Cognitive Radio Networks (CRNs) have been envisioned as a solution for frequency spectrum-scarcity and spectrum misuse issues. Since the requirement for cooperation and dynamism increases with the new spectrum access approach, time synchronization is mandatory for ensuring the proper operation of CRNs. In this paper, we propose DCR-Sync, a novel time synchronization protocol for CRNs. Differently from existing proposals, DCR-Sync is fully distributed and resilient towards failure of root nodes, i.e., the nodes which play the role of master on the synchronization process. We present DCR-Sync in two versions. The first version is static in nature, and the second version can adapt dynamically to network changes. Through extensive simulations, we show that both versions outperform the performance of existing synchronization protocols. Precisely, both versions of DCR-Sync are simulated using NS2 simulator and are compared to the TPSN protocol. Simulation results show the improvements obtained by DCR-Sync in terms of network overhead and convergence time.
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