Wideband acoustic communications dispelling narrowband myths

Robust synchronisation is a fundamental requirement for any wideband acoustic communication system. It is shown that the temporal scaling influence of acoustic Doppler arising from platform motion and path length fluctuations between ray arrivals plays a significant role in high and low data rate acoustic system performance. Poor channel time coherence invariably leads to a complex synchronisation problem; an area which is often understated and misunderstood in wideband acoustic systems. It is shown that wideband systems can actively exploit the intrinsic phase stability of ray arrivals dispelling the narrowband myth that the acoustic channel cannot support phase coherent methods. This paper seeks to demonstrate the nature and impact of Doppler and Doppler variability on wideband acoustic communication's system performance and the benefits of robust open and closed loop Doppler compensation for both high data rate and low data rate modulation methods. Techniques for robust open loop synchronisation and Doppler estimation are presented and discussed.