A Low Complexity Turbo MMSE Equalization Method for OTFS Underwater Acoustic Communications

This paper provides a low complexity turbo iterative equalization algorithm for OTFS underwater acoustic communication systems. The method defines the influence range of symbols in the delay-doppler domain, performs symbol-by-symbol MMSE equalization and LDPC soft decoding. By exchanging soft information between equalizer and decoder, turbo iteration equalization is realized. It uses iterative structure to further enhance the performance by using the information of the previous iteration. In addition, based on block iterative matrix inversion, the direct inversion of large matrices is avoided. Simulation results show that the proposed method can significantly reduce the computational complexity while losing less performance.