Joint Source-Channel Synchronisation and Unequal Error Protection For Image Transmission

In this paper we propose a new application of Unequal Error Protection (UEP), in which UEP is used to improve channel and source synchronisation for image transmission. The source coding strategy consists of a 2-D wavelet decomposition followed by quantization and Huffman coding. Source synchronization is achieved by inserting resynchronisation markers into the Variable length Coded bit stream and UEP at the source coding level is employed by unequally assigning the number of resynchronisation markers to the image subbands based on their level of importance. At the channel level, Rate Compatible Punctured Turbo (RCPT) codes are used to unequally allocate code rates to the image subbands, and for channel synchronisation, the Code Assisted Bit Synchronisation scheme is adapted to the RCPT codes. In this way UEP is applied at both source and channel level to improve both synchronisation and error performance. Gains of over 6 dB in terms of Peak to Peak Signal to Noise Ratio (PSNR) was observed for some Es/No values when compared to an Equal Error Protection scheme.