Coding gain in error-correcting codes is defined as?

• A. Improvement in required SNR to achieve a target BER due to coding
• B. The decoding complexity
• C. The data rate increase
• D. A reduction in transmission power for same BER

Answer: (B)

Coding gain is the amount by which using an error-correcting code reduces the signal-to-noise ratio needed to reach a specified error rate. In other words, it’s the improvement in Es/N0 (or Eb/N0) for the same target BER that coding provides. It’s typically expressed in decibels.

Think of it as comparing two systems at the same BER: the coded system can operate with a lower SNR than the uncoded one. For example, if achieving a BER of 10^-5 requires 8 dB Es/N0 without coding but only 5 dB Es/N0 with coding, the coding gain is 3 dB.

This concept is distinct from decoding complexity, which is about the resources needed to decode, or from data rate changes, since coding adds redundancy that can lower the net data rate unless the code rate is considered. It’s also not simply “reducing transmit power” by itself, although achieving the same BER with coding can allow you to lower transmit power (a practical outcome of the SNR improvement).