Prof. Xiao Han

Keynote Speech Title: Under-ice acoustic data transmissions: simulations and experimental results

Speaker's Bio:
Xiao Han is currently an associate Professor with the College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin, China. He received the Ph.D. degree from Harbin Engineering University, China, in 2016. From June 2018 to September 2018, he joined the ninth Xuelong Arctic expedition. He is the author of numerous research articles published in related international conference proceedings and journals and is the holder of nearly ten patents. His research interests include underwater acoustic signal propagation, ocean acoustics, digital communication theory acoustic communication in under-ice environment, and embedded systems. Most of his work focuses on channel estimation, tracking and equalization in time domain based on passive time reversal and decision feedback equalizer in underwater environment. Now his research is mainly concentrated in under-ice acoustics communication in shallow water. .

Keynote Speech Abstract:
With the rapid development of various applications in the Arctic recent years, under-ice acoustic (UIA) research is becoming a hot topic. The thick ice cover in Arctic regions prevents underwater platforms (i.e. underwater unmanned vehicles, UUVs) from communicating with the satellites, which makes the acoustic become the only means to realize robust UI data transmissions, targets detection and navigation. The acoustic propagation under-ice water interference is very different from that under air-water interference.
As most of the sound velocity profiles (SVPs) have positive gradients in UI environment, the acoustic rays will bend to the ice cover during propagation. Furthermore, the reflection coefficients of ice are much smaller than that of air for acoustic signal, so the transmission loss is much greater in UI environment. In this paper, computer simulations are firstly conducted based on two typical SVPs measured in Arctic regions. Then this paper discusses several problems that need to be solved in order to realize robust UI data transmissions.
The first problem is Doppler effect. The movement of ice cover especially in floating ice region can make the ice-water cover keep changing, just like oceans waves, introducing Doppler effect to those acoustic rays reflected by the ice-water interference. The second problem is sparse channel impulse responses (CIRs) estimation in special noise environment. Due to the unique acoustic propagation features in UI environment, only few acoustic rays can arrive at the receiver, making the CIRs show sparse features. The special noise is impulsive noise which is introduced by ice cracking, ice breaking and ice melting. The paper proposes corresponding methods to solve the above problems and will show the theory, simulation results and experiments results.