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Slashback: Privacy, Spectrum, Location
Sir, you just need to trust us. geekee writes "An article on CNN claims that the proposed passenger-screening system for air travelers is much more innocuous than previously claimed. Now it is claimed that the Transportation Security Administration "will not view credit records, traffic violations or other personal data", according to Admiral James Loy. He also claims records of travel will not be maintained. "Airline reservation agents would provide a traveler's name, address, phone number, date of birth, and travel plans to the TSA, which would then check that information against a variety of commercial databases and an FBI watch list.", according to TSA spokeperson Heather Rosenker."
Thinking of the children means more than hiding their eyes. Jim Tyre writes: "You pointed out that my censorware.net piece ["CIPA Before the Supreme Court"] provided a nifty link to where the official supreme court oral argument transcript would be when available online. It's now available."
What's good for the mercantilists ... wait, no doesn't have the same ring. Lawrence Lessig says that the current radio spectrum is vastly underutilized, and that new technology can extract much more use from it, creating a true radio commons. Zo writes to point out that many Salon readers disagree: "Radio waves, bandwidth, the spectrum. . .Don't we know *anything* for sure?
Sir, these books smell fine ... what's the catch?
silentbozo writes "Avid Slashdotters will remember the Baen Free Library, which puts up free web versions of Baen titles for ANYONE to download and read without having to mess around with encryption and DRM. They went a step further with this experiment last fall with the release of David Weber's War of Honor which had a bunch of novels in html, rtf, doc, palmdoc, and othe formats on CD (bound into the hardcover), which you could copy and give away to anyone. Well, they're at it again. In May, they'll have another CD for those of you who didn't get War of Honor, bound into John Ringo's Hell's Faire.
I got hooked reading John Ringo's books after browsing through my copy of the War of Honor CD... and it's a great way of catching up on the previous books in the series. Hell's Faire looks really good - I personally am looking forward to finding out what happens to the O'Neals as they fight the Posleen on Earth, and to the crew of Bun-Bun... Eat anti-matter Posleen-boy!"
As secure as ... well, you pick. Anthanos writes "pGina [http://pgina.xpasystems.com], a modular authentication framework for Windows, has come a long way since it was last noted on /. nearly a year ago. Since then a full-fledged LDAP plugin, PAM plugin, and chaining have all become part of the feature set. The kicker is the recently released Slashdot plugin, which allows authentication of Windows clients with... yup you guessed it, Slashdot Accounts! XPA Systems has even begun offering services revolving around this GPL product. Seems this may be the solution for people looking to merge authentication of Windows clients with MacOSX, Solaris, and other *nix boxen."
Let's see a handheld that uses both, please ... Mattias Östergren writes "Well aware of the risks with dependency of GPS the European Space Agency (ESA) have developed their own satellite navigation system, EGNOS. EGNOS is more accurate than GPS and the signal also tell you how much it could be off.
The first reference station have just been installed on the roof of the Land Survey in Gävle, Sweden. There is a Swedish press release about it."
You know, previewing a story before it makes the page is really worthless on Slashback when you can't "Read More"
That what was all this school was for... to teach us how to solve our own problems. -- janeowit
(Actually, the existing setup is sweet, but 5cm would be much sweeter.)
Well the section is called slashBACK, meaning followups and information related to previous articles.
If so, how can anyone from Arkansas go anywhere?
But seriously, all this background check BS is too much. Scan people and baggage. Lock the cockpit. Put an 'air cop' on board. What can you do? Not pay for movie headphones? (Credit be damnned, they make you pay in cash.)
Background checks are unnessasary if the airport is secure in the first place.
Ahh...I see. Its cheaper to run my SS/DL #s and invade my privacy than it is to change a door on an airplane. It must be, or airline would have done it a long time ago, because they care about people!^W airplanes.
obviously not meant for technical documents; as I only see rtf, not rtfm format.
Any RF technician or audiophile can tell you that if you want to focus in on a specific frequency or range, you need good/better AC filters.
For AM transmissions, theoretically a single, exact frequency can suffice. Assuming the transmitter is truly on the expected frequency, all you need is a very narrow bandpass filter.
For FM transmissions, it's a little bit trickier. Simply put, the voltage being applied to your speakers (if one ignores all the fancy equilizer circuitry in a radio) is dependent on the exact frequency being transmitted at a given time. The transmitter sends a constant-amplitude signal whose frequency changes with the amplitude of the audio sample.
With FM transmissions, you need bandwidth. You have to be able to discern between the high and low point in the signal, so your radio technology has to at least be capable of discerning between the frequency at the high point, and the frequency at the low point. The broader the bandwidth, and/or the more precise your transmitter and receiver, the more accurate the signal will be on the receiving end.
The point behind all of this is that we're much better at discerning between frequencies than we were fifty years ago, when the FM spectrum allocated. We should be able to fit a passable transmission in a much smaller bandwidth than we do now.
This has interesting possibilities. If you have stations with a high bandwidth (for audiophiles), mixed with low-bandwidth stations (for simple voice broadcasts, you can allocate your bandwidth much more efficiently.
The same concept can apply for digital technologies, too.
What's this Submit thingy do?
Awww. Not so threatening, eh? I was hoping the TSA would go for the whole data collection tamale. Think what happens when the US Gov tries to build a newly designed, big, complex system -- bidding by defense contractors is long, drawn-out, and then it is challenged and redone; the contractor that finally wins takes forever to complete it, if ever; if the contractor actually manages to build something, it's completely unusable; in disgust, the govt throws it away and starts the cycle again with more bidding. Just ask the FAA, LOL!
/.ers. That way we'll have no data collection, ever.
Therefore urge TSA not to compromise their standards, fellow
English -- gotta love it! / The engineers refuse to refuse the rocket until the refuse is removed from the launch pad.
...secure, locked cockpit doors aren't going to look like such a good idea the first time some terrorist type spends years training to be a pilot and is sitting *behind* that door.
Cheers
-b
If I wanted a sig I would have filled in that stupid box.
At any rate, there's a lot of good Galileo information on the web. Here are some links:
These links are from a file I have of info on Galileo. Hopefully no link rot.
IIRC, government-held info that's supposed to be purged from someone's record has a nasty tendency to stick around (whether by accident or by design). I wonder how hard the TSA and the DHS will make it to submit a FOIA request to verify that this information *is* being purged after each flight.
As an RF/Microwave Engineer, I deal with the problems with RF interference daily. A recent article I saw online lauded the participation of ham radio operators in disaster situations including the World Trade Center relief operation.
Imagine thousands of devices and gadgets emitting radiation on random frequencies, and you can see the problems that might arise in critical communication situations. The background noise level at HF frequencies is already very bad due to consumer devices. I would hate to see it get any worse.
EGNOS is the European answer to WAAS, folks, not GPS.
EGNOS is only available in Europe at the moment because it's only being transmitted from one geostationary satellite that's sitting over Europe. WAAS is currently being transmitted from two geostationary satellites over the Americas.
Neither system is what I'd call new - they've been in a sort of beta test phase for years, and there are already consumer receivers on the market that support EGNOS/WAAS.
Perhaps I just don't get it, but I am having trouble figuring out why anyone (outside of a small subset of the population) would need accuracy less than 50 feet or so. I suspect people that really need accuracy greater than this currently have the tools to achieve such accuracy. It's not like most people are letting their GPS device drive their vehicles or something. Plus for people that need better accuracy, there are means by which to get it, depending on how much you want to spend.
But, as I said earlier, perhaps I just don't get it....
People are more violently opposed to fur than leather
because it's safer to harass rich women than motorcycle gangs
For AM transmissions, theoretically a single, exact frequency can suffice. Assuming the transmitter is truly on the expected frequency, all you need is a very narrow bandpass filter.
If you try to send an AM signal across a 1 Hz band, you will get a 1 Hz bandwidth signal out at the other end. Not very useful if you were trying to play music. Definitely not useful if you were trying to transmit data.
The number people are interest in is data rate. Data rate is bandwidth times the log to base 2 of the number of levels you can distinguish. Different encoding schemes (FM, wide-spectrum coding) express the relation differently, but the same limit applies.
You can narrow the bandwidth, but as soon as you hit noise limits, your data rate starts going down too. *That's* the problem. Low-noise electronics doesn't help if the noise is from other users.
The only way to avoid user clutter is to switch to something other than a broadcast system, which involves either large dishes or short-range transceivers and hubs connected to a _wired_ backbone.
I believe the claimed accuracy is 5 meters.
Cheers!
Where does that 5cm number come from? It says 2m in the swedish text, and 5m in the english text..?
(1m = 100cm, for those who find the decimalness of the metric system confusing)
It would be much more productive if Reed and other "architects of the Internet" spend time finding solutions to EM pollution caused by switching power supplies and digital systems, rather than proposing ways to make problems worse in areas they clearly don't understand.
This comment follows a rant which ironically ignores most modern radio breaktrhoughs: packet routing and frequency hopping on low power devices to create a network with far greater bandwith than a single transmitter per frequency set up that's current. Instead, he focus on ancient details of antenae size and signal propagation. It's amazing that someone could ignore the demonstrated reality of Alohanet and 802.11B meshworks and then call others ignorant.
Then again a simple search pulls up stuff about Tom Rauch. Is this guy a profesional slammer or what?
Well, fine, he knows his tubes and amps, IF the first person linked to above is not correct in assesing him as a whore. You have to be suspicious of people who rant so.
All of the other letters on that page supported Lessing's conclusion that the broadcast spectrum is poorly allocated and mostly empty. There was that one bizare and false analogy to a pinhole cameras with no pinhole. I've never seen a pinhole radio, it must be intersting.
DMCA, Hollings, Palladium. What might have sounded like paranoia is now common sense.
how many lives per gallon are you getting america?
That's a very good question. How many lives should we be getting? If it's under ten, I've got no problem with that. Anything over that would make me consider downgrading my Lincoln Aviator to something more sensible like a Ford Excursion.
Four or five lives for me to drive down to the grocery store? Hell of a deal, I say! What do you expect me to do, walk?!?!?
I'm sure if these people in Arabia or whatever the hell it is could feel the supple leather of my seats or the raw power of America's finest sport utility vehicle, they'd be more than happy to trade their lives so I could ride in style. I don't understand those people anyway, living in huts and raising camels. I don't see how their poor real-estate buying choices are my problem. If they don't like it there, they can just move, can't they? Not move here, of course, this country is far too crowded and our resources are too limited. But isn't there some country where they could go and buy a nice villa? Surely there must be.
It's not like we didn't tell them, "leave the city, we're going to be dropping some bombs." They had plenty of warning! I just don't understand what they're complaining about.
It's not like most people are letting their GPS device drive their vehicles or something.
No, but they let Microsoft Streets do it for them. And it's really annoying when your car symbol jumps from one street to a parallel one.
Anyway, check out Geocaching. It's awesome, but an accurate GPS helps out a lot. You go around finding boxes of prizes with only a GPS coordinate and a couple of clues. It's great for excercise, and it's fun! You hear me, geeks? FUN EXCERCISE!
What's this Submit thingy do?
Currently there are three ways to partition the available spectrum:
FDMA (Frequency Division Multiple Access): The standard technique of TX/RX on different frequencies (or colors if you read the analogy on Slashdot a few days ago). Ho-hum, it's the first thing I would have tried too. Our predominate and most wasteful technique.
CDMA (Code Division Multiple Access): A set of spread-spectrum techniques that use a sort of RF kung-fu to manipulate previously considered undesirable properties of radio waves to advantage. On the coolness factor the engineers that designed these technologies should be in the nonexistant Engineering Hall of Fame. The scuttlebut is that some of this technology was invented by Qualcomm as early as WWII but was highly classified until recently, so Qualcomm still holds most of the patents to this today.
TDMA (Time division multiple access): This involves standard unix-like time splicing, except using radio signals. GSM works like this by partitioning groups of eight consecutive time slots to form a TDMA frame with a duration of 4.615 ms. Each transmitter (cell-phone) in the area gets one burst period (a slot) of duration 15/26 ms (approx. 0.577 ms) to use the channel. This is an immensely powerful technique, and one that is infinitely scalable. It's only limitation is the speed of our electronics, which can and should maintain it's exponential speed curve. This is why the spectrum is underutilized.
it's :
The myth of interference
Internet architect David Reed explains how bad science created the broadcast industry.
- - - - - - - - - - - -
By David Weinberger
There are places where the networks are not touching,and there are places where they are-Boeing's Lori Gunter
You misunderstand the arguement. The frequencies are far from random, and the equipment is designed to expect frequency hoping, amongst other things. That is the most basic step toward a better utilized spectrum, one that has been used since WWII.
-R
You've obviously never tried to find a geocache hidden in a field of boulders and rocks. Look for an hour or so and you get pretty mad.
EGNOS is the European version of WAAS, a system that enhances GPS accuracy by providing differential corrections (like DGPS, only from a satellite instead of a ground-based transmitter).
It's currently in testing, and is expected to be turned on for real soon.
See http://gpsinformation.net/waasgps.htm
One noteworthy thing about the CD-ROM that's not mentioned in that orientation is that it will include a (partly-)OGL D20 RPG based on the Aldenata books, which you can currently find hosted in rich text form at Alldenata.net under the link marked "rules." (I'm not entirely sure why the spelling of the aliens changed between the first few books ("Alldenata") and the most recent one ("Aldenata"); nobody on the John Ringo Baen Bar group seems to want to talk about it.)
Editor Emeritus and Senior Writer, TeleRead.org
Also frequency hopping spread spectrum was designed to stop jamming since it's hard to broadcast across a very wide spectrum at high power. But give one of these transmitters to everyone in a metropolitan area and watch the mayhem insue. All cell networks use spread spectrum technology, and there are still subscriber limits.
The reply of Rauch was completely accurate. I'd like to see you send any signifcant power at modern radio or TV frequencies without a giant antenna. Mesh networking may be nice, but what happens when you're alone on a back road with your
Let the people who have EE and not CS degrees build the radios. Real life is not digital.
While the subset of people that need high accuracy maybe small, that doesn't mean they're not economically significant. Just making surveying easier would be a hugh cost savings. Think of all the things that are surveyed. The lot your home sits on. The street in front of your house. In oil exploration, there's surveying of seimic sensors. The list goes on and on.
Where the hell do you get your info?
Most modern radios (I mean those in cell phones/WiLan) use a combination of these techniques. Furthermore you have a serious lack of understanding of the technologies you mentioned.
First, CDMA is considered on the forefront of spread spectrum technologies today, TDMA is old-hat. Second, TDMA is not infinitely scalable. If you have shorter time slices, you increase the bandwidth. There is no free lunch, you have to use bandwidth to send data. You can sometimes increase efficiency, but nothing is infinitely scalable.
Really, put the infinitely scalable TDMA system in the engineering hall of fame with the perpetual motion machine and brickwall filter.
The statement about AM is flat-out wrong.
Do the fscking trig.
Consider a sinewave modulating signal. Let c be the carrier frequency, and m be the modulating frequency. Recall that cos(u) varies between -1 and 1. We want the modulating control signal to vary between 0 and 1, so the modulator is 1/2(1+cos(m)).
We use cos(u) because it simplifies the key trick in the derivation. OBVIOUSLY, it is just a phase shift to do it in sin(u).
Then the fundamental equation of AM is
f(t) = 1/2(1+cos(m))cos(c) (1)
= (1/2 + 1/2cos(m))cos(c)
= 1/2 cos(c) + 1/2 cos(m)cos(c) (2)
The first term is the carrier wave. Observe that it carries half of the input power and NONE of the modulating signal.
Recall from basic trig
cos(u+v) = cos(u)cos(v) - sin(u)sin(v)
and
cos(u-v) = cos(u)cos(v) + sin(u)sin(v)
Then
cos(u+v) + cos(u-v) =
(cos(u)cos(v) + cos(u)cos(v)) +
(sin(u)sin(v) - sin(u)sin(v))
which simplifies to
cos(u+v) + cos(u-v) = 2 cos(u)cos(v)
Or
cos(u)cos(v) = 1/2(cos(u+v)+cos(u-v))
That looks familiar. Recall (2)
f(t) = 1/2 cos(c) + 1/2 cos(m)cos(c) (2)
Substituting
f(t) = 1/2 cos(c) + 1/2(1/2(cos(m+c)+cos(m-c)))
= 1/2 cos(c) + 1/4 (cos(m+c) + cos(m-c))
And there you have it. You have a carrier wave, and you have two sidebands, and the bandwidth of the whole thing is twice the modulating frequency.
The next step is to observe that the Fourier theorem applies and is carried straight through, and so ANY modulating signal will generate two sidebands, one above and one below the carrier wave, each preserving the harmonic content of the modulating signal, but with one reversed in frequencies.
Your explanation of FM is just as bad. I'm not going to do the derivation, because it is MUCH messier, involving very ugly Bessel functions, and I don't have my textbook handy.
You can reduce the bandwidth of an FM signal, but you lose fidelity.
You can reduce the bandwidth of an AM signal by band-limiting the input audio information, which is routinely done in voice communications gear: the full audio spectrum goes up to NOMINALLY 20 kHz, but the useful speech formants are pretty much all found between 300 Hz and 3 kHz.
You can suppress the AM carrier wave, and you can suppress one of the sidebands. This is also routinely done, in single sideband communications. This involves loss of redundancy and loss of easy tuning, which in turn makes careful tuning much more important: any mistuning comes out as distortion.
There's also have a sort of space division multiplexing- i.e. using directional antennas. That concept is used on TV aerials among others.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"So EGNOS works rather like WAAS. They provide corrections to the GPS signal. How do they obtain the corrections? A network of fixed ground stations with precisely known positions receives GPS, compares the GPS position with the actual position, and computes GPS corrections. Those corrections are beamed up to a satellite, which beams them back down for appropriately configured GPS receivers to make use of. The GPS receiver looks at the corrections for nearby ground stations, and linearly interpolates a correction for its location.
The accuracy of such a correction depends on the density of ground stations (the nearer you are to a ground station, the more applicable its correction signal). The coverage area is wherever the administrators decide to sprinkle their ground stations. Presumably EGNOS will limit their ground stations to Europe, but in principle they could put them everywhere. So it looks like EGNOS is just WAAS for Europe.
You've never been sailing, have you? In the fog ... Try it some time - you might suddenly get to appreciate the advantages of accuracy.
Or you could try flying - in poor viz.
But I agree, you just don't get it.
"Cats like plain crisps"
Next time you are in your airplane flying around in poor visibility, you might notice that there are numerous round gauges and dials there in front of you in the cockpit. Theses are called instruments, and by reading them correctly, you will be able to figure out where you are going. In visibilty that is so poor that you cannot look out and see the world around you, you will be operating under instrument flight rules, or IFR. Hope you are certified for IFR flight. It is interesting to note that IFR has existed much longer than GPS, and in fact a GPS reciever is not one of the instruments that your craft must posess in order to operate under IFR.
My whole point is that people that need accuracy have it now, and will continue to have it. Its just not free.
Perhaps not, but in this regard, we are equals.
People are more violently opposed to fur than leather
because it's safer to harass rich women than motorcycle gangs
Er - they don't - I'm in Australia. The diferential service is pretty limited. Lots of coast, not many people.
People got to places before GPS. Even before sextants. And compasses. And charts. But they died a lot doing it.
I like GPS - its universal availablity and accuracy is a boon to all. Better accuracy would be good.
I obviously fit into the group you don't believe in, the ones who would like better accuracy and don't currently have access to it. But I'd have thought that was me and all the other non-wealthy offshore sailors in the world. Why should accuracy be restricted to the rich, as you appear to suggest, when a system available to all can offer it?
I reckon something else is going on here. Could it be you can't stand the idea of those dashed Europeans (especially France) having a more accurate system than the good old USA?
"Cats like plain crisps"
think about what you are saying. If only a fraction of the currently restricted bandwith were so well utilized! As it is, you hear silence. Which is preferable? The possibility of a clog or enforced silence and frustration?
Clogging is a certainty without imposed limits; people are greedy that way. Removing band restrictions just guarantees that *all* parts of the spectrum are clogged.
Band restriction is a quality of service issue - if you want to be able to use your cell phone, or to put up an antenna and hear music from your favourite radio station, there must be a guarantee that the person next door isn't cluttering up that section of the spectrum for you. This is especially true for emergency services, and for bands that interfere with important equipment (radio beacons at airports come to mind).
What is it that you stand for?
Wired backbones. All the bandwidth you can eat, and much less contention for it. Limit wireless to short range, and put hubs everywhere. Problem solved (for urban areas; rural areas are an entirely different problem with different constraints).
Limit wireless to short range, and put hubs everywhere. Problem solved (for urban areas; rural areas are an entirely different problem with different constraints).
So you would have no free long range high power spectrum at all?
There would be a few bands open for hobbyists, just like there are now. Want to build a 1 kW transmitter? Go ahead - just get your ham license first. Decide you're not going to play nicely in the community? Your license gets revoked.
Without management, anything longer than short-range will cause too many people to step on each others' toes.
The cost of all that badwith you want would be considerably less if more spectrum was given over to 802.11B type freedom. The equipment is cheap enough that people would build the infrastructure and run it as a free public service.
The free public service would then start charging a modest fee to support its overhead, and then the core of people running it would slowly drift to the dark side as bureaucracy started fossilizing, and you'd end up with something indistinguishable from the bandwidth providers we currently have.
Do you think that Cthulhu came to earth and decided to found UUNet to torment the mortals? Large-scale utility providers _naturally_ evolve to become this way!
If you want cheaper bandwidth, start a letter-writing campaign to get better government regulation of the industry. It's a utility, just like phone and power and water and so forth. Manage it like one.