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.