Underutilization of the limited spectrum sparked the need for dynamic spectrum access and flexible spectrum policies. Accurate estimation of spectrum occupancy is an essential step for spectrum access in distributed networks. This paper analyzes a bidirectional and dual scanning method that scans multiple spectrum bands to find a suitable free-channel. Moreover, secondary users' access to available spectrum could be interrupted by the arrival of primary spectrum users, forcing the well-behaved secondary users to switch to another free-channel. A pointer and adaptive reserve channel mechanism is proposed in this paper to facilitate quicker and smoother channel switching. Simulation results for both techniques show improved overall connectivity is maintained for varying primary users' arrival rates.
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