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Open Spectrum: Free the Airwaves
akb writes: "Most of the RF spectrum in use is licensed for exclusive use. What do we get? Inefficient use through spectrum hoarding, political finagling to abuse the regulatory system to gain competitive advantage and access to the airwaves for only a few players. A good article over at CNET picks up on the example of 802.11b in using spread spectrum technology and unlicensed bands and proposes that model be applied to the rest of the spectrum. For the hardcore check out NYU law professor Yochai Benkler's writings, particularly this article (pdf) and Durga Satapathy's papers for the tech end of things."
Licensed airwaves is a good thing. It ensures that frequencies remain useable and don't obstruct other frequencies. If anyone could broadcast on any frequency, the airwaves would be useless due to noise.
Maybe more work needs to go into reforming the regulation policies instead of developing free-for-alls.
tcd004
Fear the box office of Harry Potter!
While this may seem like an unfair govermental restriction, radio frequencies are not an unlimited resource, like, say, bandwidth, at least not at the present time. There are bands that are available for unrestricted use, just as there are bands that are not usable by just anyone. I do think the regulatory bodies need to keep a better handle on the usage and they need to be able to reclaim bands that are not being put to the best use, though this is quite difficult in practice (for example, digital TV is mandated to be put in place over the next several years, but one string attached to the new frequencies given to existing TV stations was that they give up their current frequencies once they switch over).
Low-power FM was touted to be a great thing for free speech. It was to open up very low-power community FM transmitters, provided (of course) that they didn't interfere with any existing broadcast signal. This would have given voices to community groups, schools, churches, outreach organizations, etc.
There was broad political and popular support for it--but (you know what's coming) the major radio broadcasters lobbied like sons of bitches to have it turned down, using a lame excuse of interference and degradation of signal. Eventually, if I remember correct, LPFM was killed as a last-minute amendment to a bill, an amendment bought by lobbyists no doubt representing Clear Channel Communications and the other bigwigs that bring us the same pap we hear on every FM station in this country.
Don't let big corporations continue to buy up all the bandwidth and hold us hostage with it. We need to get LPFM back on track. Hell, support your local pirate radio station by just listening. You'll be seeing the effect that LPFM should be bringing us and you'll actually hear differing viewpoints, and--dare I say it?--interesting programming.
Karma: Excellent Birds (mostly as a result of listening to Laurie Anderson)
Corporations have been eyeing the amateur radio bands for years. Here are these chunks of bandwidth that are licensed for public use in some very prime locations of the electromagnetic spectrum, all the way from 1.8MHz up to the GHz range. The FCC would just LOVE to auction off the ham radio portions of the spectrum and make millions off of it. Indeed, with waning interest in ham radio, the FCC will be under heavy pressure to free up that spectrum. It'll probably start out with switching them over to "shared use", but once they have their feet in the door, a few years down the road the ham bands will start disappearing. This is just another case of big money having more political influence than the public interest.
If you look at the history of Radio broadcasting, the entire purpose of government regulation of frequency allocations was give interference-free access to the most desirable bands to commercial broadcasters, while forcing non-commercial users who used radio for personal communication or experimentation (the ancestors of modern amateur radio operators) into less desirable frequencies (and then, when those were proven to be useful by the efforts of the amateurs, taking much of that bandwidth away from the public, also).
But now regulation clearly could serve the opposite purpose. After all, if all regulations were eliminated, and everybody were allowed to transmit wherever they like, the big corporate interests (cellphone companies, broadcasters, etc.) would probably be able to effectively claim everything, since they could run higher-power transmitters and more of them than any individual could hope to. If there is to be any kind of non-commercial use of RF, it clearly needs exclusive bandwidth protected by the FCC (as hams, CB users, GPRS/PRS, wireless networks, etc. already have).
Of course regulation as it stands serves the opposite purpose...making as much money as possible auctioning off public spectrum to cellphone companies, etc. But that does not mean that its elimination would solve the problem of the commercialization of public spectrum.
"(Man) tries to live his own life as if he were telling a story. But you have to choose: live or tell." --Sartre
The main problem with the radio spectrum today is that is has been portioned out over many decades. Over that time both needs and technology have changed. I don't think the entire spectrum should be opened up, but it would be smart to reevaluate and reorganize it, leaving more spectrum open for personal use, consolidating the entertainment bands to more efficiently use space with digital technologies like this, and leaving clear bands for scientific and emergency use. And of course, desiging devices so they don't transmit louder than they absolutely have to.
The only real problem with this are legacy devices, namely TV, mobile phones, and especially radio, and their transmission towers. If the transition can be eased for those devices (with adapters or cheap replacements and some gov't subsidy to upgrade transmitters) then I think things would go fine.
---If you can't trust a nerd, who can you trust?
While bandwidth is an oversimplistic way of either looking at things, or regulating them, it is a fact that any communications system can be analyzed (roughly) in terms of bandwidth. And this means that any communications system can interfere with any other communications system if they share frequencies in any sense.
For a real world example of why you can't ignore bandwidth, try running WiFi in a house where you have some 2.4GHz phones. It may work. But sometimes it doesn't - the reason - radio frequency interference. They share the same bandwidth.
Ah, you say... so they don't use good enough systems... or aren't broad-band enough... or something! Not true... there are hard physical limits that no amount of scheming will get around. The rest of this post discusses that in more technical detail.
All signaling systems (INCLUDING Time-Modulated Ultra-Wide-Band)require a separation of signal from noise. Noise is either natural (thermal, atmospheric, solar, etc), incidental (power line leakage, etc) or other radio systems. Regardless of what kind of signaling system is used, it has a limit as to the amount and kind of noise that can be tolerated in any given situation. The other limits described below affect the amount of noise reduction/signal enhancement that is possible.
Limits to processing gain. WiFi and other modern technologies (CDMA cell phones) use spread spectrum to reduce the effects of interference. Unfortunately, this does not eliminate interference. In engineering terms, it is the equivalent of adding gain to the desired signal. The gain is roughly the bandwidth occupied by the transmitted signal divided by the bandwidth required to send the signal without modulation (the baseband bandwidth). This value is measured in decibels, and is typically 20-30 dB, although it can increase. But the higherhe data rate, the lower the processing gain!
The effect of distance - radio signal energy decreases by an inverse square law. This means that a nearby interference source can have a much stronger signal, proportionally, than the desired signal from a farther source. Some numerical examples:
This illustrates that a signalling system, by itself, will not prevent interference - defeating the main argument. Specific factors are:
Imperfections in equipment. Real equipment will not reach theoretical levels of performace.
Limited dynamic range. If you have a 100,000 watt transmitter 3 feet from your receiver, there is a good chance that no matter what its technology, it will not be able to pull out the desired signal. In digital terms, this is the equivalent of running out of bits in your integer! If a number is too big, you either overflow your math, or you scale it down, losing the little bitty number you wanted.
Limited bandwidth - there is a limited amount of bandwidth, useful for a given purpose, at any place and time. This bandwidth, for many purposes, is between 1GHz and 25GHz (although for ionospheric radio, it is only 30 MHz). This means that if someone is generating a strong signal in the bandwidth you are using, there may be no other bandwidth you can jump to.
Intermodulation. Any nonlinearity in the system, including incidental nonlinearities such as a nearby rusty pipe, will cause all the RF signals impinging on them to be mixed, and the mixing products re-radiated. Receivers have inherent nonlinearity, which unfortunately gets worse as the power used by the receiver is reduced.
Leakage. You may have a great receiver, but an interfering transmitter that is close enough may leak through its plastic case and get into an intermediate stage of your receiver.
etc.
Without regulation, some other system must arise to arbitrate needs for radio spectrum, or chaos will result
The only good weather is bad weather.
Bingo!
It's been a number of years since I was involved in this sort of work (so my memory may be a bit fuzzy) but this is an old problem. I was part of a group of engineers that were developing software to predict the problems that proposed FM transmitters might have on instrument landing system receivers. If you look at the frequency spectrum allocations you'd say that there shouldn't be any problem. Different frequency ranges so no problem. Right? Wrong. The landing system receiver receives all the freuqncies that the antenna picks up. Some of those FM transmission frequencies combine in the receiver's front end to generate harmonics that are in the landing system frequency band. Some ILS receivers are better than others at rejecting these but the point is that they're there and they affect the S/N (adversely) and degrade the landing system's performance. Not something you want happening. I recall some of the flight tests where other people were collecting real data to confirm out models. In one case, where the technicians had tapped into the guts of the ILS receiver, they could actually hear the audio from a nearby radio station. Similar concerns about interference of the ILS signals had to do with cable systems. You think your local cable TV provider is ensuring that all the connections on the poles aren't leaking RF energy?
And, if memory serves, lowering the S/N in a spread spectrum has an adverse effect on signal acquisition and tracking. Won't it be fun when everyone in the neighborhood has a spread-spectrum connection to the internet and you find that it performs like a dialup connection.
And I just love law professors who spout views on technology policies without having the necessary technical background. Just about as much as I enjoy professional politicians doing the same thing. There are technical reasons why the spectrum is/was carved up into protected bands. The trouble with politicians (and law professors who probably want to be politicians) is that they're mainly concerned with the economic aspects of spectrum allocation. And, IMHO, that's dangerous.
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