Optimal M-Out-of-S Rule for Asynchronous Cooperative Sensing in Heterogeneous Cognitive Radio Networks

Abstract

This letter introduces an asynchronous cooperative sensing (CS) scheme in a heterogeneous cognitive radio network (CRN), wherein S secondary users (SUs) characterized by non-identical receiver operating characteristic (ROC) curves report their sensing results to the decision fusion center (DFC) with different reporting delays. The DFC adopts the M-out-of-S rule to identify the primary user’s (PU’s) signal under dynamic scenarios, where the PU switches between active and inactive states during the CS interval. First, we derive the generalized expressions for the ROC curve of the proposed scheme. Then, we formulate a generalized optimization problem to determine the optimal value of M of the M-out-of-S rule under the Bayesian criterion. Additionally, we present a limiting value on individual SUs’ reporting delays to achieve the best CS performance. Finally, the numerical results obtained using an energy detector (ED) demonstrate the superior performance of the proposed scheme over the state-of-the-art schemes.