Power control in cognitive radio using fuzzy logic

Abstract

Cognitive Radio Networks (CRNs) has the ability to improve the spectrum utilization provided that a fair enough balance is made in achieving goals and user requirements. This research work assumes a spectrum sharing environment in cognitive radio with a set of Primary User (PU) and a set of Secondary User (SU) in a Rayleigh fading environment. The PU link being a licensed user has a preference over SU link and has no concern with the presence or absence of SU link provided that its desired Quality of Service (QoS) is assured. When both links exist on a channel simultaneously, interference is caused. The main challenge lies in determining the performance constraint for the PU. This can be made possible by considering the desired QoS of PU as a constraint on utilizating spectrum. If SU uses an Optimal Power Control Scale while using spectrum, interference can be mitigated and performance can be improved. This research work proposes a Fuzzy Based Optimal Power Control Model which allows SU link to determine its power scale opportunistically as the interference at PU side changes. Proposed model is based on Mamdani Fuzzy Inference System and has two antecedents: The PU Transmit-Receive SNR Ratio and Interference Temperature. Based on these antecedents, a set of Rules are defined to optimize the power scale of SU. Simulations show that Bit Error Rate (BER) is decreased and performance is improved when compared to the spectrum sharing environment with Fixed Step Power Control.