Chapter 3 - New Radio Access Physical Layer Aspects (Part 1)

Abstract

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. The physical layer further interfaces with the MAC sublayer 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, 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 these deleterious effects and can provide the maximum throughput and lowest latency under various operating conditions. In this chapter, the fundamental concepts and common features/functions in downlink and uplink of the new radio are studied, which include review of the characteristics of wireless channels in sub-6 GHz and mmWave frequency regions as well as the analysis of 2D and 3D channel models and propagation effects. We will then begin our top-down approach to physical layer protocols starting with waveforms, orthogonal and non-orthogonal multiple-access schemes, and duplex schemes as well as the operating frequencies of the new radio. The frame structure, OFDM numerologies, time-frequency resources, and resource allocation techniques will be discussed and analyzed from theoretical and practical point of views.