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Spectrum Sensing Scheduling in Cognitive Radio Networks

Kelkar, Aditya
In cognitive radio (CR) networks, spectrum sensing has gained great importance for opportunistic spectrum access. There are many factors that affect the efficiency of spectrum sensing. High sensing accuracy can help reduce the chance of interference to primary user and improve the spectrum utility. However, high sensing accuracy requires a large amount of sensing resources including multiple collaborative CRs and the sensing duration. We propose a cost based framework for spectrum sensing scheduling, in which all these factors are modeled by certain cost or gain of the system. A sequential energy detector is used for accumulating all energy measurements for sensing. Depending on the decision made, the CRs decide whether to wait as the channel is occupied or to start data transmission as there is a spectral hole. The optimal number of CRs, the sensing accuracy levels and the waiting/transmission time are obtained such that the average gain per unit time including both sensing and wait/data transmission stages are maximized. We provide various experimental results to show the effectiveness of the proposed design and the effects of various parameters on the performance are analyzed. The idea is then extended to a multiple channel CR network. The channel profile generated from a single channel design is utilized for CR assignment to channels that request for sensing. Two approaches, viz., greedy approach and non-greedy approach are designed for scheduling. Then the two approaches are compared on the basis of total average gain obtained from each approaches. The non-greedy approach outperforms the greedy approach with respect to the total average gain.