[AusNOG] ADSL2+ line sync data

[Peter Adkins]

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.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4446136

>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 :)


On Fri, Sep 13, 2013 at 8:46 AM, Mike Trewartha <miketrewartha at gmail.com>wrote:

> 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?
>
>
> Regards, Mike.
>
> Sent from my iPhone
>
> On 13/09/2013, at 8:32 AM, Paul Brooks <pbrooks-ausnog at layer10.com.au>
> wrote:
>
> On 13/09/2013 7:08 AM, Guy Ellis wrote:
>
> Paul,
>
> In response to your challenge (Exercise for the reader - work out how
> VDSL2 would be any different)...
>
> In contrast to the current ADSL2+ network, there are 3 big differences
> with the proposed VDSL2 FTTN deployment -
> (i) shorter loop lengths (700-800m)
> (ii) vectoring (crosstalk--)
> (iii) bonding (speed++)
>
> While such a VDSL2 network is not as good as fibre, it's no where near as
> bad as the current ADSL2+ network.
> Right now some poor folks are on 6km loop lengths, there's plenty of
> crosstalk and getting bonding working is a challenge.
>
> 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.
>
> My point was that - without vectoring - the VDSL2 chart would look much
> the same.
>
> 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.
>
> 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.
>
>
> Anyway, back to the original topic  - I was looking for ADSL2+ data -
> anyone?
>
>
>
>
> Regards,
>  - Guy.
>
>
>
>
> On 12/09/2013 12:17 PM, Paul Brooks wrote:
>
> A recent Ofcom (UK) report has a very interesting chart of ADSL2+ line
> speeds:
>
> Ofcom Infrastructure Report 2012 Update
>
> http://stakeholders.ofcom.org.uk/market-data-research/other/telecoms-research/broadband-speeds/infrastructure-report-2012/
>
> http://stakeholders.ofcom.org.uk/binaries/research/telecoms-research/infrastructure-report/Infrastructure-report2012.pdf
> Figure 4 on page 11:
> <mime-attachment.png>
>
> 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.
> (Exercise for the reader - work out how VDSL2 would be any different)
>
>  Also scatter-plots of sync-speed with line-length, as per Figure 8 from
> another UK report:
>
> <mime-attachment.png>
>
> 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.
>
> 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.
> Please contact me off-list - thanks.
>
> Paul.
>
>
>
>
>
>
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>
>
> --
> Guy Ellisguy at traverse.com.auwww.traverse.com.au
> T: +61 3 9386 4435 M: +61 419 398 234
>
>
>
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-- 
Regards,
Peter Adkins
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