Model And Applications In Delay Tolerant Networks

Recently, with the maturation of wireless network technology and the popularity of smart portable nodes, researches and application on Delay Tolerant Networks(DTNs) are developing rapidly. Not limited by the network structure, DTNs make full use of portable devices'bandwidth, computing, storage and other resources, and provide users with data transmission, data dissemination, information query and other network services via a variety of connecting ways. Since DTNs need no additional base station devices to form the network, they have wide application prospects and far-reaching impacts on the realization of future pervasive computing.There exist a lot of problems in the practical application of Delay Tolerant Networks, for example:dynamic changing of the network topology, the limitation of the transmission bandwidth, the limitation of the portable terminals and so on. Although previous researchers have done a lot in these areas, most models are only suitable for specific scenarios, and the transmission and stability performance of algorithms need to be improved. To address the above issues, this paper conducts a comprehensive analysis and research in DTNs on the basis of drawing on the research methods in the traditional network. The main contributions are as follows:Based on data traces collected from the real environment, we experimentally investigate the pair-wise contact information and the correlation of community and geography information. Then, we propose the concept of geography-aware community (Geo-community) and analyze the distribution of the inter-contact time and the user sojourn time distribution over geo-communities,both of which characterize the network connectivity features. This work lays a foundation for modeling.By considering the user mobility among different communities as a Markov renewal process, we use the single-step transition probability and sojourn time probability to build nodes'static mobility model, and get the static distribution probability and geo-centrality which reflect the contact between nodes and community, so as to solve the data dissemination problem in DTNs. Furthermore, we use the temporal correlation single-step transition probability and conditional sojourn time probability to build nodes' dynamic mobility model, obtaining the instantaneous distribution probability which reflects the movement locus of nodes, so as to solve the information query problem in DTNs.Using the past recorded information to predict the future contact information with other neighbors and introducing the value of node utility, an adaptive asynchronous sleep scheduling mechanism is proposed for DTNs. The propose sleep scheduling mechanism can improve the energy efficiency effectively, and is compatible with existing data transmission protocols.