Basin-scale time reversal communications.
During November 1994, broadband acoustic signals were transmitted from a 75-Hz source to a 20-element, 700-m vertical array at approximately 3250 km range in the eastern North Pacific Ocean as part of the acoustic engineering test (AET) of the acoustic thermometry of ocean climate program [Worcester et al., J. Acoust. Soc. Am. 105, 3185-3201 (1999)]. The AET tomography signal can be treated as a binary-phase shift-keying communication signal with an information rate of 37.5 bitss. With the multipath arrivals spanning 5-8 sec, these data represent an extreme case of intersymbol interference. The AET array data are processed using time reversal combined with frequent channel updates to accommodate channel variations over the 20-min long reception, followed by a single channel decision-feedback equalizer. The almost error-free performance using all 20 array elements demonstrates the feasibility of time reversal communications at basin scale. Further, comparable performance of single receive element communications integrating over multiple transmissions indicates that the ocean provided temporal diversity that is as effective as the spatial diversity provided by the array.
Song
H C
HC
Marine Physical Laboratory, Scripps Institution of Oceanography, La Jolla, California 92093-0238, USA. hcsong@mpl.ucsd.edu
Kuperman
W A
WA
Hodgkiss
W S
WS
D000162:Acoustics; D003142:Communication; D003657:Decision Making; D004738:Engineering; D005246:Feedback; D006801:Humans; D009792:Oceans and Seas; D013997:Time Factors