Patent ID: 6934545

Claim:
A mobile communication terminal apparatus comprising: measuring means for measuring respective reception qualities of radio signals transmitted from a first base station and a second base station disposed in a periphery of the first base station while synchronization is established with the first base station; handoff determining means for determining whether or not handoff is necessary based on a measurement result of said measuring means; message generating means for generating a first handoff request message if the handoff determining means determines the handoff to be necessary; first selecting means for selecting a usable first sequence number from a plurality of sequence numbers; message transmitting means for transmitting the first handoff request message generated by said message generating means with the selected first sequence number to said first base station; response monitor means for monitoring whether or not an acknowledgment response arrives from said first base station within a predetermined period from a transmission timing of said handoff request message; message retransmitting means for retransmitting said first handoff at least once with the selected first sequence number if the acknowledgment response does not arrive from the first base station within said predetermined period; second selecting means for selecting a usable second sequence number from said plurality of sequence numbers; and message additional transmitting means for transmitting a second handoff request message with the selected second sequence number, the second handoff request message having the same content as that of the first handoff request message transmitted by said message transmitting means to said first base station.