An in-vehicle device receives broadcast data from a base station A, calculates a checksum of the received broadcast data, and transmits the checksum to a base station B. The base station B determines whether the checksum received from the in-vehicle device is correct. If the checksum is not correct, the base station B instructs a base station C to retransmit the broadcast data, and the base station C retransmits the broadcast data to the in-vehicle device.