Private 5G: A Systems Approach

Private 5G: A Systems Approach

Larry Peterson, Oguz Sunay, and Bruce Davie

Table of Contents

Foreword

Preface

Acknowledgements

Chapter 1: Introduction

1.1 Standardization Landscape

1.2 Access Networks

1.3 Managed Cloud Service

1.4 Beyond 5G

Chapter 2: Architecture

2.1 Overview

2.2 Radio Transmission

2.3 Radio Access Network

2.4 Mobile Core

2.5 Managed Cloud Service

Chapter 3: Radio Transmission

3.1 Coding and Modulation

3.2 Scheduler

3.3 Virtualized Scheduler (Slicing)

3.4 New Use Cases

Chapter 4: Radio Access Network

4.1 Packet Processing Pipeline

4.2 Split RAN

4.3 Software-Defined RAN

4.4 Near Real-Time RIC

4.5 Control Loops

Chapter 5: Mobile Core

5.1 Identity Management

5.2 Functional Components

5.3 Control Plane

5.4 User Plane

Chapter 6: Managed Cloud Service

6.1 Building Blocks

6.2 Example Deployment

6.3 Cloud Management Platform

6.4 Connectivity API

Appendix A: Aether Software

A.1 Overview

A.2 Quick Start

A.3 Closer Look

A.4 Scale Cluster

A.5 Verify Network

A.6 Emulated RAN

A.7 Physical RAN

A.8 Runtime Control

About The Book

Read the Book

Build the Book

Contribute to the Book

About The Authors

Foreword

When I was a graduate student studying parallel computing in the early 1990s, the World Wide Web exploded onto the scene, and I wanted to understand how the Internet made such rapid advances possible. I picked up a copy of the first edition of Computer Networks: A Systems Approach, and I started reading. I was delighted to learn not only the Internet’s history and main concepts, but also to see examples of real code that illustrated how the protocols actually worked and how they could be changed. I was hooked. I loved the idea of working in the computer networking field, where the technologies we build can help bring people together and lower the barriers to innovation so that anyone who can write software can contribute.

As time went on, I saw that, while the Internet enabled rapid advances in end-host applications, the inside of the Internet was harder to change. Network devices were closed and proprietary, and protocol standards evolved slowly and painfully. In response, enabling innovation inside the network became a passion of mine, and of many other technologists eager to make the Internet better–more secure, performant, reliable, cost-effective, and easier to manage. Gradually, the computer networking field changed, with the advent of software-defined networking, giving network owners–such as the hyperscalers running large data centers–much more control over the software inside their networks. (See Software-Defined Networks: A Systems Approach for more of this story!) Nowadays, computer networking really is about software. It’s a welcome change.

In recent years, the excitement has moved to the network edge with the emergence of 5G cellular access networks. No longer are wireless communication, computer networking, and cloud computing siloed parts of some larger ecosystem. They are brought together, allowing wireless devices to connect to nearby computing resources. Far beyond providing mobile Internet access, these networks enable exciting real-time applications like augmented and virtual reality (AR/VR), Internet of Things (IoT), self-driving cars, drones, robotic control, and more. Plus, these networks are not only the purview of large carriers that must invest significant resources in wireless spectrum, cell towers, and more. Rather, individual enterprises, campuses, and communities are deploying private 5G within their own organizations to support their own applications, using lightly regulated spectrum like CBRS (Citizens Broadband Radio Service). Opportunities for innovation abound!

However, now there is so much more to learn, to understand the many parts of 5G access networks as a single coherent system. The learning curve can be steep. Even fairly technical people usually know one or at most two parts of the system, and do not know how the parts relate to the larger whole. For example, I knew a good amount about computer networking, a little about cloud computing, and not much about wireless communication. Private 5G: A Systems Approach–this book–changed that. I learned what I needed to know about the radio access network, and how the pieces come together to be more than the sum of their parts. More than that, the book shows that, despite the complexity of the 3GPP cellular standards and the long and frustrating history of closed network equipment in the cellular networking space, open source software is gaining a foothold. Open source platforms like Aether and Magma–both discussed in this book–are seeing practical deployment in a wide variety of settings. The book even has a guide for readers to bring up the Aether platform, including a 5G small cell.

For me, then, the story comes full circle. Private 5G networks are something you can touch, code, and deploy yourself. Armed with the knowledge of how 5G access networks work, and with hands-on experience with open source software, just imagine the places you’ll go!

Jennifer Rexford

Princeton, New Jersey

Preface

When we wrote our introductory 5G book three years ago, our goal was to help people with experience building Internet and cloud services to understand the opportunity to bring best practices from those systems to the mobile cellular network. On paper (and in the press) 5G had set an ambitious goal of transformative changes, adopting a cloud-inspired architecture and supporting a new set of innovative services. But the gap between that aspirational story and the reality of 40 years of network operators and hardware vendors protecting their incumbent advantages made for a challenging pivot. So we started with the basics, and set out to explain the fundamental networking concepts and design principles behind the myriad of acronyms that dominate mobile cellular networking.

Because 5G adopts many of the principles of cloud native systems, it promises to bring the feature velocity of the cloud to Telco environments. That promise is being delivered most successfully in private 5G deployments that are less constrained by existing Telco organizations and legacy infrastructure. What started out as sketches on a whiteboard three years ago is now becoming a reality: Several cloud providers are offering private 5G solutions for enterprises, and there is a complete open source implementation of a 5G-enabled edge cloud that the Internet community can learn from and build upon.

The architecture described in this book is not limited to private deployments. It includes the necessary background information about the mobile cellular network, much of which is rooted in its origin story as a Telco voice network, but the overarching theme is to describe the network through the lens of private deployments of 5G connectivity as a managed cloud service. This includes adopting best practices in horizontally scalable microservices, Software-Defined Networking (SDN), and cloud operational practices such as DevOps. These practices are appropriate for traditional operators, cloud providers, and enterprises alike, but it is emerging use cases in private deployments that will benefit first.

The book makes extensive use of open source software—specifically, the Aether and Magma projects—to illustrate how Private 5G can be realized in practice. The availability of open software informs our understanding of what has historically been a proprietary and opaque system. The result complements the low-level engineering documents that are available online (and to which we provide links) with an architectural roadmap for anyone trying to understand all the moving parts, how they fit together, and how they can be operationalized. And once you’re done reading the book, we encourage you to jump into the hands-on appendix that walks you through the step-by-step process of deploying that software in your own local computing environment.

Acknowledgements

The software described in this book is due to the hard work of the ONF engineering team, the Magma engineering team, and the open source communities that work with them. Bilal Saleem did the heavy lifting on Aether OnRamp (described in the Appendix), with a special thanks to Ajay Thakur, Andy Bavier, Gabriel Arrobo, and Muhammad Shahbaz for their guidance and feedback.

Thanks to the members of the community who contributed text or corrections to the book, including:

Edmar Candeia Gurjão

Muhammad Shahbaz

Mugahed Izzeldin

Robert MacDavid

Simon Leinen

Tiago Barros

Gabriel Arrobo

Ajay Thakur

The picture of a Magma deployment in Chapter 5 was provided by Shaddi Hasan. The cover photo is by Erwan Hesry and published on Unsplash.

Larry Peterson, Oguz Sunay, and Bruce Davie

November 2023

Chapter 1: Introduction

Mobile networks, which have a 40-year history that parallels the Internet’s, have undergone significant change. The first two generations supported voice and then text, with 3G defining the transition to broadband access, supporting data rates measured in hundreds of kilobits per second. Today, the industry is transitioning from 4G (with data rates typically measured in the few megabits per second) to 5G, with the promise of a tenfold increase in data rates.

But 5G is about much more than increased bandwidth. 5G represents a fundamental rearchitecting of the access network in a way that leverages several key technology trends and sets it on a path to enable much greater innovation. In the same way that 3G defined the transition from voice to broadband, 5G’s promise is primarily about the transition from a single access service (broadband connectivity) to a richer collection of edge services and devices. 5G is expected to provide support for immersive user interfaces (e.g., Augmented Reality, Virtual Reality), mission-critical applications (e.g., public safety, autonomous vehicles), and the Internet of Things (IoT). Because these use cases will include everything from home appliances to industrial robots to self-driving cars, 5G will support not only humans accessing the Internet from their smartphones, but also swarms of autonomous devices working together on their behalf.

There is more to supporting these services than just improving bandwidth or latency to individual users. As we will see, a fundamentally different edge network architecture is required. The requirements for this architecture are ambitious, and can be illustrated by three classes of capabilities:

To support Massive Internet of Things, potentially including devices with ultra-low energy (10+ years of battery life), ultra-low complexity (10s of bits per second), and ultra-high density (1 million nodes per square kilometer).

To support Mission-Critical Control, potentially including ultra-high availability (greater than 99.999% or five nines), ultra-low latency (as low as 1 ms), and extreme mobility (up to 100 km/h).

To support Enhanced Mobile Broadband, potentially including extreme data rates (multi-Gbps peak, 100+ Mbps sustained) and extreme capacity (10 Tbps of aggregate throughput per square kilometer).

These targets will certainly not be met overnight, but that’s in keeping with each generation of the mobile network being a decade-long endeavor.

On top of these quantitative improvements to the capabilities of the access network, 5G is being viewed as a chance for building a platform to support innovation. Whereas prior access networks were generally optimized for known services (such as voice calls and SMS), the Internet has been hugely successful in large part because it supported a wide range of applications that were not even thought of when it was first designed. The 5G network is designed with this same goal: enabling future applications beyond those we fully recognize today. For an example of the grand vision for 5G, see the whitepaper from one of the industry leaders.

Further Reading

Qualcomm Whitepaper. Making 5G NR a Reality. December 2016.

The 5G mobile network, because it is on an evolutionary path and not a point solution, includes standardized specifications, a range of implementation choices, and a long list of aspirational goals. Because this leaves so much room for interpretation, our approach to describing 5G is grounded in three mutually supportive principles. The first is to apply a systems lens, which is to say, we explain the sequence of design decisions that lead to a solution rather than fall back on enumerating the overwhelming number of acronyms or individual point technologies as a fait accompli. The second is to aggressively disaggregate the system. Building a disaggregated, virtualized, and software-defined 5G access network is the direction the industry is already headed (for good technical and business reasons), but breaking the 5G network down into its elemental components is also the best way to explain how 5G works.

The third principle is to illustrate how 5G can be realized in practice by drawing on specific engineering decisions made in an open source implementation. This implementation leverages best practices in building cloud apps, which is an essential aspect of 5G evolving into a platform for new services. This implementation also targets enterprises that are increasingly deploying 5G locally, and using it to help automate their manufacturing, retail, and business practices—a trend that has been dubbed Industry 4.0. Such enterprise-level deployments are known as Private 5G, but there is nothing about the technical approach that couldn’t be adopted throughout the more traditional public mobile network that comes to mind when you think about your cell service today. The only difference is that private deployments are more aggressively embracing the cloud practices that will ultimately distinguish 5G from earlier generations.

Further Reading

K. Schwab. The Fourth Industrial Revolution. World Economic Forum.

What this all means is that there is no simple definition of 5G, any more than there is for the Internet. It is a complex and evolving system, constrained by a set of standards that purposely give all the stakeholders many degrees of freedom. In the chapters that follow, it should be clear from the context whether we are talking about standards (what everyone must do to interoperate), trends (where the industry seems to be headed), or implementation choices (examples to make