Research About Power Control Algorithm In The Cognitive Radio Network

In recent years,with the continuous growth of the application and demand of wireless networks,the limited spectrum resources become more and more intense,but the spectrum utilization is not high.Cognitive radio technology arises at the historic moment,it can be perceived the idle spectrum in the surrounding wireless environment,and using the technology of dynamic spectrum allocation to realize the primary users and cognitive users of spectrum sharing,and greatly improve the spectrum utilization rate.However,in cognitive system,the cognitive user may increase the transmit power to achieve the ideal transmission quality.So in order to ensure the normal use of the primary user,we must control the power of cognitive users.In recent years,the power control algorithm based on game theory is one of the hot spots,and has achieved good results.The basic idea of game theory can effectively solve the problem of mutual restriction.However,the power control algorithm based on game theory still has problems,such as,far and near unfairness.This paper according to the near far effect exists in the cognitive radio network communication process,path loss over and algorithm stability,analysis and research based on game theory power control algorithm.The main work of this paper is as follows:(1)Firstly,on the basis of NPGP,we proposed a new cost function mechanism-adding a link function of nonlinear cost function.This cost function joined the link factor-penalty factor,which is multiplied with the transmit power,so that reduces the CUs' transmission power,and make the distance from the base station is far from the punishment of CUs smaller,more than the base station near the CUs to be a greater punishment,thus,better control of the near and far unfair effect.(2)Secondly,for the problem of near-far effect,large path loss,and stability of algorithm,e t,in the cognitive radio,a new power control algorithm--a non cooperative power control game algorithm based on the comprehensive cost function,is proposed in this paper.This algorithm design a new utility function,which add some punishment factors,such as,link quality and the interference capacity limit of the primary users(PUs)are considered.In order to realize the adaptive adjustment of penalty factors,the Signal-to-interference radio(SINR)of CUs are controlled above the minimum threshold and the interference value of the CUs arecontrolled below the capacity tolerance of PUs in this algorithm.So,in this algorithm,the CUs' SINR are poorer,the less punished the CUs are,in the extent to reduce the overall transmit power of cognitive users,and ensure the normal communication of primary users and cognitive users.The existence of Nash equilibrium is given.The simulation results show that the new algorithm has batter stability,and with smaller transmission power,could reduce the loss of the path,solve the near-far effect problem effectively,and make the interference of CUs less than capacity tolerance of PUs.