Optimal Power Control with QoS Constraint for OFDM-Based Cognitive Radio Network

The power control problem is considered with the CR user QoS requirement and the interference to primary user under the threshold which the primary user can tolerate. We model the power control as a optimize problem which each CR user SINR must not less than minimum SINR requirement and the total interference must less than predefined threshold. Firstly we consider the network can satisfy the CR user SINR requirement, then we use the lagrange multiplier to solve the power allocation optimize model. Then we consider the condition that the network can´t satisfy the CR users SINR requirement, so we would be to check the feasibility condition and conduct optimization to find the optimal feasible link set and the optimal power allocation. We prove that find the optimal power allocation is NP-complete. Lastly we use heuristic algorithms to realize the optimal power allocation in the network and give the detailed conduct of the algorithm.