User Assignment and Power Allocation Optimization in Cognitive Radio Networks

The paper considers an underlay cognitive radio model, which includes multiple primary and secondary users. Under the interference limitations imposed for the conservation of a high quality of service (QOS) for the primary users, this work aims to enhance the throughput of the secondary users. A joint optimization of secondary to primary user assignment and the power allocation at the secondary user's transmitters is adopted under the interference as well as individual power constraints. To solve the formulated integer programming problem, dual decomposition strategy is adopted. Karush -- Kuhn -- Tucker (KKT) optimality conditions are exploited to obtain the optimal power allocation while user pairing is obtained from the assignment problem. Moreover, sub-optimal schemes are proposed to reduce the complexity and finally simulations are conducted to validate the proposed schemes.