Research On Message Transmission In Opportunistic Networks

In traditional wireless multi-hop networks,due to the existence of node movement,signal attenuation,obstacles and other factors,the network often keeps an interrupted state,besides that,a complete end-to-end path between the source node and the destination node cannot be established,which resulting in message transmission failure.Opportunistic network is the network that is designed to solve these kinds of problems.It utilizes the mobility of nodes to build bridges among nodes and make those nodes communicate with each other.And the accustomed wireless network's "store-and-forward" mode has been transformed into mode of "store-carry-forward".This thesis firstly outlines the opportunistic networks' fundamental information,includ-ing the notion,research backdrop,domestic and foreign research status,major applications at the present stage and existing key issues needed to be resolved of the opportunistic network,etc.,then analyzes the several significant routing protocols of the opportunistic network,and find out the present routing algorithms mainly studied in fields of how to improve network performance,including improving the success rate of information transmission,decreasing message transmission delay of opportunistic network,and lessening total consumption of op-portunistic network.Next,on the foundation of previous research and analysis of opportunis-tic network routing algorithms,the classic Prophet opportunistic routing algorithm is mainly analyzed in this thesis and my own routing algorithm based on the Prophet algorithm is proposed then.Prophet algorithm amalgamates both flood forwarding and encounter-based prediction forwarding thinking,calculates the encounter probability among nodes based on the frequency of historical encounter frequency.During the process of transmission,infor-mation is forwarded only to those nodes with a higher encounter probability.Therefore,Prophet algorithm can lessen the profligacy of network resources and channel congestion caused by the flooding forwarding algorithm at a certain degree.However,this algorithm has self-evident deficiencies:there is no regularity during the process of nodal motion,be-sides that,the success rate of message delivery is relatively low.Aiming at the shortcom-ings of the current Prophet algorithm,this thesis proposes a new routing algorithm which is based on the primitive Prophet algorithm.Since the primitive Prophet algorithm's success rate of message delivery is relatively low,based on the research of the traditional Prophet routing algorithm,this thesis premeditates the properties of the node movement model un-der the above-mentioned conditions,the characteristics of the encounters duration among nodes,the utilization of the remaining cache of intermediate nodes in the transfer procedure among nodes,and the properties of messages' time-to-live,an enhanced routing algorithm is proposed.The consequences of emulation demonstrate that,under a given motion pattern,the algorithm proposed in this thesis could effectively enhance the success rate of message delivery,efficaciously decrease network overhead,and efficaciously decrease the message delivery times.In the end,the ONE simulation platform is utilized to simulate the improved Prophet algorithm,and compare it with the classic routing algorithm.Experiments' results demon-strate that this improved algorithm has relatively great performance in enhancing the success rate and decreasing delay in information transmission.