Underwater Ad-Hoc Networks: A Review

Underwater sensor networks have become increasingly interesting in the past four decades. They can be used in a multitude of scenarios, commercial and military alike. Underwater networks can communicate in several ways, but when nodes are far apart, underwater acoustic communication is the only feasible way. The complex underwater acoustic channel puts high demands on the network protocols. The physical layer needs to contend with short coherence times, high intersymbol interference and significant Doppler spread. The routing protocol needs to handle intermittent connectivity and mobile network topologies, such as autonomous underwater vehicle networks. The medium access control protocol needs to manage medium access with high latency and potentially high packet loss ratios without congesting the network. The available acoustic modems are still rather expensive, which limits the size of a sensor network. Voices have also been raised from the academia for a paradigm shift, from hardware-defined, proprietary modems to software-defined, open-architecture modems, in order to accelerate research in the field and enable interoperability. This paper reviews the recent advancements in designing and implementing underwater networks on several levels and discusses some interesting approaches to underwater ad-hoc networking. The focus lies on acoustic communication.<br>

Underwater Ad-Hoc Networks: A Review

Underwater sensor networks have become increasingly interesting in the past four decades. They can be used in a multitude of scenarios, commercial and military alike. Underwater networks can communicate in several ways, but when nodes are far apart, underwater acoustic communication is the only feasible way. The complex underwater acoustic channel puts high demands on the network protocols. The physical layer needs to contend with short coherence times, high intersymbol interference and significant Doppler spread. The routing protocol needs to handle intermittent connectivity and mobile network topologies, such as autonomous underwater vehicle networks. The medium access control protocol needs to manage medium access with high latency and potentially high packet loss ratios without congesting the network. The available acoustic modems are still rather expensive, which limits the size of a sensor network. Voices have also been raised from the academia for a paradigm shift, from hardware-defined, proprietary modems to software-defined, open-architecture modems, in order to accelerate research in the field and enable interoperability. This paper reviews the recent advancements in designing and implementing underwater networks on several levels and discusses some interesting approaches to underwater ad-hoc networking. The focus lies on acoustic communication.<br>

Adaptable Underwater Networks: The Relation between Autonomy and Communications

This paper discusses requirements for autonomy and communications in maritime environments through two use cases which are sourced from military scenarios: Mine Counter Measures (MCM) and Anti-Submarine Warfare (ASW). To address these requirements, this work proposes a service-oriented architecture that breaks the typical boundaries between the autonomy and the communications stacks. An initial version of the architecture has been implemented and its deployment during a field trial done in January 2019 is reported. The paper discusses the achieved results in terms of system flexibility and ability to address the MCM and ASW requirements.