A robust digital communication system for doubly-spread underwater acoustic channels

The performance of underwater acoustic communication systems depends on the timeliness and accuracy of the estimate of the time-varying channel characteristics and the use of an effective algorithm to compensate for the distortion on the received signal caused by the channel. In a previous paper, the authors proposed estimating the characteristics of the doubly-spread underwater channel using a pilot tone in conjunction with a broadband PN pilot sequence and the channel estimate was optimised using an evolutionary algorithm. However, because of frequency selective fading due to multipath propagation, the pilot tone can be severely attenuated, causing unreliable channel estimates. To overcome this, diversity techniques are used here, wherein additional pilot tones are suitably placed to mitigate the frequency selective fading. As a result, both the channel estimates and the overall system performance are more reliable even for the more severe channel being considered here.

[1]  T.C. Yang,et al.  Performance limitations of joint adaptive channel equalizer and phase locking loop in random oceans: initial test with data , 2000, OCEANS 2000 MTS/IEEE Conference and Exhibition. Conference Proceedings (Cat. No.00CH37158).

[2]  R. F. Ormondroyd,et al.  An improved digital communication system for doubly-spread underwater acoustic channels using evolutionary algorithms , 2003, Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492).

[3]  W. Hodgkiss,et al.  Effects of tidally driven temperature fluctuations on shallow-water acoustic communications at 18 kHz , 2000, IEEE Journal of Oceanic Engineering.

[4]  L. Bjorno,et al.  A simulation tool for high data-rate acoustic communication in a shallow-water, time-varying channel , 1996 .

[5]  Milica Stojanovic,et al.  Recent advances in high-speed underwater acoustic communications , 1996 .

[6]  R. F. Ormondroyd,et al.  Combined differential Doppler and time delay compensation for an underwater acoustic communication system , 2002, OCEANS '02 MTS/IEEE.

[7]  R. Storn,et al.  On the usage of differential evolution for function optimization , 1996, Proceedings of North American Fuzzy Information Processing.

[8]  R. Galvin,et al.  A stochastic underwater acoustic channel model , 1996, OCEANS 96 MTS/IEEE Conference Proceedings. The Coastal Ocean - Prospects for the 21st Century.

[9]  A.B. Baggeroer,et al.  The state of the art in underwater acoustic telemetry , 2000, IEEE Journal of Oceanic Engineering.

[10]  R. F. Ormondroyd,et al.  A phase estimator for complex signals using evolutionary algorithms , 2003, The 3rd International Workshop on Scientific Use of Submarine Cables and Related Technologies, 2003..

[11]  A. Baggeroer,et al.  Communication over Doppler spread channels. Part I: Channel and receiver presentation , 2000, IEEE Journal of Oceanic Engineering.