Multi-user Opportunistic Spectrum Access with Channel Impairments

In this paper, we study the impact of sensing error and channel fading on the decision process of a multiple secondary user network in a primary network whose channel occupancy states are modelled as a Bernoulli process. We present a randomized access strategy to maximize total secondary network throughput. The proposed method guarantees that the probability of collision between primary and secondary users in each channel is less than the predefined value of P_c = ξ. To find the optimal access strategy, we formulate secondary network throughput as an optimization problem. Then, using the KKT method to find the solution, we break the original problem into multiple sub-problems. Then, we employ an iterative algorithm and a sifting technique to reduce the number of sub-problems and find the final solution. The solution contains both the SUs access strategies and their detector operating points. In other words, we present a solution for the cross layer design in cognitive radio networks. At the end, we compare our results with two other heuristic strategies (1) equi-probable strategy and (2) weighted strategy and show that the proposed method outperforms them in terms of total throughput.