<div dir="ltr">There's a couple of papers available on the IEEE around FEXT with regards to ADSL2+ services. More specifically, how much of an impact cross-talk can have within an environment where a large number of surrounding pairs in a bundle are also used to provide an ADSL2+ service.<div>
<br><div><a href="http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4446136">http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4446136</a></div><div><br>From what I understand, FEXT could start to be an issue if a large number of adjacent xDSL services were deployed with out the magic of 'vectoring' due to this cross-talk. This having been said, I could be way off the mark here (I haven't even had my morning coffee yet!) in which case I'm happy to be corrected :)<br>
<br><br></div></div><div class="gmail_extra"><div class="gmail_quote">On Fri, Sep 13, 2013 at 8:46 AM, Mike Trewartha <span dir="ltr"><<a href="mailto:miketrewartha@gmail.com" target="_blank">miketrewartha@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div>With the change in loop lengths, what is the likelihood of some bodies current decent (ie. 18mbit+) ADSL2+ sync speeds dropping once FTTN is deployed?<br>
<br><br>Regards, Mike. </div><div><br>Sent from my iPhone</div><div class="im"><div><br>On 13/09/2013, at 8:32 AM, Paul Brooks <<a href="mailto:pbrooks-ausnog@layer10.com.au" target="_blank">pbrooks-ausnog@layer10.com.au</a>> wrote:<br>
<br></div></div><blockquote type="cite"><div><div class="im">
<div>On 13/09/2013 7:08 AM, Guy Ellis wrote:<br>
</div>
<blockquote type="cite">
<div>Paul,<br>
<br>
In response to your challenge (Exercise for the reader - work
out how VDSL2 would be any different)...<br>
<br>
In contrast to the current ADSL2+ network, there are 3 big
differences with the proposed VDSL2 FTTN deployment - <br>
(i) shorter loop lengths (700-800m) <br>
(ii) vectoring (crosstalk--)<br>
(iii) bonding (speed++)<br>
<br>
While such a VDSL2 network is not as good as fibre, it's no
where near as bad as the current ADSL2+ network.<br>
Right now some poor folks are on 6km loop lengths, there's
plenty of crosstalk and getting bonding working is a challenge.<br>
</div>
</blockquote>
You can forget about pair bonding in the broader plan - I sincerely
doubt the budget or street cabinets will be big enough to build two
ports for every dwelling.<br>
<br>
My point was that - without vectoring - the VDSL2 chart would look
much the same.<br>
<br>
Sure the axis labels would change - distances to 5km become
distances to 800 metres, bandwidth tops out at 120 Mbps instead of
24 Mbps - but the shape of the chart would look much the same. A
negligable proportion getting the full 'up to' speed, roughly 30% of
people getting speeds down to 50% of the "up to" limit, and a large
hump majority of people down the low end getting about 10 - 15 Mbps
- probably better than the ~4 Mbps they might get now with ADSL2,
but not really up to the new benchmark.<br>
<br>
That leaves vectoring as the major difference - which will make
speeds more predictable and push a lot more services to the right to
higher speeds, reduce the width of the fuzzy cloud in the second
diagram, but still won't deliver 50 Mbps further than about 750
metres.<br>
<br>
<br>
Anyway, back to the original topic - I was looking for ADSL2+ data
- anyone?<br>
<br>
<br>
<br>
</div><blockquote type="cite"><div class="im">
<div> <br>
Regards,<br>
- Guy.<br>
<br>
<br>
<br>
<br>
On 12/09/2013 12:17 PM, Paul Brooks wrote:<br>
</div>
</div><blockquote type="cite"><div class="im">
A recent Ofcom (UK) report has a very interesting chart of
ADSL2+ line speeds:<br>
</div><div>
<div>
<div>
<p class="MsoNormal"></p><div class="im"> Ofcom Infrastructure Report 2012
Update<br>
<a href="http://stakeholders.ofcom.org.uk/market-data-research/other/telecoms-research/broadband-speeds/infrastructure-report-2012/" target="_blank">http://stakeholders.ofcom.org.uk/market-data-research/other/telecoms-research/broadband-speeds/infrastructure-report-2012/</a><br>
<a href="http://stakeholders.ofcom.org.uk/binaries/research/telecoms-research/infrastructure-report/Infrastructure-report2012.pdf" target="_blank">http://stakeholders.ofcom.org.uk/binaries/research/telecoms-research/infrastructure-report/Infrastructure-report2012.pdf</a><br>
Figure 4 on page 11:<br></div>
<mime-attachment.png><br>
<p></p><div class="im">
<p class="MsoNormal">This chart is effectively the result
of the ADSL line-sync/attenuation curve combined with
the increasing area of circles of increasing radius
around the exchange - and demonstrates very clearly why
so many people get low ADSL2+ line speeds.<br>
(Exercise for the reader - work out how VDSL2 would be
any different)<br>
<br>
</p>
Also scatter-plots of sync-speed with line-length, as per
Figure 8 from another UK report:<br>
<br></div>
<mime-attachment.png><div class="im"><br>
<p class="MsoNormal">Now every DSLAM network operator can
put together similar charts - but I'm not aware of any
stats for Australian networks, apart from the heat maps
put out by iiNet and the <a href="http://adsl2exchanges.com.au" target="_blank">adsl2exchanges.com.au</a> site,
which aren't quite what I'm looking for.<br>
</p>
<p class="MsoNormal">For all you DSLAM operators - I would
be very interested in putting together similar charts
for the Australian networks, to see how our copper loop
network varies from the UK network. If anyone is willing
to share data or statistics, I'm very interested in
pulling together similar Australian charts - on a
non-identified, aggregated, anonymised basis if you
wish.<br>
Please contact me off-list - thanks.<br>
</p>
<p class="MsoNormal">Paul.<br>
</p>
<p class="MsoNormal"> <br>
<br>
</p>
</div></div>
</div>
</div><div class="im">
<br>
<br>
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<br>
<br>
<pre cols="72">--
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