Advances in Receiver Technologies for Single-Carrier Underwater Acoustic Communications

Single-carrier underwater acoustic (UWA) communication offers several practical advantages, including a low peak-to-average power ratio, power-amplifier-friendly operation, strong tolerance to transducer nonlinearities, and relatively straightforward engineering implementation, making it attractive for shipborne equipment, submersibles, autonomous underwater vehicles, underwater sensor networks, and deep-sea exploration systems. This paper reviews single-carrier UWA receiver technologies from the perspective of the coupling between channel modeling and receiver design. Within a unified broadband multipath model and common Doppler-compensation framework, four progressively refined post-resampling channel models are examined: the linear time-invariant tapped-delay-line model, the common residual carrier-frequency-offset model, the nonuniform Doppler model, and the broadband delay-scale model. Their applicability is further related to the development and modeling foundations of decision-feedback equalization (DFE), frequency-domain equalization, Turbo iterative equalization, and receivers based on vector approximate message passing (VAMP), generalized approximate message passing (GAMP), parametric bilinear generalized approximate message passing (PBiGAMP), and robust joint estimation and detection. Receiver technologies, representative domestic and international lake and sea trials, and major challenges under impulsive noise, long delay spreads in deep-sea channels, and multiple-input multiple-output (MIMO) transmission are further summarized. Future directions, including adaptive channel modeling, low-complexity joint inference, integration of physics-based priors with data-driven methods, and standardized channel datasets, are then discussed. The analysis shows that single-carrier UWA receiver design is evolving from isolated equalizer optimization toward coordinated channel modeling, parameter estimation, Doppler compensation, soft-information exchange, and decoder feedback. As measured channel libraries and open datasets continue to mature, performance evaluation is also shifting from scenario-specific demonstrations toward cross-scenario, reproducible benchmarking.