2gig + on Docsis 3.1
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 goin...
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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 !!
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.
Yes in theory the CM could access 5Gbps of network capacity, but dropping the video QAM's is not on their roadmap.
Although they are rolling out the Sagem Hub5, most of the 3.1 modems are Hub4 which has a 2.4Gbps limit in the E-router chip. They certainly could rollout a 2Gbps service but that would depend on the business case & viability to deliver it in congested areas.
The 5 x OFDM could work, but not with any of the current modems. Also none of the CMTS in VM can support this, plus it would require all legacy Hub3 to be swapped out, so they will not do it !!
As far as VM is concerned, XGS-PON is their future. The reason they deployed RFoG was so they could re-use the fibres for XGS-PON as the OLT's are deployed, but this will not happen until they start rebuilding the legacy HFC areas.
pete_at_home wrote:Yes in theory the CM could access 5Gbps of network capacity, but dropping the video QAM's is not on their roadmap.
As far as VM is concerned, XGS-PON is their future. The reason they deployed RFoG was so they could re-use the fibres for XGS-PON as the OLT's are deployed, but this will not happen until they start rebuilding the legacy HFC areas.
No need to drop the video QAMs in full or even at all really. You said the vast majority of areas were 1 GHz plant - they're only loaded up to 750 MHz and some have 36 or even 40 SC-QAMs for load balancing of 3.0 modems. FYI: video QAMs have been progressively dropped for ages with moves to MPEG 4 and more channels to IPTV.
Moving RFoG to XGSPON isn't dependent on HFC areas and millions of premises of HFC have already been overlaid with XGSPON: the delay isn't the XGSPON build it's the billing and provisioning systems being unable to handle cable and XGSPON to the same address.
Tons of HFC cabinets with FTTP L3 and L4 cabinets next to them connected to active OLTs waiting for release in the UK from Oxford to Chichester to Coventry, Liverpool, Glasgow, etc, etc. Millions of premises of HFC have had XGSPON overlay built and with XGSPON OLTs going into the field there is no dependence at all on HFC for RFoG areas to receive XGSPON. They could be done with nothing more than an SD1i power pillar, a POP-A cabinet with an OLT in it, some duct, a core drill into an existing chamber and some optical co-existence elements if they really wanted to. The power budget is more than fine.