A. Silva and S.M. Jesus asilva@ualg.pt
and sjesus@ualg.pt
SiPLAB-FCT, Universidade do Algarve
Faro, Portugal
Comments: download pdf file .
Ref.: Proc. IEEE/MTS Oceans'02,
(ISBN:0-7803-7535-1), p.2416-2421, Biloxi, USA, Ocober 2002.
Abstract : Field experiments using Time-Reversal Mirror(TRM)
techniques
have shown that the underwater acoustic channel presents a longer
stability
than it was previously anticipated. Applying such techniques to
underwater
communications requires that, either the emitted signals are previously
filtered
by time-reversed replicas of the channel impulse response or that a
probe-signal
should be transmitted ahead of the data-signal for post channel
filtering.
In the former case, the time-reversed filtered message is expected to
be undone
by the actual acoustic channel between the array and the receiver,
while
in the later, the undoing of the multipath is performed electronically
inside
the computer and is therefore termed as virtual Time Reversal
Mirror(vTRM).
The main issues being addressed in recent literature deal with channel
stability,
focus width and the required array aperture for obtaining reasonable
temporal
and/or spatial focusing. This paper focus essentially in two practical
aspects,
generally not addressed: one is to demonstrate the potential
application of
the vTRM approach to undo the severe intersymbol interference in a real
variable
geometry channel scenario and, the other, is the importance of
optimization
of the probe-signal time window length in a real application.
ACKNOWLEDGMENT: this work was partially supported under projects INFANTE, INTIMATE from FCT (Portugal) and LOCAPASS (FUP/MDN).