Time Diversity Passive Time Reversal for Underwater Acoustic Communication

Underwater acoustic signal propagation is greatly affected by source-receiver motion, surface variations, and water column variabilities, which make the underwater acoustic communications very challenging. A passive time reversal (pTR) system is widely used for underwater communication systems due to its focusing property, which minimizes the time spreading of the underwater channel. The performance of the pTR system degrades when the underwater channel varies rapidly. During the experiment in TrondheimFjord on September 22, 2016, some environmental variations are observed which resulted in channel variations and the performance of the pTR system degraded. A time diversity pTR system is proposed and it uses the time diversity of the channel to compensate for the channel variations. The proposed system is tested at two receiver positions and it provides 2-3-dB gain in terms of mean square error in the presence of rapid channel variations.