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Australian Researchers Push Near-Broadband IP Over VHF
Curmudgeon Rick writes "A research group at the Australian National University is getting symmetrical 250K bps at 20km, using "empty" 7MHz-wide broadcast TV allocations in the 45MHz band. Story here, project homepage here. Aim is to put some bandwidth out beyond the reach of the wires, where users are few and far between."
Mesh networking would be a better idea than all of this. More bandwidth, more parallelism, less power.
It doesn't sound as if they are really ready to talk about frequency coordination with other users. I hope they don't go about asking for spectrum for anything but experimentation this early in their project.
Bruce
Bruce Perens.
ANU... go to bottom of page
Conquering that 'last mile'
Pioneering work by physicists and engineers at ANU to build a cheap, simple and robust wireless communication system may soon see regional Australia getting a workable connection to the Internet. The system is called BushLAN, and it's all about bridging that 'last mile'.
Regional Australia has never had adequate access to the Internet. It's either not available, too expensive or unreliable. A major part of the problem is the 'last mile' of access. This 'last mile' is the connection between the central communications hub in a local town to individual residences and businesses. Unfortunately, the 'last mile' is usually much more than just a mile. In rural areas such as Cowra, for example, the last mile has been measured to be anywhere from three to 100 kilometres from the town centre. In more isolated areas it can be much greater.
The cost of cabling to only a few customers over these distances is prohibitive and current wireless solutions aren't practical. Satellite connections are expensive and usually require a cable connection for a user to send information out (ie they receive downloads from a satellite but send information out via the telephone). There are ground-based wireless connections commercially available but these operate in microwave frequencies using directional antennas that require a clear line of sight to function. Given Australia's sparse population and frequently hilly terrain this would require a large number of repeater stations.
Dr Gerard Borg is a plasma physicist at the Research School of Physical Sciences and Engineering. His work with radio transmission has convinced him that the last mile could be effectively bridged using the low-VHF radio spectrum. This part of the radio spectrum has much longer wavelengths than the microwave frequencies used by other wireless systems and this allows signals to be transmitted further without the need for expensive repeaters or satellites. What's more, it doesn't depend on line of sight as the signal has the ability to go around mountains and other large obstacles in the landscape. At the moment the low VHF radio spectrum is used to transmit TV signals but with the decommissioning of some analogue TV bands in 2008 (digital TV uses higher frequency radio) there's an opportunity to switch this unused spectrum over to data connections for regional Australia.
BushLAN (Bush - Local Area Network), as the system is called, has the potential to provide remote users in regional Australia with a permanent, high-quality Internet connection (at more than 100 kb/sec) at an affordable price. However, to get BushLAN up and running, many technical and marketing aspects of this multi-faceted system have to be developed first. To achieve his goal, Dr Borg has enlisted the assistance of a wide range of students from the Faculty of Engineering and Information Technology who have taken on the various jobs associated with the system as part of their Honours, Masters or Doctoral projects.
"The practical nature of BushLAN and its relevance to regional Australia really attracts the students," says Dr Borg. "Once they're involved, they become highly motivated about what we're trying to achieve. Quite often they finish the formal part of their work for their thesis, but then they stay on working on the project through the Christmas vacation."
The next step for BushLAN is to set up local trials to test transmissions, and then work with interested Internet service providers to see how BushLAN can be integrated into existing information systems. The hope is that with BushLAN as part of the system, the 'final mile' will no longer be an unbeatable hurdle.
Science Reporter is brought to you by the National Institute of Bioscience, the National Institute of Engineering and Information Sciences, the National Institute for the Environment, the National Institute of Health and Human Sciences and the National Institute of Physical Sciences. Written by David Salt.
For more information on any of the stories presented here please visit http://ni.anu.edu.au/
Quidquid latine dictum sit altum viditur
In Australia the ACCC defines BroadBand as 200kps and over.
er, that would be no.
The channel-width is 7MHz, the frequency is around 45MHz.
Visit CryptoGnome in his home.
Narrowband: less than 2Mbps (POTS, ISDN, etc)
Broadband: greater than or = 2Mbps.
Most DSL lines work at under 1Mbps (home users don't need more and it's damned expensive if telcos offer it at all), but in full flight, it can reach around 8Mbps, so it's technically broadband.
One man's *near* broadband is another man's 2B+D.
As a transmission engineer, you should already know that, in the US, that part of the spectrum (45MHz +/- 3.5MHz) is already allocated and HEAVILY used by all kinds of two-way land mobile radio systems. In fact, the band is sliced up so that even various Federal agencies (including the military) are using it. TV starts at 54MHz, and those frequencies (TV channels 2-59) will be used for HDTV.
Go read 47CFR Part 2...
Yes they do. I am a licensed amateur radio operator (with moorse code, a nifty skill to have, though now kinda useless lol). It is called packet radio. I myself haven't gotten into it, but it is a different protocol which you can tunnel others through (tcp/ip). Some are internet repeaters, basically hooking up their cable modem to their ham radio. Problem is, that only one person can transmit at a time, collisions aren't too common though.
If you are about to mod me down, keep in mind that this post was most likely sarcastic.
This might fly in Australia, but probably not in the US or other large nations. The radio spectrum is a limited resource and as such, a highly competitive one. Amateur radio operators (myself included) are constantly trying to defend our allocated bands here in the US against commercial entities who would like to have it for their own usage. I don't see a system that uses this much bandwidth being practical for US usage.
That's not entirely true.
In the land Down Under, Telstra is the dominant telco, and it's currently 51% government owned. The current Liberal Party (think: nice Republicans)-National Party (think: farmers) coalition government really wants to flog off the rest. The problem is that Telstra provides many services to the underpopulated areas (aka "the Bush", who are generally represented by the National Party half of the Coalition) that really don't make much economic sense but make a lot of political sense. Also, it's sort of halfway decent that the outback farmers get at least a phone service. Anyway, every man and his dog knows that if Telstra gets fully privatised, *bang* there goes any semblance of service to the bush, since it is just not econmical.
To that end, the government has brought in a Service Guarantee (including Universal Service Obligations) that says (amongst other things) Telstra must provide certain minimum standards to all subscribers, and if they don't they get smacked. The government hopes that after a few years we'll all see what a good corporate citizen Telstra is and give the Libs the OK to flog off the other 51% of Telstra.
Now, one big complaint from the bush is that they get bugger all access to broadband. Even getting net access at all can be tricky for them. Satellite (if available) is very expensive. This would almost certainly not improve under a toally privatised Telstra. However, if Telstra could provide near-broadband to the bush without having to string up hundreds of miles of cable, things would again be looking promising for the privatisation thing to be on the agenda again.
Speaking from a purely Australian voter/taxpayer POV, the keyphrase is the National Party might be the junior member of the coalition but they can wield a fair amount of power over the Libs when they want to.
.When they came for the communists, I said "He's next door. Take him away. Goddam commies."
Analogue television channels in Australia are 7MHz wide. The channels of interest are between 45 and 75MHz. BushLAN is not necessarily tied to using a particular block of spectrum, or an entire television channel. BushLAN subdivides available spectrum into 300kHz channels. As always, there is a tradeoff between transmitter power, communications range, and the data rate.
Using two 300kHz channels [for a symmetric full-duplex connection] low power, relatively short range links with a raw data rate of 115.2kbps have already been created.
As to propagation. VHF achieves beyond line of sight range whereas microwave links are limited to LOS. Long distance propagation is largely due to diffraction over hill tops. Atmospheric attenuation is much smaller at VHF (wavelength is roughly 6 metres) than it is at microwave frequencies (wavelength: ~10cm). This allows greater reliability during adverse weather conditions.