Cognitive Spectrum Access with Joint Opportunistic Power and Rate Control in Fading Channels

In cognitive networks, power control is commonly applied to limit the interference caused by the cognitive radio to the primary user’s communication, while rate control seeks the way of rate adaptation that achieves the highest spectrum efficiency. In this paper, we combine these two techniques and jointly consider power and rate control in fading channels. In particular, we propose our joint opportunistic power and rate control (JOPRC) strategy for both single-channel and multi-channel scenarios. Our strategy applies opportunistic interference cancellation in rate adaptation and protects the outage probability on the primary link not to be degraded via opportunistic power adjustment. In multi-channel case, due to both total transmit power constraint and per-channel maximum power constraint, our JOPRC equals finding the solution of an intercepted water- filling problem with floating rocks, and the floating-rock water- filling (FRWF) algorithm is proposed to obtain that solution. Analysis of the ergodic rate of the cognitive user is given by numerical simulations.