Research Of Spectrum Access Scheme Based On The Priority Of Secondary Users

Cognitive radio network is one of the methods to solve the contradiction between supply and demand of the spectrum.With the age of the Internet coming,Personalized and multimedia demand of the secondary users become the main features of the next generation wireless networks.So how to divide the spectrum resource with different priority secondary users in coexistence environment is the important problem.Carrier Sense Multiple Access scheme is one of the important technology in IEEE 802.11,it has a wide range of applications in WLAN.On this basis we designed spectrum allocation scheme in different priority secondary users in coexistence environment and analyzed the performance of the system.Firstly,aiming at the characteristic of different demand of users coexist in the cognitive wireless network nowadays.This dissertation designed a plan that combine with different detect mechanism and back-off mechanism.Then it makes high priority secondary users detect channel with full listening scheme and get shorter back-off time.With this scheme reflect to different demand between high priority secondary users and low priority secondary users.Secondly,build the Markov Model of this scheme with queuing theory,and obtain the steady state probability with matrix analytical method,on this basis,two important performance measures were obtained,forced termination probability and throughput of secondary users.Then discuss the performance of the proposed scheme under the system parameters.At last,design optimization algorithm for getting optimal value of different priority secondary users in coexistence environment scheme when system throughput reach the maximum.This algorithm could obtain optimal value of high priority back off time to make throughput of system to the top.Result of the experimental shows that the scheme put forward by this paper could adapt to the different priority secondary users in coexistence environment,and satisfies the demand of high priority secondary users.On the basis of the algorithm for getting maximum value of this scheme we could allocate wireless spectrum resources better than before,which raised performance of different priority secondary users in coexistence environment.