Robust image transmission over wireless CDMA channels using combined error-resilient source coding and channel error control

In this dissertation we study compression and robust transmission of images over wireless channels. Due to the problems associated with wireless channels, image communication over these channels requires error-resilient coding schemes that must offer good compression and low complexity. We propose an analysis-by-synthesis coding technique called Variable Block-size two-dimensional Code Excited Linear Predictive (VB 2D-CELP) coding that implements block-adaptive prediction and variable block-size coding. The method can be used for still picture coding or for periodic intra-frame coding required in time-varying image coding. The scheme demonstrates its merits over the DCT-based JPEG standard by reducing the block effects of the DCT method while having low decoder complexity and offering provisions for error-resilience.; Another important problem studied in this dissertation is the transmission of images over wireless channels, in particular over CDMA Rayleigh fading channels. We develop a robust coding scheme and propose error-resilient tools that are implemented in the source coding scheme to mitigate the effect of uncorrected channel errors and to limit error propagation. Source error detection and concealment techniques are implemented under the source coding constraining conditions or under separation of the responses into zero-input response and zero-state response of each image block.; Based on an investigation of the error sensitivity of the bit-stream of coded images, we propose and investigate strategies that combine error-resilient source coding and channel error control for the purpose of providing robust transmission. The a priori knowledge of the bit-sensitivity of the different types of information of the compressed image data enables us to perform an efficient unequal error protection for robust transmission. For the channel error control, we investigate a type-I hybrid ARQ protocol using concatenated Reed-Solomon/Convolutional coding. We study the system performance for two extreme channel conditions: the perfectly interleaved channel and a quasi-static highly correlated channel. For applications with different quality of service requirements, we study the system performance in terms of reliability and transmission delay and examine the effect of outer interleaving and maximum number of retransmissions on the system performance using a quasi-analytical method for the case of the channel with non-independent errors.; Finally, a coding control technique that dynamically adapts the source coder rate and channel error control to the channel condition is proposed. Based on an estimate of the channel condition, the rate control adapts the source coder rate so as the compression ratio is changed to provide higher channel protection when the channel is severe, and improve the source rate and provide better performance when the conditions are favorable.