[LINK] Look, up in the sky! [Was: Lag will set our broadband back: expert]

Paul Brooks pbrooks-link at layer10.com.au
Wed Jul 29 12:49:16 AEST 2009

David Boxall wrote:
> It looks like Minchin was right: 
> <http://www.abc.net.au/reslib/200907/r407663_1922763.asx>.
> One reason given for the delay in the NBN build in Tasmania is lengthy 
> negotiations with the state-owned electricity supplier for access to 
> poles, from which to string fibre.
> So what are the potential impacts on reliability, durability, 
> maintenance costs and value of the network, given that it seems much - 
> if not most - of it will be overhead?
It depends very much on geography, and what you already have at hand.

 From my TransACT days - most of the fibre/copper cables there are also 
overhead, which is much cheaper and faster to deploy, so the impact 
there is a lower cost network with services available in a shorter 
timeframe.  However to the question of reliability - the Canberra poles 
are generally in back yards and reserve corridors, not so much along 
busy suburban roads, so vehicle impact isn't as big an issue as it is 

Maintenance costs aren't much different - lift a manhole/small 
trench-digger  vs climb a ladder/cherry-picker.
Durability - underground cable is vulnerable to backhoes, and eaten by 
rats/ants, overhead is vulnerable to truck impact, and eaten by 
cockatoos, but redundant loops and correct cable coatings generally 
reduce the impact of this either way.

There are many good reasons to deploy overhead, as there are to deploy 
underground, and it is never a case of exclusively one or the other - 
some will be underground where it makes sense, some will be overhead, 
the only question is the relative proportion - as always, it comes down 
to 'good, fast, cheap - pick two only to optimise'.

The main arguments against aerial cable are not 
reliabilty/durability/maintenance at all, but cost vs visual aesthetics.

> On Mon, 06 Jul 2009 at 18:14:52 +1000 Richard Chirgwin wrote:
>> I *suspect*, entirely without supporting evidence, that the overhead 
>> cable issue exists at least partly because there's overhead fibre 
>> already there. It's quite feasible that Telstra and Optus would both be 
>> thinking about what's called "vending in" - that is, "here's some 
>> network infrastructure, we want X shares in NBNco in exchange".
Its not so much that overhead fibre is already there, but that 
rights-of-way are already there - Telstra already has access to 
underground ducts, pits and pipes - so their lowest-cost option is to  
lay new cable underground. Electricity utilities like Aurora and 
TransACT/ACTEW have access to existing poles, so their lowest-cost 
option is on the poles.
Outside Tasmania, the NBNCo builder may not be an existing electricity 
network like Aurora, and also may not have ready access to existing 
ducts - so its not worth extrapolating the Tasmanian situation to the 
mainland, but the prior experience with Optus HFC would suggest the 
lowest cost option is to rent access to the poles.

If Telstra would vend-in its duct network, the story may change.


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