The Myth of Radio Spectrum Interference 603
Selanit writes "Just came across a fascinating article on Salon about a technologist who claims that there is no such thing as "interference" in the radio spectrum. He argues that interference is a symptom of inadequate equipment, not a fact of nature, and that with improved transceivers we could open the spectrum up to high-quality broadcasts by anyone. Reference is made to the GNU Radio Project. Neat stuff." We've posted other stories about this. I wonder if the "color" meme will catch on.
Not going to happen (Score:4, Insightful)
Based on the power that Television companies hold, does anybody really think this is going to happen? We have a hard enough time with the record labels, now they want to go up against people like NBC?
Great idea. Unfortunatly, it would never happen without serious reform within the Gov itself.
Not that I don't like making waves, but one step at a time.
Just my humble opinion,
SirLantos
complete bunk (Score:4, Insightful)
Partially..... (Score:4, Insightful)
Too optimistic, in my view (Score:4, Insightful)
Radio's basic signal function defined in software? Sure, "Maximize your bandwidth with our new RadioBooster!!!" (at the cost of your neighbors).
While this guy might have a point - the current FCC policies on RF spectrum might be a bit outdated, I would be careful with deregulation here.
This has been a known fact for a long time... (Score:4, Insightful)
Well made and tuned equipment can eliminate any chance of interference and allow for more radio stations within an area. However, organizations like NAB (www.nab,org) and now, the FCC stonewall any attempts to open up the airwaves. At one time, there was a proposal to allow low power broadcasters to operate, unlicensed, if they could prove they weren't interferring and accept the interference from other channels. It was approved but still puts the "little guy" at a disadvantage: http://www.fcc.gov/mb/audio/lpfm/.
If there ever was an "ol' boy network", it's broadcasting. If you want to broadcast legally, you're looking at dropping half a million in legal and license fees alone before you buy your first piece of equipment.
Re:Limited Quantities (Score:2, Insightful)
Uncertainty Principle (Score:2, Insightful)
If i wasnt so sleep deprived, i could give some approximations with numbers and stuff.
interesting, but a bit arrogant (Score:3, Insightful)
As my chemistry teacher once said to me, 'A poor craftsman blames his tools'
Reed is wrong (Score:5, Insightful)
For a variation on this theme, there's an interesting moment in a movie (Frankie and Johnnie?) where there's a terrific racket in a diner, impossible to understand anything, but a cook and a clerk are communicating easily --- by sign language. Consider also those occasional TV images of the Wall Street pit traders flinging gang signs at each other
Spectral purity and antenna quality limitations can be overcome --- by money. You can build higher quality receivers and transmitters, bigger antenna installations but it costs money and space in fairly unavoidable ways.
Reed is also wrong from a regulatory level. It's not just the FCC that you'd have to work with, but the ITU. Those pesky radio waves have this interesting habit of leaking over borders on the ground, and pretty much everywhere down here from satellites.
There are pretty good reasons to pick on modern broadcasting: crappy content, media concentration --- but "broadcasting" is not one of them. Those great big transmitters permit the use of very dumb receivers with poor sensitivy. The very simplicity and asymmetry of broadcast provides tremendous economic and technical appeal, and I'd be amazed if it ever went away.
Far more interesting is the glacial progress of DTV in broadcast.
Color Wheel (Score:4, Insightful)
Back to the color thing:
Ever had a color wheel, a circle with pie shapped sections in various colors. You spin it and it all looks white. The higher the data rate at any frequency the more the signal is spread out over adjacent frequencies, so rather than being just green or blue it all looks white. Engineers call a signal with equal power across the whole spectrum "white noise". Usefull signals disappear into noise.
Baloney (Score:2, Insightful)
Re:complete bunk (Score:3, Insightful)
He's right (Score:5, Insightful)
While this is *techniclly* correct, On could also say that A knife could be built that can cut a loaf of bread into infinite pieces, if we could design it to cut sub-elementary particles. Why are we not making knives that can do this? Because the technology isn't there, and if it was it would probably be cost prohibitive.
Qwerty is a fact of life... Live with it. (Score:3, Insightful)
This principle is part of human nature: People get used to some kind of technology/ideas and stick to it. Even when these concepts stop to be meaningful. I refer to the Querty-effect: Old typewriters had little pins with letters on them which hit an ink-soaked ribbon and presses it onto the paper. To prevent these pins from hitting eachother (which happened a lot), the qwerty keyboard was invented. The most abundant letters in English were as far apart as possible to prevent collisions. But a computer doen's have pins, so why do we still use a qwerty keybaord?
But also think of buttons in programmes: You press buttons in real life, why show them on a screen and press them with a virtual hand (the mouse cursor)? There are many more examples; the radio/TV frequency story if Mr. Reed being one of them.
The problem usually isn't the technology, it's the ideas that need to be changed. But sometimes technology improvements do get through, e.g. the DVD is nothing than an up-to date CD. MP3-player replacing the old walkman. Telefones replacing the telegraph.
Things change, ideas change. Some want to accellerate it, some want to slow it down. In the end, things just change at the rate they do and, as harsh as it sounds, there's nothing you can do about it. It just takes a little time...
Hardware can't make a difference--it's digital (Score:2, Insightful)
802.11 offers some proof of what he says (Score:3, Insightful)
If transmissions carry identification about which source they are coming from, then why couldn't a reciever be able to descriminate the information?? That is all he is saying. Although, it would seem that we would still want to regulate the power output to some extent... so I would completely agree with him that spectrum should not be restricted by licensing, but power output from a point source should still be.
Re:Interesting thing about radio signals (Score:2, Insightful)
I think the technical (Score:4, Insightful)
High quality broadcasts for everyone is a pipe dream. Want to know how that works out? Check out our Citizens Band. Not pretty at all.
I am in the process of getting an amateur radio license again. HAMs do more with less spectrum than just about anybody. Doing this has made me rethink spectrum allocations and how they are wasted. The amateur bands have very reasonable band plans that allow for a number of uses and work well.
Our primary problem with spectrum use is the band planning, not the avaliable resource. (Which is limited no matter what this guy says.)
Commercial and military uses basically get what they ask for and they ask for everything they can.
Comes back to this really. We live in a competitive culture. We have given companies the same rights we have. They are better competetors than we are.
We lose.
Our fault.
Re:Interesting thing about radio signals (Score:2, Insightful)
If there are two red lights shining from two different hilltops, do you have trouble distinguishing them?
You would if you could not distinguish the direction from which the light falls onto you - if your eyes were like these sensors that switch on outdoor lights when night falls. Which is what radio antennas are like currently.
If radio antennas were more like radio telescopes instead, a radio could "see" in which direction a particular radio station transmits from, and thus tell them apart. Currently that would be prohibitively expensive, but it does show that the supposed "interference" is an artifact of the sensing device, not of the waves themselves.
The myth of color spectrum interference (Score:3, Insightful)
You will need:
- A sheet of college-ruled paper
- A green marker
- A copy of Moby Dick
Open up the Moby Dick to the first page. Then, with the marker, start transcribing the text onto the sheet of paper -- "call me Ishmael" and all. When you run out of space, don't get more paper -- instead, just go back to the top of the sheet, and overwrite the text that's already there. When you are done with the entire Moby Dick, mail the sheet to Mr. Reed.Since there is no such thing as color spectrum interference, Mr. Reed should be able to read the entire Moby Dick just from the one sheet of paper.
This revolutionary discovery will surely eliminate waste, and save our rainforests... If only the paper-making companies didn't want to keep it under wraps !
Color is a bad analogy for the spectrum (Score:2, Insightful)
Color is a phenomenon of human visual perception. Specifically, color is a function of the power spectral distribution of incident light. Is yellow synonymous with 500nm? No. We may see light at 500nm as yellow, but we also see a mix of 650nm and 400nm as yellow too. This is the basis behind computer monitors-- even with only the ability to generating 3 different wavelengths (with different intensities), humans will perceive a very large number of colors.
There are many other ways of showing that color and frequency are not the same thing. Look at an artist's color wheel. We perceive a continuous circle of color. It's circular. But if color was a frequency, there would be a discontinuity as we wrap around from long wavelengths to short wavelengths.
Radios do not "perceive" color. They are interested in frequencies. Best not to confuse the two.
-Ed
Re:He's also right in some ways..... (Score:2, Insightful)
Even if you moved to a vacuum, there is still a limit, although I'm not sure what exactly that limit is. Certainly once the photon energy gets of the order of the mass-energy of a particle (say an electron) then all sorts of weird interactions can take place, such as annihilating two photons and producing an electron-positron pair.
Of course, you would hit the wall with more practical limits long before you reached this point.
As an aside, I have a very very crappy Logitech cordless IR mouse, but the maximum range is less than a foot, and it has to be pointed exactly at the receiver. So it is actually a lot less useable than an ordinary mouse, for which I have a whole desk to play with!
Re:Reed is wrong (Score:4, Insightful)
Yes. In practice at microwave frequencies the radio waves are rapidly absorbed. This actually raises the potential capacity of the network, since it acts a bit like sound deadening in a building.
The problem with interference arises because of imperfect spectral content and non ideal antenna response for both transmitters and receivers.
Not just that though. It also happens because one or other of the users of a particular band is using too much power, or is using it too much. Think of the airwaves as a multidrop ethernet and you're probably more what Reed is talking about. You wouldn't try to use 1 ethernet cable for a whole country- but they seem to want to do that with radio- why are the transmitters so 'loud'?
Also, are you claiming that the interference is likely to be so bad that none of the frequencies available to you are free? Because that's what it would take. Don't forget that you don't have to see the source directly, you can route through other radio users; and they can be situated at different angles. Also, consider that if both sources are interfering at your location, there's a high probability that they are interfering at other locations as well; a protocol that changes one of them to a different frequency automatically would do very well.
Interference is like being at a party: There are a lot of people talking, and your ears hear in all directions, so you have to be near the person you're trying to talk to.
Good analogy. Trouble is, ears are unidirectional. But if we give everyone cat ears, the party gets much quieter; even though cat ears are imperfect. Also if someone in the middle of the party needs to talk to someone across the room- he can always whisper it to his neighbour, who can pass it along, rather than standing up and bellowing at the top of his voice.
Re:sorry he's not being honest (Score:3, Insightful)
I realise the sarcasm, but, Yes, they will do just that if the FCC tells them fix it or recall it NOW! (or more likely, it wouldn't have reached the market with the bug since it couldn't pass the protocol certification). Presumably, the FCC would transition from frequency to protocol compliance. The problem with 802.11b is one of extremes. That is, other bands are impossible to license, but the one they're in is TOTALLY unregulated except for maximum radiated power. It's too far in the other direction.
Of course, if that band wasn't available without licensing and allocation, there would be no digital cordless, Bluetooth, or WiFi at all. They'd all still be mired in allocation squabbles and attempts to dominate the market by dominating the spectrum.
Re:complete bunk (Score:2, Insightful)
Simple answer: noise. [bldrdoc.gov] Noise [tscm.com] limits the ultimate sensitivity of ANY system.
n-QAM systems do just what you suggest: by using both AM and QPSK, n-QAM systems encode many bits on each symbol, increasing the spectral efficiency of the trasmission. Of course, that comes at the expense of noise immunity.
Re:What I found astounding... (Score:1, Insightful)
You're ignoring the fact that someone trying to decode a signal isn't interested in a particular time instant.
It's the time-varying nature of the signal that carries information. Take a time-varying signal, apply the Laplace Transform, and you've decomposed it into it's constituent frequencies.
This guy is basically screaming "go back and look at the math, people!", just like Heavyside did back when people were having the damndest time laying transatlantic cable.
They'd lay a cable, send a square pulse along it, and get a very wide and shallow normal curve pulse on the other end, because the different frequency components traveled down the line at different speeds. The dispersion made the line useless, it just ate whatever information you tried to send down it.
Heavyside looked at the math and realized you could make real (that is, non-ideal) transmission lines that are still dispersionless. But nobody payed any attention to him, because he was of modest education and was going against popular engineering knowledge at the time.
Suffice it to say they all shut up when his transatlantic cable worked and nobody elses did.
This guy's ideas aren't revolutionary to anybody educated in electrical engineering and familiar with the math of signal analysis.
And the technology is here, now, and has been for quite some time. All you really need to implement his ideas is a DSP chip (widespread and cheap) and the motivation. The motivation just currently isn't there, because there's no reason to innovate when the FCC goes around assigning huge swaths of spectrum to people.
Re:Someone hand this guy a physics book, stat! (Score:2, Insightful)
I don't think he meant there's infinite spectrum, just that it isn't being efficiently regulated, which is pretty obvious considering who's doing the regulating. I don't think you'd even have to rely on quantum mechanics to figure this out. Think of moving water around. Is it more efficient to use a big pipe intellegently, or tons of little pipes dumbly.
Could someone come in and "clog up the big pipe", by transmitting loudly on every frequency? Sure, but they could do the same thing now. However, to continue the analogy, it would actually be harder to clog the big pipe than the little one- water would re-route itself in the big pipe, wheras the small pipe would simply be blocked.
Finally, the problem isn't as much physics as just basic politics. Which scenario produces better goods and services? The government deciding which technology gets produced and who can use it, or technology companies participating in competition and producing technology, while consumers decide which is better? Just look at how long it's taken to do HDTV if you're unsure of how inefficient the FCC is. Compare the advances in radio technology to the advances in internet technology over the same period. Clearly, regulation suppresses innovation, and that's what the key issue is, whether Reed is correct or not.
Re:complete bunk (Score:3, Insightful)
There is a theoretical limit to how much information can be transmitted over any one channel of fixed width and signal to noise ration. How close are we to 100% of that theoretical limit?
Re:Yes, Claude Shannon says "he's full of shit." (Score:4, Insightful)
You mean through an information channel of finite bandwidth.
However radio paths exist in a 3D environment, which can multiply the number of channels of finite bandwidth. Reed's point is really about mesh networks and using spatial diversity receivers to create more "pipes" (i.e. channels) through the air at the same frequency.
In his concepts, mesh networked receivers can even work together to untangle interfered signals. It doesn't lead to infinite information capacity, but it sure is higher than what most radio spectrum is used for today.
Reed really shouldn't say that there isn't interference...it is that interference as physicists know it is a useful and constructive tool (as in holograms), unless your radio architecture is stupid (i.e. uni-frequency, uni-source broadcast).
Re:complete bunk (Score:2, Insightful)
And Shannon's law limits bandwidth to a known amount.
Re:This has been a known fact for a long time... (Score:5, Insightful)
Unfortunately, this is not true.
Suppose a city has two stations, one on 1600 kHz and one on 900 kHz. Let's add a station on 700 kHz, ok? Let's put him near the 1600 kHz station, since we don't want these damn antennas cluttering up the whole city. No problem with "well made equipment", right?
Now consider that near to both the 1600 and 700 antennas is a large, old, steel-framed building, containing tens of thousands of rivets and metal-to-metal joints. Some of these joints have some corrosion. Consider that there may be several such buildings. Why is this a problem?
Each joint is a potential non-linearity. Each joint is capable of taking the 1600 and 700 signal and creating the sum and difference signals and re-rediating them. The sum is 2300 kHz, outside the AM broadcast band. The difference is ... 900 kHz. The same frequency as an existing station.
Now consider if you live inside one of these buildings. You used to listen to the station on 900 kHz. Now you hear a wonderful mixed babbling of both the 1600 and 700 kHz stations -- and your radio has nothing to do with creating the problem.
Let's go one step further. These same non-linear conductors will cause sum and difference issues with single-frequency signals, too. The new station on 700 kHz will sum with itself and cause a signal on 1400 kHz. And it's even worse. The actual result will be signals on every multiple of 700 kHz well up into the shortwave bands. (If the non-linearity created a perfect square wave, you'd get only the odd harmonics, but these aren't perfect and you get even harmonics, too.)
Can't happen, you say? Yes, it can, and does. I've lived with this problem for the last 4 years from two nearby stations. It has finally gone away, since one of them moved their antenna location a mile further away, but before they did that, they made a lot of the spectrum useless here.
He's right and wrong at the same time. (Score:3, Insightful)
If you don't distinguish signals spatially then they will interfere at the receiver.
Simple example: I send two electromagnetic signals, one out of phase with the other. If you only receive at a single point, at certain locations you will get zero signal.
Unless you start talking about quantum stuff I don't see how you're going to distinguish the signals if you're measuring them at only one point.
Black Hole Sun (Score:2, Insightful)
If you take the fact that if every single creature on the planet were to look up at the sun at the exact same time, for any amount of time, the sun won't become dimmer or less warm in anyway. However, if our current technology were factored into the equation, it would take about 1/8 the world population to collapse the star and suck the planet into the resulting black hole.
Re:Reed is wrong (Score:2, Insightful)
The amazing thing, though, is that if someone you weren't listening to, halfway across the room, says your name, you hear it immediately. You can usually hear the conversation, too, if your attention's been drawn to it.
This attention mechanism in the human brain is basically very good SDR (Squishyware-Defined Radio), and provides a good analogy for real SDR: with enough intelligence in the reciever, even in a room crowded with noise, you can pick out the conversation that's of interest to you.