Direct Adaptive Equalization with CFO Pre-compensation for Single-Carrier Underwater Acoustic Communications

For single-carrier underwater acoustic (UWA) communications, phase correction is critical to the symbol detection on the receiver side. Existing receiver schemes either run a phase-locked loop (PLL) in parallel to an equalizer or perform a subsequent phase correction next to the equalizer. Both parallel and subsequent phase correction methods suffer limitations in practical use. In this work, we propose to introduce a carrier frequency offset (CFO) pre-compensation module to existing receivers, with the CFO estimated with an m-sequence. The so-obtained receiver scheme was tested by real data collected in an at-sea UWA communication trial. Experimental results verified the extra performance gain brought by the CFO pre-compensation. In the particular scenario that the CFO is the main source of the phase rotation, conventional CFO correction modules like the PLL can be dropped in light of the inclusion of the CFO pre-compensation.