Atheros and how to convert RSSI to dBm

[Miroslav Chlastak]

On 27.5.2010 02:16, Rui Paulo wrote:
> On 26 May 2010, at 23:25, Miroslav Chlastak wrote:
>
>    
>> Hello,
>>
>>   is there a way how to convert RSSI from output of "ifconfig ath0 list sta" to dBm?:
>>
>> [snip]
>>
>> ADDR               AID CHAN RATE RSSI IDLE  TXSEQ  RXSEQ CAPS FLAG
>> 00:4f:62:1d:d8:5d   14    9  11M 18.5    0  15932  22400 ES   A
>>
>> [snip]
>>
>> I my test enviroment I use this function:
>> noise floor + RSSI*2 = signal of client in dBm
>>
>> Then i get the same value as from "tcpdump -n -i ath0 -p -y IEEE802_11_RADIO":
>>
>> [snip]
>>
>> 10:41:04.746395 86402611933us tsft short preamble 58.5 Mb/s -61dB signal -98dB noise antenna 1 [0x00000012] IP 10.0.0.1.2049>  192.168.100.2.123: NTPv3, Client, length 48
>>
>> [snip]
>>
>>
>> Right? Or is this conversion "stupid"? Some better idea?
>>
>> Is there a way how to get noise floor via "ifconfig"? I get it from output of "athstats" :(
>>      
> No, there's no way right now.
>
> Check this: http://lists.freebsd.org/pipermail/freebsd-stable/2006-September/028895.html
>
> Regards,
> --
> Rui Paulo
>
>
>    

But this mail was sent on September 2006 - it's still impossible? :(

And how to do it tcpdump?

tcpdump -n -i ath0 -p -y IEEE802_11_RADIO":

[snip]

10:41:04.746395 86402611933us tsft short preamble 58.5 Mb/s -61dB signal -98dB noise antenna 1 [0x00000012] IP 10.0.0.1.2049>  192.168.100.2.123: NTPv3, Client, length 48

[snip]


Signal -61dB is right signal of my connected wireless client. Tcpdump 
this signal "know", but system (via ifconfig) doesn't?

-- 
Mira Chlastak