Vplus

Anyone heard of Vplus?

It seems to be a proposal by Alcatel to fit between VDSL2's 17a profile and G.fast, with the main focus on loops of up to 400m, giving aggregate speeds of 200-300Mbps.

One drawback of deploying G.Fast (in the future) is the fact that it has to avoid the 17MHz of spectrum used by VDSL2, so as to not interfere. Big problem...

Ironically, profile 30a of VDSL2 has a similar problem... it cannot work at the same time (in the same bundle) as 17a systems, because it uses frequencies in a different way (each tone is twice as wide as today's 4.3125 kHz). It'd probably interwork with today's 17a systems, but wouldn't work with tomorrow's vectoring systems.

Gplus overlays 17a with identical frequency use, and extends up to 30MHz. Of course it uses vectoring as standard.

I wonder if this will fly at all? Given the strong takeup of 17a systems, I suspect it could be a better step than adding the standard 30a profile. Might also be useful in FTTRN; I suspect line distances there will suit this better than G.fast.

http://www2.alcatel-lucent.com/techzine/vplus-gets-v...

http://blog.thinkbroadband.com/2014/10/g-fast-shows-...

G.Fast co-existing with VDSL2 in the loop, spectrum plot shows frequencies used

Current FTTrN plans revolve around VDSL2 simply because its tried and tested and available in volume.

The scope shows co-existence, but only because the G.fast line isn't using the first 20MHz - which is where it would carry the highest volume of data if it could.

Didn't the data released from the BT trial show the reduction in speeds when the lower part of the spectrum went unused? I'm pretty sure...

As far as I can make out from the Vplus stuff is that a Vplus subscriber could use that same spectrum at the same time as a near neighbour (in the bundle) uses VDSL2 17a.

Agree on FTTRN as it stands. Once they've sorted power out, anyway.

That photo is from the lab where they do the BT trial and the speeds mentioned by them are using that sort of waveform.

I found the trial results I was talking about ...

It could be found as one of the presentations I mention in this thread. Unfortunately, those documents have been removed, so I only have the versions I downloaded earlier in the year.

One bar chart (slide 7) shows speeds for the three different trial lines, each with results from 3 different amounts of spectrum: 23-88MHz, 23-106MHz and 2-106MHz.

On the 19m line, the results were 490Mb, 580Mb and 720Mb respectively.

The non-use of 21MHz is how they get G.fast to co-exist with VDSL2 17a (while always avoiding the bottom 2MHz for ADSL2+), but the consequence is that it reduces (G.fast) speeds by a hefty amount.

Edit: I found an alternative copy of the BT G.fast trial results: Pages 7 and 8 of
http://uppersideconferences.net/g-fast-summit2014/pr...

Edited by deleted (Thu 27-Nov-14 19:08:51)