Channel-tolerant FH-MFSK acoustic signaling for undersea communications and networks

Citation
Md. Green et Ja. Rice, Channel-tolerant FH-MFSK acoustic signaling for undersea communications and networks, IEEE J OCEA, 25(1), 2000, pp. 28-39
Citations number
8
Categorie Soggetti
Civil Engineering
Journal title
IEEE JOURNAL OF OCEANIC ENGINEERING
ISSN journal
03649059 → ACNP
Volume
25
Issue
1
Year of publication
2000
Pages
28 - 39
Database
ISI
SICI code
0364-9059(200001)25:1<28:CFASFU>2.0.ZU;2-X
Abstract
Undersea acoustic channels can exhibit multipath propagation with impulse-r esponse duration and coherence time both of the order of tens to hundreds o f milliseconds, Signal reception is further impaired by the presence of tim e-varying nonwhite ambient-noise spectra having a dynamic range of 30 dB or more, Acoustic communication requires appropriate waveform design and asso ciated signal processing to accommodate these adverse transmission characte ristics while also providing desired performance features such as low-proba bility-of-detection (LPD) and multi-access networking, Adaptive-equalizatio n techniques provide good performance only for channels with stable multipa ths and high signal-to-noise ratios (SNR's) accommodating the signaling rat es needed to sample and compensate for rapid changes, An alternative approa ch is to design for robustness against channel fluctuations. This paper describes a channel-tolerant approach identified as "telesonar t ype-B signaling.'' The technique has been designed to accommodate network a rchitectures requiring multiple access to the channel while simultaneously providing covertness and energy efficiency. Specialized frequency-hopped M- ary frequency-shift-keg (FH-MFSK) waveforms are combined with related signa l processing, including nonlinear adaptive techniques to mitigate the effec ts of all types of interference. This effectively results in a channel that has uniformly distributed noise in both time and frequency, Powerful error -correction coding permits low SNR transmissions, Nonbinary, long-constrain t-length, convolutional coding and related sequential decoding is a classic al solution for difficult low-rate channels. The probability of bit errors below 10(-10) is obtainable, even in Rayleigh-faded channels near the compu tational cutoff rate, and the probability of failure to decode frames of da ta is extremely small. Both simulations and analyses of at-sea experiments demonstrate the perform ance of this noncoherent approach to reliable acoustic communications.