Efficient Discovery of Spectrum Opportunities with MAC-Layer Sensing in Cognitive Radio Networks

• Authors: Hyoil Kim;Kang G. Shin
• Venue: IEEE Transactions on Mobile Computing
• Year: 2008

Sensing/monitoring of spectrum-availability has been identified as a key requirement for dynamic spectrum allocation in cognitive radio networks. One of the most important issues of MAC-layer sensing is how often to schedule concurrent measurements on licensed channels, and in which order to sense those channels. To resolve this issue, we address (i) how to maximize discovery of spectrum-opportunities by sensing-period adaptation, and (ii) how to minimize the delay in finding an available channel. Specifically, we develop a sensing-period optimization mechanism and an optimal channel-sequencing algorithm, as well as an environment-adaptive channel-usage pattern estimation method. Our simulation results demonstrate the efficacy of the proposed schemes and its significant performance improvement over non-optimal schemes. The sensing-period optimization discovers more than 98% of the analytical maximum of discoverable spectrum-opportunities, regardless of the number of channels sensed. For the scenarios tested, the proposed scheme is shown to discover up to 22% more opportunities than non-optimal schemes, which may become even greater with a proper choice of initial sensing-periods. The idle-channel discovery delay with the optimal channel-sequencing technique spans from 0.08 to 0.35 second under the tested scenarios, which is faster than non-optimal schemes. Moreover, our estimation method is shown to track time-varying channel-parameters accurately.