Studies of scintillation on earth-space paths

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Use of V-band geostationary satellites to deliver multimedia services

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Investigation of the effects of cloud attenuation on satellite communication systems

The aim of this project is to investigate the attenuation due to clouds at 20- 50GHz; to develop an accurate long-term prediction model of cloud attenuation applicable to slant-path links and evaluate the impact of cloud attenuation dynamics on the design of future portable EHF earth-space systems. Higher frequencies offer several advantages, for example, greater bandwidth and immunity to ionospheric effects. The EHF band is being targeted for the launch of earth-space communication systems to provide global delivery of bandwidthintensive services (e.g. interactive HDTV, broadband internet access and multimedia services, television receive-only, etc.) to portable terminal units. Since spectrum shortage and terminal bulk currently preclude the realization of these breakthrough-broadband wireless communication services at lower frequencies, a better understanding is needed in order to optimize their usage. One major obstacle in the design of EHF earth-space communication systems is the large and variable signal attenuation in the lower atmosphere, due to a range of mechanisms including attenuation (and scattering) due to clouds and rain, tropospheric scintillation caused by atmospheric turbulence and variable attenuation by atmospheric gasses. In particular, cloud attenuation becomes very significant at EHF. In this thesis, we start with an overview of literature review in the first chapter. Followed next by the theory and description of accepted-up to date- cloud attenuation models in the field (chapter 2). Then followed up by a description of the pre-processing, validations, sources and assumptions made in order to conduct the analysis of the cloud attenuation in this work (chapter 3). Afterwards, a comprehensive analysis of Meteorological and local tropospheric degradation was carried out (chapter 4). That was followed by an overview of cloud fade statistics and suggested methods to counter their effects (chapter 5). And finally the improved cloud attenuation model and the enhancement of the currently accepted cloud attenuation model (ITU-R 840.4) by terms of validating the effective temperature concept and ways of acquiring it (chapter 6)

Three Years of Atmospheric Characterization at Ka/Q-band with the NASA/POLIMI Alphasat Receiver in Milan, Italy

Since June of 2014, NASA Glenn Research Center (GRC) and the Politecnico di Milano (POLIMI) have jointly conducted a propagation campaign within the framework of the Alphasat propagation experiment through a propagation terminal at the POLIMI campus in Milan, Italy. The terminal utilizes the 20 GHz and 40 GHz beacons broadcast by the Aldo Paraboni Technology Demonstration Payload (TDP #5), and consists of dual coherent Ka- and Q-band beacon receivers. These provide a direct measurement of the signal attenuation and scintillation and are complemented by concurrent weather instrumentation that provides measurements of the atmospheric conditions at the receiver. The primary goal of these measurements is to improve model predictions of communication system performance at 40 GHz. Over three years of concurrent measurements have now been collected from the terminal, and herein we present a statistical analysis of the results thus far, as well as a summary of recent hardware upgrades to the receivers that were made in September 2017

Joint Use of On-board Reconfigurable Antenna Pattern and Adaptive Coding and Modulation in Satellite Communications at High Frequency Bands

The Telecommunication market is driven by the increasing need of the end users for multimedia services which require high data rates. Within the fixed satellite service, frequency bandwidths wide enough to carry such high data rates are to be found in Ka band (26-40 GHz), and Q/V bands (40-50 GHz). However, at Ka band and above, transmitted signals can be severely affected by tropospheric attenuation for substantial percentages of time, resulting in the degradation of the quality and of the availability of communication services. Fade Mitigation Techniques (FMTs) must be used to counteract these severe propagation impairments. In this thesis we explore the joint use of two of the most promising techniques, known as Reconfigurable Antenna and Adaptive Coding and Modulation, which up to now has been separately developed. Some of our accomplishments include, but are not limited to: a methodology to describe rain attenuation conditions for multiple users in large geographical areas, a tractable framework for the generation of correlated time series of rain attenuation for multiple receiving stations, the comparison of performance between fixed antenna systems and Reconfigurable Antenna system coupled with Adaptive Coding and Modulation

Proceedings of the Thirteenth NASA Propagation Experimenters Meeting (NAPEX 13)

The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. The meeting was organized into three technical sessions: the first focused on mobile satellite propagation; the second examined the propagation effects for frequencies above 10 GHz; and the third addressed studies devoted exclusively to the Olympus/Advanced Communications Technology Satellite (ACTS) Program