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This paper analysizes the effects of metal structures in near-field Magneto-Inductive (MI) communication systems, where the transmitter and/or receiver coils may be close to large metal structures that has high magnetic permeability and conductivity. EMCoStudio simulations show that the presence of metal structure help to increase the coupling magnitude if placed nearby the transmit and receive coils,...
The particular sensitivity of the Arctic to climate change is well established, and the significance to undersea operations can be dramatic. As part of the recent ICEX16 US Navy Exercise in the Beaufort Sea, MIT deployed an autonomous underwater vehicle with a towed hydrophone array below the ice cover for assessing the climate induced changes to the undersea ambient noise environment. The safe underwater...
One look at the absorption curve for light in water suggests that the best possible window for underwater optical transmission is at the blue-green end of the visible light spectrum, centered at roughly 450 nm for clear, deep water, and shifted more towards green for coastal water [1]. While this holds true for signal transmission in the optical communications channel, it is also true for the solar...
Recent interest in very high frequency (VHF, here defined as > 300kHz) underwater acoustic communications has motived a study of VHF noise sources in the littoral zone. The Littoral is a special environment for underwater ambient noise. Nearshore bathymetry induces wave breaking and wave-sediment interactions, both of which generate underwater noise, and a variety of marine organisms can radiate...
This paper describes industry efforts to develop an underwater acoustic communications standard for the offshore energy community. The Subsea Wireless Group (SWiG), an international oil and gas industry network comprising operators, installers, and technology companies, assessed a variety of potential use cases and possible routes to develop a common standard, culminating in the selection of the JANUS...
We describe an efficient method to discover the topology of underwater acoustic networks (UWANs). By knowing the network topology, nodes can determine destinations and routing possibilities for their packets, and schedule transmissions accordingly. To detect the network topology, an initial phase is employed. Our algorithm aims to reduce the time overhead of this initial phase while accurately discovering...
Watermark is a benchmark for testing, development, and comparison of physical-layer schemes for underwater acoustic communications. Its core is a replay channel simulator driven by at-sea measurements of the time-varying impulse response. Watermark is programmed in MATLAB and is initially provided with two (single-receiver) test channels with a run time of 30 minutes each. These channels were measured...
We propose a method for channel estimation in orthogonal frequency division multiplexing (OFDM) systems with an array of receiving elements. In contrast to traditional methods, which target the equivalent sample-spaced channel taps, this method targets the physical propagation paths whose delays are not restricted to the sample-spaced grid. The path delays are estimated jointly with the path gains...
Underwater Acoustic Networks (UANs) are widely used in various applications such as climate change monitoring, pollution control and tracking, tactical surveillance and offshore exploration. However, limited consideration is given to the security of such networks, despite the fact that the unique characteristics of UANs make these networks vulnerable to various malicious attacks. In this paper, we...
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