| Attachment | Size |
|---|---|
 Cable modulation-profile.txt | 9.66 KB |
| running-config.txt | 1.96 KB |
Dear,
Could you please tell me the best cable modulation-profile in the attached file for the following situation.
- CMTS uBR10K with PRE-4 and MC20X20V
- Attached as configured the interface cable. 4 channels 3.2mhz standard qpsk
- Around 100 cable modems per channel 1.x, 2.0 and 3.0
Due to upstream consumption I need to increase the modulation to 16qam. From the examples in the attached file what is the best option? Do I use in all upstream or can I use only the two upstream higher? If by chance does the SNR get high, the modality returns automatically to qpsk until the snr improves?
Thank you, Flavio.
What about moving to 6,4MHz A-TDMA Upstreams? Move forward to a Docsis 2.0/3.0 service?
Any chance to test upstream profiles? We use profile 222.
In the future I intend to take all cable modems docsis 1x from the network but at the moment it will not be possible because I still have many cables 1x in the network.
You have a few choices
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For increasing the capacity :
1) Change all the US from tdma to tdma-atdma, and then switch to a higher QAM eg robust-mix-qam.
You are limited to 3.2MHz width in this case though.
But enabling mixed-mode is a good idea regardless, as the D2 and D3 modems are a bit knobbled in tdma mode.
2) Change some of the US to atdma mode, and consider running them at 6.4MHz width and a higher QAM
Leave some of the US set to tdma or tdma-atdma mode so the old DOCSIS 1.x junk can still work (at a reduced bandwidth)
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For width/qam fallback :
* Create a spectrum group for each US channel
* Set primary channel width and a fall back channel width
* Set primary modulation and a fall back modulation
This way the CMTS will monitor the upstream and if its clean will operate the channel wide and high qam.
If there is noise it will auto drop the width and/or qam.
If the noise goes away the width and qam will be auto restored.
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To give you a feel for the capacity differences :
* 3.2width 16qam = aggregate 8.9Mbps available
* 3.2width 64qam = aggregate 13.3Mbps available
* 6.4width 16qam = aggregate 17.8Mbps available
* 6.4width 64qam = aggregate 26.7Mbps available
Don't have the figures handy for QPSK, but its a lot less than any of above combos