A study on remote data retrieval strategies in underwater acoustic networks

In this paper we consider the problem of uploading data from a network of fixed sensors to a mobile sink, incorporated by an Autonomous Underwater Vehicle (AUV). We approach this problem by presenting U-Fetch, a protocol based on two levels of coordinated access. In U-Fetch, some head nodes retrieve data from their neighbors locally, and send all data to the mobile sink in bunches via a contention-free link, as the sink passes by. We compare this approach against two approaches endorsed by several works in the literature, namely multi-hop routing and polling. U-Fetch represents an intermediate approach between these two schemes, and constitutes a valid tradeoff in the presence of a mobile sink. We first substantiate this claim via some simple Monte-Carlo simulations. Finally, to confirm the validity of our approach, we reproduce the detailed behavior of U-Fetch in the event-driven ns2/NS-MIRACLE simulator endowed with the DESERT Underwater libraries, and present a set of simulation results that compare the performance of U-Fetch against multihop routing and polling.