Conflict-Free Opportunistic Centralized Time Slot Assignment in Cognitive Radio Sensor Networks

The unlicensed spectrum bands become overcrowded causing an increased level of interference for current wireless sensor nodes. Cognitive Radio Sensor Networks (CRSNs) overcome this problem by allowing sensor nodes to access opportunistically the underutilized licensed spectrum bands. The sink assigns the spectrum holes to the secondary users (SUs). Therefore, it must rely on reliable information about the spectrum holes to protect the primary users (PUs). In this paper the sink uses two ways to determine the available channels and alerts the SUs if an unexpected activity of PU occurs. Our objective is to design an algorithm able to detect the unexpected presence of PUs in the multi-hop network while maximizing the throughput. To achieve our goal, we propose an optimized version of our previous scheduling algorithm Opportunistic centralized Time slot assignment in Cognitive Radio sensor networks (OTICOR). We then evaluate its performance in terms of number of slots and throughput.