ABSTRACT
Channel estimation algorithms for Orthogonal Frequency Division Multiplexing (OFDM) employed in underwater acoustic (UWA) channels are investigated. Due to the slow propagation speed of acoustic waves, the compression and dilation effect on the time domain waveform warrant explicit time-varying Doppler scale estimation and compensation. In UWA channels, the residual Doppler error after compensation can be highly correlated due to very slow variation in Doppler scaling. This paper proposes a spectrally efficient and high performance frequency domain pilot symbol assisted modulation (PSAM) channel estimation scheme that fully exploits not only the time and frequency correlation of the channel, but also the correlation in the residual Doppler. The scheme is extended to Multiple-Input Multiple-Output (MIMO) systems which further improves spectral efficiency. Simulation results demonstrate that the performance of the proposed channel estimation schemes and it is observed that the BER performance increases when the correlation in the residual Doppler is also exploited.
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Index Terms
- On efficient channel estimation for underwater acoustic OFDM systems
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