Signal limiting in envelope correlations for diversity channel evaluation: a statistical approach

The Rayleigh-like distributed envelopes encountered in mobile communications occupy a wide dynamic range, typically 10 dB above the local mean to 40 dB below the local mean, with the range decreasing for increasing bandwidth. The local mean varies owing to shadow fading, by tens of dB, and on top of this, the inverse-distance loss can vary by some 50 dB within a cell. In characterizing the Rayleigh-like fading in real-world channels, measuring equipment needs to be expensive to cover such a dynamic range or else signal limiting occurs. For diversity channel evaluation, the correlation coefficient between channels is required in order to establish the potential diversity gain. This paper gives a statistical formulation for the effect of soft- and hard-clipped envelopes used for the correlation coefficient. It is shown that even hard-clipped envelopes are useful for diversity channel evaluation using the correlation coefficient.