Current frequency allocations below Ku- band are becoming increasingly congested.
The problem continues to grow as the use of telecommunications becomes more pop-
ular. In order to compensate for increased in demand, telecommunication operating
frequencies have to be raised, yielding larger channel capacity. However, raising the
operating frequency has the adverse result of intensifying the attenuation effects of the
troposphere. At high frequencies, such as V-band, rain is known to cause the most
It has been shown that model data for numerical weather prediction, combined with
propagation prediction models, can be used to forecast telecommunication link atten-
uation. The forecast of attenuation can be used to improve the effectiveness of fade
mitigation techniques. A key problem in determining rain attenuation from rainfall
rate is the considerable variability of the raindrop size distribution (DSD). Based on
the analysis of disdrometer and numerical weather prediction model data, the aim of
this work is to constrain the parameters of the DSD and ultimately generate proba-
bilistic forecasts of attenuation.
Using disdrometer analysis, a relationship between mean raindrop size and rainfall rate
is established, and a link between drop concentration and rainfall rate is also demon-
strated. The DSD is shown to vary with season and shows some small relationships
with meteorological parameters. It is concluded that, despite some relation of the
DSD with rainfall rate and meteorological parameters, there are too many variables to
conclusively recreate the DSD.
Analysis of the attenuation-rainfall rate relationship illustrates that variability due to
the DSD increases with frequency above 40GHz. At 30-40GHz the DSD is shown
to have little impact on the attenuation-rainfall rate relationship. Finally, this thesis
examines the horizontal structure of rain cells in the UK, demonstrating the suitability
of the EXCELL model and illustrating that rain cells are more elliptical in the UK.
|Date of Award||1 Jun 2011|
|Supervisor||Robert Watson (Supervisor)|