JASA logo

Sustained underwater acoustic communications with environmental-based time-reversal

L.P. Maia, lussac.maia(to)marinha.mil.br
Instituto de Estudos do Mar Almirante Paulo Moreira, Rua Kioto, 253, Arraial do Cabo,
Rio de Janeiro 28930-000, Brazil
A. Silva, asilva(at)ualg.pt
S.M. Jesus sjesus(at)ualg.pt
LARSys, University of Algarve,
Campus de Gambelas, PT-8005-139 Faro, Portugal.

Comments: download (pdf).
Ref.: Journal of the Acoustical Society of America, Express Letters, Vol.144(4), EL262-EL267, October 2018.

The usage of time-reversal in underwater communications relies on array channel matched-filtering, coherent channel replica alignment and summation. Traditionally, replicas are channel responses to probe signals received at a previous time. These are noisy and subject to distortion due to channel variability. This paper offers an alternative where noisy and potentially distorted channel replicas are replaced by noise-free and time-updated replicas generated by a numerical model constrained on previously data-identified environmental parameters. The method is applied on real data, where a quadrature phase shift key modulated signal on a 25.6 kHz carrier at 4 kbit/s was transmitted in a shallow water area over a distance of approximately 900 m. Sustained analysis without supervision shows that the proposed method may attain a mean square error gain up to 5.4 dB when compared to traditional time-reversal.