User's Manual

ARCXTEND USER MANUAL – R1.4, ISSUE 4
Copyright 2005 Arcwave, Inc. 37
Link Verification
Downstream path measurements
DS Modulation Expected Performance Troubleshooting
64 QAM
27 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
256QAM
31 dB MER
10
-8
BER, post-error correction
Verify the downstream power level
into the cable modem is between -6
dBmv and +15 dBmV.
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
Table 4-5: Downstream path measurements
Upstream path measurements
Parameter Expected Performance Troubleshooting
CM output Power
+40-52 dBmV typical.
58 dBmV max for QPSK, 55
dBmV for 16 QAM
If CM output power is too high,
reduce the amount of loss in the
drop to allow for margin or reduce
the 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. To be
sure the packet does not go
any further than the CMTS
port; the analyzer can use a
trace route command to the
Verify RF return path performance
with the wireless link. This can be
done by looking at the BER of the
cable modem in the hub.
Check for interference in the 5.250
to 5.350 GHz band. If interference
is present, try changing the
upstream frequency HI/LO setting.