What is SNR (Signal to Noise ratio)

SNR (Signal to Noise ratio) : 

• As SNR = Signal Strength (dBm)/ Noise Floor(dBm) 
• Noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals 
• Since dBm is in logarithmic scale, SNR is obtained by subtracting the noise from the signal strength i.e (SNR = Signal Strength – Noise Floor)
• The minimum required SNR for a receiver varies depending on the bit rate or modulation.
• A positive SNR is required (i.e., signal strength should be a higher than the noise) 
• E.g if a radio (client device) receives a signal of -75 dBm and the noise floor is measured at -90 dBm, the SNR is 15 dB [ -75 – (- 90) = 15 ]
• SNR value decreases if the length between receiver and Sender increases. Because of Loss / Attenuation .
• An increase in RF interference from microwave ovens and cordless phones, which increases the noise level, also decreases SNR. 
• A higher SNR value means that the signal strength is stronger in relation to the noise levels, which allows higher data rates.