Distance based an Efficient Transmit Power Control Scheme in Cognitive Radio System with Multiple Antennas

In this paper, a transmit power control scheme for a cognitive radio system (CRS) in a Rayleigh fading channel based on the location information of primary user is proposed. The situation where primary user (PU) i.e. licensed user share the spectrum with secondary user (SU) i.e. cognitive radio have been considered. First a mathematical model for probability of detection as a function of distance between PU transmitter and SU transmitter is developed. The mathematical model takes into account multiple antennas at SUs and uses energy detection (ED) with selective combining (SC) scheme. The maximum allowable transmit power at SU transmitter, to guarantee decodability of PU transmitter signal at PU receiver,is calculated by using the distancebetween PU transmitter and SU transmitter. The simulation results show that the probability of detection improves with the use of multiple antennas at SU transmitter. This improved probability of detection will result into more accurate calculations of the maximum allowable transmit power at SU transmitter.