Abstract:
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).
