What people tend to forget with serial comms is that where you have interference causing errors it is very rarely confined to a single packet and errors often corrupt many packets in long bursts of noise.
Of course, you need an error correcting mechanism; however with true differential signalling such as RS-485 (unmodified) you can get a very reliable transmission and get by with error detection (echo "I got it" or "please resend") rather than error correction.

Erik