Slashdot Mirror
Wireless "Pulse" Technology
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."
They are talking about using pico seconds, or trillionths of a second to send the data, but that was already in the article and website.
I've been amazed reading the comments on this. You have the (rather large) group of cynics who immediately dismiss everything as old/snake oil/not feasible/etc, and then a few others who actually go read the material and are interested in it. The cynics don't do much reading, they pick up a few points, make some generalizations and then say their criticism and cite things like "this just sounds like CDMA and spread spectrum, and that's been around forever." when the material discusses this technology in relation to the former things.
Of course this is just an example, in all, it's suprising that alot of this has stayed on topic, instead of 100+ comments totally off topic.
What a bunch of cynics everyone has become. Maybe people should do a little more reading and a little less generalization. (realizing that I'm generalizing myself in this post)
Yes, but... I'm reasonably sure that the reactances (probably including the antennas) were shock-excited, and rang at their resonant frequencies. Dig casually into the history of wireless (the 1910 variety, not the 1990 variety), and you'll soon read of "damped waves"; there was intense effort made to create a continuous wave (CW), and success was a significant accomplishment. In a previous post, I mentioned the Alexanderson alternator, an amazing device. Carbon microphones (some with water cooling!) had RF going to the antenna passing through them. This was before tubes. Dig more deeply into wireless history, and you'll probably find waveforms, although practical 'scopes came along about the time taht spark xmitters became illegal. Nicholas Bodley // nbodley@tiac.net
Ok folks, I dropped a brief note yesterday about the history behind this technology but the llnl
links were all down. Here is where you can go
to learn all about it:
First this link is the home of
"micropower impulse radar" or MIR at www.llnl.gov.
http://www.llnl.gov/IPandC/op96/10/10o-mic.html
I quote here the basics:
---cut here---
LLNL's micropower-impulse radar (MIR) presents a new paradigm in
radar technology. MIR uses $10 of off-the-shelf components to
outperform conventional radar and sensor equipment costing as much
as $40,000. Both the radar transmitter and receiver are contained in a
package measuring just two square inches; eventually the microradar
is expected to be shrunk to the size of a silicon microchip.
Outgrowth of laser technology
The technology is an outgrowth of the world's fastest solid-state
digitizer, which was designed to measure sub-nanosecond events
generated by fusion experiments on the Laboratory's Nova laser. MIR
is based on the radiation of short voltage impulses that are reflected
off nearby objects and detected by MIR's extremely high-speed
sampling receiver. Prototype units emit one million impulses per
second and then detect their echoes within ranges of 20 feet, or further
with the addition of synthetic beam forming antennas. The microradar
can be preset to detect stationary objects within a precisely defined
range as well as any motion within that area. MIR can penetrate
materials such as rubber, plastic, wood, concrete, glass, ice, and mud.
The technology already has been licensed for electronic studfinders,
automotive safety products, and industrial automation. Discussions
with hundreds of interested companies indicate there are many
products that will be improved and reduced in price by MIR. The
application box provides a partial listing of the many other
fields-of-use that are available for licensing.
Availability: We are not an equipment manufacturer; therefore our
goals are to (1) license MIR to qualified companies who can develop
products, (2) continue to develop variations of the MIR for our
Laboratory mission, and (3) seek out new ideas for future directions of
this exciting technology.
---cut here---
Let me put it this way: /. saying this kind of stuff without much further investigation.
Frequency domain analysis is useful because aerial length -- analogous to carrier frequency.
Therefore for mobile telecoms we are talking about 1-10GHz ?
So those "pulses of radio energy" have to be modulated (can't send DC), which reminds me of an ASK senario.
I've written a big essay on GMSK (GSM modulation) (can't prove it:) and I _can_ tell why its bull by reading
only a few lines of it.
Lets face it, anyone who knows about wireless technology can, reject an article
posted on the web and appeared on
Cheers
From Shannon it follows that radiated power and bandwith are exchangeable :
C = B*blog(1+S/N)
C=capacity(bit/s) B=bandwidth(Hz)
S=signal(Watt) N=noise(Watt)
This system uses a very high bandwith and a low power source. From "Impulse Radio Overview" :
* 1000 simultanious telephone calls. The transmitters do interfere since they generate noise for non-correlated receivers.
* 2 GHz center carrier, 1 GHz -- 3 GHz half power bandwidth.
===> 2MHz/call
Current TDMA GSM systems use 20 kHz/call. This is a very robust low power BUT low capacity system.
No, think "duty cycle." It's OK to fill the entire radio spectrum with broadband noise, as long as you only do it for about 0.00001% of the time.
The question I have is, how is the S/N ratio of such a system characterized? S/N ratio of a channel degrades as 10 * log(bandwidth), so when you start talking gigahertz bandwidths, you are talking almost 90 dB of S/N deterioration over a narrowband signal. Recovery of any useful data in such a bandwidth must be tough, to say the least.
It's outlawed in most of the US.
The shuttle does use spread spectrum through TDRSS, but that's a newer system developed in the late 1970s and deployed in the 1980s.
What about Qualcomm's CDMA system don't you like? The error correction codes are actually quite a bit stronger than those in GSM, and the vocoder is also quite a bit newer, being based on CELP rather than residual excitation.
The first versions of the CDMA system used 8kb/s (peak) codecs, while the ones most commonly deployed now use 13 kb/s (peak), same as GSM. But because the codec is more efficient than GSM's it sounds better for the same data rate.
Comments about impact to the world...Check.
Comments that "This has been done"...Check.
It's a 21st-century spark-gap transmitter!!.......Check. Not being such a technically minded fellow, I found a little legalese that may be much more telling than all the gee-whiz technobabble. Let's take a look at their Securities Disclaimer available (as a link) from the front page . It says:
It's a "don't-sue-us-this-is-Sci-Fi" statement. Doesn't that really tell you what these snake-oil salesmen are all about (and after?)
The trekker in me would love to see some of this stuff work. I will admit -- some of the applications worry me. Who says (without sounding too paranoid) that certain factions (cough) NSA (hack) don't have these capabilities right now?
Any physicist could tell you that a radio pulse is equivilent to a transmission on all radio frequencies at once.
Anal Sex IS illegal. It's called Sodomy. :P
If anyone is curious, here are the patents filed by "Larry Fullerton":
US Patent Office Search Results
`Personal radar'. Great. As if it were not enough with being immersed in all that cellular crap.
Do you know that phones sold in the EU will have to start coming with a warning label, like cigarette packs?
Exactly what laws of physics and mathematics are being disregarded? I didn't see any particular snake-oil flags in the overview paper, at any rate.
Next step, ubiquitous law enforcement :(
It does not appear to be snake oil, actually. Look at the overview paper on http://www.time-domain.com.
If anyone is curious, here are the patents filed by "Larry Fullerton":
US Patent Office Search Results
If that fails, search for "Fullerton; Larry" as the assignee/inventor name at http://164.195.100.11/netahtml/sear ch-bool.html.
Here is Time Domain's home page. Very interesting. http://www.time-domain.com/
According to the USA article, there are two separate "newsworthy" issues here: first, little company vs. the government on a patent issue; and secondly, SEVERAL bigger companies vs. government on a non-delivery-of-technology issue (i.e., government says one thing, actual technology does even less). The case on this second issue is that the plaintiffs were not advised of the weaknesses of the technology (i.e., it runs on the same frequencies as air-traffic contoller transmissions), and that they assumed the government would advise them of these shortcomings.
" joke, there are two different sides to this issue: first, the plaintiffs can easily argue that the governemnt SHOULD'VE told them of these weaknesses, since it was the GOVERNEMNT who did all the testing; on the other hand, it seems that the palintiff can very easily "play dumb and ignorant" and make the governemnt their fall-guy.
Now, beyond the old "that's-what-you-get-for-trusting-your-government
Here lies a serious problem in the certification process of government-use systems/technologies. Had the plaintiff been de-briefed of the limitations, production would had been slowed down by at least four-five months.
Sorry, but you seem to have missed at least two // nbodley@tiac.net
crucial points; one is that this is micropower,
and the second is that the pulses are really narrow.
Didn't you read that the effect is that ordinary
narrow-band equipment simply "thinks" the noise
level has risen just a wee bit?
Nicholas Bodley
As an old radar technician, seems that the // nbodley@tiac.net
technique in the receiver uses extremely narrow
range gates, precisely timed. Maybe I need to do
more homework.
Nicholas Bodley
I won't pretend to say anything about the lawyer end of things, but the science and math is fine.
TDS is not pretending to invalidate Maxwell or Shannon.
And it isn't invalidating CDMA.
What it is ''invalidating'' is exp(i*w*t)*m(t)
as a particularly useful guide to actual implementation.
All forms of communication require some sort of synchronization, and then, some sort of generalized 'orthogonality' to select among channels. How exactly you do this is the key
What TDS does is to directly apply the signals to create honest-to-god electromagnetic waveforms of the desired functional shape---not in the envelope approximation.
The really ''big picture'' conceptual issue is how to profitably use the bandwidth from NNN GhZ -> light.
The point is that it eventually is no longer easy to divide the spectrum up into (w1,w1+dw)
(w,w2+dw2) et cetera discrete frequency chunks.
It is just too hard---in practical implementation---to use conventional FM sorts of transmitters and receivers with all their very HF oscillators in them.
The goal is to sum up, in one enormous chunk, ALL of those ultra high frequencies in a single transmission and detection mechanism that may have very strong practical implementation advantages.
With conventional communications you have to have oscillators somewhere around your carrier frequency, which gets more and more expensive the higher frequency you go, and you're expending energy to keep them going. Receivers also have to have similar oscillators, which, the higher frequency you go, the more they tend to re-radiate back out, again costing power.
As far as 'snake oil' goes, this type of idea is used in advanced military radar.
Well, how can you be so sure that I have no idea?
Maybe I do.
Since I'm the anonymous coward there is no way to prove anything and no point in discussing whether I know about this stuff.
"Forget the obsolete radio waves which are not transferring any energy but send pulses of radio energy instead"
"It as good as light bulbs and the age of darkness"
Wow!
I am not exactly sure if you accept what you don't understand and sounds "C00L D00D".
If this is CDMA, it's not new, and it's not interesting.
Here's something for you to chew on:
p ie94.html
http://www-dsed.llnl.gov/documents/imaging/emjs
You're absolutely right.
The old EMP.
Carrier or not Faraday is spinning in his grave as we speak 1998 and someones patented the EM communications. It's radio all right. It's a sad day when your response get's 1. I almost wrote the same thing myself but what the hey.
Looks like the trained mamals at slashdot need more training.
That uses quantum entanglement for data transmission.
The police don't have to do much except sit there and watch. And rake in the dough.
Cool info. But how do you figure the initial synchronization works? It strikes me that the receiver must listen for a very small signal in a very large bandwidth, in order to lock onto the transmitter's pseudo-random sequence. S/N performance degrades as 10 * log(bw), and it seems you'd have to "listen" to the entire 1- to 2-GHz spectrum in order to acquire the transmitted signal.
> Or, who knows, maybe it has nothing to do with TH. :-)
> Maybe it's the world's first implementation of
> communication by Walsh Functions.
I thought that Code Division Multiple Access (CDMA) used Walsh Codes. CDMA is used in many
of today's digital cell phones.
-AC
--
Try the new linux-based search engine at http://www.NationalDirectory.com
That much rock would make a damn fine RF shield. Low gravity would allow HUGE antenna structures. How about a nice mile wide crater as a dish? :-)
TK
Now you people should be ashamed for posting that. ./
No need to read more than the first paragraph to see that its a buch of crap.
"It doesn't send radiowaves but energy pulses"??!? or something
Right something more interesting than this. Like doctor Zodak's from
Otoio village who discovered that an unlimited amount of power can be produced by
a 1cm battery if we take advanage of its mass loss between the two poles. That together with
instant discharge of neutrons can create astonishing things noone until today had though of and
which are good to make doctor Zodak rich and make an article on
A more practical use would be neighborly voyeurism.
Considering the extremely-close time discrimination of the receivers,
in shouldn't be too hard to clock a receiver with
a precision, low-jitter clock and slide the time scale to coincide with
the pulses from a pulsar.
Your description is correct. If you do the fourier transform (that is, convert from time domain to frequency domain) of a pulse (dirac delta function) you get all possible frequencies.
:)
This was quite well demonstrated by the way the electromagnetic pulse from a nuclear bomb test screwed up electronic transmissions across the entire spectrum.
Seems that metal lath for plaster should make a // nbodley@tiac.net
decent Faraday cage; just needs bonding wires (for
low frequencies.).
Nicholas Bodley
According to these same laws, Electromagnetic Pulse (EMP) exists - and this seems to be a lower-powered, more consistant variation on the theme.
Did we even have an inkling of the possibility of Nuclear Energy, Atomic structure or Theories of Relativity before Einstein, Bohr & Fermi.
Times change - and so does knowledge.
Way back when radio transmission was a new idea, before we knew how to modulate carrier waves, people used to make "spark gap transmitters." Basically, these devices would controllably discharge a huge spark, sending EM noise all over the spectrum. A non-tuned receiver could then pick up the noise caused by this discharge, and interpret it as morse code, or whatever. Its great to know we are back where we were 100 years ago. I am sure the FCC will just love having these people pollute the whole specturm.
Unless they outlaw anal sex, I won't be doing anything illegal in my house so I'm not worried.
How many times have you wanted to get a hold of
someone, paging them, calling them on their cell
phone, only to get voice mail, or no answer...
well with this you could see where your buddies
are instead of waiting around for people.. this
would be really cool.. if your cat got lost you
could just look where it is! - i know this is
nothing new.. but my cat hates wearing that big
honkin' gps on it's back!! it's about time these
things became mainstream..
vehicle stolen? - look there it is at the corner
of 5th and main!
possibilites would be endless!!
-bastard
bastard.6o4.org
mainly with terahertz laser beams to see
inside rooms etc.i think metal used to stop em.
i dont see how a radio burst can see through
a concrete wall however..
Keep in mind the internet is global... And even in the US it's determined by state laws, not a federal law.
kewl. now we'll have see-thru battle tanks.
everyone seen the stuff on time domains web page ?
Your comment is puzzling; I'll let it go. However, // nbodley@tiac.net
what we forget is that silicon is a much more-difficult
material to work with than germanium. IIrc, GE was
so proud of doing something useful with silicon
that when they invented the controlled rectifier,
the first word in its name was "silicon". Of course,
there are probably a few clueless souls who type it
as "silicon-controlled rectifier"; implying that it's
a rectifier controlled by silicon. Other clueless
types call it a silicone controlled rectifier... Nicholas Bodley
Depending on where you live, it may already be illegal.
"Give up on the spectrum concept! You're listening in the time domain for a specific time-domain waveform."
Right, that's the idea. But unless there is something I am just not seeing, you DO have to listen in the frequency domain to gain the information you need to synchronize a link in the time domain. Only after the two endpoints' pseudorandom sequences are synchronized do you gain the ability to "time-discriminate" against a gigahertz' worth of essentially random noise. That first step -- synchronization -- has got to be the killer. I don't see how a correlator can help with this.
Good point re: channel capacity, though.
Won't converting digital data to/from time space and frequency space introduce errors which may be a big problem for digital data?
Wow! You certainly are wise in the ways of Physics. I'm glad you're here to keep of clear of the snake oil salesmen of the scientific world. I can't believe how often dozens of Physics PhD's, military agencies, law enforcement agencies AND FEMA are suckered into these little schemes.
So you logic is: the claims are amazing, therefore they must be false. sic. Or perhaps: because they are amazing claims and I don't understand them, they must be false.
Please think before you submit! This has all the markings of a technology which may someday become powerful. Maybe not. But to dismiss it as garbage before understnding what they are talking about is foolish.
I believe the idea is that the spectrum is so wide band that it is below the noise floor and has negligable impact on existing devices.
The last days only Rob has been submitting articles, all in a daily burst of about an hour.. then nothing for the rest of the day. That's boring.
Square waves have a 50% duty cycle. This technology deals with extremely narrow pulses, not square waves! Also: The first harmonic is the fundamental; reason is, that defining it that way simplifies the math. The harmonic that has (e.g.) a frequency 13 times the fundamental is 13 times its frequency, not 14. Nicholas Bodley // nbodley@tiac.net
ummmm.... actually, everything you mentioned is still a sinusoidal wave. find out what you are talking about before you post things like "If it's not sending video, then it's called radio". Video is information not a signal... it is comprised of luminance signals and chrominance signals. there is much more than what you think
One can be skeptical without either accepting or dismissing. Need a position be taken?
Dismissing this technology as "a bunch of crap" is clearly a method of explaining away something that seems complex, too good to be true. If you really want to be helpful, why don't you get out some Physics or EE texts and disprove what they are claiming. This is why the Scientific Method is so great. Claims must be proven. Once proven, they must be shown to be false by some other method. No, sir. You don't get off that easy: "this is a bunch of crap, and you don't know who I am, so I don't need to back up my words with fact, or furthering any discussion on the matter"
The whole situation reminds me of the child who ignores anything but his own opinion and then plugs his ears with his fingers.
Plug your ears if you like, but that merely relegates what you've been saying to the garbage.
If you think your opinion is important, then back it up!
--"Why should we think this technology is crap?"
--"Why should we believe you when you dismiss this as bull?"
If you wish to make legitimate challenges to this technology, I suggest investigating the links Time-Domain provides on their technological overview page: http://www.time-domain.com/technology.html
As for myself, I don't claim to understand everything about this technology, but I will investigate before I either accept it or dismiss it.
Isn't that what Spread Spectrum is?
-alx
Whats ./ ?
I ate my tag line.
-=Ellis (D)25=-
Hmmm.. What about AM, CB, SW, LW, ect..ect..ect... All still radio..
If it's not sending video, then it's called radio...
I ate my tag line.
-=Ellis (D)25=-
Wireless telegraphy *did* use antennas, and big ones, too. // nbodley@tiac.net
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
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.
There has been a significant amount of intelligent
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.
Yes, but the various error sources are well-understood, and have been for decades. The Shannon and Nyquist sampling theorems are examples.
Correct. IS-95 CDMA uses direct sequence
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?
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!"
Read Heinlein's 1953 Revolt in 2100, now more than ever.
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.
Read Heinlein's 1953 Revolt in 2100, now more than ever.
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.
There's too much blood in my caffeine stream!
Anyone remember who was the "inventor" of Spread Spectrum ? None other than the 40's movie star Heddy Lamar ! She came up with the idea as a way of making radio control of torpedos un-jammable during WWII, but the technology wasn't quite feasable at the time.
Many of them carry pagers.
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.
`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.
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.
Square waves are created by taking the sine of the fundamental, adding 1/3 of the 3rd harmonic, 1/5 of the 5th, 1/7 of the 7th... etc. its all the ODD harmonics added together at their respective energies
Y'all are being too picky.
:^)
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!
Stating on Slashdot that I like cheese since 1997.
Although they get it all wrong in the article (of course this uses electromagnetic waves, they are just shaped differently), this looks like promising technology. Go read the papers on the website.
Try something more in the PCS band- something in the 1.9 GHz range more like. The rest of the details sounds right though...
I am not merely a "consumer" or a "taxpayer". I am a Citizen of the State of Texas
Obviously the space men developed RFC 1149 before developing April Fools's Day. It's tricky to broadcast that sort of thing over interstellar distances you know. Unless they have also developed Gallagher.
-cpt kangarooski, who wants to go the the gangster planet from star trek
-- This and all my posts are in the public domain. I am a lawyer. I am not your lawyer, and this is not legal advice.
because our proxy have a filter on *money* so i cannot check the link
http://www.usatoday.com/money/bcovfri.htm
so if someone can send me the html pages i'll be happy
thanks!
--
"Science will win because it works." - Stephen Hawking
That seems like a reasonable way to communicate, but my first thought when reading all the references to positioning was that it used spatial position to discriminate transceivers. There was something about Bell labs doing this on slashdot a while back.
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).
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
When radio waves go THROUGH something easily then they're not being attenuated much inside it, which by definition means that they're not dumping their energy into it, so it's safe.
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 question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
What you describe is only one type of SS, called Frequency Hopping SS. There are various others as well, mainly Direct Sequence SS (also known as pseudo-noise, phase hopping, direct spread or direct code SS), Chirp SS which sweeps the carrier over a wide band (also known as pulse-FM, mainly used by the military), Time Hopping SS in which the time position of a pulse is controlled by a pseudo-noise code sequence, and various hybrid schemes such as DS/FH and DS/TH.
:-)
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.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
If you have a single transmitter, it will be below the noise. But the noise will be significant if the technique becomes widespread.
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 "buy this share" scheme to me...
-------
Warning: Slashdot may contain traces of nuts.
Not as much as the idea of someone other than the police using it. Can you say "Case the joint"? At least the law could use it to discover that a man, a woman, and two small children might mean that they're not at the place where they were expecting to pull a no-knock on five full grown drug dealers
I see even classic Slashdot is now pretty much unusable on dial up anymore.
My comment was
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.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
Just think, if Shockley hadn't had those other two guys getting in the way he could have started off with germanium made of silicon instead of that lousy germanium made out of germanium.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
Nope, this is a lot different. In spread spectrum, the carrier jumps around the spectrum in a previously determined pattern (so the receiver "knows" where the carrier will be next) whereas this pulse method transmits on all frequencies at once, more or less.
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
This talk about impulses and exciting all frequencies reminds me of a very similar common technique in mechanical engineering where you can easily test to find the natural frequencies of a structure.
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.
Your password has expired, please login to change it.
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).
-- Give him Head? Be a Beacon?
-- Give him Head? Be a Beacon? :P)
(If you can't figure out how to E-Mail me, Don't.
Fullerton's claim is for the notion of using extremely short pulses. You can certainly use the scheme for CDMA, but it's much more fundamental, as anyone who has designed communications systems can tell you. The impediment is that because the pulse is short, you need a very high peak power to get any kind of effective radiated power (ERP). Then, you have to stuff it through an antenna. That is the basis of his patent -- how you do that.
Radio waves propagate through concrete very nicely. The short pulse then gives you the resolution you need to see objects, fuzzily, of course. But, the system works as billed.
The problem is that the short pulse needs a large amount of power (peak power) to radiate. It's a problem for the antenna, which can only absorb so much power before it fries. The TDSI system is, however, practical for short-range, tactical communications. And, because of filter response in existing receivers, the TDSI signal does appear as a small rise in the noise floor -- not enough to detect.
Marconi's first transmitters made a pulse of RF energy by firing a spark across an air gap. The radio waves were not tuned to any one frequency, and they made short pulses of energy, hence they were broadband pulse devices. Welcome to the future..it looks a lot like the past.
0 1 - just my two bits
Everyone posting here should realize that if they talk about frequencies with regard to this broadcast technique, they are probably wrong.
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.
If tits were wings it'd be flying around.
I almost forgot to add that it would really suck if somebody just build one really huge radio tower for the entire planet and made a giant single segment Ethernet.
If tits were wings it'd be flying around.
I saw a presentation by a company called AetherWire, who were making localizers using this technology. I've only seen localizers described in Vinge's 'A Deepness in the Sky'...which is a definitely worth reading anyway.
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.
I love Mondays. On a Monday, anything is possible.
I got some mail from Aetherwire pointing to various web addresses for information on their localizers; which use the same UWB technology.
t ml
d f
_ 1/WELCOME.PDF
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.
I love Mondays. On a Monday, anything is possible.
I'd say that the company also has personnel problems, since I heard one of their employees shooting his mouth off about their plans on a flight from Dallas to Orlando yesterday.
There were a lot of IT people on that flight, from a lot of different companies in various aspects of the field.
Uh... There is no DARK side of the moon. Or at least no side that's _permanently_ dark. Since the moon rotates relative to the sun, all of it gets some light.
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.
--
The Internet is the Suppository of All Knowledge. You get it in the end.
Hmm, spreading across a large range of frequencies... Do it far enough and you ruin the few radio holes left for radio astronomy.
Doupleplus ungood.
--
The Internet is the Suppository of All Knowledge. You get it in the end.
Just make a faraday cage out of your walls. EM can't penetrate metal.
This is just what I want! Would be perfect for a highly uncentralized highspeed wireless network. Instead of IP addresses you could address them by machine id (an encrypted key) and the approximate physical location. By using a sort of binary search you could find the machine quickly anywhere in the world just by it's key. No risk of someone higher up your chain cutting you off the net, no gov't or big business control. Total Net. :)
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
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?
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.
It looks like they are bandpass filtering the output. If you notice the demonstrations were in the 100's of Mhz into the low GHz range. It also means that what they are transmitting isn't truly a pulse.
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.
Warning: Contents under pressure. Open with end pointing away from people. May injure small children and pets. Can be fatal.
Transmitting w/o waves means transmitting on all frequencies at once. This is a square wave, but when they say "not a wave" they mean *not a sine wave*. To understand a little better how this works, take a sine wave and add the sine wave of its first harmonic to it. then add the sine wave of the second harmonic to those two. Keep doing this and you start to notice your waveform getting squarer and squarer. Do it infinitely and your waveform becomes perfectly square.
Well, this isn't groundbreaking in any sense.. There's been spread spectrum for several years. Besides, you won't be able to press more information through; if you use a great bandwidth, say 100 MHz, yes, you'll be able to push around 50 Mbit/s through - at most - but only if it's continuous. If you reduce it to a pulse of, say, 1 nanosecond (10^-9), you'll get a staggering single bit per 20 seconds on average. Someone please show me the bandwidth advantage?
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.
Q: How does a Unix guru have sex? A: unzip;strip;touch;finger;mount;fsck;more;yes;umount;sleep
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!
Actually that is the stndard warning you will see in virtually every annual report from every company traded on every exchange. It is to prevent you from getting sued when your earnings don't meet estimates. Everybody does it!
I think the technology differs from radio...
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-
Yeah, I hear they just settled on a name for this new technology. Its called RADIO.
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
Bowie J. Poag
Anyone else distrubed by the thought of "hand-held radar that police can use to see inside a room before bursting in"?
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.
Maybe startup company. This sounds awesome, 10 to 40 Mb/s wireless. This will be great for wearable and portable devices, cars, etc.... The IBM guy says ``if they can'' pull it off. If they can't, someone else will license the technology from them and do it themselves.
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.
personally i don't need to block it or anything, i just need to be able to see it quickly enough to slam on the brakes, or to have it not go off for the milisecond i am in front of the cop so he either gets no reading from me or doesn't even bother to look up from his donut. :)
You can't limit the frequencies much, since then the time required for each pulse increases. To know that a frequency tone is pure (a spectrum of only one frequency), you'd have to look at it for an infinitely long time. Similarly, to have an infinitely short pulse, you'd need every possible frequency to represent it. Everything else lies somewhere in between, so if you limit the frequencies that these pulses are transmitted over, the pulses have to grow in time.
Sounds like someone is ready to IPO and wants to drive up the share price.
Mike
--
Mike
--
"Wi nøt trei a høliday in Sweden this yër?"
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
--
Mike
--
"Wi nøt trei a høliday in Sweden this yër?"
can anyone explain to me how radio energy is transmitted without radio waves, as the article claims?
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
Probably for a while. Since the primary reason to go public is to raise capital, and as the article says, they have already pulled in 20 million. Not a huge amount, but a lot more than most privately held companies.
That's not completely true. The goverment can tap into your calls at a higher level. They don't need to detect the signals coming straight out of your phone.
Here is some links:
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/
It's pretty awesome, goes into some more detail, and has some graphs/pix illustrating the differences in the technologies. Makes it a little easier to understand. USA Today kind of boiled it down as much as they could.
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.
When I was able to do my own spam-armoring, you got a chance to email me. Now you can only hope I see your reply.
What the hell is the difference between a radio energy pulse and an ordinary radio wave???
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
Synchronisation can be achieved by self-clocking codes, of course, rather than relying on a separate clock channel. This can be made error-resistant in various ways; a good example is Mark Titchener's T-codes.
http://www.ee.umd.edu/~yag/
-Anthony
I did not say at any stage that they were tapping into the signals from the phone itself, merely the system in general. Fact is, I don't know for sure at what level they do it and don't claim to know.
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?
Just like digital cellular phones (which we should have had 3 years before we did!) we won't see this tech until the world wide thought police - insert you local federal government's organisation of choice here - are issued (most likely by the manufacturers, as they usually don't have the hacking skills) with a means to invade our collective privacy in yet another way.
I just kept thinking Tricorder as I read
the article.
Everyone hates me because I'm paranoid.
This is nothing new! It sounds exactly like the technology that NASA used to send back live TV from the Moon. Only back then the name was DSSS. As a reader of NASA Tech Briefs, I know that NASA has made this technology freely available to whoever wants to develop it.
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!
Mr. Natural -- Cat Herder
What I'd like to know is what side effects this would have... given all the hubbub about cellular phones frying the brain. If it can go through walls, what else can it go through?
.oO(- thelocust -)Oo. ignorant people speak of people average people speak of events great people speak of ideas.
I perhaps have missed the point here, the information available isn't exactly the clearest in the world though, so, would anyone please be able to enlighten me as to why this technique could not be used tuned to individual frequencies instead of pulsed through the entire radio frequency spectrum? as was mentioned in a few of the earlier comments, at the moment it seems as if this is only being carried to the bounds of the most basic radio-based devices (in reference to whomsoever it was who mentioned that the first marconi morse code devices sent an EM pulse over the radio waves to no specific frequency so that an untuned reciever would pick it up)
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.
Lots of folks on this thread are missing the most general concept of this technology.
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.
light photons, if you think of how light is structured according to quantum mechanics from what I've read so far. Kind of neat when you think about it. Free air pulse packets without the need for a carrier like like.
Scientia et Potentia
Anyone else distrubed by the thought of "hand-held radar that police can use to see inside a room before bursting in"?
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
== Just my opinion(s)
Er, that was the meaning of my smiley immediately after Walsh Function ... "no, it's not pizza, it's tomato and cheese on a flour and water base." In other words, maybe the "new invention" is one of the types of SS the world has known for many years but described in a way that makes it sound different.
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.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
It's different. SS/CDMA encodes information in the phase of fixed-rate transitions of a fixed-frequency phase-locked carrier. As far as I can make out, the article is describing a type of Time Hopping SS in which information-coded pseudo noise modulates the time-domain position of a pulse, so none of the RF bits of SS/CDMA are present at all.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
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!
The Companies web site can be found at http://www.time-domain.com
Privately held.... for how long?
It's not that this tech doesn't use radio waves, it just doesn't rely on the radio waves themselves as data.
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
-AS
*Pikachu*
I'm not sure if it can be detected...
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
-AS
*Pikachu*
Hey! Weren't those telegraphs you're speaking of, that used pulses to send signals, spark gap arc telegraphs? They were incredibly dangerous, incredibly power hungry, incredibly spectrum polluting, and didn't transmit using antennas at all, if I recall correctly....
Cool. I think =)
AS
-AS
*Pikachu*
Here are couple of related patent numbers I found, doing a quick search at IBM's Patent site; search for "Time Domain" and "Fullerton; Larry W." as the Inventors & Companies, look at referenced patents:
There are a good 40 patents referencing 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!
--The more you know, the less you know.
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 the CEO of Time Domain from Upside.
Anyone else distrubed by the thought of "hand-held radar that police can use to see inside a room before bursting in"?
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.
Ultrawideband is a form of spread spectrum. The major difference between it and traditional forms of spread spectrum is that it is spread over a band which is wide relative to the center frequency (>25% of center frequency)
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
Aetherwire - makers of an ultrawideband gizmo called the locator which is both exciting and very frightening.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
I don't see how this technology allows for half of the speculation described in the article.
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
-AS
*Pikachu*
A lot of the claims made in the article are misleading or overblown. The idea of using very short pulses for data transmission is not new, and as someone has already pointed out this is merely a special case of spread spectrum encoding.
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
parallax