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Series Editor: Biswanath Mukherjee Optical Networks

Massimo Tornatore Gee-Kung Chang Georgios Ellinas Editors

Fiber-Wireless Convergence in Next-Generation Communication Networks Systems, Architectures, and Management

Optical Networks

Series editor

Biswanath Mukherjee, Davis, USA

The book series in Optical Networks encompasses both optical communications and networks, including both theoretical and applied books. The series describes current advances at the cutting edge of the field and is aimed especially at industry practitioners, researchers, and doctoral students.

The series emphasizes the following major areas:

• optical network architectures; • enabling technologies for optical communication networks; • wavelength-division multiplexing (WDM) based networks; • optical access and metro networks; • long-haul optical networks; • optical packet networks; • optical burst-switched networks; • fault-tolerant optical networks; • optical network control and management; and • emerging industry standards.

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• Intermediate to advanced level textbooks as well as expository books that extend and unify our knowledge and understanding of particular areas;

• Handbooks and professional reference works that redefine “state-of-the-art,” emphasizing expository surveys, completely new advances, and combinations thereof;

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• Research monographs that make substantial contributions to new knowledge in specialty subtopics.

These peer-reviewed titles ensure the highest quality content.

More information about this series at http://www.springer.com/series/6976

Massimo Tornatore • Gee-Kung Chang Georgios Ellinas Editors

Fiber-Wireless Convergence in Next-Generation Communication Networks Systems, Architectures, and Management

123

Editors Massimo Tornatore Department of Electronics, Information and Bioengineering, DEIB

Politecnico di Milano Milan Italy

Gee-Kung Chang School of Electrical and Computer Engineering

Georgia Institute of Technology Atlanta, GA USA

Georgios Ellinas Department of Electrical and Computer Engineering

University of Cyprus Cyprus Cyprus

ISSN 1935-3839 ISSN 1935-3847 (electronic) Optical Networks ISBN 978-3-319-42820-8 ISBN 978-3-319-42822-2 (eBook) DOI 10.1007/978-3-319-42822-2

Library of Congress Control Number: 2016954914

© Springer International Publishing Switzerland 2017 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made.

Printed on acid-free paper

This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Gee-Kung Chang dedicates this book to his wife Sharon

Georgios Ellinas dedicates this book to his nephew Nicolas and his niece Carina

Massimo Tornatore dedicates this book to his father Antonio

Foreword

Optical fiber networks and wireless networks have recently undergone significant technological and architectural evolution through, e.g., massive deployments of 4G mobile networks and passive optical networks (PON). These sustained infrastruc- ture upgrades have led to enormous investments for operators (billions of dollars). The next important step is near, as 5G communication networks are expected to be deployed by 2020, featuring unprecedented performance in terms of higher data rates, lower latency, and network flexibility. To achieve this, 5G will resort to solutions such as small-cell deployment (micro, femto, etc.), coordinated multi-cell processing, and centralized radio access networks that will ultimately burden the optical metro/access segment due to the massive amount of mobile traffic to be backhauled with sub-ms latency. Operators are now looking at a promising set of techniques characterized by strict cooperation between fiber-based and wireless-based technologies. These techniques are generically referred to as fiber- wireless convergence, forming the main subject of this book.

This book’s editors have done an excellent job in capturing the various technical facets of fiber-wireless convergence. They present, using a set of clear and cohesive edited contributions, the impact and role of fiber-wireless convergence in various areas of network engineering, covering transmission systems, network architec- tures, and network management and control.

The book has been co-edited by Professor Gee-Kung Chang of Georgia Tech University in Atlanta, Professor George Ellinas of University of Cyprus, and Professor Massimo Tornatore of Politecnico di Milano, Italy. The editorial team has diverse and complementary expertise on the various areas of fiber-wireless con- vergence, which is then reflected in the comprehensive coverage of the book that spans, e.g., from detailed description of key transmission systems such as digital radio-over-fiber (D-RoF), to the role of software-defined network (SDN) control for convergence.

The book is divided into four parts: (1) path towards convergence; (2) systems; (3) architectures; and (4) management. In Part I, the reader is introduced to fiber-wireless convergence, both from the point of view of today’s market trends

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and from the point of view of the 5G technical challenges that call for convergence. In Part II, transmission systems which are more directly affected by convergence are overviewed, with a description of analog and D-RoF techniques, millimeter-wave wireless, and a detailed overview of system challenges that can be addressed by SDN. Part III captures the relevant problems and challenges on network architec- tures, covering topics as PON-based convergence, hoteling of remotized baseband functions “BBU hoteling”, and the “No Cell” vision of future mobile networks. Finally, Part IV includes relevant management and control problems such as the new role of metropolitan central office (Next Generation Point of Presence), and impact of SDN and radio coordination on convergence.

The editors deserve praise for the excellent lineup of contributing authors, who come from leading companies, reputable universities, and research laboratories, and with strong geographical diversity. This book is highly recommended as it offers timely, comprehensive, and authoritative reference to information on fiber-wireless convergence. We expect that the reader will enjoy the book.

August 2016 Biswanath Mukherjee University of California

Davis, USA

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Preface

Communication networks must continuously evolve to ensure a sustainable growth of our “Internet Society.” It has been repeatedly observed that the push for more and more advanced network services leads inevitably to an exponential growth of traffic volumes and to higher quality-of-service requirements by the users; only by resorting to novel technologies and architectural solutions network, operators can keep pace with users’ requirements. The next big innovations in the telecom industry seem to be the forecasted massive deployment of IoT devices (hence the related machine-to-machine communication paradigm), the explosion of video-content network distribution, and the development of ultra-low latency net- work services. To address the technical challenges associated with these services, many companies, research institutes, and standardization bodies have now started the race towards the 5th generation of mobile communications. Fifth-generation networks are expected to support unprecedented bit rates, guaranteeing strict latency and reliable performance, and offering support for connecting together a tremendous number of devices. Fifth-generation networks will use very dense, low-power, small-cell networks with a high spatial reuse and a high degree of coordination due to strong inter-cell interference. Both fiber-based and wireless- based backhaul solutions will be used to connect small cells and the core network, but so far, access and backhaul are individually designed and therefore not jointly optimized. Hence, the design of 5G networks has long dictated the necessity to merge the currently distinct fiber and wireless infrastructures into an amalgamated network capable of combining the strength of both technologies: the stability and high bandwidth of optical fibers with the flexibility and mobility of wireless net- works. This process of integration of the two technologies is usually referred as fiber-wireless convergence (or fixed-wireless convergence) and comprises a large set of technical challenges and solutions.

In this book, we provide the recent developments in the field of fiber-wireless convergence, concentrating on solutions that will be used to support the backhaul, midhaul, and fronthaul of 5G networks. The text presents the trends of industry, as well as current research, in state-of-the-art architectures of converged systems and networks, and takes a vertically layered approach starting from systems,

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to architectures, to management/control issues of fixed-mobile convergence. This book is different from a number of other works on 5G networks that tend to focus heavily on the wireless aspects of 5G. Instead, we decided to look at both networking and systems issues, and focus on the latest research developments in a number of areas including radio over fiber, centralized cloud radio access network, and coordinated multi-point transmission for multiple base stations. This book is meant to be an introduction for any reader interested in having a holistic approach to the technical issues in fiber-wireless convergence and to readers interested in understanding some key aspects in more depth. The aim of the editors is to present a body of work that can provide the research scientist, company engineer, and the university professor/researcher with a better understanding on fiber-wireless con- vergence and ensure that experienced as well as novice researchers can have a single handy source of reference on this topic.

The book is divided into four parts that can appeal to different needs of readers, who are interested in various networking domains and issues. Part I is comprised of the introduction, the market, and the technical motivations for fiber-wireless convergence. Part II presents and discusses transmission systems for wireless-signal transport over fiber (A-RoF and D-RoF), and competing technology to these sys- tems (namely multi-band RF and millimeter-wave transmission), and a set of opportunities that software-defined networks (SDNs) enable for such transmis- sion systems. Part III concentrates on architectural issues related to network inte- gration of fiber and wireless technologies (including use of PONs for mobile backhauling, baseband-unit hoteling, and centralized/coordinated architectures for radio access network, as the No-More-Cell architecture). Finally, Part IV covers management/control topics related to how and which network functions should converge in specific metro offices (Next Generation Point of Presence), as well as provides a closer look to some of these functions such as radio coordination and other SDN-controlled cloud services.

Acknowledgments We are extremely grateful to our past advisors and mentors, colleagues, students, and friends, who have motivated, inspired, and guided us to work in the new field of fiber-wireless convergence. All of them offered us their invaluable advise, exceptional insight, and foresight. They provided us with valu- able guidance throughout the years and helped us better understand and appreciate various aspects of this new technological area. We would also be remiss if we did not extend a thank you to Professor Biswanath Mukherjee for taking the time to write the Foreword for this book and for his patience and encouragement while this book was being prepared and delivered. We also wish to express our thanks to Zoe Kennedy, Mary James, and the entire publishing team at Springer Verlag, for their effort and patience in order to bring this project to fruition. Also, a special thanks goes to all the authors who contributed chapters for this book. Finally, Georgios Ellinas is greatly indebted to his family for their understanding and patience during this undertaking. Gee-Kung Chang wishes to thank his wife for her unwavering support and express profound gratitude to Ken Byers who endows an eminent scholar chair professor in advanced telecommunications research at Georgia Tech for several decades. Massimo Tornatore gratefully acknowledges his family and his

x Preface

fiancée Angela, for their constant love and support. Massimo Tornatore wants to acknowledge the European Community’s COMBO project, during which he gained an invaluable amount of knowledge on the topics of this book.

Milan, Italy Massimo Tornatore Associate Professor

Atlanta, USA Gee-Kung Chang Professor

Byers Eminent Scholar Chair Professor in Optical Networking

Georgia Research Alliance Eminent Scholar

Cyprus, Cyprus Georgios Ellinas Associate Professor

Preface xi

Contents

Part I The Path Towards Convergence

1 Future Radio Access, Wi-Fi-LTE, LTE-Advanced: The Path to 5G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Rajarajan Sivaraj and Prasant Mohapatra 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1.1 LTE Principles of Operation and Deployment . . . . . . . 4 1.2 Carrier Aggregation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.2.1 Definitions and Terminologies . . . . . . . . . . . . . . . . . . . 9 1.2.2 Types of Carrier Aggregation . . . . . . . . . . . . . . . . . . . 10 1.2.3 Radio Resource Management Framework for CA . . . . 15

1.3 Transmission Diversity and Spatial Multiplexing . . . . . . . . . . . . 18 1.3.1 Transmit Diversity—Definition and Terminologies . . . 18 1.3.2 MIMO and Spatial Multiplexing—Definition and

Terminologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.3.3 Coordinated Multi-point Transmission. . . . . . . . . . . . . 19 1.3.4 Types of CoMP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.3.5 Advancements: 3D Beamforming . . . . . . . . . . . . . . . . 24 1.3.6 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

1.4 Wi-Fi-LTE, Unlicensed LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.4.1 Definition and Terminologies . . . . . . . . . . . . . . . . . . . 27 1.4.2 CA of LTE-Licensed and LTE-U CCs . . . . . . . . . . . . 28

1.5 Network Heterogeneity: Self-organizing HetNets . . . . . . . . . . . . 30 1.5.1 Definition and Terminologies . . . . . . . . . . . . . . . . . . . 30 1.5.2 Background on Inter-cell Interference Coordination

(ICIC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 1.5.3 Enhanced Inter-cell Interference Coordination

(EICIC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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1.5.4 Defining the CRE Region . . . . . . . . . . . . . . . . . . . . . . 35 1.5.5 Enhancements: eICIC with CA . . . . . . . . . . . . . . . . . . 37

1.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

2 Evolution and Trends of Broadband Access Technologies and Fiber-Wireless Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Yiran Ma and Zhensheng Jia 2.1 Traffic Trend. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 2.2 Technologies of Broadband Access Networks . . . . . . . . . . . . . . 45

2.2.1 Broadband Wireline Access Networks. . . . . . . . . . . . . 45 2.2.2 Broadband Wireless Access Networks. . . . . . . . . . . . . 60

2.3 Fiber-Wireless Convergence and Technology Evolution . . . . . . . 69 2.3.1 Fiber-Based Distributed Antenna Systems (DASs) . . . 69 2.3.2 Ultra-High-Speed Fiber-Wireless Transmission . . . . . . 70 2.3.3 Fiber-Wireless for Backhaul and the Fronthaul

of HetNet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 2.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

3 The Benefits of Convergence Through Fiber-Wireless Integration and Networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 Gee-Kung Chang and Lin Cheng 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 3.2 Convergence of Architectures . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

3.2.1 Centralization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 3.2.2 Resource Sharing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

3.3 Convergence of Links. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.3.1 Mobile Backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.3.2 Mobile Midhaul and Fronthaul . . . . . . . . . . . . . . . . . . 87

3.4 Convergence of Bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 3.4.1 All-Band Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 3.4.2 MMW Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Part II Novel Systems/Subsystems for Fi-Wi Networks

4 Analog and Digitized Radio-over-Fiber . . . . . . . . . . . . . . . . . . . . . . . 99 Maurice Gagnaire 4.1 Existing Radio Cellular Networks. . . . . . . . . . . . . . . . . . . . . . . . 100 4.2 A-RoF Versus Baseband-over-Fiber . . . . . . . . . . . . . . . . . . . . . . 102

4.2.1 Option 1: RF-Modulated Signals . . . . . . . . . . . . . . . . . 103 4.2.2 Option 2: IF Modulated Signals . . . . . . . . . . . . . . . . . 103 4.2.3 Option 3: Baseband-over-Fiber . . . . . . . . . . . . . . . . . . 104 4.2.4 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

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4.3 Transmission of Microwave Signals on Optical Fibers . . . . . . . . 104 4.3.1 Intensity Modulation (IM) and Direct Detection

(DD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.3.2 External Modulation and Direct Detection

(EM-DD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 4.3.3 Photo-detector-Based Heterodyning (HE) with

Direct Detection (HE-DD) . . . . . . . . . . . . . . . . . . . . . . 107 4.3.4 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

4.4 Analog Radio-over-Fiber (A-RoF) . . . . . . . . . . . . . . . . . . . . . . . 109 4.4.1 A-RoF for “RF-over-Fiber” . . . . . . . . . . . . . . . . . . . . . 110 4.4.2 A-RoF for “IF-over-Fiber”. . . . . . . . . . . . . . . . . . . . . . 111 4.4.3 A-RoF for Multi-antennas Sites by Means

of Sub-carrier Multiplexing (SCM) . . . . . . . . . . . . . . . 112 4.4.4 A-RoF for Multi-antennas Sites by Means

of Wavelength-Division Multiplexing (WDM) . . . . . . 114 4.5 Digitized Radio-over-Fiber (D-RoF) . . . . . . . . . . . . . . . . . . . . . . 117

4.5.1 Band-pass Sampling Theory . . . . . . . . . . . . . . . . . . . . 118 4.5.2 D-RoF for a Single-Antenna Site. . . . . . . . . . . . . . . . . 120 4.5.3 D-RoF for a Multiple-Antenna Site . . . . . . . . . . . . . . . 122

4.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

5 Overview of Standardization for D-RoF . . . . . . . . . . . . . . . . . . . . . . 127 Silvano Frigerio, Alberto Lometti and Vincenzo Sestito 5.1 CPRI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

5.1.1 Specification Overview . . . . . . . . . . . . . . . . . . . . . . . . 129 5.1.2 System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 5.1.3 Main Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 5.1.4 Interface Description . . . . . . . . . . . . . . . . . . . . . . . . . . 131 5.1.5 CPRI Compression and CPRI Throughput

Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 5.2 OBSAI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

5.2.1 OBSAI Specifications Status . . . . . . . . . . . . . . . . . . . . 139 5.2.2 System Architecture Overview . . . . . . . . . . . . . . . . . . 139 5.2.3 RP3-01 Insight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 5.2.4 CPRI Versus OBSAI RP3-01 . . . . . . . . . . . . . . . . . . . 145

5.3 D-RoF Transport Over Optical Networks . . . . . . . . . . . . . . . . . . 146 5.3.1 CPRI Over OTN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.3.2 Viable Network Applications for CPRI Over

WDM/OTN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 5.4 ORI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 5.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

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6 Wireless Delivery of over 100 Gb/s mm-Wave Signal in the W-band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Jianjun Yu 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 6.2 Approaches for the Realization of Large Capacity

(>100 Gb/s) Fiber Wireless Integration System . . . . . . . . . . . . . 160 6.2.1 Optical PDM Combined with MIMO Reception . . . . . 161 6.2.2 Advanced Multi-level Modulation . . . . . . . . . . . . . . . . 166 6.2.3 Optical Multi-carrier Modulation . . . . . . . . . . . . . . . . . 169 6.2.4 Electrical Multi-carrier Modulation . . . . . . . . . . . . . . . 173 6.2.5 Antenna Polarization Multiplexing . . . . . . . . . . . . . . . 175 6.2.6 Multi-band Multiplexing . . . . . . . . . . . . . . . . . . . . . . . 178

6.3 Problems Existing in the Large Capacity Fiber Wireless Integration System and Corresponding Solutions . . . . . . . . . . . . 182 6.3.1 Wireless Multi-path Effects Due to Different

Wireless Transmission Distances . . . . . . . . . . . . . . . . . 182 6.3.2 Advance Algorithms Based on DSP . . . . . . . . . . . . . . 184

6.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

7 Systems Challenges for SDN in Fiber Wireless Networks . . . . . . . . 189 Neda Cvijetic and Ting Wang 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 7.2 System-Level Fiber Wireless Network Challenges . . . . . . . . . . . 192

7.2.1 Signaling Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 7.2.2 Network Densification . . . . . . . . . . . . . . . . . . . . . . . . . 194 7.2.3 Network Topology. . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

7.3 SDN-Based Control Plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 7.3.1 SDN-Based Control in Fiber Wireless Networks . . . . . 198

7.4 Recent Progress in SDN for Fiber Wireless Networks . . . . . . . . 201 7.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Part III Novel Network Architectures for Fi-Wi Networks

8 Architectural Evolution and Novel Design of Fiber-Wireless Access Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 Cheng Liu 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 8.2 Overview of Existing Fiber-Wireless Access Architectures. . . . . 215

8.2.1 Macrocell and Small Cell with Fiber-Optic Backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

8.2.2 Distributed Antenna System . . . . . . . . . . . . . . . . . . . . 219 8.2.3 Cloud Radio Access Network (C-RAN) . . . . . . . . . . . 221

8.3 Novel Cloud Radio-Over-Fiber Access Architecture. . . . . . . . . . 224

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8.3.1 Generic Cloud-RoF Architecture and Operational Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

8.3.2 Reconfigurable Cloud-RoF Architecture with WDM Techniques . . . . . . . . . . . . . . . . . . . . . . . . 226

8.3.3 Multi-Service Delivery Including Future- Proof Millimeter-Wave Services . . . . . . . . . . . . . . . . . 228

8.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

9 Advanced Architectures for PON Supporting Fi-Wi Convergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Georgios Ellinas, Kyriakos Vlachos, Chrysovalanto Christodoulou and Mohamed Ali 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 9.2 Backhauling Wireless Traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 9.3 Passive Optical Network (PON): Standards

and Technology Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 9.4 Technology Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

9.4.1 TDM-PON. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 9.4.2 WDM-PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 9.4.3 OFDM-PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 9.4.4 Hybrid PONs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

9.5 PON Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 9.5.1 GPON/EPON. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

9.6 10G-PON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 9.7 10G-Epon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

9.7.1 NG-PON2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 9.7.2 Evolution Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

9.8 Challenges in PON Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 9.9 Distributed Ring-Based WDM-PON Architecture . . . . . . . . . . . . 251 9.10 Architecture Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 9.11 Allocation of Network Resources . . . . . . . . . . . . . . . . . . . . . . . . 255

9.11.1 Dynamic Bandwidth Allocation. . . . . . . . . . . . . . . . . . 256 9.11.2 Upstream Traffic Flows Rerouting and Sharing . . . . . . 256

9.12 Wavelength Assignment/Sharing for Downstream Traffic . . . . . . 257 9.13 Fault Detection and Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . 257

9.13.1 Fault Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 9.13.2 Fault Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

9.14 Fronthauling Mobile Traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 9.15 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

Contents xvii

10 BBU Hotelling in Centralized Radio Access Networks . . . . . . . . . . . 265 Nicola Carapellese, M. Shamsabardeh, Massimo Tornatore and Achille Pattavina 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 10.2 Mobile Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 10.3 Evolving the Base Station: BBU and RRH. . . . . . . . . . . . . . . . . 267 10.4 Advantages of BBU Hotelling . . . . . . . . . . . . . . . . . . . . . . . . . . 268

10.4.1 Cost Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 10.4.2 Energy Savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 10.4.3 Improved Radio Performance . . . . . . . . . . . . . . . . . . . 269

10.5 Challenges of BBU Hotelling: Fronthaul . . . . . . . . . . . . . . . . . . 270 10.5.1 High, Constant Bitrate . . . . . . . . . . . . . . . . . . . . . . . . . 270 10.5.2 Maximum End-to-End Latency . . . . . . . . . . . . . . . . . . 271 10.5.3 Strict QoS Requirements . . . . . . . . . . . . . . . . . . . . . . . 273

10.6 RAN Architectures Based on BBU Hotelling . . . . . . . . . . . . . . . 273 10.6.1 Classification on BBU Placement . . . . . . . . . . . . . . . . 274 10.6.2 Classification on Fronthaul Transport . . . . . . . . . . . . . 276 10.6.3 Classification on BBU Implementation . . . . . . . . . . . . 278

10.7 An FMC Network Architecture for BBU Hotelling . . . . . . . . . . 280 10.7.1 General Network Architecture . . . . . . . . . . . . . . . . . . . 280 10.7.2 BBU Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 10.7.3 Traffic Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282

10.8 The BPTR Optimization Problem . . . . . . . . . . . . . . . . . . . . . . . . 283 10.9 A Heuristic Greedy Algorithm for BPTR . . . . . . . . . . . . . . . . . . 284

10.9.1 Notation and Input Data . . . . . . . . . . . . . . . . . . . . . . . 284 10.9.2 Heuristic Subroutines. . . . . . . . . . . . . . . . . . . . . . . . . . 285 10.9.3 Heuristic Scheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286

10.10 A Case Study for the BPTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 10.11 Conclusion and Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

11 Rethink Ring and Young: Green and Soft RAN for 5G. . . . . . . . . . 293 Chih-Lin I, Jinri Huang, Ran Duan, Gang Li and Chunfeng Cui 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 11.2 No More Cells: One Key 5G Vision . . . . . . . . . . . . . . . . . . . . . 294 11.3 Cloud RAN: The Key Enablers to NMC . . . . . . . . . . . . . . . . . . 296

11.3.1 The Concept of C-RAN. . . . . . . . . . . . . . . . . . . . . . . . 296 11.3.2 C-RAN Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 11.3.3 Advantages of C-RAN . . . . . . . . . . . . . . . . . . . . . . . . 299

11.4 Challenges and Potential Solutions for C-RAN Realization . . . . 299 11.4.1 Challenges on Transport Networks for

Centralization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 11.4.2 Potential Fronthaul Solutions . . . . . . . . . . . . . . . . . . . . 300 11.4.3 Challenges on Virtualization Implementation

to Realize Resource Cloudification . . . . . . . . . . . . . . . 302

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11.5 Recent Progress on C-RAN from China Mobile . . . . . . . . . . . . . 304 11.5.1 Field Trials on Centralization with Different

FH Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 11.5.2 Exploitation of C-RAN Virtualization . . . . . . . . . . . . . 307

11.6 Evolving Toward 5G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 11.6.1 C-RAN to Enable Key 5G Technologies. . . . . . . . . . . 310 11.6.2 Rethink CPRI: CPRI Redefinition . . . . . . . . . . . . . . . . 311 11.6.3 Edge Application on C-RAN. . . . . . . . . . . . . . . . . . . . 313

11.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

Part IV Novel Management Strategies for Fi-Wi Networks

12 Next-Generation PoP with Functional Convergence Redistributions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 Philippe Bertin, Tahar Mamouni and Stéphane Gosselin 12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 12.2 What Services at the Network Edge? . . . . . . . . . . . . . . . . . . . . . 321

12.2.1 Virtual Residential Gateway . . . . . . . . . . . . . . . . . . . . 322 12.2.2 Broadband Network Gateway . . . . . . . . . . . . . . . . . . . 324 12.2.3 Distributed Evolved Packet Core . . . . . . . . . . . . . . . . . 326 12.2.4 Highly Distributed Content Delivery Networks . . . . . . 328

12.3 The Path Toward Fixed and Mobile Convergence . . . . . . . . . . . 329 12.3.1 Converged Subscriber Data and Session

Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 12.3.2 Universal Access Gateway . . . . . . . . . . . . . . . . . . . . . 331

12.4 Implementing the NG PoP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 12.4.1 Design Principles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 12.4.2 Dimensioning the NG PoP . . . . . . . . . . . . . . . . . . . . . 334

12.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336

13 Coordinated Multi-point (CoMP) Systems. . . . . . . . . . . . . . . . . . . . . 337 Yizhuo Yang, Christina Lim and Ampalavanapillai Nirmalathas 13.1 Introduction on CoMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 13.2 Requirements on the Backhaul Network . . . . . . . . . . . . . . . . . . . 339

13.2.1 Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 13.2.2 Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 13.2.3 Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

13.3 Backhaul Architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 13.3.1 GROW-Net Architecture . . . . . . . . . . . . . . . . . . . . . . . 342 13.3.2 FUTON Prototype . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 13.3.3 Adaptive Photonics-Aided CoMP for MMW

Small Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 13.3.4 Converged Fiber–Wireless Architecture. . . . . . . . . . . . 349

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13.4 Fiber–Wireless Integration Schemes Enabling CoMP . . . . . . . . . 350 13.4.1 BS Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350 13.4.2 Performance Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 352 13.4.3 Implementation of CoMP . . . . . . . . . . . . . . . . . . . . . . 354 13.4.4 Experimental Demonstration . . . . . . . . . . . . . . . . . . . . 355

13.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357

14 Converged Wireless Access/Optical Metro Networks in Support of Cloud and Mobile Cloud Services Deploying SDN Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 Anna Tzanakaki, Markos Anastasopoulos, Bijan Rofoee, Shuping Peng, George Zervas, Reza Nejabati, Dimitra Simeonidou, Giada Landi, Giacomo Bernini, Roberto Monno, Nicola Ciulli, Gino Carrozzo, Kostas Katsalis, Thanasis Korakis, Leandros Tassiulas, Georgios Dimosthenous, Dora Christofi, Jordi Ferrer Riera, Eduard Escalona, Jacopo Pianigiani, Dirk Van Den Borne and Gert Grammel 14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360 14.2 Existing Technology Solutions Supporting Cloud

and Mobile Cloud Services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 14.2.1 Physical Infrastructure Solutions

Supporting Cloud Services . . . . . . . . . . . . . . . . . . . . . 362 14.2.2 Infrastructure Management . . . . . . . . . . . . . . . . . . . . . 363 14.2.3 Service Provisioning . . . . . . . . . . . . . . . . . . . . . . . . . . 365

14.3 Proposed Converged Network Architecture . . . . . . . . . . . . . . . . 366 14.3.1 Vision and Architectural Approach . . . . . . . . . . . . . . . 366 14.3.2 Physical Infrastructure Layer . . . . . . . . . . . . . . . . . . . . 369 14.3.3 Infrastructure Management . . . . . . . . . . . . . . . . . . . . . 371 14.3.4 Virtual Infrastructure Control Layer. . . . . . . . . . . . . . . 373 14.3.5 Converged Service Orchestration. . . . . . . . . . . . . . . . . 378

14.4 Architecture Evaluation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 14.4.1 Network Scenario and Related Work. . . . . . . . . . . . . . 379

14.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

Conclusion and Future Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

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Introduction

Abstract Fifth-generation mobile access networks will feature unprecedented performance, not only in terms of higher data rates and lower latencies, but also in terms of the “intelligence” of the network. To achieve these targets, 5G networks will resort to solutions such as small-cell deployment (micro-, femto-, etc.), coor- dinated multi-cell processing (CoMP, eICIC) and centralized/cloud RAN. Such techniques will ultimately burden the optical fiber access/aggregation network needed to backhaul the mobile traffic, as this section of the network will be responsible to serve massive traffic with very strict latency. Hence, the trend toward an actual convergence of fiber and wireless technologies in access/aggregation networks, which has been emerging in the last decade, is expected to gain increased importance, as it indirectly impacts on radio access performance. This book introduces several key enabling techniques for next-generation fiber-wireless con- vergent communication systems in 5G and mobile backhaul networks. The book features fourteen excellent contributions, authored by well-renowned industrial practitioners and academic researchers, in three main thematic areas: system tech- nologies (radio-over-fiber, millimeter-wave transmission, SDN-controlled optical technologies, LTE-advanced), network architectures (TWDM PON, BBU Hotelling, 5G RAN), and network management (SDN-controlled access, CoMP, Next Generation Point of Presence). The focus of various chapters goes beyond the description of state of the art, also presenting the evolutionary paths for fiber- wireless convergence toward 5G implementation.

The overall picture

Mobile traffic growth due to the proliferation of smart mobile devices and band- width demanding applications is accelerating the evolution of radio access networks (RAN) from 2G, 3G, to 4G, and beyond. Looking into the future, 5G wireless technology is on the horizon. The exact definition of 5G is still under active

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discussions, and many research activities are being carried out in both industry and academia. For link spectrum efficiency, the existing wireless technologies have been pushed very close to the Shannon theoretical limit by using higher-level modulation formats (e.g., 64QAM-OFDM), multiple-input and multiple-output (MIMO) techniques, and advanced channel coding schemes (e.g., low-density parity-check (LDPC) and turbo codes). However, there is a great potential in enhancing the system spectrum efficiency. For example, by coordinating adjacent cells to jointly transmit signals to cell-edge users, coordinated multi-point trans- mission (CoMP) [2] can significantly improve the data rate of the users who used to suffer from strong inter-cell interference, thus enhancing the system spectrum efficiency (see Chap. 13). In another dimension, people are always looking for more spectrum, mostly in higher radio frequencies, e.g., exploring the millimeter-wave band [3, 4] (see Chap. 6). Last but not the least, small-cell solutions are being increasingly implemented and are becoming the trend for future wireless commu- nication. By reducing the cell size, limited spectral resources can be reused among cells more frequently, thus enhancing the total system capacity. There are also many discussions on merging WLAN (e.g., Wi-Fi) with cellular small cells to provide a uniform platform for 5G wireless access (see Chap. 2). The main directions of future wireless communications [1] will be overviewed in more detail in Chap. 3.

On the other hand, supporting such techniques will strain the optical fiber-based access/aggregation network that provides the backhaul for the wireless access network. Such “mobile backhaul” or “mobile transport” network will be required to serve the massive traffic amount coming from the mobile users (generated via a plethora of broadband mobile applications) with very strict latency constraints. Hence, the trend toward an actual convergence of fiber and wireless technologies in access/aggregation networks, which has been emerging in the last decade, is expected to have an increased importance, as it indirectly impacts on radio access performance.

In this book, aligned with the directions of future 5G networks, several key enabling technologies, network architectures, and management/control approaches for fiber–wireless convergence for 5G mobile transport networks are introduced.

More importantly, the concept of centralized radio access network (CRAN), as well the associated concept of RAN virtualization (cloud RAN), is comprehensively reviewed in the book. CRAN is a recent solution which radically changes the classical architecture of the RAN. It separates mobile baseband units (BBU) from corresponding Remote Radio Heads (RRH) and consolidates them into common locations, also known as “hotels” (in fact, the paradigm of CRAN is often referred to as BBU hoteling or hosteling). Each BBU/RRH pair exchanges digital radio-over-fiber (D-RoF) data (see Chap. 5), also known as “fronthaul,” obtained from the baseband digitization of radio interface signals (see Chap. 4). Thanks to the sharing of backplanes, power, computational, and maintenance resources of BBUs hosted in the same hotel, a significant amount of OPEX saving can be achieved by adopting this mobile backhauling architecture (see Chap. 10). Moreover, increased coordination will allow to optimize RAN throughput (e.g.,

xxii Introduction

using the previously mentioned CoMP technique, see Chap. 14), and to even move towards more exciting and future-prone CRAN paradigms as the “No More Cells” approach (see Chap. 11). Note that, conventionally, backhaul/fronthaul networks can be based on T1 lines, microwave point-to-point links, and not only fiber links. However, since the backhaul/fronthaul capacity requirement increases drastically as the wireless access techniques evolve, optical fibers are considered as the ultimate transport media to provide sufficient bandwidth as well as future-proof capacity upgrade. In particular, passive optical networks (PONs) are a relevant candidate for mobile backhaul/fronthaul applications (see Chaps. 8 and 9).

In light of the previous discussion, it clearly emerges that the envisioned fiber- wireless-convergent backhaul network will require enhanced “intelligence” in terms of reconfigurability and coordination, among others. To enable such intelligence, research is currently focusing also on the role that software-defined networking (SDN) will play as an enabler for advanced functionalities for fiber-wireless con- vergence (see Chap. 7, for applications of SDN in the next-generation optical access segment, and “Conclusion and Future Topics”, for a proposal of an SDN-controlled fiber-wireless converged network supporting cloud computing services).

Finally, there is increased interest from network operators in leveraging access/aggregation infrastructure for fixed traffic to also perform backhaul/fronthaul of mobile traffic, in a related concept to fiber-wireless convergence, which is typ- ically referred as fixed-mobile convergence (see Chap. 13) [5].

The topic of fiber-wireless convergence is currently an actively researched topic, and clearly it is impossible to cover in this book all the latest progress in the field. Nevertheless, as of today, a comparably comprehensive collection of up-to-date, relevant, and logically organized works on this topic has not been yet made available. The aim of this book in putting together this collection of chapters is to ensure that experienced as well as novice researchers can have a single handy source of reference on this topic. The following chapters do not only cover exciting long-term research proposals originating mostly from academia and research lab- oratories but they also contain the current vision of practitioners working in leading technology vendor and network operator companies.

The intended audience of the book consists of students in academia learning about and doing research on fiber-wireless convergent networks in support of 5G and mobile backhaul networks, industrial practitioners that are evaluating the introduction of these technologies in the design of current 4G network as well as those starting to build a 5G-prone backhaul infrastructure, and faculty members and researchers in academia wishing to teach an advanced course on next-generation network design, or conducting research in the area of fiber–wireless convergence and 5G. The objective of the book is to provide the reader with a comprehensive source of information on this interesting and timely topic that can foster novel ideas and research lines, as well as inspire new ways to go forward and find new solutions for the numerous remaining challenges.

Introduction xxiii

Book Organization

The book is organized into four parts covering different subject areas. Part I (Chaps. 1–3) overviews market and technological trends that motivate the book and dis- cusses the benefits of convergence. An introduction to the evolution of cellular technology toward 5G is also provided for readers that need to catch up with recent trends, especially in LTE. Part II (Chaps. 4–7) focuses on enabling technologies for fiber-wireless convergence. Part III (Chaps. 8–11) deals with rising paradigms for network architectures in the fiber-wireless convergent access/metro network seg- ments, and Part IV (Chaps. 12–14) discusses some challenges in terms of man- agement of a fiber-wireless converged network. In the last chapter of the book, we conclude the book and overview very novel and recent areas of research which have been emerging during the preparation of the book.

Chapter 1 by Ma and Jia provides an introduction to technical trends and market status of both broadband wireline and wireless access networks, and also summa- rizes the current forecasts on technology evolution of fiber-wireless networks. As a useful introduction to technologies discussed throughout the rest of the book, the chapter overviews broadband wireline access networks including xDSL, coaxial cable, and hybrid fiber coax (HFC), and various PON architectures and then moves to broadband wireless access technologies such as Wi-Fi, WiMAX, and mobile cellular systems.

Chapter 2 by Sivarajan and Mohapatra presents in a comprehensive manner the foundational concepts of the design principles used in LTE-A radio access net- works, such as bandwidth aggregation, transmission diversity, interference man- agement, and MIMO spatial diversity. These concepts are instrumental to the entire book as they provide a clear technical roadmap to the 5G technologies.

Chapter 3 by Chang and Cheng introduces the concept of multi-tier radio access network (RAN) combining the strength of fiber-optic and radio access technologies. This concept, which will be complemented by the specific contributions in the rest of the book, employs adaptive microwave photonics interfaces and radio-over-fiber (RoF) techniques for future heterogeneous wireless communications. Coexistence of current and future mobile network standards such as 4G and 5G with optimized and continuous cell coverage using multi-tier RoF, regardless of the underlying network topology or protocol, is also discussed.

Chapter 4 by Gagnaire overviews the basic principles, drawbacks, and benefits of the various analog- and digital radio-over-fiber techniques currently available, by providing a detailed state-of-the-art picture of the level of advancement of these two techniques. These techniques are a key for the implementation of the signal transport in the CRAN architectures. A detailed overview of the current RoF options provides a useful insight on the transmission technologies that support the communication between RRH and BBU in CRAN.

Chapter 5 by Frigerio, Lometti, and Sestito introduces the reader to the current standardization activities related to D-RoF, namely those relative to the definition of the digital interface between radio units and base stations (CPRI, OBSAI, ORI)

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Anis Shallouf
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and those aimed at allowing for the transport of such interfaces over a geographical network. The latest aspect is specifically important in view of the modern CRAN paradigm.

Chapter 6 by Yu summarizes several different approaches for the realization of large capacity (>100Gb/s) fiber-wireless integrated systems, including optical polarization-division-multiplexing (PDM) combined with MIMO reception, advanced multi-level and multi-carrier modulation, antenna polarization multi- plexing, and multi-band multiplexing. These spectral efficient modulation and multiplexing techniques are important for providing high-speed, high-capacity, free space transmission links as an alternative to fiber based mobile backhaul and fronthaul systems to overcome difficult terrains or fiber-cut.

Chapter 7 by Cvijetic and Wang introduces the reader to system-level challenges for SDN in fiber-wireless networks, including important aspects from both the control and data plane perspectives. The requirements for and ramifications of SDN-based control in fiber-wireless networks are examined, and a survey of recent research and development advances in SDN for fiber-wireless (at both the system and network levels) is also presented.

Chapter 8 by Liu reviews several existing and emerging fiber-wireless access networks including macrocells, small cells, distributed antenna systems, and cloud RAN. A novel cloud radio-over-fiber access network is subsequently introduced as a promising fiber-wireless convergent access architecture for future 5G networks. Proof-of-concept experiments are presented to demonstrate multi-operator/ multi-service infrastructure-sharing capabilities in the cloud-RoF systems.

Chapter 9 by Ellinas et al., reviews passive optical network (PON) architectures as it is generally accepted that fiber deployment to cell towers is the only future-proof solution to build mobile backhauls, which will scale to the increased capacity requirements of future NG-WBAN technologies. Further, among the optical network architectures, PONs meet the needs for such a high-capacity access architecture. Different PON technologies, including TDM-PON, WDM-PON, OFDM-PON, and hybrid TDM-WDM, OFDM-WDM co-designs are described, followed by PON technology standards (GPON/EPON, 10G-PON, 10G-EPON, NG-PON2) and evolutionary scenarios. A novel fully distributed ring-based WDM-PON architecture is subsequently introduced as a promising access archi- tecture that not only enables the support of a converged 4G/5G mobile infrastructure but also supports distributed network control as well as management operations.

Chapter 10 by Carapellese, Shamsabardeh, Tornatore, and Pattavina focuses on the role of BBU hoteling in fiber-wireless converged architectures. A classification of the various architectural solutions for BBU hoteling is given, regarding BBU placement and implementation, and fronthaul transport. The authors introduce a novel network optimization problem, namely the BPTR (BBU Placement and Traffic Routing) problem, which addresses the questions of “how and where to place the BBUs” so as to minimize the number of hotels or the transport capacity of the network.

Chapter 11 by I, Huang, Duan, Li, and Cui follows a different, evolutionary approach for 5G systems termed “No More Cells” (NMC). NMC transfers the

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traditional cell-centric network design to a user-centric design principle. It is pointed out that NMC realization could be facilitated by the CRAN architecture, which is demonstrated and verified through extensive field trials.

Chapter 12 by Bertin, Mamouni, and Gosselin discusses how to realize con- vergence in the framework of the Next Generation Point of Presence (NG PoP). The NG PoP is a new concept of a flexible platform in the telecom network hierarchy that combines aggregation of fixed and mobile access traffic, IP edge routing, and the ability of hosting additional network functions and services. In addition, two more essential concepts in the path towards convergence are intro- duced, namely the converged subscriber data and session management and the universal access gateway.

Chapter 13 by Yang, Lim, and Nirmalathas provides a brief introduction on the cooperative multiple point (CoMP) technologies and the backhaul requirements for enabling CoMP techniques in LTE-A. The CoMP backhaul architectures and CRAN configurations based on various RoF technologies are also presented.

Chapter 14 authored by several of the researchers working on the EU project CONTENT proposes a next-generation converged infrastructure to support fixed and mobile cloud computing services. The proposed infrastructure facilitates effi- cient and seamless interconnection of fixed and mobile end users to computational resources through a fiber-wireless convergent network. The proposed architecture is well aligned and fully compliant with current SDN paradigms.