An Explicit Ground Reflection Model for mm-Wave Channels

5G mobile communication systems are likely to use the enormous bandwidths available at mm-wave frequencies. However, there is an important propagation effect that can have a major impact on the performance - the ground reflection (GR). This effect is currently not sufficiently covered by existing 3GPP propagation models. The GR causes fading both on the small-scale level, e.g., multi-path fading, and on the large-scale level, e.g., path loss and shadow fading. However, the small-scale effects become more dominant at mm-wave frequencies. This paper presents a method to explicitly include the GR in geometry-based stochastic channel models. First, an improved small-scale fading model is proposed that covers the influence of the GR on the delay and angular spreads as well as on the polarization. Second, the influence of the electromagnetic properties of the ground is discussed. Third, the path loss and shadow fading models are adjusted to accommodate the large-scale effects of the GR. The updated model allows taking GR fading into account when designing new radio communication systems and evaluate the performance before the standardization, prototyping and product development phase.