Multiple description wavelet image coding for reliable delivery and QoS maintenance

We consider the problem of efficient transmission of compressed images over multiple servers for fast and reliable access over the internet and wireless channels. Rather than having identical copies of the data at each server, we present a scheme wherein, each server holds different versions of the compressed images that can either be individually decoded to yield equivalent images, or jointly decoded to obtain a better image quality. We exploit the shift variance of the discrete wavelet transform to generate multiple descriptions of the image, and compress them with a robust image coding algorithm. A given image can be encoded into multiple independent descriptions for storage over multiple servers. The path diversity presented by the networks and the presence of equivalent descriptions on the different servers provide a mechanism for reliable delivery. The approach also ensures a robust delivery of image data in the event of network failures.