Performance of Cooperative Sensing at the MAC Level: Error Minimization Through Differential Sensing

Efficient operation of cognitive personal area networks (CPANs) necessitates accurate and efficient sensing of the primary user activity. This is accomplished in a cooperative manner by a number of nodes in the CPAN; the results of sensing are combined by the CPAN coordinator to form a comprehensive and timely channel map. The error of the sensing process is affected by various factors, including the ratio of the number of sensing nodes to the number of channels. In this paper, we present a probabilistic model of the sensing process and derive an analytical solution for the minimum number of sensing nodes that keeps the sensing error below prescribed limits. Then, we discuss three differential sensing policies in which separate sets of sensing nodes target idle and active channels only and show that the policy in which idle channels are given priority, but not exclusive treatment, achieves the best performance, as measured by the number of channels for which the information in the channel map is erroneous and the mean duration of that erroneous information.