I have upgraded D/S Modulation from QAM 64 to QAM 256,while D/S channel width remains to 6 MHz.Does it required any more changes in CMTS configuration or network???
If you have moved from 64QAM to 256 QAM, you need to increase your downstream power by about +7dBmV. This can be done at the CMTS or by removing attenuation on the forward path. However, and especially in older DWDM networks, you need to ensure by doing this you dont overload the forward path lasers.
I'm not an RF guy. Which command can I use to increase 7dBmv on a Cisco uBR7200? What happens if I don't do that? Also, my CMs are going to be offline for a moment?
You should not increase your down stream power level without a meter to measure the level coming out of your
combining network. As a general rule you would run your QAM level 6 to 10 dBmV lower than your analog channels.
Or if you have other QAM channels just set your levels the same as those. If you just start increasing your levels without
knowing what they are on your system you risk laser clipping and or distortions. I run mine 6 dBmV lower than my
analogs.
you should be aware, that setting higher QAM modulation will affect DS SNR (on 256QAM it will be lower then on 64QAM channel)
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If you have moved from 64QAM to 256 QAM, you need to increase your downstream power by about +7dBmV. This can be done at the CMTS or by removing attenuation on the forward path. However, and especially in older DWDM networks, you need to ensure by doing this you dont overload the forward path lasers.
I'm not an RF guy. Which command can I use to increase 7dBmv on a Cisco uBR7200? What happens if I don't do that? Also, my CMs are going to be offline for a moment?
Thanks in advance
You should not increase your down stream power level without a meter to measure the level coming out of your
combining network. As a general rule you would run your QAM level 6 to 10 dBmV lower than your analog channels.
Or if you have other QAM channels just set your levels the same as those. If you just start increasing your levels without
knowing what they are on your system you risk laser clipping and or distortions. I run mine 6 dBmV lower than my
analogs.