Appendix A: Path Evaluation Information
A-7
Moseley SL9003Q
602-12016-01 Revision J
Line 19
: Enter the minimum Annual Outage (from Table A-6).
Line 20
: Enter the Reliability percentage (from Table A-6).
A.2.4 Path Availability & Reliability
For a given path, the system reliability is generally worked out on methods based on the
work of Barnett and Vigants. The presentation here has now been superseded by CCIR 338-
6 that establishes a slightly different reliability model. The new model is more difficult to use
and, for most purposes, yields very similar results. For mathematical convenience, we will
use fractional probability (per unit) rather than percentage probability, and will deal with the
unavailability or outage parameter, designated by the symbol U. The availability parameter,
for which we use the symbol A, is given by (1-U). Reliability, in percent, as commonly used
in the microwave community, is given by 100A, or 100(1-U).
Non-Diversity Annual Outages
: Let U
ndp
be the non-diversity annual outage probability
for a given path. We start with a term r, defined by Barnett as follows:
r = actual fade probability/Rayleigh fade probability ( =10-F/10)
Where,
F = fade margin, to the minimum acceptable point, in dB.
For the worst month, the fade probability due to terrain is given by:
rm = a x 10-5 x (f/4) x D3
Where,
D = path length in miles.
f = frequency in GHz.
a (terrain factor)
= 4 for smooth terrain.
= 1 for average terrain.
= 1/4 for mountainous, very rough, or very dry terrain.
Over a year, the fade probability due to climate is given by:
ryr = b x rm
Where,
b (climate factor)
= 1/2 for Gulf coast or similar hot, humid areas.
= 1/4 for normal interior temperate or northern regions.
= 1/8 for mountainous or very dry areas.
By combining the three equations and noting that U
ndp
is equal to the actual fade
probability, for a given fade margin F, we can write:
U
ndp
= ryr x 10-F/10 = b x rm x 10-F/10
or
U
ndp
= a x b x 2.5 x 10-6 x f x 10D3 x 10-F/10
The following table shows the relationship between system reliability and outage time.
Summary of Contents for Starlink SL9003Q
Page 86: ...5 22 Section 5 Module Configuration Moseley SL9003Q 602 12016 01 Revision J ...
Page 90: ...6 4 Section 6 Customer Service Moseley SL9003Q 602 12016 01 Revision J ...
Page 110: ...A 10 Appendix A Path Evaluation Information Moseley SL9003Q 602 12016 01 Revision J ...
Page 118: ...D 2 Appendix D Microvolt dBm Watt Conversion 50 ohms Moseley SL9003Q 602 12016 01 Revision J ...
