[LINK] BPL
Paul Brooks
pbrooks-link at layer10.com.au
Mon Mar 16 13:24:42 AEDT 2009
stephen at melbpc.org.au wrote:
>
>
> I'm not being a smart arse .. i just want to know why a lot of Australia
> has NOT got BB nor probably anytime soon, when it seems that this system
> apparently works quite well. Is it really only a matter of an incentive?
>
Many of the BPL trials never progressed because it couldn't be made
cheap enough to compete with the price of ULLS/LSS on a per-user basis -
the technology worked, but was too expensive to compete with DSL.
From memory, BPL systems suffer from fairly short range (at least the
implementations I looked at several years ago), as the power conductors
aren't optimised for comms, so the signal level dies off within hundreds
of metres - maybe a kilometre or two - unless you install
boosters/amplifiers.
You also need to run the 'head-end' signal all the way out to the last
transformer, and inject the aggregate head-end signal onto the wires
after the last distribution transformer - and in Australia there are
usually a few hundred houses downstream of a distribution transformer,
That makes BPL look a bit like FTTN (fibre-to-the-transformer), with the
last-km infrastructure having shorter range than ADSL, and possessing
the shared/contended characteristics of HFC.
So yes, BPL can work - but it effectively combines the worst
characteristics in terms of cost, complexity and performance of most of
the alternative platforms, so isn't viable when the alternative
platforms are already in place.
About the only benefit BPL has is that it avoids the capital cost to
install a new last-km telecoms-transfer-conduit into each home, which is
great if there are no other existing telecoms-transfer-conduits
available to you, or a competitor for your intended service - such as a
telephone twisted-pair.
>
> If so, and word gets around, maybe country folk should be majorly pissed!
>
The main problem for country folks is distance, including the lengths of
their driveways (and sweaping generalisations). Broadband signals
attenuate, whether on metal wires, glass wires or radio waves - and the
higher the frequency, the shorter the range. BPL has no solution to fix
this.
(I guess you could QAM-modulate the 50Hz mains frequency to distribute a
data signal to a long range, but I doubt country folks would appreciate
the performance, or what this would do to the appliances that rely on a
clean sinusoidal feed).
Paul.
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