Cable Forum - View Single Post

watercooled · 12-04-2020, 13:57

I understand a modem can lock to both SC-QAM and OFDM carriers simultaneously so it's not surprising we still see the standard channels, but I expected to at least see an OFDM block locked too.

I mean in theory they could do gigabit with 32 bonded QAMs but I would have thought it was pushing it if more than a few people signed up to it in one area.

I'm half thinking it's just a GUI bug not showing it rather than it actually not being there.

It's a totally different channel plan though so I don't think the 256QAM SC-QAM channels tell us anything - that's the max constellation size for 3.0 as far as I know?

From what I remember reading, the new LDPC error correction allows (in theory) 4096QAM to be utilised where 256QAM would have been used with Reed Solomon, with similar noise levels and giving similar BER, etc. But 3.1 also allows channels to operate at different modulation rates where necessary.

For what it's worth, I found this as an example of what you'd expect to see on a 3.1 modem locked to OFDM blocks (still using 3.0 upstream though) https://pickmymodem.com/signal-level...1-cable-modem/

Edit: This post and the next one mention it - perhaps it is a firmware thing? But apparently some information is exposed in the network logs rather than being explicitly show on the stats pages. Weird!

12-04-2020, 13:57	#93
watercooled cf.member Join Date: May 2013 Posts: 16	Re: M1000 is available. How to order? I understand a modem can lock to both SC-QAM and OFDM carriers simultaneously so it's not surprising we still see the standard channels, but I expected to at least see an OFDM block locked too. I mean in theory they could do gigabit with 32 bonded QAMs but I would have thought it was pushing it if more than a few people signed up to it in one area. I'm half thinking it's just a GUI bug not showing it rather than it actually not being there. It's a totally different channel plan though so I don't think the 256QAM SC-QAM channels tell us anything - that's the max constellation size for 3.0 as far as I know? From what I remember reading, the new LDPC error correction allows (in theory) 4096QAM to be utilised where 256QAM would have been used with Reed Solomon, with similar noise levels and giving similar BER, etc. But 3.1 also allows channels to operate at different modulation rates where necessary. For what it's worth, I found this as an example of what you'd expect to see on a 3.1 modem locked to OFDM blocks (still using 3.0 upstream though) https://pickmymodem.com/signal-level...1-cable-modem/ Edit: This post and the next one mention it - perhaps it is a firmware thing? But apparently some information is exposed in the network logs rather than being explicitly show on the stats pages. Weird! Last edited by watercooled; 12-04-2020 at 14:15.