Cooperative Spectrum Sensing with Double Adaptive Energy Thresholds and Relaying Users in Cognitive Radio

Cognitive radio (CR) technology has been proposed to improve spectrum utilization by allowing cognitive radio users to opportunistically access under-utilized frequency band. The requirement of cognitive radio system is reliable detecting signals from licensed users to avoid harmful interference. However, due to the effects of the channel fading and shadowing, individual cognitive radio may not able to reliably detect the presence of a licensed user. In this paper, we propose a cooperative spectrum sensing scheme with double adaptive threshold and relaying users in order to improve sensing performance of both local sensing performance and global sensing performance in a CR network. In the proposed scheme, the detection threshold is changeable to adapt with the fluctuation of the received signal power in each local detector of cognitive user. In addition, the CR users with higher reliability act as a relaying user for the object of helping their neighbors to improve sensing performance. Finally, all the local observations will be sent to the fusion center to determine the global decision by using the Likelihood rule without any requirement on priori information of the licensed user.