transmission/reception separator  12  and the CDMA antenna  11 . The receiver  14  receives a radio signal through the CDMA antenna  11  via the transmission/reception separator  12  and converts the received signal into an intermediate frequency (IF) signal and demodulates it into data, and then outputs it to the CDMA modem  18 . The CDMA modem  18  modulates an audio signal received through the microphone  50  via a first switch  52  into a radio signal, and demodulates a radio signal received through the receiver  14  into an audio signal and outputs it via a second switch  62  through the speaker  60 . 
     The asynchronous GSM module  4  includes a GSM antenna  21 , a switch  22 , a receiver  24 , a transmitter  26  and a GSM modem  28 . The GSM antenna  21  is used to transmit and receive radio signals to and from the asynchronous GSM mobile communication network  20  ( FIG. 2 ), and is designed to be sensitive to frequencies used in the GSM mobile communication network. If a radio signal is received from the GSM mobile communication network  20  through the GSM antenna  21 , the received signal is input to the switch  22  in the GSM module  4 . The switch  22  in the GSM module  4  outputs the received signal from the GSM antenna  21  to the receiver  24 . When the switch  22  receives a transmission signal from the GSM modem  28  via the transmitter  26 , the switch  22  outputs the transmission signal to the GSM antenna  21 . The GSM system uses a Time Division Duplex (TDD) scheme, such that channels assigned to uplink and downlink are spaced apart from each other by specified time intervals. In the GSM system, a terminal and a base station perform transmission and reception in intervals of time slots so that transmission and reception are not performed in the terminal at the same time. 
     That is, the GSM terminal deactivates its receiver during transmission and deactivates its transmitter during reception. The switch  22  connects an output of the transmitter  26  to the GSM antenna  21  during transmission under the control of the controller  30 . On the other hand, the switch  22  connects the GSM antenna  21  to an input of the receiver  24  during reception under the control of the controller  30 . 
     The transmitter  26  modulates data output from the GSM modem  28  and transmits an RF signal carrying the modulated data through the switch  22  and the GSM antenna  21 . The receiver  24  receives a radio signal through the GSM antenna  21  via the switch  22 , and converts the received signal into an intermediate frequency signal and demodulates it into data, and then outputs it to the GSM modem  28 . The GSM modem  28  modulates an audio signal received through the microphone  50  via a first switch  52  into a radio signal, and demodulates a radio signal received through the receiver  24  into an audio signal and outputs it via a second switch  62  through the speaker  60 . 
     The display unit  40  generally includes a Liquid Crystal Display (LCD) to display various messages, icons and the like under the control of the controller  30 . The key input unit  42  includes various keys including number keys to provide key input data corresponding to a key entered by the user to the controller  30 . According to the present invention, the key input unit  42  may further include a call switching key, a call end key for ending a call received from the asynchronous mobile communication system and a call end key for ending a call received from the synchronous mobile communication system. The CDMA antenna  11  and the GSM antenna  21  may also be embodied as a single antenna. 
     The controller  30  is connected to the synchronous CDMA module  2  and the asynchronous GSM module  4  to control the overall operation of the two modules  2  and  4 . Specifically, the controller  30  allows radio signals to be received and transmitted through the synchronous CDMA module  2  and the asynchronous GSM module  4 . 
     When a call is received through the synchronous CDMA module  2  or the asynchronous GSM module  4 , the controller informs the user of the receipt of the call. If the user responds to the received call, the controller  30  controls the first and second switches  52  and  62  connected respectively to the microphone  50  and the speaker  60  so that the microphone  50  and the speaker  60  are connected to the synchronous CDMA module  2  or to the asynchronous GSM module  4  through which the call is received. Specifically, as shown in  FIG. 3A , the controller  30  applies a microphone control signal to the first switch  52  so that the microphone  50  is connected to one of the CDMA and GSM modems  18  and  28 . In addition, as shown in  FIG. 3B , the controller  30  applies a speaker control signal to the second switch  62  so that the speaker  60  is connected to one of the CDMA and GSM modems  18  and  28 , respectively. 
     While the user performs a communication via one of the synchronous and asynchronous mobile communication systems with which the terminal  100  has been connected through a corresponding one of the synchronous CDMA module  2  and the asynchronous GSM module  4 , if the terminal  100  receives an incoming call from the other mobile communication system, the controller  30  notifies the user of the receipt of the incoming call therefrom. For this notification, the controller  30  may display a predetermined message or icon on the display unit  40  or output an alert or alarm sound. The controller  30  then determines whether the call end key or the call switching key is pressed by the user. If the call end key is pressed, the controller  30  ends a call received from one of the synchronous and asynchronous mobile communication systems corresponding to the pressed call end key, and transmits a call end message to that particular mobile communication system. The controller  30  then controls the first and second switches  52  and  62  so that the microphone  50  and the speaker  60  are connected to one of the CDMA and GSM modems  18  and  28  corresponding to the other of the synchronous and asynchronous mobile communication systems, a call from which has been maintained, thereby allowing the user to perform communication of the call that has been maintained. 
     On the other hand, if the call switching key is pressed, the controller  30  controls the first and second switches  52  and  62  so that the speaker  50  and the microphone  60 , which have been connected to one of the CDMA and GSM modems  18  and  28  for current communication of a call received through the one modem, are connected to the other modem to allow the user to perform communication of another call received through the other modem while maintaining a communication channel established for the current communication. 
     A description will now be given of how call control is performed in the dual-mode mobile terminal with reference to  FIG. 4 . 
     As shown in  FIG. 4 , the controller  30  in the dual-mode terminal is in a general communication mode at step  210 , in which the dual-mode terminal performs a general communication function in response to an incoming call from one of the synchronous and asynchronous mobile communication systems. While the dual-mode terminal performs current communication of the call received from one mobile communication system in the general communication mode, the controller  30  determines at step  220  whether an incoming call is received from the other communication system (i.e., a mobile communication system other than the one mobile communication system with which the current communication has been established). If no incoming call is received from the other mobile communication system, the controller  30  allows the terminal to operate in the general communication mode. On the other hand, if an incoming call is received from the other mobile communication system, the controller  30  moves to step  230  to notify the user of the receipt of the incoming call from the other mobile communication system. For example, the controller  30  notifies the user of the receipt of the different call via a message as shown in  FIG. 5 . In other words, the controller  30  displays the message as shown in  FIG. 5  indicating the receipt of the incoming call from the other mobile communication. Here, the controller  30  may also display a calling telephone number and a received time of the incoming call, together with the message indicating the receipt of the incoming call. 
     The controller  30  then determines at step  240  whether the user has pressed a key on the key input unit  42 . If the user has pressed a key, the controller  30  moves to step  250  to determine whether the pressed key is a call switching key or a call end key. As shown in  FIG. 5 , the controller  30  provides, for example, three key options (i.e., a call switching key  310 , a key  320  for ending a call received from the asynchronous GSM mobile communication system and a key  330  for ending a call received from the synchronous CDMA mobile communication system) to the user so that the user selects a desired key from the three keys  310 ,  320  and  330 . The user selects the call switching key  310  in order to perform a communication while maintaining a call from the synchronous mobile communication system and a call from the asynchronous mobile communication system. On the other hand, the user selects one of the two call end keys  320  and  330  in order to end one of the calls from the synchronous and asynchronous mobile communication systems and then perform communication in a general communication mode. In the example of  FIG. 5 , the two keys  320  and  330  are provided to end the calls from the synchronous and asynchronous mobile communication systems, respectively. Alternatively, only one call end key may be provided to end a call from either of the two mobile communication systems. In this case, if the user has pressed the call end key, the controller  30  may control the first and second switches  52  and  62  to terminate current communication performed through one of the CDMA and GSM modems  18  and  28 , to which the microphone  50  and the speaker  60  have been connected by the first and second switches  52  and  62 . 
     Referring to  FIG. 4 , if the user has pressed a call end key, the controller  30  moves to step  270  to end a call from a mobile communication system (for example, one of the asynchronous and synchronous mobile communication systems) corresponding to the pressed call end key by transmitting a call end message to that mobile communication system. The controller  30  then moves to step  280  to prepare a communication environment for communication of the call that has not been ended. That is, the controller  30  controls the first and second switches  52  and  62  so that the microphone  50  and the speaker  60  are connected to a modem for one of the two mobile communication systems, a call from which has been maintained, thereby allowing the user to perform communication for the call. The controller  30  then returns to step  210  to enter the general communication mode. 
     If the call switching key has been pressed, the controller  30  moves to step  260  to control the first and second switches  52  and  62  so that the speaker  50  and the microphone  60 , which have been connected to one of the CDMA and GSM modems  18  and  28  for the current communication of a call received through the one modem, are connected to the other modem while maintaining the communication channel established for the current communication. This allows the user to perform communication of another call received through the other modem while maintaining the communication channel established for the current communication. The controller  30  then returns to step  240 . 
     As apparent from the above description, the present invention provides a call control method for dual-mode mobile terminals and a dual-mode mobile terminal using the method, whereby the user can receive both a call from a synchronous mobile communication system and a call from an asynchronous mobile communication system, and even when two incoming calls are received simultaneously from two different mobile communication systems, the user can perform communication in response to the two incoming calls. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, the scope of the present invention should not be limited to the above embodiments, but defined by the accompanying claims as well as equivalents thereof.