595 research outputs found
An estimation of tropospheric agents influence on 5G terrestrial radio services in the THz band
No full textRecent technological advances made possible the development of devices and integrated circuits operating at frequencies greater than 100 GHz and telco operators, in order to face with the growing demand for bandwidth from users, are increasingly turning their interest to the feasibility of use wireless links also at sub-millimeter frequencies (300 GHz-l THz). This spectral region, also named TeraHertz band, offers greater availability of contiguous bands and is under investigation by international standardization bodies such as ITU and CEPT. The present study intends to provide useful insights to define technical and operational characteristics for 5G applications aimed at land-based fixed services operating in bands up to 1 THz. In this study simulations was carried out to provide an estimation of attenuation levels due to the gaseous component, precipitating events present in the troposphere at the ground level. Furthermore, radio refractivity was also estimated. All results are referred to the Italian territory and for frequencies ranging from 40 to 840 GHz
Simulation of radiometric and attenuation measurements along earth-satellite links in the 10- to 50- GHz band through horizontally-finite convective raincells
No full textAn iterative solution is illustrated of the three-dimensional radiative transfer
equation for a horizontally finite and vertically inhomogeneous precipitating cloud. The
method is applied to modeling a convective rain cell of cylindrical shape, characterized by
spherical raindrops having a negative-exponential drop size distribution. The realistic
model also takes into account the presence of a cloud and an ice layer above the rain cell
itself. The simulated brightness temperature, the mean radiative temperature, and the
path attenuation are evaluated in a three-dimensional geometry from a surface
observation point in order to simulate a ground-based station with a beacon receiver and
a multichannel radiometer. Numerical results are shown to illustrate the potential of the
proposed model for different sets of frequency channels, observation geometries, cloud
sizes and types, and precipitation intensities. After generating a large data set by varying
the relevant rain cell parameters, regression analysis is applied to derive a statistical
estimation of the total path attenuation from surface rain rate and ground-based
radiometric measurements together with the frequency scaling factors for cumuliform
clouds in the 10- to 50-GHz band
Identification of rainy periods from ground based microwave radiometry
No full textIn this paper the authors present the results of a study aiming at detecting rainy data in measurements collected by a dual band ground-based radiometer. The proposed criterion is based on the ratio of the brightness temperatures observed in the 20-30 GHz band without need of any ancillary information. A major result obtained from the probability density of the ratio computed over one month of data is the identification of threshold values between clear sky, cloudy sky and rainy sky, respectively. A linear fit performed by using radiometric data and concurrent rain gauge measurements shows a correlation coefficient equal to 0.56 between the temperature ratio and the observed precipitation
Variability and Dynamic Characteristics of Attenuation Derived by Ground-Based Microwave Radiometer
No full textIntercomparison of Integrated Water Vapor Measurements at High Latitudes from Co-Located and Near-Located Instruments
No full textData from global positioning system (GPS) ground-based receivers, ground-based microwave radiometers (MWRs), and radiosondes (RS) at two high-latitude sites were compared. At one site, the North Slope of Alaska (NSA), Barrow, Alaska (USA), the instruments were co-located, while at the other site, the second ARM Mobile Facility (AMF2), Hyytiälä, Finland, the GPS receiver was located about 20 km away from the MWRs and RS. Differences between the GPS-derived integrated water vapor (IWV) and the other three instruments were analyzed in terms of mean differences and standard deviation. A comparison of co-located and near-located independently calibrated instruments allowed us to isolate issues that may be specific to a single system and, to some extent, to isolate the effects of the distance between the GPS receiver and the remaining instruments. The results showed that at these two high-latitude sites, when the IWV was less than 15 kg/m2, the GPS agreed with other instruments within 0.5–0.7 kg/m2. When the variability of water vapor was higher, mostly in the summer months, the GPS agreed with other instruments within 0.8–1 kg/m2. The total random uncertainty between the GPS and the other systems was of the order of 0.6–1 kg/m2 and was the dominant effect when the IWV was higher than 15 kg/m2
Assisting Italian DVB-T users against LTE Signal Impairments: The “HELP Interferenze” Project
No full textForward modeling of an atmospheric scenario: Path characterization in terms of scattering intensity
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