MOBILE COMMUNICATION SYSTEM, RADIO BASE STATION APPARATUSES, CELL AREA COOPERATIVE CONTROL METHOD AND PROGRAMS

Provided is a mobile communication system that reduces the possibility of occurrence of communication quality degradation or disconnection in mobile station terminals during communication in related cell areas, when recovery (expansion and reduction) of coverage areas that have been changed for a radio base station in a service halt state is executed. The mobile communication system comprises: a first radio base station apparatus transmitting, after recovering from a service halt state and before starting to execute a stepwise cell area expansion, a notification including an instruction for a cell area reduction corresponding to the cell area expansion to a neighboring second radio base station apparatus; and a second radio base station apparatus reducing a cell area that has been expanded during the service halt state of the first radio base station apparatus, in accordance with the instruction for a cell area reduction included in the notification transmitted from the first radio base station apparatus.