Adaptive sequential cooperative spectrum sensing technique in time varying channel

Cognitive radio is proposed to opportunistically access the spectrum while the licensed user is idle. As a result, spectrum sensing procedure to observe primary user´s existence is vital to cognitive radio. In this paper, we propose two adaptive sequential cooperative spectrum sensing techniques in time varying channel, namely the Two Stage Sequential Energy Detector and Differential Sequential Energy Detector. By utilizing past local observations from previous sensing slots, cognitive radio nodes can aggregate the current and previously received energy values to improve the detection performance. We explore the adaptive schemes, where cognitive radio user takes in previously received energy values when it thinks that the primary user´s activity remains unchanged. Simulation results show that both proposed schemes provide better detection over conventional energy detection based cooperative technique. Additionally, both proposed schemes can satisfy the IEEE 802.22 standard´s requirement of 10% false alarm and 90% detection in scenario that conventional techniques can not accommodate.