OFDM for underwater acoustic communications: Adaptive synchronization and sparse channel estimation

A phase synchronization method, which provides non-uniform frequency offset compensation needed for wideband OFDM, is coupled with low-complexity channel estimation in the time domain. Sparsing of the channel impulse response leads to an improved performance, while adaptive synchronization supports decision-directed operation and yields low overhead. System performance is demonstrated using experimental data transmitted over a 1 km shallow water channel in the 19 kHz - 31 kHz band.