Frank O'Connor foconnor at ozemail.com.au
Tue Apr 7 23:12:36 AEST 2009

At 9:04 PM +1000 on 7/4/09 you wrote:
>On Tue, 7 Apr 2009 at 17:43:07 +1000 Frank O'Connor wrote:
>>Any way you look at it, ADSL over copper has serious distance from 
>>exchange issues.
>In the NBN environment, wouldn't that be distance from the nearest fibre?

More like distance from the nearest DSLAM ... which for all intents 
and purposes is the exchange where the DSLAM is installed.

Problem is that the signals attenuate cover distance (especially in 
copper), the DSLAM monitors the lines and channels, does the quality 
control thing and boosts the signal accordingly. With copper, DSL 
connections start to deteriorate ... attenuate ... after about 1.5km. 
With fibre that distance is way increased ... because attenuation 
(and interference) is much less over fibre.

That said, there's really no reason to use DSL protocols over fibre 
... even with the algorithms developed by that Greek-Australian 
academic in Melbourne you'd max out at 250Mbs. You could use any 
number of alternatives (Ethernet, ATM, or to a local 802.16 network 
station/router etc) at the network layer and plug IP protocols in 
over the top for a much better yield 'out of the box' as they say.

>>  ... FTTH looks like your best option, and with the new NBN that 
>>looks like happening.
>According to one linesman I spoke to, Telstra made a habit of laying 
>fibre whenever they needed to replace or install copper. In 2003, 
>they apparently lay fibre to within 200 metres of my door. It's 
>still dark. I wonder how much of Australia is in a similar position. 
>Only Telstra would know the extent of that dark network.

Mmmm ... but despite that they wanted to provide us with an FTTN solution.

There's problems 'splitting' fibre to different connections, but you 
can run an number of channels over the same fibre (I don't know how 
good the signal discrimination currently is .... but I'll bet it's 
improved since the mid 80's when they were postulating about 50 
channels for 1 Gbs over a single fibre) and have seen figures of 
about 20 times that mentioned in the literature.

>>The other alternative would be satellite, but that currently peaks 
>>at about 400 KBs from memory ...
>2 Mb/s: <http://www.bluemaxx.com.au/satellite/commercial.html>

So, about half of what I stated.             :)

I was pretty sure that Telstra offered 400 KB satellite in the bush 
... but if you say it's half that I'll agree with you.


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