Reflections 169
RevMike writes "The New York Times (reg required) is reporting that Bell Labs/Lucent has developed a method to multiply the bandwidth of cellular networks by using multipath. Robert Lucky developed the system called Blast. He claims that it should multiply the data rates in existing spectrum 300% to 400%. One prototype took a network from 2.5Mb/s to 19.2 Mb/s. Interestingly, the system works better in cluttered environments." And on a related note, Kimberley Burchett writes "The latest Physics News Update mentions that skyscrapers could actually help wireless communication. 'The more scatterers between the transmitters and receivers, the more channels that are available. For the time being, the communication technique is limited to ultrasonic communication - the electronics necessary for exploiting scatterers with wide-band time-reversal antennas at cell phone frequencies simply don't yet exist.'"
Anyone got a Mirror (Score:1)
Re:Anyone got a Mirror (Score:5, Funny)
Re:Anyone got a Mirror (Score:1, Funny)
The state of Tech (Score:1)
At least the geek american way...
time reversal antennas? (Score:2, Interesting)
technology will *ever* exist?
Re:time reversal antennas? (Score:1)
Re:time reversal antennas? (Score:2)
HOW THIS WORKS (Score:5, Interesting)
First how is it possible to gain bandwith using 'clutter' ? here is how. imagine that you and I are both in our cars at a stop light and listening to the same rasio station. Only my radio can barely get the staion and yours does fine. If I pull my car forward a few feet, suddenly my reception improves. What happened is that the multi-path interference made my car sit in a node and your sit at a maximum.
Now if there had been more than one radio transmitter and some dude back at the station had changed the relative phase of the antennas he could have put your car in a node and my car in maximum. Thus by changing the relative phases of antenna one can direct the signal to whichever car you want. If we now differenlty modulate the signals on the antenna's we could send one signal to one car and the other signal to another car. Thus by recycling the same broadcast channel we have doubled our bandwidth.
But there is a problem here. How does the guy at the station know how to adjust the phases of the transmitters to get this spatial separation? the answer is he cant know unless he knows where both of us are and where all of the building are, and the moving cars,etc... basically impossible to compute beforehand.
So instead what you do is have the car transmit a signal on the same frequency that is coded to say 'hi i'm car #1'. The guy at the station receives this signal on his antennas and notes the relative phase of the singals on each. Now by time reversal symmetry, if he broadcast at those phases all of the multi-path signals would converge in phase on my car's antenna. Likewise he can pick out car number 2 and so on.
Furthermore i'f the clutter is changing or almost equivalently if I am driving my car, he can just keep updating the relative phases and track my car's antenna.
So the missing ingredient here is some way to detect phases and re-transmit phases in real time. One approach is to have a reference signal all of the transmitters are locked to that from which they could compute the phases they need to re-transmit. This is potentially compuationally expensive since we also have to demodulate and detect all the signals as well.
another approach is to simply phase conjugate the incoming signal, amplify it, remodulate it witht he signal, and rebroadcast it. Thus the outgoing signal is the time reversed image of the incoming signal. We never need to actually measue the phase.
there are lots of ways of 'phase conjugating' as signal but I'm not enough of a microwave jock to say how you do it in that region of the spectrum. In the optical band region there are lots of ways using non-linear optics. However none of these are wide band. They only work at specific (laser) wavelengths that can be created coherently. From the comments in the article I am assuming this is true in the microwave regime as well. When you get down to the ultra-sonic regime you get to frequencies (mega hertz) where you can do this electronically directly. So that is proably why its accoustic.
interestingly there are a number of approaches to making passive approximate phase conjugate mirrors using engineered materials (bulk element transmission lines) that do operate in the microwave regime. these however are not advanced enough for practical use yet. currenly they are finding use as light weight stealth materials aimed at radar invisibility. But probably within 5 to ten years these will be practical enough for the applications envisioned here.
I might specualte that just as the development of electronics was first spurred by military use and then by consumer use. This might happen here too.
and if some bozo complains about my typing skills I will adjust the phases of my heat ray to melt their brain.
Re:HOW THIS WORKS (Score:1)
To me, latency in cell phones is really bad, and I hope that it only gets better as technology improves. Even though more bandwidth seems like a good idea at first, we need to reduce latency before increasing bandwidth, IMO.
Re:HOW THIS WORKS (Score:2)
Re:HOW THIS WORKS (Score:3, Interesting)
BLAST doesn't require the receivers to send anything back to the transmitter.
Instead, the receivers use several antennas to create a virtual antenna with great directional sensitivity. Then the receivers use the different reflections of the signal of interest to build up a signal to receive.
This gets tricky to describe without drawing on the wall, so bear with me.
Consider a receiver with 4 antennas at different locations - for the sake of discussion say a square 1 meter on a side. We will also assume 2 transmitters at different locations. The transmitters are on the same carrier frequency, but are transmitting different signals.
For the receiver, there will exist 4 signals (one for each antenna) from each transmitter, for a total of 8 signals.
The receiver creates a set of 4 phase shift networks, and sums their output.
For each transmitter, there will exist a setting of the 4 phase shift networks that will bring all the signals from that transmitter into phase, causing them to reinforce in the summing node. Since the other transmitter will not have the same phase relationship, its signals will not tend to add up. This gives the signal of interest more level than the signal not of interest.
Now, add in some buildings, mountains, lakes, and so on, to create multipath signals. Now the number of signals from each transmitter has increased manyfold. The more signals, the more attenuation the transmitter you are trying to ignore vs. the transmitter you are trying to receive.
However, to accomplish this you need to be able to shift the phase of your network by up to tens of milliseconds, with a resolution of tens of nanoseconds. If you are moving, you have to constantly evaluate how the received signal parameters are changing, and adjust your network accordingly.
And that is why this hasn't been done for RF. For ultrasound, you are looking at needing to delay seconds, with sub-millisecond resolution.
However, when CDMA was first conceived of, the hardware to implement it would have taken several tractor-trailers to carry around. Now it fits in your back pocket.
Re:HOW THIS WORKS (Score:2)
pick out multiple phases of the signal is to have a couple of antennas, spaced at about maybe 1/4 wavelength apart or so. It's called "diversity" and radios in cars have had it since the 1940's, only it's not so popular anymore. You just pick the antenna that has the best strength or signal coded for you or whatever.
Great!!! (Score:1)
What's ultrasonic communitation? (Score:1)
What does that mean exactly?....What is it used for, what can it NOT be used for?
Re:What's ultrasonic communitation? (Score:1)
Daniel
Re:What's ultrasonic communitation? (Score:1)
Re:What's ultrasonic communitation? (Score:2)
another dissapointment (Score:5, Funny)
Re:another dissapointment (Score:1)
Re:another dissapointment (Score:1)
Not flying very far, admittedly, but still flying!
Blast? (Score:1)
Does anyone have any updated statistics on cellular safety? I wonder if this technology will affect that aspect of cellular use?
Re:Blast? (Score:5, Interesting)
Well, this one [observer.co.uk] appeared quite recently. It turns out that sparrows don't like to live near cellphone towers, and that fact is being blamed for a large reduction in the British sparrow population.
At the present time, the scientists who believe that cell phone radiation causes health effects in humans are a small minority. However, everyone agrees that cell phone use can be hazardous, for example, as a distraction while driving.
Re:Blast? (Score:1)
Cell Phones = Cancer is BULLSHIT (Score:5, Interesting)
OK, I'm a physical chemist, and this junk drives me up the wall.
All these journalists assume that the wattage is what matters, and that being 1 cm from a 4 watt transmitter could be unhealthy. However, the wattage is irrelevant - Einstein showed this with the photoelectric effect. Basically, it is the frequency of the radiation that is dangerous, not the wattage, because one photon interacts with one electron - so the number of photons is irrelevant. For example, which would you rather be near - a 100W light bulb, or a 1W gamma ray emitter? Thought so...;)
To give you a baseline, cancer due to radiation occurs because photons of succicient energy actually break chemical bonds in your DNA. This requires low-UV or better to accomplish. That's why sunburn gives you cancer. Now, compare this to radio waves, which are far, FAR to low in energy to accomplish anything of the sort. In fact, radio waves are even to low to excite the vibrational or rotational states of a molecule (which is how a microwave oven works), so there is no risk of "cooking" your brain, either.
Ultimately, when pressed, these cell-phone-cancer freaks point at two cases where some habitual cell-phone user got cancer on the right side of his brain. Ergo, it was the cell phone. These "doctors" (and I use the term loosely) have never proposed any sort of mechanism or ANYTHING to explain how it could occur. Because it can't.
Bottom line, you have a better chance of getting cancer from your own body heat (you emit infrared radiation) than you do from a cell phone.
Re:Cell Phones = Cancer is BULLSHIT (Score:1)
Then please refrain from using "Wattage" when you mean "Power".
Re:Cell Phones = Cancer is BULLSHIT (Score:1)
Re:Cell Phones = Cancer is BULLSHIT (Score:1)
Then why not say "power" here? Why use "power" for a journal and "Wattage" for
Re:Cell Phones = Cancer is BULLSHIT (Score:2)
I don't have the studies, but measurable physiological changes in organisms exposed to EMP's of the type emitted by nuclear weapons have been found. That right there disproves your hypothesis that the energy level is irrelevant
There is also evidence that cellular divsion and the DNA replication process functions using the earth's magnetic field as a baseline guide. This is one of the reasons cancer can occur. Remember, cancer is very rarely due to atomic decay (from gamma waves as you mention), it occurs primarily due to an error in the DNA replication process.
There are of course many animals whose very existence depends upon the continued stability of the earth's magnetic field. Many birds "see" the earths electromagnetic field. Most simple sea floor organisms used a biological compass for directional movement. Many single celled organisms have similar abilities.
Cancer can be caused by many factors, not just atomic level degredation due to radioactive decay. Right now it is not known exactly what high levels of electromagnetic radiation does to humans, but it DOES do something. The simple fact that animals are sensitive to this kind of energy indicates caution is warranted. You are certainly free to bath yourself in whatever radiation you desire, but I prefer to avoid it.
We can argue all day, and we can both disagree. Just don't shove your theory down my throat and I won't shove mine down yours. That means insulating wires and devices and minimizing high energy cell phones and putting sufficient shielding in devices.
A few corrections... (Score:2)
The way in which the damage is done is dependent on frequency. UV and gamma/X-ray radiation is high enough in energy that it can directly cause severe damage to molecules (such as our DNA) - This is why it causes cancer, even if relatively little of it is absorbed by the body.
Visible light doesn't do much damage because very little gets absorbed by the body - Most gets reflected.
RF can be VERY dangerous because unlike visible light, it can penetrate the body. In some cases (HF most likely up to VHF) it goes right through without interacting. At the UHF/microwave regions, this changes - Significant percentages start getting absorbed by the body. 2.4 GHz is particularly nasty because of a molecular resonance with H20 - Water absorbs around here readily, which is why it's not primarily a communications band and why microwave ovens operate at 2.4 GHz.
That said - Cell phones aren't dangerous, because they only emit 200 milliwatts (digital) and 600 milliwatts (analog) - That's not enough to cause significant heating. You won't feel it, you won't notice it, your body generates and dissipates far more heat on its own. Furthermore, the high-power analog mode only occurs in the 900 MHz band, never in the PCS band where absorption is higher.
Also, if someone were to be injured by excess RF, it wouldn't be cancer. Cancer modifies DNA, RF merely heats up cells to the point where they die.
Re:A few corrections... (Score:2)
Which is why there is no problem; last I checked cell phones don't operate in the microwave. (800 MHz I believe) Also, I was specific - microwaves are not radio waves, and I never claimed being near microwaves was safe.
As for power being irrelevant, it is when we're talking about radiation that is about 6 orders of magnitude too low in frequency to cause any sort of dangerous electronic transitions (UV is about 1,000,000 THz). The dependence is exponential - so if something is possible but improbable for UV, it is absolutely impossible for radio waves.
Bottom line, unless you have an exceptionally liberal definition of "radio," they won't be causing any damage.
Re:A few corrections... (Score:2)
It is simply incorrect to say that radio-frequency (RF) signals are incapable of causing damage irrespective of power. Your analysis is deeply flawed and ignores a wealth of literature that shows the effects of strong electromagnetic fields on humans and animals.
It is correct that what we're discussing here is nonionizing radiation. It is not correct that the deleterious effect of RF is related solely to the particle energy. Another significant factor is the degree to which the signal is absorbed by the human body. The human body is not transparent to RF; neither is it a conductor. It absorbs energy from an RF field, energy that is converted into heat. When the energy is sufficiently high, this heat can damage cells. This is particularly true in some areas of the body such as the eyes. And the body does not absorb energy at all frequencies equally. In fact, the FCC RF exposure regulations allow less power density at 30-300 MHz than they do at frequencies above that. (And, yes, power does matter, very much.) That's because the specific absorption rate (SAR) of the human body peaks at approximately 100 MHz.
Some useful background can be found on the FCC's RF Safety [fcc.gov] page.
Re:A few corrections... (Score:2)
What you actually wrote was: "As for power being irrelevant, it is when we're talking about radiation that is about 6 orders of magnitude too low in frequency..."
As for "deeply flawed," the photoelectric effect is fairly clear - for two sources of the same power, the one with the higher frequency is the one with the greater ability to effect electron transitions (ie, breaking bonds in DNA).
But that's simply not the issue for nonionizing radiation, which is the flaw in your analysis.
I repeat: At these frequencies the principal known deleterious effect is heating and is a strong function of power. Your statement that power is irrelevant is simply incorrect. Now, if what you meant was to limit that to cell-phone levels, fine. But that's not what you said. Claiming ex post facto that it should be obvious is weak.
And, by the way, if you're not able to hear objective criticism of your statements without taking it personally, maybe you would be better served not to make them.
This is silly... (Score:2)
Btw, where does "non-ionizing" radiation officially start? Because even near-uv can cause damage to DNA...just wondering.
Now, if what you meant was to limit that to cell-phone levels, fine. But that's not what you said. Claiming ex post facto that it should be obvious is weak.
Since this was a post *about* cell phones, I think that's a reasonable assumption. I mean, any statement can be proven false if extended to ridiculous or out-of-context conclusions. I mean, did you call your classical physics teacher an idiot because Newton's laws were proven "wrong" by Einstein? Similarly, I would maintain that extending discussions of megawatt (or even kilowatt) transmitters to a discussion of cell phones certainly meets that standard.
And, by the way, if you're not able to hear objective criticism of your statements without taking it personally, maybe you would be better served not to make them.
I can take criticism, and I can return it. And if you criticize, you should expect your rebuttals held to a higher standard than that which you're criticizing. What I find annoying is nitpicking at posts where someone failed to state the obvious, when all parties realize what was implied. Or did you honestly think I was speaking of universal truths regarding the deletrious effects of radiative power?
Re:This is silly... (Score:2)
You certainly appeared to think you were. And it wouldn't be the silliest thing ever posted on /. (Now, there's a competition!) At best your terminology was imprecise and subject to misinterpretation. Clearly, though, you're not interested in hearing that. Your loss.
Umm... (Score:2)
Most people define the beginning of the "microwave" region as somewhere between 1 GHz and 2 GHz. This doesn't mean that they are no longer radio waves.
Microwave ovens operate at 2.4 GHz. (Note: This is the main reason that 2.4 GHz is an unlicensed band, which is where 802.11b/g hardware operates, as do 2.4 GHz cordless phones.)
The band allocation for UMTS (3G GSM cellular) is approximately 2110-2170 MHz. (2.11-2.17 GHz). This is only 10% lower in frequency than microwave ovens. The PCS band, which is where MANY cell phones operate, is 1.9 GHz. And even 900 MHz is absorbed by the body reasonably well. Not quite as well as at 2.4 GHz, but still enough that I would not want to be closer than a foot to any transmitter over 20 watts.
The reason cell phones aren't dangerous has nothing to do with frequency - And has everything to do with their power. Analog phones (except for portable/car units) are 600 mW, digital CDMA is 200 mW.
Note: 200 mW of UV/gamma/X-ray CAN be dangerous, since instead of general heating, it essentially causes "bit flipping" in your DNA. 99.999999% of the time, that flipped "bit" does nothing or kills the cell, but every once in a while the right part of the DNA is corrupted and the cell becomes cancerous.
Also, the field strengh is more critical than the total power. Being in front of a directional antenna is far worse than being near an omni, and the inverse square law is your friend. But even 5 watts at 144 MHz can give you an RF burn if you get too close to the antenna. (At that power level, it's basically physical contact, but even a thin insulator won't help you, unlike with DC or low-frequency AC.)
Re:Umm... (Score:2)
The reason cell phones aren't dangerous has nothing to do with frequency - And has everything to do with their power. Analog phones (except for portable/car units) are 600 mW, digital CDMA is 200 mW.
Note: 200 mW of UV/gamma/X-ray CAN be dangerous, since instead of general heating, it essentially causes "bit flipping" in your DNA. 99.999999% of the time, that flipped "bit" does nothing or kills the cell, but every once in a while the right part of the DNA is corrupted and the cell becomes cancerous.
Two consecutive and contradictory paragraphs. You just pointed out that the same power of two different frequencies can be potentially fatal in one circumstance, and innocuous in the other. That was THE POINT. Ask yourself, why can radio waves not cause any bit flipping? Because their frequencies are insufficient to effect an electronic transition.
Also, as far as which is more important, I still go with frequency. Double the frequency, and you will get about an 8-fold increase in the damage to chemical bonds (actually e^2, because of the exponential dependence). Double the power, and you get double the heat production. Again, this is the photoelectric effect - look it up if you've never heard of it, Einstein won the Nobel Prize for it.
I don't wand to belabor the point, but microwave absorption spectra are VERY SPECIFIC. No, 2170 is NOT close enough to 2400 GHz to cause significant excitation of the water rotational mode. A 10% difference is more than enough. If you are in doubt, I could recommend some good chemistry books, or you can find your own water microwave spectrum. This is exactly why the FCC forbids communications at this narrow band.
Ultimately, the only arguements for damage from sub-microwave radio is if you stand in front of a high-power transmitter. Well, duh. But when we are talking about something with LESS THAN A WATT of transmitting power, the only way for it to be dangerous is if it is at LEAST uv. Period. Otherwise, the only possible danger is from heat. With higher frequencies, you won't have enough power to generate heat, but you will cause tissue damage nonetheless. Hence, sunburn.
Re:Cell Phones = Cancer is BULLSHIT (Score:2)
I'm sure you're a good physical chemist, but if neurooncologists and biophysicists haven't pinned down everything that causes brain cancer, can you really say that you can?
To give you a baseline, cancer due to radiation occurs because photons of succicient energy actually break chemical bonds in your DNA.
That's one of the causes. There could be others. For example, this article [com.com] states that:
Just because the radiation produced by cell phones is itself not powerful enough to directly affect the DNA doesn't mean that it will thusly have no effect whatsoever.
Re:Cell Phones = Cancer is BULLSHIT (Score:2)
From the article: Dr. French emphasised that no link has yet been shown between the specific biological effects of mobile phone radiation and cancer, but that there was now a theoretical framework for such an effect that could be investigated.
So we have a guy theorizing that this could in fact be the case, without any real link, just a leap of faith. The research is nearly 2 years old. ANy follow up?
Re:Cell Phones = Cancer is BULLSHIT (Score:2)
I was simply pointing out that the blanket attack against ANY insinuation that they do probably isn't a good idea. Science I don't agree with does not necessarily equal junk science.
Cell phone wavelengths ARE in microwave oven range (Score:2)
Bzzzt. Cellphones typically operate in one of several bands, including 0.8 GHz, 0.9 GHz, 1.8 GHz and 1.9 GHz. The latter two are not "far, far to low" -- microwave ovens operate at 2.45 GHz. They are well within the same octave (10x or 2x, take your pick :)
Sure, FM radio and TV are well below the microwave range, but we're not all holding VHF transmitters to our heads.
I'm not saying that ionizing radiation or heating radiation is what causes the complaints we've all heard of (headaches, loss of focus, etc.). But the frequencies ARE approaching the range of microwae ovens, and I think we WILL eventually find a provable scientific evidence of harm via cellphone radiation.
Re:Cell phone wavelengths ARE in microwave oven ra (Score:2)
Sorry. There are two possible phenomena at work here. First is the possible damage to DNA from radiation. This is impossible, as mentioned. Second is possible heating by absorption of microwave radiation (I assume you mean water). These frequencies at which water does so are actually quite narrow, and a 1.9 GHz cell phone will not be absorbed much at all by water. Otherwise, your cell phone reception would go to shit on a humid day. I could send you a microwave absorption spectrum of water, and show you that it doesn't happen at 1.9.
Re:Cell Phones = Cancer is BULLSHIT (Score:2)
The problem of course is that the common man is so stupid as to need many, many more of that kind of answer before even coming up for consideration as just baseline intelligent, but at least it's a start
Re:Cell Phones = Cancer is BULLSHIT (Score:2)
I know there are no studies showing a link, and a good body of work discussing this (references [mcw.edu]), but I think I'll wait another 10 years before I really believe it. There hasn't been enough long-term study yet to suit me (and if we're throwing out creds, I'm a physicist so I understand most of what I read in these journal articles)
Re:Cell Phones = Cancer is BULLSHIT (Score:2)
Just Effing Great (Score:5, Funny)
Now it going to be people wanking off to their live-feed pr0n delived to their cellular in the movie theater.
Lovely....
Re:Just Effing Great (Score:3, Funny)
Just curious if I'm missing some new technique or something...
Robert Lucky developed the system called Blast. (Score:3, Funny)
Who would've thought? (Score:5, Funny)
I never would have imagined that a tall, slender, permanent, cellphone tower-like structure could serve as a cellphone tower.
Hmmm... (Score:5, Funny)
Re:Hmmm... (Score:1)
well... less of your bedroom (since I haven't seen it in days - why won't you return my calls?) - but more of my office desk and laundry basket at home.
if one more person tells me that a cluttered desk means a cluttered mind, I'm gonna kick their teeth in and then piss myself.
like last thursday.
Wi-Fi to become Hi-fi !! (Score:1)
And this will affect me when... (Score:1)
If my calculations are correct... (Score:5, Funny)
Perhaps if someone would fall and hit their head on the toilet, then they would come up with the means for time-reversal. Tell me future boy, why do we need screen savers on our mobile phone LCD screens?
Re:If my calculations are correct... (Score:2)
Unfortunately, no. It requires something with a little more kick . . . plutonium!
Re:If my calculations are correct... (Score:2)
No Reg. Required (Score:5, Informative)
By IAN AUSTEN
IT is a phenomenon well known to people who drive through urban high-rise canyons. Just as you stop at a traffic light, the car radio loses its signal. Once the light turns green, the car only has to creep forward a few feet to restore the radio reception.
Those dead spots, which can also cut off cellphone calls and mobile computer communications, are often caused when signals bounce wildly off the surrounding buildings. This scattering creates pockets in which two reflections of the same signal collide and cancel each other out.
Avoiding the undesirable effects of multipath, as this scattering effect is formally known, has long been a preoccupation of people who design wireless communications systems. Now, however, a system developed by Bell Labs actually embraces radio reflections not only to improve reception but also to boost the speed of wireless networks. Prototypes of the system, called Blast, can send data over third-generation, or 3G, cellphone networks at rates about eight times those of 3G.
"Normally multipath is the source of confusion, it's the enemy," said Robert W. Lucky, who recently retired as vice president for applied research at Telcordia Technologies and is familiar with the Bell Labs work. "Here you put the confusion back together Humpty Dumpty style. It's like getting something for nothing."
Gerard J. Foschini, a 40-year veteran of Bell Labs, came up with the theory behind Blast about a decade ago while working on a long-term project to find the limits of a wide variety of technologies. As part of that project, he reviewed the work of Claude Shannon, the Bell Labs mathematician who published a paper in 1948 that established the field of modern information theory. Dr. Shannon's work still provides the basis for much information theory, including the notion of system capacity limits.
"He found the ultimate limits," Dr. Foschini said. "But he was basically dealing with one transmitter and one receiver. It was obvious to us that we could deal with many transmitting antennas and many receiving antennas for the same transmission."
So Dr. Foschini began developing mathematical models to see whether sending data through arrays of antennas would expand network capacities.
Antenna arrays have long been used in radar systems. But Dr. Foschini said that radar arrays are used to focus radio beams, whereas he wanted to scatter them. He hoped to discover whether wireless capacity could be boosted by dividing up data in space as well as time. Rather than point-to-point communications, his plan was to create volume-to-volume exchanges.
He had found through mathematical research that the concept would not work if the transmitter had only a single antenna. "If you send the same signal from one antenna many times all radiating in the same band, you come out statistically right where you started," Dr. Foschini said.
Instead, he developed a system that divided data into multiple streams that were then transmitted on the same frequency by several antennas. At the receiving end, the different streams of data were picked up by other antenna arrays.
Normally more than one transmission on a single radio frequency produces nothing but electronic noise. But Blast can make sense out of the noise because of the physical separation of the antennas sending the messages. Processing software reassembles the scattered data streams into their original form.
When Dr. Foschini tested the plan mathematically, the results were surprising. "We found the capacities were enormous - far, far in excess of what people were thinking of,'' he said. "If you put more and more antennas at the transmitting end, the capacity kept increasing. We were coming out with such ridiculously large capacities that at first, we didn't believe it."
Prototype systems proved that the experiments were correct. Each additional antenna added another element of space and because of that, additional capacity.
Just as surprising was the finding that the reflections that plague current wireless systems actually expanded the capacity of Dr. Foshini's system by effectively introducing more points in space. "Heavy scattering, which I always thought was a bad thing, is with this a good thing," he said. In fact, he anticipates that Blast-based wireless systems will work more effectively in Manhattan rather than "somewhere where it's flat as far as the eye can see."
Bell Labs has made prototype chips that would allow Blast to operate at speeds of 19.2 megabits per second over a 3G wireless network. Currently the highest speed those networks can offer is 2.5 megabits per second. Ran Yan, vice president for wireless research at Bell Labs, said that the prototype chips were intended for use in a cellphone or wireless hand-held computer.
Dr. Foschini declined to estimate the ultimate transmission speeds that could be achieved with Blast. One restraint on speed is the intense data processing it requires. With current technology, higher speeds would demand chips that are too large and too power-hungry for hand-held devices.
Dr. Yan said that the first systems offered by Lucent Technologies, the lab's parent company, would probably use just four transmitting antennas. Because wireless data systems operate with high frequencies and the transmitting antennas must be separated by only half a wavelength, he said, it will not be hard to squeeze more antennas into even the most compact mobile phones or palmtop organizers.
Because of economic problems, the wireless industry has been slow to adopt even 3G networks in the United States. So Blast is unlikely to become available soon. But unlike 3G, Blast does not require the construction of new networks. It only needs relatively inexpensive equipment, like new base stations, to be installed on current systems.
"It's a minimal upgrade," Dr. Yan said. "But it will allow service providers to get 300 to 400 percent increases in data rates in first deployments, and much higher quality."
While Lucent is already making network base stations for wireless service providers that can be converted to use Blast, Dr. Lucky anticipates that those companies will wait for the military to pioneer use of the system. He said there were concerns that the complexity of Blast might create unforeseen problems when used by large numbers of people on congested networks.
Assuming that problems do not develop there, however, Dr. Lucky said, the system could completely alter all systems that depend on radio waves. "I had this idea that spectrum was all used up,'' he said. "Now, with new technologies like Blast, maybe spectrum is infinite."
Re:No Reg. Required (Score:2)
There's fair use and then there's copyright infringement. Give it a rest. The NY Times has plenty of bandwidth, so it's not like you're mirroring due to the a potential Slashdotting. You are just blatantly stealing content.
Re:No Reg. Required (Score:2)
I really don't blame you for AC'ing that comment.
Ultasonic? (Score:1)
Similar work at BYU (Score:2, Informative)
Re:Similar work at BYU (Score:1, Funny)
There is a joke about polygamy lying in this statement.
Sorry, had to be said
Isn't this just some... (Score:1)
or is it some kind of compression scheme where you take the signal transfer and match it to the closest matched wave possible and simply send over an encoding of it instead.
though in other notes.. isn't the best way to boost speed.. just to put more power into it?
Re:Isn't this just some... (Score:1)
Re:Isn't this just some... (Score:1)
dubious (Score:1)
Bollocks. I'd bet money Buck Rodgers has one.
And Shatner.
Not Lucky, Forchini (Score:3, Informative)
Re:Not Lucky, Forchini (Score:1)
Re:Not Lucky, Forchini (Score:2)
--zawada
PS, For those who aren't aware, Bob Lucky started his career at Bell Labs way before the big breakup of AT&T. When AT&T was broken up, a bunch of Bell Labs people (including Lucky) moved over to the newly-created Bellcore to support the RBOCs... When the RBOCs sold Bellcore to SAIC, Bellcore's name was changed to Telecordia so that "Bell" would no longer be a part of it.
Re: Old Guys from Bell Labs (Score:2)
All these 25-year-old dot-com kids who are worried that they're too old to be CEOs should know the world was different once.... the article described Forschini as a 40-year veteran of the Labs, and it's unlikely to have been a typo for "40-year-old".
Or you could use existing technology (Score:1)
But the electronics don't exist and it might be years away and it does not work yet with celluar frequencies and it might just be easier cheaper and all around make more sense to just use existing technology but pump up the number/amount of frequencies.
Now that is news and it matters!
Customary Joke (Score:3, Funny)
It took the physics guys this long to figure out that a beowulf cluster of skyscrappers works better ?
Ducks...;)
Actually a good point.... (Score:2)
It took the physics guys this long to figure out that a beowulf cluster of skyscrappers works better ?
What's cool is that taking a signal of a given bandwidth, splitting it, bouncing it, and recombining it is actually better. It's a bit like saying that a Beowulf cluster made of 3 1GHz PIV's would beat the crap out of a single 3GHz PIV system - which should not happen. Crazy!
Time-Reversal? (Score:1)
I dont quite follow... is this saying its now possible to travel back in time using a cell phone?
Yet Another Variant (Score:1)
Yet Another Variant of the old "Get DSL/Cable performance out of your old 14.4k modem" story? Sorry, but "plus 400% data rate" stinks. Show it in the field with a few thousand parallel users and I'll believe it.
mixed blessing? (Score:1, Interesting)
But I'm a little skittish about jumping into this hole, hog. We still haven't seen any unbiased studies on the effects of cellular phones on the brain (where people hold their phones while talking) and the reproductive organs (where they keep them when they're not).
I don't know if we want to double, treble, or quadruple their radiation emissions before we know what the effects on living tissue will be. What government department does this sort of thing fall under? The FCC? If there isn't one, then one should be created. Just my two cents.
Re:mixed blessing? (Score:1)
Not sure about you, but I keep my cellphone in a holster on my hip.
It balances out the HandEra PDA and the LeatherMan, not to mention the Bat Shark Repellent.
Re:mixed blessing? (Score:2)
I am going to call you on this. Where is a biased study? How was it flawed and how would you have done it differently?
Personally, I believe that if there are any hazards to humans from cell phone RF emissions, they are very slight, otherwise it would be easy to find them conclusively in a well-designed study.
And, if, perchance, you can't back up what you are saying, then please stop saying it.
MM
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Lucent announced it last October (Score:5, Informative)
Chips developed by Bell Labs will enable mobile devices to receive more than 19 megabits of data per second on 3G networks
Bell Labs demoes 19.2Mbps 3G chips [theregister.co.uk]
By John Leyden
Posted: 18/10/2002 at 13:28 GMT
Re:Lucent announced it last October (Score:1)
Cool? Yes, but when? (Score:2)
There's the bullet: "...Simply don't yet exist"
At least as it is, the plan doesn't call for more clutter. Most cities are ugly enough as they are.
Official North Korea Website Site Still Sucks, and Uses Macromedia Fireworks 3.0 [xnewswire.com]
John Lee Hooker..... (Score:2)
So it wont work for CDMA (Score:1)
Does this also mean I'll never get broadband on cellphones unless we use a different frequency
Re:So it wont work for CDMA (Score:1)
My reading is that information theory maximums are based on single transmitter/single receiver models. This model is a multiple transmitter/multiple receiver system where the signal is post-processed from a cacophony of noise into multiple discrete streams of data.
Just making a guess, a system of four transmitters and four recievers should be able to carry four times the data in the same band. The multi-path of the signals from any particular antenna will probably cause destructive interference on one receiving antenna, noise on two antenna, and constructive interference on one antenna.
The hard part is that it is impossible to predict which antenna has the constructive interference at any time. The data has to be assembled after the fact.
Re:So it wont work for CDMA (Score:2)
I can't be bothered to decipher these fluff articles, but it looks like these guys have merely added a phased-array antenna to the conventional CDMA approach. It is neat, but once you have the concept of making multipath work for you, it isn't much of a leap.
Re:So it wont work for CDMA (Score:2)
This isn't exactly scalable. (Score:2, Interesting)
Re:This isn't exactly scalable. Retraction. (Score:1)
The technology does exist (Score:1)
And you wanted to know WHY we need faster chips? (Score:2, Interesting)
So is this the next killer app to fund chip research?
Handheld vs. Laptop bandwidth needs (Score:2)
It's possible that the "hand-held devices" that this technology is too large for are the laptops, not the phones, in which case, yes, we'd like some new chips please :-) Maybe the old MicroUnity [microunity.com] project could be finished... By the way, if you're going to do phased-array things with antennas, might as well have fun doing them with microphones and speakers and skip the headset entirely. One of the Microunity folks was playing with this a few years ago; you could do really impressive things if you had the signal-processing horsepower available, which their chip, had it ever become what they wanted, would have done; maybe current DSPs can provide enough horsepower today.
Wow, maybe then can do this with ATSC broadcasts! (Score:1)
Text of NYTimes article (Score:1)
By IAN AUSTEN
T is a phenomenon well known to people who drive through urban high-rise canyons. Just as you stop at a traffic light, the car radio loses its signal. Once the light turns green, the car only has to creep forward a few feet to restore the radio reception.
Those dead spots, which can also cut off cellphone calls and mobile computer communications, are often caused when signals bounce wildly off the surrounding buildings. This scattering creates pockets in which two reflections of the same signal collide and cancel each other out.
Avoiding the undesirable effects of multipath, as this scattering effect is formally known, has long been a preoccupation of people who design wireless communications systems. Now, however, a system developed by Bell Labs actually embraces radio reflections not only to improve reception but also to boost the speed of wireless networks. Prototypes of the system, called Blast, can send data over third-generation, or 3G, cellphone networks at rates about eight times those of 3G.
"Normally multipath is the source of confusion, it's the enemy," said Robert W. Lucky, who recently retired as vice president for applied research at Telcordia Technologies and is familiar with the Bell Labs work. "Here you put the confusion back together Humpty Dumpty style. It's like getting something for nothing."
Gerard J. Foschini, a 40-year veteran of Bell Labs, came up with the theory behind Blast about a decade ago while working on a long-term project to find the limits of a wide variety of technologies. As part of that project, he reviewed the work of Claude Shannon, the Bell Labs mathematician who published a paper in 1948 that established the field of modern information theory. Dr. Shannon's work still provides the basis for much information theory, including the notion of system capacity limits.
"He found the ultimate limits," Dr. Foschini said. "But he was basically dealing with one transmitter and one receiver. It was obvious to us that we could deal with many transmitting antennas and many receiving antennas for the same transmission."
So Dr. Foschini began developing mathematical models to see whether sending data through arrays of antennas would expand network capacities.
Antenna arrays have long been used in radar systems. But Dr. Foschini said that radar arrays are used to focus radio beams, whereas he wanted to scatter them. He hoped to discover whether wireless capacity could be boosted by dividing up data in space as well as time. Rather than point-to-point communications, his plan was to create volume-to-volume exchanges.
He had found through mathematical research that the concept would not work if the transmitter had only a single antenna. "If you send the same signal from one antenna many times all radiating in the same band, you come out statistically right where you started," Dr. Foschini said.
Instead, he developed a system that divided data into multiple streams that were then transmitted on the same frequency by several antennas. At the receiving end, the different streams of data were picked up by other antenna arrays.
Normally more than one transmission on a single radio frequency produces nothing but electronic noise. But Blast can make sense out of the noise because of the physical separation of the antennas sending the messages. Processing software reassembles the scattered data streams into their original form.
When Dr. Foschini tested the plan mathematically, the results were surprising. "We found the capacities were enormous - far, far in excess of what people were thinking of,'' he said. "If you put more and more antennas at the transmitting end, the capacity kept increasing. We were coming out with such ridiculously large capacities that at first, we didn't believe it."
Prototype systems proved that the experiments were correct. Each additional antenna added another element of space and because of that, additional capacity.
Just as surprising was the finding that the reflections that plague current wireless systems actually expanded the capacity of Dr. Foshini's system by effectively introducing more points in space. "Heavy scattering, which I always thought was a bad thing, is with this a good thing," he said. In fact, he anticipates that Blast-based wireless systems will work more effectively in Manhattan rather than "somewhere where it's flat as far as the eye can see."
Bell Labs has made prototype chips that would allow Blast to operate at speeds of 19.2 megabits per second over a 3G wireless network. Currently the highest speed those networks can offer is 2.5 megabits per second. Ran Yan, vice president for wireless research at Bell Labs, said that the prototype chips were intended for use in a cellphone or wireless hand-held computer.
Dr. Foschini declined to estimate the ultimate transmission speeds that could be achieved with Blast. One restraint on speed is the intense data processing it requires. With current technology, higher speeds would demand chips that are too large and too power-hungry for hand-held devices.
Dr. Yan said that the first systems offered by Lucent Technologies, the lab's parent company, would probably use just four transmitting antennas. Because wireless data systems operate with high frequencies and the transmitting antennas must be separated by only half a wavelength, he said, it will not be hard to squeeze more antennas into even the most compact mobile phones or palmtop organizers.
Because of economic problems, the wireless industry has been slow to adopt even 3G networks in the United States. So Blast is unlikely to become available soon. But unlike 3G, Blast does not require the construction of new networks. It only needs relatively inexpensive equipment, like new base stations, to be installed on current systems.
"It's a minimal upgrade," Dr. Yan said. "But it will allow service providers to get 300 to 400 percent increases in data rates in first deployments, and much higher quality."
While Lucent is already making network base stations for wireless service providers that can be converted to use Blast, Dr. Lucky anticipates that those companies will wait for the military to pioneer use of the system. He said there were concerns that the complexity of Blast might create unforeseen problems when used by large numbers of people on congested networks.
Assuming that problems do not develop there, however, Dr. Lucky said, the system could completely alter all systems that depend on radio waves. "I had this idea that spectrum was all used up,'' he said. "Now, with new technologies like Blast, maybe spectrum is infinite."
Bell Labs started talking about this... (Score:1)
Screw all this (Score:1)
what is the underlying physics? (Score:1)
One point that came out in the article was that the signal was being transmitted from an array of antenas and received by an array of antennas. This says to me, that they're using the phase shift of the signal somehow to increase the bandwidth, but if the transmitter array is only a half-wavelength in extent then the phase shift in time is only on an order of 1ns. (I'm assuming the wavelength is comparable to the size of a cell phone
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I hate sigs.
Dr. Lucky, I presume? (Score:1)
Obviously... (Score:2)
I wonder how many lines of code and how much time this job took?
Robert Lucky and old news (Score:3, Interesting)
Robert Lucky was at Telcordia, not Bell Labs. The New Yorks Times articles notes this. So, editors, please do a vague glance in the general direction of the article and the article summary before posting..
Second, this is old news. Here is a general scientific article on the underlying basis for the technology from September 2001:
http://www.aip.org/pt/vol-54/iss-9/p38.html
Kevin
Isn't this just multiuser detection? (Score:2)
Re:Robert Lucky developed the system called Blast. (Score:1)