Low-biased Doppler frequency estimation scheme employing variable prefilter and sampling rate

There are several popular Doppler frequency estimation algorithms using pilot symbols in wireless communication systems. When there exist additive noise, the estimates of these algorithms are upward biased. Prefiltering and down-sampling the received pilot symbols reduces the bias because it improves the signal-to-noise ratio and decreases the noise bandwidth. However, when the cutoff frequency of prefilter and sampling rate are fixed considering the expected maximum Doppler frequency, the bias at low Doppler frequency is not sufficiently reduced. In this paper, we propose several variable Doppler frequency estimation schemes employing variable Doppler frequency estimation schemes employing variable sampling rate, variable prefilter or the both of them. The performance of the proposed estimation schemes is analytically evaluated and verified by computer simulation. The evaluation results show that the bias due to additive noise is considerably reduced using the proposed schemes.