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OFDM modulation has been adopted by several wireless multimedia transmission standards, such as Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB-T), because it provides a high degree of immunity to multipath fading and impulsive noise. High spectral efficiency and efficient modulation and demodulation by IFFT/FFT are also advantages of OFDM. In the frequency-selective radio transmission channel, all fading and Inter-Symbol Interference (ISI) result in severe losses of transmitted image quality. OFDM divides the frequency-selective channel into several parallel nonfrequency selective narrow-band channels and modulates the signal into different frequencies. It can significantly improve the channel transmission performance without employing complex equalization schemes. It also has a broad application prospect in wireless image and video communications.
In this design, a new scheme for progressive image transmission over coded Orthogonal Frequency Division Multiplexing (OFDM) system with Low-Density Parity-Check Coding (LDPC) is developed using Matlab. 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 the OFDM signal. It improves the error resilience ability and transmission efficiency for progressive image transmission over Additive White Gaussian Noise (A WGN) channel. The Set Partitioning In Hierarchical Trees (SPIHT) algorithm is used for source coding of the images to be transmitted. First, 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 Matlab simulation results show that adding the DST to the system improves the visual quality of reconstructed images and reduces the PAPR of OFDM signal more than the DCT.
Reference Paper: Robust Image Transmission with OFDM over an AWGN Channel
Author’s Name: Naglaa F. Soliman, Abd Alhamid. A. Shaalan, and Mohammed. M Fouad
Year:2011
Source: National Telecommunication Institute, Egypt
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SIMULATION VIDEO DEMO
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