Adaptive MAC-layer Sensing of Spectrum Availability in Cognitive Radio Networks

In the recently-suggested dynamic spectrum allocation policy of cognitive radio networks [1]–[3], sensing/monitoring of spectrum availability is identified as a key requirement. To meet this requirement we address an important MAC-layer sensing issue: which of proactive and reactive sensing is more energy-efficient? An algorithm is proposed to dynamically determine which sensing mode to use. For proactive sensing, sensing-period adaptation to maximize discovery of opportunities and optimal-ordering of channels to minimize the delay in finding an available channel are proposed. Channel-usage patterns are also estimated. Our simulation results demonstrate the efficacy of the proposed sensing scheme, as well as its performance improvements over the previously-proposed schemes. The sensing-period adaptation discovers up to 98% of the analytical maximum of spectral opportunities, regardless of choice of the initial sensing period. For the testing scenario and simulation parameters we used, the proposed scheme is shown to discover up to 20% more opportunities than the previous sensing schemes without sensing-period adaptation. This improvement may become greater as the initial sensing period grows. The delay in finding an idle channel with the proposed channel-ordering is around 0.02 second, which is a half of the delay without channel-ordering, and the proposed scheme yields steady performance over a wide range of the number of channels.