A communication system (1) includes a mobile communication network (2); a fixed communication network (3) connected to the mobile communication network (2); and a plurality of radio base stations capable of communicating with a mobile terminal (100) by radio communication. The radio base stations include a first base station (41, 42) connected to the mobile communication network (2); and second base stations (51, 52) connected to the fixed communication network (3) through wire communication lines (61, 62). A communication connection using a predetermined interface is established between one of the second base stations (51) and one of neighboring base stations (the first base station (42) and another one of the second base stations (52)) located in the neighborhood of the one of the second base stations (51).