Spectrum monitoring for cognitive radios in Rayleigh fading channel

In-band spectrum sensing requires that the secondary users (SU) periodically suspend their communication in order to determine whether the primary user (PU) has started to utilize the channel or not. In contrast, in spectrum monitoring the SU can detect the emergence of the PU from its own receiver statistics such as receiver error count (REC). Previously it is shown that in AWGN channels, a hybrid spectrum sensing/spectrum monitoring system significantly improves channel utilization of the SUs and detection delay for the PUs. In this paper we investigate the problem of spectrum monitoring in the presence of fading where the SU employs diversity combining to mitigate the channel fading effects. We show that a decision statistic based on the REC alone does not provide a good performance. Next we introduce new decision statistics based on the REC and the combiner coefficients. Simulation results are presented that show significant improvement in system performance.