MATLAB Examples

Convolutional Encoder with Uncoded Bits and Feedback

The model serves as a unit test bench for the convolutional code implemented. The model shows how to define and use a trellis that describes a convolutional code. The particular code in this example cannot be described by a set of generator and feedback connection polynomials. The code's trellis cannot be created by the poly2trellis because that function expects generator and feedback connection polynomials as input arguments.


Structure of the Convolutional Code

This figure shows the convolutional code.

Structure of the Example

The major components in this example include:

  • A transmit path that builds a representation of the convolutional encoder using discrete low-level delay and sum (XOR) blocks. This representation looks very similar to the figure showing the structure of the convolutional code.
  • A transmit-receive path that builds a representation of the same convolutional encoder using the Convolutional Encoder block. In this case, the description of the encoder is within the block's Trellis structure parameter. This portion of the model also includes the Viterbi Decoder block, which decodes the convolutional code.
  • Both paths compute the number of bit errors.

Open Example Model and Explore Its Contents

Open the example model slex_commcnvencoder.

Results and Displays

When you run the simulation, the block labeled Compare Encoder checks that the two representations of the encoder yield the same result. The block labeled Compare Encoder - Decoder checks that the encoder and decoder work properly as a pair. Each Display block in the model shows an error rate of zero, as expected.

Error rate for Compare Encoder signal: 0.000
Error rate for Compare Encoder-Decoder signal: 0.000