Research On Spectrum Sharing Algorithm For Railway Cognitive Radio Networks

The rapid development of modern economic society has stimulated the increasing renewal of China's high-speed railway construction.Convenient and safe trains are the preferred means of transportation for people's daily travel.With the vigorous development of modern diversified network products and the intelligentization of handheld terminals,people use wireless spectrum more frequently.Trains are densely staffed,and so many spectrum requirements make the carrying capacity of radio spectrum resources even more inadequate.The secondary user(SU)in the cognitive radio system can attract authorized users to participate in spectrum resource trading actively by compensating for considerable economic income so as to access their idle spectrum opportunely within the acceptable interference range of primary user(PU).Game theory is the optimal decision-making theory under the interaction of competitive individual strategies.In recent years,its application in spectrum sharing of cognitive radio system has become a research hot spot.However,most previous studies are based on specific theoretical models,and few studies focus on specific scenario;and the services transmitted by the secondary users are treated equally,which is quite different from the actual spectrum sharing scenarios.In view of the shortcomings of the above research,this paper analyzes and designs the cognitive spectrum sharing algorithm based on train user's service in the high-speed railway scenario.Through the simulation analysis,the rationality and effectiveness of the algorithm are demonstrated.(1)The traditional one-sided network coverage mode is prone to signal transmission interruption when the train is switching over the area.Aiming at this problem,this paper realizes the spectrum sharing process from the base station to every train user based on the HSRs interlaced site redundancy coverage model,which divides the process into two steps:from the base station to the train body,from the train body to single train user;and selects appropriate game theory models at different stages to analyze specific spectrum sharing problems.(2)During the spectrum sharing process from the target base station to the train body,different target base stations compete with each other to obtain relatively more spectrum sharing opportunities,thus greatly improving their economic benefits.Therefore,the classical Bertrand game model is used to analyze the effect of the current network load status,the difference of spectrum attributes among different authorized user agents(such as spectrum occupancy ratio,data transmission efficiency and spectrum substitution)on the actual spectrum sharing results.Under the condition that the train is stationary and the primary system(authorized user agents)fully grasps the opponent's strategy information,the optimalstrategy and benefit income of the network providing spectrum service are analyzed;and the optimal response strategy and benefit of the main system in the process of train movement are given.In addition,under the dynamic bidding model,a new distributed iterative algorithm is adopted,which makes the spectrum strategy of the main system converge to a lower price rapidly.While ensuring the efficiency of the primary system,it greatly improves the enthusiasm of the cognitive train participating in spectrum sharing.(3)The spectrum allocation strategy from the train body to individual user needs to satisfy the expects of different service transmission of secondary users.In this stage,under the condition that the train body owns limited spectrum,the target transmission rate value of different services is introduced in a dynamic game algorithm,so that train users carrying different services can use spectrum resources with restraint,according to the proportion of target demand;The pricing principle enables users with poor service satisfaction to obtain relatively favorable prices,which balances the satisfaction of transmission revenue among train users,and achieves relatively fair spectrum sharing of different business.