Robust transmission of progressive image bitstreams based on DCT over broadband wireless channels

A robust progressive image transmission scheme over broadband wireless fading channels is developed for 4~ th generation wireless communication systems (4G) in this paper. The proposed scheme is based on space-time block coded orthogonal frequency-division multiplexing (OFDM) with 4 transmit antennas and 2 receive antennas and uses a simplified minimum mean square error (MMSE) detector instead of maximum likelihood (ML) detectors. Considering DCT is simpler and more widely applied in the industry than wavelet transforms, a progressive image compression method based on DCT called mean-subtract embedded DCT (MSEDCT) is developed, with a simple mean-subtract method for the redundancy of reorganized DC blocks in addition to a structure similar to the embedded zerotree wavelet coding (EZW) method. Then after analyzing and testing bit importance of the progressive MSEDCT bitstreams, the layered unequal error protection method of joint source-channels coding based on Reed-Solomon (RS) codes is used to protect different parts of bitstreams, providing different QoS assurances and good flexibility. Simulation experiments show our proposed scheme can effectively degrade fading effects and obtain better image transmission effects with 10～20 dB average peak-signal-noise-ratio (PSNR) gains at the median E_b/N_o than those schemes without space-time coded OFDM or equal error protections with space-time coded OFDM.