Optimized Transmission of Images with OFDM over AWGN Channel Using Trigonometric Transforms

A new scheme is proposed for progressive image transmission over coded Orthogonal Frequency Division Multiplexing (OFDM) system with Low Density Parity Check Coding (LDPC). Trigonometric transforms are used in this scheme for improving the performance of the OFDM systems and reducing the Peak-to-Average Power Ratio (PAPR) of OFDM signal. It improves the error resilience ability and transmission efficiency for progressive image transmission over Additive White Gaussian Noise (AWGN) channel. The Set Partitioning in Hierarchical Trees (SPIHT) algorithm is used for source coding of the images to be transmitted. In the proposed scheme the transmit data sequence of the OFDM signal after Inverse Fast Fourier Transform (IFFT) is grouped into in-phase and in-quadrature components, then each component is transformed using either the Discrete Cosine Transform (DCT) or the Discrete Sine Transform (DST). The results show that adding the DST to the system improves the visual quality of reconstructed images and reduces the PAPR of OFDM signal. The major obstacle is the high peak-to-average power ratio (PAPR) in the OFDM signal causing non-linearity at the receiving end. This paper focuses on the fact of greatly reducing the PAPR present in the OFDM signal.