A COMMUNICATION FRAMEWORK FOR OPPORTUNISTIC MOBILE NETWORKS WITH DIVERSE CONNECTIVITY

An Opportunistic Mobile Network (OMN) refers to the network paradigm where wireless devices communicate with each other through the opportunistically formed wireless links. Routing in OMN relies on node mobility and the store-and-forward mechanism. It is paramount to have energy efficient, robust and cost effective routing protocols in such environments. Previous research usually assumes that the connectivity in such networks is extremely sparse and that the network is purely infrastructure-less. However, real world deployments of OMNs actually exhibit di- verse connectivity, i.e., connectivity may range from sparsely connected to well connected or the network may coexist with infrastructure. Consequently, the simplified assumptions of previous solutions lead to suboptimal behaviors of routing protocols, which includes redundant transmissions, too much or insufficient data replications, poor forwarding decisions, etc. In this dissertation, in order to address the aforementioned problems, we propose a communication framework for OMNs with diverse connectivity, which consists of a series of algorithms and protocols that aim to provide energy efficient, robust and cost-aware communication services to applications. In this framework, we propose: a) algorithms that carefully schedule transmissions in an opportunistic contact involving multiple nodes; b) routing protocols that consider simultaneously mobile nodes' delivery capability and traffic load; c) mathematical tools that characterize not only Inter-Contact Times but also their correlations; d) adaptive mechanisms to realize dynamic data replication; and e) forwarding strategies that optimally trade-o_ energy consumption and delay in a cost-aware fashion when utilizing infrastructure. We evaluate the proposed routing protocols and algorithms through extensive simulations using both synthetic network models and real world mobility traces. We also conduct real world experiments on a wireless testbed to demonstrate their practicability. The evaluation results show that, with the assumption of diverse connectivity in mind, the proposed algorithms and protocols greatly improve the networking performance and efficiency. The consideration of delay correlations and a mechanism for dynamic replication are critical for a routing protocol to perform well with a wide range of network connectivity. When infrastructure is present, our proposed forwarding strategy helps improve the energy-delay trade-off when cost is a constraint