The Doppler effect severely degrades the orthogonality of orthogonal frequency division multiplexing (OFDM) systems, and is a severe problem in the underwater acoustic (UWA) communications, leading to nonuniform Doppler shifts for all subcarriers. In order to alleviate Doppler effect, resampling technique by oversized fast Fourier transform (FFT) can achieve fast and accurate resampling in frequency domain. Nevertheless, the accuracy of this conventional FFT based approach depends on the FFT size, which in turn increases receiver complexity. In order to overcome this problem, the Doppler compensation model in frequency domain is simplified by Taylor series expansion in this letter. Based on the simplified model, we propose the Doppler compensation algorithm by using FFT and interpolation to achieve higher compensation accuracy. Simulation results demonstrate that the proposed algorithm shows very similar bit error rate (BER) performance with that of Chirp Z-transform (CZT) based method. However, the complexity of our proposed algorithm is about half of CZT based method. Further, our proposed low-complexity Doppler compensation algorithm can also be applied to the sampling frequency offset (SFO) correction in terrestrial OFDM communication systems.

中文翻译：

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具有非均匀多普勒频移的水下声学 OFDM 系统的低复杂度多普勒补偿算法

多普勒效应严重降低了正交频分复用 (OFDM) 系统的正交性，并且是水声 (UWA) 通信中的一个严重问题，导致所有子载波的多普勒频移不均匀。为了减轻多普勒效应，采用超大快速傅立叶变换（FFT）的重采样技术可以在频域实现快速准确的重采样。然而，这种传统的基于 FFT 的方法的准确性取决于 FFT 大小，这反过来增加了接收器的复杂性。为了克服这个问题，本文通过泰勒级数展开来简化频域中的多普勒补偿模型。在简化模型的基础上，我们提出了采用FFT和插值的多普勒补偿算法，以达到更高的补偿精度。仿真结果表明，所提出的算法显示出与基于 Chirp Z 变换 (CZT) 的方法非常相似的误码率 (BER) 性能。然而，我们提出的算法的复杂度大约是基于 CZT 的方法的一半。此外，我们提出的低复杂度多普勒补偿算法也可以应用于地面 OFDM 通信系统中的采样频率偏移 (SFO) 校正。