Gustavo A. Siles

Atmospheric Attenuation in Wireless Communication Systems at Millimeter and THz Frequencies [Wireless Corner]

This paper intends to give an overview about atmospheric propagation effects affecting millimeter and terahertz (THz) communication systems. The main focus is on attenuation caused by atmospheric gases and liquid water droplets, either in the form of suspended particles into clouds or rain falling hydrometeors. Theoretical aspects about each of them are presented, emphasizing on those that deserve special attention as frequency increases. Statistics of attenuation estimated from meteorological data and some experimental results, as in the case of rain attenuation, obtained in Madrid, Spain, are presented throughout the paper, thus providing further insights about the phenomena discussed.

Experimental assessment of slant-path rain attenuation variability in the Ka-band

Summary This study is based on the results of a slant-path Ka-band propagation experiment carried out in Madrid, Spain, regarding rain attenuation, which is the main propagation impairment in this frequency band. The experimental and statistical results correspond to seven complete years of measurements, a period large enough to accomplish a comprehensive analysis in order to characterize the variability of rain rate and attenuation. It is shown that year-to-year variability is significant in temperate climates as Madrids. The aforementioned significance is also apparent with regards to seasonal, monthly, worst-month and hourly variability concerning rain attenuation, which are also discussed and related when possible to the variability of the rain phenomena, either represented by the total amounts of rainfall in the different periods or by rain rate statistics. Copyright

An Application of IGS Zenith Tropospheric Delay Data to Propagation Studies: Validation of Radiometric Atmospheric Attenuation

The objective of this paper is to continue exploring the use of International GNSS Service (IGS) products as a tool to be used in Earth-space propagation experiments. With this purpose, 4 years of Zenith Tropospheric Delay data from IGS Villafranca station, in Madrid, Spain, have been processed with the aim to estimate the attenuation due to gases. These values are then used for the validation of a concurrent database of 4 years of radiometric measurements at 19.7 GHz, collected at Universidad Politécnica de Madrid (UPM) with the purpose of studying the attenuation effects of gases and clouds. The suggested validation procedure includes both an automatic routine and visual inspection. The validated measurements are statistically analyzed on a yearly and seasonal basis. Results point toward the usefulness of IGS data in propagation experiments as well as their integration in their processing routines.

Fade and Interfade Duration Characteristics in a Slant-Path Ka -Band Link

Satellite-to-earth links are subject to several propagation effects in the troposphere, being rain attenuation the impairment that can cause the deepest fades. In this paper, the duration of both fades and the intervals between consecutive fades (interfade intervals) are characterized on the basis of the results of a long-term slant-path Ka-band propagation experiment carried out in Madrid, Spain. The experimental and statistical results included in this paper correspond to seven complete years of measurements, a period large enough to characterize not only the average-year statistics of fade dynamics but also their variability, which is assessed on the basis of annual statistics of durations. The obtained average-year statistics of fade durations are in many cases close to the predictions made by the International Telecommunication Union-Radiocommunications and Communications Research Center Canada models, although the predictions could be improved with a better selection of the parameters of the distributions used in the models. Interfade duration statistics are also presented and related to recent modeling efforts. The interannual variability of statistics, such as the relative number of fades, is quantified and found to be low, except for the higher attenuation thresholds or the highest durations considered in this paper.

Propagation Measurements at 19.7 and 99 GHz Using Ground-Based Radiometers

Radiometers are commonly used in order to assess the atmospheric propagation channel under low-attenuation and scatter-free conditions, with an increasing tendency toward using millimeter frequencies. In this letter, the interest is concentrated on the analysis of atmospheric attenuation measurements simultaneously obtained, under clear sky and the presence of clouds, by two independent and colocated ground-based radiometers at 19.7 and 99 GHz, in April of 2012 in Madrid, Spain. The experimental results obtained are in agreement with the estimations based on vertical meteorological profiles, and it is relevant to mention the high sensitivity to cloud liquid water provided by the measurements at 99 GHz. In general, the perspective of this work points toward the validity of using millimeter radiometry in propagation applications.

Propagation measurements on terrestrial links in Madrid

Propagation in the millimeter-wave band has been analyzed using experimental measurements on three terrestrial links working at 38, 75 and 85 GHz carried out in Madrid, Spain. Rain attenuation is the most relevant impairment in such band. Statistics obtained from experimental attenuation time series have been compared with several model predictions. The experimental drop size distributions provided by a disdrometer and a 24 GHz Doppler radar have been used to estimate rain attenuation.