User's Manual

Installation Guide
27 of 27
Link Verification
Verify the ARCXtend wireless link
• Downstream path measurements
DS
Modulation
Expected Performance Troubleshooting
64 QAM 28 dB MER
10
-8
BER, post-error
correction
256 QAM 31 dB MER
10
-8
BER, post-error
correction
Inspect the constellation to
determine the type of impairment
affecting the signal and
troubleshoot accordingly.
Verify the plant MER is greater
than required for the downstream
modulation
• Upstream path measurements
Parameter Expected Performance Troubleshooting
CM output
Power
+40-50 dBmV typical
+55 dBmV max
+30 dBmV min
If the cable modem output power is
too high, reduce the amount of loss
in the drop to allow for margin or
reduce the “Upstream Attenuation”
setting.
If cable modem output power is too
low, increase the hub’s “Upstream
Attenuation” setting.
BER 10-8 BER, post-error
correction for QPSK and 16
QAM
To test BER on the return
path, the analyzer can ping the
CMTS with a packet of
known data. The ping
command will return the
packet to the analyzer from
the CMTS on the downstream
path.
Verify the return or upstream path
of the wireless link at the U/S Tap
on the hub with PureBurst disabled
and with a spectrum analyzer set to
maximum hold.
If interference is present in the 10
to 42 MHz band, change to a
different upstream RF channel or
move the CPE to a different
location.
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