Patent ID: 8045529

Claim:
A terminal station radio communication device belonging to a second radio communication system which shares a frequency channel with a first radio communication system in which a radio terminal station communicates with a radio base station in a predetermined transmission time period using a predetermined frequency channel, the second radio communication system being allowed to use the frequency channel with lower priority over the first radio communication system, the terminal station radio communication device comprising: a frequency selector for changing frequency channels; a transmission power determining unit which sets up signal transmission power, the signal transmission power being used for communications between radio communication devices belonging to the second radio communication system, and being determined such that reception power at the radio base station is below a predetermined threshold; a synchronizer enabling the terminal station radio communication device belonging to the second radio communication system to acquire timing information to start signal transmission; a signal transmitter starting transmitting the signal at the timing represented in the timing information and terminating the signal transmission within a predetermined time period; and a carrier sensor which detects a carrier signal in a short time period from the timing represented in the timing information obtained from the synchronizer until a lapse of the predetermined time period, and enabling the signal transmitter to send the signal when reception power is found to be below the predetermined threshold during the carrier signal detection.