Patent ID: 7720502

Claim:
A radio device applied to a radio communication system which carries out an access control using a CSMA system, the radio device comprising: a propagation-attenuation calculating unit that calculates a propagation attenuation amount from a received frame, which was transmitted by a transmitting radio device, the propagation attenuation amount being calculated based on reception power and transmission radiation-power information included in the received frame; and a transmission-power controlling unit that calculates optimum transmission power at each transmission rate based on the propagation attenuation amount calculated by the propagation-attenuation calculating unit and minimum necessary reception power determined for each transmission rate, registers each calculated optimum transmission power into an optimum transmission power table by relating the optimum transmission power to a radio device identifier for identifying the transmitting radio device and each transmission rate, and; when a frame is to be transmitted to a transmission destination radio device, performs the following: selects an optimum transmission power to the transmission destination radio device based on the optimum transmission power table, the radio identifier of the transmission destination radio device, and the transmission rate, thereby carrying out a transmission power control of transmitting the selected optimum transmission power as a transmission frame including the selected optimum transmission power as transmission radiation-power information, and detects whether a value smaller than the selected optimum transmission power is registered as the optimum transmission power at the minimum transmission rate of a radio device different from the transmission destination radio device in the optimum transmission power table; and a hidden-terminal avoidance-control executing unit that executes a predetermined hidden-terminal-avoidance control process when the transmission-power controlling unit detects the presence of the smaller value in the optimum transmission power table.