Research On Routing Protocol Of Content-Based Pub/Sub Using Space-Time Property In Delay Tolerance Networks

With the rapid development of mobile computing, the quick steps of wireless communication technology, and the widespread appllying of wireless communicating manufacturers, researchers have paid great attention to the reasearch and application of wireless and mobile networks. Due to the tolerance of delay and interruption in network to some extent, delay tolerance networks, which can be used in the case that the network is disconnected in special and real life scenes. Message transmission is a vital and fundamental problem in delay tolerance networks, and has direct influence on performance of kinds of applications on the entire network. Fortunately, the decoupling between the publisher and subscriber make the content-based publish/subscribe be suitable to message transmission in delay tolerance networks. Therefore, the research on content-based publish/subscribe scheme in delay tolerance networks is of great worth and has wide application prospects.For all sorts of content-based pub/sub applications in DTN to realize event publication and subscription efficiently, selecting the routing scheme is critical. Apart from the traditional routings, the aim of routing in DTN is maximize the possibility of message transmitted. The message transmission occurs when two nodes contact in DTN, and meanwhile the change of node's location and the contacts bewteen them are uncertain. So, the pridiction of the nodes'locations and the possibilities of any node pair contact is vital to routing. At present, to instruct routing, researchers in and at abroad is tending to use the time of nodes'encounters in history to dipict the realtionship between nodes, whereas analysis of instance tell us that these thinkings are not be satisfied.This paper is based on the idea that not only using the time of nodes'encounters in history, but also using the space information, that is to say, using the space ang time together, to describe nodes'moving patterns and the relationship of any pair nodes more accurately, the purpose of which is to guide any node to select the optimal next hop for a message.Firstly, in this paper we model the delay tolerance networks and define the problem of realizing content-based publish/subscribe scheme in DTN formally, then propose a novel multi-level networks structure, STPSS, which can be used to content-based publish/subscribe in DTN,and a strategy of assigning weight values to subscriptions is raised to overcome the limitations of real environment. Furthermore, based on the improved STPSS, a Space-Time based on content-based Pub/Sub Routing Protocol in DTN--STPSRP is proposed. Finally, results of experiments show that the proposed technical performs better in aspects of delay, the ratio of subscribers'satisfactory and the traffic of whole network than existing technologies, meanwhile the value of some parameters can have an effcet on the network performance.