A Novel Clock Synchronization Scheme for Hybrid Overlay/Underlay Spectrum Access Based Cognitive Radio Networks

In order to improve the throughput in cognitive radio networks (CRNs) without affecting primary users (PUs), the hybrid overlay/underlay spectrum access mechanism draws lots of attention recently. For such mechanism, this paper proposes a multi- steps cluster-based clock synchronization scheme, which is embedded in the CRN setup progress. Three steps are involved. Firstly, the neighbor/hierarchy is discovered, and the clock synchronization is initialized. Secondly, the clock synchronization is achieved coarsely based on the underlay channel. Finally, the clock synchronization is refined by the hybrid overlay/underlay channels. In each step, a linear joint estimator for clock parameters is derived. Our simulation results show that the proposed clock synchronization scheme performs better than the traditional schemes both in parameters estimation precision and in algorithm convergence speed.