Title :
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.
fDate :
4/1/2006 12:00:00 AM
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;
Journal_Title :
Oceanic Engineering, IEEE Journal of
DOI :
10.1109/JOE.2006.876139
