Performance study of turbo coded wavelet packet based orthogonal frequency division multiplexing system over rayleigh fading channel

Dissertant

Abd Allah, Rawaz Husayn

Thesis advisor

Yusuf, Raghad Zuhayr

University

Salahaddin University-Hawler

Faculty

College of Engineering

Department

Electrical Engineering Department

University Country

Iraq

Degree

Master

Degree Date

2010

English Abstract

The increasing demand for accurate and high data rate services necessitates the development of more efficient wireless communication systems.

Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technique which is well-known to be effective against multipath distortion and suitable for high data rate transmission over wireless channels.

Traditional OFDM systems are based on sinusoidal carriers which can take advantage of Fast Fourier Transform (FFT) technique to implement the system, but windowed sinusoids have high sidelobe energy which leads to a high energy leakage.

To reduce this energy leakage, Discrete Wavelet Packet Transform (DWPT) has been proposed to replace the FFT process, with a comparable complexity, this system is known as Wavelet Packet (WP) based OFDM. In order to have reliable communications, channel coding is often employed.

This thesis improves the performance of the WP based OFDM system by implementing turbo code as a powerful Forward Error Correction (FEC) code.

In this thesis, the performance of turbo coded WP based OFDM for different mother wavelet functions is examined over Additive White Gaussian Noise (AWGN) and Rayleigh fading channel models and the results are compared to turbo coded OFDM.

Most of the results are presented for the Rayleigh fading channel while the results in AWGN channel are considered as a baseline for the Rayleigh fading channel.

The effects of turbo decoder iterations block length, interleaver types, various Doppler shifts, code rate, and different decoding algorithms are examined. The results in AWGN channel and Rayleigh fading channel for turbo coded OFDM and turbo coded WP based OFDM, depicted that the performance of the turbo code is much worse under correlated Rayleigh fading channel than that of AWGN or uncorrelated Rayleigh fading channels.

The best performance in correlated Rayleigh fading channel is obtained using turbo coded WP based OFDM with Daubechies and Symlet wavelet packets which provided over 80 coding gains at a Bit Error Rate (BER) of 10 compared to their corresponding uncoded case for large interleaver size and low code rate. The proposed systems are also used to transmit and receive RGB images over the AWGN and Rayleigh channel models.

The BER of the received images are calculated.

The histograms of the intensity distributions of the original and received images are shown in case of coded and uncoded proposed systems.

Also the peak signal to noise ratio ( ) of the received image compared to the original image is calculated.

Simulation results showed that, turbo code is an excellent choice to enhance the visual quality of the received images, and its iterative decoding procedure can improve the quality of the recovered image.

The best quality of the received images in Rayleigh fading channel is obtained using turbo coded WP based OFDM with Daubechies wavelet packet ( of 41.7730 of the Kid image and 47.1803 of the F16 image) which is slightly better the system with Symlet wavelet packet.

Main Subjects

Electronic engineering

No. of Pages

117

Table of Contents

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Language

English

Data Type

Arab Theses

Record ID

BIM-311069