Radio communication system, mobile station, base station and radio network controller

The object of the present invention is to provide a radio communication system which can reduce the load on a radio network controller (50) during multicast communication. The present invention relates to the radio communication system having a radio network controller (50), base stations (10-40) and mobile stations (11-43), to perform multicast communication. The mobile station (11) comprises a response signal transmitter (11b) configured to transmit a response signal including a group ID identifying a multicast group A to the base station (10). The response signal responds to a control signal for the multicast group A which the mobile station (11) is joining in. The base station (10) comprises a response signal transmitter (10c, 10d, and 10e) configured to transmit at least one response signal to the radio network controller (50). The response signal is selected from at least one response signal transmitted from the mobile station (11) joining in the same multicast group A.