More Improvements made to docsis 4.0

Tito79

https://www.lightreading.com/cable-technology/cablelabs-sees-14-gig-speeds-at-latest-docsis-4-0-interop

fmd

If we were to guess the number of OFDM channels that Broadcom’s Unified chip supports…

7 × 192 MHz OFDM @ optimal 4096-QAM settings: 7 x ~ 1.9 Gbps = ~ 13.3 Gbps

The rest is up to SC-QAM. Only 6 OFDM is required by the standard (CMTS/RPD).

fmd

It appers to support 8 OFDM…

The gap between channel 3 and 4 can be used for SC-QAM

hex0101

fmd ~~So 13 Gbps down and 5 Gbps up capacity? Unified 4.0 meaning ESD? Or FDX up to 1.2 and downstream OFDM channels up to 1.8 Ghz?~~

Just saw the mid-split, oops.

fmd

In this context, mid-split just refers to the classic FDX layout, where the legacy upstream is 5-85 MHz. This is what Comcast uses. In this layout, the full duplex band begins at 108 MHz.

In the demo, Harmonic has OFDM channels from 108-684 MHz and 834-1794 MHz.

In regard to Unified. It means two things:
1) A unified device (node/amplifier/modem) supports both FDD (ESD) and FDX.
2) It extends FDX’s downstream from 1.2 to 1.8 GHz.

fmd

Another improvement that Harmonic has been talking about is “Flex FDD”. The modem is FDD, but it doesn’t have a diplex filter (no details about the technical implementation). 1) It can change split at any time. 2) There is no crossover region. How other vendors will greet this option is yet to be seen (using MaxLinear’s FDD chip).

hex0101

fmd XB10 (both Serrcom and Vantiva)/Pebble-2/ARRIS OM6000 (can’t remember the FDX RPD module model) /CommScope FDX Amp/Serrcom FDX Amp all use Broadcom?

fmd

Yep. Only Broadcom makes FDX/Unified chips (at least for now). Broadcom also happens to be the only of the two vendors that make node chips.

It’s possible to make diplexer-less amplifiers without these FDX chips (echo cancellation). Technetix makes one. I can’t say, if Harmonic has a new approach to it.

cypherstream

Do you have a link to the original demo? That picture is still blurry when zoomed in. Can’t read anything on that screen shot.

fmd

Unfortunately not. I tried zooming in during the presentation, but the embedded video in the slide just couldn’t get more clear than that. :-)

fmd

It got increased to 16 Gbps… https://www.cablelabs.com/blog/docsis-4-0-interop-delivers-16-gbps-downstream-speeds

8xOFDM + 25xSC-QAM, I’m guessing. 16 Gbps is about maximum without going above 4096-QAM.

cypherstream

fmd wow past xgs-pon and more than halfway to 25gpon.

Imagine two 25gbps fiber links to the node serving 16gbps out the left two node ports and another 16gbps out the right two node ports.

hex0101

fmd without going above 4096-QAM.

Are current plant conditions currently good enough to run 4096 QAM?

fmd It got increased to 16 Gbps

FDX or ESD? By increasing the downstream to 16 Gbps, your upstream capacity is reduced.

I remember seeing this in a SCTE Tech Expo presentation in 2023:

The presenter also mentioned that DOCSIS 4.0 has beat XGS-PON! DOCSIS 4.0 was doing 10 Gbps down, whereas XGS-PON tops out at around 8 Gbps. DOCSIS 4.0 numbers were counting forward error correction, whereas XGS-PON were not.

cypherstream

hex0101 xgs-PON is 10gbps but yeah I guess that’s if your the only customer and you don’t do FEC!

My cable op is offering 8/8gbps for $122.35/m, but they are using 25gpon.

hex0101

cypherstream My cable op is offering 8/8gbps for $122.35/m, but they are using 25gpon.

Wow, that is a great price! And on 25G-PON, so plenty of capacity!

fmd

hex0101 Are current plant conditions currently good enough to run 4096 QAM?

A lot of it has to do with amplification… How hard the amplifiers are driven, and how low the signal is when it reaches the next amplifier.

The 1.8 GHz booster amplifier is available to the operators, but to what extent will they use it? If they can make it work at a lower modulation, they may just skip it. Fx. Cox said that they won’t pursue 4096-QAM between 1 and 1.8 GHz.

fmd

hex0101 FDX or ESD? By increasing the downstream to 16 Gbps, your upstream capacity is reduced.

That is of course one caveat, upstream and downstream steal from each other, but if the system is made dynamic, there can be times where downstream has access to all of it.

videomatic3

hex0101

hex0101 The presenter also mentioned that DOCSIS 4.0 has beat XGS-PON! DOCSIS 4.0 was doing 10 Gbps down, whereas XGS-PON tops out at around 8 Gbps. DOCSIS 4.0 numbers were counting forward error correction, whereas XGS-PON were not.

Lol. Maybe 1 direction, but if you add up the totals of both directions simultaneously, it doesn’t beat it.

cypherstream

videomatic3 I guess they could do 8/8gbps to make that 16gbps. But yeah thats shared for the node. How deep are they going to push it?