Power control algorithm for cognitive radio systems

Cognitive radio (CR) is the enabling technology for dynamic spectrum access, which may potentially mitigate the radio spectrum scarcity problem encountered in many countries. This paper is concerned with power allocation spectrum sharing CR networks, where a secondary user (SU) communicates simultaneously over the same frequency band with an existing primary users (PUs) link. In addition, this method uses PU feedback information. It is assumed that the SU transmitter has the perfect channel state information (CSI) on the fading channels from SU transmitter to both PU and SU receivers, as well as the fading channel from PU transmitter to PU receiver. Furthermore, the proposed method takes into account the statistical variation of the signal to interference plus noise ratio (SINR) of each transmitter/receiver pair and optimally allocates power to minimize probability of fading-induced outage probability. Such approaches can guarantee convergence towards the optimal solution with an acceptable convergence speed. Therefore, equipment designers and system operators can use their judgment to find the best SU pairs to meet their specific needs. Simulation results are provided for the optimal power control performance.