The invention provides a radio base station apparatus forming a wireless zone in a mobile communication system and to a base station controller performing channel control over a terminal visiting a wireless zone. The radio base station apparatus has an identifying section identifying a particular radio base station that is to maintain a radio channel between the radio base station apparatus and a terminal during a process of diversity handover, a network interface section delivering a signal to a network if a local station is not the particular radio base station, and an inter-office interface section delivering to the network a composite wave of the signal and a signal having arrived and forwarded from the terminal via the radio channel at a radio base station forming a wireless zone adjacent to a wireless zone formed by the local station if the local station is the particular radio base station.