Carrier Frequency Offset Compensation for OSDM in Underwater Acoustic Communications: Theory and Experiments Using a Vector MIMO Modem

Underwater acoustic communications suffer from time-varying multipath delay and different Doppler frequency offsets at different paths. To address these issues, a Carrier Frequency Offset Compensated Orthogonal Signal Division Multiplexing (CFO-C-OSDM) is proposed based on the basis expansion model for the time-varying channel. The CFO-C-OSDM method performs CFO compensation and channel estimation jointly, which manages a dynamic Doppler shift range characterized by a nonzero main CFO and residual CFOs caused by multipath propagation effectively. To validate the efficacy of this proposal, several rounds of emulations and experiments were conducted. The results show that the proposed CFO-C-OSDM proves to be more robust against doubly spread channels than existing techniques, such as D-OSDM and OSDM.