freebsd 8 ifconfig wlan0 get signal strength !

[miniqq]

wlan0 interface created by ath0
how to get a ap's signal strength ?
any command to do that ?
and what does 'S:N' mean give by ifconfig wlan0 list scan ?

 

[SirDice]

and what does 'S:N' mean give by ifconfig wlan0 list scan ?

Signal to Noise ratio.

 

[miniqq]

Signal to Noise ratio.

"Signal to Noise ratio" Does the 'Signal' means "signal strength" OR ...?

 

[SirDice]

"Signal to Noise ratio" Does the 'Signal' means "signal strength" OR ...?

http://en.wikipedia.org/wiki/Signal-to-noise_ratio

 

[fronclynne]

"Signal to Noise ratio" Does the 'Signal' means "signal strength" OR ...?

It's actually not expressed as a ratio in the ifconfig output.

For instance, here

 SSID/MESH ID    BSSID              CHAN RATE   S:N     INT CAPS
REDACTED         00:nn:nn:nn:nn:nn    6   54M -75:-96  100 EP  
redacted         00:nn:nn:nn:nn:nn   11   54M -75:-96  100 EP  
!!!!!!!!!!!      00:nn:nn:nn:nn:nn    1   54M -90:-96  100 EP   WPA
linksys          00:nn:nn:nn:nn:nn    6   54M -88:-96  100 EPS  WPA
redacted         00:nn:nn:nn:nn:nn   11   54M -92:-96  100 EPS 
linksys          00:nn:nn:nn:nn:nn    1   54M -82:-96  100 E    MESHCONF MESHCONF HTCAP WME

(I'm using the top line) S:N is -75:-96 where -96dBm is the background noise and -75dBm is my cruddy signal. More about calculating here:

http://www.swisswireless.org/wlan_calc_en.html

 

[miniqq]

Thank you SirDice & fronclynne .
I got it from
http://www.shakeoffyourweight.com/d...ceTables/Converting signal strength to DB.pdf
.
But I check the source in /usr/ports/net-mgmt/wifimgr
it use (abs(signal) - abs(niose))*4 describing the signal strength.
It's more or less sketchy! I guess.

 

[miniqq]

and I found (abs(signal) - abs(noise))* 4 == RSSI value

 

[miniqq]

and I found (abs(signal) - abs(noise))* 4 == RSSI value

Wrong! corrected
abs(signal) - abs(noise) == RSSI (by integer)

 

[ondra_knezour]

abs(signal) - abs(noise) == RSSI (by integer)

Shouldn't this be abs(noise) - abs(signal)? Consider typical values of noise about -96 dBmW and signal about -70 dBmW. In your formula you get -26, but you are looking for positive value.