Patent ID: 7376424

Claim:
A method for performing seamless inter-frequency hard handover in a radio communication system, comprising the steps of: a) at a mobile station, disconnecting a first uplink carrier frequency used for communication with a source base station, transmitting a direct sequence spread preamble signal through a second uplink carrier frequency for a short time after receiving a first instruction from a base station controller, and continuously performing the communication through the first uplink carrier frequency, wherein the first instruction includes a transport channel frame number (TGCFN) at which the mobile station starts an uplink preamble transmission, a slot number (TGSN), and compressed mode parameters; b) at a target base station, acquiring an uplink synchronization of the mobile station by using the direct sequence spread preamble after receiving a second instruction from the base station controller, wherein the second instruction includes the TGCFN, the TGSN, the compressed mode parameters, and a scrambling code identification (SCID), thereby allowing the target base station to search the preamble transmitted from the mobile station in a preset time; and c) at the base station controller, after the preamble transmission, transmitting a connection frame number (CFN) of the mobile station to the source base station, the mobile station, and the target base station to instruct performing the hard handover by using the uplink synchronization and establishing communication between the mobile station and the target base station through a new link at the CFN of the mobile station.