In this chapter, the authors present the application of fuzzy logic for power control in spectrum sharing cognitive radio network. The investigated network consists of a pair of primary users (PUs) and a pair of cognitive radio users (CRs). In order to compute an optimal power scale for the CR link, a fuzzy-based optimal power control strategy is investigated based on the Mamdani fuzzy control model using two input variables: the PU’s signal-to-noise ratio (SNR) and PU’s interference channel gain (channel gain from the cognitive radio users to primary users). Applying the fuzzy-based optimal power control strategy, the desired quality of service (QoS) is assured on the PU link, and the efficiency of spectrum usage is also maximized on the CR link in the spectrum sharing network. In addition, the bit error rate (BER) is also improved as compared with the spectrum sharing network without power control.
