Patent ID: 7843881

Claim:
A handover method for providing a packet data service to a dual-band dual-mode mobile communication terminal having an asynchronous modem unit and a synchronous modem unit in a mobile communication network in which asynchronous and synchronous mobile communication systems coexist, the method comprising: the first step of, as the mobile communication terminal in a dormant state with respect to the asynchronous mobile communication system moves into an area of the synchronous mobile communication system, a Serving General packet radio service (GPRS) Support Node (SGSN)/Gateway GPRS Support Node (GGSN) of the asynchronous mobile communication system receiving information indicating that handover is required; the second step of the SGSN/GGSN commanding a base station of the synchronous mobile communication system to perform handover; the third step of the mobile communication terminal attempting to originate a call to the base station, thus executing call processing and channel assignment between the base station and a mobile switching center of the synchronous mobile communication system; the fourth step of performing a negotiation related to call processing and setup between the mobile communication terminal and the base station; the fifth step of the synchronous mobile communication system setting up a trunk; the sixth step of initializing a radio link protocol between the mobile communication terminal and the base station; the seventh step of the base station notifying the mobile switching center that channel assignment has been completed; the eighth step of setting up a packet data call between the mobile communication terminal and a packet data service node of the synchronous mobile communication system; and the ninth step of the synchronous mobile communication system assigning a mobile IP to the mobile communication terminal.