Variable block-size double predictor DPCM (VBDP-DPCM) image transmission system over wireless fading channel

摘要

A variable blocksize double predictor differential pulse code modulation (VBDP-DPCM) image coding algorithm is utilized for image transmission over Rayleigh fading channels. Quadtree segmentation algorithm is applied to divide a given digital image into segments of variable size, square blocks, in which the nonstationary statistical characteristics of the given image source can be better exploited. Each variable blocksize sub-image is then applied the double predictor DPCM (DP-DPCM) coding scheme to further reduce the quantization error and produce a better data compression ratio than that of a DPCM scheme. To improve the system performance for transmitting VBDP-DPCM encoded images over wireless fading channel, we have adopted the quadrature phase shift keying (QPSK) modulation as well as a channel coding algorithm in this study. The convolutional encoder and maximum-likelihood Viterbi hard decision decoder are applied to protect the transmitted source data and to reduce bit error rate (BER) in fading channel. Performance of this VBDP-DPCM image transmission system over Rayleigh fading channel is evaluated in this research.