On Distributed Multi-User Handshake And Access Protocol In Cognitive Radio Networks

With the continuous development of communication technologies and the rapid increase in the number of wireless intelligent terminals,the shortage of spectrum resources has become a bottleneck for the development of modern communications,and the drawbacks of traditional static spectrum allocation methods have also become increasingly evident.The terminals in the cognitive wireless network can learn the electromagnetic environment intelligently,adjust their configuration parameters autonomously according to the sensing results,and dynamically use spectrum holes to fundamentally solve the shortage of spectrum resources.Therefore,cognitive radio technologies have gradually become one of research hotspots.In order to solve the collision problem of multiple pairs of cognitive users trying to access the same channel in a distributed cognitive wireless network,this thesis will focus on the discussion of distributed multi-user multi-channel handshake and access protocols.Improve the collision between cognitive users,and then improve the utilization of spectrum resources in the system and improve the shortage of spectrum resources.This thesis first introduces the classification criteria and characteristics of distributed multi-user multi-channel handshake and access protocols.Then we study the existing handshake and access protocol called Multi-step Channel Reservation based Multi-channel MAC(MCR-MMAC).Based on this,we propose an improved handshake and access protocol.The cognitive users select the common control channel dynamically according to the real-time channel state before handshaking,which effectively solves the system congestion problem.Adopting the idea of polling time division in the handshake,effectively improves the collision problem of cognitive users in the handshake phase,and solve the common control channel saturation problem.So,we improv the system spectrum resource utilization.Then,in the multi-hop cognitive wireless network,we use the method of the maximum number of side bipartite graphs to cluster the cognitive users in the network.Based on this,we propose a handshake and access protocol based on selecting channels by channel weight.In the protocol,we improve the collision problem on the global common control channel by selecting the local common control channel.The channel weight is used to select the channel to handle the collision problem on the data channels,we divide channels into two sets,the inner-cluster communication channel set and the inter-cluster communication channel set,which accelerates the convergence rate of selecting channels by channel weigh,increase the cumulative access time of cognitive users,and increase the utilization of system spectrum resources.