Research On The Intersection Sequence And Competition Resolution Strategy For Cognitive Radio Networks

In cognitive radio networks,channel rendezvous strategies and collision avoidance mechanisms allow multiple secondary users(SUs)to access the licensed spectrum and enable one of them to gain access to the spectrum for data communication.Hence the utilization of spectrum resources can be improved and the problem of spectrum resource shortage can be alleviated.Due to the lack of global clock synchronization and the lack of global channel access mechanism in cognitive radio networks,this thesis investigates sequences-based synchronous rendezvous algorithm and collision avoidance mechanism.The main work includes the following four aspects.First,considering asynchronous channel rendezvous of multi-user in cognitive radio networks,this thesis proposes a design of CSI(Complete-ly Shift-Invariant)sequences,proves its completely global SI(Shift-Invariant)property,and derives closed-form expressions of the rendezvous rate and the rendezvous rate variance.The simulation results show that the CSI sequences enjoy optimal rendezvous performance.Second,to handle with channel collisions among multiple SUs,this thesis designs multiselection mechanisms without immediate feedback.The behavior of the mechanism is modeled using the three-dimensional Markov process and the closed expressions of competition successful rate are derived.The simulation results verify the accuracy of the theoretical analysis.Third,to handle with channel collisions among multiple SUs,this thesis proposes a design method of multi-contention mechanisms based on instantaneous feedback.The behavior of the mechanism is modeled by a three-dimensional Markov process,and the closed expressions of contention successful rate are derived.The simulation results verify the accuracy of the theoretical analysis,and also show that the use of instant feedback can effectively improve the contention successful rate at the cost of a large control overhead.Finally,built on the above design,the closed expressions of successful rendezvous rate,successful rendezvous rate variance under different collision avoidance mechanisms are derived.The accuracy of the theoretical analysis is verified by simulation.Furthermore,it is shown that the combined use of the above designs can effectively improve the successful rendezvous rate and reduce the successful rendezvous rate variance,compared with previous studies.