Robert T. Johnk and John J. Lemmon

Abstract:

This paper examines the estimation of the local mean voltage of a radio signal in a Rayleigh fast-fading environment. We focus on the statistical uncertainties of local voltage averages obtained by both integrating the voltage envelope of a specified spatial interval and averaging over a set of discrete spatial samples. We derive new analytical expressions of the variances of both discrete and continuous averaging for selected spatial intervals. We also give recommendations for averaging intervals and sample spacing to achieve a ±1 dB spreading factor. We provide important new results for the variance of discrete averaging with new insight gained on separations required for uncorrelated samples. One significant finding of this work is that criteria in the published literature are incorrect and underestimate the variance. We support these findings with an experimental validation of our variance expressions using laboratory fading simulator measurements and sample statistics.

Keywords: autocorrelation; propagation; fast signal fading; correlation; path loss; continuous wave (CW); Rayleigh; time series; vector signal analyzer; channel sounder; coverage factor; I/Q envelope; local mean; Lee 40 wavelength criterion; sampling; standard deviation; spreading factor; variance; discrete average

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