Image Transmission Using LDPC Log Domain Iterative Decoding Method

Abstract: Most source coding standards (voice, audio, image and video) use Variable-Length Codes (VLCs) for compression. However, the VLC decoder is very sensitive to transmission errors in the compressed bit-stream. Previous contributions, using a trellis description of the VLC codeword’s to perform soft decoding, have been proposed. But the complexity of the trellis technique becomes intractable. In this paper, we propose a soft-input VLC decoding method which is not trellis based. Performance in the case of transmission over an Additive White Gaussian Noise (AWGN) channel is evaluated. Simulation results show that the proposed decoding algorithm exhibit very low complexity and also bit error rate (BER) at output of channel decoder decreases with increase in SNR. We consider the serial concatenation of a VLC with the channel code and perform iterative decoding. Results show that, when concatenated with Low Density Parity Check (LDPC) codes, iterative decoding provides remarkable error correction performance. Experimental results indicate that the proposed method requires less iteration and improves overall system performance.

Keywords: JPEG compression, Discrete Cosine Transform (DCT), Huffman encoding, LDPC codes.