Research On Opportunistic Network Routing Methods For Random Processes

The classical computer network is connected with each other by lines,and the network topology is fixed.In order to deal with some special situations,as one of the wireless ad-hoc networks,mobile opportunity network applications come into being.Different from the traditional computer network,the communication mode of mobile opportunity network depends on the random movement of each terminal node in the network.The source node carries messages in a certain area.When it meets any neighbor node,it creates a short communication opportunity.The core of mobile opportunity network routing is the communication mechanism between terminals as nodes.The focus of research on the communication mechanism of conventional mobile opportunity network is generally reflected in three aspects.The first one is to observe and discover the movement rules of terminal nodes,the second one is to predict the state of terminal nodes by summarizing their social attributes,and the third one is to design the communication mechanism of opportunity network by combining the movement rules and state prediction,in order to improve the evaluation index of mobile opportunity network routing.But for the scene with high degree of freedom,the network structure changes and network link updates are complex and changeable.The next state of any terminal node in any time network is only related to the current state,and it can not summarize the law from the past state to predict the future,so it can not use the conventional way to summarize the node law and predict the future state of the node,which leads to the decrease of the evaluation index of the opportunity path.In the scene applications with high degree of freedom of movement of terminal nodes,the single copy,multi copy and hybrid copy routing of opportunistic networks designed by conventional methods can not achieve the expected performance,so it is necessary to establish modeling methods and research and design corresponding single copy,multi copy and hybrid copy routing forwarding strategies to adapt to such scenes.The random movement of a highly free terminal in a given region is considered to be similar to the Brownian motion of pollen.The mathematical description of Brownian motion is a Wiener process,which is a continuous stochastic process,so the Wiener process has Markov property.In this paper,aiming at the scene modeling of application terminal with high freedom,we design an opportunistic network routing algorithm to improve the delivery rate of messages,reduce the cost rate and average delay of the network,save the power of terminal equipment and the consumption of network resourcesThe main contents of this paper are as follows:First,aiming at the problem that the traditional modeling method of opportunistic network scene focuses on finding the terminal motion law and predicting the future state of nodes to improve the delivery rate is not suitable for the highly liberalized scene of terminal motion.This paper establishes a modeling method of opportunistic network scene with high degree of terminal motion freedom based on the characteristics of special stochastic process.This method is the basis of contents in the following chapters.Second,it is impossible to obtain the node's movement law or predict the node's movement trajectory by conventional methods in the scene of terminal motion with high degree of freedom in mobile opportunity network,which makes the conventional single copy opportunity routing low delivery rate and high network overhead rate.Based on the Markov property of opportunity network node encounter in high freedom motion mode,this paper finds out the state transition rule of node message forwarding based on Markov decision process in network.According to the rule,a routing algorithm which can increase the delivery rate of opportunistic network is designed.This algorithm does not replicate the copy of message,so it belongs to the single copy routing of opportunistic network.At the same time,it can greatly reduce the average number of relay nodes and reduce the cost rate.After that,the correctness of the related model and theory is verified by simulation experiments.The proposed routing strategy is superior to the existing mainstream single copy algorithm in the simulation scenario,and achieves a good balance at the aspects of network delivery rate and network overhead rate.Thirdly,in the scene of terminal motion with high degree of freedom,the conventional multi-replica routing strategy in opportunistic networks relies on a large number of nodes to copy and deliver message copies or predicts the delivery probability based on the encounter probability,which results in the increase of delivery rate and the increase of network overhead rate.This paper is based on the Markov chain probability transfer law at the node encounter time This paper proposes a node forwarding strategy which can control the number of replicas in the opportunistic network.This strategy algorithm is multi replica routing in the opportunistic network because it replicates a limited number of message replicas in the first stage.After that,the correctness of the related model and theory is verified by simulation experiment.The proposed routing strategy can execute multithreading concurrently according to the designed message with limited number of copies,and has no special loss of network resources.Fourth,in the case of high degree of freedom of terminal motion in mobile opportunistic network,the conventional hybrid routing algorithm of opportunistic network focuses on improving the delivery rate and reducing the average network delay,which increases the network overhead rate and increases the power consumption of terminal equipment.In this paper,based on the previous work,a hybrid segment forwarding strategy is designed by combining the characteristics of single replica and multi replica routing in opportunistic networks.The strategy is divided into two stages:single replica stage and multi-replica stage.After that,the correctness of the related model and theory is verified by simulation experiment.The proposed routing strategy combines the advantages of single replica and multi-replica forwarding strategies.By comparing the three evaluation indexes of opportunity network,it can meet the requirements of the scenario and avoid the disadvantages of single replica and multi-replica routing to the greatest extent.Compared with other excellent routes,the evaluation has special advantages in the scene with strong randomness,and reduces the power consumption of terminal equipment.