Patent ID: 7447117
Filing Date: 2008-11-04
Classification: H04B

Abstract:
1. An underwater communications system, comprising: an antenna array including a plurality of sensors for receiving sound transmissions; a sound transmission source for transmitting communication packets, said packets containing a Doppler-sensitive probe signal followed by a gap, followed by a sequence of symbols beginning with training symbols followed by message symbols, wherein said probe signal can be a stand alone signal or part of said training sequence; a receiver including a processor, said processor programmed (i) for receiving and detecting said Doppler-sensitive probe signal or said training sequence for each of a plurality of receiver channels; (ii) for estimating the channel impulse response function using a matched filter based on a set of Doppler-shifted probe signal waveforms within an anticipated range of Doppler shift for each of a plurality of receiver channels, thereby determining a broadband ambiguity surface as a function of Doppler shift and multipath delay time for each of a plurality of receiver channels, and determining the Doppler-shift from the peak position of the ambiguity surface and a Doppler-corrected impulse response function for each of a plurality of receiver channels; (iii) for correlating the received signal after the probe signal with the Doppler-corrected impulse response function for each of a plurality of receiver channels to yield a plurality of processed channel outputs, and (iv) for summing the channel outputs to yield a common receiver output; and a Decision Feedback Equalizer (DFE) applied to said common receiver output to adaptively correct for the inter-symbol interference and retrieve the transmitted communication message.