Preface

Summary

About the Book

The book addresses strategies and principles of physical layer coding and signal processing that fully respect and utilize knowledge of the structure of a wireless network. This technique substantially increases the overall network throughput, efficiency, and reliability. Wireless Physical Layer Network Coding (WPNC) (a.k.a. Physical Layer Network Coding (PLNC)) is a general framework for physical (PHY) layer coding and processing strategies in which PHY behavior at a given node depends on its position in the network topology, and the signal-level processing/decoding exploits multiple paths between source and destination. We introduce the concept of Network Coded Modulation (NCM) as a network-structure-aware signal space code, which processes a (hierarchical) joint function of source data. At intermediate nodes NCM utilizes hierarchical decoding, and it is also designed to allow unambiguous decoding at the final destination using multiple hierarchical observations, arriving via different routes. The book addresses the fundamental principles of WPNC in the context of network information theory, and provides a comprehensive classification of the strategies. It also covers advanced design and techniques, including particular coding and processing designs and their respective properties. We also address selected hot research topics and open problems.

Motivation for the Book

It is becoming widely accepted that the most significant future developments in the physical layer of wireless communication systems will not take place in the PHY layer of individual communication links, but rather in the context of complete wireless networks, especially as the density of wireless networks continues to increase. Over the past decade or so there have been significant developments in network information theory; these have shown that very significant overall performance gains are available compared with the conventional paradigm in which PHY techniques are applied to individual links only, leaving network aspects to be dealt with only at higher layers of the protocol stack. One such new research field is network coding, in which coding techniques are applied to multiple data streams at intermediate nodes in a network, rather than only to individual streams on single links. This can exploit network topology to significantly improve throughput in multi-user networks. However, in its original form it operates at the level of data streams, rather than signal waveforms, and hence is not well suited to the inherently broadcast nature of wireless networks.