The effect of diffused arrivals on the performance of phase coherent underwater acoustic communications

• Published in: The Journal of the Acoustical Society of America 2001-05, Vol.109 (5_Supplement), p.2451-2451
• Main Authors: Yang, T. C., Yoo, Kwang, Al-Kurd, Azmi
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4744689

The delayed multipath arrivals cause intersymbol interference (ISI) in underwater acoustic communications, which can sometimes extend over tens to hundreds of symbols. The performance of the decision feedback equalizer (DFE) requires a reasonably accurate estimate of the number of tap coefficients as too few taps fail to remove the ISI and too many taps increases the mean square error (the processor noise). An initial estimate of the channel impulse response is often used to determine the number and positions of the taps. This decision is clear-cut for well-defined (usually high-amplitude) arrivals but ambiguous for diffused arrivals that are weak and undistinguished. It should be noted that diffused arrivals can be a significant component of the signal, resulting usually from sound scattering from fluctuating surface/bottom and random media. Its amplitude and complexity are compounded and enhanced by platform motion. This work illustrates the effect of diffused arrivals on the performance of the equalizer by introducing diffused arrivals in a simple model and proceeds to show the effect of wind speed on the bit error rate in realistic ocean channels. [Work supported by ONR.]