But when you try to do any calculus on your data in ad-hoc units, you're just going to have to switch back to radians so the math works. Your examples are obvious (2pi)*(size_of_arc/size_of_whole_circle_arc), (2pi)/4, Angels are mythical creatures, but the interior angle you're looking for is (2pi)/6.
Degrees are ingrained, but that doesn't make them consistent with metric. SI should have defined the angle unit such that 2*pi metric_arc_units is a circle. 2*pi centimetric_arc_unit is 100th of a circle and so on.
The standard has been through many amendments and revisions with numerous different physical layer specifications of varying bandwidth. So a fine grained frequency specifier is appropriate to work with all RF phys (there was one IR phy).
Really the question should be why present users with the low level frequency channel number as a choice in a user centric UI? Why not just ask 'low, middle or high' and map it to 1, 6 and 11 for 11b or 11n on 2.4GHz unless they switch on 'advanced' mode.
Set the APs on non-overlapping channels or the same channel. That's what the original poster meant by 1, 6 and 11. 1 - 11 represent frequency slots, but the signal bandwidth is much wider than one slot.
A transmission centered on channel 4 would overlap with a transmission centered on channel 6 for example.
1, 6 and 11 correspond to the low, high and middle frequencies of the 2.4GHz unlicensed band.
I just took a look at Jeff Garzik's notes and it says it has the RdRand extensions, so my expectations are raised a little. Yay. Here's what I do on FC17..
1) Install the RdRand enabled rngd
2) At the command line, type systemctl enable rngd.service
3) In/usr/lib/system/system/rngd.service, change
ExecStart=/usr/local/sbin/rngd –f
To
ExecStart=/usr/local/sbin/rngd –W 4096 –t 1 –f –n 0
To make it not fail, fill the buffer and have a 1 second interval)
4) In/etc/sysctl.conf change kernel random pool refill threshold
to something sensisble
kernel.random.write_wakeup_threshold = 3072
It's odd that rngd is an 'ambitious new feature. It's been around for years and has never been deployed right.
Three things are wrong 1 - It's not on by default 2 - When you turn it on, the command line options are wrong, so it silently fails. 3 - When you fix the command line options, it barely feeds in entropy during boot time because the wakeup threshold in the kernel is set too low, so you get the boot time entropy starvation problem, even though you have an entropy source and rngd running.
Also, if they don't pick up the RdRand extensions to rngd to support Ivy Bridge's fast/secure RNG, then that is a big fail.
Perhaps you can help clear up a debate that has been happening on and off for years.
Is it really necessary to space the channels so far apart? It seems to be a conventional wisdom that flies in the face of the intent of the standard. Sure, the spectrum does overlap somewhat, but isn't the protocol and the air interface designed to handle this situation gracefully?
It sure does in the city where we have multiple APs coming in five-by-five on each and every channel.
Thanks in advance!
The collision avoidance protocol works most efficiently when the devices sharing the spectrum are on the same channel. Having to content with partially overlapping interferes is not going to improve the spectrum usage.
It's part of the standard, and I know, cause I helped write it.
A-HA! There's the culprit!
It's not just him. I was there as well. The difference is that over several years roaming IEEE 802, I managed to remove more text from the specs than I added. This is probably my biggest contribution to society.
At the time of writing the original 802.11 specification, the WDS frames were barely 'designed'. They were just a frame format with an additional address, so you could have the source, destination, transmitter and receiver addresses. There was a vague idea that you could use this for AP to AP communication in some way, but the details were far from worked out. There was no explicitly specified, interoperable description of how to use WDS frames.
It took several years of arguing and rather daft proposals for higher level uses of WDS to get specified so they could be ignored by everyone.
Require that code be run through code analysis and compliance tools that look for the basic things, like function naming, function decomposition, pointer use and other pitfalls.
Then when code reviews come around, you have data instead of arguments and suggestion. "You've got 500 warnings from the code compliance tool. Clean them up before bringing the code to code review."
As far as I can tell, while it doesn't 'have' to push anything out, it does. I have no interest in watching 3D, crap films or special events. I only want to watch good films. There are less good films on at the cinema, even though there appear to be enough good films in circulation to meet my occasional desire to go to the movies. They simply are not being shown, or being shown for 3 milliseconds in the middle of the week while I'm not paying attention.
We went to see no movies this Christmas. There were three evenings where we decided to go and see one, but we found nothing we wanted to see, despite three large multiplexes in the vicinity. Netflix and Amazon streaming filled in at home. I highly recommend 'Rare Exports' for the best Christmas movie ever.
The primary deleterious effect of 3D in my local movie theaters is that the 2 or 3 popular movies at any time now occupy 4 or 6 screens, for the 3D and non 3D versions. This pushes out 2 or 3 other options, so there are fewer options available. This is not a good thing.
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I'd already been a recipient of their 'creative' service with an airline credit card. Never again. I'm free to choose not to do business with them.
There was a cost to switching (mortgage refinance fees) but more than compensated for by switching to a variable rate mortgage.
wamu was sold to chase
Forcing me to switch my mortgage to my credit union, because I don't do business with chase.
Oh, it looks like they did exactly that...
http://www.gordonengland.co.uk/conversion/siderived1.htm
But when you try to do any calculus on your data in ad-hoc units, you're just going to have to switch back to radians so the math works.
Your examples are obvious (2pi)*(size_of_arc/size_of_whole_circle_arc), (2pi)/4, Angels are mythical creatures, but the interior angle you're looking for is (2pi)/6.
Degrees are ingrained, but that doesn't make them consistent with metric. SI should have defined the angle unit such that 2*pi metric_arc_units is a circle. 2*pi centimetric_arc_unit is 100th of a circle and so on.
Agreed. It's less that the video card I'm about to buy and I can pretend that the lego is 'educational' if my wife inquires.
>what of the generations of existing trades that rely on imperial? I.E. Carpentry
50mm x 100mm would be closer to the truth than 2"x4" given the actual dimensions of wood sold in the US.
>So we are stuck using 360 degrees or 2Pi radians.
Radians are fine. Anything else is stupid.
If you kill him, he will become more powerful than you can possibly imagine.
The standard has been through many amendments and revisions with numerous different physical layer specifications of varying bandwidth. So a fine grained frequency specifier is appropriate to work with all RF phys (there was one IR phy).
Really the question should be why present users with the low level frequency channel number as a choice in a user centric UI? Why not just ask 'low, middle or high' and map it to 1, 6 and 11 for 11b or 11n on 2.4GHz unless they switch on 'advanced' mode.
Actually the problem is in three places, which I listed above.
This is true, I hang my head in shame and fully expect to be cast into grammar purgatory on my death. It's still broken in FC17 though.
Set the APs on non-overlapping channels or the same channel. That's what the original poster meant by 1, 6 and 11.
1 - 11 represent frequency slots, but the signal bandwidth is much wider than one slot.
A transmission centered on channel 4 would overlap with a transmission centered on channel 6 for example.
1, 6 and 11 correspond to the low, high and middle frequencies of the 2.4GHz unlicensed band.
I just took a look at Jeff Garzik's notes and it says it has the RdRand extensions, so my expectations are raised a little. Yay. /usr/lib/system/system/rngd.service, change
Here's what I do on FC17..
1) Install the RdRand enabled rngd
2) At the command line, type systemctl enable rngd.service
3) In
ExecStart=/usr/local/sbin/rngd –f
To
ExecStart=/usr/local/sbin/rngd –W 4096 –t 1 –f –n 0
To make it not fail, fill the buffer and have a 1 second interval) /etc/sysctl.conf change kernel random pool refill threshold
4) In
to something sensisble
kernel.random.write_wakeup_threshold = 3072
It's odd that rngd is an 'ambitious new feature. It's been around for years and has never been deployed right.
Three things are wrong
1 - It's not on by default
2 - When you turn it on, the command line options are wrong, so it silently fails.
3 - When you fix the command line options, it barely feeds in entropy during boot time because the wakeup threshold in the kernel is set too low, so you get the boot time entropy starvation problem, even though you have an entropy source and rngd running.
Also, if they don't pick up the RdRand extensions to rngd to support Ivy Bridge's fast/secure RNG, then that is a big fail.
I have low expectations.
Beware the twin evils of the electronic entertainment industry and dairy industry consortiums....
I see you've read this: http://www.amazon.com/Milk-Sulphate-Starvation-Martin-Millar/dp/1593762275
Perhaps you can help clear up a debate that has been happening on and off for years.
Is it really necessary to space the channels so far apart? It seems to be a conventional wisdom that flies in the face of the intent of the standard. Sure, the spectrum does overlap somewhat, but isn't the protocol and the air interface designed to handle this situation gracefully?
It sure does in the city where we have multiple APs coming in five-by-five on each and every channel.
Thanks in advance!
The collision avoidance protocol works most efficiently when the devices sharing the spectrum are on the same channel. Having to content with partially overlapping interferes is not going to improve the spectrum usage.
It's part of the standard, and I know, cause I helped write it.
A-HA! There's the culprit!
It's not just him. I was there as well. The difference is that over several years roaming IEEE 802, I managed to remove more text from the specs than I added. This is probably my biggest contribution to society.
At the time of writing the original 802.11 specification, the WDS frames were barely 'designed'. They were just a frame format with an additional address, so you could have the source, destination, transmitter and receiver addresses. There was a vague idea that you could use this for AP to AP communication in some way, but the details were far from worked out. There was no explicitly specified, interoperable description of how to use WDS frames.
It took several years of arguing and rather daft proposals for higher level uses of WDS to get specified so they could be ignored by everyone.
Require that code be run through code analysis and compliance tools that look for the basic things, like function naming, function decomposition, pointer use and other pitfalls.
Then when code reviews come around, you have data instead of arguments and suggestion. "You've got 500 warnings from the code compliance tool. Clean them up before bringing the code to code review."
No I'm not. Whenever I need to see a bit more text, I rush out and buy a bigger monitor.
I sense a problem that didn't need solving.
Any screen space taken up by this feature is an affront to every coder who's ever had to maximize their window to fit more code in the editor's view.
Sorry, I can't say more that I said in the NIST slides.
As far as I can tell, while it doesn't 'have' to push anything out, it does. I have no interest in watching 3D, crap films or special events. I only want to watch good films. There are less good films on at the cinema, even though there appear to be enough good films in circulation to meet my occasional desire to go to the movies. They simply are not being shown, or being shown for 3 milliseconds in the middle of the week while I'm not paying attention.
We went to see no movies this Christmas. There were three evenings where we decided to go and see one, but we found nothing we wanted to see, despite three large multiplexes in the vicinity. Netflix and Amazon streaming filled in at home. I highly recommend 'Rare Exports' for the best Christmas movie ever.
That is exactly the point. Read it again. Leaking is generally a bad thing.
The sooner it goes away the better.
The primary deleterious effect of 3D in my local movie theaters is that the 2 or 3 popular movies at any time now occupy 4 or 6 screens, for the 3D and non 3D versions. This pushes out 2 or 3 other options, so there are fewer options available. This is not a good thing.