# 1.2.10 Error Detection and Correction | Summary and Q&A

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July 12, 2019
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MIT OpenCourseWare
1.2.10 Error Detection and Correction

## TL;DR

Hamming distance is a useful tool for measuring differences between encodings and can be used to detect single-bit errors in code words.

## Key Insights

• 🥺 Single-bit errors in encoded data can lead to misinterpretation of the data.
• 🆘 Hamming distance measures the differences between encodings, which can help identify errors.
• 🫦 A minimum Hamming distance of at least 2 is needed to detect single-bit errors using parity.
• 🕵️ Parity can only detect single-bit errors, and a more sophisticated encoding is needed to detect multiple errors.
• #️⃣ To detect a certain number of errors, the minimum Hamming distance between code words should be one more than the number of errors.

## Transcript

Now let's think a bit about what happens if there's an error and one or more of the bits in our encoded data gets corrupted. We'll focus on single-bit errors, but much of what we discuss can be generalized to multi-bit errors. For example, consider encoding the results of some unpredictable event, e.g., flipping a fair coin. There are two outcomes:... Read More

## Questions & Answers

### Q: What is the purpose of Hamming distance in error detection?

Hamming distance helps measure the differences between encodings, allowing us to identify single-bit errors in code words.

### Q: How does the simple encoding of "heads" and "tails" fail in error detection?

The simple encoding has a Hamming distance of 1 between the code words "0" and "1", making it impossible to differentiate between an uncorrupted encoding of "tails" and a corrupted encoding of "heads".

### Q: How does adding a parity bit help in error detection?

Adding a parity bit increases the minimum Hamming distance between code words from 1 to 2. This enables the detection of single-bit errors since corrupted code words will have an odd number of 1-bits.

### Q: Can parity detect errors with an even number of bit errors?

No, parity can only detect single-bit errors. If there are an even number of bit errors, corrupted code words will have an even number of 1-bits and may appear to be valid.

## Summary & Key Takeaways

• Single-bit errors in encoded data can occur during transmission and lead to misinterpretation of the data.

• Hamming distance is defined as the number of differing positions between two encodings of the same length.

• By choosing code words with a minimum Hamming distance of at least 2, single-bit errors can be detected using parity bits.