Research And Design On Message Optimization Mechanism Of Spray And Wait Protocol In Opportunistic Mobile Social Networks

Opportunity Mobile Social Networks(OMSNs)unlike the traditional mobile networks,the intermittency and uncertainty of OMSNs make message forwarding be a challenging issue.Take this characteristic into account,the design of efficient routing protocols is often an important part of the message forwarding mechanism in OMSNs.In addition,the movement of people often form multiple communities because of the same interests and social relationships.Therefore,it is a hot research point in OMSN to improve the routing efficiency by studying the society of nodes in OMSN.In this thesis,the research of message optimization mechanism of spray and wait protocol in OMSN is carried out in view of the above characteristics and the insufficient of existing algorithms.The architecture and key technologies of OMSNs are firstly researched.Then a brief description of some routing algorithms and simulation tools is provided,which lays the foundation for the comprehensive research and analysis of OMSN.The background of Android Bluetooth communication is also introduced,which provides a theoretical and technical basis for the design and implementation of the following prototype system.Considering the society and dynamicity of OMSN,a multi-community message forwarding model is established.At the same time,the dynamic quota-controlled mechanism in two-period Spray and Wait is analyzed,and the message forwarding model is applied in this routing protocol.On this basis,a quota-controlled routing problem of minimizing the average number of copies of a message that satisfies the required delivery probability under the given TTL(Time-to-Live)of the message is formulated as a nonlinear optimization problem.To solve this problem,an improved genetic algorithm called GAPTO(Genetic Algorithm for delivery Probability and TTL Optimization)for the dynamic quota-controlled routing scheme to reduce the routing cost further is proposed.In addition,a cost-efficient dynamic quota-controlled routing protocol in multiple communities based on GAPTO is proposed,which can dynamically adjust message copies according to its assigned delivery probability and TTL in different communities on the shortest path.Both the numerical and simulation results show that our routing with the proposed algorithm has a good performance.Finally,a prototype system of cost-efficient dynamic quota-controlled routing in multiple communities based on Android is implemented.The system adopts the message forwarding model and routing optimization algorithm proposed in this thesis,which accepts the user's expected delivery ratio and TTL of message to complete the message forwarding by Android Bluetooth communication between nodes.The testing results show that the system can perform the functions of the cost-efficient dynamic quota-controlled routing protocol completely.The research in this thesis not only can widely apply to the real world,but also can provide ideas for the study on routing protocols in OMSNs,which has a good theory value and application prospect.