A Bayesian approach using M-QAM modulated primary signals for maximizing spectrum utilization in cognitive radio

Recently, cognitive radio (CR) has gained a lot of attention with its spectrum sensing feature, because it provides better spectrum utilization in wireless communication. The spectrum sensing plays a major role in CR. In this paper, a new technique of spectrum sensing is proposed in which optimal Bayesian detector is used to detect the presence of M-ary quadrature amplitude modulated primary signal. This proposed approach acts as optimal detector when primary user is idle for most of the time. The analytical expression for detection statistic of the proposed technique over additive white gaussian noise channel is derived and the detection and false alarm probabilities are also calculated. These probabilities are compared with M-ary phase shift keying modulated primary signal scheme. The nature of false alarm probability is also analysed for different priori probability cases. Simulation results show that the proposed approach achieves higher spectrum utilization and also maximizes the throughput of secondary user in the CR network.