Routing Algorithm And Application Research Based On Historical Encounter Information In Opportunistic Networks

The opportunistic network is a multi-hop and self-organized network which utilizes the movement of the node to realize the opportunity communication.This kind of network can play a good advantage in some extreme conditions,instead of the traditional network.With the rapid development of wireless communication technology and the popularity of mobile smart devices,the opportunistic network is applied in more and more fields,promoting the development of opportunistic networks.In the opportunistic network,people use various kinds of mobile smart devices,and during people's movement,devices self-organizing themselves into network to achieve the opportunistic communication.In this kind of mobile smart devices based opportunistic network,the network topology is complex and changable because of the uncertainties of nodes' mobile behavior and the limited comunication capabilities of handheld smart devices.So there doesn't exist the real-time and stable communication link.Routing algorithms for this kind of networks should consider the node's mobile transmission delay,communication disconnection,energy consumption and many other problems.Also,for various application background,research on message dissemination and routing strategy for the opportunistic networks gradually shows diversified development due to varied application requirements and movement patterns of carriers of mobile smart devices,.Firstly,this paper introduces the significance of research background on opportunistic network,research status and the main application fields.Then we focuses on the routing protocols and mobile movement models.Although the existing routing algorithms have good performance in some specific network scenarios,but they do not consider the mobility characteristics of nodes and social relations.these factors can affect the delivery efficiency.(1)According to the mobility characteristics of nodes and the social relations among nodes,this paper proposed an encounter-based routing algorithm to forward messages.Firstly,the proposed algorithm computes forwarding efficiency of each node depending on the encounter histories.Meanwhile,considering the uncertain transmission time with messages of varied size,the algorithm computes the average contact duration based on the past information.Thus,a message may be directly forwarded to the destination node,or it is forwarded to other nodes if and only if the candidate node may encounter the destination node with a higher probability and a longer average contact duration between them.The experiment results prove the proposed algorithm outperforms several other routings in terms of message delivery rate,message redundancy and average delay.(2)To improve the utilization of smart devices,this paper first introduces the shortcomings of message transmission via Wi-Fi under traditional opportunistic networks,and then analyzes the message transmission process in traditional opportunistic networks with Wi-Fi technology,and finally proposes a time-sharing and multi-connected message distribution mechanism based on historical records.Making use of the time-sharing mechanism,the node Wi-Fi state switching condition is established,which makes the smart device switch between the hotspots state and the search state,so as to avoid the communication blocking caused by the nodes in the same state;At the same time,multi-connected mechanism can increase the node's communication opportunities.Moreover,according to the history records of the encounters between nodes,we optimize the routing paths of messages and always choose the node which meet the destination more frequently as relay nodes.The experimental results show that the time-sharing and multi-connection based message distribution strategy can improve the transmission performance of the opportunistic network,balance the energy consumption of nodes and prolong the network lifetime.