Time-reversed communication over Doppler-spread underwater channels

Gomes, Camila Couto; Barroso,

doi:10.1109/icassp.2002.1005280

Cited by 3 publications

(5 citation statements)

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“…These groups have been engaged in experimental work, emphasizing low-complexity processing using TR only. In parallel, analytical work addressed the use of adaptive channel estimation and low complexity equalization in conjuction with TR [4]. The common goal of these efforts was to eliminate ISI by use of TR.…”

Section: Introductionmentioning

confidence: 99%

Spatio-Temporal Focusing for Elimination of Multipath Effects in High Rate Acoustic Communications

Stojanovic¹

2004

AIP Conference Proceedings

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Abstract. High rate underwater communications have traditionally relied on equalization methods to overcome the intersymbol interference (ISI) caused by multipath propagation. An alternative technique has emerged in the form of time-reversal, which comes at virtually no cost in computational complexity, but sacrifices the data rate and relies on large arrays to reduce ISI. In this paperer, optimal multipath suppression using spatio-temporal processing is addressed analytically. A communication link between a single element and an array is considered in several scenarios: uplink and downlink transmission, with and without channel state information and varying implementation complexity. Transmit/receive techniques are designed which simultaneously maximize the data detection SNR and minimize the residual ISI, while maintaining maximal data rate in a given bandwidth and satisfying a constraint on transmitted energy. The performance of various techniques is compared on a shallow water channel operating in the 15 kHz band. Results demonstrate benefits of optimal focusing whose performance is not conditioned on the array size.

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Section: Introductionmentioning

confidence: 99%

Spatio-Temporal Focusing for Elimination of Multipath Effects in High Rate Acoustic Communications

Stojanovic¹

2004

AIP Conference Proceedings

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“…Acoustic propagation was simulated using a Gaussian beam ray tracer with sound-speed profile shown in Figure 1a, constant bottom reflection coefficient αB = 0.6, and surface reflection modeled as a deterministic angle-dependent coefficient equal to the average specular component for a surface RMS roughness of 0.4 m [7]. The source velocity vector was chosen as v = Figures 1b-c show two projections of the depth-delay-Doppler spread function, calculated according to (5), (10) and (11), and discretized with steps ∆τ = T b /4 and ∆ν = 0.1 Hz. These projections correspond to l |Um(k, l)| 2 and m |Um(k, l)| 2 , respectively.…”

Section: Simulation Resultsmentioning

confidence: 99%

“…It is assumed that the delay between the forward and time-reversed transmissions is sufficiently small so that the source displacement during that interval will be negligible, and the multipath structure of the channel can be regarded as constant [5]. Fluctuations in the phase of gm(t) due to uniform motion will simply be lumped together with actual Doppler shifts for estimation/compensation purposes, as described below.…”

Section: Coherent Communication In the Presence Of Dopplermentioning

confidence: 99%

“…Fluctuations in the phase of gm(t) due to uniform motion will simply be lumped together with actual Doppler shifts for estimation/compensation purposes, as described below. The equivalent Doppler-distorted signal transmitted over a single path in response to the nominal passband waveformx(t) = Re{x(t)e jωct } is [5] …”

Section: Coherent Communication In the Presence Of Dopplermentioning

confidence: 99%

“…This allows automatic compensation of differential Doppler at the receiver during the time-reversed transmission even if, as would most likely happen in a real situation, it is not following the time-reversed path. This simple and robust approach can be combined with other variants of time reversal, such as spatial modulation through wavefront segmentation [2,5].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Doppler compensation in underwater channels using time-reversal arrays

Gomes

Barroso

2003 IEEE International Conference on Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03).

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This work addresses the problem of compensating for differential Doppler shifts due to source motion in a time-reversal mirror. Time reversal is a feedback wave focusing technique that can be used in poorly-characterized media, and is quite appealing in bidirectional underwater communications as it allows multipath to be transparently canceled in highly dispersive channels. Under simplifying assumptions, it is shown that time-reversed focusing occurs even when the source moves uniformly, although this induces fluctuations in the envelope of the regenerated signal due to differential Doppler. The proposed technique for Doppler compensation builds on the representation of time-varying pulse shapes using delay-Doppler spread functions. By inverting these functions in both delay and Doppler at each transducer, the mirror is able to project signals that converge on the source and are devoid of Doppler shifts when observed in its moving reference frame.

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Time Reversal precoder: An efficient tool for more reliable underwater acoustic communication

Banerjee

Agrawal

2012

2012 Oceans - Yeosu

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Time-reversed communication over Doppler-spread underwater channels

Cited by 3 publications

References 0 publications

Spatio-Temporal Focusing for Elimination of Multipath Effects in High Rate Acoustic Communications

Spatio-Temporal Focusing for Elimination of Multipath Effects in High Rate Acoustic Communications

Doppler compensation in underwater channels using time-reversal arrays

Time Reversal precoder: An efficient tool for more reliable underwater acoustic communication

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