How do forward error correction and interleaving complement each other in DVB-S2?

• A. FEC adds redundancy to correct errors; interleaving disperses burst errors over time to improve FEC effectiveness.
• B. Interleaving adds redundancy to correct errors; FEC disperses burst errors over time.
• C. FEC reduces required bandwidth, while interleaving increases it.
• D. Interleaving eliminates the need for any FEC.

Answer: (A)

Forward error correction provides redundancy so the receiver can detect and fix errors without retransmission. In satellite links, errors often come in bursts rather than isolated bits. If a burst hits a single codeword hard, the FEC might not be able to correct it. Interleaving reshuffles the order of bits before transmission, so a burst affects different codewords across time. After deinterleaving, those errors become scattered as small errors across many codewords, which the FEC can correct more effectively. In short, FEC supplies the error-correcting capability, while interleaving makes burst errors look like random, smaller errors to that capability. Interleaving doesn’t add redundancy by itself, and it helps the FEC work far better in a DVB-S2 environment, though it adds some latency.