CoLlAborative eMbedded networks for submarine surveillance (CLAM) Project Deliverable D4.1 State of the art on networking and distributed processing and exploitation of mobility and heterogeneous systems for improving system performance

Document Overview In the present deliverable, we briefly summarize the current trends and state-of-the-art on networking solutions for Underwater Wireless Acoustic Sensor Networks (UWASNs). In particular, the focus of the document is on Medium Access Control (MAC), Routing, Localization and Synchronization, as well as on node positioning and mobility. Our literature search points out that, although several solutions have been specifically proposed for underwater networks, there is no optimal protocol fitting all scenarios. Depending on the specific conditions and variability of the underwater environment, different classes of protocols perform better in some cases. As such, the choice of the optimal protocol to deploy is heavily scenario-dependent. In addition to improving performance at each layer of the protocol stack, one of the goals of the CLAM project is hence to investigate new solutions to dynamically adapt the protocol behavior to the acoustic channel conditions, to varying traffic loads and to topological changes. In Section 1 we present the existing state-of-the-art on MAC protocols. We provide a taxonomy of the current solutions, identifying different classes of underwater MAC protocols and selecting for each class the more representative solutions. Routing solutions for UWASNs are investigated in Section 2, distinguishing between general approaches to the routing problem and other approaches based on the concept of Delay-Tolerant Network (DTN). Routing protocols which explicitly address in-network data aggregation are also described. In Section 3, among all the open issues for 3D UWASNs, we address the currently proposed solutions for distributed underwater GPS-free localization and time synchronization, which are most critical services in such networks. Section 4 proposes a survey on existing solutions and approaches for topology design and topology control problems. Finally, in Section 5, we introduce mobility solutions for UWASNs, showing how node mobility can impact and improve the protocol operations.