Turbo Encoder

This page covers CTC Encoder basics with rate 1 by 3 example i.e. Convolutional Turbo Encoder technique for Forward Error Correction.

Turbo code is the most popular forward error correction technique used in next generation wireless communication systems such as Mobile WiMAX and LTE. We will understand here CTC or Convolutional Turbo Code technique.

Following figure depicts rate 1/3 CTC encoder used in mobile wimax or 16e OFDMA Physical layer.

turbo encoder

As shown in the figure 1 CTC encoder is used between randomizer and puncturing/interleaving.
CTC encoder is composed of CTC interleaver and constituent encoder and is depicted in figure 2.
There are three steps here.
Step 1: Input bits A and B are passed directly to the output.
Step 2: Input bits A and B are passed through Constituent encoder and will produce Y1,W1. Constituent encoder is explained below.
Step 3: Input bits A and B are passed through CTC Interleaver/Constituent encoder and will produce Y2,W2.

Constituent encoder is composed of 3 shift registers S1,S2 and S3 and all the three step outputs mentioned above are self explanatory and mentioned in figure 3.

MATLAB Code of CTC Encoder

CTC Encoder

Useful References

forward error correction-This page describes forward error correction and its application and mention different forward error correction techniques.
RS Encoder-This page covers RS Encoder i.e. reed solomon encoding basics with example.
convolution encoder implementation with example, Read more.
CRC-This page covers CRC or Cyclic Redundancy Check.

RF and Wireless Terminologies