Research On Spectrum Handoff Based On Queuing Theory In Cognitive Radio Networks

Cognitive radio technology can utilize spectrum holes opportunistically to improve spectrum efficiency.When the primary user reaches the authorized frequency,the secondary user has to remove from the current frequency unconditionally in order to ensure the service quality of the primary user.However,with the development of network technology,the explosive growth of mobile services has led to a sharp increase in user traffic,resulting in the shortage of spectrum resources.On the one hand,the surge in the primary users traffic causes the secondary users to perform the spectrum handoff frequently.On the other hand,the secondary users have higher and higher requirements for delay performance,and secondary users with different services have different delay performance requirements.Therefore,it is necessary to design the reasonable and efficient spectrum handoff strategy to improve the delay performance of the secondary users.In order to improve the delay performance of secondary users in cognitive wireless networks,the main contents are as follows:1.In order to provide more spectrum resources,a cognitive heterogeneous radio network is proposed by combining open wireless networks that utilize unlicensed spectrum with cognitive radio networks using authorized spectrum opportunistically.Aiming at the problem of large service delay caused by the increasing of user traffic,a dynamic adaptive spectrum handoff strategy is proposed based on data segmentation factor optimization.Firstly,the secondary users are classified according to the service delay requirement.Secondly,a data segmentation factor optimization strategy based on the heterogeneous network historical channel information is proposed according to the busy state of the primary user network,to optimize the delay performance of the secondary users.Finally,the preemptive and non-preemptive M/G/1 queuing model is used to model the spectrum handoff process,and analyze the extended data transmission delay.MATLAB simulation results show that,the proposed spectrum handoff strategy shows better delay performance than the always-staying mode and the always-changing mode.2.A heterogeneous spectrum handoff strategy based on M/M/c retry queuing model is proposed to solve the problem of the system performance degradation caused by multiple spectrum handoff in the cognitive heterogeneous radio network.Firstly,the spectrum handoff strategy of primary users and different priority secondary users is designed according to the different delay requirements of the secondary users.Secondly,the M/M/c retry queuing model is used to model the spectrum handoff process of the secondary users,and then we analyze the extended data transmission delay of secondary users combining markov chains.Finally,we use MATLAB to simulate the heterogeneous spectrum handoff strategy proposed in this thesis,and the results prove that the heterogeneous spectrum handoff strategy can further reduce the handoff delay of secondary users.