Estimation and compensation of Doppler scale in UAC OFDM systems

Doppler effect causes loss of orthogonality in Orthogonal Frequency Division Multiplexing (OFDM), which in turn may severely degrade receiver performance. In high data rate underwater acoustic communication (UAC), the effect of Doppler shift varies considerably over OFDM frequency band. In the past and current UAC OFDM literature, the frequency domain Doppler shift is presented in terms of path dependent Doppler scale in time domain. This paper proposes and presents two algorithms to estimate Doppler scale induced by time variability of the channel. The performance of these estimation methods is evaluated under varying sampling period, varying number of channel taps, and varying channels.