Research On Spectrum Access Scheme Based On User's Priority Under Heterogeneous Networks Environment

With the continuous development of wireless communication technologies and mobile broadband networks,the coexistence and integration of heterogeneous networks and the demand for personalized services of different users have become one of the important features of the next generation wireless communication network.How to allocate rare spectrum resource effectively under the heterogeneous networks environnent has important research value and practical significance.Cognitive radio technology has been widely used in the field of wireless spectrum access domain to improve the utilization of spectrum resources by enabling secondary users to access the idle spectrum unused by primary users opportunistically.In this thesis,cognitive radio technology combined with carrier sensing multiple access scheme are applied to heterogeneous networks and a new spectrum access scheme based on user's priority is proposed.Firstly,according to the characteristic of the coexistence of users with different personalized needs,these users were distinguished by adopting different spectrum access mechanisms.In this scheme,low priority users can only sense channels in one single network,while high priority users use all sensing mechanism to sense all channels of system and use new switching mechanism to execute spectrum handoff in order to obtain more access opportunities.By using different sensing and switching mechanisms,different business needs of high and low priority users can be satisfied.Secondly,adopting the analysis method of queuing theory,a four-dimensional continuous-time Markov model of the proposed scheme was constructed.By using matrix analysis method,the steady state probability of system and two important system performance measures,system throughput and HoL packet delay,were obtained.Then analyzed the impact of different system parameters on the performance of the proposed scheme.Lastly,an optimization algorithm of the back-off rate of high priority users with the highest system throughput of the proposed scheme was designed.The algorithm can adjust the optimal back-off rate of high priority users under different networks environment and obtain the maximum system throughput.The simulation results showed that the proposed spectrum access scheme based on user's priority under heterogeneous networks has better performance than the existing spectrum access scheme without the priority classification of users under heterogeneous networks.The allocation of spectrum resource according to the optimization algorithm designed in this paper can improve the throughput of system.