igned to push the boundaries of mobile communications to unprecedented levels in terms of data rates, latency, reliability, and connectivity. Purposely versatile, 5G NR is engi- neered to address the needs, known and future, of many industries, to enable new ser- vices and experiences, through a high degree of in-built flexibility and configurability. Thus, an engineering challenge in itself, 5G NR is also a major engineering challenge for mobile device implementation, especially the modem. Indeed, the promise of 5G NR to deliver multi-Gbps data rates, ultra-reliability, and low latency is only viable if the overall complexity of the modem and its power consumption are all but fully mit- igated for mobile devices. This chapter provides expert insights into how this difficult equation can be resolved SO that 5G NR can quickly become a reality for consumers. It assumes a working knowledge of 5G NR, as described in other chapters. To shed light on these challenges, it is necessary to understand the basic structure of a modem and what constitutes its complexity. Figure 13.1 shows a generic block diagram inside a 5G modem System on Chip (SoC). It typically consists of a baseband process- ing unit, a mixed signal circuits unit, and a configurable RF circuits unit. Outside of the 5G Technology: 3GPP New Radio, First Edition. Edited by Harri Holma, Antti Toskala, and Takehiro Nakamura. © 2020 John Wiley & Sons Ltd. Published 2020 by John Wiley & Sons Ltd. 13 5G Modem Design Challenges 5G Modem SoC 5G NR Baseband Unit Control Path Hardware Hardware Hardware Module 1 Module 2 Module 3 Mixed-signal Internal circuits Memory Control Processor Configurable RF circuits PA/LNAs 4G LTE Antennas External Baseband Unit & Mixed-signal circuits Memory Figure 13.1 Generic 5G modem architecture. 5G modem SoC lie the external RF components such as the power amplifier/low-noise amplifier (PA/LNA) and antenna units, as well as an external (and less expensive) mem- ory unit that can be shared by other integrated circuits and the Applicatio