Patent ID: 7720493

Claim:
A communication system comprising: a communication terminal device configured to communicate with a mobile terminal; a plurality of low order switching devices included in communication paths between the communication terminal device and the mobile terminal, said plurality of low order switching devices each configured to transmit packet data to a plurality of base stations and a plurality of secondary low order switching devices in a multicast manner; a high order switching device configured to transmit packet data to the plurality of low order switching devices in a multicast manner; wherein the high order switching device includes a first determiner configured to determine a transmission time for the high order switching device and each of the plurality of low order switching devices to transmit the packet data resulting in simultaneous data reception at the mobile terminal, wherein the determination is based on a time period necessary for transmission of the packet data from the high order switching device to each of the plurality of low order switching devices, and a transmission time from each of the plurality of low order switching devices to the plurality of base stations; the high order switching device includes a first transmitter configured to transmit the packet data from the high order switching device to the plurality of low order switching devices, and each of the plurality of low order switching devices includes a first transmitter configured to transmit the packet data from each of the plurality of low order switching devices to the plurality of base stations based on the transmission timing determined by the first determiner; the high order switching device includes a first generator configured to generate a plurality of radio slot data, based on transmission target packet data, wherein said transmission target packet data includes packet data transmitted to the high order switching device, and based on the number of low order switching devices that are destinations of multicast transmission by the high order switching device, the high order switching device further including a second generator configured to generate packet data including radio slot data generated by the first generator; each of the plurality of low order switching devices include a generator configured to generate packet data, based on packet data received from the high order switching device, which includes radio slot data generated by the first generator of the high order switching device; and the high order switching device and each of the plurality of low order switching devices include a second transmitter configured to transmit the packet data including the radio slot data to the plurality of low order switching devices based on transmission timing determined by the first determiner.