Bidirectional Joint Iterative l₁-RLS Estimation for Single-Carrier Underwater Acoustic Communication: Algorithm and Undersea Experimental Results

Enhancing the performance of single-carrier underwater acoustic (UWA) communication systems necessitates the development of accurate channel estimation techniques within the receiver. Among various approaches, the recursive least squares (RLS)-based channel estimation method has been extensively employed due to its rapid convergence and robust tracking capabilities. Over time, numerous enhancements have been incorporated into the RLS framework to further improve channel estimation performance for UWA systems. In this paper, a novel Bidirectional Joint Iterative l₁-RLS (Bi-Ji-l₁-RLS) algorithm is proposed to optimize channel estimation for single-carrier UWA communication systems. The proposed algorithm exploits bidirectional diversity and the inherent sparsity of UWA channels to achieve performance improvements. A comprehensive transient analysis is developed, jointly considering the bidirectional estimation mechanism and the l₁-norm constraint, which elucidates the operational behaviors and confirms the advantages of the Bi-Ji-l₁-RLS algorithm over the conventional l₁-RLS approaches. Simulation results further validate the theoretical analysis, demonstrating enhanced estimation accuracy. Moreover, experimental results obtained from undersea trials substantiate the practical effectiveness of the proposed algorithm, highlighting its moderate superiority over existing techniques in real-world UWA communication scenarios. Specifically, the proposed algorithm achieves the minimum bit error rate (BER) of 0.0832% and the maximum output signal-to-noise ratio (OSNR) of 12.6024 dB.