Effects of internal waves on acoustic coherent communications during SW06

During a 12 h period in the Shallow Water 2006 experiment, concurrent environmental observations and acoustic measurements were made to study internal wave effects on coherent underwater acoustic communications. Binary phase shift keying signals at carrier frequencies 813 Hz and 1627 Hz which propagated over a 19.8 km source-receiver range during the 12 h period are processed. This is done using time reversal multi-channel combining followed by a decision feedback equalizer with continuous channel updates prior to time reversal combining. The communications performance in terms of output signal-to-noise ratio exhibits significant change (more than 5 dB) due to the passage of internal waves through the acoustic track. The effects of the internal waves also show a frequency dependency.