Performance analysis of power controlled cognitive radio with imperfect Nakagami-m fading CSI

Abstract

In this paper, a work has been carried out to analyse the performance of cognitive radio (CR) users where secondary user (SU) adapts its transmit power according to an activity model of primary user (PU). The performance has been measured in terms of the outage probability of PU and SU where SU is working in spectrum underlay mode. While PU is present in the network, SU's instantaneous transmitting power is controlled such a manner that interference at the primary receiver (PR) end will be less than a threshold limit, otherwise SU transmits the signal at power Pmax. A power control scheme has been proposed where SU maintains a interference constraint on PR end in terms of maximum allowable primary outage. SU imperfectly estimates the channel with PR and controls its transmission power based on the accuracy of this estimation. A MATLAB based simulation test bed has been developed, and performance studies are carried over for Nakagami-m fading channel to show the performance of the power control scheme. Also, SU's maximum achievable channel capacity is shown for various amount of imperfect channel state information (CSI) under some PU outage constraint.