  Simple and accurate expressions for path gain are derived from
electromagnetic fundamentals in a wide variety of common environments,
including Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) indoor urban
canyons, urban/rural macro, outdoor-indoor and suburban streets with
vegetation. Penetration into a scattering region, sometimes aided by guiding,
is the "universal" phenomenon shared by the diverse morphologies. Root Mean
Square (RMS) errors against extensive measurements are under 5 dB, better than
3GPP models by 1-12 dB RMS, depending on environment. In urban canyons the
models have 4.7 dB RMS error, as compared to 7.9 dB from linear fit to data and
13.9/17.2 dB from LOS/NLOS 3GPP models. The theoretical path gains depend on
distance as a power law with exponents from a small set {1.5, 2, 2.5, 4},
specific to each morphology. This provides a theoretical justification for
widely used power law empirical models. Only coarse environmental data is
needed as parameters: street width, building height, vegetation depth, wall
material and antenna heights.
