RADIO COMMUNICATION SYSTEM AND RADIO COMMUNICATION DEVICE

PROBLEM TO BE SOLVED: To enable each transmission device to optimally perform data transmission with mutually different priorities, with the provision of a radio communication device capable of performing data communication with an intermediate priority among transmission devices in a radio communication system having a device of periodic transmission mixed with a device of random transmission.SOLUTION: An on-road device performs periodic transmission at a constant communication period in a preset transmission period. A preferential on-vehicle device acquires the periodic transmission information of the on-road device and another preferential on-vehicle device through each transmitter and a random transmitter, and sets the self-periodic transmission period to perform periodic transmission so that the transmission period does not overlap with the on-road device and the other preferential on-vehicle device. Also, the random transmitter acquires the periodic transmission information of the on-road device and the other preferential on-vehicle device with the similar procedure to the preferential on-vehicle device, and performs random transmission by the CSMA system, in a transmission period not overlapped with the periodic transmission period obtained from the periodic transmission information. Further, the preferential on-vehicle device changes the periodic transmission period when the transmission period overlaps with the on-road device and the other preferential on-vehicle device.