Scientific context

Internet of Underwater Things (IoUT) is currently an international trending topic. It concerns applications in ocean engineering [1], environmental monitoring [2] or underwater threats detection [3]. These three applications are especially important for Floating Offshore Wind Turbines (FOWT) that record today an incredible growth in France of 1GW per year according to the French Low Carbon Strategy. Acoustic communications are usually employed to connect underwater objects. They are typically organised inside a Underwater Acoustic Sensor Network (UASN). Fig.1 summarizes possible applications of UASN around FOWT, pollution and seismic activity monitoring. As in terrestrial IoT, the underwater assets can be self-organised in multi-hops to extend coverage and to reduce energy consumption. Above the surface, high data rate channels via satellite or 5G radio link maintain basically connectivity from the shore up to the underwater things. Acoustic Wireless Communications (UWA) are particularly slow. With a speed of sound of 1500 m/s, the scale factor is 200000 slower if you compare with speed of light for radio communication. But 5 times faster than in the air! Moreover, acoustic sounds can cover several kilometres with small autonomous equipments even in case of turbidity (presence of particles). For all of these reasons, underwater acoustic is preferred to optic or radio communication. Nevertheless, the data rate is an issue for underwater acoustic communication. Affordable commercial acoustic modems offer bitrates from 50 bps to 200 kbps (the price of the modem is usually indexed on the available bandwidth) with various Maximal Transfer Unit (MTU) from 64 bits (in JANUS [4] protocol from NATO) to 128 Bytes (for the AHOI modem from Technical University of Hamburg by example). Such heterogeneity in the devices is also an issue for UASN. 

Currently NATO is promoting the interoperability but through a monolithic layer 1 and layer 2 stack by the JANUS protocol [4]. No underwater equipment (sensor nodes, underwater and surface vehicles,…) can easily interoperate today. The network stacks are designed in silos and the Internet Protocol (IP) is totally absent like wireless industrial networks 20 years ago. Building a layer 3 interoperability through an Internet Protocol (IP) adaptation layer is a fundamental goal of the UCHIC project.

In the literature, very few research articles address the IP convergence problem for underwater networks. The limited interoperability between underwater networks and conventional terrestrial networks restricts the utilization of underwater data and complicates its integration into broader information systems, particularly those leveraging wireless technologies and 5G infrastructure, due to the lack of common addressing schemes and data representation formats. While achieving interoperability at layer 2 remains challenging due to a highly fragmented manufacturer market, it can be achieved at higher protocol layers, particularly at the IP level, provided that packet size constraints can be addressed. In 2016, Sun and Melodia [6] proposed an original encapsulation (based on 6LoWPAN) but required 2 bytes to support IPv6 or IPv4 packets with no application layer consideration as security services. Recently, Parrein, Morozs and Toutain [7] has proposed a conceptual approach based on SCHC (Static Context Header Compression [8]) of only 1 byte for IPv6 encapsulation and constrained applications (i.e., CoAP) for IoUT.

SCHC, standardized by the Internet Engineering Task Force (IETF), is a framework that provides both header compression and fragmentation capabilities. IMT Atlantique plays a leading role in its development, serving as both a major contributor and chair of the working group focused on this technology. SCHC has been widely embraced beyond the IETF, with major standardization organizations including IEC, 3GPP, and LoRa Alliance incorporating it into their specifications. This adoption has led to significant real-world implementations, most notably in the utility sector where it has enabled the deployment of 7 million gas meters across Italy and Greece. SCHC’s inherent design characteristics make it naturally suited for Internet integration, and its applicability extends beyond its original scope to encompass emerging domains such as time-sensitive networks and space communications.

Fig. 2: Sea trials around SEM-REV, Research Infrastructure near le Croisic (Blue IoT Eolia project, June 2022). The 4 yellow watertight beacons are visible on the deck of the boat.

This project aims to extend SCHC into a new domain of severely constrained networks, building on our standardized architecture for Sigfox (RFC 9442), which defines SCHC adaptation for uplink and downlink transmission over the Sigfox LPWAN technology. While maintaining SCHC’s core compression and fragmentation capabilities, we seek to push its standardization boundaries by developing it into a convergence layer that can unify diverse acoustic modem technologies. The objective of U-CHIC project is to further investigate the potential of SCHC over IoUT (security and fragmentation purposes in particular) to provide a full wireless IPv6 secure connectivity from the shore to the seabed. Last but not the least, the concept, ideas and development around Underwater Acoustic Sensor Network (UASN) must be validated on real experiment experiments in tank, lake and sea at the end. It constitutes a critical and necessary step of this research usually required for valuable international publication. The sea trials are also good opportunity to attract attention of potential industrial partners that expect some advanced prototypes in an operational environment (TRL 7). The Fig. 2 illustrates our skills to carry on experimentations at sea here on the SEM-REV site on June 2022 for the Blue IoT Eolia Project funded by Pays de la Loire region (here in collaboration with Centrale Nantes, member of Nantes Université).

References:

[1] Benoît Parrein, Fekher Khelifi, François Babin, Thierry Grousset, Jean-Marc Rousset, et al.. Underwater acoustic sensor network to monitor floating offshore wind: SEM-REV sea trials. IEEE OCEANS 2024, Jun 2023, Limerick, Ireland. ⟨hal-04190985⟩

[2] Diamant, R., Alexandri, T., Barak, N. et al. A remote sensing approach for exploring the dynamics of jellyfish, relative to the water current. Sci Rep 13, 14769 (2023). https://doi.org/10.1038/s41598-023-41655-8

[3] L. Shen, Y. Zakharov, B. Henson, N. Morozs, B. Parrein and P. D. Mitchell, “Target Detection Using Underwater Acoustic Communication Links,” in IEEE Journal of Oceanic Engineering (Early Access), doi: 10.1109/JOE.2024.3455414.

[4] Duarte, C. M., Chapuis, L., Collin, S. P., Costa, D. P., Devassy it, R. P., Eguiluz, V. M., … & Juanes, F. (2021). The soundscape of the Anthropocene ocean. Science, 371(6529), eaba4658.

[5] J. Potter, J. Alves, D. Green, G. Zappa, I. Nissen, and K. McCoy, “The JANUS underwater communications standard,” in 2014 underwater communications and networking (UComms), pp. 1–4, IEEE, 2014.

[6] Y. Sun and T. Melodia, “The Internet underwater: An IP-compatible protocol stack for commercial undersea modems,” in Proceedings of the 8th International Conference on Underwater Networks & Systems, WUWNet ’13, (New York, NY, USA), Association for Computing Machinery, 2013.

[7] Benoît Parrein, Nils Morozs, Laurent Toutain. An internet protocol adaptation layer for underwater acoustic networks. Forum Acusticum 2023, Sep 2023, Turin, Italy. ⟨hal-04192238⟩

[8] Hussein AL HAJ Hassan, Ali Krayem, Ivan Martinez, Laurent Toutain, Alexander Pelov. SCHC over LoRaWAN, a Framework for Interoperable, Energy Efficient and Scalable Networks, The 9th IEEE World Forum on Internet of Things (IEEE WFIoT2023), Oct 2023, Aveiro, Portugal. ⟨hal-04244739⟩