igins and covers related topics like 5G and spectral availability for 5G deploy- ment. This provides a background for a discussion on deployment options, which defines the hardware and software architecture. Chapter 2, System Components, Requirements, and Interfaces, outlines the requirements and architecture of key system components such as the central unit (CU), distributed unit (DU) and RU. Chapter 3, Hardware System Dimensioning, establishes key performance metrics such as front/backhaul throughputs, memory requirements, interconnect performance, as well as latency and other metrics. Chapter 4, Hardware Architecture Choices, talks about the different hardware implementa- tion options, from server-based designs to more embedded implementation options for CU/ DU as well as options for RU system design. We discuss the pros and cons of each architec- ture approach. Chapter 5, System Software, is like the hardware architecture choice but more software centric in nature. We cover os components such as Linux and DPDK/bbdev as well as required software drivers. Chapter 6, User-Plane Application Components, covers relevant details of the Physical and Layer 2 application stacks. We outline functions implemented by these stacks. This includes 3GPP defined functions such as PDCP, RLC/MAC, and PHY and implementation-specific parts such as Air Interface Scheduler, O-RAN eCPRI fronthaul, and DFE. Chapter 7, Wireless Scheduling and Quality of Service Optimization Techniques, delves deeper into the most complex and differentiating piece of the User-Plane stack: the wireless scheduler algorithm. We explain commonly used algorithms for time and frequency domain scheduling and outline the potential structure of a scheduling algorithmic framework. Chapter 8, Synchronization in Open Radio Access Networks, covers requirements as well as implementation on CU/DU and RU side for time and frequency synchronization including relevant standards and implementation methods. xvi Preface Chapter 9, Software Performance, discusses key perform