Cluster-based Scheduling for Cognitive Radio Sensor Networks

International audienceIn this paper, we define a cluster based scheduling algorithm for Cognitive Radio Sensor Networks (CRSNs). To avoid inter-clusters collision, we assign fixed channels only to nodes having one-hop neighbors out of their clusters. We denote these nodes as specific nodes. Previous studies assign distinct channels to whole neighbor clusters to avoid inter-clusters collision. Our objective is to optimize the spatial reuse and to increase the network throughput while saving sensors energy. We start by assigning channels only to the specific nodes. Once the problem of inter-clusters collision is solved, each cluster head (CH) schedules the transmissions in its cluster independently. For the cluster members that are specific nodes, the CH assigns only time slots because the channel assignment is already done. For other cluster members (CMs) (not specific nodes), the CH assigns the pair (channel, slot). Two solutions are proposed in this paper to schedule the CMs: The Frame Intra Cluster Multichannel Scheduling algorithm denoted Frame-ICMS and the Slot Intra Cluster Multichannel Scheduling algorithm denoted Slot-ICMS. We evaluate the performance of these algorithms in case of accurate PUs activity detection and in case of bad PUs activity estimation. We prove that our proposals outperform an existing one especially in terms of energy saving

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

International audienceThe unlicensed spectrum bands becomeovercrowded causing an increased level of interference forcurrent wireless sensor nodes. Cognitive Radio Sensor Networks(CRSNs) overcome this problem by allowing sensor nodes toaccess opportunistically the underutilized licensed spectrumbands. The sink assigns the spectrum holes to the secondaryusers (SUs). Therefore, it must rely on reliable information aboutthe spectrum holes to protect the primary users (PUs). In thispaper the sink uses two ways to determine the available channelsand alerts the SUs if an unexpected activity of PU occurs. Ourobjective is to design an algorithm able to detect the unexpectedpresence of PUs in the multi-hop network while maximizingthe throughput. To achieve our goal, we propose an optimizedversion of our previous scheduling algorithm Opportunisticcentralized TIme slot assignment in COgnitive Radio sensornetworks (OTICOR). We then evaluate its performance in termsof number of slots and throughput