spects (Part 1) This chapter describes the theoretical and practical aspects of physical layer protocols and functional processing in 3GPP new radio. As shown in Fig. 3.1, the physical layer is the lowest protocol layer in baseband signal processing that interfaces with the digital and the analog radio frontends and the physical media (in this case air interface) through which the signal is transmitted and received. The physical layer further interfaces with the medium access control (MAC) sublayer and receives MAC PDUs and processes the transport blocks through channel coding, rate matching, interleaving/scrambling, baseband modulation, layer mapping for multi-antenna transmission, digital precoding, resource element mapping, orthogonal frequency division multiplexing (OFDM) modulation, and antenna mapping. The choice of appropriate modulation and coding scheme as well as multi-antenna transmission mode is critical to achieve the desired reliability/robustness (coverage) and system/user throughput in mobile communications. Typical mobile radio channels tend to be dispersive and time variant and exhibit severe Doppler effects, multipath delay variation, intra-cell and inter-cell interference, and fading. A good and robust design of the physical layer ensures that the system can robustly operate and overcome the above deleterious effects and can provide the maximum throughput and lowest latency under various operating conditions. Chapters 3 and 4 on physical layer in this book are dedicated to systematic design of physical layer protocols and functional blocks of 5G systems, the theoretical background on physical layer procedures, and perfor- mance evaluation of physical layer components. The theoretical background is provided to make the chapter self-contained and to ensure that the reader understands the underlying theory governing the operation of various functional blocks and procedures. While the focus is mainly on the techniques that were incorporated in the design of 3GPP NR physical layer, the author has a