2gig + on Docsis 3.1

[Ash_]

Is there a plan for VM to upgrade its none FTTP customers to 2gig in the near future?

The theoretical max of Docsis 3.1 is 10gbps so I'm curious if they ever will or is 1gig the max we are ever going to get. The rollout of FTTP XGS-PON is underway but it ain't going to be anytime soon for me and I could do with a bit more speed on the upload. 

The XGS-PON packages allow symmetrical upload and download speeds which I need but isn't available to Docsis 3.1 routers. What I find interesting is the Hub5 has the ability to bond more channels but they are not using them. 

[Cardiffman282]

See https://community.virginmedia.com/t5/Networking-and-WiFi/Hub-5-ready-for-2-10Gbps-DOCSIS-3-1-support... 

[Tudor]

Quick answer, never. Too costly.

[unisoft]

---

@Tudor wrote:

Quick answer, never. Too costly.

---

In a number of areas it's ready to go, most of the upstream capacity work was done for GIG1 for example, and they won't boost upload too much anyway. It all depends whether they think XGS-PON upgrade via Project Mustang is going at fast enough rate to alleviate need to offer 2gbps on HFC/RFoG. RFoG has its own problems anyway with upload for the GIG1 service. I think they are sitting it out at the moment as not much demand for 2gbps, and their Nexfibre is already offering it via full fibre FTTP.

[IPFreely]

---

@Tudor wrote:

Quick answer, never. Too costly.

---

What will be costly to provide 150 or 200 Mb upload on the cable network? I imagine the RFoG stuff will go straight to XGSPON.

[pete_at_home]

Just for clarity, the theoretical limit for D3.1 is not 10Gbps.  D4.0 provides for additional OFDM channels and more bandwidth on the cable plant.  The actual capacity depends on a number of factors:

RF Bandwidth on HFC network.  Right now VM HFC varies but is predominately 1Ghz maximum.  With the number of Video channels, this limits the downstream Docsis capacity to 32 D3.0 channels, plus 2 OFDM (192Mhz & 96Mhx wide).  Consequently the max cable bandwidth is approximately 2.5Gbps - hence why they offer 1100Mbps to the modem which is shared by all customers on that service area.  (it is technically possible to get 3.2Gbps capacity if the RF network is extended to 1.2Ghz, but the modems cannot support it !!)

CMTS Type & software version:  99% of the CMTS in Virgin are 1.2Ghz capable, but the HFC plant is not, so they limit the downstream channels to 1Ghz.  Also the CMTS only supports 2 OFDM.   There is an emerging standard called "Docsis 3.1 Plus or extended" which enables additional OFDM channels but currently it's limited to LAB CMTS software only.

Modem Tuner Capability:  Pretty much all the D3.0 modems on the planet only have tuning capability for 32 x D3.0 plus 2 x D3.1 channels, so rolling out D3.1-Plus would require new modems !!

VM02 roadmap:  VM decided to roll-out XGS-PON rather than upgrade their docsis networks to D4.0.  New build areas are being done first, but overbuild in legacy areas will follow.   Other operators around the world are doing D4.0 which requires CMTS, Amplifier & Modem upgrades.  It simply isn't gonna happen in the UK !!

[nodrogd]

On the DOCSIS network VM has to accommodate their broadcast TV services as well as Broadband. This uses considerable resources that could otherwise be redeployed for Broadband. Also on the HFC parts of the network there would be increasing contention issues where there are still around 500 customers sharing each network segment.

[IPFreely]

---

@nodrogd wrote:

On the DOCSIS network VM has to accommodate their broadcast TV services as well as Broadband. This uses considerable resources that could otherwise be redeployed for Broadband. Also on the HFC parts of the network there would be increasing contention issues where there are still around 500 customers sharing each network segment.

---

As long as the network isn't full TV being there isn't a problem is it? Is the cable network completely full? A higher speed product  with no other changes wouldn't it mean more capacity is needed more than fewer customers on each segment? Unless the network is completely full that shouldn't be too expensive?

[gitty]

---

@pete_at_home wrote:

RF Bandwidth on HFC network.  Right now VM HFC varies but is predominately 1Ghz maximum.  With the number of Video channels, this limits the downstream Docsis capacity to 32 D3.0 channels, plus 2 OFDM (192Mhz & 96Mhx wide).  Consequently the max cable bandwidth is approximately 2.5Gbps - hence why they offer 1100Mbps to the modem which is shared by all customers on that service area.  (it is technically possible to get 3.2Gbps capacity if the RF network is extended to 1.2Ghz, but the modems cannot support it !!)

A 192 MHz OFDM channel is ~1500 Mbps @ 1024-QAM and ~1800 Mbps @ 4096-QAM.
A 96 MHz channel is ~half that.
32 x SC-QAM (8 MHz) @ 256-QAM is ~1600 Mbps

Current 3.1 modems can access up to ~5 Gbps (shared capacity, not offered speed tier), if enough spectrum is allocated to DOCSIS.

About the 10 Gbps: A single OFDM can do up to ~1900 Mbps (best configuration @ 4096-QAM). 3.1 can fit five channels between 258 MHz and 1218 MHz (depends on the hardware). That gives ~9.5 Gbps. It exceeds 10 Gbps, if FEC is included.

[IPFreely]

Will answer myself as this one has drawn a blank. There are only active carriers up to 750 MHz at the moment. 258 MHz available on 1 GHz plant so a full 192 carrier shiny new and the current 92 MHz carrier gets a bump to 158 wide. 258 MHz will provide more than 2 Gbps of new capacity, easily enough.

500 modems on a segment they are light users. Average is less than half that. The extra capacity to handle burst will be plenty.

VM have been seeding 3.1 devices into the network for months to relieve the 3.0 channels with a view to using their spectrum.

They may also place an OFDMA carrier underneath the existing SC-QAMs. Won't be great but 20-ish Mbps that wasn't there before.

Drop the top two SC-QAMs to enlarge the OFDMA block there, move from 5 * 25 + 1 * 70 = 195 Mbps powering a 110 Mbps tier to 3 * 25 + 1 * 20 + 1 * 170 = 265 Mbps. Might be fine for 220, should be more than adequate for 160.

Areas with mid-split, return paths going to 85 MHz, are good to go regardless: 20 MHz free waiting for OFDMA and likely at a higher order modulation than 256QAM.