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<body class='hmmessage'><div dir='ltr'>I'm not sure if it has been mentioned or not as I just joined, but VDSL2 supports Vectoring, which as I understand it is basically scheduling transmission across the different pairs in say a 100 pair bundle. This way, cross talk based interference is run.<div><br></div><div>Quote Paul:</div><div><i>"VDSL2 doesn't really add much functionality to ADSL2 other than the vastly expanded frequency range."</i></div><div><br></div><div>'Frequency Range' literally means <i>Bandwidth</i> ;) How much data you can transport over that - the <i>Bitrate</i>, which is what us IT folks generally mean when we say 'bandwidth' - really just comes down to how clever you are with math. </div><div><br></div><div>For Example:</div><div>Interleaving in ADSL2 allows you to dedicate less of your bitrate to error correction, and hence make available more bandwidth.</div><div><br></div><div>Vectoring in VDSL2 allows the DSLAM some control over how much noise each pair will be subject to. Imagining we have Pairs A,B,C,D in a flat ribbon. Vectoring would ensure that Pairs A&C and B&D Transmit at the same time, but never A&B and C&D. Because of this, each individual pair is subject to less crosstalk, and hence more bandwidth is usable over the same physical medium, and a higher bitrate can be achieved by increasing the width of your modulation scheme (eg, moving from 256 Bins to 512 Bins as in ADSL2->2+) or changing the complexity of your scheme (eg, ADSL1->ADSL2).</div><div><br></div><div>Sorry If I've repeated someone,</div><div><br></div><div>Cheers,</div><div><br></div><div>Jarrad</div><div><div><br></div><div><br><div><hr id="stopSpelling">Date: Fri, 12 Sep 2014 18:03:52 +1000<br>From: pbrooks-ausnog@layer10.com.au<br>To: ausnog@lists.ausnog.net; jeremy@visser.name<br>Subject: Re: [AusNOG] Strange ADSL problem - troubleshooting / diagnosis advice wanted<br><br>
<div class="ecxmoz-cite-prefix">On 10/09/2014 3:28 PM, Jeremy Visser
wrote:<br>
</div>
<blockquote cite="mid:540FE199.9070408@visser.name">
<pre>On 10/09/14 14:39, Paul Brooks wrote:
</pre>
<blockquote>
<pre>ADSL2+ is supposed to re-train to a new sync rate seamlessly without
packet drops, whereas the older ADSL1 had to effectively drop the
line, re-sync, generate a new bitfield table per tone to cope with
changes to background noise and cross-talk that caused a need for a
re-sync.
</pre>
</blockquote>
<pre>I thought that was a feature of VDSL2, not ADSL2+.
I’d be interested to see a source on that as happy to be wrong.</pre>
</blockquote>
<br>
Its actually goes back to ADSL2:<br>
<br>
G.992.5 Jan 2009 ADSL2+<br>
<br>
<a class="ecxmoz-txt-link-freetext" href="https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.992.5-200901-I%21%21ZPF-E&type=items" target="_blank">https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.992.5-200901-I!!ZPF-E&type=items</a><br>
<br>
<br>
Page 'ii':<br>
This Recommendation defines several optional capabilities and
features:<br>
– transport of STM and/or ATM and/or Packets;<br>
– transport of a network timing reference;<br>
– multiple latency paths;<br>
– multiple frame bearers;<br>
– short initialization procedure;<br>
<b>– dynamic rate repartitioning;</b><b><br>
</b><b>– seamless rate adaptation;</b><br>
- extended impulse noise protection;<br>
- erasure decoding;<br>
- virtual noise;<br>
- impulse noise monitor.<br>
"<br>
<br>
G.992.3 April 2009 ADSL2:<br>
<br>
<a class="ecxmoz-txt-link-freetext" href="https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.992.3-200904-I%21%21ZPF-E&type=items" target="_blank">https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.992.3-200904-I!!ZPF-E&type=items</a><br>
<br>
Page 'ii':<br>
"This Recommendation defines several optional capabilities and
features:<br>
• transport of STM and/or ATM and/or Packets;<br>
• transport of a network timing reference;<br>
• multiple latency paths;<br>
• multiple frame bearers;<br>
• short initialization procedure;<br>
<b>• dynamic rate repartitioning;</b><b><br>
</b><b>• seamless rate adaptation;</b><br>
• extended impulse noise protection;<br>
• erasure decoding;<br>
• virtual noise;<br>
• impulse noise monitor."<br>
<br>
"Relative to Recommendation ITU-T G.992.1, the following PMD-related
features have been added:<br>
• New line diagnostics procedures available for both successful and
unsuccessful initialization<br>
scenarios, loop characterization and trouble-shooting.<br>
<b>• Enhanced on-line reconfiguration capabilities including
bitswaps and seamless rate adaptation.</b><b><br>
</b><b>• Optional short initialization sequence for recovery from
errors or fast resumption of operation.</b><b><br>
</b><b>• Optional seamless rate adaptation with line rate changes
during showtime.</b>"<br>
<br>
Clause 8.16:<br>
"8.16 On-line reconfiguration of the PMD function<br>
On-line reconfiguration of the PMD function is intended to allow
changes in the control parameters<br>
without interruption of service and without errors (i.e., bitswap,
dynamic rate repartitioning and<br>
seamless rate adaptation)."<br>
<br>
VDSL2 doesn't really add much functionality to ADSL2 other than the
vastly expanded frequency range.<br>
<br>
cheers...<br>
<br>
Paul.<br>
<br>
<br>
<br>
<br>
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