Joint channel assignment and power allocation in cognitive radio networks

A joint channel assignment and power allocation algorithm is presented for cognitive wireless networks, where primary and secondary users operate over the same frequency band at the same time. In this study, we take into consideration a constraint on the interference from secondary users towards primary users, as well as a constraint on the QoS of secondary users. The problem is formulated as a constrained utility maximization problem, for which we prove the existence and the uniqueness of the global optimum solution. Since the problem is NP-hard, we provide a novel heuristic algorithm that operates in two phases. Firstly, it admits all the incoming secondary users and allocates the available channels through a distributed and dynamic procedure, taking into account the interference constraint. Secondly, an iterative power control, which considers both constraints, is applied. In each iteration, a user removal algorithm is employed to reduce the number of admitted secondary users until a steady state is reached. The performance of the joint resource allocation algorithm is investigated in terms of the total number of admitted secondary users for several network parameters, such as the minimum QoS requirements and the interference constraint.