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Probabilistic Cooperative Caching-Based Content Subscribing in Opportunistic Mobile Networks

Publish/subscribe (pub/sub) based data access techniques have been actively researched in opportunistic mobile networks (OppNets) that can be characterized by the intermittent connectivity and limited network capacity. Because of time-varying network topologies due to the node mobility, it becomes an issue to guarantee end-to-end path for seamless communication. In this paper, we propose a probabilistic cooperative caching based content subscribing scheme, called PCC, to enhance data availability and accessibility in OppNets. We first present the basic pub/sub based operations and their corresponding information to be maintained and exchanged. Then we measure the expected data delivery latency as a basis for the data utility and define a data utility function based on the time-to-live of data and data delivery latency. We further refine exchanging the data using a multi-objective linear programming and propose a heuristic approach to cooperatively cache the data among nodes. We conduct extensive simulation experiments for performance comparison using the opportunistic network environment simulator (ONE). The simulation results show that our scheme outperforms other three existing schemes (i.e., Ad hoc Podcasting, Content Place, and Least TTL) in terms of delay, number of delivered data, and number of hops, and indicate that our scheme can be a viable approach in OppNets.