Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

The Myth of Radio Spectrum Interference

michael posted more than 11 years ago | from the monsters-and-boogiemen dept.

Wireless Networking 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.

cancel ×


Sorry! There are no comments related to the filter you selected.

at last!!! (-1, Offtopic)

Anonymous Coward | more than 11 years ago | (#5493543)


PLEASE what should I do next in my life ??!

Re:at last!!! (-1, Offtopic)

Anonymous Coward | more than 11 years ago | (#5493569)

and I succeed to post the SP too!!! YOOOHOOOOO my dreams come true!!

all your (-1)

greenalbatros (215035) | more than 11 years ago | (#5493563)

rf spectrums are belong to the government, you have to liscense them you know

If you support Slashdot, you support terrorism (-1, Troll)

Anonymous Coward | more than 11 years ago | (#5493565)

I wouldn't be surprised if VA Software itself was funneling money to Al Quaeda and other anti-American terrorist organizations, due to the rampant anti-American sentiment that runs rampant through both comments and the little snide remarks made by Michael, CmdrTaco, etc. in the story submissions.

Before you sign up for the subscription service so that you can continue to get your oh-so-beloved "FIRST POST!!!!!!", just ask yourself exactly where the money is going. Maybe to kill another 3,000 innocent Americans.

Remember what our President said: If you aren't for us, you are against us. They are tracking you. Slashdot and other anti-American, anti-capitalist websites ARE being watched, I can assure you. Watch what you say. Personally I hope the whole lot of you are arrested and subjected to sleep-deprivation interrogation techniques. Serves you right.

Re:If you support Slashdot, you support terrorism (0)

bigwayne (650386) | more than 11 years ago | (#5493601)

Sleep Deprivation? Hell, I haven't slept in days, bring it on.

Re:If you support Slashdot, you support terrorism (0)

Anonymous Coward | more than 11 years ago | (#5493674)

I woulda rated this one (Score: 5, Funny)

Interesting thing about radio signals (2, Interesting)

nexusone (470558) | more than 11 years ago | (#5493566)

I had a old radio that would make noises based on what my processor was doing...
Hard processing on the CPU, made the most interference.

Re:Interesting thing about radio signals (2, Funny)

nycsubway (79012) | more than 11 years ago | (#5493699)

While living in Hartford, CT, I used to listen to AM880 (out of NYC, a distance of about 200 miles) from my car. Whenever I stopped at a particular traffic light, the hum in the background got louder. When the light turned green, the hum got lower. After a while I was able to tell when the light turned green without even looking at it.

Radio? (-1)

rxed (634882) | more than 11 years ago | (#5493572)

michael is on the role today.

Anyone (1)

buktotruth (651740) | more than 11 years ago | (#5493573)

Given adaquate equipment, anyone could transmit thier webcam to EVERYONE with a tv. Sounds like that would make for some interesting tv.

Re:Anyone (1, Interesting)

Angry White Guy (521337) | more than 11 years ago | (#5493701)

As proven here, everyone has the right to free speech, but some of us should not be given the medium to exercise that voice.

The last thing that I want are a bunch of gaotse pics on my tv, and trolls on my radio. The news is bad enough.

Re:Anyone (0)

Anonymous Coward | more than 11 years ago | (#5493929)

preach on, brother

I........ (-1, Offtopic)

Anonymous Coward | more than 11 years ago | (#5493577)

Wanna touch on your buns!!!

Gonna be with this man ... Hafta take it like a man!!!

-cum join teh revolution!

I'm not so sure (5, Funny)

gomerbud (117904) | more than 11 years ago | (#5493585)

I know a physicist who claims that pi is in fact rational. He claims that the only reason we don't realize it yet is because of the current limitations of our circle measuring devices.

Re:I'm not so sure (1)

kfg (145172) | more than 11 years ago | (#5493661)

I don't know about that. I use the finest piece of string I could find and it still looks irrational to me.


Sorry, Obligitory Simpsons Quote (2, Funny)

da3dAlus (20553) | more than 11 years ago | (#5493775)

Prof. Frink: "A-hem, um, ahem! Excuse me!....Pi is exactly 3!!"

Audience: "HUH?!? WHAT?!?"

Prof. Frink: "Sorry I had to do that, but now that I have your attention..."

interference... (-1)

Anonymous Coward | more than 11 years ago | (#5493588)

The biggest interference I know about is when is when the open score morons blanter on about how great the ogg format is. It has been proven that the ".wma" is the best and it even works on my mp3 player.

I can read the mind of the submitter... (-1, Flamebait)

LePrince (604021) | more than 11 years ago | (#5493590)

It says :

"Hmm, this story is boring, it'll get rejected. BUT, if I had a link to a GNU project, it'll get posted... Cool !"

Sorry for the sarcasm, but not everything should revolve around GNU... 'neway. Just my .02... from a guy who has 0 accepted stories, 7 rejected. ;-)

Meme (-1, Troll)

Anonymous Coward | more than 11 years ago | (#5493591)

Look at me, I just read an article on memes, and they were on Wired's Hot List, or if they weren't they should be, so I'm going to use 'memes' so everyone knows with certainty that I'm a dork with no life that you all can identify with instead of using something like 'metaphor' or 'idea' which normal intelligent people use and is perfectly correct in this instance, so please come back to Slashdot every few seconds since we're all so smart here.

Re:Meme (1)

Elbereth (58257) | more than 11 years ago | (#5493765)

I think by "meme" he means "me! me! look at me!"

fascinating article? (0)

Anonymous Coward | more than 11 years ago | (#5493600)

Let's stretch Salon's death row for as long as possible, that makes them produce good stuff!

The article is crap (0, Troll)

psylent (638032) | more than 11 years ago | (#5493604)

It is just a bunch of meaningless words slapped together with phrases that make it sound intelligent. This guy looks like a CS grad or (oh horrors) a digital designer. I would really love to see his credentials. He has no clue about communication theory. My profs would flunk him.

Re:The article is crap (5, Informative)

W32.Klez.A (656478) | more than 11 years ago | (#5493723)

" This guy looks like a CS grad or (oh horrors) a digital designer. I would really love to see his credentials."

David Reed is many things, but crackpot is not one of them. He was a professor of computer science at MIT, then chief scientist at Software Arts during its VisiCalc days, and then the chief scientist at Lotus during its 1-2-3 days. But he is probably best known as a coauthor of the paper that got the Internet's architecture right: "End-to-End Arguments in System Design."

thank you for reading the article.

Re:The article is crap (2)

coult (200316) | more than 11 years ago | (#5493741)

So being a spreadsheet developer makes you an expert in electromagnetics?

Re:The article is crap (0)

Anonymous Coward | more than 11 years ago | (#5493770)

From reading the article, I'd say it didn't.

Re:The article is crap (1, Funny)

Anonymous Coward | more than 11 years ago | (#5493777)

and at MIT of all places?

I went to a demo of `instruments of the future` they put on in london. It looked like the sort of crap you`d come up with if you`d left your degree course until the last minute, got really stoned and said `lets take a keyboard....but remove the keys and make it so the angle you hold it at changes the pitch`. Yeah, but how do you play it? How do you reproduce a melody. " it around, see....and then..."

Re:The article is crap (2, Interesting)

Ed Avis (5917) | more than 11 years ago | (#5493749)

I dunno, what about:

- Two transmitters in two different places, but with an overlapping range, both broadcast on the same frequency.

- A receiver is halfway between the two transmitters and so within range of both.

- The receiver has two or more antennae, each antenna has some directionality. You do a lot of DSPing in software to distinguish the two signals even though they are both on the same frequency.

Re:The article is crap (4, Interesting)

pe1rxq (141710) | more than 11 years ago | (#5493914)

What the guy in the article is talking about is using spread spectrum techniques.
This is done by spreading your signal over a large spectrum with a pseudo random key. The number of possible keys is still limited (There has to be a certain difference between two keys for it two work) and thus you still have a maximum number of users although things like roaming are a lot easier since you are limited by keys overlapping and not range overlapping.

This is what is being done in CDMA cellphones, Wireless Lan, Bluetooth etc. It is nothing new, already happening and you still need regulation to make sure the spectrum doesn't get completly unusable.


Re:The article is crap (1)

1fitz2many (409956) | more than 11 years ago | (#5493943)

Good idea... interference isn't a problem for radio dish arrays, like the VLA [] .

The greater the number of transmitters that are out there, you need more receiver antennae (and processing power) to distinguish which direction the desired signal is coming from.

Thus "unlimited bandwidth for everyone" doesn't seem as economical, especially if your receivers are really expensive [] .

Re:The article is crap (1)

IAR80 (598046) | more than 11 years ago | (#5493874)

Is it just me or more and more tabloid stories find their way on the slashdot front page?

Multiuser Detection (2, Interesting)

s20451 (410424) | more than 11 years ago | (#5493888)

He's probably talking about multiuser detection, which is an idea that has been around for about 20 years. The idea is that instead of observing only the signal that you're interested in, you also observe every other transmitted signal. If the other signals are digital, you can reconstruct those signals electronically and subtract the resulting interference. Unfortunately it is a hideously complicated problem in practice, and is not terribly robust, so no major wireless standard incorporates it (not even any of the 3G standards).

Limited Quantities (3, Informative)

evilviper (135110) | more than 11 years ago | (#5493606)

Interference is a fact of life. Sure, the technology can improve and allow us to do the same things with less of the spectrum, and other things like spread-spectrum can come along and lessen the interference problem, but spectrum is still a limited resource.

The FCC is currently forcing the switch to digital communications all over, which is shrinking the required spectrum. I'm sure when other technologies mature, they will make use of those as well to further free-up the spectrum.

shrinking the required spectrum.... (1)

oliverthered (187439) | more than 11 years ago | (#5493652)

by reducing the impact of interference.

You get less for your monet with digital, but at least you know what your getting.

Re:shrinking the required spectrum.... (4, Informative)

stevew (4845) | more than 11 years ago | (#5493702)

Uhm - no. The reduction in radio frequency usage is due to the adoption of compression of the video stream. These are still going to be multi-MegaWatt Xmitters because of the frequency(UHF), and the distance they want to cover. Put two of these on the same frequency, close enough, and you have inteference at the receiver. PERIOD.

A major part of communications theory is issues dealing with bit-error rates, and interference. It is a reality. Now we can move to things like "spread spectrum" but even this is no panacea. Fact - for a given bit errror rate, bandwidth, and communications path conditions - there are a finite number of spread spectrum transmitters than can coexist in the same band before the bit-error rate is exceeded!

How do I know? Well I've been a ham for 25 years giving me practical experience, and I'm a EE as well.

Re:Limited Quantities (2, Insightful)

i0chondriac (310892) | more than 11 years ago | (#5493693)

However, the FCC is selling the freed b/w to phone companies. Even when the technology allows us to use mere fractions of the currently allocated spectrums, you can be guaranteed that those free spectrums will be unavailable to the public.

Patented Colours! (4, Funny)

BinaryCodedDecimal (646968) | more than 11 years ago | (#5493607)

From the article:

Pantone may own the standard numbers by which digital designers refer to colors, but only the FCC can give you an exclusive license to a color itself.

So I could patent the wavelength of a colour of my choosing, and claim royalties every time someone uses a colour that matches my wavelength? Now there's a way to get rich quick...

Except people wearing clothes using your colour could run away from you really quickly and cause red shift:

"See? It's not the same as your colour. It's very slightly more red. You can't sue me!"

Re:Patented Colours! (1)

morie (227571) | more than 11 years ago | (#5493778)

Or they can come at you really fast.

They then either claim violet shifting or just run into you. They might even hit you somwhere where it hurts...

Not going to happen (4, Insightful)

SirLantos (559182) | more than 11 years ago | (#5493611)

If Reed is right, nearly a century of government policy on how to best administer the airwaves needs to be reconfigured, from the bottom up.

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,

complete bunk (4, Insightful)

coult (200316) | more than 11 years ago | (#5493627)

This article is complete bunk. Yes, its true that radio frequencies are like colors. So imagine this scenario: you are receiving signals from someone who is using 'green'. They are flashing a huge green light, and you can pick up the pulses they are sending by being bathed in the green light. Now someone else comes along and also starts flashing a huge green light. You can't read the signal any more, because there are now two huge green lights bathing you with their signals. How can you tell which pulse is coming from which light? You can't! That's interference.

Re:complete bunk (2, Interesting)

Anonymous Coward | more than 11 years ago | (#5493787)

With a single omni-directional antennae I think that you are roughly right.

With multiple antennae you can use signal processing to separate signals from different directions, just like we do with our ears when listening to people.

By your logic government should regulate people talking at certain places :) Because if two people are talking there would be no way to distinguish the two.

Re:complete bunk (3, Insightful)

coult (200316) | more than 11 years ago | (#5493838)

Sure, you can build in directional antennae, but then your radio has to know what direction the station is in, and be able to keep the antenna pointed in the right direction. Can your walkman keep its antenna pointed in the right direction while you are vigorously jogging? Not for $20 it couldn't.

Re:complete bunk (2, Informative)

IAR80 (598046) | more than 11 years ago | (#5493915)

The directional anntena has what it is called a main lobe whitch is usually measured in degerees and it is greater than 0, therefore two radio signals using the same frequency and resising in the same lobe will certainly interfere.

Re:complete bunk (1, Informative)

Anonymous Coward | more than 11 years ago | (#5493818)

Um, if two people are flashing a huge green light at me from different directions, I sure can tell the difference and know where the pulses come from - dunno about you...

Re:complete bunk (1)

coult (200316) | more than 11 years ago | (#5493861)

The analogy isn't a complete one. What if you can only see the green light that is reflecting off of diffuse clouds overhead - can you still separate the signals?

Re:complete bunk (1)

kryptobiotic (451986) | more than 11 years ago | (#5493869)

While your scenario works fails to work using simple isotropic antennas like we use today, it could work with a more advanced system. All you need is some directivity. A phased array with some logic controlling it could scan all directions for a given 'color', locate the sources, and seperate the two signals. I know that the multipath/scattering issue would cause some problems but they might not be insurmountable.

The 'red' traffic light does not stop you from seeing the 'red' car next to you.

Re:complete bunk (4, Interesting)

nicodaemos (454358) | more than 11 years ago | (#5493892)

I'm not sure how you can consider the article complete bunk if you've had a sufficient college physics class that covered the particle-wave duality of electromagnetic waves.

In your example, it's true that your eyes can't discern the difference between the signals and this is classically how we've viewed radio detectors. However, the information in the signals is not lost - you're ability to detect between them is altered, but the photons themselves are unaltered.

If you switch to a different type of sensor or encoding scheme - for example, utilize frequency hopping (aka spread spectrum) then you could easily broadcast the two signals over the same range of frequencies (colors).

Overall the article has a lot of merit in providing a different and, in my mind, compelling metaphor of bandwidth as colors as opposed to the classical bandwidth as land. As to his ideas of limitless bandwidth being true, the idea is beyond my ability to see how this is feasible, but that does not detract from his idea that we could actually be communicating a LOT more over the current spectrum than we are today.

If the theory is correct (1)

Tebriel (192168) | more than 11 years ago | (#5493628)

Think of DRM ramifications: your reciever could only allow you to receive things from "approved spectrums." Or only allow you to record things from "unsecured" spectrums.

Salon ads (0, Offtopic)

MagPulse (316) | more than 11 years ago | (#5493640)

How brain-damaged do you have to be to read that article with text right next to the car ad with letters moving around and the whole thing flashing at you? I'm reminded of an article that said something like "the site may as well stick a sign up saying 'we hate you, please go away'".

Re:Salon ads (0)

Anonymous Coward | more than 11 years ago | (#5493677)

Hmm, I saw none of what you're describing.. thanks to Proxomitron [] . ;)

Partially..... (3, Insightful)

Chanc_Gorkon (94133) | more than 11 years ago | (#5493650)

Radio Interference could partially be attributed to crappy equipment. Anyone remember when keyboard cases were metal (ala the old 88 and 101 key Keyboards that came on original IBM PC's)? Now it's plastic. Now there's not even a real keyswitch in a keyboard. Most keyboards kind of look like the rubber keyboards once you open them up. Only difference is the plastic key caps. Not only that, but most equipment is so rf leaky that you can hear them when you put them next to a radio. My Nextel phone always makes my monitor tick and sometimes flicker when I use it. The filtering on this stuff is crap. If manufacturers of consumer grade stuff would spend a little more cash, then their device would not cause interference. Some times the cash is so little, it's just like a 3 dollar difference. IN fact, nix the "grades" of equipment. Make it all one grade. That way everyone will not interfere with anyone else. Granted, this guy is probably not spot on, but most consumer grade stuff is crap.

Re:Partially..... (1)

jandrese (485) | more than 11 years ago | (#5493907)

Um, aren't Cell phones, by definintion, supposed to put out RF when in use? I don't think I'd define that as "leakage".

Wha? (4, Informative)

sg3000 (87992) | more than 11 years ago | (#5493653)

Perhaps, I'm not the most knowledgeable guy on RF interface, but I went to The University of Texas at Austin, got my degree in electrical engineering (studying electromagnetics), worked at Ericsson designed cellular systems and RF planning, worked at a company making "smart antennas" for cellular systems. From my experience, I had a hard time understanding what he was talking about. "Spectrum is more like the colors of the rainbow"? Of course it is, that's how the radio spectrum works. But then he goes off on, "There's no scarcity of spectrum any more than there's a scarcity of the color green." Which makes little sense to me.

It's not that using a radio frequency somehow "depletes" a resource -- it means that if you put a green object in a green room with green lights, after a point you won't be able to see the object any more, kind of like how camouflage works. The problem is when you have a lot of signaling broadcasting in an area, the noise level can increase to the point that no single signal can be resolved. The classic example is how it's very difficult to understand a particular conversation in a noisy room. And that's why you have to generally parcel out radio spectrum and define limits on how it can be used (signal strength, bandwidth characteristics, noise levels, coverage patterns, etc)

That guy's nutty analogy makes me think he's a leftover of the dotcom era -- when eyeballs was more important than revenue and other silly things. Admittedly, I should read the whole article, but the first few paragraphs made me feel like I'm talking to a crazy guy on the bus.

Re:Wha? (1, Informative)

Anonymous Coward | more than 11 years ago | (#5493794)

It got no better after the first couple of paragraphs. He seemed to be implying that if we used the spectrum more efficiently then interference would be minimized (except he kept saying that this meant there was no sch thing as intereference which was a bit confusing).
As interference minimization is really nothing new and he gave no cutting edge examples (the only example he mentioned was frequency hopping!) the article was simply high on hyperbolae (there is no such thing as interference) and low on any actual information.

Re:Wha? (3, Interesting)

TheMidget (512188) | more than 11 years ago | (#5493876)

I must admin that I also only read the first page of the article, but I think what he is trying to get at is directionality and/or spatial locality. You can put several green objects in one room, and you are able to see them all, because they are at different places in that room.

However, far from being revolutionary, his 'discovery' is a well known fact, which is already in wide use by now:

  • the directional antenna that the Wifi freaks are so fond of...
  • satellites at different orbital positions reuse the same frequencies...
  • FM spectrum is reused as well. Ever noticed that when driving long distances you get different radio stations on the same frequency?
  • mobile phone cells (d'oh...)

Also, his analogy breaks when you compare wavelengths: light having much shorter waves is much more directional (allowing for the pinhole camera phenomenon) whereas radio need much bigger spatial separation to avoid interference. While you can put several green objects into one room, and still distinguish them, you need much larger cells for RF.

Re:Wha? (2, Informative)

puppet10 (84610) | more than 11 years ago | (#5493894)

The point I think the author is making is that there is a (theoreticallly) infinately divisible analog space contained between any two wavelengths of EM spectrum. For example the green at 510nm and the green at 520nm are both 'green' but with sufficient technological enhancement can be distinguished from one another.

Your point is also a good one, in that from an engineering point of view as the signals get closer together in the spectrum the ability to distinguish one signal from another is reduced.

However his answer to this is that the current method of spectrum allocation does a terrible job at utilizing the available spectrum partly because the transceviers we use for radio and television broadcast for example are relatively stupid and inefficient compared to what we could be doing, partly because of how the historical licensing stucture grew to be fixed ownership of particular frequencies and the space around them to allow dumb recievers to utilise them.

His idea is to try to promote the reduction of frequency requirements to the least restrictive set of rules to allow a reciever to recieve a broadcast from a broadcaster. One example given is through the use of smarter SDRs (software defined radios) to make more efficient use of the available spectrum.

bOINGbOING transcript from the spectrum conference (2, Informative)

lopati (74873) | more than 11 years ago | (#5493657)

Lessig: ...Coase's arguments [] reflected the state of the art at the time. Property was the best way to allocate spectrum in 1959. But it's the wrong answer today. Not because property does no good -- in fact, it does a great deal of good. This should not be taken to imply that administrative allocations are inevitably worse -- a market has costs, and if those costs exceed the value, then markets result in misallocation. Coase's insight -- most prescient -- is that spectrum is not in its nature rivalrous. It's not a thing at all. Colors, sounds correspond to frequency.

Sort of right; sort of wrong (0)

Anonymous Coward | more than 11 years ago | (#5493675)

I mean, yeah, there is an infinite number of spectrum "buckets" if you get better and better tuned equipment. So what? We don't have perfect equipment. Maybe we could manage to split down the bands more finely but there are still a finite number.

As for "photons don't interfere with each other" - this is bullshit. Photons act like waves and waves interfere with each other.

Too optimistic, in my view (3, Insightful)

archeopterix (594938) | more than 11 years ago | (#5493676)

From the article:
Reed believes that as more and more of radio's basic signal-processing functions are defined in software, rather than etched into hardware, radios will be able to adapt as conditions change, even after they are in use. Reed sees a world of "polite" radios that will negotiate new conversational protocols and ask for assistance from their radio peers.
I see a tragedy of the commons [] waiting to happen.

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.

Re:Too optimistic, in my view (1)

sjames (1099) | more than 11 years ago | (#5493816)

Sure, "Maximize your bandwidth with our new RadioBooster!!!" (at the cost of your neighbors).

That's why he sees a continuing role for the FCC. It's just that they would ensure that devices obey the necessary protocol rules rather than their current role of making sure that only megacorps can get new allocations and only a few controllable broadcasters can reach an actual audience (gotta keep those naughty words off the air!)

Good analogy (1)

rnelsonee (98732) | more than 11 years ago | (#5493683)

So he compares radio waves to that of visible light -- a good analogy, but it doesn't mean his argument holds up. This article jumps around a bit, from the beginning to where he mentions quantum mechanics, to adopting frequency-hopping algorithms. I just don't get the bit in the beginning. If you've got two stations allowed to broadcast, say, Forest Green, in the air at the same time, then how can an optical receiver (say, my eye) discern between the two? In the broadcast world, you're going to have multiple receivers trying to 'tune in' to multiple sources. Broadcasting at the same freq. and the same time will alias the signals.

Re:Good analogy (1)

Feezle (605987) | more than 11 years ago | (#5493882)

how can an optical receiver (say, my eye) discern between the two?

My eye can distinguish between two green light sources, as long as they aren't in precisely the same direction. So can a camera obscura.

A similar idea works just fine with radio, if you have a directional antenna. My old GE SuperRadio has a great ferrite rod that lets me selectively listen to two AM stations on the same frequency by orienting the rod to null-out the station that I don't want to hear. A better antenna might let me distinguish between more than two stations on the same frequency.

Never believe a "technologist" (0)

Anonymous Coward | more than 11 years ago | (#5493684)

It just means that he failed out of engineering school and is good at BS.

This has been a known fact for a long time... (4, Insightful)

geewiz45 (310903) | more than 11 years ago | (#5493685)

Large radio broadcasters love to claim this when there is a threat of a new station being added in their market. Not because there is a possibility of interference if the frequencies are close - they're scared of competition.

Well made and tuned equipment can eliminate any chance of interference and allow for more radio stations within an area. However, organizations like 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:

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.

sorry he's not being honest (3, Interesting)

plcurechax (247883) | more than 11 years ago | (#5493690)

David Reed is not being completely honest, he is being overly optimistic, IMHO, and hasn't demostrated with actual experiments his claims.

Based on stories of 802.11b (Wi-Fi) and/or Bluetooth suffering from interference either from like-protocoled devices being operated by other parties, or cross-protocol interference which results in the one or both protocols not being effective in their data transmissions, and these are supposed to be advanced intelligent devices which don't suffer from interference due to their use of Spread Spectrum technology, and intelligent software controlled radios (which may or may not be software defined radio - SDR).

So unless he can demostrate experimental evidence, I'm a scepetic.

Re:sorry he's not being honest (1)

sjames (1099) | more than 11 years ago | (#5493863)

The problem is that none of those devices are software updatable, and they don't have a minimal negotiation protocol in common. The biggest offender is cordless phones (that have no negotiation protocol other than do what you want until you can hear the base station). If they negotiated, they could coexist with little problem.

Consider how it would be if the phone spoke 802.11b and used 64Kbps over ethernet.

Re:sorry he's not being honest (1)

plcurechax (247883) | more than 11 years ago | (#5493935)

The problem exists in two different 802.11b Wireless LANs in the same area (building) today, that is they use the same "intelligent" protocol, yet suffer performance degradation of interference, beyond being a shared transport (like 10BaseT Ethernet via a hub).

Uncertainty Principle (2, Insightful)

gomerbud (117904) | more than 11 years ago | (#5493704)

Heres part of the real problem. In order to communicate over radio waves, you must use a well defined bandwidth for your transmission and reception. As we scale up the number of simultaneous connections over a range of frequencies, each individual connection must be allocated a central frequency and an ever decreasing bandwidth. As the bandwidth gets smaller and smaller, we are decreasing the uncertainty in photon energy. If we keep decreasing the bandwidth, then we get to a point where we have a nontrivial uncertainty in time. This uncertainty in time makes it so that we cannot properly measure the time variation of our signal. Thus, there is a point when our bandwidth is so small that we cannot recieve a reasonable signal. This is interference in transmission itself. If you can figure out how to filter this out, you'll win a nobel prize.

If i wasnt so sleep deprived, i could give some approximations with numbers and stuff.

The Stanford Spectrum Conference... (4, Informative)

Remik (412425) | more than 11 years ago | (#5493722)

...just took place earlier this month. There's a lot of good information here [] . An audio/video archive of the conference will be available on the 17th for those who didn't catch the webcast.

The idea that Spectrum doesn't need to be regulated is quite old, and it seems more and more likely to be valid. In any case, the idea that it needs to be controlled by government interests is less and less likely.


Re:The Stanford Spectrum Conference... (0)

Anonymous Coward | more than 11 years ago | (#5493841)

Who modded this Troll?!

I am an engineer working in spectrum, and I was at the Stanford conference. Everyone making lots of haughty remarks about quantum and how it's not feasible needs to go read the papers [] presented at this conference. Smart/spread spectrum is here, it's just a matter of time.

Whats red, green, blue (0)

Anonymous Coward | more than 11 years ago | (#5493725)

...yellow, purple and orange?

An Italian radio wave dressed up.

The guy is a nut... (1)

aallan (68633) | more than 11 years ago | (#5493739)

There's no scarcity of spectrum any more than there's a scarcity of the color green....

I can't believe Salon published the article, or that it got picked up by Slashdot. This is bogus science [] , and the guy is clearly a nut. Perhaps the editors should read their own articles [] ?


Re:The guy is a nut... (0)

Anonymous Coward | more than 11 years ago | (#5493815)

Bogus is right! but it should not even be qualified as "science". Clearly this person hasn't a clue about how these things work or the basic physics of EM wave propagation (does he think everyone can transmit a delta-function!) - actually we can power our delta-function transmitters with perpertual motion machines as well. Don't you just hate the laws of thermodynamics!

Re:The guy is a nut... (1)

kirkjobsluder (520465) | more than 11 years ago | (#5493941)

I don't think it is bogus science. But I do think that the article does not describe the issues very well. His main argument is that spectrum scarcity can be solved using radio transmission protocols analogous to the internet where transmitters dynamically negotiate frequency with the receiver. There is the big catch, IF you adopt this particular technology there is no shortage of spectrum. It is rather like saying that there is no shortage of spectum if everyone agreed to use CW and morse code (CW has a very narrow bandwidth). As opposed to FM or AM.

I think that the point he is missing is that applications tend to expand to fill available bandwidth.

interesting, but a bit arrogant (2, Insightful)

Joe the Lesser (533425) | more than 11 years ago | (#5493743)

He argues that interference is a symptom of inadequate equipment

As my chemistry teacher once said to me, 'A poor craftsman blames his tools'

well duh! (1)

Nick_Gunz (141133) | more than 11 years ago | (#5493945)

Of course a poor crafstman blames his tools; a poor craftsman can't afford good tools!

reverse color metaphor (0)

Anonymous Coward | more than 11 years ago | (#5493748)

Given that visible light is part of the radio spectrum, wouldn't it be possible to broadcast light in the same way as a radio transmitter broadcasts?

Or for that matter, would it be possible to use some sort of LED setup to broadcast non-light signals such as TV or radio? Based on what little I know about LEDs, if this were possible, FM-type broadcasts would be significantly more difficult than AM-style broadcasts.

And the cost to "upgrade" is? (1)

plcurechax (247883) | more than 11 years ago | (#5493751)

He also thinks that everyone is going to start using $200 ADC/DAC subsystems in your $2 garage door opener or $20 walkman.

I don't think any "economy of scale" will scale far enough to drop high performance DAC prices from >$50 to $0.50.

Covered in a book (1)

truthsearch (249536) | more than 11 years ago | (#5493763)

The political and other non-technical aspects of this are covered in The Future Of Ideas by Lawrence Lessig [] . Good read.

Take a college physics class 'tard (1, Informative)

Anonymous Coward | more than 11 years ago | (#5493766)

Fact: All radio, visible light, cosmic rays, infrared, x-rays all the good Electromagnetic radiation exhibits interference. Do a search for the double slit experiment if you don't believe light acts the same way. If you let light through a pinhole as he suggests, and then sent it through two more pinholes so there were essentially two sources of coherent light spaced apart, you'd get interference. And, this still happens if you're only letting a photon through at a time. Basic quantum theory people....

Makes sense (0, Offtopic)

t0ny (590331) | more than 11 years ago | (#5493769)

If I shout across a crowded room, the other people talking could, in a manner of speaking, be called interferrence. However, its not a failure of the sound waves projecting from my mouth, its a failure of the ears on the person across the room. If you had one of those satelite dish looking microphones you could hear me better.

/.'s now the shitter that M$ House lacked (0)

Anonymous Coward | more than 11 years ago | (#5493782)

It's now just one step removed from posting stories about alien abductions and three-headed babies.

And the daily crop of "bash John Ashcroft" stories haven't even been posted yet!

Reed is wrong (5, Insightful)

Inspector Lopez (466767) | more than 11 years ago | (#5493788)

Reed's article is based on the observation that Maxwell's Equations are linear (for most materials) and that, therefore the waves pass through each other without modification (again, unless you're in pretty exotic environments --- early universe, etc.) The problem with interference arises because of imperfect spectral content and non ideal antenna response for both transmitters and receivers. 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.

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 ... the reason that it works is that your eyes have very fine angular sensitivity (high quality antennas) compared to your ears.

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.

Like the article? (1)

thesolo (131008) | more than 11 years ago | (#5493792)

Just a reminder, if you enjoyed reading this Salon article (or any of the dozens of others that /. has posted), you should consider becoming a Salon member! []

I've joined, and it was well worth the money. Their articles on the state of the music industry, Payola, etc., were enough to deserve my cash.

He's also right in some ways..... (2, Informative)

Chanc_Gorkon (94133) | more than 11 years ago | (#5493803)

The radio spectrum isn't a finite resource. How much can you increase frequency? You can infinitely increase it. What is limited is usable frequency. Usable frequency is limited not just by technology, but also by the physics of the environment. I have always said that trying to implement 802.11b like what has been done with cellular tech cannot be done because of it's frequency. 802.11b uses 2.4 GHz band of frequency. The physics of the problem makes 2.4 GHz not suited for long haul. 2.4 GHz can go through buildings but can only go around 50 feet. You could extend that by using a beam or a better omnidirectional antenna, but your definitely not going to go miles in most current instalations. Now HF frequencies can go thousands of miles with current equipment. I am sure BOTH RF frequency bands can and do go thousands of miles and maybe even light years, but current technology limits that. If the signal is so low in strength that current recievers can't detect it, then it's not useful. It's finite. Theoretically, if you can develop a reciver that can recieve the very very low strength signal, then you could....possibly say that a RF wave can be infinite.....but conditions have to be perfect. No walls and a total vacuum. On the other hand, interference that we currently have comes from going for that extra buck. If one were to build proper recievers and transmitters, they would be very expensive, but they would not be susceptible to interference. Cheap devices absolutly breed interference.

Re:He's also right in some ways..... (1)

October_30th (531777) | more than 11 years ago | (#5493835)

How much can you increase frequency? You can infinitely increase it.


I'm waiting for the day when I can get a cellphone that operates in the X-ray or, even better, gamma-radiation regime?

Color Wheel (4, Insightful)

RichMan (8097) | more than 11 years ago | (#5493804)

Sure a pure frequency is nice and clean. As soon as you start modulating a signal it smears itself all over the spectrum using up adjacent space. So yes a pure transmission is nicely separable but as soon as you put any signal on it the whole thing smears out.

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.

Another myth! (-1, Troll)

Anonymous Coward | more than 11 years ago | (#5493809)

The "Moon": A Ridiculous Liberal Myth

It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! Daddy's Roommate? God Almighty!)

Documentaries such as Enemy of the State have accurately portrayed the elaborate, byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors .. the next time you're out in the backyard exercising your Second Amendment rights, the liberals will see it! These satellites are sensitive enough to tell the difference between a Colt .45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you.

Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for that particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who dare to make use of their God-given rights at night!

Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, there is no mention of the "moon" anywhere in literature or historical documents -- anywhere -- before 1950. That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down.

Ultra Wide Band (2, Interesting)

plcurechax (247883) | more than 11 years ago | (#5493829)

Ah yes, David Reed and Dewayne Hendricks on UWB: The UWB currently proposed is a simple first step. UWB transceivers are simple and could be quite low-cost. And UWB can transmit an enormous amount of information in a very short burst ...

Of course UWB is still in the laboratory, and these two think that the FCC should rewrite the laws now for a technology that may work well (i.e. not cause widespread interference), and may be cheap. Except we don't know yet!

Baloney (1, Insightful)

pcraven (191172) | more than 11 years ago | (#5493831)

Looks like Michael needs Carl Segan's Baloney Detection Kit [] .

Re:Baloney (1)

IAR80 (598046) | more than 11 years ago | (#5493940)

Or "Science as candle in the dark" by the same author.

In a perfect world... (0)

Anonymous Coward | more than 11 years ago | (#5493851)

Does anyone know of a working arrangment for consecutive transmissions on the same frequency? Something beyond a protocol of how to share transmission rights based on time. To illistrate, assume that I have a green flashlight that runs on two AA batteries. If I am shining my green flashlight to the west, and a local radio station, KRAP, is shining its 1M watt green light in the same direction is there any method to decifer the two seperate signals?

As another thought, imagine a beowulf clus.... uh, nevermind.

Big difference betwqeen RF and optical receivers (4, Interesting)

AlecC (512609) | more than 11 years ago | (#5493860)

The big different between RF and optical receives is that RF receivers (radios) are usually fairly omnidirectional, whereas optical receivers (eyes) are usually pretty directional. In part, this derives from the physics of the things - longer waves go turn more round obstacles, and tend to broadcast wide angle if their wavelength is similar in size to their aerial.

The way we use radio takes advantage of this - we don't have to aim the antenna for our car radio, and we prefer it that way so we can listen as we drive. This leads to a promiscuous sort of receiver, which is subject to interference. I think it is going a bit far to say thai is because of the legislative environment or technological background - it is because it is the way we *want* it to be.

At optical weavelengths, we *want* a directional, even a focussed, image - and our eyes produce it. In between, we tend to use directional transmissions with point-to-point microwave dishes.

However, the simple reflector style lens, depending upon newtoinian optics to fouca an image of the transmitter onto the receiver, is not the only way to receive a signal. People are already working on multi-aerial systems which take a "holographic" approach to reconstructing the signal. There was an article about one of them on /. a few months ago. These could very well lock onto the signal from a particular direction, and ignore signals on the same frequencey from a different direction.

I think the frequencxy hopping bit is actually somewhat of a red herring. It doesn't generate new spectrum, it meakes better use of the spctrum we have. It gets rid of the wastage caused by blank safety space betwenn radio stations both in geographical space and in spectum space.

Interference _is_ real (1)

Vollernurd (232458) | more than 11 years ago | (#5493864)

As long as the equipment we use daily remains "inadequate" enough to not distinguish finely enough the different transmissions we see, my aural pleasure will always be shat-upon by Pirate broadcasts.

There's many Pirate radio stations breaodcasting all over our FM bands and it leaves me with no way to listen to a radio programmes that I am interested in.

Not that I'm against Pirate radio, I just think that if they opened up the spectrum more, then cramming 100+ stations into a very narrow band would be unecessary.

Open Source TV Transmitter (1)

randomErr (172078) | more than 11 years ago | (#5493884)

So how about an easy to use open source TV transmitter? I mean when HD hits there will be tons of TV we could do some low power broadcasting to.

He's right (4, Insightful)

Fapestniegd (34586) | more than 11 years ago | (#5493898)

with improved transceivers we could open the spectrum up to high-quality broadcasts by anyone
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.

Push here, it comes out there (1)

daves (23318) | more than 11 years ago | (#5493900)

If he is right, then cheap radios are a myth.

Qwerty is a fact of life... Live with it. (3, Insightful)

asciimonster (305672) | more than 11 years ago | (#5493906)

There are many concepts that, if tweaked to the current technology, could be greatly improved. However, keeping old technology also has it's merits: Firstly, it's proven technology so all quicks are known or resolved; New technology undoubtedly has more problems. Even the threat that new technology has more problems, people will not use it. Also, changing to a new kind of technology require huge investments. New technology has to be pretty profitable if it is to overcome the investments made in the old one.

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...

There are more sensitive radio receivers out there (5, Interesting)

tjwhaynes (114792) | more than 11 years ago | (#5493913)

and they are known as radio telescopes!

Radio Astronomers have a hard enough time keeping the important wavebands free of interference without the radio spectrum being unregulated. Lots of useful, hard science is being done by the radio telescopes around the world observing the machinations of galaxies out in the distant universe. One of the key problems is that these signals are amazingly faint. The standard unit used in radio measurements is the Jansky - thats 10^(-26) Joules per second per square metre - which should give you some indication as to how faint. Lift that coke can off the floor onto the table and you've just used up more energy than has been received from distant galaxies by ALL the radio telescopes on the surface of the planet.

Terestrial radio transmitters are so many orders of magnitude stronger than these signals that any sideband transmissions even 90db below peak transmission still totally swamps the surrounding spectrum. And very few transmitters are truely 'perfect'. It's not as though a transmitter broadcasting at frequency X with HWHM waveband Y can't be detected at X +/- 8 Y. Yes - better quality receivers allow you to separate out signals at close frequencies, but a very strong signal next to a very weak signal will drown out it's neighbours.


Toby haynes

He's right, just wrong focus. (1)

Rares Marian (83629) | more than 11 years ago | (#5493916)

Like ever go up to traffic lights on a 2 or 3 or more lane road?

I can tell those lights apart just fine.

What is difficult here is that radio waves are damn hard to pinpoint where they come from since they go in all directions.

But so does light doesn't it?

Man this gives me an idea.

People should all watch "Pump Up the Volume" (-1, Offtopic)

Hao Wu (652581) | more than 11 years ago | (#5493937)

6 times is not enough. This movie screamed this same message 13 years ago. I have been trying to preach since 1990 that Christian Slater was a genius and that society needs to learn the true value of Pirate Radio broadcast. Now maybe some of you will listen to me.
Load More Comments
Slashdot Login

Need an Account?

Forgot your password?

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>