Question

Periodic truncation is done by

(a) Appending zero to end of the input data sequence

(b) Appending zero to the beginning of the input data sequence

(c) Appending one’s to end of the data sequence

(d) Appending one’s to beginning of the data sequence

The question was asked during an internship interview.

The query is from Convolution Encoding and Decoding in portion Channel Coding of Digital Communications

Answer 1

Correct answer is (a) Appending zero to end of the input data sequence

Easiest explanation: Convolution code are forced into a block structure by periodic truncation which is done by appending zero to the end of the input data sequence, for the purpose of clearing or flushing the encoding shift register of the data bits.