Today, mobile networks and mobile devices enable applications for millions of users in diverse network environments. However, the potential of mobile networks has not yet been fully realized because such networks are often unreliable and prone to disconnection. Mobile network environments, ranging from well-connected mesh networks to extremely sparse Delay Tolerant Networks (DTNs), face a variety of connectivity challenges due to unpredictable links, coverage holes, and losses in the wireless medium.
In this talk, I will present a suite of protocols that overcome unreliability and improve connectivity in diverse mobile networks. At one end of the connectivity spectrum are sparsely connected DTNs, where the lack of an end-to-end path causes traditional routing protocols to break down. I will present RAPID, a DTN routing protocol that uses opportunistic replication coupled with a utility-driven algorithm to significantly improve a given routing metric. At the other end of the spectrum are well-connected mesh networks, where factors such as multipath fading lead to short disruptions that affect performance of interactive applications such as Voice over IP. I will present ViFi, a mesh network protocol that reduces disruptions using a probabilistic relaying algorithm that leverages overheard packets. Using RAPID and ViFi as examples, I will show how utility-driven and probabilistic algorithms can be used to implement protocols in a decentralized and highly uncertain wireless environment. Our deployment and experimental evaluation of these protocols in outdoor mobile testbeds demonstrate the effectiveness of our approach.
I will briefly describe some of my more recent works on improving energy efficiency in mobile devices. Finally, I will conclude by outlining future research challenges in designing self-adapting protocols to allow seamless operation and in improving the usability of next generation mobile devices.