A joint source-channel coding scheme for robust image transmission

Summary form only given. We propose a joint source-channel coding scheme for the transmission of images over noisy channels. In this scheme, the interaction between source coding and channel coding is through a small number of parameters. A robust source coder based on the classification of the discrete wavelet transform (DWT) coefficients of the image is coupled with a flexible error control scheme which uses a bank of channel codes. Robustness in the source coder is achieved by scalar quantization of the coefficients followed by robust arithmetic coding to check catastrophic propagation of errors. Robust arithmetic coding generates a sequence of equal-length packets of bits along with a small number of sensitive bits for synchronization. A bank of rate compatible punctured convolutional codes concatenated with an outer error detection code like CRC is used for providing unequal error protection. Error detection is useful for error masking while decoding. The sensitive bits are protected and transmitted separately. An iterative algorithm is developed for selection of source coding rates and channel codes for the sequences of DWT coefficients. The algorithm uses the probabilities of packet decoding errors for the different channel codes and the operational rate distortion performance of the sequences of coefficients for the joint allocation. The system has a high reliability as the sensitive information is kept small. Some simulation results are provided for the transmission of the 512/spl times/512 image Lenna over binary symmetric channels.