Found a nice PDF on VDSL and profile speeds

If anyone would like to have a look through

pretty nice info either way if you're interested

PDF -> http://www.filefactory.com/file/cd62d8d/n/2957_file_...

screeny -> http://i55.tinypic.com/2qd2wkp.png

Edited by epyon (Fri 02-Sep-11 01:52:55)

I hate those extremely irritating download sites...

A simpler place to access can be found at this direct link instead.

The document has been seen before on here - the graphs of distance vs speed are probably on the optimistic side; likely they don't take into account real-world deployments with significant amounts of crosstalk & interference.on non-perfect lines.

In reply to a post by WWWombat:

I hate those extremely irritating download sites...

MediaFire seems to be okay, no download delay or 'encouragement' to pay for premium downloads. Wonder why it is not used more often...

DrT

Thank you for the direct link - I was being driven mad

Have seen it or something similar before

Thanks for that. Interesting to see the 17A graph projections.

with my line length of 350 meters with 0.5 copper I should get good speeds on 17a

what is the current profile in use? How does it vary?

Certainly wasn't on anything to do with Be.

I remember vaguely posting something like this a while back.

Memory fading, getting old, might have been that you saw.

In reply to a post by orly:

what is the current profile in use? How does it vary?

I believe the current profile BT use is 8C.

In reply to a post by orly:

what is the current profile in use?

Doesn't your comparison chart tell you this

Nope...it's not that good

It was either on here on Whirlpool

And i know what you mean about memory failing

This pdf is from 2006, the one I have been using is from 2009 by a company called Zhone. There is quite a noticeable difference between the graphs from these 2 documents.

I've estimated my line length to be 2100ft, according to your PDF the maximum I can get is:
8b profile: 40Mb down / 15Mb up
17a profile: 60Mb down / 20Mb up
30a profile: 60Mb down / 20Mb up

On the more recent PDF it says:
8a-d profile: 80Mb down / 20Mb up
17a profile 95Mb down / 50Mb up
30a profile: 80Mb down / 40Mb up

So either VDSL2 technology has progressed quite a bit in those 3 years or some manufacturers have better VDSL2 technology and are able to extract more out of the line.

Are these real measurements or estimates? Factors other than distance might also account for the difference, crosstalk and wire type being particularly important.

Given that recovery of the data is quite a heavy-duty signal processing task, differences or refinement in embedded algorithms and evolution of processing power of the on-board ASIC/DSP might help to get closer to the theoretical maximum over time.

It doesn't actually say. It just lists white-papers from several years under each page. My guess is they are maximum indoor tests as they say outdoor cabling etc will reduce efficiency through the things you've mentioned.

I just found a new PDF (or new to me, at least) with some predictions on behaviour of the 17a profile under different line conditions (ie different amounts of crosstalk).

It is a PDF from Ikanos study into bonded VDSL2 solutions. The later detail discusses various bonded solutions, but it does start with some useful benchmark figures for unbonded circuits.

The graph on page 8 is the most enlightening: It shows how throughput degrades from a theoretical-best standalone circuit down to multiple co-interfering circuits, and suggests that BT's "up to 80Mbps" solution will be limited to about 300 metres from the cabinet.

Page 14 shows the downstream behaviour of the 12a profile - which ought to be very similar to the 8x profiles (the extra frequencies from 8MHz to 12MHz are only used for upstream).

UNFORTUNATELY...

The graphs are all based on the 998 band-plan, which is asymmetric, tilted towards giving more frequencies for downstream.

Openreach have been using band-plan 997 so far (with profile 8c), which is a more symmetric split between upstream & downstream. If they continue to use plan 997 with profile 17a, I'd guess that the downstream throughput will be lower than shown in the graphs.