ND SatCom SKYWAN IDU 7000, Manual

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80 Network Design and Engineering Guide 2010-10-26
Outdoor Unit and Satellite Link Design
Fundamentals of Link Budget Calculation
link availability of 99.9% will result in a higher rain margin compared to an availability of only
98%. The following picture presents an overview of ITU-T rain zones in Europe and Northern
Africa:
Figure 3-5 ITU-T Rainzones Europe and North-Africa
Rain Margin and Uplink Power Control
The inclusion of rain fade in the link budget calculation increases the power requirements on
the earth stations and on the satellite transponder.
As an example we assume a situation where according to the required availability and the rain
zones of the earth stations a necessary rain margin of 5 dB for the uplink and 4 dB for the down-
link is determined. The difference between up- and downlink could result from different rain
zone locations of the earth stations and the higher frequency of the uplink compared to the
downlink. The power requirements for the earth station and the satellite transponder at maxi-
mum rain fade is shown in figure 3-6.