Bit-error rate based Doppler estimation for shallow water acoustic OFDM communication

Abstract

Orthogonal frequency division multiplexing (OFDM) has drawn extensive attention in the field of underwater acoustic (UWA) communication due to its advantages of high transmission rate and high spectrum efficiency. Unfortunately, the practical application of OFDM in UWA communication is subject to severe multi-path as well as Doppler sensitivity. To overcome the impact of Doppler, generally the value of Doppler is estimated by searching the best correlation with the standard copy in time or frequency domain, to enable Doppler compensation via the resampling. However, it has been recognized that, at the presence of diffuse or time varying multi-path, the Doppler estimated by searching signal-level correlation may cause significant mismatch and thus deteriorate the demodulation. The reason is that, while the Doppler is searched in terms of signal-level correlation function, the purpose of the demodulation is to achieve the minimum bit error rate (MBER) at bit-level. In this paper, a Doppler estimation method based on BER search is proposed to transform the signal-level Doppler estimation into a bit-level one. Finally, numerical simulation and sea trial experiments under different Doppler scenarios are performed to verify the effectiveness of the proposed Doppler estimation method.