Time reversal has aroused considerable interest incommunications applications as a means of partially compensatingfor the intersymbol interference introduced by the channel.This paper presents experimental results for a passive timereversal experiment conducted off the west coast of Portugalduring the MREA’2004 mission. A single acoustic projectorgenerated a 2/4-PSK stream at 200 and 400 baud, modulatedaround a carrier frequency of 3600 Hz. The signals were receivedat a range of about 2 Km from the source on a sparse verticalarray with 8 hydrophones. We examine several strategies fordemodulating the data, including equalization, time-reversal, andcombinations of both techniques. This work emphasizes the use oflow-complexity multichannel combining algorithms for trackingchannel variations prior to generating a passively focused signal.
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