Patent ID: 7710917

Claim:
A mobile communication system comprising: a relay device capable of delivering data signals that are received to a network in response to data signals addressed to a predetermined multicast group transmitted from a transmitter, and of delivering various kinds of requests received from the network to a transmitter side and to the network; a plurality of radio base stations connected to the relay device, and capable of delivering the data signals delivered from the relay device to the network; and a mobile terminal that receives the data signals delivered from the radio base station, the mobile terminal including means for transmitting a path formation request which includes group identification data for identifying a predetermined multicast group at the time of taking part in the predetermined multicast group and at the time of switching over a radio base station to which it is connected while receiving data signals transmitted being addressed to the predetermined multicast group, the path formation request further requesting formation of a path for receiving the delivery of the data signals, wherein each of the radio base stations includes, first means for detecting various kinds of requests inclusive of the path formation request transmitted from the mobile terminal, means for transmitting various kinds of requests detected by the first detecting means to the relay device, second means for detecting various kinds of requests delivered from various-requests transmission means in another radio base station, means for registering the group identification data included in the path formation request to a multicast delivery table thereof when the first detecting means detects the path formation request transmitted from the mobile terminal, and deletes the group identification data included in the path formation request from the multicast delivery table thereof immediately without further communication in the network when the second detecting means detects the path formation request transmitted from the transmitting means in the another radio base station, the registering means inhibiting deletion of the group identification data when there remains in the multicast delivery table another mobile terminal in the predetermined multicast group that wishes to continue to receive a multicast packet in the network, and means for transmitting a multicast packet received from the relay device to the network only when the multicast packet received from the relay device is a multicast packet addressed to the multicast group which is the same as the multicast group registered to the multicast delivery table thereof as the group identification data.