Comprehensive explorations of Open X-
Table of Contents
List of Contributors xiii
Foreword xv
Preface xvii
About the Authors xix
Definitions / Acronyms xxi
1 The Evolution of RAN 1
Sameh M. Yamany
1.1 Introduction 1
1.2 RAN Architecture Evolution 4
1.2.1 The 2G RAN 5
1.2.2 The 3G RAN 6
1.2.3 The 4G/LTE RAN 6
1.2.4 The 5G RAN 9
1.3 The Case for Open RAN 11
1.4 6G and the Road Ahead 11
1.5 Conclusion 13
Bibliography 13
2 Open RAN Overview 14
Rittwik Jana
2.1 Introduction 14
2.1.1 What is Open RAN and Why is it Important? 17
2.1.2 How Does Open RAN Accelerate Innovation? 17
2.1.3 What are the major challenges that Open RAN can help to address? 18
2.2 Open RAN Architecture 18
2.3 Open RAN Cloudification and Virtualization 19
2.4 RAN Intelligence 20
2.5 Fronthaul Interface and Open Transport 20
2.6 Securing Open RAN 21
2.7 Open Source Software 21
2.8 RAN Automation and Deployment with CI/CD 22
2.9 Open RAN Testing 22
2.10 Industry Organizations 23
2.11 Conclusion 23
Bibliography 23
3 O-RAN Architecture Overview 24
Rajarajan Sivaraj and Sridhar Rajagopal
3.1 Introduction 24
3.1.1 General Description of O-RAN Functions 24
3.1.1.1 Centralized Unit – Control Plane and User Plane Functions (CU-CP and CU-UP) 26
3.1.1.2 Distributed Unit Function (DU) 26
3.1.1.3 Radio Unit Function (RU) 26
3.1.1.4 Evolved Node B (eNB) 27
3.1.2 RAN Intelligent Controller (RIC) and Service Management and Orchestration (SMO) Functions 28
3.1.3 Interfaces 29
3.2 Near-RT RIC Architecture 30
3.2.1 Standard Functional Architecture Principles 30
3.2.2 E2 Interface Design Principles 32
3.2.3 xApp API Design Architecture 34
3.3 Non-RT RIC Architecture 37
3.3.1 Standard Functional Architecture Principles 38
3.3.2 A1 Interface Design Principles 38
3.3.3 R1 API Design Principles for rApps 41
3.4 SMO Architecture 47
3.4.1 Standard Functional Architecture Principles 47
3.4.2 O1 Interface Design Principles 48
3.4.3 Open M-Plane Fronthaul Design Principles 51
3.4.4 O2 Interface Design Principles 52
3.5 Other O-RAN Functions and Open Interfaces 54
3.5.1 O-RAN compliant Centralized Unit Control Plane (O-CU-CP) 54
3.5.1.1 Control Plane Procedures 54
3.5.1.2 Management Plane Procedures 54
3.5.2 O-CU-UP 54
3.5.2.1 Control Plane Procedures 55
3.5.2.2 User Plane Procedures 55
3.5.2.3 Management Plane Procedures 55
3.5.3 O-DU 55
3.5.3.1 Control Plane Procedures 55
3.5.3.2 User Plane Procedures 55
3.5.3.3 Management Plane Procedures 55
3.5.4 O-eNB 56
3.5.5 O-RU 56
3.6 Conclusion 57
Bibliography 57
4 Cloudification and Virtualization 59
Padma Sudarsan and Sridhar Rajagopal
4.1 Virtualization Trends 59
4.2 Openness and Disaggregation with vRAN 59
4.3 Cloud Deployment Scenarios 61
4.3.1 Private, Public, and Hybrid Cloud 61
4.3.2 Telco Features Required for “Any Cloud” Deployment 62
4.3.3 On Premise, Far Edge, Edge, and Central Deployments 63
4.3.4 Classical, Virtual Machines (VMs), Containers, and Hybrid Deployments 64
4.4 Unwinding the RAN Monolith 64
4.4.1 Adapting Cloud-Native Principles 66
4.4.2 Architectural Patterns 67
4.4.3 Software Architecture Portability and Refactoring Considerations 68
4.4.4 Compute Architecture Consideration 69
4.5 Orchestration, Management, and Automation as Key to Success 70
4.5.1 Acceleration Abstraction Layer 73
4.5.2 Cloud Deployment Workflow Automation 75
4.6 Summary 76
Bibliography 76
5 RAN Intelligence 77
Dhruv Gupta, Rajarajan Sivaraj, and Rittwik Jana
5.1 Introduction 77
5.2 Challenges and Opportunities in Building Intelligent Networks 77
5.3 Background on Machine Learning Life Cycle Management 78
5.4 ML-Driven Intelligence and Analytics for Non-RT RIC 80
5.5 ML-Driven Intelligence and Analytics for Near-RT RIC 82
5.6 E2 Service Models for Near-RT RIC 83
5.6.1 E2SM-KPM 84
5.6.2 E2SM-RC 84
5.6.3 Other E2SMs 85
5.7 ml Algorithms for Near-RT RIC 86
5.7.1 Reinforcement Learning Models 87
5.8 Near-RT RIC Platform Functions for AI/ML Training 88
5.9 RIC Use Cases 89
5.10 Conclusion 90
Bibliography 90
6 The Fronthaul Interface 91
Aditya Chopra
6.1 The Lower-Layer Split RAN 91
6.1.1 Lower Layer Fronthaul Split Options 92
6.2 Option 8 Split – CPRI and eCPRI 93
6.3 Option 6 Split – FAPI and nFAPI 94
6.3.1 Subinterfaces 97
6.3.2 Architecture Agnostic Deployment 97
6.4 Option 7 Split – O-RAN Alliance Open Fronthaul 97
6.4.1 Control (C) and User (U) Plane 98
6.4.2 Management (M) Plane 98
6.4.3 Synchronization (S) Plane 100
6.4.4 Key Features 100
6.4.4.1 Fronthaul Compression 100
6.4.4.2 Delay Management 102
6.4.4.3 Beamforming 102
6.4.4.4 Initial Access 103
6.4.4.5 License Assisted Access and Spectrum Sharing 104
6.5 Conclusions 104
Bibliography 104
7 Open Transport 105
Reza Vaez-Ghaemi and Luis Manuel Contreras Murillo
7.1 Introduction 105
7.2 Requirements 105
7.2.1 Fronthaul Requirements 106
7.2.2 Midhaul Requirements 106
7.2.3 Backhaul Requirements 107
7.2.4 Synchronization Requirements 107
7.3 WDM Solutions 108
7.3.1 Passive WDM 109
7.3.2 Active WDM 109
7.3.3 Semiactive WDM 110
7.4 Packet-Switched Solutions 111
7.4.1 Technology Overview 112
7.4.2 Deployment Patterns 112
7.4.3 Connectivity Service and Protocols 113
7.4.4 Quality of Service (QoS) 114
7.5 Management and Control Interface 114
7.5.1 Control and Management Architecture 114
7.5.2 Interaction with O-RAN Management 116
7.6 Synchronization Solutions 117
7.6.1 Synchronization Baseline 117
7.6.2 Synchronization Accuracy and Limits 118
7.7 Testing 118
7.8 Conclusion 119
Bibliography 120
8 O-RAN Security 121
Amy Zwarico
8.1 Introduction 121
8.2 Zero Trust Principles 121
8.3 Threats to O-RAN 122
8.3.1 Stakeholders 122
8.3.2 Threat Surface and Threat Actors 122
8.3.3 Overall Threats 123
8.3.4 Threats Against the Lower Layer Split (LLS) Architecture and Open Fronthaul Interface 123
8.3.5 Threats Against O-RU 124
8.3.6 Threats Against Near- and Non-Real-Time RICs, xApps, and rApps 124
8.3.7 Threats Against Physical Network Functions (PNFs) 124
8.3.8 Threats Against SMO 125
8.3.9 Threats Against O-Cloud 125
8.3.10 Threats to the Supply Chain 125
8.3.11 Physical Threats 126
8.3.12 Threats Against 5G Radio Networks 126
8.3.13 Threats to Standards Development 126
8.4 Protecting O-RAN 126
8.4.1 Securing the O-RAN-Defined Interfaces 126
8.4.1.1 A1 127
8.4.1.2 O1 127
8.4.1.3 O2 128
8.4.1.4 E2 128
8.4.1.5 Open Fronthaul 128
8.4.1.6 R1 130
8.4.1.7 3GPP Interfaces 131
8.4.2 Securing the O-Cloud 131
8.4.3 Container Security 131
8.4.4 O-RAN Software Security 131
8.4.5 Software Bill of Materials (SBOM) 132
8.5 Recommendations for Vendors and MNOs 132
8.6 Conclusion 134
Bibliography 134
9 Open RAN Software 137
David Kinsey, Padma Sudarsan, and Rittwik Jana
9.1 Introduction 137
9.2 O-RAN Software Community (OSC) 138
9.2.1 OSC Projects 138
9.2.2 The Service Management and Orchestration (SMO) Framework 138
9.2.3 Near-RT RIC (RIC) 139
9.2.4 O-CU-CP and O-CU-UP 140
9.2.5 O-DU Project 140
9.2.6 O-RU 140
9.2.7 O-Cloud 140
9.2.8 The AI/ML Framework 141
9.2.9 Support Projects 141
9.3 Open Network Automation Platform (ONAP) 141
9.3.1 Netconf/YANG Support 141
9.3.2 Configuration Persistence 142
9.3.3 VES Support 142
9.3.4 A1 Support 142
9.3.5 Optimization Support 142
9.4 Other Open-Source Communities 143
9.5 Conclusion 144
Bibliography 144
10 Open RAN Deployments 145
Sidd Chenumolu
10.1 Introduction 145
10.2 Network Architecture 146
10.2.1 Network Components 147
10.2.1.1 Antenna 147
10.2.1.2 O-RAN – Radio Unit 148
10.2.1.3 O-RAN-Distributed Unit (O-DU) 150
10.2.1.4 O-RAN-Centralized Unit (O-CU) 150
10.2.1.5 RAN Intelligent Controller (RIC) 150
10.2.2 Traditional vs. O-RAN Deployment 151
10.2.3 Typical O-RAN Deployment 152
10.2.4 Spectrum and Regulatory 153
10.3 Network Planning and Design 153
10.3.1 Cell Site Design 154
10.3.2 Network Function Placement 155
10.3.3 Dimensioning 155
10.3.3.1 Application Dimensioning 155
10.3.3.2 Platform Dimensioning 156
10.3.4 Virtualization Impact 156
10.3.4.1 Non-Uniform Memory Access 157
10.3.4.2 Hyper-Threading 157
10.3.4.3 CPU Pinning 157
10.3.4.4 Huge Page 157
10.3.4.5 Single Root Input/Output Virtualization 158
10.3.4.6 PCI Passthrough 158
10.3.4.7 Data Plane Development Kit 158
10.3.4.8 Resource Director Technology 158
10.3.4.9 Cache Allocation Technology 158
10.3.4.10 Resource Overcommitment 159
10.3.4.11 Operating System 159
10.3.4.12 K8S Impact 159
10.3.5 Networking Hardware 159
10.3.6 Hardware Type 160
10.3.7 Reliability and Availability 160
10.3.8 Impact of Network Slicing 161
10.4 Network Deployment 162
10.4.1 DU Deployment 162
10.4.1.1 DU Deployed at a Centralized Data Center 162
10.4.1.2 Timing Design When DU is at the dc 163
10.4.1.3 DU Deployed at Cell Site 164
10.4.2 CU Deployment 165
10.4.3 Radio Unit Instantiation 165
10.4.4 Radio Unit Management 166
10.4.4.1 Hierarchical Management Architecture Model 166
10.4.4.2 Hybrid Management Architecture Model 166
10.4.5 Network Management 166
10.4.6 Public Cloud Provider Overview 167
10.4.6.1 Native Services 167
10.4.6.2 CD Pipeline 167
10.4.6.3 Cluster Creation and Management 168
10.4.6.4 Transport Design 168
10.4.7 Life Cycle Management of NFs 168
10.4.8 Network Monitoring and Observability 169
10.4.8.1 Prometheus 169
10.4.8.2 Jaeger 169
10.4.8.3 Fluentd and Fluentbit 169
10.4.8.4 Probing 169
10.4.9 Network Inventory 169
10.4.10 Building the Right Team 170
10.5 Conclusion 170
Bibliography 170
11 Open RAN Test and Integration 172
Ian Wong, Ph.D.
11.1 Introduction 172
11.2 Testing Across the Network Life Cycle 174
11.3 O-RAN ALLIANCE Test and Integration Activities 175
11.3.1 Test Specifications 175
11.3.2 Conformance Test Specifications 176
11.3.2.1 A1 Interface Test Specification (O-RAN.WG2.A1TS) 178
11.3.2.2 E2 Interface Test Specification (O-RAN.WG3.E2TS) 179
11.3.2.3 Open Fronthaul Conformance Test Specification (O-RAN.WG4.CONF) 180
11.3.2.4 Xhaul Transport Testing (O-RAN.WG9.XTRP-Test.0) 181
11.3.2.5 Security Test Specifications (O-RAN.SFG.Security-Test-Specifications) 181
11.3.3 Interoperability Test Specifications 181
11.3.3.1 Fronthaul Interoperability Test Specification (O-RAN.WG4.IOT.0-09.00) 182
11.3.3.2 Open F1/W1/E1/X2/Xn Interoperability Test Specification (O-RAN.WG5.IOT.0) 183
11.3.3.3 Stack Interoperability Test Specification (O-RAN.WG8.IOT) 183
11.3.4 End-to-End Test Specifications 185
11.3.5 O-RAN Certification and Badging 186
11.3.6 Open Test and Integration Centers 187
11.3.7 O-RAN Global PlugFests 189
11.4 Conclusion 189
Bibliography 189
12 Other Open RAN Industry Organizations 191
Aditya Chopra, Manish Singh, Prabhakar Chitrapu, Luis Lopes, and Diane Rinaldo
12.1 Telecom Infra Project 191
12.1.1 Organizational Structure 192
12.1.2 Core Activities 194
12.2 Trials and Deployments 194
12.3 Small Cell Forum 195
12.3.1 A History of Openness at SCF 196
12.3.2 Alignment with the 3GPP and O-RAN Alliance Solutions 196
12.4 3rd Generation Partnership Project 197
12.5 Open RAN Policy Coalition 199
12.6 Conclusion 200
Bibliography 200
Index 201
