1. College of Information Engineering, Zhejiang University of Technology, Hangzhou 310023, China
2. Zhejiang Provincial Key Laboratory of Communication Networks and Applications, Hangzhou 310023, China
Corresponding author (email@example.com
Estimations of channel gain, noise variance, and Doppler shift are of great importance in mobile communications. However, the relative motion of the mobile transceiver results in time-varying channels and, therefore, degrades the accuracy of channel parameter estimators. Thus, this paper attempts to characterize such degradations in a general time-selective channel environment, where we derive finite-sample Cramér-Rao lower bounds (CRLB) by assessing the joint effects of Doppler shift (mobile speed), direction of propagation, and additive white noise. These bounds will provide insights into the potential for the estimation of the aforementioned channel parameters. Furthermore, an approximation scheme is proposed in order to tackle the boundary singularity of the channel power spectrum density (PSD). Numerical computations demonstrate that the approximated method produces similar results to the non-approximated method, so long as the sample number satisfies a certain condition. Additionally, the approximated method effectively extends the applicable Doppler range of the non-approximated method.
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