Inside Unmanned Systems

JUN-JUL 2018

Inside Unmanned Systems provides actionable business intelligence to decision-makers and influencers operating within the global UAS community. Features include analysis of key technologies, policy/regulatory developments and new product design.

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MARINE COMMUNICATIONS 50   June/July 2018 unmanned systems inside Photo courtesy of George Sklivanitis. Divers could also use these networks to interact with underwater assets, Sklivanitis said. "Under water vehicles can act as vir- tual diver assistants and provide a range of services, such as diver monitoring, guiding, navigation and diver tracking," he said. Furthermore, military uses of such net- works could include "remote wireless con- trol of underwater vehicles and drones for surveillance, mine, ship, intruder or object detection," Sklivanitis added. A host of ap- plications for these networks may also exist for the offshore petroleum industry, seaport monitoring, commercial fisheries, pollution monitoring, oceanographic research and wildlife monitoring, he said. CHALLENGES However, to cover long distances underwater, lower frequencies of sound are needed. These can transmit far less data than the frequen- cies used for terrestrial radio communications, Sklivanitis said. In addition, underwater acoustic communi- cations links can suffer from a variety of other problems that hamper data transmission. For example, acoustic emitters and receivers are vulnerable to drifting with the waves, and the speed at which sound travels through water can vary with temperature, salinity and depth, all of which complicate the analysis of acoustic signals. Moreover, underwater acoustic waves are susceptible to scattering due to ref lection off the surface of the water, the bottom of the sea and objects suspended in the ocean. Given all these constraints, underwater acoustic channels have limited bandwidth open to them. Furthermore, they currently experience heavy traffic from both artificial acoustic systems such as sonar as well as natu- ral acoustic systems such as echolocating dol- phins and whales. COGNITIVE NETWORKS One strategy to make the most of that lim- ited ba ndw idth comes f rom technolog y known as cognitive radio. Cognitive radios are programmed to automatically detect available radio channels and negotiate with other cognitive radios to set their transmis- sion and reception settings to make the most of the wireless spectrum and avoid interfer- ence, Pados said. "Cognitive networking is new even for aerial communications, but the most critical applica- tion of cognitive networking may be underwa- ter, because the problem of creating effective links and networks is so much more difficult underwater than aerially," Pados said. The researchers hope to develop new cog- nitive underwater acoustic modems that can adapt to maximize all the available wireless An underwater modem

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