The Magazine for Underwater Professionals

Sep/Oct 2017


JANUS, the first digital underwater communications standard

New protocol opens the way for the development of many exciting underwater communication applications, writes Dr John Potter

Tests of JANUS were conducted using the Centre for Maritime Research and Experimentation's Littoral Ocean Observatory Network (LOON), a test bed made by acoustic tripods forming an underwater acoustic network. Photo: NATO

Finally, after 70 years with only the familiar old ‘Ger-trude’ analogue standard, the support of NATO Allied Command Transformation (ACT) has allowed the NATO Science and Technology Organisation (STO) Centre for Maritime Research and Experimentation (CMRE) to develop ‘JANUS’; an open, digital standard. It is sometimes hard to get excited about standards, but they are critical enablers for interoperability, and with this new standard in underwater digital communications, we take the first step towards the underwater version of the smartphone and the Internet of Underwater Things (IoUT).

The formal acceptance of JANUS as a standard, by NATO and its 29 nations, comes at the end of a 10-year process of research, development, negotiation, campaigning, testing and refinement to achieve the alignment of key stakeholders in the user, research and industrial communities. While initially established as a NATO standard, JANUS is open and intended to serve both military and civilian applications internationally.

JANUS is not simply a point-to-point communications protocol; it allows the dynamic discovery and integration of underwater nodes into an ad-hoc network, providing a bootstrapping mechanism to create an IoUT. It is deliberately simple and robust, minimising demands on devices, thus maximising backwards compatibility with existing assets.


Yet JANUS also allows manufacturers to develop sophisticated decoding algorithms if their devices have the computational and energetic capacity, maximising performance and providing a means to monetise integration of this open standard into communications equipment.

JANUS is the Greek and Roman god of doorways, openings and gateways, and so the JANUS communication standard opens gateways between assets from different suppliers, providing a ‘lingua franca’ with which to communicate. JANUS is also extremely flexible in application, with 256 defined user classes, each of whom can determine up to 64 different templates for data encoding, with optional data trains of arbitrary length, seamlessly appended to the basic 64-bit header. The JANUS Medium Access Control (MAC) mechanism provides a means to ‘reserve’ the acoustic channel, to allow other (perhaps more optimised or faster) acoustic exchanges to be conducted without interference. Data can be encrypted and application templates need not be published, protecting sensitive information.


JANUS thus opens up exciting new possibilities in the market place, as happened with Wi-Fi in the terrestrial portable devices market. As the first international standard of its type, JANUS has the potential to tame the ‘Tower of Babel’ in underwater communications, in which each modem manufacturer currently employs proprietary protocols that cannot communicate with devices from a different supplier. It is now possible to develop a wide range of applications, from distributing underwater AIS pictures of vessel traffic and surface meteorological conditions to the co-ordination of heterogeneous autonomous and remotely controlled vehicles working on a subsea installation, and enabling error-corrected communications with distressed submarines.


Dr John Potter is a principal strategic development officer at the NATO STO Centre for Maritime Research and Experimentation





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