UK regulator Ofcom has announced it will make 6.8GHz of spectrum - from 57GHz up - licence exempt for fixed-wireless links, unless you're too near the MoD. The statement (pdf) follows a consultation on the subject which ran up until September, and generated a few responses that Ofcom has considered, and rejected. Anyone will be …
So what's the bandwidth?
somebody with the requisite knowledge tell us what the maximum reasonable bandwidth you'll be able to get over 1KM with this is??
I calculate it to be
one point twenty-one jiggawatts
Strewth, any fule know the units of bandwidth are jiggawatt.meters, or it wouldn't be a width, innit?
Bandwidth will be....
6.8GHz, as stated in the article.
Or are you asking about data transfer rate - a different beast entirely ;)
For that you need to check modulation etc, but it should be pretty high, even if you assume you can only use one frequency, and can cram no more than one bit per cycle into the data stream then 60Gbps.
Of course you actually have 6.8GHz to play with, if you can use 1000 different wavelengths without interference then 60Tbps is the basic assumption.
Minor nitpick (the best type!)
It's more likely that the oxygen rich atmosphere would absorb the signal than adsorb it, electromagnetic waves don't stick to the surface of oxygen atoms too well ;-)
Beer: Because I Owe everyone a beer now, and it's that season again
Now that you mention it,
I was about to comment on that myself.
It says 6.8GHz.
So if you are using below the noise signalling you could get maybe a raw 1Gbps before FEC at about -3dB SNR
If you have +22dB SNR, you might get 36Gbps.
Depends on if there is an upper limit to dish size. 30dbi is a very small dish at 60GHz. (about 45cm @ 11GHz). I think 45cm dish might be 45dB gain @ 60Ghz with approx 60% efficiency. Path loss is very high... My software runs out of numbers at 30GHz.
If you used the full 6.8GHz and only a 1Mbps data rate then Shannon tells us you can operate well below the noise maybe nearly -30dB SNR
Teeny 'Tennas for Tiny Photons
The small wavelengths at this frequency lend themselves to super beam forming antenna designs, yielding MIMO on steroids.
Now add Mesh Forming and GEO-ROUTING, and you end up with Gigabit Connections for everyone that buys a radio.
Science pedantry ahoy
"Adsorb" refers to particles sticking to a surface. Oxygen can certainly "absorb" radiation however.
Given the band is 6.8Ghz
A data rate (bps) not far below that should be pretty feasible.
Building hardware that can actually source or sink that is another question.
take all the bandwidth!
you could easily use a spread-spectrum signal bandwidth which occupies all of the 57.1GHz to 63.9GHz open non-licensed frequencies.
The maximum TX power being limited to around 10 milliwatts does imply that to go a kilometre a slightly gainier antenna than 30dBi would be needed, maybe something like an retro-directive antenna array, should have a multi-gigabit throughput. Shadowing is an important term in the 5 millimetre band as propagation is essentially restricted to Line-of-Sight.
I think rather than point-to-point this technology will be used for cellular or ad-hoc networks with metres between access points, around 100m inter beacon-distance on roads, atmospheric attenuation is high!
Around 10x what you get over 2.4GHz WiFi
Probably more than that actually.
Although the last microwave link I used got a hideous bitrate - but to be fair, that's entirely because the mobile phone company had no backhaul to speak of.
(170kbps is a bit rubbish over 3G)
great , now weres the PC USB2 sticks for this
great , now weres the PC device USB2 sticks for this, and as above what real data throughput does it do?
for instance the 11n protocol in these high ranges if the USB2 sticks were or are being made soon, how many usable digital channels would that equate to to get 100Mbit/s.
1 Km RANGE isnt great FOR personal use, but its better that a custom Wifi 11n 2.4 directional arial today i assume!
need far more details, please enlighen us.
South Uisit - Pedant
It might matter more in South Uist than you would think. Currently much of Uist, Harris and Lewis get it's broadband over microwave link.
It's quite conceivable that people in south uist might want to relay broadband over a 1km or so as a range extender or to connect up an outhouse.
The yanks opened this band up a while back but although there are a few manufacturers, the kit seems to be quite pricey and not readily available. Rain seems to be a big issue at this wavelength, so external use in the UK might be a bit restricted anyway.
There is some talk of using this band for WirelessHD but are there any products available/in the pipeline in Europe?
Is it the nissile range?
South Uist sounds like the missile range.
Given the apparent limits of this particular tech, the only risk I can see is some extraneous signal setting off a detonator or igniter, and that seems pretty unlikely.
North Luffenham is an Army barracks now. Air Defence.
You can sort of see connections.
There have been rumours for years of systems which can detect stealth planes by detecting "holes" in the background radiation.
Over 60 dB/km !
That 60 dB/km (due to the oxygen molecules) must be ADDED to normal path attenuation! This makes it practically useless for any link longer than a few hundred meters, considering the 10mW maximum power.
Even though it would still be useful for a Gigabit WiFi or wireless HDMI devices to use within the home - in the same room.
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