The Research Of Power Control Algorithm And The Application Of Correlative Optimization Algorithm In Cognitive Radio Networks

Cognitive Radio Network (CRN) is a key technique in next generation wireless communications to relieve the spectrum scarcity problem. The core idea of CRN is to make users with the ability of sensing the information of its radio environment access the unused spectrum in an opportunistic manner, which will greatly improve the wireless spectrum efficiency. Also, CRN can significantly increase the system performance such as total throughput.Power control technique, one of the most important issues in CRNs, is to manipulate the transmission power levels of cognitive users or secondary users (SUs) in order to satisfy their own communication requirements as well as to make little interference to licensed users or primary users (PUs). Recently, as a powerful tool of allocating resource, game theory is widely used in areas like wireless communication, power control and so on. In CRNs, the mostly used non‐cooperative game theory power control models treat transmission power levels of SUs as players, and then each player will contend with each other trying to maximize its utility according to a utility function. In this paper, we propose a power control model of uplinks in CRNs based on non‐cooperative game theory, suggest a novel utility function and prove the existence of Nash Equilibrium of this model. Then, a power control iterative algorithm is deduced from this utility function and we also prove its convergence. Simulation results show that this algorithm can not only satisfy the Signal to Interference plus Noise Ratio requirements, but also make SUs have proper transmission power levels. Also, the algorithm suggested in this paper has a better anti‐noise effect compared with other algorithms.Just like game theory, assignment problem is another branch of operations research. The feature of assignment problem is similar with the process of choosing proper relay nodes in cooperative communication; both of them are assigning proper resource to proper location to maximize the system performance. Thus, it is nature to consider using theories about assignment problem to decide how to choose relay nodes in cooperative communication. Cooperative communication takes advantage of the transmit diversity and can bring great improvements to the system performance. However, problems such as low frequency spectrum utilization and low total throughput do exist in recent researches of cooperative communication. In this paper, we propose a new cooperative communication algorithm to conquer the above disadvantages. Based on the consideration of making full use of all available channels, we put forward a total throughput maximization problem in CRNs. Through mathematical analysis and reduction, we turn this maximization problem into a standard assignment problem and use Hungarian method to solve it. We also deduce an algorithm to help PUs and SUs in CRNs to decide their proper choose of communication methods. Performance evaluations via simulations show that our algorithm can greatly improve the total throughput and frequency utilization rate of CRNs compared with other methods.