Open RAN Explained: The New Era of Radio Networks

Open RAN EXPLAINED A pioneering outline of the concepts that enhance 5G capabilities to revolutionize the telecommunications industry. Open radio-access network, or Open RAN, is a type of network architecture in which baseband and radio unit components from different suppliers can operate seamlessly in concert. Advances in network communication were, until recently, hampered by the proprietary network operations of each mobile operator; the advent of 5G, however, with its service-based architecture model, has finally opened the door to the expansion of connectivity on the Open RAN model. This transformation promises to define the future of mobile network architecture. Open RAN Explained is among the first books dedicated to this groundbreaking technology. Its comprehensive but accessible summary of current and future developments in Open RAN promises to facilitate network deployment and device design, as well as to provide a handy reference for network professionals in a range of different fields. The result is a must-read volume for anyone looking to understand the future of wireless communication. Open RAN Explained readers will also find: In-depth description of the challenges and opportunities of network modularization Analysis conversant with the latest release specifications of the O-RAN Allliance, GSMA OP/TIP, and other key emerging technologies Authors working at the leading edge of 5G network communications Open RAN Explained is ideal for network operators, network element and device manufacturers, telecommunications researchers, and advanced students, as well as industry-adjacent figures such as regulators, consultants, and marketing professionals.

Table of Contents:
Author Biographies xiii Preface xv Acknowledgments xix Abbreviations xxi 1 Introduction 1 1.1 Overview 1 1.2 Readiness of the Ecosystem 2 1.2.1 Virtualization 2 1.2.2 Industry Forums 3 1.2.3 Statistics 4 1.2.4 Path Toward Open RAN Networks 5 1.2.5 Security Aspects 7 1.2.6 Commercial Deployments 7 1.3 Focus and Contents 7 References 9 2 Open RAN: Journey from Concept to Development 11 2.1 Overview 11 2.2 Requirements 11 2.3 Standards 12 2.3.1 3GPP 12 2.3.2 O-RAN Alliance 14 2.3.3 Telecom Infra Project 18 2.3.4 Collaboration of Organizations 22 2.4 Open Source and Open RAN 23 References 25 3 Evolution of the RAN 27 3.1 Architecture of a Mobile Communications System 27 3.1.1 System-Level Overview 27 3.1.2 User Equipment 27 3.1.3 Radio Access Network 28 3.1.4 Core Network 29 3.2 Components and Structure of the RAN 29 3.2.1 The Radio Base Station 29 3.2.2 RAN Service Area 30 3.3 RAN Enhancements from Early Mobile System to 4G 33 3.3.1 Introduction 33 3.3.2 RAN Key Performance Indicators 34 3.3.3 Early Mobile System Radio Access Networks 34 3.3.4 The Evolved Universal Terrestrial Radio Access Network 35 3.3.4.1 Baseband Unit and Remote Radio Head Split 36 3.3.4.2 Fronthaul Protocol Evolution 36 3.3.4.3 X2 Interface Between Base Stations 37 3.3.4.4 User Plane Control Plane Separation 38 3.4 Role of Information Technology in the Evolution of the RAN in 5G and Open RAN 40 3.4.1 Introduction 40 3.4.2 Virtualization 40 3.4.3 Cloudification 42 3.4.4 Software-defined Networking 44 3.5 RAN Evolution in 5G 46 3.5.1 The Next-Generation Radio Access Network 46 3.5.2 gNB Split Architecture 47 3.5.2.1 Rationale for Split Architecture 47 3.5.2.2 Split Architecture Topology Options 49 3.5.3 Fronthaul Evolution: eCPRI 50 3.6 Evolution of the Base Station Architecture 52 3.6.1 Overview 52 3.6.2 Distributed RAN 52 3.6.3 Centralized RAN 53 3.6.4 Virtualized RAN (vRAN) 55 3.6.4.1 Concept 55 References 56 4 O-RAN Alliance Architecture 59 4.1 High-Level Objectives of the O-RAN Alliance Architecture 59 4.2 O-RAN Alliance Work on 4G 59 4.2.1 Laying the Ground for a Multi-vendor Environment 59 4.2.2 Standalone and Non-standalone 5G 60 4.2.3 The O-eNB and 4G Interfaces Profiling 61 4.2.3.1 O-eNB 61 4.2.3.2 X2 and W1 Profiling 62 4.3 O-RAN 5G Architecture 63 4.3.1 Architecture Overview 63 4.3.2 O-RAN Alliance Architecture Network Components 64 4.3.2.1 O-RAN Central Unit (O-CU) 64 4.3.2.2 O-RAN Distributed Unit (O-DU) 64 4.3.2.3 O-RAN Radio Unit (O-RU) 65 4.3.2.4 Service Management and Orchestration Framework 65 4.3.2.5 O-Cloud 65 4.3.2.6 RAN Intelligent Controller 65 4.3.3 Interfaces 65 4.3.3.1 3GPP-Defined Interfaces 65 4.3.3.2 O-RAN Alliance-Defined Interfaces 66 4.4 O-RAN Alliance Architecture Innovation 66 4.4.1 O-RAN Alliance Two-Pronged Approach 66 4.4.2 Open Fronthaul 67 4.4.3 Stricter Approach to RAN Functional Split 67 4.4.3.1 Introduction 67 4.4.3.2 The NG-RAN Radio Resource Management 69 4.4.3.3 Functional Split of the Physical Layer Between O-DU and O-RU 71 4.5 Service Management and Orchestration Framework 74 4.6 O-Cloud 74 4.7 Real-Time Intelligent Controller 77 4.7.1 Non-Real-Time RIC 78 4.7.1.1 Non-Real-Time RIC Architecture Principles 78 4.7.1.2 R1 Services 79 4.7.2 Near-Real-Time RIC 79 4.8 Open Fronthaul 81 4.8.1 Addressing the Technical Challenges of the 5G Fronthaul 81 4.8.2 User Plane and Control Plane 84 4.8.3 Synchronization Plane 84 4.8.4 Management Plane 85 References 85 5 TIP – Commercialization of Open RAN 87 5.1 Overview 87 5.2 Fundamental: Requirements and Test Plans 88 5.2.1 OpenRAN Overview 88 5.2.2 OpenRAN Releases 89 5.2.2.1 Overview of OpenRAN Releases 89 5.2.2.2 RU 90 5.2.2.3 DU/CU 91 5.2.2.4 RIA 92 5.2.2.5 SMO 93 5.3 Testing and Validation, Marketplace 94 5.3.1 Rationale 94 5.3.2 The Process 94 5.3.3 Achievements 95 5.4 Experience of OpenCellular 96 References 97 6 Open RAN Use Cases 99 6.1 Introduction 99 6.2 Open RAN as Enabling Foundation 99 6.2.1 Overview 99 6.2.2 Customer Experience 99 6.2.2.1 QoE Optimization 99 6.2.2.2 Signaling Storm Protection 100 6.2.3 Facilitating 5G Component Technologies 102 6.2.3.1 Overview 102 6.2.3.2 Massive MIMO Beamforming Optimization 102 6.2.3.3 MU-MIMO Optimization 103 6.2.3.4 Traffic Steering 104 6.2.3.5 Dynamic Spectrum Sharing 105 6.2.3.6 Local Indoor Positioning 107 6.2.3.7 Energy Saving 107 6.2.4 Network Slicing 108 6.2.4.1 Overview 108 6.2.4.2 QoS-Based Resource Optimization 108 6.2.4.3 RAN Slice Service Level Assurance 109 6.2.4.4 Multi-vendor Slice 110 6.2.4.5 NSSI Resource Allocation Optimization 112 6.2.5 Network as a Service and RAN Sharing 113 6.2.5.1 NaaS: Concept and Deployment 113 6.2.5.2 Application to RAN Sharing 114 6.2.5.3 Sharing of O-RUs 115 6.3 Connected Mobility 117 6.3.1 Overview 117 6.3.2 Rationale 117 6.3.3 Specific Use Cases 118 6.3.3.1 V2X 118 6.3.3.2 UAV 120 6.3.3.3 Railway Communications 123 6.4 Private Networks 126 6.4.1 Overview 126 6.4.2 Introduction to Private Network 126 6.4.2.1 Definition 126 6.4.2.2 Rationale 127 6.4.3 Role of Open RAN 128 6.4.4 Applications 129 6.4.4.1 Smart City 129 6.4.4.2 Industry 129 6.5 Potential for the Future 130 6.5.1 Key Differentiators of Open RAN Revisited 130 6.5.2 Potential Use Cases 130 References 131 7 Open RAN Security Aspects 135 7.1 General 135 7.2 User Equipment 135 7.2.1 SIM 135 7.2.2 Device 136 7.3 Current Security Landscape 136 7.3.1 Overview 136 7.3.2 Open RAN Work on Security 137 7.3.2.1 Context and O-RAN Specifications 137 7.3.2.2 O-RAN Security Requirements 138 7.3.2.3 O-RAN Security Protocols Specification 139 7.3.2.4 O-RAN Security Threat Modeling and Remediation Analysis 140 7.3.2.5 O-RAN Study on Security for O-Cloud 140 7.3.2.6 O-RAN Study on Security for Application Lifecycle Management 142 7.3.2.7 O-RAN Study on Security Log Management 143 7.3.2.8 O-RAN Study on Security for Service Management and Orchestration 143 7.3.2.9 O-RAN Study on Security for Shared O-RU 144 7.3.2.10 O-RAN Study on Security for Near-Real-Time RIC and xApps 145 7.3.2.11 Complementing Material 146 7.3.3 Industry and Government Entities 147 7.3.3.1 Open RAN MoU 147 7.3.3.2 NIS 147 7.3.3.3 EU 147 7.3.3.4 FCC 147 7.4 New Threats 149 7.4.1 Overview 149 7.4.2 Machine Learning 149 7.4.3 Open Interfaces 150 7.4.4 Open-Source SW 150 7.4.5 Supply Chain 151 7.4.6 Misconfiguration 152 7.4.7 Low Product Quality 152 7.4.8 Lack of Access Controls 152 7.4.9 Other Risks 153 7.5 O-RAN Interface Protection Aspects 154 7.5.1 General 154 7.5.2 Protection of Interfaces 154 7.5.3 Mutual Authentication 154 7.5.4 Security Aspects for Near-Real-Time RIC 155 7.5.5 Security Aspects of Non-Real-Time RIC 156 7.5.6 Trusted Certificate Authorities 156 References 157 8 Open RAN Deployment Considerations 161 8.1 The Evolution of the RAN Deployment Strategy 161 8.2 Analysis of the Functional Split of the Base Station and Performance 164 8.2.1 Need for Multiple Splits 164 8.2.2 High-Level Split – Option 2 164 8.2.3 O-RAN Alliance Split 7-2x 165 8.2.4 Small Cell Split 165 8.2.5 Low-Level Split – Option 8 166 8.3 Service-Based Planning Aspects 166 8.3.1 New 5G Services and Planning 166 8.3.2 Challenge of Operators 167 8.3.2.1 General 167 8.3.2.2 Multi-vendor Integration 167 8.3.2.3 Cost Challenges 168 8.3.2.4 Performance 169 8.3.2.5 Skillset and Experience 169 8.3.3 Challenge of Vendors 170 8.3.4 Considerations in Brownfield and Greenfield Scenarios 171 8.3.4.1 Brownfield Deployment 171 8.3.4.2 Greenfield Deployment 172 8.4 Testing and Measurements 173 8.4.1 General 173 8.4.2 New Methods and Challenges in Open RAN Testing 176 8.4.3 Conformance and Interoperability Testing 178 8.4.3.1 General 178 8.4.3.2 Case Study: DoCoMo 179 8.4.3.3 Case Study: Vodafone 180 8.4.3.4 Recommendations from the Field 181 8.4.4 Test Laboratories 181 8.4.5 Testing and Open RAN Multi-vendor Integration 182 8.4.5.1 General 182 8.4.5.2 Open RU Testing 183 8.4.5.3 Open DU Testing 183 8.4.5.4 Open CU Testing 184 8.4.5.5 Open RIC Testing 184 8.4.6 Other Measurement Considerations 184 8.5 Optimization 184 8.5.1 Traditional Optimization and New Technologies 184 8.5.2 AI/ML in Open RAN 185 8.5.3 Open RAN and Evolution Toward AI-native Network 186 8.6 Transition to Open RAN 188 8.6.1 The Path to an Open RAN Compliant Network 188 8.6.2 Coexistence of Deployed RAN with Open RAN Components 189 8.6.3 Multi-vendor RAN 191 8.6.4 Open RAN Equipment Lifecycle 191 8.6.5 Open RAN Performance 192 8.7 Moving Toward the Future Access Agnostic Network: Nonterrestrial Open RAN Scenarios 192 8.7.1 General 192 8.7.2 Frontend 192 8.7.3 Polarization 193 8.7.4 MIMO 193 8.7.5 Open RAN in Satellite Communications 194 8.7.5.1 NG-RAN Impacts, Transparent Satellite 195 8.7.5.2 NG-RAN Impacts, gNB Processed Payload 195 8.7.5.3 Impacts of the Open RAN 195 8.7.5.4 Impacts on Measurements 196 References 196 Index 199

About the Author :
Jyrki T. J. Penttinen is Senior Technology Manager, North America, GSMA. He has worked in mobile telecommunication since 1994. Since then, he has worked with Nokia and Giesecke+Devrient Mobile Security, and has experience in research and operational activities for both radio and core network domains, including planning, optimization, measurements, system architectures, and services. He is currently focusing on 5G, designing guidelines for the North American and Caribbean mobile network operators. Michele Zarri is an independent management consultant. He started his career in Fujitsu R&D working on layer 1 of WCDMA before moving to Deutsche Telekom representing the company in 3GPP. Michele served two terms as 3GPP TSG SA WG1 chairman and has been rapporteur of several specifications and work items. In 2015, Michele joined the GSMA as technical director of the 5G projects. Dongwook Kim is Specifications Manager of the 3GPP, the secretary of 3GPP CT3 working group, and the work plan coordinator of 3GPP TSG CT. He has worked in the industry for 11 years and his past employers include Korea Telecom (KT), GSM Association (GSMA), and Telecom Infra Project (TIP). His career has focused on promoting latest telecom technologies and serving as the industry think tank.