The main OFDM drawbacks are Carrier Frequency Offset (CFO) and large Peak-to-Average Power Ratio (PAPR), which both degrade the Bit Error Rate (BER). Specifically, we consider here clipping or any other PAPR reduction method sufficient to prevent the nonlinear high-power amplifier from generating errors. Moreover, in small cells, the signal-to-noise ratio is large, while the small time dispersion allows the OFDM symbol cyclic prefix to prevent intersymbol interference. This retains the CFO to solely determine the BER and vice versa, enabling indirect estimation of CFO-induced phase distortion by simple BER testing. However, a particular problem is measuring very low BER values (generated by alike residual CFO), which could last a long time in order to acquire statistically enough errors. The test time can be drastically reduced if the noise margin is reduced in a controllable way, by adding the interfering signal to each subcarrier at the receiver. This approach is shown to enable efficient and accurate short-term BER (and so CFO phase error) testing.

中文翻译：

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降低噪声余量的基于BER的实用残余OFDM CFO估计

OFDM的主要缺点是载波频率偏移（CFO）和较大的峰均功率比（PAPR），它们均会降低误码率（BER）。具体来说，我们在这里考虑削波或任何其他PAPR降低方法，足以防止非线性大功率放大器产生误差。此外，在小小区中，信噪比很大，而小的时间分散使OFDM符号循环前缀可以防止符号间干扰。这保留了CFO单独确定BER的能力，反之亦然，从而可以通过简单的BER测试间接估计CFO引起的相位失真。但是，一个特殊的问题是测量非常低的BER值（由类似的残留CFO生成），为了获得统计上足够的误差，该值可能会持续很长时间。如果通过将干扰信号添加到接收器的每个子载波，以可控的方式降低噪声容限，则可以大大减少测试时间。可以证明这种方法可以进行有效且准确的短期BER（以及CFO相位误差）测试。