PURPOSE: To improve communication efficiency of the real-time data by setting the transmission right in response to the type of data to be transmitted.

CONSTITUTION: When the transmission data are transferred to a radio control part 1 from a data terminal 20, a communication control part 2 stores the data in a memory 4. Then a CPU 3 reads the data out of the memory 4, and a packet assembly/disassembly part 10 disassembles the transmission data into a radio packet of the fixed length and assembles it into a data packet. A data discrimination part 15 discriminates the data type to classify the data of high reality in a rank A when it has high reality and other data in a rank B respectively. Then a carrier-sense operation is applied to a data channel for the data of rank A, and the frequency is shifted to a control channel 1 when no data under transmission exists any more. Then a carrier pulse is transmitted. In regard to the data of rank B, the frequency is shifted to the channel 1 when no data exists on the data channel any more. Then the frequency is shifted to a control channel 2 when no other carrier exist, and the transmission of data is carried out.