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Long Reach VDSL2 details

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ejs:
There are a few more details about the proposed Long Reach VDSL2 (LR-VDSL) in the recently published Openreach consultation document.

The most interesting thing I learned was that it is not going to be merely using existing VDSL2 specifications, there are new amendments to the G.993.2 and G.993.5 ITU documents expected to be approved in late 2017 or 2018.

--- Quote ---Changes to the VDSL protocol to enable it to synchronise on long loops and to ensure VDSL always outperforms ADSL2+ from the exchange.
--- End quote ---

This means the current LR-VDSL trials are not quite using the same technology as what it will ultimately use.

Apparently most vectoring ready modems should be firmware upgradeable to support the new LR-VDSL changes.

I'm assuming that reference to ADSL2+ also includes outperforming ADSL2 from the exchange.

WWWombat:

--- Quote from: ejs on May 14, 2017, 08:38:18 PM ---This means the current LR-VDSL trials are not quite using the same technology as what it will ultimately use.

--- End quote ---

I recall that Openreach showed graphs of the potential improvements - and they had 2 variants of LR-VDSL. The 2nd, better, variant was theoretical ... so I guess that related to future spec changes.

I'm trying to figure how to ever guarantee better performance than exchange-based ADSL2+. Presumably you have to at least emulate ADSL2+ in the lower bands, or (at the very least) mimic the transmission power and bit allocation rules. That probably affects power masks downstream, and UPBO upstream.

aesmith:

--- Quote from: WWWombat on May 14, 2017, 09:18:53 PM ---I'm trying to figure how to ever guarantee better performance than exchange-based ADSL2+.
--- End quote ---

Are they trying to?   I thought the idea might be for BT to be able to decommission all DSL from the exchanges, and serve everything from the cabinets.

ejs:
They need to migrate everyone on the LR-VDSL cabinet to FTTC (either LR-VDSL or ordinary), otherwise the LR-VDSL signals would adversely affect the ADSL signals from the exchange. So if they are going to do mandatory migrations for everyone on the cabinet, they don't want anyone to end up with lower speeds. The consultation document is also about the particulars of organising the migrations with the CPs.

WWWombat:

--- Quote from: aesmith on May 19, 2017, 08:01:46 PM ---I thought the idea might be for BT to be able to decommission all DSL from the exchanges, and serve everything from the cabinets.

--- End quote ---

I don't think that BT has enough ports in the cabinets for this to happen generally across the country. And, in any case, BT don't own all the DSL equipment in the exchanges.

When BT want to provide LR-VDSL, it will have to be targeted at specific cabinets - and those specific cabinets will have to have enough ports to migrate all ADSL.

Passing thought: I get a feeling that we've recently seen a lot more Huawei-288 cabinets, relative to the smaller ones, than was seen in the commercial rollout. I wonder if this kind of migration has already been budgeted for?

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