Network Coding and Wireless Physical-layer ... - Jacobs University

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33 The emergence of scalable video coding standard means that some parts of transmitted data should be better protected than others. This concept is called unequal error/erasure protection (UEP). We will show in Chapter 4 that network coding inherently supports this concept. However, this will inevitably leads to conflicts among receiving nodes in a multicast session. We provide an economic analysis of the conflicts as well as an auction algorithm to resolve them. Rateless codes, such as LT-codes and Rapter codes, are originally designed to guarantee that erasures in the network do not affect data recovery. This seems, at first thought, to imply that they do not support UEP, since the recovery of every data priority seems to be guaranteed. However, a subsequent work by Rahnavard, vellambi, and Fekri, shows that UEP can still be implemented using a similar concept of unequal recovery time (URT) [47]. Their technique ensures that, for an unlimited time, data of all priorities is recovered, but for a specific time range, higher-priority data will be recovered before the lower-priority one. This allows the receiving nodes to decide how long they want to spend time receiving data, according to the number of priorities that they need. However, when rateless codes are used in a network with network coding, another problem arises. We call it the degree distribution distortion problem. This will make the recovery time of every data priority longer than the normal case without network coding. In Chapter 5, we investigate this problem in LT-codes with the simplest case of a butterfly network and gives a solution.
Chapter 4 Unequal Erasure Protection (UEP) in Network Coding 4.1 Introduction to Erasures and Unequal Erasure Protection (UEP) in Network Coding Recent works on network coding consider errors and erasures in networks [5, 58, 60, 82], whereas earlier ones model networks as graphs in which each edge represents an erasurefree channel with a unit capacity [14,61,63]. In this chapter, we consider each edge in the network to represent the data transmission rate of one symbol per unit time in a binary erasure channel (BEC), i.e., the edge capacity is reduced from 1 to 1 − p, if p denotes the erasure probability. We discuss this in the context of generalized networks in Section 4.2. When data is of different importance, it is natural that one prefers to better protect the high-priority data than the low-priority one against errors and erasures. This concept is called unequal error/erasure protection (UEP). Scalable video and image data, such as Scalable Video Coding (SVC) standardized by JVT as an extension of H.264/AVC, consists of several layers of data [64]. Upper layers represent fine details added to lower ones. As shown in Fig. 4.1, when the third layer data is missing, the receiver can only recover the first two layers since the recovery of the 34
Page 1: Network Coding and Wireless Physica
Page 4 and 5: Abstract The general abstraction of
Page 6 and 7: Contents Abstract i Abstract ii Dec
Page 8 and 9: vi CONTENTS 5.4 Degree Distribution
Page 10 and 11: List of Figures 2.1 A basic digital
Page 12 and 13: x LIST OF FIGURES 5.11 Comparison o
Page 14 and 15: Part I Motivation, Overview, and In
Page 16 and 17: Chapter 1: Motivation and Overview
Page 18 and 19: Chapter 2 Introduction to Digital C
Page 20 and 21: Chapter 2: Introduction to Digital
Page 30 and 31: Chapter 3: Introduction to Graphs a
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Chapter 6: Wireless Physical-layer
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Chapter 7 Physical-layer Key Encodi
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Chapter 7: Physical-layer Key Encod
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Chapter 8: Summary, Conclusion, and
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Bibliography [1] 3GPP, “3GPP; Tec
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BIBLIOGRAPHY 121 [21] F.A. Hayek,
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BIBLIOGRAPHY 123 [43] M. Friedman a
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BIBLIOGRAPHY 125 [63] S. Jaggi, P.
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BIBLIOGRAPHY 127 [81] X. Sun, X. Wu
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