A new transmit power control scheme in cognitive radio system based on location information of primary user

In wireless communications, efficient use of spectrum is most challenging task. Cognitive radio is a promising technology to overcome the spectrum scarcity problem and provide efficient way of utilizing spectrum resources by dynamic spectrum access (DSA). In this paper, we have considered the situation where primary user (PU) i.e. licensed user and secondary user (SU) i.e. cognitive radio, share the spectrum simultaneously. We have developed a mathematical model for probability of detection as a function of distance between PU transmitter and SU transmitter. We have used this model to adjust the transmit power of SU while maintaining a quality-of-service for the PU by limiting the interference generated by SU.