Design And Modeling Medium Access Control Protocol For Cognitive Radio Networks

In recent years,with the rapid development of wireless communication technologies and the wide use of wireless devices,the demand of people for spectrum resources is increasing.However,a survey of the US Federal Communication Commission(FCC)shows that a severe imbalance exists in the use of spectrum resources.In the future,the shortage of spectrum resources will become one of the bottlenecks restricting the development of wireless communication technology.Cognitive radio networks(CRN)have emerged as an efficient way to redistribute spectrum resources.The core idea of CRN is that a cognitive system can find a licensed but unused frequency band by sensing the spectrum environment in the frequency domain and the time domain space,in order to share the spectrum resources and improve the utilization of spectrum resource without causing interference to the communication of the licensed users.How to design a reasonable and efficient medium access control(MAC)protocol for the unlicensed and licensed users in CRN,as well as the modeling and analysis of its performance,has always been a difficult problem in related fields.The research work of this paper focuses on the above issues.The main innovative work includes:(1)Depend on the traditional CRN MAC protocol based on common control channel,this paper design a CRN MAC protocol based on the traffic priority classification of licensed users,and analyze the upper bound of the throughput of CRN based on this protocol,which provides theoretical guidance for the setting of protocol parameter.The protocol records the licensed users as the primary user(PU)and the unlicensed users as the secondary users(SU).The protocol can be divided into the competition phase,the channel reservation phase,and the data transmission phase.The competition phase is mainly used by SU to compete for the licensed channel,the channel reservation phase is used for the information interaction between the sender and receiver,and the data transmission phase is used for the transceiver to tune to the licensed channel and start transmission stage.The protocol aims to reduce the waste of the channel bandwidth due to the waiting for the occupied licensed channel to idle by SU and the collisions between the SU and PU through the four-time handshake mechanism and the traffic priority classification mechanism of PU.So as to improve the performance of network saturation throughput and the quality of service as much as possible.Simulation results show the validity of the protocol.(2)Modeling and analyzing the problem of CRN saturation throughput,and proposing a twodimensional Markov chain model.In this model,the "pseudo-state" is used to distinguish the two different collision probabilities of the SU in the common control channel and the data transmission channel.This paper put forward the concept of the virtual backoff process,which successfully corrects the error of collision probability calculation due to the change of SU's number in the common control channel.The model transforms the CRN throughput problem into a successful reservation problem in the common control channel,and converts the multi-channel problem into a single-channel problem to obtain the mathematical expression of the network saturation throughput.The comparison of the numerical and simulation results proves the validity of the model and provides a theoretical basis for the performance improvement and parameter optimization of the protocol.