Performance Analysis Of Turbo Codes

Résumé: Telecommunication is one of the most important technologies present this days. One problem with communication is that wrong interpretations may occur in the case of receiving data from a noisy channel. Telecommunication engineers were trying all the time to develop new channel coding techniques that ensure the safe transfer of information in the presence of any undesirable effect and produce results very close to the theoretical limit set by Shannon, such as turbo codes. Turbo codes have been successfully implemented in satellite and video conferencing systems and provision has been made in 3rd and 4th generation mobile systems. This project presents an evaluation of soft output decoding for turbo codes. Coding theory related to this work is studied, including convolutional encoding and Viterbi decoding. Recursive systematic convolutional (RSC) codes and nonuniform interleavers commonly used in turbo code encoder design are analysed. The scope of this work is analysing the performance of the Turbo code. Using MATLAB we have implemented a digital communication system i.e. a transmitter, a channel and a receiver, both transmitter and receiver are turbo encoder and decoder. After the simulation of our system, the results are presented in the form of curves (bit error rate versus signal to noise ratio) This includes thorough investigation of central components that influence Turbo code performances, such as the constraint length of the encoder, the type of modulation, the type of the interleaver, as well as the procedure of iterative decoding. The whole investigation is carried out over an additive white Gaussian noise channels and the results are discussed in details in the coming chapters.

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