Aviat Networks ECLIPSE EDGE, Руководство пользователя

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4 Aviat Networks
Chapter 5. Eclipse Edge Commissioning and Troubleshooting
• For a looped test the originating DAC provides the PBBS generator and G.821
receiver. Requires a far-end loopback on the trib, which can be applied using Portal
or a physical loop.
• For a both-way test, a PRBS generator on one DAC is G.821 received on its remote
DAC, and vice-versa. No loopback is required.
Edge also supports a digital loopback option. Refer to
Loopback Points on
page 113
.
Where an external BER tester is to be used, refer to manufacturer instructions.
NOTE:
External testers provide superior measurement accuracy and access
to a wider range of test and measurement functions.
Fade Margin for Edge
This test is designed to check that the expected (calculated) fade margin for a link
matches actual performance.
The expected fade margin should be included in the link installation datapack
together with Tx power, system losses, antenna gains, the effective radiated power,
free space path loss, expected receive signal level and the calculation for link
availability.
The fade margin test measures the difference in receive signal level between the
normal, operational level, and the threshold level, the level at which bit errors appear.
The threshold level can be specified for a bit error rate (BER) of 10
-6
or 10
-3
. For
Eclipse Edge, the difference between 10
-3
and 10
-6
thresholds is not more than 2dB.
CAUTION:
Fade margin measurement should only be conducted after it
has been verified that expected RSLs, as indicated in Portal
performance screens, are correct at both ends of the link. If
an RSL is low, the reason for this must first be investigated
and resolved.
When coupled with an ability to measure receive signal level at the receiver input, this
procedure also provides an indication of receiver threshold, which can be checked
against receiver specifications.
For Edge, a fade margin test involves reducing the Tx power at one end of the link,
and checking the error performance at the other using the G.826 data presented in
the Portal Performance Screen. However, achieving a threshold RSL is only possible
where there is sufficient adjustment available in Tx power.
• Tx power adjustment ranges apply down from the maximum power setting
supported by the frequency and bandwidth option configured for the link.
• Therefore, in situations where the expected fade margin is greater than the Tx
power-reduction range available within Portal, it is not possible to reach threshold.
Nevertheless, reducing Tx power to its minimum and confirming error-free
operation should still provide an acceptable degree of confidence.