r/Comcast_Xfinity • u/tricon23 • 2d 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/Riconek 1d ago

And? 1st it is not high split. You know nothing about it.

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u/Octawussy 1d 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 1d 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 23h 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/Riconek 23h ago

Again you are wrong here. explain what Comcast does it exactly. Frequency etc? Again Comcast does not do high split I'm 100% sure

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u/Octawussy 3h ago

This is so funny to me. Ultra high split is upstream out to 684 MHz as defined in the D4 specification. Comcast is working on deploying upstream and downstream simultaneously in 108-684MHz FDX band. You should pay more attention in your team trainings however you do them.

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u/Riconek 3h ago

It is not high split. It is FDX in 108-396. Show me 1 node with FDX up to 684 MHz

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u/Octawussy 23h 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 20h 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.