Sea Technology

MAY 2017

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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10 st / May 2017 www.sea-technology.com merged submarine to com- municate with other subma- rines, surface ships or land stations without sending out any kind of radio transmitter antenna, resulting in the risk of interception. After the Cold War, this communication paradigm changed completely. Tacti- cal communication over long distances in the range of 10 to 50 naut. mi. be- tween submerged subma- rines or a mother ship and submerged diver delivery vehicles have increasingly come into focus. Up to now, most of the communication has been analog by means of acoustic waves. They are exposed to relatively low attenuations. Acoustic commu- nication systems and transducers are small enough to be installed both on submarines and on small diver delivery submersibles. They can also be carried by human divers. New Requirements for Military Digital Communication With regard to military purposes, digital underwater communication has been identified as a key technology for operation of submarines with surface vessels and for com- munication with UUVs or AUVs. This is especially true for the areas of autonomous sensor networks for mine counter- measures (MCM) and anti-submarine warfare (ASW). The possibility to communicate with each other enlarges the range of information exchange and improves decision making within an operational scenario. The collection and right combination of all available information from partners or reachable sensors will make a common and thorough overview of the scenario possible. The role of submarines in many operational scenarios requires a much higher level of connectivity with the out- I n scientific applications, digital underwater com- munication methods have been in use for a long time, while in military applica- tions, analog communica- tion has been the norm. However, recently, digital underwater communica- tion has gained military importance. It can improve and even replace older technologies. In the scientific world, digital underwater com- munication methods are used to communicate with manned and unmanned underwater vehicles in or- der to transfer telemetry or status data or to guide the ve- hicles. These methods are suitable for military applications, too. History of Military Underwater Communication Long-range digital underwater communication with sub- marines is currently limited to either very low-frequency (VLF) or extremely low-frequency (ELF) radio communi- cation. ELF communication works with electromagnetic waves of frequencies far below 100 Hz. It can reach almost every submarine around the world in depths down to 300 m. The main disadvantage is a one-way communication scheme requiring very large transmitter antennas reaching several tens or hundreds of kilometers in size. Furthermore, the communication data rate is limited to approximately 10 bits per minute. Primarily, these VLF and ELF transmitters were used during the Cold War to alarm deeply submerged nuclear submarines (SSBN). In this scenario, the submarine is only able to receive messages, e.g., emergency action messages (EAM) from the land station, but there is no way for a sub- Military Digital Underwater Communication UT 3000 Enables Digital, Analog Combo for Submarine Operations By Matthias Conrad • Sabrina Schreiber Typical actors in a digital underwater network scenario.

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