Slashback: Privacy, Spectrum, Location 198
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."
Subscriber Preview (Score:5, Insightful)
Re:Subscriber Preview (Score:2, Offtopic)
-- iCEBaLM
Looks like it's only usable in Europe for now ... (Score:5, Interesting)
(Actually, the existing setup is sweet, but 5cm would be much sweeter.)
Re:Looks like it's only usable in Europe for now . (Score:2, Interesting)
But, as I said ea
Re:Looks like it's only usable in Europe for now . (Score:1, Funny)
Re:Looks like it's only usable in Europe for now . (Score:2)
Re:Looks like it's only usable in Europe for now . (Score:2)
They needed to know precisely where they were GOING TO PUT THE THING, down to the 3cm, IIRC, because they needed to know the materials required, where the international rights/responsibilities changed, what kind of chalky-grey-stuff they were going to be tunnelling through ( use GPS, test sea-floor, move a bit, use GPS, test sea-floor, using triangulation of low-freq, which does penetrate water, or physical connection-to-bottom-of-sea, or whatever ), but they /did/ need precise measurements for the engineer
that's pretty shortsighted (Score:1)
Re:that's pretty shortsighted (Score:2)
i don't know why I was but i was
Re:that's pretty shortsighted (Score:2)
That kind of people is rather harmless when they get drunk, but as soon as they stop they start harassing random people.
Re:Looks like it's only usable in Europe for now . (Score:3, Insightful)
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 [geocaching.com]. 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!
Re:Looks like it's only usable in Europe for now . (Score:2)
James
Re:Looks like it's only usable in Europe for now . (Score:2, Insightful)
Its easy to find uses for high accuracy. (Score:4, Insightful)
Re:Its easy to find uses for high accuracy. (Score:2)
It depends on what you mean by legal. I know people who lay roads by GPS. The receivers they use for benchmarking (the key anchor point for a survey) are static things. A true survey benchmark is a point which has been extremely accurately located. The alternative to benchmarks (which are normally in built up areas) are trig points (also located down to t
Re:Looks like it's only usable in Europe for now . (Score:2, Insightful)
Or you could try flying - in poor viz.
But I agree, you just don't get it.
Re:Looks like it's only usable in Europe for now . (Score:3, Interesting)
Tell me something...why do you think that the Coast Gaurd provides a free differential beacon? Could it be because you need something to make GPS more accurate than it is with Selective Availability? No...that could not be it. If you are sailing around, relying on nothing but a GPS reciever without differential correction to figure out where you are and where you are go
Re:Looks like it's only usable in Europe for now . (Score:2, Informative)
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
Re:Most Important Use for High Accuracy (Score:2)
Re:Most Important Use for High Accuracy (Score:2)
Somehow, I don't think there would be such a free market in nuclear weapons because an attack on America with a North Korean bomb, would probably bring retribution on the producer, not just the user.
Re:Looks like it's only usable in Europe for now . (Score:3, Informative)
Cheers!
Re:Looks like it's only usable in Europe for now . (Score:3, Informative)
(1m = 100cm, for those who find the decimalness of the metric system confusing)
Re:Looks like it's only usable in Europe for now . (Score:2)
Re:Looks like it's only usable in Europe for now . (Score:2)
But yeah, it is sweet...and that's 2 meters (according to the swedish text as oposed to 5 meters in the english text...strange, that)PLUS an estimate of error in the reading (which could be 0.001 mm or 1 meter
Re:Looks like it's only usable in Europe for now . (Score:2, Informative)
So EGNOS works rather like WAAS. [selectzone.com] 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
Re:Looks like it's only usable in Europe for now . (Score:2)
TSA background checks? (Score:5, Insightful)
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.
Re: (Score:3, Insightful)
Re:Doors aren't the answer... (Score:4, Insightful)
This means ... what? (Score:2)
Re:Doors aren't the answer... (Score:2)
Re:Doors aren't the answer... (Score:2)
Especially now that it's looking like the pilots can will be able to carry sidearms in the future.
The copiolet can lock the door, shoot the pilot and have the plane into the ground in under a few seconds.
Hell, you don't even need to do that - If with an Airbus, just stomp on the rudder hard for a few seconds and and the ta
Re:Doors aren't the answer... (Score:2)
Re:Doors aren't the answer... (Score:2)
Re:TSA background checks? (Score:5, Interesting)
The problem is, if you have too much information per datapoint, you start getting false positives.
Think of it like your Bayesian spam filter(God, I LOVE Moz 1.3!)...the longer you train it (the more spam messages you feed it), the better it will be at recognizing the types of messages you give it.
However, if you, say, start feeding it messages from your ex-spouse, it will start homing in on on other stuff. Possibly personal mail, or maybe legal notifications (depending on your situation.
Re:TSA background checks? (Score:2)
I think you hit the nail on the head. But here's the question. To what degree do we want our lives to be governed by actuarial accountants? How much can we trust them? Oh, math is math. But let's not let the word "statistics" get in the way of knowing that judgement calls are involved here.
This is really the BIG QUESTION for us all. How do you discern right from wrong? Correct and incorrect? Probable from improbable?
Think about Slashdot's moderation system for a mome
Re:TSA background checks? (Score:1, Interesting)
2) OBVIOUSLY this is more than just deciding if a single individual is "secure" for a single flight. They are attempting to track individuals that are on "lists". If a suspected terrorist gets on a plane, the FBI now has till that plane lands to decide if they want to pay him(her) a visit or not. If 20 of them all get on planes in one day to one location, well then...
Re:TSA background checks? (Score:1)
just as a side note, the term is actually 'air marshall.' which are some pretty highly trained, butt kickin, federal agents.
Re:TSA background checks? (Score:1)
You need two, that do not know each other. You allow all passengers to carry guns, so you do not have the good guys be known by bypassing security.
So we will have to remove all security.
So, let UAL and American go out of business, serves our goverment right.
Re:TSA background checks? (Score:3, Insightful)
Anyway, people are too paranoid about guns to be comfortable with anyone having a gun onboard, let alone normal passengers.
The main reason people don't want guns on board planes is because having bullets flying around a pressurized cabin is a Known Bad Idea.
Re:TSA background checks? (Score:2)
Re:TSA background checks? (Score:2)
Sure, a slow leak is no problem. But a window or door failure is NOT a slow leak, it is a very rapid depressurization! A friend of mine who is an ATC once decribed a flight attendant training film he once saw. On failure of a window at altitude, the first thing that happens is that everyone sitting in that row disappears out the window (whether they are wearing seatbelts or not). People in surrounding rows who are not wearing seatbelts are also in trouble. Sharp pain
Re:TSA background checks? (Score:3, Interesting)
This makes a certain amount of sense. While many people do end up in credit trouble through no fault of their own
Re:TSA background checks? (Score:3, Insightful)
This makes a certain amount of sense. While many people do end up in credit trouble through no fault of their own (catastrophic medical bills, job loss, etc), very often people who end up with poor credit do so because they are unable to properly manage their fiances. Perhaps this indicates they are also irresponsible in other areas of their life.
It's an awfully big conceptual leap to suggest that people who get into debt and don't pay their bills are also likely to blow up airplanes, now isn't it? Or
Re:TSA background checks? (Score:3, Funny)
Yeah. I had a friend who had that problem. She dumped him in the end...
Re:TSA background checks? (Score:5, Insightful)
Re:TSA background checks? (Score:2)
Missing tech format (Score:5, Funny)
obviously not meant for technical documents; as I only see rtf, not rtfm format.
Re:Missing tech format (Score:2)
Depending on the genre, rtf may be fully descriptive.
[hint [reference.com]]
Bandwidth IS underutilized! (Score:2, Informative)
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
Re:Bandwidth IS underutilized! (Score:3, Informative)
No. Mr. Fourier tells us that an AM signal consists of a range of frequencies. A single, exact frequency is just a pure sine wave, it carries no information. The bandwidth required for AM is just the bandwidth of the signal to be carried.
For a simple example, try adding together two slightly different frequencies. You'l
Data rate is proportional to bandwidth. (Score:5, Informative)
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.
Re:Data rate is proportional to bandwidth. (Score:3, Interesting)
If on the other hand I treat my input as a three dimensional space all of a sudden I can have as many broadcast sources as my ability to process them can tolerate. I can distinguish signal based on directionality, though I have new concerns like multi-pa
Re:Bandwidth IS underutilized! (Score:2)
> can suffice. Assuming the transmitter is truly on the expected
> frequency, all you need is a very narrow bandpass filter.
Wrong. To send a 1KHz signal via AM you need 2KHz of bandwidth under theoretical best case conditions. You need bandwidth to even send Morse. If you are sending CW at a fast enough speed the bandwidth usage actually becomes non-trivial.
If you can't be bothered to actually study some information theory before op
Re:Bandwidth IS underutilized! (Score:1)
Re:Bandwidth IS underutilized! (Score:2)
What is normally called AM has TWO sidebands and thus double the bandwidth of the message.
Jeroen
Re:Bandwidth IS underutilized! (Score:2)
Re:Bandwidth IS underutilized! (Score:5, Funny)
Actually only the RF technician could tell you that. The audiophile would say that AM sounds warmer than FM but only if you're using oxygen-free radio waves. Then they'd start blithering on about how the crystals in their radio were hand-picked by virgins during the winter solstice.
This will ruin my karma, but... (Score:5, Informative)
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.
Re:Bandwidth IS underutilized! (Score:2)
I'm sure Lessig is a very capable lawyer, but I wonder what he would say if I asked him who Nyquist and Fourier are. Could he explain the theories for which they are well known?
TSA Data Gathering (Score:4, Funny)
Therefore urge TSA not to compromise their standards, fellow
Galileo Information (Score:5, Informative)
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.
Re:Galileo Information (Score:5, Interesting)
Really? [slashdot.org] I would beg to differ. I say this under the context that the US taxpayer bought and paid for the GPS, so they have no duty to guarantee any level of service, however some of the arguments against a European GPS system seems to be along the lines of the kid who's taking his ball home and gets angry when he sees that they got their own ball.
Political sidenote: I love how the administration has set up a whole slew of ridiculous propaganda techniques to give the illusion of a dangerous enemy to enrage the public into a president supporting, pollster responding public. Want to invade someone? Up your dubious "threat level" as if you are responding to some overt immediate threat from the deadly enemy. Want to pretend that your enemy is more powerful than they really are? Talk about disrupting GPS, lest they guide their 1960s era Soviet T55s by it... Eurasia...europa...who knows anymore. I am making no comment about the righteousness of this war, but I hope that people can see through these shallow manipulations.
Re:Galileo Information (Score:2)
As far as anyone else using them against us is concerned, we'll just jam the Galileo frequencies in our AO. Americans would be advised not to buy Galileo handsets because we may have to set up jammers for all non-GPS
Re:Galileo Information (Score:2)
Who would have these cruise missiles and use them? Well for starters China if they attack Taiwan and we help defend it. They may not attack us
Re:Galileo Information (Score:2)
Nah, an obviously inferior system, made by people who are jealous of another counrty. It couldn't have anything to do with a part of the world wanting a better s
Re:Galileo Information (Score:2)
get a waas [garmin.com] capable reciver, >3m accuracy.
http://www.garmin.com/aboutGPS/waas.html
Trusting the GW Bush administration (Score:2)
- Fake uranium orders from Niger
- Student's thesis from 12 years ago presented as convincing evidence
- Meaningless wiretappings presented as evidence
TSA vs. FOIA (Score:4, Insightful)
I agree with many Salon responses to rx spectrum (Score:4, Interesting)
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.
Re:I agree with many Salon responses to rx spectru (Score:3, Interesting)
-R
Re:I agree with many Salon responses to rx spectru (Score:2, Insightful)
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
EGNOS != GPS (Score:4, Informative)
EGNOS isn't GPS (Score:5, Informative)
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.
Re:EGNOS isn't GPS (Score:2)
Do ANY of you slashdotters actually know anything about the technology you harp about? Or maybe check the URL's...
Re:EGNOS isn't GPS (Score:2)
Re:EGNOS isn't GPS (Score:1)
Not so bad on Lessing. (Score:3, Informative)
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.
RTFA! (Score:2, Insightful)
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
Re:RTFA! (Score:3, Insightful)
The sheer failure to grasp the concept is so amazing to me. Even the geeks don't get it.
1) Open up some portion of the spectrum to unlicensed transmitters that are limited only by reasonable health concerns and basic mode of operations limits(ie. a few watts effective radiated power in the UHF band with "minimal required output power" type regu
Re:RTFA! (Score:3, Insightful)
WiFi is just the barest beginning and restricted to as you say a propagationally challenged spectrum.
The point that you have missed is that the investment required takes economic incentive that doesn't exist in the current regulatory structure.
You have missed the point that at first "we" want our own band with good propagation that won't interfere with current usage. One good example would be unu
Re:Not so bad on Lessing. (Score:3, Interesting)
Mesh routing schemes break down in highly populated areas - you end up with too many messages needing to be routed by any given node, and the fraction of node bandwidth used for that node's messages dropping like a rock.
Relation is a fun exercise in calcula
Arg! The argument is the point! (Score:2)
That's debatable but 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? What is it that you stand for?
Re:Arg! The argument is the point! (Score:3, Interesting)
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 an
bad policy (Score:2)
So you would have no free long range high power spectrum at all? That's realy short sighted (pun intended), and I'm happy to think that the FCC chairman disagrees with you. 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
Re:bad policy (Score:3, Insightful)
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
as it was in the begining ... (Score:2)
Nonsense! No electronic device, licensed or unlicensed my interfere with federally allocated spectrum. You don't need to yank a license to shut someone down any more
Re:as it was in the begining ... (Score:2)
You miss my point. I'll state it more clearly:
If you have a reason to transmit signals long distances, you can do so cheaply by filling out the appropriate forms and following
Radio Spectrum Underutilized (Score:5, Informative)
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.
Please, do some research once in a while (Score:2, Interesting)
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 incre
Re:Please, do some research once in a while (Score:4, Interesting)
Yes, but not necessarily worse for that. WiFi uses it, as does ethernet for that matter.
Second, TDMA is not infinitely scalable.
True, and false ;-)
True in the sense that sending more bits between two nodes increases the frequency band used, and eventually the band interferes with surrounding bands.
However, if power control, node routing and directional antennas are used the network throughput scales up proportional with the number of users; and TDMA supports this.
Re:Radio Spectrum Underutilized (Score:5, Interesting)
This is why the spectrum is underutilized.
You do realize that as sampling rate goes up, spectrum use (bandwidth) goes up, right?
Any given region of spectrum can only carry so much data, any way you slice it. Power, noise/clutter, and bandwidth combined determine (and limit) data rate.
Missed one Re:Radio Spectrum Underutilized (Score:3, Interesting)
Re:Radio Spectrum Underutilized (Score:2)
CDMA's and CDMA hybrids are being used in favor of the others. Everyone's doing CDMA now.
Checkout http://www.astalavista.com/mobile/wct.shtml [astalavista.com] for a longer list.
not Lessig : it was David Reed / David Weinberger (Score:3, Informative)
The myth of interference
Internet architect David Reed explains how bad science created the broadcast industry.
- - - - - - - - - - - -
By David Weinberger
EGNOS enhances GPS, doesn't replace it (Score:5, Informative)
It's currently in testing, and is expected to be turned on for real soon.
See http://gpsinformation.net/waasgps.htm
Aldenata OGL D20 RPG on the disc & on the web (Score:4, Interesting)
Re:The editors are morons! (Score:2, Offtopic)
how many? (Score:5, Funny)
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.
Re:FP (Score:2)
Since Colombia was mentioned, which kind of coke?