Error Detection and Correction Questions and Answers

Answer: C

CRC and Hamming code work on data of any size and fixed size respectively.

A cyclic redundancy check divides the whole message, of any length, by a generator polynomial and appends the remainder, so it can protect frames of arbitrary size. A Hamming code is a block code: a fixed number of data bits (for example 4 in the (7,4) code) is combined with a fixed number of parity bits, so it works on fixed-size blocks.

The options with 8-bit, 2-bit or fixed size for CRC reverse or misstate this.

Answer: D

The false statement is binary words from the source will be referred as codewords and those from the channel encoder as data words.

The terms are the other way round. The binary words coming from the source are the data words (messages). The channel encoder adds redundant bits to each data word, and its output words are the codewords.

The other statements are true. A channel encoder adds redundancy so that errors can be detected and possibly corrected. Correcting errors at the receiver without asking for retransmission is forward error correction. In block coding the bit stream is divided into blocks (binary words) that are encoded separately.