Abstract
Underwater acoustic (UWA) channels are wideband in nature due to the small ratio of the carrier frequency to the signal bandwidth, and introduce frequency-dependent Doppler shift. The resulting Doppler effect translates each frequency component by a different Doppler amount. Therefore, the conventional techniques for Doppler shift estimation in wireless narrowband communication channels cannot be applied to the UWA environments. In this thesis, we consider a UWA environment having a common Doppler scaling factor on all propagation paths and propose a preamble-assisted Doppler scaling factor estimation scheme for ZP-OFDM (zero padding orthogonal frequency division multiplexing) systems. The Doppler scaling factor is estimated based on the phase difference of the received signals on the same subcarrier in two consecutive OFDM preambles. In the simulations, we show that the proposed scheme outperforms the matched-filter and multiple correlator methods in terms of mean square error (MSE).