[AusNOG] 700Mbps over copper pair...over 400 metres

[Paul Brooks]

On 23/09/2010 3:42 PM, Matthew Moyle-Croft wrote:
>
>
> As an exchange based technology it's not terribly interesting except 
> for CBD exchanges and quite short loops.   VDSL2 uses about 6x as much 
> power per port, especially if you want the higher speeds, so, given 
> the limitations on heat/power in TEBA, you can get a lot less ports 
> per rack.    But, for CBD exchanges with short loops, it would have 
> been pretty good.
>
> I'd have been happy if it was deployable, then at least we'd have a 
> choice where it made sense - certainly the bonding technologies which 
> can deal with cross talk are quite interesting to deliver good speed, 
> but, I suspect it'd be mainly for inbuilding or short loops to 
> business rather than residential unless we went for a cabinetised or 
> subloop unbundling model.

The bonding techniques - or at least the Dynamic Spectrum Management 
techniques and 'phantom circuit' methods that Alcatel-Lucent and this 
latest Huawei release is all about - require all copper lines in the 
bundle to be driven from ports on the same DSLAM, and currently on the 
same linecard  of the same DSLAM. In a ULLS world where each pair can be 
driven by a different DSLAM and is unsynchronised with the others, DSM 
falls down - so do you want an exchange MDF to be monopolised by a 
single DSLAM operator to enable that provider (only) to provide 
DSM-bonded VDSL2 in the area?

Also in the context of an exchnage - the 400 metres starts at the VDSL 
DSLAM port. By the time the signal has travelled from the DSLAM linecard 
through the cross-connect cable to the MDF, down the MDF to the 
line-side, and then to the outside wall of the exchange, you could 
easily lose 150m of that distance just inside the exchange building. In 
a CBD exchange, with TEBA space on multiple floors, the distance lost 
inside the building is probably the worst case of all - sooo - is there 
a sufficient number of potential customer buildings within ~200 metres 
of the exchange outside wall (allowing a few tens of metres inside the 
customer building for risers etc)??

VDSL2 is a great technology for FTTBasement then 
inbuilding-copper-up-the-riser deployments - not so much from exchanges, 
even CBD ones, I think.

Paul.
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