A frame-work for joint source-channel coding of images over time-varying wireless channels

This paper presents a frame-work for joint source-channel coding of images over time-varying wireless channels. The source coding algorithm produces an embedded bit-stream to support decoders at different bandwidths. The embedded (source) bit-stream produced is prioritized with bits arranged in order of visual importance. The subjective quality of compressed images improves significantly by the use of perceptual distortion measures in the source coder. Rate-compatible punctured convolutional codes (RCPC) suited for a time-varying channel are used as the channel codes in the joint source-channel codec. The advantage of using RCPC codes is that the high rate codes are embedded into the lower rate codes of the family and the same Viterbi decoder can be used for all codes of a family. A DQPSK modulator is used for transmission in our system. We consider the rate allocation between the source and channel for four scenarios. The scenarios vary according to the amount of information at the transmitter about the channel state at the receiver