Progressive Image Transmission over Ofdm System

A modified Orthogonal Frequency Division Multiplexing (OFDM) system for robust progressive image transmission is proposed in this paper. A joint source-channel coder (JSCC) is employed in the modified OFDM system. The set partitioning hierarchical trees (SPIHT) used as source coder, and The Low-Density Parity-Check (LDPC) used as a channel coder. The SPIHT coder is modified to generate four different groups of bit stream relative to its significances. An unequal error protection (UEP) is suggested for data groups with the LDPC coder. Also, the modified OFDM system includes an adaptive clipping technique as a Peak to average power ratio (PAPR) reduction technique for OFDM signal. This proposed PAPR reduction technique is based on adaptive clipping for the amplitude of the input signal, where each of signals related to the different four groups of the modified SPIHT coder is clipped with a different clipping level according to the group sensitivity. To demonstrate the efficiency of the modified OFDM system with proposed PAPR reduction technique, the simulation results are presented based on bit error rate (BER), the Peak-signal-tonoise ratio (PSNR) and PAPR over AWGN channel. Based on the simulation results, the proposed structure provides a significant improvement in BER and PSNR performances and a reduction in PAPR is achieved.