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Sharing the Airwaves: Spread-Spectrum Broadcasting
NaDrew writes "From the SFGate: Hal Plotkin writes about how Spread-Spectrum broadcasting technology could revolutionize the way we listen to the radio, and make it incredibly easy for neo-broadcasters to start their own services. Sadly, he writes, the "often technically inept U.S. Congress has complicated the situation in recent years by shortsightedly instructing the FCC to sell or lease additional bands of spectrum that had been reserved for other uses." Not to mention "the media conglomerates that own most of the nation's TV and radio stations have a vested interest in the status quo and won't easily give up their hammerlock on what, in the end, are public airwaves." A fascinating article that also includes some history of Spread-Spectrum technology (did you know it was patented by Hedy Lamarr?)." A good primer to spread spectrum if you're new to the issue.
(did you know it was patented by Hedy Lamarr?)
That's Hedly!
*** Where are we going? And what's with this handbasket?
So why don't they just fix what we have!?
Wireless-Schmireless
The congress tries to give private enterprice what they want. But it is conress fault! Can't they get the story right just once, for their tame little kittens.
Microsoft - Where would you like to go today, Maybe Jail?
Sure if you are not tuned in, it looks just like noise.
But if people are not careful what will happen is the noise floor is raised higher and higher till it drowns out signals.
Yah that isn't close to happening yet, but the way it's being hyped as if everyone and anyone can broadcast at the same time, it might happen sooner than expected.
Using spread spectrum technology greatly increases bandwidth available. We are figuring this out 75 years after the invention of radio, so wouldn't any one else out there be doing the same thing? Are we wasting time looking for a strong signal from space when a spread spectrum signal would look just like increased static coming from a planet.
Free cell phone tracking
I say we mod her down!
*wave of hand from powerful alien* SETI is evil... you should ban SETI... You don't want to know about other worlds and aliens... Aliens don't exist, and they certainly wouldn't be visiting earth unnanounced to sample the local women... go about your business.
No! You don't say! What an obscure piece of historical trivia. Wherever did you discover that?
I suppose next you're going to bust out with the news that Milton Berle was hung like a horse.
Edith Keeler Must Die
RIAA: What, a new way to distribute music? Kill it quick, before we figure out that it could make us a boatload of money!!
US Military: That's our bandwidth! We need all the spectrum we can get to bomb an Afghan hut!
Steve Case: Did the military say bandwidth?? We should buy that up and meter it.
but I thought that part of the spectrum under consideration had also been set aside for wireless.
I know there was a small flap on something like this back last October, while everyone had their attention elsewhere.
Greed moves on
"It is a greater offense to steal men's labor, than their clothes"
That's what Pulsars are, basically a big galactic GPS / messaging system.
try { do() || do_not(); } catch (JediException err) { yoda(err); }
The possibility of unfettered access to spread-spectrum technology for broadcasting must scares the bejeezus out of the RIAA. So far, their whole arguement against the web-based radio stations has been easy for them to try to enforce it because the pay-per-listen criteria is trackable.
However, if this technology becomes feasible to the average web-caster to broadcast their favorites tunes over the airwaves, then the measurement criteria for tracking who's listening goes out the window, and the RIAA has no power to enforce their rules.
Expect the RIAA to be on the side of the radio station conglomerates on this one.
Rule #1 -- Politics always trumps technology.
If spread-spectrum is allowed to flourish, everyone will have their own home-station, just like the web allowed them to have their own homepage...
Get ready for broadcasts of little Jimmy's first burp, and little Sara's first oboe recital.
For a preview of things to come, review the recent history of mp3.com--high quantity, low quality (followed by corporate buyout?).
I went to the city because I wished to live without deliberation.
The european Digital TV and Radion systems already
use spread spectrum technology (though not
frequency hopping AFAIK) and have been since
they came online years ago. Time for the US to
play catch up (again).
The problem is that Spread Spectrum makes *LESS* effecient use of the spectrum vs frequency division multiplexing. Yes, I am an electrical engineer, and we studied this in class.
The US government sells its services to the highest bidder, while it builds new infrastructure using the lowest bidder. This guarantees low quality in all government services and projects. With regard to the FCC, clearly it is in the hands of the (increasingly few) media corporations.
If those guys at Waco had been broadcasting nationally from within their "compound," do you suppose it might have turned out differently?
You're assuming aliens would be using radio at all and haven't discovered a far better means of
communication. After all, across space almost any form of EM radiation travels as well as radio
waves , they could just as easily be using light.
SS transmissions still use discrete frequencies at any one point in time as they hop around the spectrum. Since SETI monitors wide portions of the spectrum simultaneously, you would actually be able to observe the hopping in real time as the different frequency bands become active with non-random signals. No matter what method of SS transmission you use, as soon as you send non-random data, this will be detectable at any frequency point of the used spectrum. Unless of course your objective is to not be observed and you hide your data in white noise (using steganographic techniques).
So beautiful. So brainy. Sigh ...
Um. Radio is light is electromagnetic radiation. But radio has a benefit, because it is not absorbed by air. Why? Because it's long-wavelength. Basically any gaseous atmosphere is going to be transparent to radio waves, so they are probably using that - probably a liquid environment will also be transparent to it.
You're also wrong that any form of EM radiation travels well in space - dust really sucks, and it preferentially absorbs higher wavelengths (because the dust can absorb them). Radio travels well in space, light does not.
Besides, SETI is looking at an 'intelligent' portion of the spectrum (I believe... they may have switched) - the 21 cm line of hydrogen. We can't look at any large portion of the spectrum - that's really friggin' difficult. So we assume that if they're trying to contact us, they're using an intelligent wavelength.
SETI isn't looking for stray communications, in any case. They're looking for a signal intended for us to notice. If SETI fails, that doesn't mean that there isn't anything out there - it simply means they aren't trying to contact us in the way we think they are, OR they aren't trying to contact us at all.
Great! Now we get every little shit on the planet running his own barage jammer screaming "It's my right!" Some of us actually NEED that low noise floor. It will be very bad when navigation signals go away because people are snarfing any bandwidth they feel like stealing. Existing ultrawideband devices already approved by the FCC measurably raise the noise floor and significantly reduce the SNR of ATC and GPS systems.
I sincerely doubt that an ET would transmit anything we could understand unless they are specifically trying to communicate with young civilizations.
Firstly, compression, by its nature, removes redundancy and order from a signal. Since we would expect an advanced civilization to use near perfect compression to communicate, their signal would look like noise.
Secondly, how long have we had technology that could communicate between the stars? 100 years, tops. We're already discovering that the way we've been doing it is not the best way. 100 years is a blink of an eye in the age of the universe. Very, very few civilizations would be this early in their development right now. So very nearly all civilizations are probably using something that we've never even had the vaguest notion of to communicate. We're still cave men looking for fire signals while everyone else is using compressed spread spectrum radio for communication.
Light is EM radiation too? Gee , thats for letting
me know, I'd never have guessed.
And interstellar dust will absorb wavelengths that
are similar to the grain size which is why some
clouds absord infrared more than visible light
and x-rays go straight through. It depends where
you are. Yes radio travels better in gases but
if these aliens communicate between planets they
could be using anything as I said since interstellar
absorbtion is not relevant on the solar system
(or indeed even local star group) scales.
I have been at the forefront of communications R&D
for 30 years. I can absolutely tell you this is
a load of crap.
Because of the near/far problem, spread spectrum
can't be suitable for broadcasting.
"Radio travels well in space, light does not."
Guess that's why I can't see the stars at night.... oh wait...
*I love sarcasm*
Pardon my FCC frequency allocation ignorance, but how much does Earth radiate at 21cm? (roughly 1.4GHz) There appears to be this presumption in SETI that they're trying to contact us. But other than a couple of bursts, are we trying to contact them? Or have we set the band aside as a quite space for radio astronomy, so on a random sampling nobody would find us?
The living have better things to do than to continue hating the dead.
The FCC isn't interested in increasing the number of radio stations out there. The RIAA doesn't want more broadcasters competing with them. What the government and big business want is as few channels and companies as possible so that they can have tighter and tighter control. For example, if you set up a pirate radio station (ie. you don't pay the FCC's fees), then the FCC will come and shut you down ASAP. This isn't because they're "protecting the airwaves", it's because you aren't paying them. It's been affordable to set up your own FM station for a long time, but the FCC's licenses are extremely high in order to keep normal people off the air.
I'm not sure about the actual numbers, but I think it's in the hundreds of thousands of dollars a year to keep an FM music station on the air.
Travis
"Light" usually implies "electromagnetic radiation". If you meant visible light, you should've said visible light. I was just saying that your terminology was a little ambiguous.
Interstellar absorption is VERY important on local star group scales! Anything smaller than about 1 micron is basically unusable on space scales: it's a power concern. For anything less than 1 micron, you have to transmit MORE power to get the same signal to the receiver. In that case, you'd be an idiot to use that frequency and not the clearer, low power one.
There's a reason we use radio to communicate with satellites and space probes - because it's intelligent, and far easier than visible light (aka lasers). While they MIGHT use lasers, they'd probably only do it for point-to-point connections (planets) and not for spacecraft.
Radio will never go away, not until we find a new medium to broadcast through. And in other civilizations, it won't go away either. It's fundamentally a good region of the frequency spectrum to use.
If you could see radio, you'd see a HELL of a lot more than just stars.
The wording (and context) obviously meant "radio travels better in space than light does" which is true.
It's easy to deal with absorption when you've got a transmitter as powerful as the Sun.
spread spectrum is noisy, tears up vital communications necessary for storm chasing, wipes out or interferes with repeater operations, and is a general nuisance to the Amatuer radio community. We provide many disaster relief services, not to mention the tornado and heavy storm tracking to help the weathermen confirm or deny potential problems shown on doppler and other radar systems. The ARRL and several other ham friendly organizations have been fighting the spread spectrum lobbyers as well as the little leo (low earth orbit) sattelites that infringe on our allocated spectrum. and..... lets not even get started on lowjack.......... Seriously, this is a budding problem that needs to be fixed!!!
I think the #1 thing the Electrical Engineers out there are missing is the impact of data compression algorithms. I'll grant them for now that its less efficient (how about some numbers as to how inefficient it is), but with proper compression/decompression algorithms, the same signals today should be ten times smaller, or, the same frequency can broadcast 10 stations more than it used to. That opens up a lot of space if the "property rights" aspects of transmission were shattered. If a concept like spread is used which fundamentally is less efficient but destroys the monopolies is implemented, I think data compression can bypass any inefficiencies.
Hey, I'm just your average shit and piss factory.
Several years ago a considerable amount of spectrum was sold by North American and European governements for huge prices in the tens of billions of dollars. However, little money exchanged hands. The bidding "down payment" was small, so many sham companies speculated. These huge amounts are just coming off the books. Some of the companies went into backrupcy with these huge debts. The governments also have to write off huge revenues that never materialized.
Therin lies the real problem with spread spectrum vs. conventional broadcasting channels. The limitations of conventional communications techniques is part of what stimulated the development of these more efficient algorithms. And since different groups are confined to their own frequencies, there was little stepping on toes.
But with spread spectrum, there is no pressure to be efficient, because there are no direct limitations on how much you can broadcast. The only problem is background "noise" from other broadcasters, and the easiest way to overcome that is with a more powerful broadcast. The obvious result is an escalation of more people talking louder.
It's like being in a nightclub, where everybody has to scream and repeat themselves to make themselves heard, but communication is near impossible anyway. The only one that can really be heard are the super-amplified guys on stage.
What we need is a more efficient and publicly-accessible use of the airwaves. Deregulating them will give the folks with the big antennas more control, not less.
---If you can't trust a nerd, who can you trust?
As usual, everybody tends to oversimplify spread spectrum and it "magically" works. Nope. Not at all. I wish it were so simple, just like CDMA was supposed to be. Well, because the signal is supposed to look like noise, at least in a CDMA cell phone, you have to effectively manage all the power levels of the users on the system so they don't step on each other. Thats why you have specs like ACPR (Adjacent Channel Power Ratio). Well, power control is a bitch. And you wonder why CDMA cell phones are much larger than their GSM counterparts.
In theory, the real sell on CDMA is spectrum reuse (and security), but thats theory. Its still better than GSM, but like a friend of mine told me once: people only develop complexity to hide mediocrity. And the academics might love the spread spectrum stuff, but its academics... not the people working in the field who have to deal with all the nasty issues academics don't deal with.
I'm not a know-all of spread spectrum issues, and it definitely has some great uses. But I don't think it would be very useful for 1 way communications like radio(unless it needs to be secure - like say...a cruise missile). It really peeves me off when somebody writes about something they no idea about.
Is there anyone who is doing a Spread Spectrum audio or video project?
It would be kind cool if an open Spread Spectrum video standard came out.
Use a 802.11 switch with a 1 watt amp to cover your neighborhood with reruns of Wargames or Commander Taco Eats Michigan.
You say things that offend me and I can deal with it. Can you?
Why wouldn't UWB be used for everything that must be transmitted if it's so great?
Given that:
Their choice is to view it and bomb it from far away by remote control or view it and bomb it close-up-and-personal.
It's still full of terrorists armed with hi-tek antiaircraft missiles when they need to bomb it.
Doing it by remote control needs a lot more bandwidth.
I'd say they have a good case that they DO need all the bandwidth they can get.
Or at least all the bandwidth they currently have MIL-spec remote-sensing and remote-bombing equipment set up to use, so they don't have to go have more designed and built while the terrorists are moving to a new hut and blowing up more skyscrapers.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
This reminds me of the old joke of a drunk looking for his keys under a streetlight. Asked if he lost his keys there, he says "no, but the light's better here."
the "[multiple derisive characterizations deleted] U.S. Congress has ... shortsightedly instructing the FCC to sell ... spectrum that had been reserved for other uses."
"... what, in the end, are public airwaves."
Like the land is all public land, and we're all tennants in government housing projects?
One of the problems with the radio spectrum is that there's a limited amount of it. With the "public airwaves" and "licencing this public trust" model the government's central planners have kept large blocks of spectrum unutilized or underutilized by older technoligies that make less efficient use of it.
One of the most effective methods known to handle the allocation of a scarce resource is a market, where people can OWN pieces of it, subdividiing and trading them as convenient and profitable - which, in the absense of government interference, often ends up with the pieces being used for the most-valuable-to-people purposes.
Like land, there's only so much spectrum. Like land, some uses can "leak out" and pollute neighboring pieces.
The government has decided to try an experiment and switch from the central-planning model to the property/market model for part of the spectrum, to see if that works better.
Of course this gores the oxen of the people who are currently using the spectrum they're selling, so they complain (and often rightly so).
And of course it also gores the oxen of people who have a political leaning toward central-planning, prompting them to spew rhetoric. This set of people apparently includes Hal Plotkin of SFGate.
It's a pity, because the rhetoric obscures anything of interest he might have had to say.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Using spread spectrum technology greatly increases bandwidth available
This just isn't true, any more than weaving around increases the width of a roadway. Sure, it might let you dodge some obstructions, but in the process you become an obstruction to other trafic. The total amount of information that can be carried doesn't increase. Just like in the weaving-around-on-the-road analogy, you have to ask, what would happen if everyone did this? The answer, of course, is that to a good first aproximation all those other SS broadcasters would look like noise to you; so the ambient noise level goes up and the S/N ratio falls, meaning less information gets through.
How much less? well, in an ideal world, if you do everything right you only lose exactly as much as you thought you'd gained. TNSTAAFL.
Each photon you reveive can only tell you so much. You can't beat the uncertanty principle with hand waving.
-- MarkusQ
Spread Spectrum is no magic bullet.
,or.. that other way (how does one describe DSSS?).
Instead of taking a section of spectrum, and, say, dividing it into a hundred equal slices frequency-wise and assigning a slice to each of a hundred users, you take that same spectrum and allow thos ehundred people and divide the spectrum up time-wise,
The point is.. it's not a magic bullet. There is still limited spectrum, and hence, limited bandwidth.
Whether it's common spread spectrum (DSSS, FHSS) or the new UWB thing everyone talks about every six months... it's still limited.
The benefit of spread spectrum over other methods is simply that radios can all be equal, and the 'sharing' can be accomplished algorithmically, rather than by physical frequency boundaries... which should make things more flexbile.
In my humble opinion, frequency hopping and spread
;)
spectrum are not the same.
...says an M.S. in electrical engineering.
I thought it was common knowledge
I think there is too much power and money concentrated over the holding a broadcast spectrum. We have to run ahead of competition and install as many of IPv6 routers as possible, hopefully converting internet, to have multicast.
Multicast will allow *anyone* to have a radiostation, and few even a video station, at flat cost.
Running smashing your head against the wall is not the best way to use yourhead, perhaps, run around the wall, remove supporting beams and it will fall by itself. I think cause of bandwidth to be shared by companies is a lost cause...
The amateur service is intended to be more than merely a backup yacking system to cellphones. It's supposed to encourage experimentation with new systems. Sadly, the current FCC rules don't allow for much useful spread spectrum experimentation by hams, but the truth of the matter is that existing commercial systems could be ported to the amateur frequencies, and do the jobs you mention (emergency communications) far, far better than the 1950s FM technology you're clinging to.
Look at what happened to Packet Radio in the Amateur Service; we built it, they came, but then the FCC issued and enforced inane and archaic content restrictions on the use of packet, and the experimentation died out. The FCC is doing it to us again, all in the name of control.
...-.-
Heheh... thanks for the laugh.
And here I thought the Super Huge Interferometric Telescope poster we posted at that same meeting was the wackiest thing there... :)
[TMB]
2) Inter-Modulation Distortion. This is a general class of problems resulting from non-linearity in amplifiers. It manfests itself on a spread spectrum link as noise --just like the near/far problem. Your options for getting around this problem in a spread spectrum receiver are few: Basically all you can do is build a higher power front end amplifier (consume more power). With narrowband systems you can take advantage of resonant circuits as well.
3) Sequency management. Someone has to coordinate these things somehow. Many are embracing spread spectrum as a way to get rid of the FCC. That's unfortunate. Yes, they're doing their job quite poorly and yes, it's been this way for a long time. That doesn't mean anarchy is better, or that the FCC's mission is irrelevant.
4) Data transmission != spread spectrum. Efficient use of spectrum is laudable. That doesn't mean that you must spread to be efficient, however. There are plenty of very well known modulation techniques which can be used for data transmission. The discussion of data broadcast or point to point data transmission has no bearing on whether one ought to use spread spectrum or not.
5) Making a transition from narrowband communications to spread spectrum communications systems is too expensive, difficult, and impractical to consider. You simply can't change every aircraft radio and air traffic control facility overnight. You can't just shut off all broadcast stations and tell everybody to buy new radios. You'd have a major riot on your hands.
6) Current Broadcast programming sucks. Did adding all those channels to Cable TV improve regular TV programming? Does anyone think XM radio will do good things for FM radio? Get real.
Most of the discussion on spread spectrum right now is more about the disadvatages of narrowband when scaled up and the advantages of spread spectrum on a small scale. However spread spectrum doesn't scale up any better than narrowband communications has. The technologies and limits are still the same. This is not a magic solution. This is merely one method out of several for signal multiplexing.
I can imagine a day when spread spectrum systems will be more common. However it does very little to solve issues such as re-engineering the FCC to be less flaccid and useless, sending high speed data over the airwaves, or how to improve broadcast programming. It's just a technology, it's not a way of doing business.
Nearly fifty percent of all graduates come from the bottom half of the class!
Here's a good overview of the positives and negatives of spread spectrum modulation:
Spread Spectrum Rule Recommendations in Amateur Radio
That makes me curious... if WE aren't sending out directed transmissions to other stars on the 21cm line, why do we think that alien civilizations would be?
"Destroy science and religion. Science would re-emerge exactly the same; but not religion." - Penn Jillette, paraphrased
Ok, so there is a limited amount of Spectrum. Can you explain why, then, the amount of "public" spectrum is FAR FAR LESS than the amount of "public" parks in the United States ??
.. 20 Ghz, we have about 250 Mhz of public space. In other words, only about 1% of this spectrum is publically owned !! The rest has been usurped by your federal government, in the same way that they damned the grand canyon, flooded the HetchHetchee Valley of California, and any number of other federal abominations done for "The good of everyone !!!" (yeah, because the benefactors made huge campaign contributions, that's who is "everyone")... like RCA and Sarnoff ... sheesh.
:
In the 2.4 Ghz band we have 83 Mhz of spectrum.
In the 900 Mhz band we have 26 Mhz of spectrum.
In the 418 Mhz band we have ?? Mhz of spectrum.
In the 5.7 Ghz band we have 125 Mhz of spectrum.
In total, from 0
If we sold LAND the way we sold SPECTRUM, then the sale would be something like this
How much am i bid for all the rivers in america?
How much am i bid for all the valleys in america?
The fact is, cellular technology makes modern spectrum auctions STUPID AND IDIOTIC. Modern spectrum should be sold ONLY WHEN ATTACHED TO A PIECE OF LAND BENEATH IT. To do otherwise is to GROSSLY waste public resources.
I don't think anybody is claiming that this increases the total available bandwidth. What they are claiming is that it makes more efficient use of the available bandwidth by making formerly unusable bandwidth usable.
Of course you didn't look at any of the spectrum above 20GHz? Is
this because of cost/feasibility or just information available to
you? Above 300GHz nothing is licensed. Of course once one reaches
a high enough power level regulations come into play like with lasers
which are in the THz(?) range.
Unfortunately on the lower frequencies they cannot be attached to
the land beneath the expected coverage because of propagation issues
which may cause interference in another cell or plot of land. Once
one reaches a high enough frequency (above the 300GHz range, again
possibly in the THz range) it can be land area specific because of
specific attenuation by the atmosphere. This could then be used
to create thousands/millions of tiny cells with a very large amount
of bandwidth, since bandwidth available ultimately increases with
frequency, that would not cause intereference with each other because
they would be land area specific.
According to a conversation I had with Robert Pepper, entities in Europe owning spectrum can't lease them like in the U.S. With 3G spectrum being so expensive in Europe, UWB could bypass the regulation issues that may take forever to to fix thus jumpstarting the 3G wireless efforts. No wonder why Intel is pushing 3G efforts, to sell more microprocessors.
Because if you're trying to contact other civilizations, the 21 cm line makes sense. It's a scientifically interesting wavelength (Neutral hydrogen has a forbidden line at 21 cm) and the Universe is basically transparent to it.
The reverse argument, that we don't transmit at 21 cm, why should they, which implies if we aren't trying to contact them, why are they trying to contact us, is a valid criticism. I think SETI has basically acknowledged that unless an alien civilization is trying to contact us (or any other civilization), we won't contact them. It's fairly evident that within a few years, "leaking" radiation from Earth will be indistinguishable from noise, so we can expect other civilizations did the same.
This is why if SETI fails, it does not imply there aren't any other civilizations out there. It just implies that none of them are far more gung-ho about contacting other civilizations than we are.