I think the problem is your interpretation of the meaning of "effectively" in that sentence. You take it to mean that it controls access effectively. I believe it means in effect in this context.
An example:
A minefield placed in a canyon floor will effectively render the canyon useless as a means of transit for the enemy.
A minefield placed in a canyon floor will, in effect, render the canyon useless as a means of transit for the enemy.
It so happens that the first form could mean either that it is effective as a means of preventing use, or that the effect of doing so is that use is prevented. The second form only offers the second connotation. But many laws have confusing wordings, with the consequent squabbling over what is really intended by the wording, so nothing new in this one.
Just deleted a phishing email yesterday that copied Paypal's site -- Including Paypal's warning that no Paypal employee will EVER ask you for your password. But please do click on Paypal Security and give it to us there. The URL wasn't even a "domain name" -- it was an IP address:-)
How many of the non-computer savvy know what an IP address is? what a URL is?
Bah! People are too illiterate in computer/web mechanics to be trainable against this blatant fraud. Sorry if I offend, but truth trumps "feels good" any day.
If you read the patent, it does not require GPS - it can use it if available, but it is a "geoposition" technology. GPS is another geoposition technology. They do the same job, in similar ways.
Just another case of somebody calling something "GPS" with no clue what it is they are actually saying.
It was all the rage at the recent 3GSM trade show in Barcelona. I happen to work for a company developing such a product.
They're not ready for primetime today, and even if they were, your cellular operator would have to offer it as part of their service -- you couldn't use one independently. But in the next year or two, they will begin to be a commodity.
Sorry it won't help your problem *today* - but maybe it's a consolation that a product is being developed to meet your PARTICULAR problem directly!
Apparently you have never bought company stock with company issued options.
If you exercise your options, and the "valuation" (aka strike price) at the time of exercise is higher than the option price, the IRS will ding you for income tax on the difference - EVEN IF YOU NEVER SELL THE SHARES. This is "implied income".
To make it even more offensive, say your shares are in a pre-IPO company. You have exercised options to purchase shares that CANNOT BE SOLD - and if you're unlucky, may never be sellable (i.e. the company folds before going public). Nonetheless, the IRS still got their pound of flesh....
I am a regular Slashdot reader, so I get to see all the "scares" that fly by on a daily basis. What amuses me most is the juxtaposition of "global warming" and "oil depletion".
Hey - we are running out of oil in the ground. As demand further outstrips supply, the price of gasoline will climb, and climb, and climb, and... Consumption will naturally fall as supplies fall. How can you consume what you cannot get?
Global warming freaks try to get us all in a tizzy about how we are destroying our planet with - fossil fuel consumption? (which I believe is the single largest factor contributing to greenhouse gases, right?)
The global warming freaks can huff and puff about how we're killing ourselves, but:
a) The world can't just STOP using fossil fuel, without a total collapse of modern civilization
and
b) Like it or not, the world cannot continue to consume fossil fuel at increasing rates, and will in fact have no choice but to reduce consumption, eventually reaching zero.
So does anyone really believe that anything meaningful can be done to curb global warming (with respect to fossil fuel consumption) that isn't already going to happen whether we want it to or not?
What I think we should be serious about is sequestering a percentage of fossil fuel production and make sure it is set aside for those industries that produce secondary products that are not possible without petroleum - e.g. pharmaceuticals, plastics, various advanced materials.
You might be able to build a clean-burning coal-fired automobile, given the NECESSITY of doing so (in the not-so-distant future), but can you imagine the difficulty of doing so with no plastics?
Everyone who actually KNOWS how to handle a gun, knows that the most reliable gun safety is KNOWLEDGE.
But of course, those who do NOT know how to handle a gun love this kind of shit. They just can't wait to make it a felony to own a gun that does NOT prevent you from being able to use it when you need it.
That way, you'll just give up and quit owning guns. Mission accomplished.
I read a story recently of yet another moron shooting a family member while "cleaning a gun." Irrespective of "cleaning," the moron broke the first law of gun safety which is to make sure you NEVER POINT AT ANYTHING YOU DO NOT INTEND TO KILL. That law applies WHETHER OR NOT the gun is loaded, and WHETHER OR NOT the person holding the gun knows if the gun is loaded. Doh!
I seriously believe that accidental killing of another person with a gun should earn an automatic conviction of at least involuntary manslaughter. End of subject. "I didn't know the gun was loaded" means NOTHING to the deceased, and should be null and void as a defense.
I realize that when someone shoots a friend or family member by accident, that person is grief-ridden. But they can be just as grief-ridden behind bars. Their stupidity DEMANDS that they serve time, IMHO.
Gun safety: Know what the hell you're doing, or don't touch the thing.
You can't clone a SIM card. You can come *close* - but you won't be able to copy the Ki (secret key) that is used to authenticate your phone to the GSM network. The Ki file in the SIM is writable (by a person with the administrative password, but not readable -- by ANYONE, including the person who wrote it. The only "reading" of it is done during authentication, when the embedded processor in the SIM (which *can* read it) uses the Ki to calculate a cryptographic hash which it sends to the GSM network. (it's a standard challenge/response type of authentication).
And before you ask, if someone got hold of your SIM and wrote a new Ki value (so that they could make a complete clone of your SIM, given that they know what Ki value they wrote into YOUR SIM), then the network would reject both phones, because the network has a copy of the Ki which was originally in your SIM. Since the perp changed your Ki in order to clone, your phone will no longer be accepted on the network. In other words, a dead giveaway that your SIM was not cloned....
Yes, Apple petitioned the FCC in the early 90's - the so-called "Data-PCS" petition. Spectrum was granted in the 1850-1990 PCS band. But it never got used.
At that time (early 90's), Apple was developing its own proprietary WLAN radio, using frequency hopping. Out of decency, I won't name the company that bought that intellectual property from Apple (it never saw the light of day, AFAIK, from any company).
The Airport radio is unequivocally NOT an Apple initiative. It is very, very close in design to the Prism chipset, which shares a common heritage. The early Airport and Lucent (Orinoco) radios are almost identical. And Lucent (previously AT&T, previously NCR) had a LONG head-start before Apple abandoned frequency hopping and went to DSSS. Having served on the 802.11 committee in its first two years, I can tell you that it was AT&T/NCR that was doing the heavy lifting on DSSS radios. Harris Semiconductor (later Intersil/Globespan/Conexant) also had a lot of good DSSS technology to contribute, a legacy of some of their heavy military spread spectrum investments.
From what I could see, it looked like the real work on 802.11b got done *outside* the committee, with the big boys collaborating and then bringing their converged design to the committee for consideration. The 802.11 committee is filled to overflowing with a lot of "watchers", and a small handful of "workers." In my time on the committee, Apple was almost totally a "watcher", and with respect to DSSS (the basis of 802.11b), TOTALLY and COMPLETELY a "watcher."
And the 10 MHz spectrum your post refers to (i.e. "Data-PCS") never got used by ANYONE. However, a subsequent petition, spearheaded by Apple (or more accurately, by one zealous employee at Apple) *did* result in the creation of the U-NII band (which is where 802.11a operates in the U.S. -- i.e. 5 GHz).
The standards body was inventing 802.11 three years (or more) before Apple took them seriously. The technological underpinnings of 802.11b came from companies like Agere (Lucent/AT&T/NCR), Intersil (Harris), and Digital Ocean (seriously!). Apple had ZERO input into 802.11 during its first two years, and I seriously doubt they had much input in to the "b" version's salient aspects.
I did hear (from a most authoritative source) that Apple got a black eye for having one of its employees propose WEP (and we all know how painful that has been)....
Spurious/misinformed. Apple's WLAN efforts were started in the Newton group, then moved to ATG. For the first several years of the 802.11 committee, Apple pursued their own proprietary WLAN design, while "monitoring" the committee.
Later, (after my departure) I guess they decided that working with a standard wasn't such a bad idea after all...
I would give NCR credit for the first practical 802.11 WLAN (pre 802.11b in fact). NCR, acquired by AT&T, spun off as Lucent, spun off as Agere, trademark (Orinoco) sold to Proxim....
And Harris Semiconductor brought a lot to the table also, with Prism, spun off as Intersil, sold to Globespan Virata, acquired by Conexant...
Flexbeta is running a contest, asking readers to submit articles for publication. Each article published gives the author a chance to win a top-end ATI graphics card. There are several other smaller prizes.
He's just trying to win something. He's certainly not a subject matter expert:)
In July 1992, I was attending an IEEE 802.11 meeting. The company I worked for at the time was making a major series of presentations - "coming out of the closet", as it were, after many months of revealing nothing whatsoever about their WLAN development program.
At one point, the presenter (a colleague of mine) was asked, "Your error correction scheme seems extreme. Do you really think interference in the 2.4 GHz band is going to be that bad?"
My colleague pointed to me (in the audience) and asked me to repeat a remark I had made during a coffee break, where I said, "Well, I've never seen such a thing as a Listen Before Cook microwave oven!"
("Listen Before Talk" was a new phrase coined by one of the committee members to defuse more silliness of arguing over the term "carrier sense", which had a somewhat different meaning to RF engineers as opposed to Ethernet engineers. I found the analogy appropriate -- i.e. "talk":: "cook").
I got a brief chuckle from the committee, but no mention in the meeting minutes, so the event was lost in obscurity.
However, years later, I was searching for a particular kind of patent for a microwave oven invention I had in mind, when I came across:
Patent No. 6,346,692: "Adaptive Microwave Oven". In brief, this patent describes an invention wherein a microwave oven "listens" to the 2.4 GHz band before turning on its magnetron, on a cycle-by-cycle basis, so as to avoid interference with RF communications in the same spectrum. I.E. "Listen Before Cook." The patent was awarded in 2002 to two persons (presumably) employed by Agere Systems, since Agere is the assignee for this patent.
How's that for prior art?
P.S. My "other" microwave oven invention had to do with "listening to the sound of popping corn" to determine when the pop rate was declining, thereby determining the right time to turn off the oven, avoiding the Blackened Redenbacher Syndrome. Sadly, I was beat to that particular punch -- a broader patent existed that covered "auditory feedback" in controlling microwave oven operation.
No, your question and your understanding was valid. The power rating on a power supply states what maximum power the supply can deliver to its load. The actual power consumed *from* the power supply is solely a function of the load attached to it (i.e. the "computer" components it runs). The actual power consumed *from* the wall outlet is the sum of the power consumed by the power supply's load (i.e. the computer components) plus the extra power consumed by the power supply (i.e. the waste) which is directly proportional to the power supply's efficiency.
WarriorPoet42 got it right the second time around - but this did not make your question "stupid."
BY THE WAY: Just because you have a 400W power supply in your PC does NOT mean you are consuming 400W of power from the AC outlet. If you put an older (slower) CPU/mobo with no expansion cards, and run, say, a modern low-power hard drive, etc., the LOAD presented to the 400W power supply will be much lower. Think about it. Small form factor PCs are often built with 150W power supplies. This means that the components NEVER consume more than 150W, and probably seldom if ever hit that peak.
A side-effect of this is that the power supply efficiency does not necessarily always *waste* its ratedpower-minus-(1-minus-efficiency).
(whaatt??) Let's say: R is the power supply's rated power. E is its efficiency expressed as a fraction of 1 (i.e. 90% efficiency is expressed as 0.9)
So, a 400W (R=400) power supply with 80% (E=0.8) efficiency will *waste* 400*(1.0 - 0.8) 80 watts of power. But ONLY if the LOAD is drawing the full 400 watts of power!
Now let's say we have a 400W power supply with 80% efficiency, but the computer components only draw 180W of power. Let's use C to represent the power draw of the computer, so C=180. Now, just substitute C for R and you get:
C*(1-E) = 180*(1.0 - 0.8) = 36W. This is what you are REALLY losing due to power supply inefficiency.
Note: A switching power supply will have some minimal losses even if there is NO load attached to it. These are small compared to the efficiency losses in normal operation, so for practical purposes may be ignored. You could add a constant (say, K) to the equations above to account for this static power loss in the power supply, but K would be small, when compared to C, so has little effect on the math....
Insufficent spectrum with which to develop long enough spreading codes to both achieve the needed low cross-correlation (from one code to any other code), and still maintain 11 Mbits/sec transmission speed. (note: to achieve 11 Mbit/s in 22 MHz of spectrum, 802.11b uses a complex modulation scheme known as CCK - Complementary Code Keying. While I do not fully understand the math behind this, it seems that CCK is unlikely to be amenable to use in creating families of codes with low cross-correlation properties - needed for CDMA).
IS-95 CDMA, I believe, transmits a few kilobits/sec of voice information in a 1.2 MHz bandwidth, using "standard" DSSS. CDMA works because the coding gain with such a huge ratio of data bandwidth to DSSS modulation bandwidth is much larger than that achieved in 802.11 systems.
If you are willing to drop your data rate to, oh, 200 kilobits/sec in the 2.4 GHz band, perhaps 802.11 could be redesigned to accomplish CDMA techniques.
Still, setting up "point-to-point" RF links between individual end user stations would require an enormous amount of computing horsepower (check out a CDMA base station for comparison). And it would not deal with broadcasts, which would still have to be forwarded to an access point - be recoded for each INDIVIDUAL link to each subscriber it serves - and retransmitted N times, where N=number of users served by the access point.
Other systems actually do use techniques somewhat like this, but rather than code division, they use space division (e.g. Vivato, which uses electronic beam steering to establish point-to-point links with each subscriber station).
As I originally stated, and let me re-state - 802.11 is architected on the basis of an "all stations are equal" approach, which makes an uncomfortable fit with a centralized control design. The committee entertained many, many proposals which included centralized control, and rejected them. There are a couple of straightforward reasons: 1) The RF spectrum in which these devices operate is unlicensed and hence "uncontrolled". A base-station centric design would make it so that no station could communicate at all if that base station were experiencing service-blocking interference. The chosen design, though not completely eliminating this failure mode, is more resilient in the face of such issues. Second, the 802.11 MAC is essentially identical for use in an infrastructure mode (i.e. with access points connected to a "distribution medium", typically a wired LAN) and in "ad hoc" mode (where there are only "stations" - no infrastructure at all). Most people forget about "ad hoc" mode, but the committee could not. Their charter required that it be accommodated.
CDMA would not solve this problem. CDMA operates the same as 802.11, in that it is a direct sequence spread spectrum modulation. They are different, though, in that 802.11 devices all use the same spreading code, whereas CDMA uses different spreading codes for each device. CDMA is based upon a "base station subscriber" model, where the base station controls all of the subscriber devices - telling them which codes to use, and managing the interference environment. 802.11 is based on a distributed "no node is greater than any other node" basis. Centralized management of spreading codes would require a total re-architecting of 802.11, and would take it in directions that are inimical to the design objectives of the technology.
P.S. I am a member of the 802.11 committee -- I know of what I speak
Yes, this has happened before. Go to the video store and look for the PBS series "Connections" with James Burke. Episode 1 in that series starts with a dramatization of the 1965 blackout. Started when an overload protection circuit (i.e. breaker) on a Niagara hydroelectric distribution line "did what it was designed to do" (says Burke). The result was a wave of cascading overloads that took out the whole Northeast U.S. power grid.
All this really indicates is that power utilities run their systems with virtually no protective margin. Or, it could be said, demand has outstripped whatever margin they ever *have* had.
The power distribution system could benefit from an "expert system" that watched large regional events to quickly detect (and isolate) rapid sequences of such failures. Not a small task, but straightforward in theory.
WRONG WRONG WRONG!!! (bzzzzt)
on
DOD vs. 802.11b
·
· Score: 5, Informative
There is so much misinformation in both the NY Times article and the discussion here on/., I just have to set the record straight:
1) The DoD is concerned about the 5 GHz U-NII (Unlicensed National Information Infrastructure) band -- which is where 802.11a (not 802.11b) operates. This is a recently opened band.
2) There is no way the DoD can mount a plausible objection to 802.11b, as it operates in the 2.4 GHz ISM (Industrial, Scientific, and Medical) band. The ISM band is the home to microwave ovens, which frequently "leak" 30 times more RF than an 802.11b "intentionally" transmits. There are industrial applications of the 2.4 GHz ISM band that emit KILOWATTS of RF. The 2.4 GHz band is, in essence, the junkyard of the microwave spectrum.
3) The IEEE 802.11 committee is already working on interference mitigation techniques to make 802.11 radios more "friendly" to radar in the 5 GHz band. This is the work of Task Group H. The two major innovations being hammered out in that task group are DFS and TPC (dynamic frequency selection and transmit power control). Both of these are mandated by the European Union's regulatory bodies, in order to open up 5 GHz for 802.11 radios. When ratified, this will lead to an 802.11h radio, which is functionally analogous to 802.11a, but with DFS and TPC. At that time it is likely that 802.11a will wither on the vine, being replaced with 802.11h in the U.S. also. (Note: 802.11a is legal only in the U.S. today. And DoD is basically following the EU's lead in expressing concern about interference to radar. That's what the NYT article meant about Europe being "ahead" in this matter.)
4) While the FCC is in charge of CIVILIAN use of the RF spectrum, they are not the sole arbiter of RF in the United States. The rest of the job is done by the NTIA (National Telecommunications and Information Administration), which is the caretaker for government use of spectrum. For the FCC to open up the 5 GHz spectrum, they needed approval from the NTIA first (which they got).
Summary: "But the times they are a' changin."
Basically the DoD is trying to head off proliferation of 802.11a before it's too late. Of course, the market leading vendors (e.g. Atheros) are none too happy about this, and I don't blame them. Changing the rules after they invest many millions in development of a product on the basis of an expectation of marketability would make even the most accommodating entrepreneur cranky:)
Phased array antennas will provide receiver gain equal to transmitter gain if reception and transmission are on the same frequency (which is the case for 802.11). This is known as signal path reciprocity. In fact, the "Wi-Fi switch" probably first discovers the client when the client sends a "probe" or "associate" request, looking for connectivity. Once the "Wi-Fi switch" hears the client, it has the opportunity to determine the best tuning of the antenna, which will provide the highest signal gain when transmitting back to it.
From an old geezer - The diabetes epidemic is real. I was never a Dew addict, but grew up in the South. Got addicted to a pitcher of sweetened iced tea a day. Now I'm on insulin.
I watched my son drink Dew from the 2-liter bottle. Even though he's thin as a twig, I keep reminding him that it don't mean nuthin. He could end up like me.
You could too.
If you're chuckling as you read this sob story, while finishing off another sugar-rich soda and opening another bag of chips, ask yourself -- "When is it time to change my eating and (non) exercise habits? In ten years? Next year?" The future has a nasty way of becoming the present...
Your speech is as free as a bird, but Slashdot's providing of a forum is not. If you don't care for Slashdot's policy, set up your own website or STFU.
Slashdot Mirror
I think the problem is your interpretation of the meaning of "effectively" in that sentence. You take it to mean that it controls access effectively. I believe it means in effect in this context.
An example:
A minefield placed in a canyon floor will effectively render the canyon useless as a means of transit for the enemy.
A minefield placed in a canyon floor will, in effect, render the canyon useless as a means of transit for the enemy.
It so happens that the first form could mean either that it is effective as a means of preventing use, or that the effect of doing so is that use is prevented. The second form only offers the second connotation. But many laws have confusing wordings, with the consequent squabbling over what is really intended by the wording, so nothing new in this one.
Just deleted a phishing email yesterday that copied Paypal's site -- Including Paypal's warning that no Paypal employee will EVER ask you for your password. But please do click on Paypal Security and give it to us there. The URL wasn't even a "domain name" -- it was an IP address :-)
How many of the non-computer savvy know what an IP address is? what a URL is?
Bah! People are too illiterate in computer/web mechanics to be trainable against this blatant fraud. Sorry if I offend, but truth trumps "feels good" any day.
If you read the patent, it does not require GPS - it can use it if available, but it is a "geoposition" technology. GPS is another geoposition technology. They do the same job, in similar ways.
Just another case of somebody calling something "GPS" with no clue what it is they are actually saying.
I could not agree more. Except that if you are paying north of $100K in taxes, (looking at my paystub), I wonder what company you CEO for...
Learn this new buzzword: Femtocell
It was all the rage at the recent 3GSM trade show in Barcelona. I happen to work for a company developing such a product.
They're not ready for primetime today, and even if they were, your cellular operator would have to offer it as part of their service -- you couldn't use one independently. But in the next year or two, they will begin to be a commodity.
Sorry it won't help your problem *today* - but maybe it's a consolation that a product is being developed to meet your PARTICULAR problem directly!
Apparently you have never bought company stock with company issued options.
If you exercise your options, and the "valuation" (aka strike price) at the time of exercise is higher than the option price, the IRS will ding you for income tax on the difference - EVEN IF YOU NEVER SELL THE SHARES. This is "implied income".
To make it even more offensive, say your shares are in a pre-IPO company. You have exercised options to purchase shares that CANNOT BE SOLD - and if you're unlucky, may never be sellable (i.e. the company folds before going public). Nonetheless, the IRS still got their pound of flesh....
Smoke that.
I am a regular Slashdot reader, so I get to see all the "scares" that fly by on a daily basis. What amuses me most is the juxtaposition of "global warming" and "oil depletion".
Hey - we are running out of oil in the ground. As demand further outstrips supply, the price of gasoline will climb, and climb, and climb, and... Consumption will naturally fall as supplies fall. How can you consume what you cannot get?
Global warming freaks try to get us all in a tizzy about how we are destroying our planet with - fossil fuel consumption? (which I believe is the single largest factor contributing to greenhouse gases, right?)
The global warming freaks can huff and puff about how we're killing ourselves, but:
a) The world can't just STOP using fossil fuel, without a total collapse of modern civilization
and
b) Like it or not, the world cannot continue to consume fossil fuel at increasing rates, and will in fact have no choice but to reduce consumption, eventually reaching zero.
So does anyone really believe that anything meaningful can be done to curb global warming (with respect to fossil fuel consumption) that isn't already going to happen whether we want it to or not?
What I think we should be serious about is sequestering a percentage of fossil fuel production and make sure it is set aside for those industries that produce secondary products that are not possible without petroleum - e.g. pharmaceuticals, plastics, various advanced materials.
You might be able to build a clean-burning coal-fired automobile, given the NECESSITY of doing so (in the not-so-distant future), but can you imagine the difficulty of doing so with no plastics?
whatever....
Everyone who actually KNOWS how to handle a gun, knows that the most reliable gun safety is KNOWLEDGE.
But of course, those who do NOT know how to handle a gun love this kind of shit. They just can't wait to make it a felony to own a gun that does NOT prevent you from being able to use it when you need it.
That way, you'll just give up and quit owning guns. Mission accomplished.
I read a story recently of yet another moron shooting a family member while "cleaning a gun." Irrespective of "cleaning," the moron broke the first law of gun safety which is to make sure you NEVER POINT AT ANYTHING YOU DO NOT INTEND TO KILL. That law applies WHETHER OR NOT the gun is loaded, and WHETHER OR NOT the person holding the gun knows if the gun is loaded. Doh!
I seriously believe that accidental killing of another person with a gun should earn an automatic conviction of at least involuntary manslaughter. End of subject. "I didn't know the gun was loaded" means NOTHING to the deceased, and should be null and void as a defense.
I realize that when someone shoots a friend or family member by accident, that person is grief-ridden. But they can be just as grief-ridden behind bars. Their stupidity DEMANDS that they serve time, IMHO.
Gun safety: Know what the hell you're doing, or don't touch the thing.
You can't clone a SIM card. You can come *close* - but you won't be able to copy the Ki (secret key) that is used to authenticate your phone to the GSM network. The Ki file in the SIM is writable (by a person with the administrative password, but not readable -- by ANYONE, including the person who wrote it. The only "reading" of it is done during authentication, when the embedded processor in the SIM (which *can* read it) uses the Ki to calculate a cryptographic hash which it sends to the GSM network. (it's a standard challenge/response type of authentication).
And before you ask, if someone got hold of your SIM and wrote a new Ki value (so that they could make a complete clone of your SIM, given that they know what Ki value they wrote into YOUR SIM), then the network would reject both phones, because the network has a copy of the Ki which was originally in your SIM. Since the perp changed your Ki in order to clone, your phone will no longer be accepted on the network. In other words, a dead giveaway that your SIM was not cloned....
... expulsions of rectally delivered gaseous matter. They are free to sample most anytime they like.
Yes, Apple petitioned the FCC in the early 90's - the so-called "Data-PCS" petition. Spectrum was granted in the 1850-1990 PCS band. But it never got used.
At that time (early 90's), Apple was developing its own proprietary WLAN radio, using frequency hopping. Out of decency, I won't name the company that bought that intellectual property from Apple (it never saw the light of day, AFAIK, from any company).
The Airport radio is unequivocally NOT an Apple initiative. It is very, very close in design to the Prism chipset, which shares a common heritage. The early Airport and Lucent (Orinoco) radios are almost identical. And Lucent (previously AT&T, previously NCR) had a LONG head-start before Apple abandoned frequency hopping and went to DSSS. Having served on the 802.11 committee in its first two years, I can tell you that it was AT&T/NCR that was doing the heavy lifting on DSSS radios. Harris Semiconductor (later Intersil/Globespan/Conexant) also had a lot of good DSSS technology to contribute, a legacy of some of their heavy military spread spectrum investments.
From what I could see, it looked like the real work on 802.11b got done *outside* the committee, with the big boys collaborating and then bringing their converged design to the committee for consideration. The 802.11 committee is filled to overflowing with a lot of "watchers", and a small handful of "workers." In my time on the committee, Apple was almost totally a "watcher", and with respect to DSSS (the basis of 802.11b), TOTALLY and COMPLETELY a "watcher."
And the 10 MHz spectrum your post refers to (i.e. "Data-PCS") never got used by ANYONE. However, a subsequent petition, spearheaded by Apple (or more accurately, by one zealous employee at Apple) *did* result in the creation of the U-NII band (which is where 802.11a operates in the U.S. -- i.e. 5 GHz).
The standards body was inventing 802.11 three years (or more) before Apple took them seriously. The technological underpinnings of 802.11b came from companies like Agere (Lucent/AT&T/NCR), Intersil (Harris), and Digital Ocean (seriously!). Apple had ZERO input into 802.11 during its first two years, and I seriously doubt they had much input in to the "b" version's salient aspects.
I did hear (from a most authoritative source) that Apple got a black eye for having one of its employees propose WEP (and we all know how painful that has been)....
Spurious/misinformed. Apple's WLAN efforts were started in the Newton group, then moved to ATG. For the first several years of the 802.11 committee, Apple pursued their own proprietary WLAN design, while "monitoring" the committee.
Later, (after my departure) I guess they decided that working with a standard wasn't such a bad idea after all...
I would give NCR credit for the first practical 802.11 WLAN (pre 802.11b in fact). NCR, acquired by AT&T, spun off as Lucent, spun off as Agere, trademark (Orinoco) sold to Proxim....
And Harris Semiconductor brought a lot to the table also, with Prism, spun off as Intersil, sold to Globespan Virata, acquired by Conexant...
Flexbeta is running a contest, asking readers to submit articles for publication. Each article published gives the author a chance to win a top-end ATI graphics card. There are several other smaller prizes.
:)
He's just trying to win something. He's certainly not a subject matter expert
As a previous poster pointed out, this sounds a lot like VMSK - a well debunked modulation scam.
. htm
Here's another: http://www.sec.gov/litigation/litreleases/lr15898
"Never give a sucker an even break." (W.C. Fields)
I can't resist mentioning this silly episode.
:: "cook").
In July 1992, I was attending an IEEE 802.11 meeting. The company I worked for at the time was making a major series of presentations - "coming out of the closet", as it were, after many months of revealing nothing whatsoever about their WLAN development program.
At one point, the presenter (a colleague of mine) was asked, "Your error correction scheme seems extreme. Do you really think interference in the 2.4 GHz band is going to be that bad?"
My colleague pointed to me (in the audience) and asked me to repeat a remark I had made during a coffee break, where I said, "Well, I've never seen such a thing as a Listen Before Cook microwave oven!"
("Listen Before Talk" was a new phrase coined by one of the committee members to defuse more silliness of arguing over the term "carrier sense", which had a somewhat different meaning to RF engineers as opposed to Ethernet engineers. I found the analogy appropriate -- i.e. "talk"
I got a brief chuckle from the committee, but no mention in the meeting minutes, so the event was lost in obscurity.
However, years later, I was searching for a particular kind of patent for a microwave oven invention I had in mind, when I came across:
Patent No. 6,346,692: "Adaptive Microwave Oven". In brief, this patent describes an invention wherein a microwave oven "listens" to the 2.4 GHz band before turning on its magnetron, on a cycle-by-cycle basis, so as to avoid interference with RF communications in the same spectrum. I.E. "Listen Before Cook." The patent was awarded in 2002 to two persons (presumably) employed by Agere Systems, since Agere is the assignee for this patent.
How's that for prior art?
P.S. My "other" microwave oven invention had to do with "listening to the sound of popping corn" to determine when the pop rate was declining, thereby determining the right time to turn off the oven, avoiding the Blackened Redenbacher Syndrome. Sadly, I was beat to that particular punch -- a broader patent existed that covered "auditory feedback" in controlling microwave oven operation.
No, your question and your understanding was valid. The power rating on a power supply states what maximum power the supply can deliver to its load. The actual power consumed *from* the power supply is solely a function of the load attached to it (i.e. the "computer" components it runs). The actual power consumed *from* the wall outlet is the sum of the power consumed by the power supply's load (i.e. the computer components) plus the extra power consumed by the power supply (i.e. the waste) which is directly proportional to the power supply's efficiency.
WarriorPoet42 got it right the second time around - but this did not make your question "stupid."
BY THE WAY: Just because you have a 400W power supply in your PC does NOT mean you are consuming 400W of power from the AC outlet. If you put an older (slower) CPU/mobo with no expansion cards, and run, say, a modern low-power hard drive, etc., the LOAD presented to the 400W power supply will be much lower. Think about it. Small form factor PCs are often built with 150W power supplies. This means that the components NEVER consume more than 150W, and probably seldom if ever hit that peak.
A side-effect of this is that the power supply efficiency does not necessarily always *waste* its ratedpower-minus-(1-minus-efficiency).
(whaatt??) Let's say:
R is the power supply's rated power.
E is its efficiency expressed as a fraction of 1 (i.e. 90% efficiency is expressed as 0.9)
So, a 400W (R=400) power supply with 80% (E=0.8) efficiency will *waste* 400*(1.0 - 0.8) 80 watts of power. But ONLY if the LOAD is drawing the full 400 watts of power!
Now let's say we have a 400W power supply with 80% efficiency, but the computer components only draw 180W of power. Let's use C to represent the power draw of the computer, so C=180. Now, just substitute C for R and you get:
C*(1-E) = 180*(1.0 - 0.8) = 36W. This is what you are REALLY losing due to power supply inefficiency.
Note: A switching power supply will have some minimal losses even if there is NO load attached to it. These are small compared to the efficiency losses in normal operation, so for practical purposes may be ignored. You could add a constant (say, K) to the equations above to account for this static power loss in the power supply, but K would be small, when compared to C, so has little effect on the math....
Insufficent spectrum with which to develop long enough spreading codes to both achieve the needed low cross-correlation (from one code to any other code), and still maintain 11 Mbits/sec transmission speed. (note: to achieve 11 Mbit/s in 22 MHz of spectrum, 802.11b uses a complex modulation scheme known as CCK - Complementary Code Keying. While I do not fully understand the math behind this, it seems that CCK is unlikely to be amenable to use in creating families of codes with low cross-correlation properties - needed for CDMA).
:)
IS-95 CDMA, I believe, transmits a few kilobits/sec of voice information in a 1.2 MHz bandwidth, using "standard" DSSS. CDMA works because the coding gain with such a huge ratio of data bandwidth to DSSS modulation bandwidth is much larger than that achieved in 802.11 systems.
If you are willing to drop your data rate to, oh, 200 kilobits/sec in the 2.4 GHz band, perhaps 802.11 could be redesigned to accomplish CDMA techniques.
Still, setting up "point-to-point" RF links between individual end user stations would require an enormous amount of computing horsepower (check out a CDMA base station for comparison). And it would not deal with broadcasts, which would still have to be forwarded to an access point - be recoded for each INDIVIDUAL link to each subscriber it serves - and retransmitted N times, where N=number of users served by the access point.
Other systems actually do use techniques somewhat like this, but rather than code division, they use space division (e.g. Vivato, which uses electronic beam steering to establish point-to-point links with each subscriber station).
As I originally stated, and let me re-state - 802.11 is architected on the basis of an "all stations are equal" approach, which makes an uncomfortable fit with a centralized control design. The committee entertained many, many proposals which included centralized control, and rejected them. There are a couple of straightforward reasons: 1) The RF spectrum in which these devices operate is unlicensed and hence "uncontrolled". A base-station centric design would make it so that no station could communicate at all if that base station were experiencing service-blocking interference. The chosen design, though not completely eliminating this failure mode, is more resilient in the face of such issues. Second, the 802.11 MAC is essentially identical for use in an infrastructure mode (i.e. with access points connected to a "distribution medium", typically a wired LAN) and in "ad hoc" mode (where there are only "stations" - no infrastructure at all). Most people forget about "ad hoc" mode, but the committee could not. Their charter required that it be accommodated.
Your turn
CDMA would not solve this problem. CDMA operates the same as 802.11, in that it is a direct sequence spread spectrum modulation. They are different, though, in that 802.11 devices all use the same spreading code, whereas CDMA uses different spreading codes for each device. CDMA is based upon a "base station subscriber" model, where the base station controls all of the subscriber devices - telling them which codes to use, and managing the interference environment. 802.11 is based on a distributed "no node is greater than any other node" basis. Centralized management of spreading codes would require a total re-architecting of 802.11, and would take it in directions that are inimical to the design objectives of the technology.
P.S. I am a member of the 802.11 committee -- I know of what I speak
Yes, this has happened before. Go to the video store and look for the PBS series "Connections" with James Burke. Episode 1 in that series starts with a dramatization of the 1965 blackout. Started when an overload protection circuit (i.e. breaker) on a Niagara hydroelectric distribution line "did what it was designed to do" (says Burke). The result was a wave of cascading overloads that took out the whole Northeast U.S. power grid.
All this really indicates is that power utilities run their systems with virtually no protective margin. Or, it could be said, demand has outstripped whatever margin they ever *have* had.
The power distribution system could benefit from an "expert system" that watched large regional events to quickly detect (and isolate) rapid sequences of such failures. Not a small task, but straightforward in theory.
There is so much misinformation in both the NY Times article and the discussion here on /., I just have to set the record straight:
:)
1) The DoD is concerned about the 5 GHz U-NII (Unlicensed National Information Infrastructure) band -- which is where 802.11a (not 802.11b) operates. This is a recently opened band.
2) There is no way the DoD can mount a plausible objection to 802.11b, as it operates in the 2.4 GHz ISM (Industrial, Scientific, and Medical) band. The ISM band is the home to microwave ovens, which frequently "leak" 30 times more RF than an 802.11b "intentionally" transmits. There are industrial applications of the 2.4 GHz ISM band that emit KILOWATTS of RF. The 2.4 GHz band is, in essence, the junkyard of the microwave spectrum.
3) The IEEE 802.11 committee is already working on interference mitigation techniques to make 802.11 radios more "friendly" to radar in the 5 GHz band. This is the work of Task Group H. The two major innovations being hammered out in that task group are DFS and TPC (dynamic frequency selection and transmit power control). Both of these are mandated by the European Union's regulatory bodies, in order to open up 5 GHz for 802.11 radios. When ratified, this will lead to an 802.11h radio, which is functionally analogous to 802.11a, but with DFS and TPC. At that time it is likely that 802.11a will wither on the vine, being replaced with 802.11h in the U.S. also. (Note: 802.11a is legal only in the U.S. today. And DoD is basically following the EU's lead in expressing concern about interference to radar. That's what the NYT article meant about Europe being "ahead" in this matter.)
4) While the FCC is in charge of CIVILIAN use of the RF spectrum, they are not the sole arbiter of RF in the United States. The rest of the job is done by the NTIA (National Telecommunications and Information Administration), which is the caretaker for government use of spectrum. For the FCC to open up the 5 GHz spectrum, they needed approval from the NTIA first (which they got).
Summary: "But the times they are a' changin."
Basically the DoD is trying to head off proliferation of 802.11a before it's too late. Of course, the market leading vendors (e.g. Atheros) are none too happy about this, and I don't blame them. Changing the rules after they invest many millions in development of a product on the basis of an expectation of marketability would make even the most accommodating entrepreneur cranky
Phased array antennas will provide receiver gain equal to transmitter gain if reception and transmission are on the same frequency (which is the case for 802.11). This is known as signal path reciprocity. In fact, the "Wi-Fi switch" probably first discovers the client when the client sends a "probe" or "associate" request, looking for connectivity. Once the "Wi-Fi switch" hears the client, it has the opportunity to determine the best tuning of the antenna, which will provide the highest signal gain when transmitting back to it.
From an old geezer - The diabetes epidemic is real. I was never a Dew addict, but grew up in the South. Got addicted to a pitcher of sweetened iced tea a day. Now I'm on insulin.
I watched my son drink Dew from the 2-liter bottle. Even though he's thin as a twig, I keep reminding him that it don't mean nuthin. He could end up like me.
You could too.
If you're chuckling as you read this sob story, while finishing off another sugar-rich soda and opening another bag of chips, ask yourself -- "When is it time to change my eating and (non) exercise habits? In ten years? Next year?" The future has a nasty way of becoming the present...
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