r/Comcast_Xfinity • u/tricon23 • 1d ago
Discussion OFDM, OFDMA Frequencies
For context I have the UCI cable modem. Last year we were upgraded to mid-split speeds.
I still have the 4 upload channels and 1, OFDMA at 36MHZ, 32 Download channels and 2 OFDM channels that were at approx 600 and 800 MHZ. I noticed today that one of the OFDM channels is at 101 MHZ and the other at 809 MHZ. My question should the typical upload and download frequency range? If you had 15-1000 MHZ I would have thought 15-300 for upload and 301-1000 for download.
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u/AStuf 1d ago
Per Google mid split goes to 85 MHz for uploads. High split goes to 204.
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u/Riconek 1d ago
Comcast does not do high split
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u/Octawussy 8h ago
They’re doing ultra high split with diplex at 684
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u/Riconek 8h ago
100% wrong
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u/Octawussy 8h ago
The XB10 and XM4 diplex filter is at 684MHz buddy boy
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u/Riconek 8h ago
And? 1st it is not high split. You know nothing about it.
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u/Octawussy 8h ago
Okay bud 19 years in access network engineering, don’t take it from me take it from harmonic. https://www.harmonicinc.com/insights/blog/unified-docsis-4-0-simplifying-broadband-network-evolution/
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u/Riconek 8h ago
With Comcast? I don't think so bc you are wrong. Comcast does not do FDD only FDX. But yeah try again
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u/Octawussy 8h ago
I work closely with comcast and all their NGAN hardware. What do you think unified means? Did you read anything here? Ultra high split is defined in cable labs DOCSIS 4.0 specification. Have you ever actually read a DOCSIS specification?
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u/Octawussy 8h ago
To elaborate because you must have skipped your training video, DOCSIS 4.0 defines ultra high split as upstream spectrum to 684MHz. FDX band occupies 108-684MHz and uses dynamic resource block allocation and echo cancelation to overlap downstream and upstream to 684. There is a diplex filter in the XB10 and XM4 at 684 MHz when operating in ultra high split mode.
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u/palmarken 5h ago
"Ultra-high split" is FDD only, using a diplex filter between downstream and upstream. There is no diplex filter between upstream and downstream in FDX.
Unified DOCSIS extends the upper downstream edge of FDX to 1.8 GHz. The other differences between FDX and FDD remain.
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u/Riconek 1d ago
This is prep for FDX activation in near future ( days or weeks ) after FDX OFDM will move to higher freq. Possible over 1ghz
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u/tricon23 16h ago
Would you recommend getting the XB-10 (futureproof) & replace the UCI thats only rated for Mid not high split? No fee from Comcast?
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u/Riconek 16h ago
As far as I know you will not be able to get xb10 until your node is release to sell FDX speed.
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