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<div class="moz-cite-prefix">I think just taking distance into
account is very simplistic view of things. Im not sure what state
the copper is in the UK. However in Australia there are other
things to consider other then distance. <br>
<br>
Joints. - The number of joints in an adsl loop dramatically
decrease SNR and increase loss. The type of joint is also of
interest. Insulation displacement is far better then non soldered
pin strip for example. <br>
<br>
Cable type / gauge. - Cable type and gauge varies greatly. There
is far less loss on higher gauge cable. However most of the time
gauge changes at every joint this produces all sorts of nasty
results from impedance mismatches to standing waves. <br>
<br>
Bridge Tap - xDSL's worst enemy and Telecom stalwart from the
1970-80's bridged taps are responsible for most of the SNR
problems on xDSL. I remember pulling these things out for a
living when attempting to reduce the BERT on Auspac and X25
services back in the 80's (now im showing my age) These things
are going to be the biggest problem for the new VDSL/FTTN
environment. Technicians paid per completed service will not have
a lot of incentive to go find and remove these so the rule of
thumb will be. "Does it work at any speed, Yes. Good next job" .
Just as it is now. <br>
<br>
Customer premiss cabling - Although this isn't some time's our
problem as ISP's it becomes our problem through support man hours
and unhappy customers, How many customers have you had a
discussion with about that old K-Mart non twisted pair 20m
extension cord and those old disused 5 parallel sockets (more
bridged tap's). It cant be my extension cord it worked yesterday.
<br>
<br>
<rant><br>
My experience is the people working in this space, maintaining the
Telstra CAN (or customer area network) have very poor
understanding of these issues and the ones that do dont have the
time to care when they apply the pizza delivery pay model to these
guys. None of this will change, price pressure and time frame's
will make a network that needs serious TLC even worse. I have a
customer that has been waiting 7 months for copper that was
damaged during a road works project to be replaced. 3G for 7
months. Good luck with that. <br>
<br>
VDSL has it's place. In buildings - however we spend serious time
going to customers sites in buildings only to find that a
technician with a time pressure was there that morning and stole
what they thought was a spare pair for a phone service. Just
because they could hear no dial tone on it. No dial tone it must
be free. <br>
<br>
Welcome to the brave new - old world of data over copper.<br>
</rant><br>
<br>
<br>
<br>
On 12/09/13 12:17 PM, Paul Brooks wrote:<br>
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<blockquote cite="mid:52312456.90609@layer10.com.au" type="cite">
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A recent Ofcom (UK) report has a very interesting chart of ADSL2+
line speeds:<br>
<div class="moz-forward-container">
<div class="WordSection1">
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<p class="MsoNormal"> Ofcom Infrastructure Report 2012
Update<br>
<a moz-do-not-send="true"
href="http://stakeholders.ofcom.org.uk/market-data-research/other/telecoms-research/broadband-speeds/infrastructure-report-2012/">http://stakeholders.ofcom.org.uk/market-data-research/other/telecoms-research/broadband-speeds/infrastructure-report-2012/</a><br>
<a moz-do-not-send="true"
href="http://stakeholders.ofcom.org.uk/binaries/research/telecoms-research/infrastructure-report/Infrastructure-report2012.pdf">http://stakeholders.ofcom.org.uk/binaries/research/telecoms-research/infrastructure-report/Infrastructure-report2012.pdf</a><br>
Figure 4 on page 11:<br>
<img id="_x0000_i1025"
src="cid:part3.01060803.02030706@spectrum.com.au"
height="350" border="0" width="593"><br>
</p>
<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>
<img src="cid:part4.02010709.07050405@spectrum.com.au"
alt="" height="240" width="553"><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 adsl2exchanges.com.au 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>
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