Research On The Performance Of Spectrum Switching Mechanism In Cognitive Radio

With the rapid development of wireless network,people have higher and higher requirements for spectrum bandwidth.Compared with the availability of bandwidth,the number of devices using spectrum grows very fast.As the current spectrum allocation mechanism is static,it can not meet the increasing bandwidth demand,and the problem of spectrum scarcity is increasingly prominent.Cognitive radio network(CRNs)is an effective way to solve this problem.Cognitive radio network enables secondary users to temporarily use the spectrum bandwidth not occupied by the primary user,so as to improve the utilization of limited spectrum resources.In this paper,the spectrum switching mechanism in cognitive radio network is analyzed and studied.The specific work is as follows:Firstly,this paper studies the preemptive priority queuing model based on the mechanism of continuous transmission,which is used to evaluate the impact of multiple spectrum switching on channel utilization and delay performance in cognitive radio networks.According to the characteristics of cognitive radio network,the priority relationship between primary user and secondary user is described by using the preemptive priority queuing model,and the corresponding service queue is established.The secondary connection may be interrupted by multiple interrupts from the primary user during data transmission,which may result in multiple spectrum switching.Although spectrum switching can improve the channel utilization,the transmission delay will increase due to multiple switching.In the model proposed in this paper,the mixed queuing parallel service queuing method is used.Based on this,the spectrum switching behavior of the secondary user is analyzed,and the generalized transmission time and channel utilization of the secondary user are derived,and the influence of the arrival rate of the primary and secondary user on the channel utilization and the generalized data transmission time is analyzed.Secondly,this paper proposes a new primary user first adaptive spectrum handoff mechanism based on the traditional handoff mechanism.It emphasizes the priority of the primary user,and considers the influence of the primary user's arrival rate on the secondary user's communication and limits the interference power of the secondary user to the primary user,so as to adaptively decide to implement the active handover mechanism or the passive handover mechanism.The Markov chain between primary and secondary users is established under this adaptive switching mechanism,and the corresponding steady-state probability is obtained.The analytic expressions of system throughput and channel utilization are derived from the steady-state probability and throughput under different states.In addition,a Markov chain is established for the communication between secondary users,and the time of transmitting control information between secondary users is deduced.Numerical results show that the proposed adaptive handoff mechanism has higher system throughput and channel utilization than the CSMA based access method,and can calculate the transfer time between secondary users.