[AusNOG] ADSL2+ line sync data

Fri Sep 13 11:33:54 EST 2013

I think there are to many unknown's to apply much of this type of logic 
to NBN2. The 100M/bit question will be.

Where will they put the "node". The most logical place will be to knock 
over the pillars (big grey knob looking post)  and put the big green 
graffiti target in it's place. The Node will then cover what was 
formally known as the "distribution area" (DA).

  If that's the case the direct main cable usually 300+ pairs direct to 
the exchange will be superseded with the fiber & node. This higher 
density cable is where most of the cross talk is seen usually. It's 
induced in these cables but the root cause  is usually impedance 
mismatch further down the loop. With the higher density cable out of the 
picture I think the cross talk will be decreased overall but the  root 
cause will still be there to cause havoc.

Warning detail ahead !

  Iam assuming BYO CPE and internal customer premisses cable .  So the 
mismatches will still be there even if someone had the foresight to go 
and remove all the bridged tap's in the joining posts and pits. Most of 
these exist in large epoxy filled heads that is basically just  3 pairs 
scotch locked together stuck in what looks like the bottom half of a 2l 
drink bottle and filled with Epoxy.  Some even have passive L/C 
(inductors/coils of wire) components in place that were used to balance 
the loop back toward the now non existing mains cable. Records for this 
stuff is flakey to non-existent. It has to be found. Burred in the 
ground in unknown locations encapsulated in epoxy some in asbestos pits. 
Some of these pits have been covered by earth or concrete years ago.  
There is little financial case to make all this happen. It's man power 
intensive. Time consuming dirty work. It does not fit the Pizza delivery 
business model and wont happen.  You may as well put in fiber at that 
point.

If i was tasked with this brief. That is to get this thing working as 
quickly and cheaply as possible so it can be sold. This is what I would do.

Get a contractor to build a custom node housing. It would be a big box 
that would allow the dslam/vdsl equipment at one end and the other end 
would fit over the existing pillar. Jumpers could then be run from the 
dslam to the pillar  untill all subscribers were off the main's cable.  
The mains cable could then be ripped out by a disposal contractor to 
sell the copper.

Nothing would be done further down the loop. It would work how it works 
now best effort. Customer would go to dick smith and get themselves a 
vdsl modem with POTS/VOIP port and that would be that.  Average speed 
would be <25M/bit with a the lucky few <50M/bit

It would be very quick to finish. Does not touch the ends of the CAN 
where all the problems are and the whole thing could be sold to a sucker 
(aka mum&dad's via share offers and super funds) and we can go through 
this whole thing again in 10 years.

Matt.

On 13/09/13 10:40 AM, Peter Adkins wrote:
> 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 <mailto: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
>     <mailto: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 <http://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 Ellis
>>>     guy at traverse.com.au  <mailto:guy at traverse.com.au>
>>>     www.traverse.com.au  <http://www.traverse.com.au>
>>>     T:+61 3 9386 4435  <tel:%2B61%203%209386%204435>  M:+61 419 398 234  <tel:%2B61%20419%20398%20234>
>>>
>>>
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>>
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>
> -- 
> Regards,
> Peter Adkins
>
>
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