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/download/reference/ReferenceTables/Converting%20signal%20strength%20to%20DB.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.