This book is an introduction to fifth‐generation (5G) mobile telecommunication systems.

5G builds on earlier generations of mobile telecommunications, but it differs in several ways. It is designed for a wider range of applications than before: not only consumer applications such as voice, video and data, but also industrial applications such as machine‐type communications. In turn, those applications have a wider range of requirements than before: some require a peak data rate of several gigabits per second, others require the delivery of data packets with delays as low as a few milliseconds, while others require a battery life of several years. To help meet those requirements, the network uses technologies such as network function virtualization, software‐defined networking and network slicing, so as to provide a flexible, underlying resource that can be easily reconfigured to support new requirements as they arise. In pursuit of higher data rates and higher system capacities, the air interface supports higher radio frequencies than previous generations have done, and makes extensive use of multiple antennas.

There are many other books on 5G which contain detailed accounts of the underlying technologies, the likely applications, the system architecture and the air interface. The aim of this book is to complement them by offering an end‐to‐end, system‐level perspective. It contains fewer details about individual topics than many of the others, but it is broader in scope, covering the requirements and architecture of 5G, the principles and implementation of the air interface and the signalling procedures within the network. It is aimed at mobile telecommunication engineers who want an introduction to the architecture and operation of 5G; at those who are experts in one part of the system, but who want to understand what is taking place elsewhere; and as a technical foundation for those in related roles such as management, marketing, intellectual property and consultancy.

The first few chapters cover the foundations. Chapter 1 reviews the history of mobile telecommunications, and introduces the applications, requirements and key technical features of 5G. Chapter 2 covers the architecture of the core network and the signalling protocols that it uses, while Chapter 3 covers similar ground in the case of the radio access network.

The next three chapters address the underlying technologies that are used by the air interface. Chapter 4 reviews the use of radio spectrum, and discusses the coverage issues that appear when operating at high radio frequencies. Chapter 5 reviews the techniques that are used for digital signal processing, for example modulation, demodulation, orthogonal frequency division multiple access and error correction. (Much of that chapter has been condensed from the author's previous work, ‘An Introduction to LTE’.) Chapter 6 explains how 5G uses multiple antennas to compensate for the coverage problems that appear at high radio frequencies, and to improve the system capacity when the radio frequency is low.

The next six chapters describe how the air interface is actually implemented. Chapter 7 is an introduction to the air interface, while Chapter 8 describes the acquisition procedure in which a mobile discovers a nearby cell, and Chapter 9 describes the random access procedure in which the mobile makes its initial communication. Chapter 10 covers the procedures for link adaptation, which compensate for changes in the amplitude and phase of the incoming radio signal, and help to control the use of multiple antennas. Chapter 11 addresses the procedures that are used for scheduling and data transmission, while Chapter 12 explains how the air interface's higher‐level protocols handle tasks such as scheduling and re‐transmission.

We then move on to the end‐to‐end operation of 5G. Chapter 13 covers the procedures that a mobile runs when it switches on, to discover a nearby cell and register with its chosen network. Chapter 14 addresses the security procedures in 5G, while Chapter 15 covers the procedures which connect a mobile to an external data network, and which allow an external application server to monitor and influence its behaviour.

The next four chapters address different aspects of mobility management, in which the network keeps track of the mobile's location and controls the cells with which it is communicating. Chapter 16 covers the procedures in a state known as RRC_CONNECTED, in which the mobile is carrying out normal communications with the network. Chapter 17 addresses the state of RRC_IDLE, in which the mobile is on standby, while Chapter 18 deals with the new state of RRC_INACTIVE, which is an optimization for low data rate communications. Chapter 19 covers the procedures used for inter‐operation between the core networks of 4G and 5G. As the final topic, Chapter 20 addresses the enhancements that have been made to 5G in the most recent release of the specifications, and reviews some of the plans for future releases.

Like any technical subject, 5G uses a large number of acronyms and abbreviations. To help make the text readable, I have tried to strike a balance between the uses of abbreviations and text, for example by using ‘downlink’ in place of DL, but AMF in place of ‘access and mobility management function’. New terms are highlighted in italics throughout the text, and there is a full list of abbreviations at the start of the book.

Unavoidably, some of the topics are mathematical ones. Some previous knowledge of Fourier transforms would help the reader understand the discussion of orthogonal frequency division multiple access in Chapter 5. Similarly, some previous knowledge of matrices would help with the discussion of multiple antennas in Chapter 6, while familiarity with complex numbers would be helpful for both. However, I have attempted to make the maths as lightweight as possible, and to explain the important concepts using English instead. The Bibliography contains some references for further reading.