الفهرس 
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Abstract
Orthogonal Frequency-Division Multiplexing (OFDM) becomes the most promising
technology that enables transmission of high data rates. The basic idea of OFDM is to use a
large number of parallel narrowband sub-carriers instead of a single wideband carrier to
transport information. OFDM effectively provides broadband wireless communication in
hostile multipath environments. Furthermore OFDM is robust against Inter-Symbol
Interference (ISI) and fading caused by multipath propagation. To improve the Bit Error
Rate (BER) performance of OFDM, error correcting codes are utilized. Low-Density Parity-
Check (LDPC) codes have attracted much attention particularly in the field of coding theory.
So, they can be effectively applied with OFDM.
Orthogonal Frequency-Division Multiplexing communication systems suffer from two
primary drawbacks. The first is the high sensitivity to carrier frequency offsets and phase
noise. The second, and the major aspect to be concerned, is the high Peak-to-Average Power
Ratio (PAPR) of the transmitted signals. The high PAPR makes OFDM sensitive to nonlinear
distortion caused by the transmitter’s Power Amplifier (PA), and hence lead to degradation in
system performance.
This thesis is mainly concerned with image transmission using OFDM, as a vital issue in
modern communication systems. The thesis begins with an overview of the OFDM system
and the PAPR problem in multi-carrier systems. After that, an overview of LDPC coding is
presented as the coding scheme adopted in the thesis. For image transmission, compression is
very important. So, the thesis will present a survey of the Set Partitioning In Hierarchical
Trees (SPIHT) compression technique as it is used as the image compression technique.
Three proposed P APR reduction methods for OFDM signals are presented. The first
one is based on discrete transforms and permutations, the second one is based on chaotic
interleaving with the chaotic Baker map, and the third one is a hybrid approach (chaotic
Baker map + Companding). The effect of these three proposed methods on efficiency of
compressed image communication process is studied. Also the effect of LDPC coding on
image transmission process with the proposed P APR reduction methods is studied. The main
objective is to get into a trade-off between the required reduction in the P APR and the
required high quality of communicated images.