Open RAN Explained

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.

• Author Biographies xiiiPreface xvAcknowledgments xixAbbreviations xxi1 Introduction 11.1 Overview 11.2 Readiness of the Ecosystem 21.2.1 Virtualization 21.2.2 Industry Forums 31.2.3 Statistics 41.2.4 Path Toward Open RAN Networks 51.2.5 Security Aspects 71.2.6 Commercial Deployments 71.3 Focus and Contents 7References 92 Open RAN: Journey from Concept to Development 112.1 Overview 112.2 Requirements 112.3 Standards 122.3.1 3GPP 122.3.2 O-RAN Alliance 142.3.3 Telecom Infra Project 182.3.4 Collaboration of Organizations 222.4 Open Source and Open RAN 23References 253 Evolution of the RAN 273.1 Architecture of a Mobile Communications System 273.1.1 System-Level Overview 273.1.2 User Equipment 273.1.3 Radio Access Network 283.1.4 Core Network 293.2 Components and Structure of the RAN 293.2.1 The Radio Base Station 293.2.2 RAN Service Area 303.3 RAN Enhancements from Early Mobile System to 4G 333.3.1 Introduction 333.3.2 RAN Key Performance Indicators 343.3.3 Early Mobile System Radio Access Networks 343.3.4 The Evolved Universal Terrestrial Radio Access Network 353.3.4.1 Baseband Unit and Remote Radio Head Split 363.3.4.2 Fronthaul Protocol Evolution 363.3.4.3 X2 Interface Between Base Stations 373.3.4.4 User Plane Control Plane Separation 383.4 Role of Information Technology in the Evolution of the RAN in 5G and Open RAN 403.4.1 Introduction 403.4.2 Virtualization 403.4.3 Cloudification 423.4.4 Software-defined Networking 443.5 RAN Evolution in 5G 463.5.1 The Next-Generation Radio Access Network 463.5.2 gNB Split Architecture 473.5.2.1 Rationale for Split Architecture 473.5.2.2 Split Architecture Topology Options 493.5.3 Fronthaul Evolution: eCPRI 503.6 Evolution of the Base Station Architecture 523.6.1 Overview 523.6.2 Distributed RAN 523.6.3 Centralized RAN 533.6.4 Virtualized RAN (vRAN) 553.6.4.1 Concept 55References 564 O-RAN Alliance Architecture 594.1 High-Level Objectives of the O-RAN Alliance Architecture 594.2 O-RAN Alliance Work on 4G 594.2.1 Laying the Ground for a Multi-vendor Environment 594.2.2 Standalone and Non-standalone 5G 604.2.3 The O-eNB and 4G Interfaces Profiling 614.2.3.1 O-eNB 614.2.3.2 X2 and W1 Profiling 624.3 O-RAN 5G Architecture 634.3.1 Architecture Overview 634.3.2 O-RAN Alliance Architecture Network Components 644.3.2.1 O-RAN Central Unit (O-CU) 644.3.2.2 O-RAN Distributed Unit (O-DU) 644.3.2.3 O-RAN Radio Unit (O-RU) 654.3.2.4 Service Management and Orchestration Framework 654.3.2.5 O-Cloud 654.3.2.6 RAN Intelligent Controller 654.3.3 Interfaces 654.3.3.1 3GPP-Defined Interfaces 654.3.3.2 O-RAN Alliance-Defined Interfaces 664.4 O-RAN Alliance Architecture Innovation 664.4.1 O-RAN Alliance Two-Pronged Approach 664.4.2 Open Fronthaul 674.4.3 Stricter Approach to RAN Functional Split 674.4.3.1 Introduction 674.4.3.2 The NG-RAN Radio Resource Management 694.4.3.3 Functional Split of the Physical Layer Between O-DU and O-RU 714.5 Service Management and Orchestration Framework 744.6 O-Cloud 744.7 Real-Time Intelligent Controller 774.7.1 Non-Real-Time RIC 784.7.1.1 Non-Real-Time RIC Architecture Principles 784.7.1.2 R1 Services 794.7.2 Near-Real-Time RIC 794.8 Open Fronthaul 814.8.1 Addressing the Technical Challenges of the 5G Fronthaul 814.8.2 User Plane and Control Plane 844.8.3 Synchronization Plane 844.8.4 Management Plane 85References 855 TIP – Commercialization of Open RAN 875.1 Overview 875.2 Fundamental: Requirements and Test Plans 885.2.1 OpenRAN Overview 885.2.2 OpenRAN Releases 895.2.2.1 Overview of OpenRAN Releases 895.2.2.2 RU 905.2.2.3 DU/CU 915.2.2.4 RIA 925.2.2.5 SMO 935.3 Testing and Validation, Marketplace 945.3.1 Rationale 945.3.2 The Process 945.3.3 Achievements 955.4 Experience of OpenCellular 96References 976 Open RAN Use Cases 996.1 Introduction 996.2 Open RAN as Enabling Foundation 996.2.1 Overview 996.2.2 Customer Experience 996.2.2.1 QoE Optimization 996.2.2.2 Signaling Storm Protection 1006.2.3 Facilitating 5G Component Technologies 1026.2.3.1 Overview 1026.2.3.2 Massive MIMO Beamforming Optimization 1026.2.3.3 MU-MIMO Optimization 1036.2.3.4 Traffic Steering 1046.2.3.5 Dynamic Spectrum Sharing 1056.2.3.6 Local Indoor Positioning 1076.2.3.7 Energy Saving 1076.2.4 Network Slicing 1086.2.4.1 Overview 1086.2.4.2 QoS-Based Resource Optimization 1086.2.4.3 RAN Slice Service Level Assurance 1096.2.4.4 Multi-vendor Slice 1106.2.4.5 NSSI Resource Allocation Optimization 1126.2.5 Network as a Service and RAN Sharing 1136.2.5.1 NaaS: Concept and Deployment 1136.2.5.2 Application to RAN Sharing 1146.2.5.3 Sharing of O-RUs 1156.3 Connected Mobility 1176.3.1 Overview 1176.3.2 Rationale 1176.3.3 Specific Use Cases 1186.3.3.1 V2X 1186.3.3.2 UAV 1206.3.3.3 Railway Communications 1236.4 Private Networks 1266.4.1 Overview 1266.4.2 Introduction to Private Network 1266.4.2.1 Definition 1266.4.2.2 Rationale 1276.4.3 Role of Open RAN 1286.4.4 Applications 1296.4.4.1 Smart City 1296.4.4.2 Industry 1296.5 Potential for the Future 1306.5.1 Key Differentiators of Open RAN Revisited 1306.5.2 Potential Use Cases 130References 1317 Open RAN Security Aspects 1357.1 General 1357.2 User Equipment 1357.2.1 SIM 1357.2.2 Device 1367.3 Current Security Landscape 1367.3.1 Overview 1367.3.2 Open RAN Work on Security 1377.3.2.1 Context and O-RAN Specifications 1377.3.2.2 O-RAN Security Requirements 1387.3.2.3 O-RAN Security Protocols Specification 1397.3.2.4 O-RAN Security Threat Modeling and Remediation Analysis 1407.3.2.5 O-RAN Study on Security for O-Cloud 1407.3.2.6 O-RAN Study on Security for Application Lifecycle Management 1427.3.2.7 O-RAN Study on Security Log Management 1437.3.2.8 O-RAN Study on Security for Service Management and Orchestration 1437.3.2.9 O-RAN Study on Security for Shared O-RU 1447.3.2.10 O-RAN Study on Security for Near-Real-Time RIC and xApps 1457.3.2.11 Complementing Material 1467.3.3 Industry and Government Entities 1477.3.3.1 Open RAN MoU 1477.3.3.2 NIS 1477.3.3.3 EU 1477.3.3.4 FCC 1477.4 New Threats 1497.4.1 Overview 1497.4.2 Machine Learning 1497.4.3 Open Interfaces 1507.4.4 Open-Source SW 1507.4.5 Supply Chain 1517.4.6 Misconfiguration 1527.4.7 Low Product Quality 1527.4.8 Lack of Access Controls 1527.4.9 Other Risks 1537.5 O-RAN Interface Protection Aspects 1547.5.1 General 1547.5.2 Protection of Interfaces 1547.5.3 Mutual Authentication 1547.5.4 Security Aspects for Near-Real-Time RIC 1557.5.5 Security Aspects of Non-Real-Time RIC 1567.5.6 Trusted Certificate Authorities 156References 1578 Open RAN Deployment Considerations 1618.1 The Evolution of the RAN Deployment Strategy 1618.2 Analysis of the Functional Split of the Base Station and Performance 1648.2.1 Need for Multiple Splits 1648.2.2 High-Level Split – Option 2 1648.2.3 O-RAN Alliance Split 7-2x 1658.2.4 Small Cell Split 1658.2.5 Low-Level Split – Option 8 1668.3 Service-Based Planning Aspects 1668.3.1 New 5G Services and Planning 1668.3.2 Challenge of Operators 1678.3.2.1 General 1678.3.2.2 Multi-vendor Integration 1678.3.2.3 Cost Challenges 1688.3.2.4 Performance 1698.3.2.5 Skillset and Experience 1698.3.3 Challenge of Vendors 1708.3.4 Considerations in Brownfield and Greenfield Scenarios 1718.3.4.1 Brownfield Deployment 1718.3.4.2 Greenfield Deployment 1728.4 Testing and Measurements 1738.4.1 General 1738.4.2 New Methods and Challenges in Open RAN Testing 1768.4.3 Conformance and Interoperability Testing 1788.4.3.1 General 1788.4.3.2 Case Study: DoCoMo 1798.4.3.3 Case Study: Vodafone 1808.4.3.4 Recommendations from the Field 1818.4.4 Test Laboratories 1818.4.5 Testing and Open RAN Multi-vendor Integration 1828.4.5.1 General 1828.4.5.2 Open RU Testing 1838.4.5.3 Open DU Testing 1838.4.5.4 Open CU Testing 1848.4.5.5 Open RIC Testing 1848.4.6 Other Measurement Considerations 1848.5 Optimization 1848.5.1 Traditional Optimization and New Technologies 1848.5.2 AI/ML in Open RAN 1858.5.3 Open RAN and Evolution Toward AI-native Network 1868.6 Transition to Open RAN 1888.6.1 The Path to an Open RAN Compliant Network 1888.6.2 Coexistence of Deployed RAN with Open RAN Components 1898.6.3 Multi-vendor RAN 1918.6.4 Open RAN Equipment Lifecycle 1918.6.5 Open RAN Performance 1928.7 Moving Toward the Future Access Agnostic Network: Nonterrestrial Open RAN Scenarios 1928.7.1 General 1928.7.2 Frontend 1928.7.3 Polarization 1938.7.4 MIMO 1938.7.5 Open RAN in Satellite Communications 1948.7.5.1 NG-RAN Impacts, Transparent Satellite 1958.7.5.2 NG-RAN Impacts, gNB Processed Payload 1958.7.5.3 Impacts of the Open RAN 1958.7.5.4 Impacts on Measurements 196References 196Index 199