Efficient cooperative spectrum sensing for cognitive wireless relay networks over Rayleigh flat fading channels

This paper is concerned with cooperative spectrum sensing (CSS) mechanisms in cognitive wireless relay networks (CWRNs). Conventionally, the decision of available spectrum for cognitive radio (CR) users is carried out based on the global decision at a fusion center (FC). In this paper, we propose a new CSS scheme to improve the spectrum sensing performance by exploiting both local decisions at the CR users and global decisions at the FC. Particularly, by deriving the probabilities of missed detection and false alarm for a practical scenario where all sensing, reporting, and backward channels suffer from Rayleigh fading, we show that our proposed CSS scheme achieves an improved sensing performance over the conventional scheme. Furthermore, we propose a CSS scheme based on network coding (NC) for a specific CWRN where the transmission from a source node to a destination node is realized with the aid of two groups of CR users located in the transmission coverage of two primary users (PUs). The proposed NC-based CSS scheme helps reduce one phase of sensing for a higher system throughput compared to the conventional scheme which requires eight phases in total to monitor all available spectrums of both PUs.