cture. We learned that NR is OFDM-based with scalable subcarrier spacing. This changes the slot durations to allow for different kinds of services, but it also presents challenges regarding how these different subcarrier spacings can be multiplexed in the frequency domain without interfering between them. We have also discovered that NR supports a slot-based scheduling mode. We saw that there are several interesting use cases that necessitate the introduction of this scheduling mode, such as LTE/NR coexistence or forward compatibility. Finally, we have described the dynamic TDD duplexing mode that NR introduces and how it is signaled to devices by using the slot format indication. In the next chapter, we are going to learn about initial access and management. We will refer to physical channels and signals frequently to better understand the initial access procedure. 5G Air Interface and Physical Layer Procedures - Part 2 The next New Radio (NR) concept that we will cover in this chapter is the initial access to a network and beam management procedures. These procedures are new to NR, and there is nothing similar in Long-Term Evolution (LTE), especially for initial access. As we will see during this chapter, both millimeter wave operation and reducing the number of signals that are always transmitted are the two main drivers for this initial access procedure design. Upon completion of this chapter, we will understand the concept of beam sweeping and especially its relationship with Millimeter Wave (mmWave) frequency. We will focus on how a device and the gNB can identify the best special beams to be used for transmission. We will also describe the beamforming's effect on the initial access procedure. Upon completion of this chapter, we will understand some of the design decisions regarding initial access, as well as how decisions can enable LTE-NR coexistence in the same radio frequency. In this chapter, we'll cover the following topics: Initial access and beam management Physical channels and signals for the init