Research On Multicast And Broadcast Schemes In Mobile Ad Hoc Networks

Thanks to the rapid development of mobile technology,the mobile devices are in widespread application by which our lifestyles and society are being changed.The ubiquitous computing technology has developed rapidly,and now,humanity is being in the period of the transition from a personal computer-based Internet era to the Internet of things(IOT)era.In the IOT era,the communication devices are apt to be interconnected efficiently in wireless way.There are various wireless devices used to access information anytime,anywhere as needed.MANETs(Mobile Ad Hoc NETworks)requires no fixed infrastructure and could be easily deployed in any place at any time.It runs in a distributed and parallel way,which makes the network highly robust and strongly fault tolerant.All make MANETs the preferred networking solution for mobile wireless devices.Multicast and broadcast schemes are two very import components in MANETs for its Grouporiented applications.Moreover,Broadcasting is used by many routing protocols in their route discovery processes.Although many kinds of multicast and broadcast schemes have been proposed,less in-depth works focus on the node mobility and there still has a large room to improve their overhead,delay,and reliability.MANETs is increasingly applied in civil fields besides being applied in the military action and the emergency rescue scenarios.The applications of smart car,mobile phones,smart watches and other wearable devices are experiencing rapid growth.VANET and wearable ad hoc networks,etc.,have become a hot research topic in the near future for its huge market potential.The satellite constellation network is also being in development.The nodes in these new applications have strong mobility and their mobile speeds are quite different.Consequently,further improving the adaptability to node mobile of multicast schemes and broadcast schemes in MANETs is an important subject with significant theoretical value and practical significance.The systematic and in-depth work on the adaptability to node mobility of multicast and broadcast schemes for MANETs has been carried out in this thesis.The corresponding multicast and broadcast schemes for low-medium-speed and the broadcast scheme for medium-highspeed scenarios are proposed as the solutions adapting to different node mobility and density,different ratio and absolute number of uncovered neighbors.The major works are stated as follows.(1)Aiming at the matter of different velocities of nodes,a velocity-based data dissemination scheme(VDDS)is proposed for MANETs.In the scheme,a small part of high-speed nodes is hired to forward the received packet with higher probability.The forwarding probability at each node is adjusted dynamically and adaptively according to its velocity.The velocity-based data dissemination mechanism accelerates the data propagation efficiently,and reduces the delay at a low cost.Moreover,it can be extended easily to other data dissemination schemes,which need to collect the neighbor knowledge,to upgrade their performance.(2)Aiming at the problem of multicast performance affected by mobility,uneven distribution and different velocities of nodes,NCM(a Neighbor Coverage-based Multicast scheme)and NCVM(a Neighbor Coverage and Velocity-based Multicast scheme)are proposed working in low-medium-speed scenario in MANETs.In NCM scheme,the forwarding probability of multicast packet at each node is calculated according to the ratio and the absolute number of uncovered neighbor group member,and the density of neighbor as well.The neighbor coverage condition is a true reflection of data dissemination and is maintainable.Before the forwarding,each node need to wait a random delay time to update the neighbor coverage knowledge,which decreases the probability to disseminate redundant data and keeps the network load balance.The simulation proved that NCM keeps a high packet delivery ratio with less overhead and reduces the average end-to-end delay sharply.By extending VDDS to NCB scheme,NCVM is proposed.In NCVM,a part of high-speed nodes is hired to forwarding the multicast packets,which is different from NCM.Moreover,it further reduces the average end-to-end delay and improves the packet delivery ratio.(3)Aiming at the problem of broadcast performance affected by mobility,uneven distribution and different velocities of nodes,NCB(a Neighbor Coverage-based Broadcast scheme)is proposed working in low-medium-speed scenario in MANETs.And,by extending VDDS to NCB scheme,a promoted scheme NCVB(A Neighbor Coverage and Velocity-based Broadcast Scheme)is obtained.NCVB upgrades its adaptability to node mobility and reduces the average end-to-end delay.(4)In medium-high-speed scenarios,the tree-based,the mesh-based and the coverage-based schemes only obtain a poor performance,due to topological reconstruction and inaccurate coverage knowledge caused by frequent node movement.However,the neighbor density knowledge is insensitive to node mobility,so NDB(a Neighbor Density-based Broadcast scheme)in this thesis is proposed for medium-high-speed MANETs.In order to reduce transmission redundancy and collisions without decreasing packet delivery ratio,the rebroadcast probability at each node is adjusted dynamically and adaptively according to upstream and downstream node density.There is a controllable tradeoff,by adjusting the parameter,between the packet delivery ratio,the delay and the transmission overhead incurred by rebroadcast based on node density.By extending VDDS to NDB scheme,a promoted scheme NCDB(a Neighbor Coverage and Density-based Broadcast scheme)is obtained.Benefitting from VDDS for its accelerating data propagation,NCDB further reduces the average end-toend delay and improves its adaptability to node mobility.The schemes proposed in this thesis are evaluated by comparison with the latest and the classic multicast and broadcast schemes.The simulation shows how the overhead,the delay and the packet delivery ratio are affected by node mobility,network size and traffic load.Each of the proposed schemes exhibits its respective superiority through comparative analysis of simulated data in different network scenarios.All research shows that the selection of group communication scheme depends on the specific network environment and traffic load.At the end of this paper,a detailed summary is concluded to explain how to choose the proper group communication scheme.