What is RSSI , SNR and technical specification value in dbm

Hi,
I am little bit confused about RSSI concept and SNR , Signal strength.
One more thing that , what is technical specification of signal strength and SNR and RSSI for 802.11 a,b,g and n
Because as far as application concern , this values get changed eq. voice , video
I need to get the values according to application.

Hi,
RSSI means Receiver Signal Strength Indicator. It's the strength of the signal as perceived as received by the client. It does not have a precise unit of measurement. On client softwares, it's usually a percentage (that has no real meaning). WLC and APs usually show in dbm.
SNR is Signal/Noise ratio. The noise level is usually at -90dbm let's say. This means that if you have a signal at -90dbm, it's completely lost in the noise, it has a SNR of 0.
A signal at -80dbm has a SNR of 10 in the same conditions, it is barely decodable.
However if the noise level is -95 then a signal of -80 will give a SNR of 15 and will be much more decodable.
Noise is usually between -100 and -90 in normal circumstances.
Dbm is another way of expressing power (rather than milliwatts). The advantage of dbm is that you can add or substract antenna gains very easily since those are in db.
20dbm=100mw
The rule is "if you substract 3dbm, divide the mw by 2" and "if you substract 10dbm, divide the milliwats by 10"
So 17dbm = 50mw
13dbm=25mw
10dbm=10mw
The received signal strength which are usually between -40 and -80dbm are then fractions of fractions of microwatts :-)

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SNR (Signal-to-Noise Ratio) is a ratio based value that evaluates your signal based on the noise being seen. So let's look at the components of the SNR and they see how to determine it. SNR is comprised of 2 values and is measured as a positive value between 0db and 120db and the closer it is to 120db the better: Signal Value and Noise Value typically these are expressed in decibels (db).
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The last three things I will kind of explain is the EIRP, Free Space Path Loss, and Client side.
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Actual RSSI + Antenna Gain = Displayed RSSI
-68db + 2db = -66db
I hope all this helps with your question...
Please rate useful posts.
Thanks,
Kayle

What is RSSI , SNR and technical specification value in dbm

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