Open RAN E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Open RAN A comprehensive survey of Open RAN technology and its ecosystem In Open RAN: The Definitive Guide, a team of distinguished industry leaders deliver an authoritative guide to all four principles of the Open RAN vision: openness, virtualization, intelligence, and interoperability. Written by the industry experts currently defining the specifications, building the systems, and testing and deploying the networks, the book covers O-RAN architecture, the fronthaul interface, security, cloudification, virtualization, intelligence, certification, badging, and standardization. This critical reference on Open RAN explains how and why an open and disaggregated, intelligent, and fully virtualized network is the way networks should be designed and deployed moving forward. Readers will also find: * A thorough introduction from key industry players, including AT&T, Telefonica, Mavenir, VMWare, Google and VIAVI * Comprehensive explorations of Open X-Haul transport networks and other unique 5G capabilities * Practical discussions of the four pillars of O-RAN architecture: openness, virtualization, intelligence, and interoperability * Comprehensive treatments of how smaller vendors can introduce their own services and customize the network Perfect for engineers, product managers, and marketing professionals in the telecom industry, Open RAN: The Definitive Guide will also benefit graduate students, researchers, and engineers in government agencies with involvement in the wireless and telecom industries.
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Seitenzahl: 457
Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Table of Contents
Series Page
Title Page
Copyright Page
List of Contributors
Foreword
Preface
About the Authors
Definitions / Acronyms
1 The Evolution of RAN
1.1 Introduction
1.2 RAN Architecture Evolution
1.3 The Case for Open RAN
1.4 6G and the Road Ahead
1.5 Conclusion
Bibliography
2 Open RAN Overview
2.1 Introduction
2.2 Open RAN Architecture
2.3 Open RAN Cloudification and Virtualization
2.4 RAN Intelligence
2.5 Fronthaul Interface and Open Transport
2.6 Securing Open RAN
2.7 Open Source Software
2.8 RAN Automation and Deployment with CI/CD
2.9 Open RAN Testing
2.10 Industry Organizations
2.11 Conclusion
Bibliography
3 O‐RAN Architecture Overview
3.1 Introduction
3.2 Near‐RT RIC Architecture
3.3 Non‐RT RIC Architecture
3.4 SMO Architecture
3.5 Other O‐RAN Functions and Open Interfaces
3.6 Conclusion
Bibliography
4 Cloudification and Virtualization
4.1 Virtualization Trends
4.2 Openness and Disaggregation with vRAN
4.3 Cloud Deployment Scenarios
4.4 Unwinding the RAN Monolith
4.5 Orchestration, Management, and Automation as Key to Success
4.6 Summary
Bibliography
5 RAN Intelligence
5.1 Introduction
5.2 Challenges and Opportunities in Building Intelligent Networks
5.3 Background on Machine Learning Life Cycle Management
5.4 ML‐Driven Intelligence and Analytics for Non‐RT RIC
5.5 ML‐Driven Intelligence and Analytics for Near‐RT RIC
5.6 E2 Service Models for Near‐RT RIC
5.7 ML Algorithms for Near‐RT RIC
5.8 Near‐RT RIC Platform Functions for AI/ML Training
5.9 RIC Use Cases
5.10 Conclusion
Bibliography
6 The Fronthaul Interface
6.1 The Lower‐Layer Split RAN
6.2 Option 8 Split – CPRI and eCPRI
6.3 Option 6 Split – FAPI and nFAPI
6.4 Option 7 Split – O‐RAN Alliance Open Fronthaul
6.5 Conclusions
Bibliography
7 Open Transport
7.1 Introduction
7.2 Requirements
7.3 WDM Solutions
7.4 Packet‐Switched Solutions
7.5 Management and Control Interface
7.6 Synchronization Solutions
7.7 Testing
7.8 Conclusion
Bibliography
8 O‐RAN Security
8.1 Introduction
8.2 Zero Trust Principles
8.3 Threats to O‐RAN
8.4 Protecting O‐RAN
8.5 Recommendations for Vendors and MNOs
8.6 Conclusion
Bibliography
9 Open RAN Software
9.1 Introduction
9.2 O‐RAN Software Community (OSC)
9.3 Open Network Automation Platform (ONAP)
9.4 Other Open‐Source Communities
9.5 Conclusion
Bibliography
10 Open RAN Deployments
10.1 Introduction
10.2 Network Architecture
10.3 Network Planning and Design
10.4 Network Deployment
10.5 Conclusion
Bibliography
11 Open RAN Test and Integration
11.1 Introduction
11.2 Testing Across the Network Life Cycle
11.3 O‐RAN ALLIANCE Test and Integration Activities
11.4 Conclusion
Bibliography
12 Other Open RAN Industry Organizations
12.1 Telecom Infra Project
12.2 Trials and Deployments
12.3 Small Cell Forum
12.4 3rd Generation Partnership Project
12.5 Open RAN Policy Coalition
12.6 Conclusion
Bibliography
Index
End User License Agreement
List of Tables
Chapter 7
Table 7.1 Frame loss ratio requirements.
Table 7.2 One‐way delay requirements [O‐RAN.WG9.XTRP‐REQ‐v01.00 2020].
Table 7.3 TAE limits for category A+ through C services.
Table 7.4 Example of Fronthaul and Midhaul dimensioning for scenarios in [O...
Chapter 11
Table 11.1 Interfaces in 3GPP‐based open radio access network with correspo...
Table 11.2 Available certificates and badges and their corresponding certif...
List of Illustrations
Chapter 1
Figure 1.1 Five generations of mobile cellular networks.
Figure 1.2 Main components of a mobile network.
Figure 1.3 Layers of the protocol stack of a 3GPP mobile network.
Figure 1.4 Simplified view of a 2G network.
Figure 1.5 Simplified 3G/3.5G RAN architecture.
Figure 1.6 Simplified 4G/LTE RAN architecture.
Figure 1.7 The 4.5G RAN architecture.
Figure 1.8 ITU IMT‐2020‐standard vision.
Figure 1.9 The evolution from 2G RAN to 5G RAN.
Figure 1.10 Evolution toward open RAN.
Chapter 2
Figure 2.1 Multi‐vendor Open RAN ecosystem.
Figure 2.2 Intelligent applications in Near‐RT RIC.
Figure 2.2a RAN Programmability
Figure 2.3 Accelerating open RAN platforms operator survey.
Chapter 3
Figure 3.1 An informal view of the O‐RAN functions.
Figure 3.2 O‐RAN architecture.
Figure 3.3 Near‐RT RIC architecture.
Figure 3.4 Non‐RT RIC architecture.
Figure 3.5 Exposure of SMO and non‐RT RIC framework services.
Figure 3.6 O‐Cloud infrastructure inventory.
Figure 3.7 Logical clouds.
Chapter 4
Figure 4.1 Virtualization trends.
Figure 4.2 Decomposition of the RAN.
Figure 4.3 “Any Cloud” deployment models.
Figure 4.4 Features required for “Any Cloud” deployment.
Figure 4.5 RAN function deployment.
Figure 4.6 Workload deployment options.
Figure 4.7 Aspects of transformation.
Figure 4.8 Cloud‐native principles.
Figure 4.9 In‐line and look‐aside accelerators.
Figure 4.10 Service management and orchestration.
Figure 4.11 Infrastructure and deployment management services.
Figure 4.12 Cloud‐based deployment.
Figure 4.13 Accelerator abstraction layer and APIs.
Chapter 5
Figure 5.1 Machine learning deployment scenario.
Figure 5.2 Machine learning life cycle management and implementation example...
Figure 5.3 Illustration of a reinforcement learning engine in the near‐RT RI...
Figure 5.4 Near‐RT RIC architecture,
Figure 5.5 RIC use cases and applications
Chapter 6
Figure 6.1 CPRI‐based fronthaul architecture.
Figure 6.2 eCPRI‐based fronthaul architecture.
Figure 6.3 RAN split options proposed by 3GPP.
Figure 6.4 Option 8 fronthaul split between baseband and radio unit.
Figure 6.5 FAPI and nFAPI split architectures.
Figure 6.6 Using FAPI and nFAPI in various split RAN architectures.
Figure 6.7 Option 7‐2 split architecture.
Figure 6.8 Hierarchical and hybrid architectures of the M‐plane.
Figure 6.9 Option 7‐2 split data flows.
Chapter 7
Figure 7.1 Xhaul transport networks [XPSAAS].
Figure 7.2 Definition of absolute and relative TAE and TE.
Figure 7.3 Passive WDM (O‐RAN.WG9.WDM.0‐R003‐v03.00 2022).
Figure 7.4 Active WDM (O‐RAN.WG9.WDM.0‐R003‐v03.00 2022).
Figure 7.5 Semiactive WDM (O‐RAN.WG9.WDM.0‐R003‐v03.00 2022). (a) Type I. (b...
Figure 7.6 TIP open transport SDN architecture.
Figure 7.7 Overall O‐RAN Architecture.
Figure 7.8 Synchronization topologies.
Chapter 8
Figure 8.1 O‐RAN high‐level architecture.
Figure 8.2 SMO and non‐real‐time RIC architecture.
Chapter 9
Figure 9.1 O‐RAN logical architecture.
Chapter 10
Figure 10.1 High‐level E2E architecture.
Figure 10.2 Traditional vs. vRAN vs. ORAN.
Figure 10.3 Disaggregated vRAN vs. conventional RAN.
Figure 10.4 Typical O‐RAN macro deployment.
Figure 10.5 Centralized DU deployment.
Figure 10.6 Timing distribution when DU is deployed at the DC.
Figure 10.7 DU deployment at site.
Figure 10.8 Hierarchical RU management.
Figure 10.9 Hybrid RU management.
Chapter 11
Figure 11.1 The O‐RAN evolution fundamentally changes the mobile network arc...
Figure 11.2 Basic network life cycle.
Figure 11.3 Illustrative open RAN functional diagram.
Figure 11.4 Test configuration for A1 conformance of the non‐RT RIC.
Figure 11.5 Test configuration for A1 conformance of the near‐RT RIC.
Figure 11.6 Test configuration for E2 conformance of the near‐RT RIC.
Figure 11.7 Test configuration for E2 conformance of the E2 nodes.
Figure 11.8 Test configuration for open fronthaul conformance of the O‐RU....
Figure 11.9 Test configuration for open fronthaul conformance of the O‐DU....
Figure 11.10 Test configuration for open fronthaul interoperability between ...
Figure 11.11 Test configuration for X2 interoperability between an eNB and e...
Figure 11.12 Test configuration for F1 interoperability between gNB‐CU and g...
Figure 11.13 Test configuration for Xn interoperability between gNBs.
Figure 11.14 Test configuration for an O‐RAN system end‐to‐end test.
Figure 11.15 Test configuration for an O‐RAN system end‐to‐end load and stre...
Figure 11.16 Test configuration for an O‐RAN system end‐to‐end RIC‐enabled u...
Figure 11.17 O‐RAN certification and badging structure.
Chapter 12
Figure 12.1 Hardware and software disaggregation in Open RAN.
Figure 12.2 TIP's Open RAN Project Group structure.
Figure 12.3 Open RAN trials and deployments.
Figure 12.4 Illustration of potential function splits between central and di...
Guide
Cover Page
Series Page
Title Page
Copyright Page
List of Contributors
Foreword
Preface
About the Authors
Definitions / Acronyms
Table of Contents
Begin Reading
Index
Wiley End User License Agreement
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IEEE Press445 Hoes LanePiscataway, NJ 08854
IEEE Press Editorial BoardSarah Spurgeon, Editor in Chief
Jón Atli Benediktsson
Behzad Razavi
Jeffrey Reed
Anjan Bose
Jim Lyke
Diomidis Spinellis
James DuncanAmin MoenessDesineni Subbaram Naidu
Hai LiBrian Johnson
Adam DrobotTom RobertwazziAhmet Murat Tekalp
Open RAN
The Definitive Guide
Edited by
Dr. Ian C. Wong
VIAVI SolutionsAustin, TX, USA
Dr. Aditya Chopra
Amazon Kuiper LLCAustin, TX, USA
Dr. Sridhar Rajagopal
MavenirRichardson, TX, USA
Dr. Rittwik Jana
GoogleNew York, NY, USA
Copyright © 2024 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.
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List of Contributors
Sidd ChenumoluDISH Network, EnglewoodCO, USA
Prabhakar ChitrapuSCF, St. LouisMO, USA
Aditya ChopraAmazon Kuiper, RedmondWA, USA
Luis Manuel Contreras MurilloTelefonica, Distrito TelefónicaMAD, Spain
Dhruv GuptaAT&T, San RamonCA, USA
Rittwik JanaGoogle, New York CityNY, USA
David KinseyAT&T, SeattleWA, USA
Luis LopesQualcomm, BoulderCO, USA
Sridhar RajagopalMavenir, RichardsonTX, USA
Diane RinaldoORPC, PortlandME, USA
Manish SinghDell, Round RockTX, USA
Rajarajan SivarajMavenir, RichardsonTX, USA
Padma SudarsanVMWare, Palo AltoCA, USA
Reza Vaez‐GhaemiVIAVI Solutions, GermantownMD, USA
Ian WongVIAVI Solutions, AustinTX, USA
Sameh M. YamanyVIAVI Solutions, BoulderCO, USA
Amy ZwaricoAT&T, DallasTX, USA
Foreword
Virtualization and cloud have unified computing and networking. This unification can be seen in all areas of wired communications. With Open RAN (O‐RAN), wireless communications will be able to take advantage of the unification as well.
Wireless communications are overtaking wired communications. According to some estimates, traffic from wireless and mobile devices accounts for two‐thirds of all IP traffic. However, the deployment of wireless communications is costly. The cost is mainly driven by RAN. For example, substantial increase in the number of cell sites and radio types with massive MIMO (multi‐input multi‐output) technology required by 5G drives RAN costs even higher. O‐RAN attempts to solve this problem by disaggregating and splitting the RAN, supporting standardized interfaces that can interoperate with each other. This standardization drives multivendor radio, hardware, and software deployments with key functions implemented as virtual network functions (VNFs) and cloud‐native network functions (CNFs) on vendor‐neutral hardware and networks implemented in modular units.
Building O‐RAN and ensuring its performance guarantees are huge undertakings. Compared to traditional RAN, installing and operating O‐RAN is expected to be substantially more complex and time‐consuming. The expense of this model may offset O‐RAN cost savings as in virtualized wired networks. However, an open and virtualized model should drive more innovations, flexibility, and automation in wireless communications. For example, RAN Intelligent Controllers (RIC) with open APIs should provide a platform for the developer community to innovate RAN algorithms.
This book discusses various industry groups and standardization bodies participating in specifying O‐RAN technologies; O‐RAN architecture consisting of RIC, Service Management and Orchestration architecture, cloudification and virtualization, open transport, security, and open software; and typical O‐RAN deployment scenarios. It is a valuable book in this area.
Mehmet Toy, PhD
Associate Verizon FellowDistinguished MEF FellowITU‐T SG13 (Future Networks) Vice ChairIEEE Life‐Time Senior Member
Preface
“Wouldn’t it be great if we had a book on O‐RAN?” It was a discussion I had with Sameh Yamany, VIAVI CTO and my manager and mentor, as I began my journey with VIAVI and in the world of open RAN and the O‐RAN ALLIANCE. It was towards the end of 2020, where I first started as a contributor to the open fronthaul test specifications, and even after taking the helm as co‐chair of the Test and Integration Focus Group. There’s always something new that I learned as I delved deeper into the various topics encompassing the vast field of open RAN. As I then tried to on‐board new employees in our company to contribute to the O‐RAN ALLIANCE, or introduce open RAN to external audiences, I realized that a definitive guide written by active members and contributors to the specification body for Open RAN, i.e. the O‐RAN ALLIANCE, would be a worthwhile contribution to the field. I first contacted my Ph.D. advisor, Prof. Brian Evans who suggested I contact a former graduate school buddy Aditya Chopra, in AT&T labs at the time, who was an active contributor to the open fronthaul specifications (WG4) in O‐RAN. After a brief coffee conversation in the middle of the COVID pandemic, we sketched out a rough outline, and decided to bring on‐board 2 more editors, Sridhar Rajagopal from Mavenir, and Rittwik Jana, from VMWare at the time, to embark on this journey. It was a long journey of recruiting expert authors, going through the editing process, and finally coming up with this book, which we hope would be useful guide to anybody new to the field of open RAN and wanting to know more about its ins and outs, but also to seasoned veterans in a specific area, wanting to understand more the other aspects of this vast field that is revolutionizing the telco industry as we speak.
Ian Wong, Editor, Open RAN, The Definitive Guide
As one of the earliest O‐RAN delegates, and lead delegate for AT&T in O‐RAN Fronthaul Working Group, I was often approached by colleagues in both the technical and business organizations within AT&T requesting to learn more about Open RAN, its concepts and the role played by the myriad standards bodies within this ecosystem. It is not sufficient to just point to the documents or reports produced by the standards, as they are often unable to capture the nuances behind the decisions that are listed within them. So when Ian approached me about writing a book on Open RAN, we both quickly agreed on the unmet need of having a guide for newcomers into the world of Open RAN. Given the vastness of this ecosystem, we also knew it had to be an edited book with chapters authored by the experts in that particular slice of the Open RAN universe. With Ritwik and Sridhar, as well as the various chapter authors jumping on board, I am truly grateful for the wonderful learning experience I was afforded while working with such a brilliant group of accomplished leaders in their respective fields.
Aditya Chopra, Editor, Open RAN, The Definitive Guide
At Mavenir, I have been working on Open RAN products since the inception of the O‐RAN alliance, and contributing on open RAN specifications, eco‐system development and solutions. I have always received and still continue to receive questions from our partners and customers on eco‐system readiness, deployment aspects, security aspects, etc. This always required extra effort in customer education. While specifications are available, they are not in a form that can be easily consumed by someone wanting to understand open RAN. So, when Ian contacted me on the co‐editing a book on open RAN, I felt it would be wonderful to provide all this information in one place for anyone investing in open RAN and putting together a team of expert contributors from various domains such as Open RAN product development, hardware, platform, test and measurement solutions, and operator deployments. It has been a pleasure working with my co‐editors and contributors on this book and I look forward to this book being used as a definitive guide for open RAN.
Sridhar Rajagopal, Editor, Open RAN ‐ The Definitive guide
Ian and Aditya approached me to co‐author this book on Open RAN early 2021 along with Sridhar. I was already heavily involved in the O‐RAN standards organization and had gained a lot of experience driving proof of concepts at AT&T back then. It was a great opportunity to tell a story about a piece of technology that is moving so fast. A lot of hard work and passion goes into making a new piece of technology such as Open RAN real, from the crafting of standards specifications to open source implementations and eventually real world deployments. I thought that writing this book would be a nice way to capture some of those interesting tidbits to the engineers and practitioners of this evolving field.
We charted out a quick plan to capture the various aspects of Open RAN and invite experts in the field to contribute to this book. It was a long journey of getting all the chapter contributions incorporated into a draft and editing the overall narrative so that there is a flow. We hope that this "snapshot" of Open RAN technology will be a useful guide to all. I am very grateful and fortunate to work with so many talented people everyday in this field and it has truly been a humbling experience.
Rittwik Jana, Editor, Open RAN ‐ The Definitive guide
About the Authors
Dr. Ian C. Wong is presently the Director of RF and Wireless Architecture in the CTO office at VIAVI Solutions, where he is leading RF and wireless technology strategy, architectures, and standards. He is the co‐chair of the Test and Integration Focus Group (TIFG) and the Next‐Generation Research Platforms research stream in the O‐RAN Alliance, and VIAVI’s representative at the full member and steering groups of the NextG Alliance. From 2009 to Aug 2020, he was with NI (formerly National Instruments) where his last position was Section Manager of Wireless Systems R&D where he led the development of real‐time end‐to‐end 5G wireless test and prototyping systems, and managed the company’s 3GPP wireless standards and IP strategy. From 2007 to 2009, he was a systems research and standards engineer with Freescale Semiconductor where he represented Freescale in the 3GPP LTE standardization efforts. He is a senior member of the IEEE, was the Director of Industry Communities for IEEE Communications Society 2016–2019, and was the Industry Program Chair for IEEE Globecom 2014 in Austin.
Dr. Wong co‐authored the Springer book “Resource Allocation for Multiuser Multicarrier Wireless Systems,” numerous patents, standards contributions, and IEEE journal and conference publications. He was awarded the Texas Telecommunications Engineering Consortium Fellowship in 2003–2004, and the Wireless Networking and Communications Group student leadership award in 2007.
He received the MS and PhD degrees in electrical engineering from the University of Texas at Austin in 2004 and 2007, respectively, and a BS degree in electronics and communications engineering (magna cum laude) from the University of the Philippines in 2000.
Dr. Aditya Chopra is a Senior Communication Systems Engineer at Project Kuiper within Amazon, where he develops systems solutions and prototypes for Low‐Earth Orbit communication networks. From 2017 to 2022, he was a Principal Member of Technical Staff at AT&T, where he performed communication systems research and prototyping of wireless cellular solutions. At AT&T, he was the lead representative at the Fronthaul Working Group (WG4) within the O‐RAN Alliance. He was the lead representative and one of the key members developing fronthaul specifications within this group when it was part of xRAN. From 2012 to 2017, he was a systems engineer at National Instruments, developing high speed wireless test solutions. His research interests include wireless physical layer optimization and prototyping of advanced wireless communication systems.
Dr. Chopra received his PhD (2011) and M.S. (2008) degrees in electrical engineering from The University of Texas at Austin, Texas, USA and his B.Tech degree in electrical engineering from the Indian Institute of Technology, Delhi, India, in 2006.
Sridhar Rajagopal is currently SVP, Access Technologies at Mavenir Systems, where he leads cross‐functional design and solutions for Mavenir's Open RAN products involving the RAN, radio and RIC platforms. Prior to this, he was one of the initial employees at Ranzure Networks, a cloud RAN start‐up. He also had R&D roles in design, prototyping and standardization of 5G cellular and Wi‐Fi systems at Samsung, in UWB technology at WiQuest communications and 3G/4G research at Nokia. He was an associate editor for the Journal of Signal Processing Systems (Springer) and has led leadership positions in standardization bodies such as IEEE and WiMedia. He was a co‐recipient of the IEEE 2017 Marconi Prize Paper award for his research on mmWave systems. He has co‐invented around 50 issued US patents. He received his M.S. and Ph.D. degrees from Rice University and is a senior member of IEEE.
Rittwik Jana is currently a Telco analytics and automation network engineer at Google. He was previously the chief architect of RAN intelligence at VMware and a Director/MTS of inventive science at AT&T Shannon Research Labs. He is an industry expert with 25 years of experience in numerous wireless technologies and standards. His work has focused primarily on building services for cellular network planning using AI/ML and Google cloud APIs, disaggregating and optimizing the RAN using Open RAN technologies, model driven control loop automation in O‐RAN/ONAP and performance evaluation of next‐generation mobile streaming apps such as AR/VR/360 video. He is the co‐chair of the requirements group in Open RAN Software Community (OSC) and was the chair of WG5 FCC’s Communications Security, Reliability, and Interoperability Council in 2021. He is a recipient of the 2016 AT&T Science and Technology medal and the 2017 IEEE Vehicular Technology society Jack Neubauer memorial paper award on full duplex wireless. He earned a Ph.D. in Telecommunications Engineering from the Australian National University, Canberra, Australia in 2000.
Definitions / Acronyms
3GPP
Third‐generation Partnership Project (3gpp.org)
5GC
5G Core
5GS
5G System
5QI
5G QoS Class Identification
AAL
Acceleration abstraction layer
ACK
Acknowledgement
ACS
Adjacent Channel Selectivity
AF
Application Function
AI
Artificial intelligence
ARPU
Average revenue per user
AMF
Access and mobility management function
API
Application programming interface
AOI
Area Of Interest
AP
Application Protocol
A‐PTS
Assisted‐Partial Timing Support
ARP
Allocation Retention Priority
AS
Autonomous Systems
AWS
Amazon Web Services
BASTA
Base Station Antenna Standard
BBDEV
Baseband Development (Intel Library)
BBU
Baseband Unit
BGP
Border Gateway Protocol
BLER
Block Error Rate
BMCA
Best Master Clock Algorithm
BOM
Bill Of Material
BWP
Bandwidth Part
CaaS
Containers as a Service
CALEA
Commission on Accreditation for Law Enforcement Agencies
CAT
Cache Allocation Technology
CC
Component Carrier
CFR
Crest Factor Reduction
CI/CD
Continuous Integration/Continuous Deployment
CM
Configuration Management
CNCF
Cloud Native Computing Foundation
CNI
Container Network Interface
COTS
Commercial Off the Shelf
CP
Control Plane
CP
Cyclic Prefix
CPU
Central Processing Unit
CQRS
Command and Query Responsibility Segregation
CSAR
Cloud Service Archive
CSP
Communication Service Provider
CSR
Cell Site Router
CU
Centralized Unit
CUPS
Control User Plane Separation
CA
Carrier Aggregation
CN
Core network
COTS
Common or commercial off‐the‐shelf
CPRI
Common public radio interface
CQI
Channel Quality Index
cRAN
Cloud or centralized RAN
CTI
Cooperative Transport Interface
CUSM
Control, user, synchronization, and management plane, in relation to Open Fronthaul
dB
decibel
DC
Dual Connectivity
DC
Data Center
DHCP
Dynamic Host Configuration Protocol
DME
Data Management and Exposure
DMS
Deployment Management Service
DNS
Domain Name System
DPD
Digital Pre Distortion
DPDK
Data Plane Development Kit
DRAM
Dynamic RAM
DRB
Data Radio Bearer
DSCP
Differentiated Services Code Point
DU
Distributed Unit
DAST
Dynamic Application Security Testing
D‐TLS
Datagram Transport Layer Security
DAPS
Dual Active Protocol Stack
DOCSIS
Data Over Cable Service Interface Specification
DL
Downlink
DM
Data Model
DUT
Device under test
EC2
Elastic Cloud Compute
ECR
Elastic Container Registry
EDC
Edge Data Center
EKS
Elastic Kubernetes Service
eMBB
enhanced Mobile Broadband
EMS
Element Management System
eMTC
enhanced Machine Type Communication
ETSI
European Telecommunications Standards Institute
EVC
Ethernet Virtual Circuits
EVM
Error Vector Magnitude
EARFCN
E‐UTRA Absolute Radio Frequency Channel Number
eCPRI
Enhanced common public radio interface
eNB
evolved Node B, essentially the 4G base station
EN‐DC
E‐UTRAN New Radio Dual Connectivity
EPC
Enhanced packet core, core network for 4G
E2SM
E2 Service Model
E‐UTRA
Evolved Universal Terrestrial Radio Access
E‐UTRAN
Evolved Universal Terrestrial Radio Access Network
FCAPS
Fault, Configuration, Accounting, Performance, Security
FDD
Frequency Division Multiplexing
FEC
Forward Error Correction
FH
Fronthaul
FOCOM
Federated O‐Cloud Orchestration and Management
FPGA
Field Programmable Gate Array
FQDN
Fully Qualified Domain Name
FAPI
Fronthaul Application Platform Interface
FHM
Fronthaul multiplexer
FHG or FHGW
Fronthaul gateway
FFT
Fast Fourier Transform
FM
Fault Management
GaN
Gallium Nitride
GCP
Google Cloud Platform
GKE
Google Kubernetes Engine
GM
Grand Master
GPS
Global Positioning System
GPU
Graphical Processing Unit
gNB
next generation Node B, essentially the 5G base station
gNB‐CU
gNB Central Unit
gNB‐DU
gNB Distributed Unit
GPDR
General Data Protection Regulation
HO
Handover
HT
Hyper Threading
HCP
Hyperscale cloud provider
HMTC
High Performance Machine Type Communication
I/O
Input/Output
IA
Intel Architecture
IaaS
Infrastructure as a Service
IE
Information Element
IFFT or iFFT
Inverse Fast Fourier Transform
IMS
Infrastructure Management Service or IP Multimedia Subsystem
IOC
Information Object Class
IEEE
Institute of Electrical and Electronics Engineers
IETF
Internet Engineering Task Force
ITU
International telecommunication union
IM
Information Model
IoT
Internet of Things
IOT
Interoperability Test
IP
Internet protocol
IPSec
Internet Protocol Security
K8S
Kubernetes
KPI
Key Performance Indicator
LCM
Life Cycle Management
LDC
Local Data Center
LEA
Law Enforcement Agency
LI
Legal Intercept
LLC
Last Level Cache
LLS
Lower Layer Split
LTE
Long Term Evolution
LAN
Local Area Networks
LSTM
Long Short Term Memory
MAC
Medium Access Control
MDT
Minimization of Drive Testing
ML
Machine Learning
MME
Mobile Management Entity
mMIMO
massive MIMO
MnS
Management Service
MOI
Managed Object Instance
MPLS
Multiprotocol Label Switching
MTBF
Mean Time Between Failures
MU‐MIMO
Multi‐User Multiple Input Multiple Output
MA
Managed Application
M2M
Machine‐to‐machine
MDP
Markov Decision Processes
ME
Managed Element
MF
Managed Function
MIMO
Multiple‐input Multiple‐output
MMS
Multimedia Message Service
mMTC
massive machine‐type communication
MNO
Mobile network operator
NATS
Network Address Translation
NB‐IoT
NarrowBand Internet of Things
NEBS
Network Equipment Building Systems
NETCONF
Network Configuration Protocol
NF
Network Functions or Noise Figure
NFO
Network Function Orchestrator
NGMN
Next Generation Mobile Network
NIC
Network Interface Card
NIS
Network Information Service
NMS
Network Management System
NUMA
Non‐Uniform Memory Access
NAC
Network Access Control
NAS
Non‐access‐stratum
NBI
Northbound interface
Near‐RT RIC
Near‐Real‐Time RAN Intelligent Controller
nFAPI
Networked Fronthaul Application Platform Interface
NFV
Network Function Virtualization
NG
Next Generation
NG‐RAN
Next Generation RAN
NIST
National Institute of Standards and Technology
NTN
Non‐terrestrial network
Non‐RT RIC
Non‐Real‐Time RAN Intelligent Controller
NR
5G New Radio
NSA
non‐stand‐alone, in relation to 5G architecture
OAM
Operations, Administration and Maintenance
OFDM
Orthogonal Frequency Division Multiplexing
ONAP
Open Network Automation Platform
OOBE
Out of Band Emission
OS
Operating System
OTT
Over The Top
O‐Cloud
O‐RAN Cloud
O‐CU‐CP
O‐RAN Central Unit Control Plane.
O‐CU‐UP
O‐RAN Central Unit User Plane
O‐DU
O‐RAN Distributed Unit
O‐eNB
O‐RAN eNB
O‐RAN
Open RAN, also short for O‐RAN ALLIANCE
(o‐ran.org)
O‐RU
O‐RAN Radio Unit
OLT
Optical Line Terminal
ONU
Optical Network Unit
OFH or Open FH
Open Fronthaul
OpenRAN
Short for OpenRAN project group in Telecom Infra Project (TIP)
ONF
Open networking foundation
(opennetworking.org)
OTIC
Open test and integration center
PA
Power Amplifier
PaaS
Platform as a Service
PAPR
Peak to Average Power Ratio
PCIe
Peripheral Component Interconnect Express
PCP
Public Cloud Provider
PDCP
Packet Data Convergence Protocol
PDSCH
Physical Data Shared Channel
PE
Provider Edge
P‐GW
Packet Data Network Gateway
PHY
Physical Layer
PLMN
Public Land Mobile Network
PM
Performance Management
PMD
Poll Mode Driver
PNF
Physical Network Function
PRACH
Physical Random Access Channel
PRB
Physical Resource Block
PRTC
Primary Reference Time Clock
PSAP
Public Safety Answering Point
PSTN
Public Switched Telephone Network
PTP
Precision Time Protocol
PCI
Peripheral Component Interconnect
PDU
Protocol Data Unit
PKI
Public Key Infrastructure
PKIX
Public Key Infrastructure (X.509)
PON
Passive Optical Network
QoS
Quality of service
QoE
Quality of experience
QSFP
Quad Small Formfactor Pluggable
RAB
Radio Access Bearer
RAM
Random Access Memory
RAT
Radio Access Technology
RCEF
Radio Connection Establishment Failure
RDT
Resource Director Technology
RF
Radio Frequency
RFFE
RF Front End
RIC
RAN Intelligent Controller
RLC
Radio Link Layer
RLF
Radio Link Failure
RoE
Radio Over Ethernet
RRC
Radio Resource Control
RRH
Remote Radio Head
RRM
Radio Resource Management
RSRP
Reference Signal Received Power
RSRQ
Reference Signal Received Quality
RU
Radio Unit
Rx
Receive
RAN
Radio Access Network
RACH
Random Access Channel
rApp
Non‐RT RIC Application
RF
Radio Frequency
RL
Reinforcement Learning
RIA RAN
Intelligence and Automation
ROMA RAN
Orchestration and lifecycle Management Automation
RRU
Remote Radio Unit
RT
Real Time
SCTP
Stream Control Transmission Protocol
SDAP
Service Data Adaptation Protocol
SDL
Specification and Description Language
SDU
Service Data Unit
S‐GW
Serving Gateway
SLA
Service Level Agreement
SM
Service Model
SME
Service Management and Exposure
SMF
Session Management Function
SMO
Service and Management Orchestration
SMT
Simultaneous Multi Threading
SN
Sequence Number
SoC
System on Chip
SR
Segment Routing
SR‐IOV
Single Root I/O Virtualization
SW
Software
SyncE
Synchronous Ethernet
SA
Stand‐alone, in relation to 5G architecture
SAST
Static Application Security Testing
SBA
Service Based Architecture
SBOM
Software Bill of Materials
SCA
Software Composition Analysis
SCAS
Security Assurance Specifications
SCF
Small Cell Forum
SDN
Software Defined Networking
SDO
Standards development organization
SI
Systems integrator
SID
Segment identifier
SON
Self Organizing Network
SP
Service Provider
SSH
Secure Shell
SUT
System under test
T‐BC
Telecom Boundary Clock
TDD
Time Division Duplex
TNL
Transport Network Layer
TSC
Telecom Slave Clock
TTI
Trasmission Time Interval
TTLNA
Tower Top Low Noise Amplifier
Tx
Transmit
TCO
Total Cost of Ownership
TDMA
Time‐division multiple access
TIP
Telecom Infrastructure Project
(telecominfraproject.com)
TLS
Transport Layer Security
TN
Transport Node
TNE
Transport network elements
TR
Technical Report
TRP
Transmission and Reception Point
TS
Technical Specifications
TU
Transport Unit
UE
User Equipment
UL
Uplink
UMTS
Universal mobile telecommunication system
UNI
Universal network interface
UP
User Plane
UPF
User plane function
uRLLC
ultra‐reliable low‐latency communications
VIP
Virtual Internet Protocol
VLAN
Virtual Local Area Network
VM
Virtual Machine
VPN
Virtual Private Network
VNF
Virtualized Network Function
vRAN
Virtualized RAN
WCDMA
Wideband code‐division multiple access
WDM
Wavelength division multiplexing
WG
Working Group
xApp
Near‐RT RIC Application
xNF
Any Network Function
YANG
Yet Another Next Generation (Data Modeling Language)
ZTA
Zero Trust Architecture
1The Evolution of RAN
Sameh M. Yamany
VIAVI Solutions, Boulder, CO, USA
The last century marked the birth of the “Information Age,” ushering humanity into an era where access to knowledge and information fueled a global digital economy that pretty much changed every aspect of our lives. At the center of this transformation was the role played by the Telecommunications industry. It all started with the creation of the first computer networks in the 1950s. Then the global and ready access to information exploded in the 1980s with the introduction of the World Wide Web. Next, the evolution of wireless communication technologies allowed access to information not only from universities, offices, and homes, but from anywhere in the world at any time of the day. Finally, while the first two generations of mobile services were mainly built to support person‐to‐person calls as well as innovative messaging services, it was the invention of smartphones at the turn of the twenty‐first century, with instantaneous access to information, that led to the rise and proliferation of innovative apps and services that impacted the lives of billions of people around the world.
It is worth noting that the deployment of the fourth wireless generation (4G) of mobile technologies – often called the long‐term evolution or LTE – was one of the fastest in telecommunications history, adding over 2.5 billion subscribers in less than 5 years compared to 10 years for the third wireless generation to reach the same number of subscribers. The fifth generation (5G) that started in 2019 is predicted to reach three billion subscribers by the end of 2025, making its adoption even faster than 4G.
The Radio Access Network, or RAN, has been a critical component to all mobile generations. This chapter describes how the RAN evolved with each generation and the factors leading to the need for a new Open Radio Access Network (O‐RAN) architecture.
1.1 Introduction
According to the acclaimed book Sapiens: A Brief History of Humankind (Harari 2015), our kind – the modern humans – started to behave in a more intelligent and superior way some 70,000 years ago. One significant difference we had over the other archaic humans was our ability to imagine and envision a future state of our evolution and plan toward it. That unique feature transformed us from foragers to farmers and city dwellers. Then, around 500 years ago, the same quality ushered us into a scientific evolution, followed by an industrial revolution 250 years later that triggered our current information age era. Advanced communication was central to the industrial and information age revolutions. We can argue that smoke signals and drums were the first primitive modes of communication our kind utilized thousands of years ago. However, it was not until the early nineteenth century that the first electronic communication systems appeared.
As this book focuses on radio telecommunication, it is worth noting that the first use of radio signals in communications occurred in the 1920s. While the inventions of the telegraph and wired telephony had significant impacts on human life in the first half of the twentieth century, it was the people’s appetite to be able to communicate with each other, on the move, from anywhere and at any time, that ushered us into the mobile telecommunication era. The first five generations of mobile services were developed between the 1980s and the 2020s (Figure 1.1).
Figure 1.1 Five generations of mobile cellular networks.
Figure 1.2 Main components of a mobile network.
The RAN has been increasingly becoming the most valuable asset in mobile telecommunication systems and, over time, has shaped many of the innovations and acceleration of the information age revolution. A significant shift in RAN architecture was the move to packet‐switched data to improve data traffic throughput in 3G. Another major re‐architecture took place with the introduction of the LTE RAN. 5G RAN has been remodeled entirely to take advantage of software‐defined networking (SDN) and the virtualization and cloudification of the network functions.
A simple mobile network comprises three main components, as shown in Figure 1.2. The core network (CN) ensures subscribers get access to the services they are entitled to. The CN also contains the critical functions of authentication, location, mobility, and performing the necessary switching tasks. The RAN connects the user equipment (UE) to other network parts through a radio interface.
The data and signaling communications between any mobile network architecture components are governed by a set of standards‐defined protocols at every layer of interaction. A set of these protocols, as shown in Figure 1.3, determine how to set up and tear down signaling and communications between the mobile network elements. This set is mainly defined in the Control Plane or simply CP. Another set, called the User Plane or UP, enables the forwarding of data packets between the UE and the CN.
Several standards organizations develop and define mobile network protocols. All of them fall under the umbrella of the 3rd Generation Partnership Project (3GPP.org), which was established in 1998. The functional layers depicted in Figure 1.3 have all been specified and developed from Technical Specification (TS) documents within a 3GPP release. For example, the non‐access‐stratum (NAS) functional layer was specified by a particular 3GPP TS version to manage the setup and tear down of communications signaling between the UE and the CN and maintain these communication sessions as the UE moves throughout the network.
Another functional layer, the radio resource control (RRC), is responsible for the protocols between the UE and the Base Station. The RRC protocols’ main functions include broadcasting system information, contacting the UE and paging them, and modifying or releasing any active connections to the UE. It also takes care of the handover process between the different network‐defined cells. Another primary function of the RRC protocol layer is to report the transmission signal strengths from the different cellular towers as received by the UE.
Figure 1.3 Layers of the protocol stack of a 3GPP mobile network.
Other standard protocols for the RAN are the packet data convergence protocol (PDCP), responsible for the packet ciphering, data compression, and sequencing; the radio link control (RLC), responsible for error corrections and packets segmentation management; the media access control (MAC) performing the data multiplexing from different logical channels to be delivered to the air interface managed by the physical (PHY) functions.
1.2 RAN Architecture Evolution
To understand the history of advancements and innovations in mobile communication services, we must closely examine the drivers behind such explosive expansion over four decades going back to the 1980s. The primary force that ushered in the coming of the first generation (1G) mobile network was people’s excitement and new expectations that they could communicate with each other from anywhere and at any time. Long gone was the need to find a wired‐telephone post to call someone when your car broke down or you missed an important call from the office while shopping for groceries. Before cell phones became a reality, people used to call a place, not a person. Mobile communications changed that, and families and people found it easier to find each other at critical times, like being able to communicate emergencies or changes in kids pickup plans due to traffic jams.
The 1G voice services were purely analog and suffered from interference. As the number of users increased, it also lacked reliability and resiliency. The second generation mobile network, or 2G, moved from analog to digital, providing better quality and capacity. 2G also added a trendy feature, SMS, or Short Message Service, fashionably known as “texting.”
Texting ushered humanity into a new culture of communication. We were able to send quick and efficient notes (and later with shorthands and emojis) to inform each other we would be late, set up a quick meeting, or announce a new addition to the family, all without the need to make a call. With MMS (Multimedia Message Service), we shared photos from anywhere in the world and celebrated together, almost in real‐time, events thousands of miles away.
But we wanted more. We wanted to send emails on the go or access the internet from the malls. That is when improvement to 2G brought the 2.5G enhancements allowing the transfer of data packets over the mobile networks enabling subscribers to exchange email messages and browse the World Wide Web on the go.
As people’s appetites for data access grew, the need for more capacity in mobile networks led to the third generation, or 3G, that supported much higher data rates than 2.5G, letting users exchange emails and large photos faster and with higher quality than before. Also, 3G and 3.5G witnessed the debut of video calls using a new type of mobile phone, smartphones.
But it was not until 4G, referred to as LTE, that we fully witnessed the beginning of the era of smartphones and mobile devices. LTE was also the first fully IP‐based mobile network, thus enabling a plethora of innovative apps (short for mobile applications) encompassing every aspect of life, from music, food, shopping, TV, sports, games, social media, news, office and business, wellness, pet tracking, you name it.
While the first four generations of mobile networks were mainly focused on the users and subscribers, the explosive need for industrial automation, machine‐to‐machine communications, ultra‐low latency remote applications, gaming, autonomous driving, and the emergence of AI‐based IoT devices – all these new vertical industries required a completely new architecture for mobile networks. That was the start of the revolutionary 5G era.
1.2.1 The 2G RAN
The second generation (2G) mobile network design was essentially aimed at providing digital voice services and a moderate connection to data services. The 2G RAN architecture was labeled the Global System for Mobile communications or GSM, and it used TDMA (Time Division Multiple Access) for radio resource sharing, replacing the 1G analog systems.
The 2G RAN, shown in Figure 1.4, had two main components. The first was the BTS, or base transceiver station, which housed the radio resources. The deployment of several BTSs would be grouped within a particular geography and managed by one BSC or a base station controller. BSC supports many cellular functions within the BTS group, including handover scenarios, RF channel assignments, and the collection and maintenance of the different cell configuration parameters.
With the need to provide additional data access, the GSM, mainly circuit‐switched‐based, was improved to provide packet‐based data connections. These middle‐of‐the‐road improvements toward the third generation were called the GPRS, or General Packet Radio Services, sometimes labeled 2.5G. Still, the 2.5G RAN had a fundamental flaw; it was not designed from the ground up to support connection to all attached GPRS‐capable phones even when they had very low data usage; hence, the third‐generation RAN was needed with full‐fledged packet‐based data access architecture.
Figure 1.4 Simplified view of a 2G network.
1.2.2 The 3G RAN
The 3rd‐generation mobile networks started in the late 1990s and early 2000s and were deployed initially in Japan, Europe, and the United States with the intent to co‐exist and eventually replace the 2G/2.5G mobile infrastructure.
The 3G mobile RAN used a Wideband CDMA (WCDMA) radio physical layer and was technically labeled the UTRAN architecture, where UTRAN stood for universal mobile telecommunication system (UMTS) terrestrial RAN. The 3G RAN system, shown in Figure 1.5, had two new components; the first was the NodeB, replacing the BTS system in the 2G network, and the second was the radio network controller, or RNC, responsible for coordinating radio resources and mobility between several NodeBs.
The 3G deployment was a great success story in telecommunication history, and it fueled significant growth in subscriber numbers because it supported much higher data rates than the 2G system. Toward the mid‐2000s, a new kind of cellular phone was being designed, the smartphone. However, the 3G network architecture did not foresee the demand from these new smartphones to be “always‐on” and connected all the time to support new types of applications or apps running on these devices. These apps were characterized by low average data rates, with occasional high peak usage and low latency requirements.
An evolved 3G architecture was designed and implemented to address these shortcomings in the 3GPP release‐five (Rel‐5). The new RAN design used a High‐Speed Downlink Packet Access or HSDPA for data access. The 3GPP Rel‐6 defined another High‐Speed Uplink Packet Access or HSUPA, and Rel‐7 upgraded both these features and became known collectively as the HSPA+ enhancements, or more commonly, 3.5G, a precursor to the anticipated 4G 3GPP releases.
1.2.3 The 4G/LTE RAN
While most of the telecom service providers around the world were busy during most parts of the 2010s deploying and expanding their 3G and 3.5G networks, there was another threatening and competing technology based on the IEEE 802.16 standard on the rise – the WiMAX, short for Worldwide Interoperability for Microwave Access. WiMAX proponents claimed their technology already satisfied the major fourth‐generation mobile network requirements defined by the International Telecommunication Union (ITU), in particular reaching speeds of up to 100 megabits per second, which was a leapfrog from the current 3.5G speeds. WiMAX also pushed to replace and dominate the last‐mile broadband access for residential and enterprise customers. The threat presented by WiMAX created a sense of urgency among the traditional telcos and led 3GPP to accelerate the release of the anticipated LTE standards. In addition to the WiMAX frenzy, the need to have a common standardized worldwide roaming motivated many telcos, particularly those that used CDMA in 3G, to migrate to the LTE standard much faster.
Figure 1.5 Simplified 3G/3.5G RAN architecture.
Figure 1.6 shows a simplified LTE RAN architecture. One of the significant differences from previous RAN designs was the elimination of the RNC. Instead, a new element was introduced, the evolved NodeB, or eNodeB, designed to connect to an IP‐based network from the get‐go. The eNodeB was smaller in size yet more efficient and high performing, benefiting from advances in microprocessor chips and smaller RAM components. LTE also expanded the use of a Remote Radio Head (RRH) connecting to the eNodeB with an optical fiber and using the Common Public Radio Interface (CPRI) standards for communication and managing the radio resources and the RF spectrum.
The initial deployment of LTE networks was the fastest in telecommunications history, yet the promised high‐speed rates were not initially achieved. It was not until 3GPP Rel‐10, famously known as LTE‐Advanced, that the anticipated increased peak rates were achieved using a new technology called carrier aggregation, in which up to five carriers provided a 100 MHz total bandwidth. Another enhancement in Rel‐10 was the use of Multi‐Input Multi‐Output (MIMO) antenna technology in which 8 × 8 MIMO was used for downlink and 4 × 4 MIMO for uplink.
Figure 1.6 Simplified 4G/LTE RAN architecture.
Figure 1.7 The 4.5G RAN architecture.
With the fast expansion of smartphones and mobile device applications and the explosion of data traffic on the wireless network, it became apparent to the LTE network operators that the geographical distribution of traffic demand was not the same everywhere. As a result, coverage and capacity became significant concerns impacting customer experience and satisfaction. While macro cells provided connectivity at wider geographical ranges, the coverage performance at the edge of the cells suffered considerably. The idea of smaller cells was born to solve many of these issues. While small‐cell antennas only cover smaller geographical areas, they provide better connectivity consistency, reliable coverage within their range, and more flexibility to combat interference and blind spots. This network densification led to an exponential increase in the number of RRHs, and it became cost prohibitive to attach an eNodeB to every RRH; hence came the introduction of a centralized pool of eNodeBs (sometimes called a BBU hotel) and the term centralized‐RAN or CRAN was born. At the same time, 3GPP introduced releases 13 and 14, giving rise to the LTE Pro (also known as 4.5G). Figure 1.7 shows an example of the 4.5G RAN with small‐cell and CRAN deployment.
By 2016, 4.5G networks provided increased data rates and higher bandwidth by enhancing carrier aggregation to support up to 32 simultaneous carriers, in addition to advancements in MIMO antennas from 16 to 64 elements. Another innovation in 4.5G was the introduction of two‐dimensional beamforming technology. While beamforming was invented in the 1940s, it was not until the late 2010s when beamforming was introduced to wireless communication systems. In simple terms, beamforming technologies focus the radio signal transmission toward a target receiver, a cell phone in this case, rather than having the signal widely broadcasted in all directions. Such focus transmission can be performed horizontally in 2D or can be additionally narrowed down vertically in 3D.
1.2.4 The 5G RAN
The first two decades of the twenty‐first century witnessed several advances in using artificial intelligence in many aspects of life. In particular, industrial automation and the rise of cloud service providers allowed enterprises and people to work and access their business applications and IT services remotely. They could scale up and scale down their computing and storage needs without too much upfront capital investment. Also, the threat from non‐traditional communication providers and over‐the‐top players providing new innovative and free services led the traditional network operators to re‐evaluate their strategy and design a new network architecture that offered differentiated services and features and justified the ROI on their infrastructure CAPEX investments.
In addition to the above, the global mobile ARPU (Average Revenue Per User) kept trending down. Yet, the new demand from industry verticals for the machine to machine (M2M) communications and everything connected to everything (e.g. automotive, drones, agriculture, utilities, airports, port authorities, and shipping) provided a new source of revenue besides subscribers’ usage of the mobile services and the mobile M2M market was estimated to grow at a stunning double‐digit CAGR percentage. However, these exciting new opportunities for the mobile network needed a new generational mobile network design to support essential features such as high throughputs, dynamic adaptability, network slicing, and ultra‐reliable low latency (Grijpink et al. 2018). The new 5G network requirements – issued in 2015 by the ITU Radiocommunication Sector in their International Mobile Telelcommuncations‐2020 (IMT‐2020) Standard – came to fulfill these promises (Figure 1.8).
Figure 1.8 ITU IMT‐2020‐standard vision.
Figure 1.9 The evolution from 2G RAN to 5G RAN.
To deliver on the ITU IMT‐2020 requirement, the 5G RAN architecture (shown in Figure 1.9) had to be disaggregated and provide flexibility and adaptability for different use cases that sometimes had contradicting and orthogonal demands.
