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Hands-on with JANUS: Understanding, Implementing and Using the first Digital Underwater Communications Standard

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Systems Concepts and Integration

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interoperability, JANUS, support in distressed submarine operations, underwater acoustic networks, underwater AIS and METOC, Underwater digital communication standard, unmanned systems cooperation


For over 70 years the only underwater (UW) communications standard has been the analogue UW telephone, known as ‘Gertrude’, currently the main solution adopted by NATO, military and civilian bodies when underwater communications is required, e.g. in support to distressed submarine escape and rescue operations. With the rapid rise in the availability and use of autonomous unmanned UW assets, there has been a pressing need for a wireless digital UW communications standard that can be used to convey any type of data and support machine-to-machine exchanges. Given the impairments of optical and radio propagation in water, acoustic communication remains the most efficient way to communicate underwater over distances in the order of hundreds of meters and beyond. Among the several manufacturers of underwater digital modems, none is currently able to communicate with systems produced by different manufacturers. This imposes severe limitations on how cooperative networks of underwater assets can be effectively deployed. To break this interoperability barrier the NATO STO CMRE has developed, in collaboration with academia and industry, a simple and robust signalling mechanism to be used as the first standard for digital underwater communications. The proposed protocol, JANUS (after the Roman God of transitions, gateways and portals), has been iterated over close to 10 years and has finally been promulgated as a NATO standard (STANAG 4748) on March 24th 2017. JANUS is now to be implemented across the naval assets of all 29 NATO nations. JANUS however is not restricted to NATO, indeed not even restricted to military use, but open and available to both military and civilian use worldwide. The adoption by NATO navies is just the start. Driven initially by naval demand, we soon expect many UW modems to be offering JANUS as a communication protocol option, and to see its use spread to offshore oil and gas operations, oceanographic surveying, diver support and many other applications. JANUS not only provides an interoperable UW communications protocol for point-to-point communications, but offers a bootstrapping method for node discovery and the construction of dynamic ad-hoc networks. JANUS also offers the potential to dynamically negotiate and de-conflict operations that may not have been co-ordinated in prior planning, but which discover each other during operation. During the final stages of the promulgation process, NATO sponsored the NIAG SG190 study on JANUS with the objective of gathering insight from industrial players on how to continue the development path of JANUS. Among the topics addressed were: 1) Additional frequency bands; 2) New application classes; 3) Protocol extensions; 4) How to define JANUS compliance. The sponsored study has highlighted how the use of standardised methods may open the way to foster underwater node interoperability. This would catalyse the development of a wide range of underwater applications of operational relevance, including an underwater digital emergency channel (that can be seen as an underwater version of the “VHF Channel 16”) and Underwater AIS for water space management, just to cite a few. The use of JANUS has been already demonstrated in multiple sea trials conducted in Portuguese waters in cooperation with operational assets of the Portuguese Navy. Additionally, JANUS has been used and validated during the Dynamic Monarch 2017 (DYMH17) exercise in Turkish waters. It was installed on board a Spanish submarine and on different Rescue Ships: one from the Italian Navy, two from the Turkish Navy, one hosting the NATO Submarine Rescue System (NSRS). DYMH17 is the tenth in a series of NATO sponsored live Submarine Search, Escape and Rescue Exercises. It is the world’s largest submarine rescue exercise. DYMH17 is organised every 3 years by the International Submarine Escape and Rescue Liaison Office (ISMERLO) and is designed to test international forces’ interoperability and ability to respond


This Lecture Series aims to: a) Raise awareness of the challenges in communicating in the underwater domain and the importance of complying with standards. b) Introduce potential users, developers and decision makers to the definition of new procedures and operations based on the use of digital communication, machine-to-machine interaction and the deployment of underwater unmanned/autonomous assets. c) Give hands-on experience in the first underwater digital communication standard. d) Understand why JANUS is designed as it is, what potential it offers in maritime operations and the basics of how to implement the JANUS protocol in a practical system. This may lead to more nations participating in CDT exercises such as the REP series organized in cooperation with CMRE in Portuguese waters.


This Lecture Series will cover the following topics: a) Introduction to underwater communications; challenges and solutions. b) The need for a digital UW communications standard. c) The objectives of JANUS. d) The design principles of JANUS. e) JANUS physical layer design outline. f) JANUS Media Access Control Protocol and interference issues. g) Overview of the JANUS protocol data flow. h) JANUS wiki and resources. i) Matlab, and C baseline implementations. j) JANUS use cases and application scenarios including experiences and results from various sea trials, including the ones conducted in cooperation with the Portuguese Navy and DYMH17. k) Hands-on with JANUS: transmitting and receiving data using the baseline implementations. l) Steps forward towards extending the use of JANUS for machine-to-machine interaction in support to submarine escape and rescue operations and water space management.

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