The quantification of wet antenna attenuation (WAA) represents one of the major uncertainties in rainfall retrieval from commercial microwave links (CMLs). We propose identifying WAA distribution and upper limits based on rainfall climatology without the need for nearby rainfall observations. The quantified contributions of antenna wetting due to total loss are derived from 2 years of data collected from eight short (48-497 m) CMLs operating at frequencies of 37.3-39.2 GHz within the cellular backhaul. More specifically, the complementary cumulative distribution functions of measured attenuation are compared with theoretical ones calculated from rainfall data from local rain gauges. The results show that WAA reaches 1.5-2.0 dB and dominates over path attenuation during light rainfalls (R < 2 mm/h). WAA can, however, reach 2.8-5.3 dB during heavy rainfalls and maximal WAA observed during extreme rainfalls (R ≈ 70-130 mm/h) is between 6-9 dB. The constant value of WAA used in some previous studies may, therefore, lead to a significant overestimation of peak rainfalls retrieved from CMLs.

The Land Mobile Satellite (LMS) channel at 2 GHz is examined and the first order statistics are modeled using experimental data for two tree shadowing scenarios. Considering that the first order statistics of the channel are used as input to channel models as well as for the calculation of the system margins, the modeling of the probability density function (PDF) and the cumulative distribution function (CDF) of the received signal envelope is of great importance for the design of LMS systems. Experimental data from measurements performed in Prague, the Czech Republic, are presented for two scenarios, a Heavy Tree Shadowing one and an Intermediate Tree Shadowing one. Four of the most widely used distributions, Rayleigh, Rice, Loo and lognormal, are considered for the modeling of the CDF of the signal envelope. Loo and Rice distributions out of the four considered distributions provide the best fit with reference to the measured data. Moreover, analytical empirical expressions are given for the parameters of the Loo distributions as a function of the elevation angle, to be used for the modeling of the LMS channel under tree shadowing. It is found that the expressions for the estimation of the distributions' parameters provide a good fit to the experimental data.

An extensive measurement campaign, covering a representative set of typical buildings in an urban area and aimed at building penetration loss for satellite services at L-, S- and C-band, was performed in Prague in the summer of 2009. Throughout the measurements, a remote-controlled airship was used as a pseudo-satellite carrying a transmitter which provided unmodulated continuous wave left-handed circularly polarized signals at 2.0 GHz, 3.5 GHz, 5.0 GHz, and 6.5 GHz. A description of the measurement campaign is provided here, together with a thorough analysis of the resulting experimental data. A significant dependence on elevation angle is reported for line-of-sight and non-line-of-sight propagation conditions separately. Subsequent steps to introduce elevation dependent empirical models at corresponding frequencies follow. Finally, a comparison to other studies dealing with building penetration loss for high elevation angles is presented.

Seasonal variations of the polarization diversity gain are addressed for a nomadic user in a vegetated area taking high elevation angles and nongeostationary satellites into consideration. Corresponding experimental data were obtained at a frequency of 2.0 GHz at Stromovka Park in Prague, the Czech Republic, within the full in-leaf and out-of-leaf periods of 2013 and 2014, respectively. By detecting copolarized and cross-polarized components of the transmitted left- and right-handed circularly polarized signals, the corresponding diversity gain was obtained for multiple-input single-output (MISO), single-input multiple-output (SIMO), and combined MISO/SIMO cases. It was found that tree defoliation results in a significant decrease of the polarization diversity gain achieved for low time percentages in particular scenarios.

Atmospheric refractivity and its vertical gradient affect electromagnetic wave propagation in the atmosphere. Consequently, their statistics are needed for propagation predictions. New world maps of refractivity and its vertical gradient statistics are derived from a global, long-term dataset of meteorological quantities as given by ERA-Interim reanalysis. The derived maps provide long-term statistics obtained from 33 years of meteorological data with a one-degree spatial resolution on a latitude/longitude mesh. A processing method is described and examples of the derived maps are shown. The consistency of the new maps is checked by comparing world maps provided by ITU-R. Accuracy is tested by comparing refractivity statistics obtained from high-quality local measurements using radiosonde and tower measurements. New global maps demonstrate enhanced statistical stability, spatial resolution, and accuracy.

A sensitivity analysis of the multiple scattering theory applied to propagation in tree canopies is presented. This analysis aims at addressing the influence of input parameters on the canopy's equivalent scattering amplitude as well as the overall coherent and incoherent scattered fields. The main input parameters of interest were identified as frequency, number densities and dielectric parameters of branches and leaves, polarization, and a canopy shape. A number of graphical results are provided enabling to identify the key parameters of corresponding radio-wave propagation models based on the multiple scattering theory.