[LINK] Re: TV Spectrum for Last Mile

[Richard Chirgwin]

George Bray wrote:
>> So. Does anyone on Link care enough about the broadband-over-TV-channels
>> idea to explain how it stacks up into a business case that genuinely
>> competes with DSL etc?
>>
>> RC
>
> I know we've sparred on this before Richard, but here goes. This isn't
> a business case, just my understanding of the current opportunity to
> use TV spectra for last mile delivery.
>
> 1) The early work on BushLan by ANU said they were achieving
> 100-200kbps. Many years ago now.
>
> <http://wwwrsphysse.anu.edu.au/bushlan/background.html>
No arguments there. But there's a big gap between the BushLAN work and 
the utopian ideal - that's where I get toey!
> 2) When I investigated this issue for the wireless broadband enquiry
> my discussion with management of Broadcast Australia indicated that
> yes, using the VHF band was certainly possible and there existed at
> the time USB modems that worked to 400kbps. That technology might be
> better now too. The upstream link still uses a copper modem line, at
> whatever that will do.
No argument that "the VHF band is possible". Possible does not also 
equate to practical or economical.
>
> 3) We have world's best expertise in RF electronics in the CSIRO, so
> it's plausible that IP over VHF/UHF could be developed further.
> Perhaps specifically to make good use of the national BA network for
> regional users.
>
> Using the TV spectrum for a downlink has been diss'd on this list
> before, based on the experiences of people trying to get DVB-T
> television channels. Certainly, it's not ideal reception everywhere.
> But where it does work, it works well. That digital TV channel you're
> getting is up to 10Mbps coming down that antenna.
>
> At this point in the debate, however, I'd say that IP over VHF/UHF is
> a potential technology for regional networking (100km from town) that
> needs to be considered as a solution for *some* last miles. Combined
> with the nationwide resources of the Broadcast Australia transmission
> network, linked to a national fibre network, using IP on the TV
> spectrum can be a last mile where other technologies don't reach.
Hmm. Broadcast Australia is no longer a public sector organisation; 
those antennaes are privately held, and as has been remarked by regional 
wireless providers, tower space isn't given away for free!

If a user is 100km from town, they could use satellite, which is also 
sub-optimal but workable and available now...
>
> This technology only needs to compete with DSL if the organisation
> funding it is Telstra.  Any other organisation assessing the business
> value (in terms of the establishment cost, and end-user utility) of TV
> spectra would be thinking about the broadband black holes it fills.
>
> I firmly believe that the VHF/UHF network can contribute to more
> diversity in the BB last mile solutions. If the regional copper
> network is not capable of high downstream speeds, why not use existing
> high-bandwidth, wide area RF?
...because a data broadcast is not the same as Internet access. This 
spectrum is good at broadcasts; but less good at one-to-one. Even the 
radios used for one-to-one voice comms in VHF are broadcasting: you see 
the signal whether you're north, south, east or west of the transmitter.

I agree that the regional / remote user should have Internet access at 
the best-possible bandwidth. I also subscribe to the socialist notion 
that it can easily be cross-subsidised from the city. This isn't saying 
'"no bush broadband" - just that I think VHF isn't the solution. However...
>
> I'll try and find Gerard at ANU and see where this scene is at.
Please do! I am interested in the BushLAN work.

RC
>
> George
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