Optimal resource allocation in multi-relay cognitive networks using dual decomposition

In this paper, an OFDM-based multi-relay cognitive radio network is considered where the relays use the decode-and-forward protocol to assist the source to relay transmission. The objective is to maximize the capacity of the CR network by optimizing the relay selection, subcarrier pairing and the power allocation. The optimization is performed under the interference to primary constraints as well as the individual power constraints. The problem is formulated as a mixed integer programming problem and the joint optimal solution is found using the dual decomposition technique. To reduce the computational complexity of the optimal scheme, a suboptimal algorithm is presented. Simulation results reveal that the suboptimal algorithm achieves a near optimal solution with less complexity.