a potential for an oligopoly that implies reduced innovation and increased pricing and vendor dependency. Lastly, there is a geopolitical aspect that worsens the competitive situation. There has been broad coverage on Huawei being banned as an infrastructure vendor, leading Huawei customers to reach out to find alternative paths to acquire equipment. Given the promise of O-RAN to open up a whole new ecosystem of hardware and soft- ware vendors, there is obvious excitement in the industry around the concept of a software- centric ecosystem of vendors that can be mix-and-matched to implement a wireless network, especially if this allows the wireless network to be composed out of systems that are opti- mized to the task at hand-say rural, dense urban, industrial, or private networks. Preface At the same time, there is a lot of catching up to do. The institutionalized knowledge from the big wireless systems vendors takes a long time to catch up to, in systems, hardware, and software design. This book is a jump-start to engineers who are developing O-RAN hard- ware and software systems and provides a top-down approach to O-RAN systems design. We cover wireless and systems history as an introduction into why wireless systems look the way they do today, before introducing relevant O-RAN and 3GPP standards. The remainder of the book discusses hardware and software aspects of O-RAN system design, including dimensioning and performance targets. We include real-life examples of relevant elements of detailed hardware and software design where needed as a guide for developers. Lastly, we show a few practical examples of where O-RAN designs play in the market and how those examples map to hardware and software architectures. The target audience includes hardware and software engineers as well as product managers and consumers of O-RAN products who are looking to understand better what O-RAN is. This book is organized as follows: Chapter 1, Open Radio Access Network Overview, gives an overview of the O-RAN stan- dard and its or