Wireless Channel Modeling Perspectives for Ultra-Reliable Communications

Ultra-Reliable Communication (URC) 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 analyze the tail of the Cumulative Distribution Function (CDF) of block fading channels in the regime of extremely rare events, i.e., the ultra-reliable (UR) regime of operation. Our main contribution consists of providing a unified framework for statistical description of wide range of practically important wireless channel models in the UR regime of operation. Specifically, we show that the wireless channel behavior
in this regime can be approximated by a simple power law
expression, whose exponent and offset depend on the actual channel model. The unification provides a channel-agnostic tool for analyzing and performance optimization of radio systems that operate in the UR regime. Furthermore, the unified model is particularly useful in emerging measurement campaigns for empirical characterization of wireless channels in the regime of low outages. Finally, the asymptotic analysis can serve as an underlying building block for designing more elaborate, higher-layer technologies for URC. We showcase this by applying the power law results to analyze the performance of receiver diversity schemes and obtain a new simplified expression for Maximum Ratio Combining (MRC) that can be used to analyze multiple antenna wireless systems in an UR regime.