Performance Evaluation of orthogonal frequency division multiplexing (OFDM communication systems

Orthogonal Frequency-Division Multiplexing (OFDM) becomes the most promisingtechnology that enables transmission of high data rates. The basic idea of OFDM is to use alarge number of parallel narrowband sub-carriers instead of a single wideband carrier totransport information. OFDM effectively provides broadband wireless communication inhostile multipath environments. Furthermore OFDM is robust against Inter-SymbolInterference (ISI) and fading caused by multipath propagation. To improve the Bit ErrorRate (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 twoprimary drawbacks. The first is the high sensitivity to carrier frequency offsets and phasenoise. The second, and the major aspect to be concerned, is the high Peak-to-Average PowerRatio (PAPR) of the transmitted signals. The high PAPR makes OFDM sensitive to nonlineardistortion caused by the transmitter’s Power Amplifier (PA), and hence lead to degradation insystem performance.This thesis is mainly concerned with image transmission using OFDM, as a vital issue inmodern communication systems. The thesis begins with an overview of the OFDM systemand the PAPR problem in multi-carrier systems. After that, an overview of LDPC coding ispresented as the coding scheme adopted in the thesis. For image transmission, compression isvery important. So, the thesis will present a survey of the Set Partitioning In HierarchicalTrees (SPIHT) compression technique as it is used as the image compression technique.Three proposed P APR reduction methods for OFDM signals are presented. The firstone is based on discrete transforms and permutations, the second one is based on chaoticinterleaving with the chaotic Baker map, and the third one is a hybrid approach (chaoticBaker map + Companding). The effect of these three proposed methods on efficiency ofcompressed image communication process is studied. Also the effect of LDPC coding onimage transmission process with the proposed P APR reduction methods is studied. The mainobjective is to get into a trade-off between the required reduction in the P APR and therequired high quality of communicated images.