Wireshark · Wireshark-users: Re: [Wireshark-users] Received Signal Strenth - Radiotap - mac80211

[Guy Harris <guy@xxxxxxxxxxxx>]

On May 8, 2009, at 10:30 AM, iodavide@xxxxxxxxx wrote:

> Hi
> I'm using mac80211 for Intel(R) Pro Wireless 3945 in order to capture
> Received Signal Strength from Radiotap headers.
>
> I've created two interface
> (wlan0 and mon0) up to the same Intel card and configured mon0 in  
> monitor-mode.
>
> Radiotap shows SSI Signal (dB) and SSI Noise (dB) but I've some  
> doubts about
> their values.
>
> I read that SSI is related to a not specified dB value of the
> card but I can't find more information about it and about relation  
> between RSSI
> and RSS.
>
> Noise is always 0dB and I read that signal-to-noise ratio (SNR)
> cannot be computed by ``SSI Signal - SSI Noise'' because the noise  
> in Radiotap
> Header usually is captured as the background noise level when no  
> packet is
> transmitted. Thus, the SSI Noise can be interpreted as link quality  
> but cannot
> be used to properly compute the SNR.
>
> Some of you know if I can trust in
> Radiotap SSI Signal dB value?
> I need very reliable SSI values!

You might want to check out the radiotap Wiki:

	http://www.radiotap.org/

or ask on the radiotap mailing list (see the wiki for information).