ntricity are met. This does not mean that member- ship is limited to operators only. Members include white box hardware, software, and sys- tems vendors as well as other companies in the wireless supply chain such as test equipment and component/silicon vendors and research institutes. The breakdown in Fig. 1-2 shows that the whole O-RAN supply chain is represented in an ever-growing list of members. Why now? None of the concepts that are discussed in O-RAN are groundbreaking in nature. This raises the question on why now "O-RAN" is such a buzzword. There are a couple of reasons to point out: Historical evidence. Much of what O-RAN is trying to achieve has already been shown effective in the wireline networking world. SDN defines a set of technologies (OpenFlow Chapter 1 Open radio access network overview Operator Academic, R&D, Standards SW & Services Device Vendor/Supply Chain Systems Test & Measure Integrator/Vendo HW & White FIGURE 1-2 O-RAN membership breakdown (start of 2021). O-RAN, Open Radio Access Networks. and others) that separate the wireline networking control plane from the user plane, allowing the user plane to be commoditized into white box hardware and the control plane to become fully software-defined. Early work on SDN was done by both the University of Stanford and the University of Berkeley, but by now, SDN is supported by all major networking vendors (Cisco, Juniper, and others) as well as a plethora of open- source options. An IDC estimate says that the SDN market will be worth more than $12 billion in 2022, with a CAGR of 18.5% during the 2017-22 period. This precedent is hard to ignore-why would the same not happen to wireless networking? Moore's law. As we will be showing next, the concepts on software-defined radio (SDR) were explored since the 2000s, but O-RAN is only getting serious consideration in the ~2020s. Why is this? One aspect to consider is the advancement in silicon technology that has made a move from proprietary application-specific integrated circuit (ASIC)- based implem