Spectrum Sharing Strategy And Optimal Cognitive Transmission In Cognitive Radio Networks Based On ARQ Feedback

With the large-scale deployment and application of wireless networks,the demand for spectrum resources has become stronger,but the total amount of spectrum resources is limited,which has caused the contradiction between spectrum supply and demand,and the problem of spectrum scarcity has become increasingly obvious.Studies have shown that cognitive radio networks are one of the powerful ways to solve the problem of spectrum scarcity.Cognitive radio networks can enable secondary users to use idle spectrum resources without interfering with the normal traffic of authorized users,thereby improving spectrum utilization.This article analyzes and studies the spectrum sharing mechanism in cognitive radio networks,and also analyzes the optimal transmission of secondary users under cognitive radio networks.The specific work content is as follows:Firstly,this paper proposes a spectrum sharing strategy under the cognitive radio network.In this strategy,the secondary user(SU)can use ARQ(Automatic Repeat Request)to improve the performance of cognitive radio network.In the cooperative mode,the secondary user can assist the primary user(PU)transmission,and the redundant transmission of primary and secondary users is reduced.The Markov chain of primary and secondary users' transmission state is established,and the system throughput expression in steady state is derived.In the access mode,when the primary user feedback a NACK(negative acknowledgement),the primary user needs to retransmit,so that the primary and secondary users can simultaneously transmit during the retransmission period,which provides the secondary users with spectrum access opportunities,and analyzes the throughput gain under the access mode.Matlab is used to compare and verify the system throughput performance.It can be concluded that the system has higher throughput under the sharing strategy.Secondly,the optimal transmission situation for secondary users is considered in this article.Suppose the primary user implements the retransmission technology based on error control.This makes the interference transmitted by the main user to the secondary user generate inherent redundancy.It can be used to study the transmission strategy of the secondary user.The basic idea is that if the secondary user can obtain the main information in the given master retransmission process,then he can use the information to eliminate the interference from the main user in the next slot,thus achieving a relatively large secondary throughput.This will involve a balance problem in the design of secondary transmission strategy.On the one hand,secondary transmission will increase secondary throughput,but on the other hand,it will also cause interference when the main receiver and secondary receiver receive the main user information.These interferences may cause the retransmission of the same master user information,which is beneficial to the transmission of secondary users,but it makes it more difficult to decode primary message(PM)at SR,reducing the available redundancy under given interference constraints at pr.It is proved that the secondary user can transmit first when the SR has known primary message,because the latter can perform interference cancellation and obtain greater secondary throughput.In addition,when the ink constraints are loose,secondary transmission can also be transmitted when SR does not understand primary message.The structure of the optimal strategy is given.The numerical results show the throughput efficiency of the strategy.