Wireless "Pulse" Technology 149
mustard writes "
This is an article in USA Today about a technology that
uses energy pulses to transmit data.
It's fast as the speed of light, cell phones could be as
small as a wristwatch, and you could have only 1 tower
every 100 miles. It uses new chip technology from IBM,
and as an example, they cite that it could support over
2,000 cellphones per block, as opposed to coventional
cellular today which is about 400 per block. But it's not
limited to that, it can be used for cheap personal radar
as well. Well worth a read, fascinating stuff. In a
related story, the inventor of the patent is in a dispute
with a government funded lab who, according to congress,
stole the idea."
Wireless telegraphy (Score:1)
Yes, sparks, even enclosed arcs (up to maybe a megawatt) were used to generate RF.
Imho, the most interesting were the Alexanderson alternators;
these were developed up to the point where they could put out 200 kW at 100 kHz.
Apparently, even today, there is a station/museum at Grimeton, Sweden that is ready to go; and probably not a vacuum tube anywhere. It was fired up in 1996, iirc, on something like 23 kHz for a commemorative broadcast (Morse code).
Interesting item: In Japan, 1956, there was a radio-controlled toy bus that used a spark transmitter (handheld) and a coherer receiver!!
Nicholas Bodley
The main types of Spread Spectrum (Score:1)
Even if I wasn't already quite familiar with spread spectrum communications from having worked with CDMA for the past 7+ years, I'd have noticed the many other snake-oil indicators. First on the list are shrill claims about broad intellectual property rights and how the government is conspiring to steal their revolutionary invention from them.
Of course, the patent system and courts are so utterly clueless these days that I wouldn't be surprised if the main "use" of this "invention" is to extort large sums of money from the legitimate companies in the spread spectrum radio business.
several problems: a technical analysis (Score:1)
commentary on this "new" device on slashdot
so I don't feel the need to say too much but
nobody here seems aware of the background here
or more precisely of the name that has been
stuck on the technology.
This gizmo is called the "micropower impulse radar" or "MIR" for short and was *apparently* developed by some researchers at LLNL by leveraging their work on a really nifty digitizer
developed for use in inertial confinement fusion.
[ Do a search on www.dogpile.com for "micropower
impulse radar to see what's out there]
The IEEE magazine, "Spectrum" did a story on the
device in the spring of 1997. I tracked the article on the web and looked it up on LLNL's web
site. They had some really neat PDF files showing
all the possible applications of the technology.
I was, quite frankly, floored.
For some reason, I can't seem to get any
of the llnl links to work (www.llnl.gov, for
example). I had hoped to provide links
directly to the literature they had put together.
I have no idea who is guilty or innocent in
this patent dispute but as a consumer of
technology I certainly hope that someone develops
this work.
Might be a dumb question ... (Score:1)
The main types of Spread Spectrum (Score:1)
spread spectrum (as opposed to frequency hopping)
and it uses walsh functions in two separate ways:
to channelize the forward link into 64 channels,
and as a power-efficient modulation technique on
the reverse channel that can be noncoherently
demodulated.
As somebody who has worked with CDMA for about 7
years, this Pulse stuff sounds like snake oil to
me. It certainly has all the warning signs.
Question for the inventors of this stuff: what
happens if you're right next to a TV or FM
broadcast transmitter?
Re: Patents and the FCC (Score:1)
Of course the patent isn't on em communications... it's on the Ultrahigh-bandwidth-beamforming/cyclet method he's using. :p Since it's in Fullerton's name, you could probably find it on the patent server.
But you're right - this isn't 'new' technology -- the FCC has snubbed this kind of research since the 70s. "Not use sliced out frequencies? Put cellular antenae in boxes the size of brief cases? Heresy!"
The main types of Spread Spectrum (Score:1)
I read a couple years ago an article, by Fullerton i believe, about how he had come up with some practicle solutions for cellular service (like miniturized cellular attenae, and the like) and approached the FCC about it and they dissed him. That's why he wrote the paper anyhow. But I don't remember for sure.
Seems legit to me - but I don't know for sure.
SETI implications? (Score:1)
Perhaps extra terrestrial broadcasts are being sent via spread spectrum technology in an effort to communicate only with civilizations that have reached a significantly higher level of technology? I mean it's taken us almost 100 years to get to this point since Marconi developed the wireless telegraph.
Of course it's really easy to get locked into one paradigm whether you're talking about radio communications or human ideas and thought patterns. For all we know serious interstellar communications involves a completely different method.
nothing new here: spread spectrum/CDMA (Score:1)
Electromagnetic Physicians (Score:1)
Tell-Tale warning flags... (Score:1)
That's a standard disclaimer. Brought to you by the same legal system that tells you not to eat silica gel and not to dry your hair in the shower.
privacy? (Score:1)
`Undetectable' is a poor word for this. What happens is that if the walkie-talkie is putting out 5W of power on a spectrum spread over many hundreds of MHz, and the exact frequencies chosen / timings given are either pre-arranged and unknown to others, or being changed in a seemingly random way, the signal becomes very hard to notice.
It becomes very difficult to `scan' for a spread-spectrum signal the way one could for a single-frequency signal, as you need a great deal of information beforehand.
This is a very breathless article (Score:1)
Spread-spectrum stuff is not particularly new; combining it with digital stuff and extremely precise time measurements (`time domain' refers to measuring signals in `time space', rather than `frequency space') is pretty cool.
The article is pretty confusing about which of those additions gives you what. The spiffy hand-held radar things are a result of the precise time measurements; radar works by examining return times from radio signals, and measuring these times very precisely obviously gives better resolution. Accurate measurements also makes for less signal necessary as well to transmit a given amount of information; a factor of 100 seems optimistic, but I'm not a radio engineer.
Much of the rest of the stuff -- increased bandwidth, the ability for encryption and signal hiding -- is the result of using digital techniques.
None of this changes the fact that a given amount of frequency space has a given bandwidth and possible information content, however. Encoding things digitally can make more efficient use of that bandwidth for many signals, but using `radio pulses' vs `radio waves' (?!) doesn't change this.
radio energy w/o radio waves? (Score:1)
Oh come on... (Score:1)
Your beef seems to be with the content of the article, not Time Domain. If you have a problem with the wording of the article, try to contact the author of the article.
I agree, this just sounds like radio; however, this sounds like digital communication with radio frequencies. Still sounds a lot better than anything available in the private sector so far. Don't get your panties in a bunch!
This is cool stuff! (Score:1)
800 MHz? (Score:1)
SETI implications? (Score:1)
-cpt kangarooski, who wants to go the the gangster planet from star trek
can someone send me the article please? (Score:1)
http://www.usatoday.com/money/bcovfri.htm
so if someone can send me the html pages i'll be happy
thanks!
--
Time domain indeed (Score:1)
Spatial discrimination would use autocorrelation too, between two or more antennas. Each position would yield a different correlation value, so different sources could be picked apart fairly easily. I guess there could be some spoofing by reflections, collisions, etc., but these could probably be worked around. (In fact pseudorandom timing or frequency hopping would kill those false correlations pretty well).
Through is good, stop is bad (Score:1)
Your brain gets fried only when it STOPS the waves, as it does at the high frequencies that cellular phones use (eg. 900MHz and 1.8GHz). Microwave ovens provide another example: at 2.4GHz, the radio waves penetrate a thick slab of meat no further than a couple of inches max, which is why the outside cooks and the inside doesn't.
So, if you're concerned about fried brains then you should worry more about existing radio technology than about the relatively low frequency stuff that the article was describing, because the power density of the ultra-wideband signal is very low and therefore there is little power transmitted in the frequency slots where tissues absorb power.
The main types of Spread Spectrum (Score:1)
The description in the article sounds like it's about TH, or a hybrid using TH together with something else (probably DS) to widen the bandwidth and provide greater immunity to multipath problems.
Or, who knows, maybe it has nothing to do with TH. Maybe it's the world's first implementation of communication by Walsh Functions.
("No" noise)*1E6= a lot of noise. (Score:1)
Using this TD technique you get huge bandwidth, but this is no suprise - you are using the whole frequency spectrum.
I do not understand why the probability of overlapping pulses from different sources is estimated to be low? With thousands of simultaneous data transfers at a time?
Sounds like a "ramp" to me... (Score:1)
Sounds like a "buy this share" scheme [bbc.co.uk] to me...
privacy? (Score:1)
Shockley and silicon germanium (Score:1)
a. Making fun of the way the article omitted mentioning John Bardeen and Walter Brattain, the names on the first transistor patent,
b. Wondering how two separate elements, silicon and germanium, suddenly became one material.
Shockley and silicon germanium (Score:1)
Spread Spectrum (Score:1)
Heh, my digital communications prof likes to point out that the Spread Spectrum patent is held by the old time actress Hedy Lamarr. A shining example of a geek chick, eh?
URL for some data on this: http://www.ncafe.com/chris/pat2/index.html
Mechanical example (Score:1)
In school, we did a simple experiment to find the natural frequencies of a cantilever beam (beam attached at one end like a diving board). To start with, what you want to do is excite all the frequencies of the beam. As other people have stated, an impulse in the time domain excites all frequencies in the frequency domain. For example, if you tap a beam with a hammer, it will excite all the frequencies of the beam. For verification, look up the Laplace transform of an impulse.
So the experiment goes like this: attach an accelerometer to the beam, plug it up to a computer acquisition system, tap the beam with a hammer, record the accelerometer output, then do a FFT on the data and you will see the natural frequencies of the beam.
The similar situation is the tapping of the hammer exciting all frequencies in the beam. These guys are generating a radio "tap" with electronics.
nothing new here: spread spectrum/CDMA (Score:1)
The claims that this guy's system will lead to a revolution are nonsense. He hasn't succeeded in repealing information theory. And we'll soon have low-power radios the size of salt grains, just by evolving existing technology.
I'm sure the Livermore labs didn't steal this guy's ideas in the sense of reading and copying his work. It naturally follows as a special case of spread spectrum, which the military labs have been pushing for twenty years or more (let the bandwidth go to infinity, so you can send extremely narrow pulses).
Radio pulse != radio wave ??? (Score:1)
-- Give him Head? Be a Beacon?
WRONG (Score:1)
WRONG (Score:1)
No joke, but range is limited to about 2 or 3 km (Score:1)
broadband pulse is older that carrier wave (Score:1)
No Frequency (Score:1)
The signal has *no* frequency. It's just a pulsed radio wave, and will interfere with any other radio signal.
The reason why this is so cool is because it is easier to understand. The closest analogy is Morse code. If you have an incredibly noisy channel that has so much static where you could never understand a voice, you might still be able to understand Morse code because it takes much more interference to obliterate that signal.
The major benefit of using this technique is that everyone will be able to broadcast on whatever frequency they choose. Currently, devices like cordless phones need to run at 27 MHz or 900 MHz. Broadcasting at any other frequency at any other power would interfere with radio, and is illegal. That's because your cordless phone transmits at a relatively high power itself.
Make the signal a pulsed signal, and instead of 100 milliwats of power, you only need maybe 1 milliwatt of power (just speculating). That power level will never interfere with a conventional radio signal, so you can just broadcast without worry. Everyone can run a home network, and it's secure, fast, and reliable.
A MAJOR benefit of this technology is the low power levels. Charge your cell phone, and don't worry about charging it again for the next 6 months. And that's with 8 hours usage a day. Just like frickin' LCD watches and calculators.
No Frequency (Score:1)
``upstart company''? (Score:1)
The devices that this company was trying to build were the size of a quarter, would run for a year on a battery, and would use time-of-flight to determine their position of a network of localizers. Apparently they would work through conductors like metal refrigerator doors. The rationale was that Faraday cages work because the EM wave induces current in the cage metal, which cancels the wave -- but that this only happens with periodic waves -- not pulses.
Aviation Week carries an article about this technology every couple of years. One of the many conspiracy theories is that UWB radars would detect stealth airplanes easily, so all research in UWB is suppressed.
On the other hand, Aviation Week did carry the results of a bake-off between several pulse-radio handheld radios; and Time Domain's was the only one that worked. It could transmit 100 miles on only a few milliwatts of power. Like spread spectrum, not only is this kind of radio very difficult to jam, it's difficult to tell that it's operating at all -- unless you know the pseudorandom sequence. The big problem that the various radio companies had was synching the radios; especially if they were far apart or moving quickly.
If you do the math, though, you'll see that the data rate would have to be pretty low, especially if there are a number of pulse radio transmitters operating in the same space. This technology won't give us infinte channels for cellular phones (or cellular internet) unfortunately.
I'm a big fan of this technology. Fortunately, patents don't last forever, and these should be running out before too long.
Aetherwire information on the web (Score:1)
The 1995 DARPA report, posted at
http://www.aetherwire.com/PI_Report_95/pi_rep95.h
or
http://www.aetherwire.com/PI_Report_95/awl_pi95.p
goes into a great deal of detail about our
technique for generating carrier-free RF communication and ranging. They also link to a disk image of the Ultra-Wideband CDROM they made for a conference last May which goes into the >30-year history of UWB
http://umunhum.stanford.edu/~morf/ss/ss/UWB_CDROM
Check them out if you are interested in the technology, with a minimum of marketing bullshit. These people are the real thing.
several problems: a technical analysis (Score:1)
There were a lot of IT people on that flight, from a lot of different companies in various aspects of the field.
Dark side of the moon... (Score:1)
Perhaps you mean _far_ side.
(Sorry, but it's one of my biggest pet peeves.)
As for putting ALL of our radio science there... how silly and expensive (not to mention far off -- try convincing Congress to spend 100s of billions of dollars).
Plus, it's only a stopgap measure. If this kind of ultra-wide spread spectrum transmission is widely adopted, what are the construction and maintenance crews for the facility going to use? And what happens when we (heaven forbid) start advancing outside of the Earth-Moon system.
A further concern (Score:1)
Doupleplus ungood.
privacy? (Score:1)
Rebirth of the Internet! (Score:1)
SETI implications? (Score:1)
Accidental radio emissions from earth (and any other civilization using spread spectrum technology) are going to look increasingly like noise.
Even deliberate attempts at contact might use some kind of spread spectrum technology, possibly even without a carrier.
What would obvious sequences be for anybody trying to establish contact? Pi in binary? What would they be synchronized to? Does spread spectrum have an advantage over modulated signals for interstellar communications?
it's got problems (Score:1)
But their particular version, sending lots of bursts of digital data without a carrier, is not very nice: it fills a broad band of radio spectrum with noise.
If this became a widely used way of communicating through radio, it would interfere with conventional radio broadcasts, amateur radio, and other uses of the radio spectrum.
Bandwidth wide but not DC to daylight (Score:1)
I find the technique a bit distressing: More data bandwidth by consumeing more RF bandwidth including bands that are reserved or already in use. I hope they can control the output enough that Radio Astronomy isn't screwed up.
I also find it amusing that there seems to be inconsistancy about how difficult the technique is to use. On one hand they say it is real simple and will be very cheap. On the other hand, they say SiGe is what makes it practical. It's so easy we have to use a bleading edge process to make it work. Er, yeah.
Tell-Tale warning flags... (Score:1)
Warning: Contents under pressure. Open with end pointing away from people. May injure small children and pets. Can be fatal.
radio energy w/o radio waves? (Score:1)
Call off the revolution - it's nowhere to be found (Score:1)
In addition, what's that rubbish of making the electronics far smaller? You'll still have to be able to push a certain amount of energy into the air, and that doesn't change the properties of the components much. True, you won't need as much cooling, but certain physics still apply.
Yes, you can encrypt the information far better because you never know when the next burst will come and on which frequency, but that's about the only advantage.
But all in all, please forgive my skepticism, but I'll believe the major breakthrough when I see it.
Time domain indeed (Score:1)
Yeah it probably takes a while to lock on. At first you don't know when to expect a pulse, so any pulse you receive you guess is the first in the pseudo-random sequence. The you listen for the second pulse in the sequence. Of course you could have received a pulse from another of the 1000 users or one of the 255 other steps in the sequence. But since there's a million pulses a second per channel, even if it takes a few thousand pulses to latch onto the right channel at the right time, that's less than a second to sync up.
And don't misunderstand the channel capacity equation. Capacity is proportional to bandwidth and proportional to the log of (1+S/N). So as BW goes up, C goes up, and as S/N goes up, C also goes up. So if you have 1GHz of BW instead of a more typical 1MHz, you can get away with a much smaller S/N. For larger BW and the same capacity, S/N can be smaller - not a degradation but an improvement!
Tell-Tale warning flags... (Score:1)
Heh...great. (Score:1)
Radio depends on carrier frequencies (e.g. 105.5 Mhz FM) to modulate data onto... From what I read from the article, this technology is a simple synchronus serial bus that uses electromagnetic pulses (square waves) rather than carriers (sinusoids). Data could be both amplitude and psuedo-frequency modulated using this scheme, all without interfering with current communications standards and would be highly immune to noise. {unlike slashdot (-: }
-t-
Heh...great. (Score:1)
I hear that Mead Corp has just come out with a combination storage device/display that boasts infinite resolution, portability, and allows for an infinite number of colors to be displayed.
Theyre calling it PAPER. Wow, the world sure is changing.. Heh
privacy? (Score:1)
Well, nevermind that. I'll have to get a whole new radar detector to avoid getting speeding tickets. Shit! It will be interesting to see how feasable it would be to interfere/block the transmissions even if they can't easily be listened to.
``upstart company''? (Score:1)
The other aspects, such as position finding and radar-like mapping will bring us closer and closer to extremely small, hi-tech, borg-like devices and capabilites. I can't wait.
speed and the cops (Score:1)
??? (Score:1)
Sounds like a "ramp" to me... (Score:1)
Sounds like someone is ready to IPO and wants to drive up the share price.
Mike
--
Tell-Tale warning flags... (Score:1)
You said this is a `don't-sue-us-this-is-Sci-Fi' statement. It's actually a fairly standard disclaimer attached to press releases that may affect share prices. However, I am still of the belief that this story is a scam of the "buy this share when it goes public" variety.
Mike
--
radio energy w/o radio waves? (Score:1)
the reporter must have taken the sound of explosions (propagating in vacuum) in Star Wars too seriously.
i think the notion of a radio carrier wave is what went over the reporter's head
Privately held.... for how long? (Score:1)
They say it's secure, so we won't see it... (Score:1)
Some links (Score:1)
Time domain is at
http://www.time-domain.com/technology.html
take a look at Inficom also,
they have made a ultra sensitive receiver.
http://www.inficom.com/
Stuff on web page (Score:1)
privacy? (Score:1)
When they took the second ammendemnt, I was quiet because I didn't own a gun.
When they took the fourth ammendment, I was quiet because I didn't deal drugs.
When they took the fifth ammendment, I was quiet because I was innocent.
Now they've taken the 1st ammendment, and I can't say anything at all.
Radio pulse != radio wave ??? (Score:1)
It must use the same physics, right?
To me this sounds like just a new modulation or something.
I'm not a physician (yet). But I don't see the diffirence.
- Johan Levin
several problems: a technical analysis (Score:1)
Also: Ultrawideband Wireless Communications @ UMD (Score:1)
-Anthony
???Relevance to my original point? (Score:1)
All I do know is that the inauguration of the digital cellular system *was* delayed worldwide until the collective "secret" service (a joke in itself!) organisations could find a way to hack the system - this is an acknowledged, and sad, fact.
I would also wager that this will happen again and again, until personal privacy takes precedence over government prying! If they expect us to be forthcoming with them, why aren't they more honest with us?
They say it's secure, so we won't see it... (Score:1)
Tricorder Anyone? (Score:1)
the article.
It's Direct Sequence Spread Spectrum (Score:1)
I don't see this upstart company having any advantage over other companies that are using DSSS in consumer applications. I've compared CDMA to TDMA phones in the same markets, and my conclusion is that Qualcomm's version of CDMA just isn't the best choice for voice telephony. It might not be the spread-spectrum technology that's the problem, probably the error corection routines and the codec. Still, there's a long distance (in any domain) between what's proving practical right now and the pie-in-the-sky predictions of this article. The engineering trades aren't nearly as awestruck as USAToday is!
Medical side effects? (Score:1)
??? (Score:1)
Or is the pulse technology not on every frequency simultaneously, merely spreading all the individual pulses amongst all of the frequencies at extremely close intervals, thus making it practically the same, anyhow?
I would appreciate any information or clarification anyone could provide on this.
What it is... (Score:1)
I'll esplain it to you Lucy!
One emits a single cycle, just one, thats a monocycle, aimed at 2ghz (for instance) but not terribly tightly controlled so it bleeds over a very wide "band" with the highest power pretty well centered around 2 ghz. The monocycle (pulse) lasts one half of a billionth of a second.Then nothing at all, no carrier no nuthin for about 900 billionths of a second or 1000 billionths of a second then another monocycle is sent. If the space is 900 pico seconds then its a 1, if its a 1000 picoseconds its a 0. (or some similar timing)The wide band width only encodes 1 bit per pusle even though it covers the huge width (500 mghz to 5 ghz for instance)The wide bandwith makes the radio cheap to build and easier to detect the very weak (250 microwatts) and very short pulse. The encoding is done by timing the spaces between pulses. Since we are talking billions of potential pulses per second, there is substantial room for different timing sequences so that many devices can occupy the same band at the same time. It's the timing in the billionths of seconds and the ability to detect the signal at all that are the technological breakthroughs. A very significant factor is the very low power achieved by not maintaining a carrier wave. It makes a solar powered cell phone a real possibility.
Sounds like... (Score:1)
privacy? (Score:2)
Here in New York City we'd be happy to have something that would ensure that the police can see a person clearly outside of a building prior to pumping them full of bullets.
Outside that bit of current events, I imagine that something like hurricane fonts will happen - things that people can use to generate interference. At least I hope such things are common. After all, there are so many things that interfere with my AM reception here at home - from the microwave to my monitor - that I expect that future technologies will evolve associated technologies that provide static as a side-effect.
It just may take some time.
-Peter
Smiley and pizza (Score:2)
I'll be most interested to see whether this thing makes it to market. We shouldn't prejudge it on the basis of just an article or two: really new inventions are rare, but they *do* appear occasionally.
TH/TDMA is not SS/CDMA (Score:2)
Time domain indeed (Score:2)
The fourier transform and the concept of "spectrum" is so deeply ingrained in so many engineers that they have lost touch with the time domain, essentially the "real world". Many things are a lot simpler in the frequency domain, like AM and FM. But for many probelms the frequency spectrum is the wrong tool. I see so many people who don't understand even simple transistor circuits because they try to think in the frequency domain.
So stop talking about spectrum - it is the wrong tool for understanding this technology. Maybe the power spectral density is useful to figure out if you're polluting radio or TV signals, but that's it.
And don't talk about bit synch either. While that's important in conventional communication systems, it isn't here. With a correlation detector, you just sit waiting around until the output of your correlator jumps up - that's the detection of the pulse - then you read your picosecond stopwatch. No need to expect the signal, just detect it. So simple!
If you're unfamiliar with correlation, and want to hear some math, here goes. The correlation of two functions (say f(t) and g(t)) is the integral S(f(t)*g(t))dt. Essentially multiuply the two signals together and then integrate. For two signals that don't look at all alike, the correlation is small. But when the two signals are very close, the integral is much much larger.
So imagine that you want to detect a pulse with very high resolution. At every instant in time you use a little integrator in some electronics to integrate your incoming signal with the expected signal (whatever shape the pulse has). When there's no pulse, the output of your correlator is very small. When the pulse comes along and lines up with the pulse in your integrator, your correlation gets really big relly fast and then small again as the pulse passes.
Try the math yourself: do the integral S(f(t)*f(t-d))dt where f(t) is the e^-3x pulse and notice that there is a huge peak at d=0.
Since the autocorrelation of that pulse (the pseudo gaussian e^-3x) they are using is very very high, you can detect this pulse with very high precision using correlation techniques. Sub wavelength resolution even.
(For all you communications engineers out there, this is the legendary matched filter technique. Except the typical use of the matched filter samples its output at the middle of the bit interval, when its output is supposed to be biggest(for a one) or smallest (for a zero). Here you do the opposite: when the matched filter output is maximum, that's the middle of the bit!)
So all you need is a correlation detector, a really accurate timer, and a pseudorandom noise generator to whiten up your spectrum and allow multiple channels. And if you do some dsp, your timer allows you to turn reflections off of objects into a pretty good radar image. (Except it's more like typical sonar sounding than typical radar).
If Fullerton's correlator is as good as he says, this stuff is very much for real. Believe it!
Homepage URL (Score:2)
Privately held.... for how long?
Time Domain is a pun/inside joke =) (Score:2)
Confusing statement, I guess.
Anyhow, as an example, digital cell phones pollute the radio spectrum, because (quote your favorite signal analysis source, since I'm not an expert) sending a fast sharp clear pulse (dirac deltas!) can be described as an infinite series of signals in differing frequencies (Fourier series, each term describing a different radio frequency)
Did I get that description right?
Anyway, this pulse technique, rather than using frequency hopping to distribute data across many different frequencies and allowing multiple devices to coexist at once, uses many frequencies at once, relying on a time domain discriminator to differentiate multiple devices. I think. I am unsure how they can do this, and perhaps someone else can supplement my data, spotty as it is.
The very use of many frequencies is necessary for ultrafast digital communication, or inversely, the decision to use digital communication forces the use of entire swathes of radio frequencies. Both are the same statement, I think.
It may not interfere with traditional radio frequency devices, but I think they would appear as noise and such to today's digital wireless devices, such as cell phones.
I also imagine this tech doesn't work very well across large distances, say a state or country without conversion to an alternative communications method, though within a city, what with its extremely dense packing of people and devices, it may be perfectly useable and possible. I say it may not work across long distances because each frequency would be attenuated differently by the atmosphere, would reflect differently on the layers of the atmosphere, and may be detected at different times as the originally sharp pulse gets smeared into a fuzzier packet of data.
Still, should make wireless lans a distinctly enticing possibility
AS
Radar detector... (Score:2)
IE, it isn't a directed pulse as seen in a radar gun, so if you don't know the signal coding, I don't see how you can detect it.
Likewise to interfere with it.
If you wanted to just overwhelm them with static, you'd also probably interfere with other legitimate devices, such as your own cell phone, or the cell phone in the car next to you.
Heck, it would also mean that the police could tell how fast you were going if they knew your cellphone coding, without necessarily being able to decode and listen in on your conversation!
I'm pretty sure you can't block a radar gun functioning on this principle except to absorb all the radar with a stealth coating.
AS
Some facts (Score:2)
Cool. I think =)
AS
Patents URLs. (Score:2)
Here are couple of related patent numbers I found, doing a quick search at IBM's Patent site [ibm.com]; search for "Time Domain" and "Fullerton; Larry W." as the Inventors & Companies, look at referenced patents:
There are a good 40 patents referencing [ibm.com] the older, USP4641317, originally filed on Dec 3, 1984.
...I wonder what a prior art search would turn up.?. As the saying goes, a rose by any other name, is still a rose.
Anyhow, just a little FYI. Enjoy!
Livermore did steal it (allegedly) (Score:2)
Upside Today: Was Fullerton ever at Lawrence Livermore, or did they just develop it independently?
Petroff: He made a presentation to an audience that included almost a dozen Livermore people. Within several days they started working on a similar kind of thing, trying to come up with this technology. Livermore's credibility has been tremendously undermined [because of this] and it is becoming less of an issue. But for a long time, there were many people who knew about the Fullerton technology, but they were concerned about investing because Livermore might come in and sue them.
Interview with CEO (Score:2)
privacy? (Score:2)
Some facts (Score:2)
The signal emitted from antenna depends on the derivative (speed of change) of the signal that you drive the antenna with. The usual sine wave has about the smallest derivative - and thus minimum possible effectiveness at dissipating radio waves.
A pulse wave - which has near vertical slopes is _much_ more effective. (example - a toy car with a dc motor using brushes makes enough noise to interruptions when you watch tv. it doesn't use that much power)
A drawback to this is that only sine waves allow you to control which part of the spectrum your transmission controls. Incidentally the first "wireless telegraph" also used pulses - and thus in a given area you could only have one wireless telegraph working at a given time.
So how can one get around this limitation ? One way is to transmit two singals, not one. Imagine that both you and you partner have sources that produce identical noise. Since noise also has big slopes it's transmission is very efficient. You transmit your signal as pulses of that noise. Your partner receives all radio he/she can handle and correlates the result with the noise source he/she has. The output signal should be your pulses. And as pointed out above you don't really need to have real noise - even pseudo-random pulses will suffice.
However, whatever method you choose there is a question of how finely you can tune the receiver. In the case of correlation you won't be able to filter out all stray signals.
Thus I think the bulk of the patents aren't on the method of transmission. Rather, they should be on how tune more finely to the selected bandspace.
Some facts (Score:3)
For example, Qualcomm's CDMA is spread over 1.25MHz around a center frequency in the 800MHz band while a typical UWB system covers over 1GHz starting at around 500MHz.
Conventional spread spectrum systems use frequency hopping or direct sequence to spread the signal. UWB uses a simple and often forgotten form of spread spectrum called time hopping where short pulses are transmitted at pseudo-random intervals. The reason this modulation is used is simply because FH and DS cannot be practically implemented over such a wide bandwidth.
It's not new. It has been used in jamming resistant radars for at least two decades. What's new is an implementation on a single chip which is potentially cheaper than even conventional carrier-based RF technology at large quantities.
The primary advantage of ultrawideband is its insensitivity to fading. Narrowband transmissions can experience significant attenuation of the signal due to signals travelling through different reflection paths canceling out each other. A wideband signal is virtually immune to this and therefore requires about 20db less power usually taken as a safety margin against fading.
Ultrawideband systems can communicate over significant distances using a lower power spectral density than the electromagnetic noise generated by a typical computer.
The primary limitation to using ultrawideband systems is the wording of part 15 of FCC rules - apparently while your computer is allowed to pollute the spectrum for no good reason it is not allowed to transmit the same power INTENTIONALLY.
The FCC has issued a NOI (Notice Of Inquiry) seeking comments on possible change to these rules. Opposing comments come from the usual suspects: mostly users of the restricted bands such as government agencies.
Links:
Ultrawideband working group [uwb.org]
Aetherwire [aetherwire.com] - makers of an ultrawideband gizmo called the locator which is both exciting and very frightening.
privacy? (Score:3)
How can the same tech that allows directional distance pinpointing of a handheld cellular watch also be undetectable and untraceable in a marine communications device?
I would imagine the directionality and distance is a direct product of data smearing, that differnt frequencies and such of the same data pulse would travel at different velocities, so a single pulse train, under observation, can be analyzed to figure out how far it traveled, and the relative direction if an array of 3 receivers were used to determine which gets distorted most and least to triangulate a direction
AS
several problems: a technical analysis (Score:4)
First: An extremely short pulse approximates a delta function, which has infinite frequency content; "DC to daylight." This is still a form of RF transmission, it just happens that you are dumping energy into a very wide range of frequencies.
Second: Transmissions using this technique _do_ interfere with other RF transmissions. In fact, they interfere with _all_ other transmissions, but that interference is spread over the entire spectrum so it does not interfere with any one frequency very strongly (this raises FCC regulatory questions). In addition, a time-domain spread spectrum encoding makes the likelihood of interfering with another pulsed time-domain spread-spectrum transmission very small, if a good spreading algorithm is chosen.
Third: This is not a new idea (we were looking at this a few months ago for a data transmission application) and there is a reason why this hasn't been widely implemented: timing. In order to receive a pulsed time-domain spread-spectrum signal, you must synchronize your receiver's spread-spectrum decoder to the transmitter's encoder. The shorter the pulses, the more exact the timing and the more difficult this synchronization becomes.
Here is an analogy:
Imagine transmitting a signal by encoding it as a time-varying sequence of baseballs being fed to a pitching machine. The receiver catches the balls, decodes the sequence and reconstructs the signal.
If the transmitter is the only one pitching, the task of decoding is easy.
The problem is, the transmitter is not the only one feeding the pitching machine -- the noise in the environment is also feeding balls in. The best way to encode the signal to avoid any particular noise source (and to avoid interfering with anyone else) is to make the encoding look as random as possible, which is what spread-spectrum encoding is all about.
The resulting stream of baseballs looks random, since it is a combination of a spread-spectrum signal and random interference. In order to decode the signal, you want to catch only the balls that represent the signal.
In order to do this, you install a shutter in front of the receiver -- the spread spectrum decoder -- which will only let the "signal" balls through. This requires the decoder driving the shutter to be exactly synchronized with the encoder.
As the pulses become narrower, the "balls" are coming faster and timing the shutter must become more exact to exclude non-signal balls. If a non-signal ball passes through the shutter (or a signal ball is missed), the error will break the syncronization between the tranmitter and receiver. Narrow pulses also make it more difficult to lock the receiver's decoder to the transmitter's encoder in the first place. Once the pulses become short enough, maintinaing synchronization becomes almost impossible without an additional, non-spread communication channel. If an additional, non-spread chanel is used, then you are back to the problems of ordinary RF transmission.
There is great potential in this technology, but the technical chalenges (and regulatory hurdles) are large.
Rich