Abstract:
A method of setting up a PS call in a mobile communication system is disclosed, by which a resource waste of a PS call can be reduced. In a mobile communication terminal which sets up a PS call connection to a PS network, an embodiment of the present invention includes the step of deciding whether to maintain the PS call connection according to whether the mobile communication terminal is able to access a domain name system server for the PS network.

Description:
This application claims the benefit of the Korean Patent Application No. P10-2005-0101825, filed on Oct. 27, 2005, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mobile communication, and more particularly, to a method of setting up a PS call in a mobile communication system. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for setting up a PS (packet switched) call for a packet switched data service in a mobile communication system. 
     2. Discussion of the Related Art 
     Generally, the remarkable development of an information communication field brings about rapid changes of information and communication environments. And, a mobile communication terminal is globally used and regarded as a living necessary in the modern society. To cope with the user&#39;s demand according to the global use of the mobile communication terminal, an Internet access function is added to the mobile communication terminal having a general voice communication function. 
     In a 2 nd  generation or higher mobile communication network that supports a packet switched data service, it is possible for a mobile communication terminal to access the Internet via the mobile communication network. 
     A process that a mobile communication terminal accesses the Internet via a mobile communication network according to a related art is explained in brief as follows. 
     First of all, a mobile communication terminal makes a request for a PS call connection to a packet switched data service network. 
     If the PS call connection request is accepted by the packet switched data service network, the PS call connection is established between the mobile communication terminal and the packet switched data service network. After the PS call connection is established, the mobile communication terminal then receives an IP address of a DNS server responsible for the packet switched data service network from the packet switched data service network. 
     However, if an incorrect IP address is transmitted to the mobile communication terminal due to an error of a noise on a radio transmission or if the DNS server is operating erroneously, the mobile communication terminal may be unable to access the DNS server despite the established PS call. 
     Thus, despite the established PS call for an Internet access, the mobile communication terminal is unable to access the DNS server and the Internet access is not achieved. Hence, the established PS call becomes a waste of resource. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a method of setting up a PS call in a mobile communication system that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a method of setting up a PS call in a mobile communication system, by which a resource waste of a PS call can be reduced in case that a mobile communication terminal is unable to access a DNS server due to some reason despite the PS call established for an Internet access. 
     Another object of the present invention is to provide a mobile terminal and a communication system for efficient Internet access. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of setting up a PS call connection to a PS network by a mobile communication terminal according to one aspect of the present invention includes the step of, when the mobile communication terminal is PS call-connected to the PS network, deciding whether to maintain the PS call connection according to whether the mobile communication terminal is able to access a domain name system (DNS) server for the PS network. 
     Preferably, the method can include: attempting the PS call connection, receiving DNS (domain name system) server information from the PS network when the PS call connection is established, deciding validity of the DNS server information, and releasing the PS call connection if the DNS server information is not valid. 
     In another aspect of the present invention, a mobile communication terminal includes an RF communication module to set up a PS call connection to a PS network and a controller to control the RF communication module, wherein the controller decides whether to maintain the PS call connection of the RF communication module according to whether the RF communication module is able to access a domain name system server for the PS network when the PS call connection is set up. 
     In a further aspect of the present invention, a mobile communication system includes a mobile communication terminal, a PS data service supporting node for the mobile communication terminal, and a DNS server for the PS data service supporting node, wherein the mobile communication terminal decides whether to maintain a PS call connection according to whether the mobile communication terminal is able to access the DNS server when a PS call is connected to the PS data service supporting node. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a schematic block diagram of a mobile communication system according to one embodiment of the present invention; and 
         FIG. 2  is a flowchart of a method of setting up a PS call in a mobile communication system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     First of all, the present invention is applicable to CDMA series, GSM (GPRS) series, 2 nd  generation, 2.5 th  generation, 3 rd  generation, 3.5 th  generation, 4 th  generation communication networks and the like if a packet switched data service is available. Hence, the scope of the present invention is not limited to the following description which describes the examples of the present invention. 
       FIG. 1  is a schematic block diagram of a mobile communication system according to one embodiment of the present invention. 
     Referring to  FIG. 1 , a mobile communication system according to one embodiment of the present invention includes a mobile communication terminal  100  and a PS network  300 , all operatively configured and coupled. 
     The mobile communication terminal  100  includes an RF communication module  130  and a controller  150 . It is a matter of course that the mobile communication terminal  100  according to the present invention further includes other additional elements such as a key input module (not shown in the drawing), a display module (not shown in the drawing), a memory module (not shown in the drawing) and the like. Since the additional elements are not directly associated with the present invention, explanations for the additional elements will be omitted in the following description for the convenience of explanation of the present invention. 
     The RF communication module  130  enables the mobile communication terminal  100  to perform mobile communications externally. In particular, the RF communication module  130  enables the mobile communication terminal  100  to perform packet switched data communications. 
     And, the controller  150  plays a role of controlling the overall terminal  100  including the RF communication module  130 . In particular, the controller  150  enables the mobile communication terminal  100  to implement a PS call setup method according to the present invention that will be explained later. 
     Meanwhile, the PS network  300  of the mobile communication system according to the present invention includes a base station  310 , a PS data service supporting node  330  and a DNS (domain name system) server  350 . 
     The base station  310  plays a role in relaying radio communications between the mobile communication terminal  100  and the PS data service supporting node  330 . 
     The PS data service supporting node  330  is a node responsible for a data packet transport between the mobile communication terminal  100  and the PS network  300 . 
     In GPRS (general packet radio service) system, SGSN (serving GPRS support node) plays a role of the PS data service supporting node  330 . In CDMA system, PDSN (packet data serving node) plays a role of the PS data service supporting node  330 . 
     So, any node responsible for a packet transfer between a mobile communication terminal and a network can be regarded as the PS data service supporting node  330  regardless of its name in various mobile communication series and communication generations. 
     The DNS (domain name system) server  350  plays a role in converting a host or domain name on the Internet (or other network) to an IP address. If a user knows a specific host or domain name, the DNS server  350  enables the specific host or domain to be accessed even if the user does not know an IP address of the specific host or domain. Hence, the DNS server  350  facilitates the user to use the Internet (or other network). 
     A method of setting up a PS call in the above-configured mobile communication system according to an embodiment of the present invention is explained with reference to  FIG. 2  as follows. 
       FIG. 2  is a flowchart of a method of setting up a PS call in a mobile communication system according to an embodiment of the present invention. This method is implemented in the system of  FIG. 1 , but can be implemented in other suitable systems. 
     Referring to  FIG. 2 , the mobile communication terminal  100  makes a request for a PS call connection to the PS data service supporting node  330 . [S 10 ] 
     The PS data service supporting node  330  then sends a connection admission message and PS call connection information to the mobile communication terminal  100  in response to the request. [S 20 ] 
     In this case, the PS call connection information includes an IP address of the mobile communication terminal  100 , and information of the DNS server (DNS server information) responsible for the PS data service supporting node  330 . The DNS server information includes an IP address of the DNS server. 
     Subsequently, the mobile communication terminal  100  attempts a connection to the DNS server using the IP address of the DNS server provided in the received DNS service information. [S 30 ] In particular, the mobile communication terminal  100  preferably attempts a TCP (transmission control protocol) connection to 53-port among several ports of the DNS server. 
     Yet, an incorrect IP address of the DNS server may have been transmitted to the mobile communication terminal  100  at step S 20  due to an error such as a nose on a transmission or the DNS server may have been malfunctioning. So, the TCP connection may fail. 
     If the TCP connection with the DNS server  350  fails at step S 40 , the mobile communication terminal  100  determines that the received DNS server information (e.g., the IP address of the DNS server) is not valid due to the TCP connection failure and makes an immediate request for a PS call disconnection to the PS data service supporting node  330 . [S 40 , S 50 ] 
     The PS data service supporting node  330  then transmits a message of admitting the PS call disconnection to the mobile communication terminal  100  in response to the request. So, the PS call connection is released upon direct request. [S 60 ] 
     Meanwhile, if the TCP connection succeeds at step S 40 , the mobile communication terminal  100  maintains the PS call connection. If necessary, the mobile communication terminal  100  can maintain the PS call connection after releasing the TCP connection to the DNS server. [S 40 , S 70 , S 80 ] 
     Accordingly, the present invention is advantageous in effectively reducing a PS call resource waste that may be generated in case that a mobile communication terminal having a PS call connection for an Internet access is unable to access a DNS server due to some reason. The present invention makes a determination on the validity of the DNS service information and forcibly disconnects the PS call if the DNS server information is not valid. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.