Rain cell size attenuation modelling for terrestrial and satellite radio links.
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Date
2011
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Abstract
There is need to improve prediction results in rain attenuation in order to achieve reliable wireless
communication systems. Existing models require improvements or we need fresh approaches.
This dissertation presents a model of rain attenuation prediction for terrestrial and satellite radio
links based on a novel approach. This approach postulates that the difference in rain attenuation for
various locations is attributed to the dissimilar rain drop sizes and rain cell diameter sizes and that
cell sizes derived from local measurements would depict the true nature of rain cells better than the
cells derived from long term rain data gathered from different climates. Therefore all other link
parameters used in the attenuation equation are presented by the use of mathematical analysis; but
the rain cell size is derived from local rain rate measurements.
The physical link aspects considered in the mathematical attenuation model are: the Fresnel
ellipsoid of the link path, the effect of elevation angle, the rain cell diameter size and the shape of
growth of rain rates in the cell. The effect of the elevation angle of the link on the scale of
attenuation is accounted for through the proposed coefficient of elevation equation. The coefficient
of elevation is considered to modify the size of the rain cell diameter in proportion to the elevation
angle of the link and the rain rate growth is taken to be of the truncated-Gaussian form. On the
other hand, the rain cell diameter is derived from rain rate measurements as a power law model and
substituted in the attenuation expression.
The rain cell size model evaluated in this dissertation is based on point rain rate measurement data
from the disdrometer located at the University of KwaZulu-Natal, South Africa. The “Synthetic
Storm” technique is applied to develop the rain cell diameter distributions and the rain cell
diameter model. In addition, the impact of the rain cell diameter size model in site diversity and
cellular network-area planning for the region is discussed.
To validate the model for terrestrial links, attenuation data collected from Durban, South Africa is
used while that for satellite links, attenuation data from 15 links which are located in tropical
climatic zones are used. In each case, the new model is tested against some well-known global rain
attenuation prediction models including the standard ITU-R models. The performance of the
proposed models for the sampled radio links based on error estimations shows that improvements
have been achieved and may be regarded as a universal tropical model especially for satellite links.
Description
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
Keywords
Rain and rainfall--South Africa., Millimeter wave communication systems., Radio waves--Attenuation., Theses--Electronic engineering.