An Efficient Power Control Scheme for Cognitive Radios

In this paper, we design a transmit power control system using fuzzy logic system to provide cognitive radios the ability to coexist with primary (licensed) users in the same frequency band. With our built-in fuzzy power controller, a cognitive radio is able to opportunistically adjust its transmit power in response to the changes of the interference level to primary user (PU), the distance to PU and its received power difference at the base station (BS) while satisfying the requirement of sufficiently low interference to PU. We increase the reliability of our power control scheme by using linguistic knowledge of transmit power control (TPC) obtained from a group of network experts rather than a single expert. Simulation results show that using our proposed fuzzy power control scheme, we can decrease average transmit power consumption and achieve lower average outage probability compared with the fixed-step power control scheme.