Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- Acknowledgments
- Notation
- 1 Introduction
- Part I Preliminaries
- Part II Single-Hop Networks
- 4 Multiple Access Channels
- 5 Degraded Broadcast Channels
- 6 Interference Channels
- 7 Channels with State
- 8 General Broadcast Channels
- 9 Gaussian Vector Channels
- 10 Distributed Lossless Compression
- 11 Lossy Compression with Side Information
- 12 Distributed Lossy Compression
- 13 Multiple Description Coding
- 14 Joint Source–Channel Coding
- Part III Multihop Networks
- Part IV Extensions
- Appendices
- Bibliography
- Common Symbols
- Author Index
- Subject Index
13 - Multiple Description Coding
from Part II - Single-Hop Networks
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Dedication
- Contents
- Preface
- Acknowledgments
- Notation
- 1 Introduction
- Part I Preliminaries
- Part II Single-Hop Networks
- 4 Multiple Access Channels
- 5 Degraded Broadcast Channels
- 6 Interference Channels
- 7 Channels with State
- 8 General Broadcast Channels
- 9 Gaussian Vector Channels
- 10 Distributed Lossless Compression
- 11 Lossy Compression with Side Information
- 12 Distributed Lossy Compression
- 13 Multiple Description Coding
- 14 Joint Source–Channel Coding
- Part III Multihop Networks
- Part IV Extensions
- Appendices
- Bibliography
- Common Symbols
- Author Index
- Subject Index
Summary
We consider the problem of generating two descriptions of a source such that each description by itself can be used to reconstruct the source with some desired distortion and the two descriptions together can be used to reconstruct the source with a lower distortion. This problem is motivated by the need to efficiently communicate multimedia content over networks such as the Internet. Consider the following two scenarios:
• Path diversity: Suppose we wish to send a movie to a viewer over a network that suffers from data loss and delays. We can send multiple copies of the same description of the movie to the viewer via different paths in the network. Such replication, however, is inefficient and the viewer does not benefit from receiving more than one copy of the description. Multiple description coding provides a more efficient means to achieve such “path diversity.” We generate multiple descriptions of the movie, so that if the viewer receives only one of them, the movie can be reconstructed with some acceptable quality, and if the viewer receives two of them, the movie can be reconstructed with a higher quality and so on.
• Successive refinement: Suppose we wish to send a movie with different levels of quality to different viewers. We can send a separate description of the movie to each viewer. These descriptions, however, are likely to have significant overlaps. Successive refinement, which is a special case of multiple description coding, provides a more efficient way to distribute the movie. The idea is to send the lowest quality description and successive refinements of it (instead of additional full descriptions). Each viewer then uses the lowest quality description and some of the successive refinements to reconstruct the movie at her desired level of quality.
The optimal scheme for generating multiple descriptions is not known in general. We present the El Gamal–Cover coding scheme for generating two descriptions that are individually good but still carry additional information about the source when combined together. The proof of achievability uses the multivariate covering lemma in Section 8.4. We show that this scheme is optimal for the quadratic Gaussian case. The key to the converse is the identification of a common-information random variable. We then present an improvement on the El Gamal–Cover scheme by Zhang and Berger that involves sending an additional common description.
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- Information
- Network Information Theory , pp. 320 - 335Publisher: Cambridge University PressPrint publication year: 2011