HDPath™ Digital Fade Margin
Q: How can I compute microwave link fade margins for digital systems?
A: With TAP6.0.2161 or later and a Maintenance Subscription date of March 31, 2007, or later, you can compute both the Thermal Fade Margin (TFM) typically used for analog systems, and the Composite Fade Margin (CFM) used for digital systems.
(For details on the calculation of TFM and CFM, see the article on Microwave System Equations.)
Note that all values in this example are for demonstration purposes only. You should determine appropriate settings for your application.
For example, suppose you have a path profile displayed in HDPath. The digital specifications used to compute the CFM are in the “Receiver Digital Specs” section of the Receiver Fixed Facility interface. For analog systems, all of the values are set to zero:
Click the Microwave Link Budget button to compute the link information for the path:
The Microwave Link Budget form is displayed:
You can scroll down to the bottom of the report to see the reliability and outage calculations based on the Thermal Fade Margin (TFM):
If the link is for a digital system, you can enter the parameters for the Dispersive Fade Margin (DFM), the Adjacent Channel Interference Fade Margin (AIFM) and the External Interference Fade Margin (EIFM) as applicable:
When any of the Receiver Digital Specifications are included, the Microwave Link Budget report includes the unavailability (Undp), Reliability percentage, and link outage (seconds per year) values computed using the Composite Fade Margin (CFM) as well as the Thermal Fade Margin (TFM).
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Copyright 2007 by SoftWright LLC