The transition to 5G is happening, and unless you’ve been actively trying to ignore it, you’ve undoubtedly heard the hype. But if you are like 99% of the CS-trained, systems-oriented, cloud-savvy people in the world, the cellular network is largely a mystery. You know it’s an important technology used in the last mile to connect people to the Internet, but you’ve otherwise abstracted it out of your scope-of-concerns.

The important thing to understand about 5G is that it implies much more than a generational upgrade in bandwidth. It involves transformative changes that blur the line between the access network and the cloud. And it will encompass enough value that it has the potential to turn the “Access-as-frontend-to-Internet” perspective on its head. We are just as likely to be talking about “Internet-as-backend-to-Access” ten years from now.

This book is written for someone that has a working understanding of the Internet and cloud, but has had limited success penetrating the myriad of acronyms that dominate cellular networking. In fairness, the Internet has its share of acronyms, but it also comes with a sufficient set of abstractions to help manage the complexity. It’s hard to say the same for the cellular network, where pulling on one thread seemingly unravels the entire space. It has also been the case that the cellular network had been largely hidden inside proprietary devices, which has made it impossible to figure it out for yourself.

This book is the result of a mobile networking expert teaching a systems person about 5G as we’ve collaborated on an open source 5G implementation. The material has been used to train other software developers, and we are hopeful it will be useful to anyone that wants a deeper understanding of 5G and the opportunity for innovation it provides. Readers that want hands-on experience can also access the open source software introduced in the book.

This book will likely be a work-in-progress for the foreseeable future. It’s not intended to be encyclopedic—favoring perspective and end-to-end completeness over every last bit of detail—but we do plan to flesh out the content over time. Your suggestions (and contributions) to this end are welcome.

Larry Peterson and Oğuz Sunay

Open Networking Foundation

June 2020

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 at 4G (supporting data rates typically measured in the few megabits-per-second) and starting the transition to 5G, with the promise of a tenfold increase in data rates.

But 5G is about much more than increased bandwidth. In the same way 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, including support for immersive user interfaces (e.g., AR/VR), 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 won’t just support humans accessing the Internet from their smartphones, but also swarms of autonomous devices working together on their behalf. All of this requires a fundamentally different architecture.

The requirements for this architecture are ambitious, and can be summarized as having three main objectives.

• 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 ultrahigh density (1 million nodes per square kilometer).

• To support Mission-Critical Control, potentially including ultra-high availability (greater than 10^–5 per ms), ultra-low latency (as low as 1 ms), and extreme mobility (up to 100 km/h).

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

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.

Further Reading

For an example of the grand vision for 5G from one of the industry leaders, see Making 5G NR a Reality. Qualcomm Whitepaper, 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 two 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 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. It also helps to illustrate how 5G might evolve in the future to provide even more value.

Evolutionary Path

That 5G is on an evolutionary path is the central theme of this СКАЧАТЬ

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