Performance for MAC Level Channel Capacity in Cognitive Radio with Carrier Sense Multiple Access and Transmitting Power Control

In cognitive radio, the mobile terminal senses the wireless accessing of the other wireless communications, specifies the vacant frequency channel, and then tries to use the specified frequency spectrum. In sensing technique, the detection accuracy depends on the detection time and thus the number of detectable systems also depends on it. When the other system is in the undetectable area for the cognitive radio, cognitive radio must protect the wireless access of it. In this paper, we consider the cognitive radio with using carrier sensing and transmitting power control. In considered system, the accessing protocol based on carrier sensing is established for protecting detectable other system. In addition, the transmitting power for suppressing the interference to the undetectable system is controlled. Since the sensing time depends on the detectable area, the transmitting power of cognitive radio transmitter and the opportunity of finding vacant spectrum are changed. Therefore, we derive the optimal sensing time for achieving the largest channel capacity.