Joint optimization of power and decoding order in CDMA based cognitive radio systems with successive interference cancellation

In the cognitive radio (CR) system, power control is a key enabling technique to ensure quality-of-service (QoS) provisioning for primary users (PUs) and secondary users (SUs). How to efficiently allocate power to SUs is not a trivial work, especially, in CDMA based CR systems with successive interference cancellation (SIC), the number of possible decoding orders grows factorially with the number of users, the problem of power control is a combinatorial optimization and belongs to the category of NP problems, which involves the joint optimization of power allocation and decoding order adjustment, thus the complexity efficient optimal algorithm cannot be found and the suboptimal algorithm should be developed. This paper proposes an efficient joint optimization algorithm of power allocation and decoding order adjustment for addressing this NP problem. In the proposed algorithm, the feasibility of CDMA based CR systems with SIC can be quickly examined. Furthermore, if the CR system is feasible, the power and decoding order of SUs will be efficiently optimized based on the corresponding feasible decoding order. We conduct the extensive simulation experiments, and the numerical results demonstrate the effectiveness of our algorithm.