Error-resilient image transmission system using COTCQ and space-time coded FS-OFDM

We present and evaluate a novel robust image transmission system for frequency selective fading channels. The system combines a wavelet image coder and space-time block codes (STBC) in conjunction with Fractional Sampling OFDM (FS-OFDM). Specifically, we employ an image coder based on channel optimized trellis coded quantization (COTCQ), which has not been previously studied for frequency selective fading channels. We demonstrate that our COTCQ coder based system both with (i) (2,2) STBC OFDM without fractional sampling, and (ii) (2.1) STBC with fractional sampling significantly outperforms a system employing trellis coded quantization (TCQ) and set partitioning in hierarchical trees (SPIHT) image coding in conjunction with (2-1) STBC OFDM at low channel signal-to-noise ratios (SNR). The usage of STBC over FS-OFDM systems improves the capacity and diversity achievable over the frequency selective fading channels. For a channel SNR of 9 dB, for instance, the peak signal-to-noise ratio (PSNR) of the Lenna image is over 2-4dB higher with our system. Importantly, the results demonstrate that the diversity gain obtained with a (2,1) STBC FS-OFDM system with low-complexity maximum ratio combining at the receiver can be translated into significant quality gains (in PSNR) in received images.