Yang, YangMa, LuSeet, Boon-Chong2025-11-062025-11-062025IEEE Wireless Communications Letters, ISSN: 2162-2337 (Print); 2162-2345 (Online), Institute of Electrical and Electronics Engineers (IEEE), 1-1. doi: 10.1109/lwc.2025.36242082162-23372162-2345http://hdl.handle.net/10292/20072Orthogonal Time Frequency Space (OTFS) modulation presents a promising approach for underwater acoustic (UWA) communication. This study proposes an iterative decision feedback equalizer based on optimal combining (OC) for UWA-OTFS systems, addressing challenges posed by the fullmatrix channel characteristics in the delay-Doppler domain. The proposed detector maximizes the signal-to-interference-plusnoise ratio of the combined signal. Furthermore, by introducing inter-Doppler interference depth, the OC detector dynamically constrains the number of combining terms. Simulation results demonstrate that the proposed detector effectively balances bit error rate performance with computational complexity.© 2025 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.0805 Distributed Computing0906 Electrical and Electronic Engineering1005 Communications Technologies4006 Communications engineering4009 Electronics, sensors and digital hardware4606 Distributed computing and systems softwareJournal ArticleOpenAccess10.1109/lwc.2025.3624208