Optimizing Downloads over Random Duration Links in Mobile Networks
Amber Bhargava, Spencer Congero, Timothy Ferrell, Alex Jones, Leo Linsky, Jayashree Mohan, Bhaskar Krishnamachari · 2016
Short range vehicle to vehicle and device to device communications are of growing interest due to their utility for vehicular safety and infotainment applications as well as for improving the capacity of cellular networks. These mobile systems are characterized by ephemeral, stochastic links. We consider a fundamental problem in this domain -- how to maximize the amount of useful content downloaded by a client from a server over an encounter that lasts a random amount of time. We assume that the distribution of link duration is known or estimated \emph{a priori} based on historical as well as real-time measurements. We present MERLIN (Maximum Expected download over Random LINks), a single-phase file request protocol that is provably optimal. We evaluate MERLIN comprehensively via simulations based on both ideal link duration distributions as well as empirical distributions obtained from real vehicular mobility traces (from Taxis in Shanghai and Buses in Chicago). We also present two Contiki OS-based implementations of MERLIN (with local and remote calculations) evaluated on the Tmote Sky wireless embedded platform.