[RFC] libertas: change quality calculation

Michail Bletsas mbletsas at laptop.org
Wed Mar 19 12:13:51 EDT 2008

libertas-dev-bounces at lists.infradead.org wrote on 03/19/2008 11:50:53 AM:

> > RSSI can be derived by adding Noise Floor to SNR value
> I saw that, and it's actually like this coded. However, I was 
> wondering if it is allowed to add "dBm" to "dB". Those are the 
> documented units for "noisefloor" and "SNR", respectively.
Yes, you can add dB to dBm and you will end up with dBm

 0 dBm = 1mW

So the Noise Floor is given as an absolute value (dBm)  and adding the SNR 
to it ( just a ratio in dB) will tell you what the Signal level is (in 

If the noise floor is reported as -86dBm, that means that the received 
noise power is about 2.5pW.
An SNR of 36 means that the received signal power is  -86dbm + 36dB = 
-50dbm ( i.e. 2^12 times higher - 10nW)

Wikipedia has a nice article explaining that: 


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