Distributed spectrum leasing via vertical cooperation in spectrum sharing networks

In this paper, a hierarchical cognitive radio network is considered, where unlicensed secondary users can maximize the transmission capacity by cooperating with licensed primary users. An asynchronous cognitive radio network and average interference model is assumed. An maximization of the secondary users capacity is proposed by controlling the transmit radio power, the secondary users relaying selection, and power splitting while guaranteeing primary users performance. A method is developed to find the solution to such a challenging mixed integer and non convex problem. The method provides an algorithm for finding the optimal power allocations for secondary users, and a greedy algorithm to finding sub-optimal associations between primary and secondary users. Numerical results evaluate the performance of the proposed method.