A base station controller (BSC) performs a handoff of a mobile terminal
(MT) moving between cells of base transceiver stations (BTSs) in a mobile
communication system. If a target BTS is selected as a handoff candidate
for the MT as the MT moves from a cell of a source BTS in service toward
a cell of the target BTS, the BSC transmits to the target BTS a first
message for requesting the target BTS to buffer packets, and transmits
packets to be transmitted to the MT to both the source BTS and the target
BTS. If the target BTS is determined as a serving BTS for the MT, the BSC
transmits to the target BTS a second message including a last sequence
number in order to request the target BTS to transmit, to the MT, packets
with sequence numbers following the last sequence number of a last packet
transmitted from the source BTS to the MT, among the buffered packets.