Signal-to-Noise Ratio

Caution

Key Formula — SNR and thermal noise power

$$\mathrm{SNR}=\frac{S}{N},\quad \mathrm{SNR_{dB}}=10\log_{10}\frac{S}{N};\qquad N=kTB,$$$$N(dBW)=-228.6+10\log_{10}T+10\log_{10}B.$$

SNR sets the bit-error rate and hence the choice of modulation and coding, the minimum antenna size and transmit power, and the rain-fade margin. It is the downlink counterpart of the C/N computed from the link budget.