Research Of Data Forwarding Technology Based On Region Type In Opportunistic Networks

Mobile Opportunistic Network(MON)is one of the emerging communication paradigms in wireless mobile communications.MON is defined as a mobile network where the communications between nodes are challenged by sporadic and intermittent contacts,along with frequent disconnections and reconnections,and thus a stable communication path from the source to the destination usually cannot be obtained.The MON applications are very diverse,such as the vehicle networks for traffic information sharing,the mobile sensor networks for wildlife tracking and the pocket switched networks comprised of human-carried mobile devices.The nodes of MONs always move frequently,and the communication devices on nodes are switched between on/off statuses unpredictably.These characteristics of MONs make the end-to-end paths dificult to be established,making the traditional routing methods cannot be applied for MONs.In MONs,the encountering opportunities between nodes are exploited for the data dissemination,i.e.,the data packets are disseminated from the data holders(nodes carrying data packets)to the encountered ordinary nodes(nodes not carrying data packets),and hence the data packets are expected to be transferred to the destination node by discrete hops even when an end-to-end communication path never emerges.Therefore,each node in MONs deals with the received data packets in the manner of “carry & forward”.Each node is allowed to carry the received data packets until it encounters other nodes,and the carried data packets will be disseminated to some selected encountered nodes.Due to the uncertainty in future movements of nodes,the data dissemination method(especially how to select the proper relay nodes)becomes a vital issue for the improvement of delivery ratio and reduction of delivery delay in MONs.To avoid the costly flooding of data packets,the data packets are usually disseminated by selecting one or multiple relays at the encounters between nodes.However,the mobility patterns of nodes will be different in various types of regions(such as residential regions,commercial regions or industrial regions),i.e.,the regularity in movement directions and movement ranges of nodes is frequently varied since the nodes move between different types of regions.This issue has not been focused and investigated for the data dissemination in most existing works.The main contributions of this thesis are as follows:(1)the adscription degrees of region types extraction algorithm for nodes in MONs.By using the related knowledge of fuzzy mathematics,we further derive the fuzzy similarity matrix and the message attributes correlations.Accordingly,theregion types of nodes and their adscription degrees are obtained.(2)A Region Type-based Data Dissemination Method(RTDDM)is proposed for MONs.The method exploits the type correlations of regions to establish nodes movement model,and establishes the Markov decision model for selecting the relay nodes according to some factors such as the region type correlations,region weights and node region type attributions.Simulation results show that under different network environments,compared to BUBBLE and BINARY algorithms,RTDDM algorithm selects more efficient relay nodes through the Markov decision model,which significantly improves data delivery rate and reduces data latency.In this thesis,the adscription degrees of region types extraction algorithm for nodes in MONs.and RTDDM algorithm are proposed,and the simulation experiments are carried out for these two algorithms.However,the two algorithms still have room for improvement.The future work can deeply study the following contents: The network environment is closer to reality;In the RTDDM algorithm,consider the influence of the period type detection period duration of the node on the selection of the relay node;in the Markov decision,consider the influence of the movement law of the node in the same area type on the selection of the relay node.