  Ultra-Reliable Low Latency Communication (URLLC) is one of the distinctive
features of the upcoming 5G wireless communication, going down to packet error
rates (PER) of $10^{-9}$. In this paper we discuss the statistical properties
of the wireless channel models that are relevant for characterization of the
lower tail of the Cumulative Distribution Function (CDF). We show that, for a
wide range of channel models, the outage probability at URLLC levels can be
approximated by a simple power law expression, whose exponent and offset depend
on the actual channel model. The main insights from the analysis can be
summarized as follows: (1) the two-wave model and the impact of shadowing in
combined models lead to pessimistic predictions of the fading in the URLLC
region; (2) the CDFs of models that contain single cluster diffuse components
have slopes that correspond to the slope of a Rayleigh fading, and (3)
multi-cluster diffuse components can result in different slopes. We apply our
power law approximation results to analyze the performance of receiver
diversity schemes for URLLC-relevant statistics and obtain a new simplified
expression for Maximum Ratio Combining (MRC) in channels with power law tail
statistics.
