A chaotic spread spectrum system for underwater acoustic communication

The work is supported in part by NSFC (Grant no. 61172070), IRT of Shaanxi Province (2013KCT-04), EPSRC (Grant no.Ep/1032606/1).Peer reviewedPostprin

Advanced data communication techniques for sub-sea applications

This thesis details research carried out in the through-water data communication field. An overview of the phenomena that prohibit acoustic communication in long-range shallow-water channels is constructed. Background research found that robust communications has not been achieved using single receiver reception in this environment. This work investigates the modulation technique itself and aims to improve on existing schemes (that have been applied to this environment). This is achieved with innovative techniques, based on multiple-frequency-shift-keying (MFSK) and space-frequency-shift-keying (SFSK). A number of industrial specified restrictions are placed on this work, including bandwidth restriction. Novel ways of intrinsically transmitting synchronisation information are therefore implemented. The development of appropriate systems is covered with general and platform specific implementation strategies being covered. A single modulation scheme (the three-chip four-frequency-shift-keying, 3C4FSK, scheme) has been put forward for consideration in any future research. Practical lab-based tests and the mathematical analysis is detailed. Conclusions recommend further funding of long-range shallow sea-water trails of the 3C4FSK scheme and for the industrial scope of this work to allow investigation into multiple receiver systems that allow spatial processing of the signal as these schemes have been shown lately to have potential in long-range channels

Fiber-optic push-pull sensor systems

Fiber-optic push-pull sensors are those which exploit the intrinsically differential nature of an interferometer with concommitant benefits in common-mode rejection of undesired effects. Several fiber-optic accelerometer and hydrophone designs are described. Additionally, the recent development at the Naval Postgraduate School of a passive low-cost interferometric signal demodulator permits the development of economical fiber-optic sensor systems

Multiple-Resampling Receiver Design for OFDM Over Doppler-Distorted Underwater Acoustic Channels

Cataloged from PDF version of article.In this paper, we focus on orthogonal frequency-divisionmultiplexing (OFDM) receiver designs for underwater acoustic (UWA) channels with user- and/or path-specific Doppler scaling distortions. The scenario is motivated by the cooperative communications framework, where distributed transmitter/receiver pairs may experience significantly different Doppler distortions, as well as by the single-user scenarios, where distinct Doppler scaling factors may exist among different propagation paths. The conventional approach of front–end resampling that corrects for common Doppler scalingmay not be appropriatein such scenarios, rendering a post-fast-Fourier-transform (FFT) signal that is contaminated by user- and/or path-specific intercarrier interference. To counteract this problem, we propose a family of front–end receiver structures thatutilizemultiple-resampling (MR)branches,eachmatched to the Doppler scaling factor of a particular user and/or path. Following resampling, FFT modules transform the Doppler-compensated signals into the frequency domain for further processing through linear or nonlinear detection schemes. As part of the overall receiver structure, a gradient–descent approachis also proposed to refine the channel estimates obtained by standard sparse channel estimators. The effectiveness and robustness of the proposed receivers are demonstrated via simulations, as well as emulations based on real data collected during the 2010 Mobile Acoustic Communications Experiment (MACE10, Martha’s Vineyard, MA) and the 2008 Kauai Acomms MURI (KAM08, Kauai, HI) experiment

Chirp Slope Keying for Underwater Communications

This paper presents a novel broadband modulation method for digital underwater communications: Chirp Slope Keying (CSK). In its simplest form, the binary information modulates the slope of a linear chirp, with up-chirps representing ones and down-chirps representing zeros. Performance evaluation in the form of probability of error vs. SNR show that the system performs as expected for AWGN environments and very well for more realistic models for underwater acoustical communications, such as the Raylegih channel with Doppler, delays, phase offset, and multipath

From Radio to In-Pipe Acoustic Communication for Smart Water Networks in Urban Environments: Design Challenges and Future Trends

The smart management of water resources is an increasingly important topic in today’s society. In this context, the paradigm of Smart Water Grids (SWGs) aims at a constant monitoring through a network of smart nodes deployed over the water distribution infrastructure. This facilitates a continuous assessment of water quality and the state of health of the pipeline infrastructure, enabling early detection of leaks and water contamination. Acoustic-wave-based technology has arisen as a viable communication technique among the nodes of the network. Such technology can be suitable for replacing traditional wireless networks in SWGs, as the acoustic channel is intrinsically embedded in the water supply network. However, the fluid-filled pipe is one of the most challenging media for data communication. Existing works proposing in-pipe acoustic communication systems are romising, but a comparison between the different implementations and their performance has not yet been reported. This paper reviews existing works dealing with acoustic-based ommunication networks in real large-scale urban water supply networks. For this purpose, an overview of the characteristics, trends and design challenges of existing works is provided in he present work as a guideline for future research