On 2011-06-03 12:36 AM, Luis R. Rodriguez wrote:

On Thu, May 26, 2011 at 5:59 PM, Luis R. Rodriguez[off-list ref]  wrote:

quoted

   What I'd like to do is to affect the ratio to nullify it if the noise
   is very low on the channel. Given that noise is logarithmic we'd have
   to use a logarithmic function as well. Working on that now.

OK I've figured a way to plug the noise into this, I designed the
following function we can use as a factor:

1.1^(x+110)

Wolfram|Alpha boring details of this function:

http://bit.ly/mJNXE9

x,y results of different noise values in dBm, using apcalc:

mcgrof@tux ~ $ calc
C-style arbitrary precision calculator (version 2.12.3.3)
Calc is open software. For license details type:  help copyright
[Type "exit" to exit, or "help" for help.]

; define f(x) = 1.1^(x+110)
f(x) defined

; f(-130)
	~0.14864362802414368640
; f(-120)
	~0.38554328942953174736
; f(-119)
	~0.42409761837248492210
; f(-118)
	~0.46650738020973341431
; f(-117)
	~0.51315811823070675574
; f(-116)
	~0.56447393005377743132
; f(-115)
	~0.62092132305915517445
; f(-114)
	~0.68301345536507069189
; f(-113)
	~0.75131480090157776108
; f(-112)
	~0.82644628099173553719
; f(-111)
	~0.90909090909090909091
; f(-110)
	1
; f(-109)
	1.1
; f(-108)
	1.21
; f(-107)
	1.331

So then, we'd use a frequency for initiating beaconing (AP, Mesh, P2P)
which uses the lowest value from the following computation:

(busy time - tx time) / (active time - tx time) * 1.1^(noise + 110)

The 1.1 factor can be modified more accurately to represent the
exponential factor of how noise should affect interference decisions,
the 110 value here can be modified for any other arbitrary value we
find as representative of a regular noise value from a simple AP on
the frequency we are observing, my assumption here was -110 dBm.

-110 dBm is not a real noise value. It's an unrealistic, ath9k-specific 
value. I have a patch that changes ath9k to make noise and signal 
strength values more realistic, and I'll submit it soon, as soon as I've 
made it a bit more precise.

- Felix