Robust transmission of html files: Iterative joint source-channel decoding of deflate codes

This paper considers the transmission problem over a noisy mobile radio channel of encoded html files according to the http1.1 protocol specifications. The deflate algorithm encodes the html files using the combination of two entropy coding algorithms: Lempel-Ziv and Huffman. The developed receiver is based on an iterative joint source channel decoding approach using the turbo principle built from two serial concatenated codes. The proposed Soft-Input Soft-Output inner decoder is based on the traditional sequential M-algorithm which is modified in order to improve the performance of the decoder. The proposed algorithm exploits the specific grammatical rules of Huffman codes, Lempel-Ziv codes and the syntax of the html language. This decoder is combined to a Soft-Input Soft-Output channel decoder of convolutional codes. Simulation results, over an additive white gaussian noise channel, show that the proposed receiver reduces the number of errors occurring in the transmitted html file compared to any conventional channel decoding.