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