Along with long-term evolution (LTE), 5G promises not only high-speed data rate transferring but also Internet of Things (IoT) services, edge computing, and more. This book covers the technical details of 5G and the open radio access network (O-RAN) platform from an engineering-centric point of view. It excellently combines theoretical concepts with the practical and technical aspects of wireless communication in 5G.
A wireless communication ecosystem can be recognized as three major sections: the core systems, the mediator system, and the air interface. The core systems section is like a data center, and the third section, the air interface, communicates with user equipment (UE) and is based on coding, modulation theories, and waveform signaling techniques. In between these two, in the second section, the mediator system handles the messaging streaming process from the first section and prepares the disseminating packets for the third section, as well as the reverse, with plenty of complex duties that the book thoroughly covers. This section enforces quality of service (QoS) flow policies, dictates security restrictions, and performs scheduling and priority rules; the hardware components, software modules, and precise synchronization mechanisms are detailed perfectly here. In this regard, hardware and software systems, scheduling, and synchronization mechanisms are the main topics of the book, with a glimpse at testing techniques in wireless communication.
O-RAN aims to generalize the software-centric techniques to radio access networks (RANs), medium access control (MAC), and physical layers beyond higher level stacks, deploying Linux-based general-purpose processors (GPPs) rather than an application-specific integrated system (ASIC). Using these features along with chip data converting integration, chip partitioning, Ethernet-based multiple chip integration, and modern memory interfaces, O-RAN’s superiority is clear.
The central theme of the hardware discussion is dimensioning and scaling. While the central unit (CU), the distributed unit (DU), and the radio unit (RU) are the main components of the mediator section and hardware hosts, dimensioning indicates how to estimate the required hardware capabilities to respond to their requirements in a sustainable manner considering latency and performance. At different levels of the system, the impact of various factors (for example, number of accepted users, network components, CU and RAN bandwidth and latency) are evaluated against different hardware platforms: network processors, field-programmable gate arrays (FPGAs), ASIC, and multicore central processing units (CPUs). The impact of offloading hardware at different layers cannot be ignored. The influence of cache hierarchy in a system on chip (SoC) platform, hybrid automatic repeat request (HARQ), memory size, and bandwidth dimensioning are explained.
Scaling is the criterion for choosing the hardware architecture at implementation of O-RAN functionalities in the different levels (data center, cell site, CU/DU small cell, and integrated small cell). Normally they have different requirements in front-haul bandwidth and MAC/PHY throughput. The mechanisms for scaling without changing the device family (changing core frequency, core scaling, adding or removing devices, hardware accelerators or number of blades in a chassis or number of chassis in a deployed system) with the possible development cycle are considered. The text prepares readers for the hardware-choosing process. The selection mechanisms for popular platforms (Multi-core CPU, X86,Arm and RISC-V) are provided with the related performance benchmarking. The chapter that covers this is full of worthy technical tips.
Software issues have a special place in O-RAN, which has a software-centric nature. The book compares microcontroller and microprocessor systems, and looks at the Linux OS’s many capabilities: maturity in structure, long-term maintainability, and portability. According to the 3rd Generation Partnership Project (3GPP) standards, O-RAN systems are running on Linux with a trend toward software abstraction and the potential for reuse and standardization. Linux is somehow heavy and wasn’t originally tailored for wireless communication (where real-time operations and timing synchronization are key issues). In this regard, the cokernel approach, PREEMPT_RT, and user-space application programming interfaces (APIs) can mitigate the effects of real-time, latency, and OS overhead challenges. Many topics are explored, including low peripheral and accelerator access, static memory management and the removal of recursion algorithms, buffer and memory management methods, and inline versus lookaside accelerators. Moreover, a chapter dedicated to software performance issues (in mostly wireless communication environments) discusses performance mindset lemmas, critical performance components and validation, the model, and performance metrics. Performance use case components in wireless communication, the packet processing cycle budget, physical layer complexity analysis, and software implementation optimization techniques are also discussed.
The book also covers the important topics of wireless schedulers and synchronization. The scheduling chapter starts with orthogonal frequency-division multiplexing (OFDM) and then explains opportunistic scheduling and QoS scheduling. It also proposes an algorithm for base station wireless scheduling. The synchronization chapter begins with a fundamental discussion about the meaning of frequency and time. Following a brief introduction to O-RAN synchronization parameters, the chapter nicely details network-based synchronization techniques. It is a comprehensive look at O-RAN synchronization and sync solution implementation issues.
This insightful book not only explains the different dimensions of the O-RAN technology, but also provides valuable information about wireless communication. It is highly recommended for engineers who are eager to learn more about O-RAN software and hardware systems.
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