I believe the s-boxes were provided by the NSA without much comment about them.
You're probably thinking of DES rather than AES with regards NSA provided s-boxes. IIRC said s-boxes in DES were changed by the NSA with no real explanation. Some years later when differential cryptanalysis was discovered in the non-secret world it turned out that the change actually hardened DES against such an attack - so in this case the NSA created a stronger algorithm. See wikipedia.
There's a fair amount that's been removed from this datasheet from the full BCM2835 one - all the parts that aren't accessible from the ARM have been taken out. It wasn't that these bits were secret per se, but that it took effort to produce the edited version.
Spirits haven't been sold in fractions of a gill for some time now. They're sold in multiples of some number of ml, although that number varies between bars - 25ml, 35ml and 40ml all seem to get used.
Largely right, in that the hops provide hardly any sugars for fermentation. I'd like to correct one point though. The hop flowers are removed after the boil, before the yeast is even added. Spent hops are generally sent to agriculture, so the carbon cycle is continued that way.
Because the metre is defined in terms of the distance light travels in some fraction of a second. As such, the speed of light in SI units is always going to be fixed.
Re:One more key point - lack of security
on
Gmail vs Pine
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· Score: 1
Yahoo at least doesn't keep their non-javascript interface hidden; they switch to it dynamically once they detect your browser doesn't support javascript. That's how it should be if it's properly implemented. Plus they have a version of maps which doesn't require javascript either.
Google has both those. If you use a non-supported browser, you get the simple mail interface. Likewise, you'll get the simple map interface if your browser is either not up to it or has script turned off.
they will probably skip HSDPA and go straight to UMTS.
Given that HSDPA is an extension to UMTS, that seems unlikely. Did you mean that they'll launch HSDPA at the same time as UMTS? That would certainly make sense.
I lost the battery cover for my cheap (Geko) GPS receiver. I phoned up Garmin UK to find out where I could buy one, and they sent me one for free - arrived the next day. Excellent.
SPDIF does indeed exist on such a signal. However, the very fact you're sending information is going to mean you don't get a simple clock signal, and you've got to somehow get that clock back with a PLL or somesuch. If your PLL isn't perfect, you're going to get drifts in your recovered clock, hence jitter. Whether you can hear it is another issue....
There's a standard on the way for quarter rate speech over EDGE. This should allow networks to carry close to twice the number of voice calls compared to the (currently popular) half rate.
...requires greater base station density...
WCDMA will need that anyway, so an increase in base station numbers will just happen sooner with EDGE.
Well, that's 8 time slots per frequency. A base station in a busy area will normally have multiple radios in, so it can work on multiple frequencies. It's obviously up to the network operator to install enough base stations with enough radios to support a reasonable data rate.
Being cynical, it's not in the operator's interest to make EDGE too good, at least in Europe, since most of them paid a fortune for W-CDMA (3G) licenses.
Actually, you do get measurable Doppler on phones. The maximum Doppler shift is given by:
velocity * frequency/( c * 3.6 ) (velocity kph, c m/s, frequency Hz - as used for GSM normally)
So, at a speed of 250 kph and a frequency of ~950 MHz (max speed for GSM tests and basic GSM centre downlink frequency) we get a maximum shift of 219 Hz. Not huge, but certainly measureable. The problem comes when you have multiple paths, all with different Doppler shifts - these interfere and give very unpleasant time-variant propagation properties.
The speed issue is nothing to do with handover - you have to be going damn fast to go through a cell quickly enough to cause trouble. The problem is the Doppler shifts and the fading duration.
The Doppler shift means that when you're going fast the radio tuning is no longer correct. This probably wouldn't be a huge problem from a plane, since your Doppler shifts will change quite smoothly (not many hills up there), allowing the phone's frequency control loop to stay locked on.
The timeslot period in GSM is designed so that the propagation conditions at up to 250 kph (for GSM 900) can be assumed to be reasonably stationary across the burst. There's a 26 bit training sequence in the middle of the burst, and the 57 data bits to both sides of this are assumed to have had the same kind of distortions. If the fades are too fast, the error rate goes up.
Re:Actually they aren't using GPS at all
on
Using GPS to Hail Cabs
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· Score: 4, Informative
You can get a more accurate fix on someone's location than just the base station they're using. The base station knows (to within 500m) the distance to your phone for setting time delays. Also, base stations are often in 3 segments.
In addition, base stations can use multiple receiving antennas and triangulate based off the relative phase at each antenna. Positioning to within a few 10s of metres is feasible then. This is becoming compulsory in the US, for the E-911 service.
GSM is likely to have trouble at that speed I think. Certainly the 1800 MHz system would - does anyone know if that's used in France?
WCDMA (the variant of 3G that's being rolled out in Europe) should have much less of a problem with high speeds. Since it's a spread spectrum signal, a fade is much less likely to have an effect, since fades are generally confined to a smaller frequency band.
GPRS traffic should show the same pulse width (~0.58 ms), but with a much more unpredictable pattern. I don't know a huge amount about how GPRS sequences transmission though. It would certainly give a more complex noise in the audio range.
The sound you hear is not related to the carrier frequency. GSM uses time division multiplexing - your phone only transmits ~1/8 of the time. The burst frequency is 217 Hz, and that's what you hear through speakers. Somewhere in your system you've got an accidental antenna that picks up your phone's signal, and "demodulates" it as an AM signal. If you looked at the signal on a 'scope, you'd see something approaching a pulse with a duty cycle of 1/8 and a frequency of 217 Hz.
There's no specific speed limit for GSM. The highest speed test channel is at 250 km/h for GSM900 and 130 km/h for DCS1800/PCS1900. The 250 is (supposedly) based off the speed of a TGV train and the 130 is based off the speed on a UK motorway, since the UK was the first country where DCS1800 was rolled out.
There are two effects that mess you up when you start moving faster - you have less time to do neighbour cell measurement before you need to handover (an in call issue really) and your signal goes to crap due to the fading speed. The maximum test speeds above are about as far as you can go before the signal properties are no longer stationary over the time of a single radio burst.
There is a 35km cell radius limit (which may be what you were thinking of). This comes from the need to adjust transmission time from the mobile to make sure the bursts from all the mobiles arrive at the right time. 35km is the longest distance that can be compensated for. So, the base station is likely to drop your call if you're much further than 35km away.
From the voltage drop you quote (1.7 V) that must be a single colour (probably red?) LED. The 20W flourescent is (I assume) closer to white. If you look at white leds they're far less efficient than the basic red and green varieties. The loss of efficiency puts them below flourescent lighting. I don't have any sources to hand to back this up I'm afraid.
Of course, LEDs can be used to make very cool light enclosures that can't be achieved with other technologies.
If we're talking car lighting (brake or tail lights) then LEDs win out easily, 'cos they've got to be red anyway.
When it really comes down to the wire, are you about providing the public with vital, up to date information, or are you about providing content to generate revenue?
This is probably why the BBC (and probably other public service organisations) seems to cope with load spikes quite well. No adverts, and the low text version is wonderfully lightweight. I suppose the "obligation to serve under high load" would be in the BBC charter if it were being written now.
There's no real way to know if a number if false. There can't be a list of all valid IMEI numbers - it'd be vast, since it would have to include all numbers issued on every GSM network in the world.
Slashdot Mirror
You're probably thinking of DES rather than AES with regards NSA provided s-boxes. IIRC said s-boxes in DES were changed by the NSA with no real explanation. Some years later when differential cryptanalysis was discovered in the non-secret world it turned out that the change actually hardened DES against such an attack - so in this case the NSA created a stronger algorithm. See wikipedia.
There's a fair amount that's been removed from this datasheet from the full BCM2835 one - all the parts that aren't accessible from the ARM have been taken out. It wasn't that these bits were secret per se, but that it took effort to produce the edited version.
I think the word you're looking for is "symbol" rather than "bit". A bit by definition is either 0 or 1.
Spirits haven't been sold in fractions of a gill for some time now. They're sold in multiples of some number of ml, although that number varies between bars - 25ml, 35ml and 40ml all seem to get used.
Largely right, in that the hops provide hardly any sugars for fermentation. I'd like to correct one point though. The hop flowers are removed after the boil, before the yeast is even added. Spent hops are generally sent to agriculture, so the carbon cycle is continued that way.
You can't? Why not?
Because the metre is defined in terms of the distance light travels in some fraction of a second. As such, the speed of light in SI units is always going to be fixed.
Google has both those. If you use a non-supported browser, you get the simple mail interface. Likewise, you'll get the simple map interface if your browser is either not up to it or has script turned off.
they will probably skip HSDPA and go straight to UMTS.
Given that HSDPA is an extension to UMTS, that seems unlikely. Did you mean that they'll launch HSDPA at the same time as UMTS? That would certainly make sense.
I lost the battery cover for my cheap (Geko) GPS receiver. I phoned up Garmin UK to find out where I could buy one, and they sent me one for free - arrived the next day. Excellent.
SPDIF does indeed exist on such a signal. However, the very fact you're sending information is going to mean you don't get a simple clock signal, and you've got to somehow get that clock back with a PLL or somesuch. If your PLL isn't perfect, you're going to get drifts in your recovered clock, hence jitter. Whether you can hear it is another issue....
Why wouldn't you have to ask that in C? The precision of a float or double isn't defined anywhere in the ANSI spec.
I assume this is specified in Java though.
Posting to undo moderation in error of the parent. Sorry about that.
EDGE does not improve voice capacity...
There's a standard on the way for quarter rate speech over EDGE. This should allow networks to carry close to twice the number of voice calls compared to the (currently popular) half rate.
WCDMA will need that anyway, so an increase in base station numbers will just happen sooner with EDGE.
Well, that's 8 time slots per frequency. A base station in a busy area will normally have multiple radios in, so it can work on multiple frequencies. It's obviously up to the network operator to install enough base stations with enough radios to support a reasonable data rate.
Being cynical, it's not in the operator's interest to make EDGE too good, at least in Europe, since most of them paid a fortune for W-CDMA (3G) licenses.
Actually, you do get measurable Doppler on phones. The maximum Doppler shift is given by:
/( c * 3.6 )
velocity * frequency
(velocity kph, c m/s, frequency Hz - as used for GSM normally)
So, at a speed of 250 kph and a frequency of ~950 MHz (max speed for GSM tests and basic GSM centre downlink frequency) we get a maximum shift of 219 Hz. Not huge, but certainly measureable. The problem comes when you have multiple paths, all with different Doppler shifts - these interfere and give very unpleasant time-variant propagation properties.
The speed issue is nothing to do with handover - you have to be going damn fast to go through a cell quickly enough to cause trouble. The problem is the Doppler shifts and the fading duration.
The Doppler shift means that when you're going fast the radio tuning is no longer correct. This probably wouldn't be a huge problem from a plane, since your Doppler shifts will change quite smoothly (not many hills up there), allowing the phone's frequency control loop to stay locked on.
The timeslot period in GSM is designed so that the propagation conditions at up to 250 kph (for GSM 900) can be assumed to be reasonably stationary across the burst. There's a 26 bit training sequence in the middle of the burst, and the 57 data bits to both sides of this are assumed to have had the same kind of distortions. If the fades are too fast, the error rate goes up.
You can get a more accurate fix on someone's location than just the base station they're using. The base station knows (to within 500m) the distance to your phone for setting time delays. Also, base stations are often in 3 segments.
In addition, base stations can use multiple receiving antennas and triangulate based off the relative phase at each antenna. Positioning to within a few 10s of metres is feasible then. This is becoming compulsory in the US, for the E-911 service.
GSM is likely to have trouble at that speed I think. Certainly the 1800 MHz system would - does anyone know if that's used in France?
WCDMA (the variant of 3G that's being rolled out in Europe) should have much less of a problem with high speeds. Since it's a spread spectrum signal, a fade is much less likely to have an effect, since fades are generally confined to a smaller frequency band.
GPRS traffic should show the same pulse width (~0.58 ms), but with a much more unpredictable pattern. I don't know a huge amount about how GPRS sequences transmission though. It would certainly give a more complex noise in the audio range.
The sound you hear is not related to the carrier frequency. GSM uses time division multiplexing - your phone only transmits ~1/8 of the time. The burst frequency is 217 Hz, and that's what you hear through speakers. Somewhere in your system you've got an accidental antenna that picks up your phone's signal, and "demodulates" it as an AM signal. If you looked at the signal on a 'scope, you'd see something approaching a pulse with a duty cycle of 1/8 and a frequency of 217 Hz.
There's no specific speed limit for GSM. The highest speed test channel is at 250 km/h for GSM900 and 130 km/h for DCS1800/PCS1900. The 250 is (supposedly) based off the speed of a TGV train and the 130 is based off the speed on a UK motorway, since the UK was the first country where DCS1800 was rolled out.
There are two effects that mess you up when you start moving faster - you have less time to do neighbour cell measurement before you need to handover (an in call issue really) and your signal goes to crap due to the fading speed. The maximum test speeds above are about as far as you can go before the signal properties are no longer stationary over the time of a single radio burst.
There is a 35km cell radius limit (which may be what you were thinking of). This comes from the need to adjust transmission time from the mobile to make sure the bursts from all the mobiles arrive at the right time. 35km is the longest distance that can be compensated for. So, the base station is likely to drop your call if you're much further than 35km away.
From the voltage drop you quote (1.7 V) that must be a single colour (probably red?) LED. The 20W flourescent is (I assume) closer to white. If you look at white leds they're far less efficient than the basic red and green varieties. The loss of efficiency puts them below flourescent lighting. I don't have any sources to hand to back this up I'm afraid.
Of course, LEDs can be used to make very cool light enclosures that can't be achieved with other technologies.
If we're talking car lighting (brake or tail lights) then LEDs win out easily, 'cos they've got to be red anyway.
When it really comes down to the wire, are you about providing the public with vital, up to date information, or are you about providing content to generate revenue?
This is probably why the BBC (and probably other public service organisations) seems to cope with load spikes quite well. No adverts, and the low text version is wonderfully lightweight. I suppose the "obligation to serve under high load" would be in the BBC charter if it were being written now.
There's no real way to know if a number if false. There can't be a list of all valid IMEI numbers - it'd be vast, since it would have to include all numbers issued on every GSM network in the world.
The biggest technical problem from what I can see would be for IP addrs and routers.
It seems the system gets round this - essentially it's one network, and the IP follows the user around. From the article:
A single IP address can be used in multiple mobile networks, including those based on next-generation standards.
I assume this is handled by Green Packet's SONaccess IP routers. The article is basically about (one of) the first use(s) of this system.