Explain the meaning of signal-to-noise ratio and its effect on communication performance.

• A. SNR is the ratio of noise power to signal power; higher SNR degrades performance.
• B. SNR is the power ratio between signal and noise; higher SNR reduces BER and improves quality.
• C. SNR is the ratio of signal power to interference power only.
• D. SNR does not affect communication quality.

Answer: (B)

The main idea is how clearly the useful signal can be distinguished from the background noise. SNR is the ratio of signal power to noise power. When expressed in a linear scale, it’s P_signal divided by P_noise, and in dB it’s 10 log10(P_signal / P_noise). As this ratio gets larger, the signal stands out more against the noise, so the receiver can detect symbols more reliably. That means the bit error rate drops and the overall communication quality improves.

If you swapped the ratio (noise power relative to signal power), you’d be describing the inverse, which would imply worse performance as the ratio grows—this isn’t how SNR is defined. Also, SNR focuses on noise, not interference; when interference is a concern, the relevant metric is SINR (signal-to-interference-plus-noise ratio), not SNR. Finally, saying SNR doesn’t affect quality is incorrect because higher SNR generally leads to clearer reception and better performance.