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Optical Cellphones
foondog writes "Here is a story over at News.com about optical cellphones. It seems that the Department of Defense has given a grant to the University of California to develop optical cellphones that are faster and more secure. This sounds a little strange to me since you would need a line of site with no obstacles in the way to use this. The article doesn't explain how this might work."
"It seams that the Department of Defense has given a grant to the University of California to develop optical cellphones that are faster and more secure. This sounds a little strange to me since you would need a line of site with no obsticals in the way to use this. The article doesn't explain how this might work."
What about from a soldier/spy/diplomat straight to a comm sat?
It's easier to get line of sight to orbit.
(sorry... had to be said)
This sounds a little strange to me since you would need a line of site with no obsticals in the way to use this.
X-rays are light energy, and they don't seem to have a problem passing through.. well.. you, among other things.
The theory of relativity doesn't work right in Arkansas.
Intersting idea, but is it really possible to have a laser based cell phone? I guess a laser would have to be used.
:)
Besides the technical problems, I really don't see much use for it. I'm happy as long as I can talk on my cell phone and I don't need: games, internet, messaging, carwash, deodorant, floss, toothpicks, swiss army knife, lunch, soft drink incorporated into my cell-phone.
I'm not that important, neither is the rest of the Slashdot crowd
If you mod me down, I *will* introduce you to my sister!
Need line of sight. DoD likes lasers. Big lasers, with lots of power. Could be dangerous.
I wouldn't want to hold one of these up to the side of my head and start talking, it might make it's own line of sight to the nearest tower.
Ouch!
A different technology in widespread use employs a method called wavelength division multiplexing, in which each cell phone uses a different wavelength of light, according to the researchers. In contrast, optical CDMA would encode each pulse, or bit of information, across a segment of wavelengths. The receiver uses a key to decode the signal and re-create the original pulse.
This sounds a lot like Ultra Wideband to me. Also, I'm guessing from reading the article that the author is confusing visible light with radio EMR.
The sell phoane comes with a set of special specticals that you put on and look at you're conversashion partner, who has an identicle set up. The phoanes then comunnicate via lazers in the specticals, thats why you have to look at each other.
(creative spelling purely intentional in homage to the original article)
What I really want is a phone with a freaking laser on it!
Someone, either the author, or a source, is totally confused about what light is.
When I read the topic, it occured to me that they might have been talking about using quantum encryption (photon spin direction? what?) with cell phones. Then I realized it wasn't the year 2025.
Anyway. This will be interesting when someone who graduated high school writes an article about it.
There are no trails. There are no trees out here.
It's not necessarily true that you need a line of sight with no obstacles in the way for an optical communications device to work. There are parts of the EM (optical) spectrum which pass through ordinary objects. Infrared, for example, can "bleed through" most walls, allowing infrared photography of the sort sometimes used by law enforcement to see behind closed doors. On the other hand, gamma rays and x-rays, which are very high frequency, are stopped by few things besides lead.
Actually, current cellphones are, in a way, optical, since they use RF. Radio waves are a kind of light of much lower frequency than the visible spectrum, and they easily leak through all kinds of solid objects. I would assume that this new research project aims at using *higher frequency* optical communications, possibly using a laser for focused rather than diffused (RF-style) transmission. Only transmitting on a direct line of sight has obvious utility for security, and that line of sight doesn't necessarily have to be onobstructed.
Anonymous Luddite: "What do you think of the dehumanizing effects of the Internet?"
Andy Grove: "Not Much."
Not an actual cell phone, but a point-to-point intercom involving binoculars and infrared transmissions. The voice was converted to (analog) IR light and transmitted through optics that created a very narrow beam. At the other end, the IR receiver was mounted in the eye piece of the binoculars and converted the light back to sound. The two devices had to be aimed very accurately at each other. That way a spy in the west could communicate with his pimp in the east across the border with very low probability of interception. They actually had this on the History Channel a few years back.
The article doesn't explain how this might work.
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Of course it doesn't
"This isn't a study in computer science, its a study in human behavior"
The grant is not to make optical cell phones. The grant is to develop CDMA (a technology used in cell phones) to be used in fiberoptic communications. The title is a bit misleading.
So, why so much money to port a technology. CDMA allows more effective use of the bandwidth and as the article points out more security than frequency division multiple access. For radio frequency stuff, CDMA is what nearly everyone uses. For radios it requires a wide bandwidth output stage. That is the kicker. The optics guys use fairly narrow band laser output stages. Then the hook them together on the same cable. They don't interfere because they are at different frequencies. To do CDMA with your whole bandwidth requires a wide bandwidth output solution (either a single broadband output or some way to put multiple lowbandwidth stages together in a better way.)
This is pretty old news.
Username taken, please choose another one.
Thus the Army must have some kind of non-broadcast communications system. I have no direct knowledge of how they would do it, but it isn't hard to imagine. For example, suppose low-flying satelites broadcast a signal. Handsets on the ground listen for that signal, and then point a highly directional antenna (LASER, focussed RF or microwave, whatever) at the satelite, and then starts transmitting a narrow beam.
There is not enough economic motive to develop this for purely commercial purposes. But once it is developed for the military, the commercial benefits are there to deploy it. Directional signalling means much less interference, and therefore much less consumption of precious spectrum, and less need for those pesky and expensive cell towers.
Crispin
----
Crispin Cowan, Ph.D.
Chief Scientist, WireX Communications, Inc.
Immunix: Security Hardened Linux Distribution
Available for purchase
From what I hear, every soldier has a mirror. On a sunny day, you can use the mirror to signal aircraft for miles.
The mirror has the advantage of not needing batteries, being resistant to shock, etc.
Of course it doesn't work in clouds or dark, and bandwidth, well... leaves something to be desired.
So if they can do this with infrared and talk through it, that seems perfectly reasonable to me. One advantage of LOS is that you have to get in the way of the thing to jam it. Of course the receiver has to be intelligent enough to ignore signals from the wrong part of town, or signals that don't carry the right code, but it's a solveable problem.
Of course, any signal, especially an IR laser, gives away your position if the enemy can see it.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
If it proves to be a gov't-use-only technology, why worry about it?
Instead of looking for specific levels of brightness, look for the delta of those levels. Or even delta^2.
Given that current satellites are able to read print the size of license plates, and we have a lot of computing power available these days, I would imagine that software could track a single point signal source and ignore others.
This is a supreme advantage of optical over other methods. We have CCDs that can see visible light and infrared, but no hi-rez CCD that can "picture" radio sources.
Jamming is only useful if all your signals come in over the same antenna. It's much, much less effective if you can easily distinguish the locations of multiple sources, then authenticate against the source you want to communicate with.
Granted, this means cell-to-satellite is easy. Not satellite-to-cell.
What's this Submit thingy do?
People are posting about "why?"
Consider the havoc that nuclear explosions play with radio frequencies.
Consider having a method of secure remote communications which does not rely on radio frequencies of any type in such a situation.
Kinda makes you stop and think about things.
"You worthless post!"
-Shakespeare, 2 Gentlemen of Verona, 1. 1. 147
I'm going to dub this the 'Laser Phone'. The Laser Phone will not be made for general public use. Laser Phones will be made for military and corporate entities that require ultra secure communications.
You maybe asking: âoeWhy would you need such a clunky method of communication? Line of site is not practical.â
The answer is very simple: Supercomputers and triangulation.
You see any voice communication has certain pitch and volume amplitude modulations. Pitch and volume amplitude modulations are part language and part human physiology. No matter how you scramble and encode the communication the human voice will always have certain keys that can be easily discerned in a conversation.
An enemy can easily grab and record a radio signal. Then the digitally recorded file can be feed in a Beowulf cluster of cheap computers. That data can within a few minutes can decode your voice and thus get your tactical information.
Another advantage of optical communication is that it is almost untraceable. Anytime you use a radio you sending out a beacon saying, "I'm right here; bomb the snot out of me!" An enemy can use simple triangulation to locate you.
A Laser Phone will be virtually impossible to intercept, track, and decode.
BTW: Anyone remembers those World War I movies where the soldiers would use mirrors to send Morse code message?
You say things that offend me and I can deal with it. Can you?
I'm busting out Beejee's when I get home for ThanksGiving. I can't wait for this!!
It's called a heliograph and a CD would make a very good substitute. ;)
Take a CD and an ice lolly stick. Make a hole in one end of the stick and hold the CD up in front of your face, shiny side facing out. Be facing the sun, more or less.
Hold the lolly stick up in front of that (about 12 inches away) and sight through the hole in the CD and the hole in the lolly stick at the aeroplane, boat, visitor craft or whatever you are trying to signal to. Now wiggle the CD until the shadow of the hole in the middle of the CD falls over the hole in the lolly stick. Now you are shining your light right at your target. By flicking your hand, you can turn the light on and off and so make morse. Or binary. Whatever.
If you do do this to a visitor, they will probably just decode the information on the CD and try to work out the meaning. Do not expect to be rescued. Expect instead to get Barry Manilow's greatest hits beamed back to you some days later.
If this saves your life, paypal me!
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