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Coming Soon: Ultra Wide Band
JScarpace writes: "Robert X. Cringely has a new article in which he talks about Ultra Wide Band (UWB), a new wireless communications technology which may allow wireless networking speeds up to a gigabit per second. Read the article."
Here's a FAQ from the Ultra Wideband Working Group.
It's not clear that it will be allowed to be deployed widely, since it may in fact interfere with the spectrum allocated for other uses. As the U.S. Governmetn's Ultrawideband (UWB) Signal Characterization Project says:
Many claims have been made that UWB communication transmitters can effectively share spectrum with existing users. Some of these claims have not been independently verified.
We'll have to wait and see...
More likely UWB will compliment GPS nicely. GPS will be used for wilderness, nautical and aviation. UWB will be used to supplement GPS by giving much more accurate measurements in the urban and sub-urban areas -- where 80% of the population lives.
+/- 6 meters isn't good enough for things like parking cars; locating stores/kids in malls; densely populated areas and it really sucks for vertical distances. Yes, differential GPS with ground stations really helps, but UWB could make location-based information and services pervasive.
UWB has a lot of potential.
Learning HOW to think is more important than learning WHAT to think.
Bullshit.
There is so little bandwidth in those low frequencies that you can hardly talk about "ultrawideband"! If it wasn't clear that he doesn't know what he was talking about beforehand, that statement should have made it clear.
"Ultrawideband" is really not anything other than a marketing name for direct-sequence spread spectrum (DSSS). It has been rebranded in no small part in order to attempt to get the FCC and similar regulatory agencies to allow it to be spread across already allocated radio bands (where they become part of the noise floor) rather than confined in between narrowband applications.
All of this really isn't anything particularly earth-shattering. The standard electromagnetic spectrum frequency domainis given by a Fourier transform of the electromagnetic wave using sine waves as base functions. Spread-spectrum technologies simply create a new "frequency domain" use a different set of base functions. They are resistant to interference or jamming only because most sources of interference or jamming operates in the standard frequency domain, not in the "alternate" one. 802.11b actually uses direct-sequence spread spectrum (spread across a fairly wide 2.4 GHz band officially used for industrial applications and microwave ovens) already -- the security added by DSSS is automatically removed by the fact that you can buy 802.11b-compatible waveform correlators for a few hundred dollars at any electronics store. Sorry guys, you still need encryption.
>I have questions though:
>- Can an enthusiast make one of these "impossibly cheap" devices?
Yes. Schematics and parts are readily available.
>- Are as the article suggests these devices really going to take off within the next year or will they be suppressed as the article suggests other technologies will be.
There is a patent conflict. Thoma McEwan of Lawrence Livermore Labs copied Time Domain's ideas and patented them. Manufacturer's will face litigation expense and could end up paying royalties on both.
>- Is it really that resistant to interference? We're using so many frequencies at one time, can they really not clash?
Yes. Spread Spectrum works now by switching frequencies in a pseudorandom sequence. Receivers that are not on the same sequence cannot hear the transmission.
UWB works on the same principle except it uses time slots instead of frequency slots. Receivers that are not on the same time sequence cannot hear the transmission. As mentioned, UWB is highly secure and difficult to detect for this reason.
>- Will it interfere with traditional radio signals? I.e, it seems to clobber other reserved EM frequencies to make use of high bandwidth. Would this mess up our telly or radio?
Probably, but only if the transmitter is very close (several feet) and you are trying to listen to a very weak signal.
If many transmitters are in use nearby, it may affect GPS by raising the general noise level. GPS works on very weak signals.
- Does anyone have experience to say whether this stuff is really as good as it proclaims to be?
A lot of people have worked on it with good results. Yes, it works.
The antennas have to be specially designed for broadband. They may be larger than practical for handheld phones, but fractal antennas may reduce the size.
- Finally, there must be more downsides than just messing up radio astronomers
It can raise the general background noise level and affect reception of weak signals. However, in an urban environment, there are plenty of signals that already raise the noise level. Radiation from Local oscillators in superhet receivers (probably hundreds of thousands used at different frequencies), cellular phones and other mobile transmitters (this really is bad for radio astronomy), industrial process like arc welding and power conversion, motor starting transients, automobile ignition noise, temperature controllers using bimetallic sensors, light switches, ad infinitum.
Electrical noise pollution is a part of modern society. The noise added by UWB may well be lost in the background noise that already exists.
Mike Monett
mrmonett@yahoo.com
I'm no engineer, but what little reading on it I've done suggests it works like this:
Think about your normal physical line. It sends data in a sequential form.. first a 1, then a 0 , then a 1, then a 0 and so on. Now admitted, it does this ridiculously fast but it's still sequential. (This is a huge simplification, btw, but it's the general gist)
Now UWB is using a whole bunch of frequencies to send those ones and zeros, but each frequency carres a different bit. So the first frequency carries a 0, the second carries a 0, the third carries a 1, the fourth carries another 1, and so on. The trick is, it sends these all at the same time and it's up to the receiver to not only know exactly WHEN those frequencies will be carrying information to it, but put them together into the proper sequence of bits.
It's the difference between getting hit by a steady, narrow stream of water, and getting hit by a single tidal wave. They'll both get you wet, but one will do it a lot faster.
So that's the faster.
The cheaper is that a physical line requires a way to code and decode the information and.. well.. a physical line. Which means you have to pay for the line, you have to pay for running line through cities and into people's houses, you have to pay for when a bad weatherstorm comes and a tree busts the line, you have to pay licensing fees to lay all this line, etc.
UWB requires a more sophisticated coder and decoder, but since it doesn't require a line and microchips are so cheap these days, this comes out to be a much lower cost - especially if the FCC lets it go unregulated.
Now as to how it avoids interfering with each other, I really don't know, because if you have enough of these devices, you would think that sooner or later *some* of them in the same area will be sending at the same time.
That Jesus Christ guy is getting some terrible lag... it took him 3 days to respawn! -NJ CoolBreeze
Ultra wide band communication isn't so damn fancy conceptually. The problem is is practically difficult. It works on the same principals as regular sized band radio transmission with the small difference of not splitting the band into channels. Channels are just time slots you set your transciever to listen to or send on which arej ust portions of a band. With UWB there's no channel designations so reception and transmission frequencies can be all over the specified band. It sounds like a good idea because there are not channels to occupy or share with others and your beeps all over a band can be construed as static rather than interference. A random beep in the middle of a frequency used for aviation radio isn't going to crash a plane as it is catagorized as static.
The problem with implimenting UWB is getting the electronics to move fast enough. In order for me to send lets say my voice over UWB I need electronics in my transmitter that can switch really quickly between enough frequencies in order to give me the aggregate bandwidth to send my voice signal. Easy you say modern CDMA cells phones already do that. Granted they make the most of their radio spectrum by splitting up data over the entire band but they are splitting up big chunks of data over a limited band. UWB transceivers will have to switch fast enough where a single radio blip might only be half a word or a quarter of a word and switch over a much higher range of frequencies.
In order to have a gigabit of bandwidth your transceiver would have to switch frequencies in excess of a billion times a second (not merely transmit at a billion hertz). It takes x electronic clock cycles to switch the electronics to switch frequencies you'd have to have electronics working at xgigahertz in order to send a gigabit of data. In a handheld unit? Not likely in the next couple years no matter how fast microprocessors get. Companies have just recently been able to build circuits that can switch at 10GHz it will still be a little while before actual logical circuits can be mass produced and run on batteries. Handheld devices are going to have the same amount of information throughput as they have now even if the radio band they work on is a good portion of the radio spectrum. There is alot of engineering left before UWB is really a viable solution to any problem but it is still a cool concept and I hope these problems get worked out sooner than later.
I'm a loner Dottie, a Rebel.
I think several (highly modded) contributors to this discussion are confusing
the concepts of information bandwidth and frequency bandwidth. Ultra-wideband
refers to the bandwidth in the frequency domain, which is only indirectly
connected to the concept of information bandwidth, in that a wide band in
the frequency domain translates to narrow pulse in the time domain. Coding
techniques also strongly affect the ultimate information bandwidth of the
system. UWB is nothing like IEEE 802.11b,
which operates in the narrow 2.4 GHz - 2.483 GHz band.
I have been working on a project for US Army STRICOM,
in which we are using 8 UWB devices manufactured by
Time Domain Inc. to perform position location. These devices
operate at 1.9 GHz center frequency with a 2 GHz bandwidth,
which translates to a 500 ps pulsewidth.
We have a short conference paper on UWB simulation, accepted for presentation
to the 2002 IEEE Antenna and PropagationSociety Symposium,
which you can access
here. Speaking in general and rather simplistic terms, the information
bandwidth of such a system would depend of the time frame over which you
will allocate these 500 ps slots to listen for the transmission of 1 bit
of information. For example, if we choose a 5 ns time frame, then we
could theoretically obtain 200 Mb/s information bandwidth, while (ideally)
allowing for 10 channels of operation. Of course, the previous analysis
neglects the need for redundancy, and you may want to choose a time slot
over which to listen for a pulse different than the pulsewidth itself, but
I think the discussion gives one a good idea about how to relate information
bandwidth to frequency domain bandwidth in a simple communication system.
Yes, Cringely doesn't understand 99% of the technology he writes about. That does not make the technology bullshit.
UWB is real. It's as close as it gets to a free lunch, and Claude need not turn in his grave.
you can build it, and it's all true... if there's only one such device
Not correct. UWB devices share the spectrum just fine. In fact, it's a far superior way to share the spectrum than narrowband frequency allocations.
The problems start when different devices use very different power levels: GPS uses extremely low levels, TV stations use very high levels and almost anything is at very high levels if you are close enough to the transmitter.
Spectrum sharing by frequency allocation provides very good separation between bands that use widely differing power levels. It's not too difficult to build filters that reject out-of-band interference by 100db or more. With ultrawideband, the rejection of unwanted signals cannot exceed 40-50db. UWB will work very well if all narrowband communications below 1GHz are shut down. Since that will never happen it will probably remain limited to very low power levels and certain niche applications.
Here's what might happen if all narrowband transmissions *are* shut down:
UWB cells for "last 10 miles" delivery, combined with long range fiber and satellite infrastructure could bring 100kbps to almost any person on earch and 10mbits/second to anyone living in a city. The terminals will use very little power and can have long battery life. Location tracking with 20 centimeter accuracy will be available anywhere in a city, including indoors.
How is all this possible with just 1GHz of bandwidth? The utilization efficiency of spectrum should not be measured in bps/Hz but rather in bps/Hz/square Km. Today's cellular infrastructure uses a very crude form of frequency reuse to optimize this capacity. IS-96 CDMA barely begins to utilize the real advantages of spread spectrum with a bandwidth of 1.25MHz. With 1GHz of spread spectrum things start to look different. And it's not just the bandwidth: 1GHz at a center frequency of 15GHz can only be use for line-of-sight communication. If the 1GHz band has a center frequency of 700MHz it has much better propagation and is immune to fading.
Of course, this will never happen. But not because it is mathematically or technologically impossible.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.