Abstract: A radio communication system has a transmitter and a receiver that transmits and receives, respectively, synchronization signals. The transmitter has a multiple-synchronization-signal generation section configured to generate the synchronization signals, a radio circuit configured to transmit the synchronization signals in a predetermined transmission cycle from a start time of the predetermined transmission cycle and with an interval shorter than the predetermined transmission cycle, and a synchronization signal sequence number generation section configured to assign a sequence number to each of the synchronization signals.

Abstract: A frame generation device has a frame generation section that generates a frame including synchronization information for achieving synchronization with a reception device from among a group including one or more reception devices each of which receives information within the frame, address information indicating an address within the frame for transmitting data, and data transmitted to the reception device included in the group. A group-basis distribution data presence/absence information generation section generates group-basis distribution data presence/absence information indicating whether or not the transmitted data is included in the frame. A synchronization information generation section generates synchronization information including the group-basis distribution data presence/absence information. The frame generation section generates the frame such that the group-basis distribution data presence/absence information is allocated prior to the address information.

Abstract: A communication system has a server, base station devices, and terminal devices. The server notifies each base station device of a transmission order of a synchronization signal and of the base station device that is designated as a reference. Each one of the base station devices transmits a synchronization signal to the corresponding terminal device based on the transmission order in a case where the one base station device has been designated as the reference. In the case where the one base station device has not been designated as the reference, the one base station device transmits the synchronization signal to the corresponding terminal device at a timing calculated based on a reception timing by the corresponding terminal device of a synchronization signal received from the reference base station device, a transmission order of the reference base station device, and the transmission order of the one base station device.

Abstract: A distribution data presence/absence information generation section generates distribution data presence/absence information indicating whether or not data is included in a frame. A synchronization information generation section generates synchronization information including the distribution data presence/absence information.