Two-Dimensional Frequency-Domain Adaptive Multi-Branch Sparse Equalization for OTFS Underwater Acoustic Communication

In this letter, we propose a two-dimensional frequency-domain adaptive multi-branch sparse equalization (TFD-AMSE) algorithm for OTFS underwater acoustic communication. Compared with existing approaches, the proposed algorithm uses two-dimensional (TD) fast Fourier transform (FFT) to efficiently perform the high-complex TD linear convolution and correlation calculations required by the existent delay-Doppler (DD) domain algorithm in the frequency-domain. Moreover, to utilise the sparsity of the DD domain to improve convergence, the tap coefficient matrix is still updated in the DD domain. Therefore, the proposed TFD-AMSE not only has the advantage of low complexity, but also has a fast convergence speed. The simulation results confirmed that TFD-AMSE is feasible and has advantages over existing methods.