Reliable Mobile Underwater Wireless Communication Using Wideband Chirp Signal

Acoustic communication between fast-moving underwater vehicles is difficult due to the fact the ratio of the vehicle speed to the sound speed many times exceeds its counterpart in the mobile radio channels. Hence, symbol synchronization, as important as carrier frequency identification, is critical for mobile underwater wireless communication. In this paper, we propose a reliable mobile underwater wireless communication using wideband chirp signals and a novel symbol self-synchronization method. The use of chirp signals takes advantage of the low Doppler sensitivity as well as their good autocorrelation properties. Several lake experiments and computer simulations have been carried out to verify the proposed system over different distances. Phenomenon of synchronization error accumulation caused by Doppler shift is presented. Our works show that the developed system is able to provide a reliable wireless link between fast-moving underwater vehicles. The achieved data rate is 300 bps with uncoded bit error rate around 10^-3-10^-5 when the relative speed is as large as 18 m/s (36 knots).