Abstract: Cognitive radio networks (CRNs) have been recognized as an advanced and promising paradigm to address the spectrum under-utilization problem. Cognitive Radio (CR) users improve spectrum efficiency by opportunistic spectrum access when the licensed spectrum is not occupied by the primary users (PUs). CR users also need to sense the spectrum and vacate the channel upon the detection of the PUís presence to protect PUs from harmful interference. this paper presents CH algorithm calculate the BER in cognitive radio networks different modulation techniques used in CH algorithm We evaluate the performance of our algorithm through analysis and MATLAB simulations.

Keywords: cognitive radio; quadrature amplitude modulation; bit error rate.