Follow Slashdot blog updates by subscribing to our blog RSS feed

 


Forgot your password?
Close
typodupeerror
×
Wireless Networking The Internet Hardware Technology

Australian Researchers Push Near-Broadband IP Over VHF 211

Posted by timothy from the verified-horse-feathers dept.
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."
This discussion has been archived. No new comments can be posted.

Australian Researchers Push Near-Broadband IP Over VHF More

Australian Researchers Push Near-Broadband IP Over VHF

Comments Filter:

  • wow! (Score:2, Funny)

    by Anonymous Coward
    So now even my TV can get b roadband!

  • Cool and all (Score:5, Funny)

    by mphase ( 644838 ) on Monday December 08, 2003 @10:34PM (#7665535) Homepage
    ...but doesn't this just mean one lucky bastard in the boonies will be getting good speeds or 50 unlucky bastards getting crap speed?

    • Re:Cool and all (Score:5, Funny)

      by tonyr60 ( 32153 ) * on Monday December 08, 2003 @10:46PM (#7665602)
      Building on our great pool of expertise developed from 802.11, I suspect that one bastard gets to communicate and 50 lucky bastards get to listen (or watch) in...

      • Re:Cool and all (Score:2, Informative)

        by tiger99 ( 725715 )
        I would expect that it would ultimately take on a cellular architecture, with maybe only 5 to 10 prospective users within range of the base station. The population density is very low in the outback, but this technology would be much cheaper than cabling 10 well spread-out properties (say 200 miles of cable for a star topology!).

        It would be better to use satellite, cable or microwave to feed all but the smallest towns.

        I wonder what the ultimate limit on baud rate would be, for example an analogue telephone

    • Re:Cool and all (Score:5, Funny)

      by principio ( 558251 ) on Monday December 08, 2003 @10:51PM (#7665643) Journal
      and we may be looking at the birth of the largest collision domain in the known universe

  • New slogan? (Score:5, Funny)

    by Silent Bob On Couch ( 669565 ) on Monday December 08, 2003 @10:34PM (#7665538) Homepage
    I wonder if this will be marketed in the US for rural areas. I can hear the slogan now...

    "VHF... Australian for Broadband."

  • broadband ? (Score:3, Interesting)

    by Anonymous Coward on Monday December 08, 2003 @10:36PM (#7665546)
    i allways thought broadband was at least 10mbit, this is 'only' as fast as 4 isdn lines, sure better than dialup but nowhere near broadband..

    • Re:broadband ? (Score:4, Informative)

      by motivator_bob ( 322365 ) on Monday December 08, 2003 @11:00PM (#7665690)
      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.

      • Re:broadband ? (Score:5, Interesting)

        by Crypto Gnome ( 651401 ) on Monday December 08, 2003 @11:35PM (#7665873) Homepage Journal
        I believe than in Australia Telstra urged the government to defind broadband as "128Kbps and up" so that they (Telstra) could then claim that (whatever the exact statistic is) the vast majority of Australians have access to internet at broadband speeds.

        Something to do with Telstra being legally required to provide said "broadband" coverage, by a certain date, or be subject to fines/limitations on expansion into other markets/or something.

        No surprises here, just Yet Another Big Business redefining reality so that they can wipe their hands of their legally bound responsibilities and rape their customers for further profits.

        • Re:broadband ? (Score:2, Informative)

          by mvpll ( 542255 )
          Close. it is actually the government doing the dodging. Telstra is currently partially owned by said government (they have already managed to sell half of it) and various political machinations are involved in selling the other half.

          Many people outside of the major population centres are concerned that a fully private company would have little interest in supplying them services. Said company would get much greater return on their investment by solely targeting capital spenditure in the few major cities.

          T

    • FAQ (Score:2, Informative)

      by foobsr ( 693224 )
      FAQ [dslreports.com]...etc.

      CC.

  • Be nice (Score:4, Funny)

    by roninmagus ( 721889 ) on Monday December 08, 2003 @10:39PM (#7665563)
    It'd be nice, but unfortunately my VCR does not support the Australian internet.

    ;-)

    That's coming from an ebayer embittered by NTSC purchases :)

  • near-broadband? (Score:5, Interesting)

    by slavitos ( 666569 ) on Monday December 08, 2003 @10:40PM (#7665567) Homepage
    Interesting term, "near-broadband".... If I am not mistaken, broadband is defined as a communications medium that can be divided into multiple segments that can be used for different purposes (e.g. voice, data, video, etc).

    Isn't "nearbroadband" almost the same concept as being "almost pregnant"?

    • Yeah... (Score:5, Interesting)

      by mindstrm ( 20013 ) on Monday December 08, 2003 @10:48PM (#7665617)
      But the term "broadband" has come to mean "fast" in the common language. Thank the media for that.

      In the olden days, the highest speed things tended to be broadband, so the meaning just got twisted.

      I'd say, considering speeds and waht is noramlly known as broadband in the US... 250kbps qualifies as "near broadband"... people usually think 1mbps is broadband.

      • Actually the highest speed things are baseband. Mainly because you don't have to waste bandwidth sharing it between different transmission methods.
      • The US government defines broadband as 200kbps.

        http://www.usda.gov/rus/telecom/broadband.htm#in fo
    • Isn't "nearbroadband" almost the same concept as being "almost pregnant"?

      see below...

      But the term "broadband" has come to mean "fast" in the common language. Thank the media for that.

      well if yer that fast...you are far more likely to be pregnant, than not, no?
    • No, closer to being "slightly fatally injured."

  • Could be a nice alternative.. (Score:5, Interesting)

    by iantri ( 687643 ) <.iantri. .at. .gmx.net.> on Monday December 08, 2003 @10:40PM (#7665571) Homepage
    This could be a nice alternative for those of us who still aren't able to get broadband (No DSL where I am and Rogers Cable never bothered to run cable to the last three houses. Guess where I am! GRR), without all the potential problems with broadband over power lines (signal leakage, interfering with ham radio).

    • Re:Could be a nice alternative.. (Score:5, Interesting)

      by zerocool^ ( 112121 ) on Monday December 08, 2003 @10:50PM (#7665639) Homepage Journal
      This is my *one and only* problem with moving out into the country. My fiancee and I are casually looking at houses, expecting to possibly be buying next spring (house buying season). With interest rates what they are, and property values going up quickly where I live (my parents bought their house 1995 for $154k, now worth >$300k), we'd like to get a house of our own, but not on a zero-lot-line, no privacy, near all the people kind of land.

      The only problem is: Move into the sticks, no always on internet. This would be a godsend for me - I don't want high speeds, I don't do online gaming, and I don't download a bunch of stuff, but I do want it to be on *all* the time. I want to be able to sit at my desk and see who's online on IM, and to check my mail or look at the news.

      This would be *perfect*. Hope they can figure out the details in the next few years. In the mean time, I may be investigating satelite internet.

      ~Will

      • Re:Could be a nice alternative.. (Score:5, Interesting)

        by anethema ( 99553 ) on Monday December 08, 2003 @11:16PM (#7665770) Homepage
        If you have a some high land nearby...or a small tower, you could set something up with a friend to use some of his/her bandwidth via a laser or WiFi connection. I'm setting up a 2 person laser lan with a friend of mine, and hes 20 km away. I've got to bounce it back across one hill because i dont have line of sight. 10mbps. It's doable.

        You also dont usually have to be too far from town to get a nice country home. I rent a place on 2 acres of green grassy land, 3 gardens, etc, for 950 a month. Of course I'm in canada, and there is probly a lot more nice available real-estate up here, but still, I live like 30 seconds drive from town, and 10 minutes from down-town kelowna.
        • I'm setting up a 2 person laser lan with a friend of mine, and hes 20 km away. I've got to bounce it back across one hill because i dont have line of sight. 10mbps. It's doable.

          You mean 10kbps, right? That's doable at 20km without selling a kidney each. Otherwise...
        • If you don't have line of sight, I wouldn't hold your breath at 2.4 gigs. I wouldn't bother wasting time trying with laser.

          Both technologies are inherently line of sight, 2.4 gz will suffer severe attenuation by anything in its path. It is possible to cause signals at vhf/uhf to bend over hill brows, but the signal will be attenuated severely due to scattering.

          20 Km distance at 2.4 gig is going to need some fairly high gain antenna at both ends, even with line of sight, the figures for free space attenuat
      • >In the mean time, I may be investigating satelite internet.

        What about ISDN? Pricing may not be bad in your area. 128kbps switched is pretty fast.

        Or a router with two plain-jane 56k modems in it. If your ISP supports modem multi-plexing (or whatever its called) you can plug right into the ethernet interface, use DHCP, set-up a firewall, set it to always call back if the ISP hangs you up, etc. That's a 100k connection right there.

        3COM has a router like this and it was a lifesaver when our Northpoint
      • Easy pick up a second line broadband is 50 a month get a couple modems and run multilink over them keep the dedicated line up all the time for your constant on and bring up the econd line one demand and via avalibility with v92 you should be able to still get calls on it or just drop the line if you need to make one. ISDN is also a nice choice if your fee's are reasnable.

        Realy though as somebody thats currently looking for land in the country DSL is out there same for cable modems and if all else fails sa

  • Wait a Minute (Score:5, Insightful)

    by Anonymous Coward on Monday December 08, 2003 @10:42PM (#7665578)
    Does Telestra know this? Surely they'll want to put a stop to any competitors of theirs.

  • There's a problem (Score:5, Interesting)

    by carambola5 ( 456983 ) on Monday December 08, 2003 @10:45PM (#7665600) Homepage
    where users are few and far between

    Sorry, but speaking from purely a capitalist's point of view, the keyword here is few. As cool as the technology is, it'll never take off.

    • Re:There's a problem (Score:5, Informative)

      by martinX ( 672498 ) on Tuesday December 09, 2003 @12:00AM (#7665978)

      That's not entirely true.

      In the land Down Under, Telstra [telstra.com.au] is the dominant telco, and it's currently 51% government owned. The current Liberal Party [liberal.org.au] (think: nice Republicans)-National Party [nationals.org.au] (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 [dcita.gov.au]) 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.

      .
      • Now, one big complaint from the bush is that they get bugger all access to broadband.

        Hell, my brother lives 20km from the Brisbane CBD and he can't get broadband.
        • Hell, my brother lives 20km from the Brisbane CBD and he can't get broadband.M/i>

          Hey! My brother resembles that remark! You don't have to be very far at all from a major population centre before Hell$tra won't sell you 'broadband', in any flavour. They're a LONG way from actually real-world achieving the "% of population has access" that they claim.

  • This story is wrong. (Score:5, Informative)

    by Bruce Perens ( 3872 ) * <bruce@perens.com> on Monday December 08, 2003 @10:46PM (#7665605) Homepage Journal
    The stuff about VHF following the curve of the atmosphere and bouncing off of the ionosphere isn't quite right. That's HF. The frequency in use for this experiment, 45 MHz, would bounce during sunspot maxima but you can't build a communications system with it if you need it to bounce. Also, the choice of frequency is strange - 45 MHz rather than microwave, where there would be much less of a problem. Do they mean to run a star topology rather than point-to-point? 7 MHz for 250 Kbps is not so great. You should get 28 250Kbps channels in there. Multipath would be the main problem.

    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

    • I hope they don't go about asking for spectrum for anything but experimentation this early in their project.

      If it does prove successful in either mesh or single-path topology, you can bet the local telcos and broadcasters will kick up a stink. I can hear the regulators shuffling their paper already...

    • Re:This story is wrong. (Score:3, Informative)

      by t0qer ( 230538 )
      250bps mesh isn't all that great bruce, having worked at ricochet tech support and having sat right underneath the main los gatos WAP and being able to see at least 6 other WAPs from that spot I can tell you the performance was crud.

      Even at double the bps, it still would be crud performance...

      The only place mesh seems to work well is over high speed, low latency copper wire or fiber, since the number of transmission retries are zero to nil.

      I'm not trying to troll, i'm just trying to point out an inherant
      • I still have a couple of the original Ricochet radios. They're pretty useless now.

        It sounds as if Ricochet had the hidden transmitter problem. It sounds likely if you could see 7 of them. Did they use any sort of channel reservation protocol?

        Bruce

        • There were a bunch of people at Stanford who built interesting network things with Ricochet - I think the project was called "Mosquito Net". You could either do point-to-point connections between pairs of them, or do "star mode" by feeding them the magic commands, but I never worked on them myself. They did have longer range than 802.11, so it's sometimes more useful, but of course they're not blazingly fast.
    • >7 MHz for 250 Kbps is not so great. You should get 28 250Kbps channels in there

      The article is distinctly light on technical details. It might be full duplex, ie 250Kbps in both directions at the same time, even that is a poor data rate to bandwith ratio.

      The quote from Dr Borg says they are not channelising though that dosn't rule out the 250Kbps figure being a timeslice allocated to a paticular station.

      I'd like to know what modulation scheme they are using for this. I suspect they are compensating

    • Bruce, you got this sorta right - you are going to see ionospheric bending at the height of the sunspot cycle, but you'll also see tropo-ducting, E layer skip, and meteor-bounce to name the modes I can think of off the top of my head.

      In my mind this is absolutely the wrong kind of characteristics you want for this kind of application. You're going to get regional interference all the time from all these different types of propagation.

      I do agree with you that microwaves, or at least high VHF/low UHF would
    • They want low frequency VHF as opposed to Microwaves to cover long distances (think 50-100km). One reason they can't get full speed from the 7MHz is the time it takes a signal to travel that distance, over 30km or so the round trip times start to get significant.

      As for mesh networking, yes it would be a better solution however there may be nothing (no towns/houses just rocks and dust) inbetween one end of the link and the other to create that mesh, so its not really a useable solution. Having repeater s

      • over 30km or so the round trip times start to get significant

        $ units
        2084 units, 71 prefixes, 32 nonlinear units

        You have: 30 kilometers
        You want: light seconds
        * 0.00010006923
        / 9993.0819

        0.1ms is a heck of a lot better than the average T1.

    • True - a nice real time map of ionosphere reflection characteristics can be found here [ips.gov.au] . The researchers themselves don't ever mention ionospheric bouncing.

      On an unrelated not, the university I work at runs their own ionosonde. They used to have trouble with the station being vandalised until they put up a sign "Warning: this facility frequently bathed in high frequency electromagnetic radiation". The HF radiation in question was sunlight, but there hasn't been any problems since.

      They seems very serious a
    • Low band vhf can sometimes act like HF - look up sporadic e propagation. The current distance record last I heard was a contact between someone in Washington and an operator in South Africa on 6 meters (that starts at 50 MHz).

      I'll fully admit its not a sustainable propagation mode anyone would want to rely on to any degree, but it happens often enough there are people out there who try to predict and operate sporadic e as its highly efficent.
    • Mesh networking would be a better idea than all of this. More bandwidth, more parallelism, less power.

      Ok, so where are the HiperLAN 1/2 products? Where's 802.16a? Why haven't we seen new code from LocustWorld in an entire year? Even MIT's roofnet is a hacked-together mess of non-routable IP addresses. (Ever read the "Click Router" documentation?)

      Mesh Networks = Flying Cars

      Show me a working 10mbps wireless mesh of over 10 nodes and I'll withdraw my statement.
    • Bruce, for the parts of Australia where this technology is going to be used, spectrum is the least of their worries. A maximum range of 20 kilometres (if that is indeed the maximum) is a *much* bigger problem than spectrum. Where this thing is likely to be used, there isn't any terrestrial television broadcasts to interfere with anyway. Oh, and there aren't too many hills to cause multipath distortion either.

      Assumptions about communication technology that apply in the rest of the developed world often s

    • If you search the university website for Bushlan, you find no reference to 45MHz anywhere. The project has been done at 7 MHz RADIO spectrum for doing the research. 7 MHz is near the 40 meter amateur band and indeed is good for long distance communication most of the time. When the TV bands become available in a few years, they will have to adjust frequency, but even 45 MHz which is just under the 6 meter amateur band, and enjoys fairly good communication reliability. You might also consider that in the

  • Actual Link to Story at ANU (Score:3, Informative)

    by LuxuryYacht ( 229372 ) on Monday December 08, 2003 @10:47PM (#7665612) Homepage
    ANU... go to bottom of page [anu.edu.au]

    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/

  • BB Speeds (Score:5, Informative)

    by Dylancable ( 718004 ) on Monday December 08, 2003 @10:48PM (#7665616)
    In Australia the ACCC defines BroadBand as 200kps and over.

  • Downtown areas. (Score:5, Interesting)

    by jfisherwa ( 323744 ) <jason.fisher@[ ]il.com ['gma' in gap]> on Monday December 08, 2003 @10:52PM (#7665644) Homepage
    As a frequency this low will generally pass through buildings and obstructions much more effectively, it's probably a more likely candidate for inner-city wireless broadband than 802.11 -- on a commercial level.

    If some ISP can obtain the correct licenses and find an existing 802.11 chipset with firmware-programmable frequency, they'd be the winners of all time.
    • A chipset can't just be "flashed" to a different frequency. RF transmission is tricky and different frequencies require different designs. The RC characteristics of the circuits have to be carefully designed to match the frequency they will be providing and the antennas and carriers should be tuned and impedance-matched for optimum performance.

      Changing from channel 1 to Channel 13 can be done in software because it's a matter of 5% difference in frequency, but the 2.4GHz frequency spectrum is 5100% highe

  • There is a market (Score:5, Insightful)

    by F'Nok ( 226987 ) on Monday December 08, 2003 @10:57PM (#7665681)
    I think that the market is UNDER estimated for this than anything. with 20-40k coverage, it is fantastic for rural coverage. And for a country where the majority of the population are active online, this means for rural areas that are spread out over large areas, it is feasible. The expense to cable an area with 10,000 people over a 20km radius is very prohibitive. However, the market for internet of 10,000 people, where network expansion means grabbing a bit more spectrum and setting up another station, is relatively small. I think this is fantastic for our rural areas here in Australia, because FAR too many cannot even support decent dialup. Who makes long distance calls for a 56k connection? Or worse, an unstable one?

  • Yes!!1 (Score:3, Funny)

    by riotstarter ( 650328 ) on Monday December 08, 2003 @11:00PM (#7665689)
    Finally, Pr0n on the TV...oh wait...

  • The Problem with VHF (Score:2, Informative)

    by Cpl Laque ( 512294 )
    Generally the problem using VHF is that its pretty limited to a few miles unless you are pumping some serious Watts with a gigantic antenna. Also I am pretty sure 45MHz is used for Military VHF communications(I believe the band to 30MHz to 87.975 or some such) but I am not sure about Australia and its Military freqs. I seem to remmember we could send "data" over VHF when I was in but it was hardly used(I just don't think anybody knew how) We did a bunch of teletype stuff that was pretty annoying.

    Back to th
    • In the US, there are VHF television bands from 54 to 72 (channels 2,3,4), 76 to 88 (channels 5 and 6) and 174 to 216 MHz (channels 7 through 13). UHF is an enormous wasteland of spectrum from 470MHz to 806 MHz. I am guessing from the context that Australia has similar allocations.

      Penetration (of structures) is relatively good at low VHF frequencies, even at relatively low power levels, and LOS can be improved with the simple addition of artificial height (tower). Also, at the frequencies they are using

      • Besides the huge latency and extortionate price (mentioned in my other post to this thread) there is also that nice weather blackout behavior.

        I always know when a nice storm is about to hit my immediate area when I'm watching directtv. The screen starts pixellizing and gapping. Then there is the blanking of the screen and the message "searching for signal". Then the rain or snow starts pelting the house. It gives me about a 10 minute warning EVERY time. Real handy, except for television and/or intern

    • Hah! Satellite. Yeah, right, satellite. HUGE latencies, high price. I'd rather stick with 56k modem than pay $70+/per month just for the internet connection via satellite.


      If they charged ~$20-30/month and I didn't want to be able to play networked games, then satellite would be fine. If you have more money than sense and don't do anything but browse and email then satellite is fine.

  • Just imagine how far you could transmit during E layer band openings. Hehehehe

  • Let's see Dr. Borg push this over 7Mhz VHF! (Score:3, Funny)

    by Proudrooster ( 580120 ) on Monday December 08, 2003 @11:17PM (#7665774) Homepage
    Let's see them push this streaming chrismas carol [pquinn.com] over their VHF connection :)

    Also, the article had this quote which I found interesting: Dr Borg said, any possible license conflicts - with digital radio advocates, and with the remaining users of the appropriate spectrum - would have to be resolved..

    I wonder if the resolution will sound like this? All your VHF Bandwidth are belong to US! Resistance is futile. We will use your bandwith for irrelevant Christmas Music Remixes [pquinn.com].

    Ding Fries are Done! Merry Christmas!

  • only 250kbps! (Score:3, Insightful)

    by Bruha ( 412869 ) on Monday December 08, 2003 @11:19PM (#7665798) Homepage Journal
    Look in 1xRTT ie the current 3g offerings by Verizon Wireless and Sprint we use 1.25Mhz of bandwidth and we can push 155kbps.. I even think our EVDO pushes that envelope further.. so I'd think you could do more on 7Mhz of frequency

  • Maybe Austrailia, but not here... (Score:4, Informative)

    by turtlexit ( 720052 ) on Monday December 08, 2003 @11:47PM (#7665922)
    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.
    • What is a large nation?
      Australia: 8 112 000 sq km
      USA: 9 363 123 sq km
      and most of the difference is Alaska:
      1 518 800 sq km.

      Also, look up your dictionary:
      x1000 is "k", eg km, kg, kW and kbps. K is some adhoc prefix thought up by geeks. Careful scientists and engineers use "k".
      http://physics.nist.gov/cuu/Units/prefixes.h tml

      • Australia is large, geographically, but they are in no way large demographically. Australia doesn't have the population numbers, nor the broad population density, of the USA. Thus, while Australia can perhaps easily dish out freqs to ISPs and whatnot, that is not the case in the USA where anywhere you go there are people and the frequencies are pretty much used up no matter where you go.

  • 17W of power to get 40km?

    I use/test/setup equipment that goes 50km at 0.5W of power. OK, they're using a non-optimal antenna, but the antennas really aren't that expensive. 17W would kill a bettery quick. No surfing for pron at night anymore.

    200kbps is interesting, and as Bruce Perens mentions, they should have been able to get a lot more bandwidth out of the spectrum they are using. None-the-less, they could be making a robustness/raw data rate tradeoff in the modulation scheme. I am probably just blind
    • >I use/test/setup equipment that goes 50km at 0.5W of power.
      That means nothing unless you specify the frequency and mode of transmission. A half watt morse code transmitter on HF will go much further than that. A half watt walkie talkie on VHF won't go very far if you are at the bottom of a valley.
  • but I thought VHF was already capable of broadcasting and recieving high speed data. Isn't HDTV in the high MB/s data rate? And they broadcast HDTV over regular OTA. Now I know that HDTV is asymmetrical but I remember back in the day there were people broadcasting data back and forth using small transmitters and regular UHF/VHF antennas. They were mainly used for weather data and such but I remember they were capable of massive speeds. It seems to me the structure for such a system has been up for a while,
    • In the US (ATSC standard), digital television is 8VSB modulation plus FEC to achieve 19.39 Mbps MPEG-2 transport stream.

      There have been several trials to encapsulate IP in MPEG-2 packets, and multiplex the IP stream into the DTV video stream on a different PID. For instance, a few Mbps of multicast Windows Media video has been shown at NAB.

  • Channels 0 and 1? (Score:2, Interesting)

    by craXORjack ( 726120 )
    surprisingly, some remaining users of the Channel 0 and Channel 1 TV allocations.

    Any aussies here know what would be using channels 0 and 1? Did Australia follow the US when it reallocated the frequencies back in the sixties? I can't even remember what channel 1 got reused for here in the states. I think it was business band radio like for taxicabs and such.

  • Low Band VHF (Score:2, Interesting)

    by Simple-Simmian ( 710342 )
    I think they could do better than use low band VHF for this.
    You would get more bandwidth as well.
    AU has few people so they have more unused spectrum to play with.
    I would think a higher frequency and better enginering would yield better results.
    At around 45 Mhz the antennas are still quite large though the signal does tend to travel well over hilly terain in this frequency range and it can propigate via the E layer at the right time of year as well.
    Well at least it's not in the middle of the Ham bands for on

  • Spectrum, data rates, propagation (Score:5, Informative)

    by dogsend ( 568967 ) on Tuesday December 09, 2003 @01:00AM (#7666209)
    Just to clarify some of the issues raised already...

    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.

  • Don't know the situation in Australia WRT satellite services (number of slots, existing birds, total market size, etc) so this may or may not be relevant. The data capabilities that can be provided by the new Ka-band satellites sounds like an excellent match to this situation. The climate and geography seem ideal -- dry and mostly flat. Of course, the technology is expensive in initial investment, but then it's easy to add individual users. I'm used to thinking in terms of service for the US and/or Europe,

Slashdot Top Deals

If you aren't rich you should always look useful. -- Louis-Ferdinand Celine

Close