1.2.12 Worked Examples: Error Correction | Summary and Q&A

2.6K views
July 12, 2019
by
MIT OpenCourseWare
1.2.12 Worked Examples: Error Correction

TL;DR

Understanding how encoding can help detect and correct transmission errors using Hamming distance.

Install to Summarize YouTube Videos and Get Transcripts

Q: How does changing a data bit affect the encoding and parity bits?

Changing a data bit results in the data bit itself being flipped, followed by flipping the corresponding row parity bit and column parity bit to maintain odd parity. The parity of the entire message also flips, requiring the bottom right parity bit to be flipped as well.

Q: What is the minimum Hamming distance for this encoding?

The minimum Hamming distance for this encoding is 4, meaning that when a data bit is flipped, a total of 4 entries need to change to maintain the encoding.

Q: Can this encoding detect and correct 1-bit errors?

Yes, since the hamming distance is 4, this encoding can both detect and correct 1-bit errors by checking the parity of each row, column, and the full message.

Q: Can this encoding correct 2-bit errors?

No, this encoding can only detect 2-bit errors but cannot correct them. The hamming distance of 4 falls short of the requirement for correcting 2-bit errors, which would require a hamming distance of at least 5.

Summary & Key Takeaways

• This content explains the encoding of messages with 9 data bits and 7 parity bits, exploring how changing one data bit affects the encoding and parity bits.

• The minimum Hamming distance for this encoding is determined to be 4, indicating the number of entries that need to change to maintain the parity of the entire message when flipping a data bit.

• It is established that this encoding can detect and correct 1-bit errors, but cannot correct 2-bit errors due to the hamming distance of 4.