High-speed noncoherent underwater acoustic communication using permutation alphabets and sliding hypothesis-tree decoding

Abstract

A framework for joint synchronization and decoding is presented, named sliding hypothesis-tree decoding (SHDT), which targets communication applications in adverse underwater acoustic channels. The framework is exemplified by constructing a robust noncoherent link with spectral efficiency 0.149–0.222 bit/s/Hz using Polar coding and super permutation frequency shift keying. The link method is evaluated with randomized time-Doppler shifts through replay simulation of recorded UWA channels, where the five benchmark channels of the public benchmark Watermark and two channels from the Baltic Sea are used; these simulations show that a low frame error rate is achievable in all seven channels. The constructed link method is further evaluated in an adverse acoustic horizontal shallow-water channel using a high-mobility setup; the link method is able to perform synchronization, and a decoder performance similar to the replay simulations is observed. SHDT allows the construction of link methods with a performance limited by the information decoding rather than the time-Doppler synchronization, making it applicable to communication with lower-rate methods in non–line-of-sight scenarios.