PTP (although the Power Profiles are not optimal for this task, other PTP profiles are designed for just this application-more on that later when addressing PTP in Chapter Backup PTP over WAN Power Profile in substations Figure 2-12 Backup Timing Across the WAN Although this example highlights a program from North America, there are similar projects under way across the globe. More information on the current and future methods of synchronization in the power grid is provided in "Chapter 3. Synchronization and Timing Concepts", and Chapter 9. Mobile operators have similar problems, whereby a cell radio is normally synchronized by a GNSS receiver but is vulnerable to being jammed and spoofed. Therefore, operators are rolling out similar solutions to provide a backup in the case of some localized GNSS outage. 2.4 Summary This chapter examined several practical use cases that require some combination of the synchroniz- ation of frequency, phase, and time. It demonstrated that this field has a lot of application outside the 5G space, which is currently the center of attention. Also, by examining the practical application of the techniques and methods, you gained a much clearer understanding of the technology beyond using an abstract treatment involving mathematics. Chapter 3. Synchronization and Timing Concepts In this chapter, you will learn the following: Synchronous networks overview: Presents an overview of synchronous networks and a com- parison of asynchronous and packet networks. Also defines frequency and phase synchroniza- tion as well as jitter and wander. Clocks: Provides details on oscillators, clock modes, and clock types, as well as clock stratum levels and quality. Sources of frequency, phase, and time: Explains sources of timing, with special focus on satellite systems and particularly the Global Positioning System (GPS). Also covers the short- range physical signals used to carry time. Timing distribution network: Describes different methods used to carry time and synchroniza- tion as well as the tran