Error Detection Correction Techniques — Test 1

Correct Answer: A. A. 4
Explanation: Hamming distance can be obtained by performing X-OR operation on two words of same length, then the number of 1s in the resulting word will be the hamming distance. It is used to find and correct the errors.

Correct Answer: A. A. Difficult to correct
Explanation: The burst errors can be detected easily but it is difficult to correct them, as they happen to appear as blocks. When the error rate is low, burst errors are convenient to detect compared to single bit errors.

Correct Answer: A. A. 1
Explanation: In order to find the minimum hamming distance between the set of words, the hamming distance between all pairs of the set should be calculated. The least number in the resulted hamming distances will be the minimum hamming distance.

Correct Answer: D. D. Hamming codes
Explanation: Hamming code assigns consecutive numbers for code word; the code word will have check bits in place of the numbers that are powers of 2 and the remaining numbers contain bits of data word.

Correct Answer: B. B. False
Explanation: An error is considered as a burst error, if two or more bits get corrupted, but they don’t need to be consecutive bits. Length of the burst independent of sequence, that is length between first burst bit to last burst bit is considered as length of burst.

Correct Answer: A. A. 1 bit
Explanation: Code word will have total of k+1 bits where k is the number of bits in data word. This extra parity bit helps the code word to have even number of 1s and it can be 0 or 1. Parity code is an error detecting code but doesn’t correct the errors.

Correct Answer: C. C. Binary convolution codes
Explanation: Unlike block codes, convolution codes don’t have encoding boundary. The encoder in this convolution codes deals with sequence of bits and outputs sequence of bits using constraint length of the code.

Correct Answer: D. D. Reed solomon codes
Explanation: Hamming codes and convolution codes works well for single bit errors, whereas Reed Solomon codes works well for burst errors. Because it uses m bit symbols, which are used to treat single bit and m bit burst errors equally as a single symbol error.

Correct Answer: C. C. 3
Explanation: Two-dimensional parity check was introduced to overcome the problem in simple parity check code that it is able to find only odd numbers of errors. Two-dimensional parity arranges the code into columns and rows and add parity bits in each column and row to find errors up to 3.

Correct Answer: B. B. False
Explanation: Simple parity check uses only one bit for parity and the bit that is added to a data word can detect odd number of errors only. Because, the even parity will be same after even number of errors occur and it shows no error.