An analytical multiple scattering model to characterize free-space millimeter-wave and optical links in presence of atmospheric impairments

An analytical radiative transfer model to account for propagation of monochromatic radiation in random media with a plane-parallel geometry is presented. The model employs an Eddington-like approach combined with the delta phase-function transformation technique. A first-order scattering correction to the Azimuth-dependent Eddington Radiative Model solution is also performed to improve the model accuracy for low scattering media and flexibility. The first-order scattering corrected solution, named Generalized Eddington Radiative Model (GERM), is systematically tested against a numerical multi-stream discrete ordinate model. The typical mean accuracy of GERM solution is generally better than 10% with a standard deviation of 20% for radiance calculations over a wide range of independent input optical parameters and observation angles. The proposed model can be applied in quite arbitrary random medium and results to be appealing for millimeter-wave line-of-sight propagation and free-space optics.