Virtual Labs

Tools

Aim

Theory

Pretest

Procedure

Demo

Simulation

Posttest

References

Contributors

Feedback

Aim

Theory

Pretest

Procedure

Demo

Simulation

Posttest

References

Contributors

Feedback

Convolutional Codes and Viterbi Decoding

Choose difficulty:

Beginner

Intermediate

Advanced

1. Choose the correct option for convolutional codes.

a: Convolutional codes can be linear or non-linear codes and they have memory. Explanation

Explanation

b: Convolutional codes are linear codes and they have memory. Explanation

Explanation

c: Convolutional codes are linear codes and they may or may not have memory. Explanation

Explanation

d: Both (B) and (C) are correct. Explanation

Explanation

2. Consider a rate

\mathbf{1/n}

convolutional code with feedforeward encoder implementation.Then the

\mathbf{t}

-th output bit

\mathbf{{v_t^{(j)}}}

of output sequence

\mathbf{{v}^{(j)}}

for

\mathbf{j = 1, 2, \ldots, }

is given by

v_t^{(j)} = \sum_{i=0}^m u_{t-i} g_{t-i}^{(j)}

Explanation

v_t^{(j)} = \sum_{i=0}^m u_i g_{t-i}^{(j)}

Explanation

v_t^{(j)} = \sum_{i=0}^m u_{t-i} g_i^{(j)}

Explanation

d: Data insufficient. Need to provide information about encoder connections. Explanation

Explanation

3. Consider an arbitrary rate

\mathbf{1/2}

feedforeward encoder with memory

\mathbf{2}

. Suppose

\mathbf{\sigma_t = (01)}

and

\mathbf{u_t = 0}

. Then

\mathbf{\sigma_{t+1}}

will be

\sigma_{t+1} = (00)

Explanation

\sigma_{t+1} = (01)

Explanation

\sigma_{t+1} = (001)

Explanation

\sigma_{t+1} = (11)

Explanation

4. Suppose the received sequence is decoded using Viterbi decoder. Select the incorrect statement.

a: Viterbi algorithm provides maximum likelihood decoding. Explanation

Explanation

b: Viterbi algorithm can also be applied when the encoder does not start in all-zero state. Explanation

Explanation

c: Viterbi algorithm will fail if there are multiple states with the same state metric. Explanation

Explanation

d: Consider the forward pass of Viterbi algorithm. In any intermediate step, the arriving path to any state with a larger weight is discarded. Explanation

Explanation

Community Links Sakshat Portal Outreach Portal FAQ: Virtual Labs

AGPL 3.0 & Creative Commons (CC BY-NC-SA 4.0)