Improvement of Time-Reversal Communications Using Adaptive Channel Equalizers

Author

Song, H.C. ; Hodgkiss, W.S. ; Kuperman, W.A. ; Stevenson, M. ; Akal, T.

Author_Institution

Marine Phys. Lab., Scripps Instn. of Oceanogr.

Volume

31

Issue

2

fYear

2006

fDate

4/1/2006 12:00:00 AM

Firstpage

487

Lastpage

496

Abstract

The spatial and temporal focusing properties of time-reversal methods can be exploited for undersea acoustic communications. Spatial focusing mitigates channel fading and produces a high signal-to-noise ratio (SNR) at the intended receivers along with a low probability of interception elsewhere. While temporal focusing (compression) reduces significantly intersymbol interference (ISI), there always is some residual ISI depending upon the number of transmitters, their spatial distribution (spatial diversity), and the complexity of the channel. Moreover, a slight change in the environment over the two-way propagation interval introduces additional ISI. Using multilevel quadrature amplitude modulation (M-QAM) in shallow water, we demonstrate that the performance of time-reversal communications can be improved significantly by cascading the received time series with an adaptive channel equalizer to remove the residual ISI

Keywords

adaptive equalisers; diversity reception; fading channels; intersymbol interference; quadrature amplitude modulation; underwater acoustic communication; adaptive channel equalizers; channel fading; intersymbol interference; multilevel quadrature amplitude modulation; shallow water; spatial distribution; spatial diversity; temporal focusing; time-reversal communications; undersea acoustic communications; Base stations; Decision feedback equalizers; Intersymbol interference; MIMO; Phased arrays; Quadrature amplitude modulation; Transmission line measurements; Transmitters; Underwater acoustics; Underwater communication; Adaptive equalizer; billboard array; decision-feedback equalizer (DFE); decision-feedback phase-locked loop (DFPLL); fractionally spaced equalizer (FSE); intersymbol interference (ISI); multilevel quadrature amplitude modulation (M-QAM); multiple-input–multiple-output (MIMO); time-reversal communication;

fLanguage

English

Journal_Title

Oceanic Engineering, IEEE Journal of

Publisher

ieee

ISSN

0364-9059

Type

jour

DOI

10.1109/JOE.2006.876139

Filename

1707996