What will be the minimum Hamming distance for the following coding scheme?

2017

What will be the minimum Hamming distance for the following coding scheme?

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  1. A.

    1

  2. B.

    2

  3. C.

    3

  4. D.

    4

Attempted by 269 students.

Show answer & explanation

Correct answer: B

Concept: The minimum Hamming distance (dmin) of a coding scheme is the smallest number of bit positions in which any two distinct valid codewords differ. The Hamming distance between two equal-length codewords is the count of positions where their bits disagree.

Application: The four valid codewords are 00111, 01001, 10101 and 11100. Compare every one of the six possible pairs and count the differing positions:

  1. 00111 vs 01001: differ at positions 2, 3, 4 → distance = 3

  2. 00111 vs 10101: differ at positions 1, 4 → distance = 2

  3. 00111 vs 11100: differ at positions 1, 2, 4, 5 → distance = 4

  4. 01001 vs 10101: differ at positions 1, 2, 3 → distance = 3

  5. 01001 vs 11100: differ at positions 1, 3, 5 → distance = 3

  6. 10101 vs 11100: differ at positions 2, 5 → distance = 2

Cross-check: The smallest of the six distances {3, 2, 4, 3, 3, 2} is 2, achieved by the pairs 0011110101 and 1010111100. No pair differs in only one position, so the distance cannot be 1.

Result: the minimum Hamming distance of this coding scheme is 2.

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