Optimizing MDTC over Feedback-less OFDM Channels


Multiple description coding is an interesting alternative image/video coding technique to combat bursty packet losses over wireless channels, and it is especially promising for applications where retransmission is unacceptable. In this paper, we consider image transmission using Multiple description transform coding (MDTC) over orthogonal frequency division multiplexed (OFDM) wireless broadcast channels, where the system may not have any channel feedback. We investigate the redundancy allocation in MDTC, physical layer frequency diversity, and decoding strategies to maximize the quality of reconstruction. Via analysis we show that, error resilience of the descriptions can be increased by suitable assignment of coding redundancy in the transform modules at the source and by exploiting frequency diversity during transmission, which can be further optimized if the channel feedback is available. We also suggest optimum estimation technique with the knowledge of redundancy allocations in reducing distortion of the reconstructed image. Our analytical observations are supported by MATLAB based studies on transmission of image frames.