System for packet data service in the mixed network of asynchronous communication network and synchronous communication network and hand-over method thereof

Disclosed herein is a mobile communication terminal and handover method therefor. In the mobile communication system, a Gateway GPRS Support Node (GGSN) of the asynchronous network is connected to a Packet Data Service Node (PDSN) of the synchronous network. Accordingly, as a mobile communication terminal, using packet data service in the asynchronous mobile communication system, moves into an area of a synchronous mobile communication system, the synchronous mobile communication system sets control signals and traffic to transmit packet data in response to a request from the asynchronous mobile communication system. Further, if forward and reverse channels are assigned between the mobile communication terminal and the synchronous mobile communication system, call setup is performed to provide the packet data service, and then a node B of the asynchronous mobile communication system releases the connection to the mobile communication ninal.