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.