Power Control for Cognitive Radios in Nakagami Fading Channels with Outage Probability Requirement

We study and propose power control schemes for cognitive radios in Nakagami fading channels. A general model is adopted, which includes the effects of transmit power control from the primary user (PU) transmitter, as well as the transmit power control from multiple secondary user (SU) transmitters, to the PU and each SU. We found that for high signal-to-interference-ratio (SIR) case in Nakagami and Rayleigh fading channels, the outage probability constraint can be upper bounded by an equivalent interference constraint, and the problem for maximizing the total SU spectrum utility can be written as a convex optimization problem which can be solved efficiently. An iterative power control scheme is also presented to maximize the total spectrum utility of the SUs, and to guarantee the quality of service (QoS) of the PU in terms of outage probability.