# Convolution Encoding and Decoding

This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Convolution encoding and decoding”.

1. The measure of the amount of redundancy is given by
a) Code size
b) Code weight
c) Code rate
d) Minimum distance

2. The number of k bit shift over which a single information bit influences the encoder output is given by
a) Code rate
b) Constraint length
c) Code length
d) Code weight

3. The method used for representing convolution encoder are
a) Connection pictorial
b) State diagram
c) Tree diagram
d) All of the mentioned

4. 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

5. Finite state machines have
a) Past memories also
b) Only present and future memories
c) Only future memories
d) Only present memories

6. How many number of transitions can be made at each bit time?
a) One
b) Two
c) Three
d) Half

7. In trellis diagram, the number of nodes ______ at successive branching.
a) Increases by 1
b) Doubles
c) Triples
d) None of the mentioned

8. Example for convolution encoder state diagram is
a) Tree diagram
b) Trellis diagram
c) Tree & Trellis diagram
d) None of the mentioned

9. In maximum likelihood decoding technique, the likelihood function compares the
a) Joint probabilities
b) Individual probabilities
c) Conditional probabilities
d) None of the mentioned

10. In maximum likelihood detector the error probability is
a) Maximum
b) Minimum
c) Zero
d) None of the mentioned

11. For a binary code, the maximum number of possible sequence made up of L branch words is
a) L2
b) 2L
c) 2L
d) L/2

12. If the quantization level of a demodulator output is ________ then it is called as soft decision decoding.
a) Equal to 2
b) More than 2
c) Less than 2
d) None of the mentioned

13. Soft decision decoding requires
a) Less memory
b) More memory
c) More speed
d) None of the mentioned

14. A binary symmetric channel is a
a) Discrete memoryless channel
b) Continuous memoryless channel
c) Discrete memory channel
d) Continuous memory channel

15. Binary symmetric channel is hard decision channel.
a) True
b) False

16. Gaussian channel is a hard decision channel.
a) True
b) False

17. Branch word synchronization is the process of determining the