Network source coding: Theory and code design for broadcast and multiple access networks.

摘要

In the information age, network systems and applications have been growing rapidly to provide us with more versatile and high bit rate services. However, the limited bandwidth restricts the amount of information that can be sent through the networks. Thus efficient data representation or source coding is imperative for future network development. Distinct from the traditional source coding strategy, network source codes take advantage of the network topology and are able to maximally compress data before transmission.; In this thesis, I present a variety of source coding techniques for use in network environments and demonstrate the benefits of network source codes over traditional source codes from both theoretical and practical perspectives.; First, I address source coding for broadcast systems. The results I obtain include derivation of the theoretical limits of broadcast system source codes, algorithm design for optimal broadcast system vector quantizers, implementation of the optimal code, and experimental results.; Then, I focus on multiple access systems which are the dual systems of broadcast systems. I present the properties of multiple access source codes and generalize traditional entropy code design algorithms to attain the corresponding optimal multiple access source codes for arbitrary joint source statistics. I further introduce a family of polynomial complexity code design algorithms that approximates the optimal solutions. Application to universal coding for multiple access networks when the joint source statistics are unknown a priori is briefly discussed. Finally, I demonstrate algorithmic performance by showing experimental results on a variety of data sets.; Finally, in seeking a simple lossy source coding method for general networks, I apply entropy constrained dithered quantization in network source code design and present the coding results for multi-resolution source codes and multiple access source codes. Multi-resolution and multiple access dithered quantizers are low complexity codes that achieve performance very close to the theoretical rate-distortion bound.