Uniform threshold TCQ with block classification for image transmission over noisy channels
A combined source-channel coding scheme without explicit error protection is proposed to transmit images over noisy channels. Major components of the proposed coding scheme include 2-D DCT with block classification, fixed-length uniform threshold trellis coded quantization, optimal bit-allocation algorithm, and noise reduction filters. The integration of these components allows us to organize the compressed bitstream in such a way that it is less sensitive to channel noise, and hence achieves data compression and error resilience at the same time. This paper reports our previous study by incorporating the block classification into the integrated scheme. Experimental results show that, in the case of noise-free channels and at the bit rate of 0.5 bpp, an improvement of 2.33 dB can be achieved with the classification. In the case of noisy channels, the gain decreases as the bit error rate increases. However, we can still achieve an average improvement of 0.46 dB, even for highly noisy channels with BER=0.1. Our proposed system uses no error protection, no synchronization codewords and no entropy coding. However, it shows a decent compression ratio and graceful degradation with respect to increasing channel errors.