3 - Error Detection and Correction

Question 1

What is a burst error?

Answer 1

2 or more bits in the data unit have been received erroneously.

Question 2

What is the Hamming distance between two words?

Answer 2

Number of differences between corresponding bits.

Question 3

What is the minimum Hamming distance?

Answer 3

Smallest Hamming distance between all possible pairs in a set of words.

Question 4

What minimum Hamming distance is used to guarantee DETECTION of s errors?

Answer 4

s + 1.

Question 5

What minimum Hamming distance is used to guarantee CORRECTION of t errors?

Answer 5

2t + 1.

Question 6

What is a linear block code?

Answer 6

A code in which the XOR of two valid codewords creates another valid codeword.

Question 7

What is a simple parity check code? How many errors can it detect?

Answer 7

Single bit error detecting code with 1 redundant bit and a minimum Hamming distance of 2.

Can detect an odd number of errors.

Question 8

What is the relationship between number of check bits and number of bits in a codeword for a minimum Hamming distance of 3?

Answer 8

n = 2^m - 1

n is codeword bits
m is check bits

Question 9

Where is the checksum used?

Answer 9

In the network and transport layers.