Collaborative channel search in cognitive radio networks

We consider a scenario where multiple collaborating cognitive radios (CR's) try to jointly detect spectrum opportunities in a wide-band spectrum within a predefined spectrum sensing time T S . Each CR is equipped with a tunable bandpass filter (BPF) and is able to sense one frequency band (channel) at a time. The sensing time consists of L sensing slots of length T. During each sensing slot, each of the collaborating CR's is assigned to sense one of the primary channels and report its observation to the other CR's. The goal is to maximize the expected number of identified idle channels by optimally choosing the channels to be sensed by each of the collaborating CR's at each sensing slot. We derive closed-form solutions for an optimal spectrum sensing policy and the associated reward function for the case of two collaborating CR's where individual sensing decisions are fused together according to the OR-rule. We show that the gain due to the optimal sensing policy is more significant when the spectrum utilization is high.