Study On Dynamic Spectrum Allocation Of Joint Power Control In Cognitive Radio Networks

With the sustained growth of wireless communication services,the confliction of the limited radio spectrum resources and the increased radio spectrum demand hampers the development of wireless communication. Cognitive radio as a new spectrum share technology can opportunistically access and utilize the searched available spectrum by interacting with the environment, so then improve the utilization of spectrum resources and ease the shortage of spectrum resources. Specifically, dynamic spectrum allocation algorithm produces an effect on utilization of wireless spectrum, also play a crucial role to the performance of cognitive radio networks.This paper focuses on dynamic spectrum allocation algorithms in Cognitive Radio Networks. During the allocation, several cognitive users can simultaneously utilize the same channel which will inevitably lead to interference between users, the power control mechanism can be introduced to avoid this problem. Reasonable power control mechanism can not only acquire balance between enlarging communication area and reducing communication interference, but also cut down energy expenditure of terminals.The paper designs joint power control in dynamic spectrum allocation to reduce interference between users, thereby improve spectrum efficiency. The main contents include:1) Firstly, the background and basis concept of cognitive radio was introduced, then dynamic spectrum allocation algorithms and power control technology were expounded, especially the important role of power control mechanism during spectrum allocation was analyzed, finally existing allocation models specially the graph based model were illustrated.2) In order to fit characters of cognitive radio, based on graph theory, the interference graph model when several cognitive users simultaneously utilize the same channel was studied, further more, characters and performance of some spectrum allocation algorithms were compared and analyzed.3) For the sake of high system performance, fast convergence performance and well fairness, under stochastic distributed network environment, an improved dynamic spectrum allocation algorithm of joint power control mechanism was proposed. Joint power control mechanism can avoid interference between users that access the same channel, this in turn, meet more users'transmission requirements. At the same time, allocation begins with the maximal independent set (MIS) that allows assigning a particular channel simultaneously to a set of links with no interference between each other which can cut back the number of allocation and reduce information exchange among users so that it can enable fast convergence. In the end, the influence of user require and history information were analyzed, and an dynamic spectrum allocation algorithm based on demand and historical information was presented, by introducing user priority and channel priority to meet fairness ulteriorly. Simulation results show that the performance of dynamic spectrum allocation algorithm of joint power control is much better than that of dynamic spectrum allocation algorithm without power control, simultaneously confirm the validity of the improved algorithm in system performance, fairness and convergence performance.