Distributed algorithms for sharing spectrum sensing information in cognitive radio networks

Collaborative spectrum sensing in cognitive radio networks mitigates the negative propagation effects of the wireless channel and increases the sensing reliability. Collaborative sensing requires sensors to share their local spectrum sensing information (SSI) with other users. This paper proposes distributed iterative time slot allocation algorithms for SSI sharing on a dedicated common control channel in a cognitive radio ad hoc network scenario. The proposed algorithms are based on a collision detection and acknowledgment scheme. This scheme allows the network nodes to receive knowledge about collisions regarding their transmitted SSI packets. The nodes use this information to update their operating time slots using a probabilistic approach; each node maintains and updates a parameter representing the probability of switching the time slot in case of a collision. Both fixed and adaptive probability based schemes are proposed. The proposed algorithms are proven to converge to a collision-free allocation with probability one if such an allocation exists. Moreover, an analytical expression for the expected convergence time is established. Extensive simulation results illustrating the rapid convergence, excellent performance, and small reporting overhead of the proposed time slot allocation algorithms are provided.