| Delay tolerant networks originates from the research on interplanetarynetwork and characterized by long delay, high bit error rate,intermittently-connected links, changing topology and so on. Classic scenariosinclude military ad hoc networks,wild animal tracking networks,ritual areanetworks and pocket switched networks. In delay tolerant networks, researchesfocus on routing protocols、congestion problem and energy problems.Since wireless sensors are worn by people, so the nodes in delay tolerantnetworks are people and delay tolerant networks become mobile social networks.Utilizing social properties in routing methods for delay tolerant network isclose to the real application scenarios and can efficiently improve routingperformance, which make it a hot issue. We adopt a “store-carry-forward”approach. In such scenario, we cannot guarantee that a certain message can bedelivered successfully, but try our best to forward it to the destination node.Besides, we give an explanation of the architecture、basic Concepts andterminology of delay tolerant networks.And we also give the basic category ofexisting routing protocols.Then we introduce social properties of delay tolerant networks. Routingprotocols in delay tolerant networks adopts the following properties includenode contact and social tie strength、community、similarity and centrality、selfishness and friendship. Using these social properties we can chose routingnodes efficiently and improve delivery rate of the whole network.Furthermore,we introduce some routing protocols in our paper. These routingprotocols are Bubble Rap、SimBet、and routing protocols based on selfishnessand friendship、Homing spread、CS-DTN、SMART.We explain the social properties this routing protocols adopt and the forwardingstrategies. The performance of the above routing protocols are compared at the last of this section.We propose an efficient routing protocol ROCD based on overlappingcommunity, which first evaluate the social relationships of every two nodes basedon contact time,contact frequency and contact regularity. Node with long contacttime,high contact frequency and good regularity can serve as a relay. We givean algorithm for overlapping community detection based on the socialrelationships and introduce the strategy for tailoring.The main innovations of ROCD are,1. Mine social attributes in DTNs, so that researches of social networkand delay tolerant networks combine together;2. Consider the regularity of contacts between every two nodes and use thepenalty factor to measure the contact regularity, making the measurement of thesocial relations more comprehensive and accurate;3. During community Detection, find node pair with strong socialrelationships and use the node pair as leaf nodes of the tree structure, leadingto community overlapping each other naturally;4. Combination tree structure and community in ROCD, so that the algorithmpresents hierarchy.We introduce the running mode of the simulator The ONE,its important partsand important classes. The ‘core file’ includes some important implementationand one of them is Message.java, which is used to generating message or forwardingmessage. Routing file includes some popular movement model of delay tolerantnetworks.The most important configuration file in The ONE isdefault_setting.txt，which usually includes all the common parameters of thesimulation.The file interface includes some communication interfaces and oneof them is SimpleBroadcastInterface, which is used in our simulation as theinterface for Bluetooth communication and provides a constant bit-rateservice.Besides The ONE also includes some file like gui、data、realtrace，report. We use MIT Reality dataset in our simulation. MIT Reality datasetincludes communication data of100students during2004-2005academic year. But, we only use parts of it, i.e. Bluetooth communication data.We use The ONE to simulate our routing algorithm and compared to BubbleRap and SimBet and results show that ROCD has better performance in deliveryrate and average delay. |
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