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Problems with CM1150V upstream on Comcast Xfinity
There are a number of past threads (now closed, or I'd be replying to them) about problems people have had with the upstream path on a CM1150V with Comcast Xfinity. I believe I understand the underl...
sleat wrote:So it makes sense that the BGA3131 is designed to operate up to 205MHz. However, notice the sentences I've highlighted. In my case, Comcast is running four upstream QAM channels (no upstream OFDM) at frequencies of 173MHz, 273MHz, 303MHz, and 367MHz. So not only are they asking the CM1150V do do something it was never designed to do, they are blatantly violating the DOCSIS 3.1 spec!
sleat I've read this thread multiple times (having my own Upstream Issues!) and took this at face value;
but only just spotted this fundamental error in your analysis ..........
The Comcast Upstream frequencies are not as you indicate, you are a factor of 10 off
i.e. they are 17.3MHz, 27.3MHz, 30.3MHz and 16.7MHz
i.e. 17300000 Hz (5 zeros) = 17,300,000Hz or 17.3MHz
So actually operating well within the DOCSIS 3.1 Spec and well within the design capability of the Chipset.
As I've said I'm having my own Upstream Issues with my CM1150V (and actually got a replacement from Netgear) and there is definitely a problem - but it's not because it's being asked to operate outside its spec.
Postscript:
It's also curious that I'm paying for 17Mbps upstream (and that's about what I get when everything is working), but Comcast is running four QAM channels at 5120 symbols/sec each. Even if they're only running QAM16 (i.e., 4 bits/symbol), that's 20.48Mbps raw signalling rate per channel, so 17Mbps throughput seems about right for one channel. If they would just give me one QAM16 channel below 205MHz, I'd probably be happy.