Getting Started

Building the Cyclic Code Model

You can build the cyclic code model by adding blocks to the model shown in the figure BPSK Modulation Model. To do so, follow these steps:

1. Type bpskdoc at the MATLAB prompt to open the BPSK model. Then save the model as my_cyclic in the directory where you keep your work files.
2. Drag the following two Communications Blockset blocks from the Simulink Library Browser into the model window:
• Binary Cyclic Encoder block, from the Block sublibrary of the Error Detection and Correction library
• Binary Cyclic Decoder block, from the Block sublibrary of the Error Detection and Correction library
3. Widen the model window and connect the blocks as in the following figure.

   

Binary Cyclic Encoder and Decoder

The Binary Cyclic Encoder block implements a binary cyclic code. The block has the following parameter settings:

• Codeword length 4
• Message length 7

The code rate is given by

This example uses a rate 4 / 7 code. The codeword length N must have the form 2^M - 1, where M is an integer greater than or equal to 3. The input to the block must have the same size as the setting for Message length.

The Binary Cyclic Decoder block decodes the signal after it passes through the channel. The block should have the same parameter settings as the Binary Cyclic Encoder block.

Reducing the Error Rate with a Cyclic Code

Setting Parameters in the Cyclic Code Model