ications. Let us take an example of legacy RAN deployment and show how the O-RAN concept applies there. See Figure 12.9: Service Service Service Service Service Service Service Transport Network SW Vendor 1 Open RAN software Commercial off the Shelf (COTS) Servers Open RAN hardware Figure 12.9 - A legacy RAN deployment [image credit: Sanya] Understanding O-RAN From the bottom up, the layer consists of the RAN hardware and software. In legacy deployments, the use of propriety hardware from a specific vendor dictated the use of the same hardware for the full deployment over the life cycle. Likewise, this locked the operator into using corresponding proprietary software, shown as SW Vendor 1. With the emergence of O-RAN, as new hardware appears on the market with enhanced capabilities, mixing and matching is possible. Additionally, the loose coupling between the RAN hardware and software provides more flexibility to adopt these solutions over the life cycle of the RAN. This is absolutely critical in the era of massive supply chain disruptions during COVID-19 period, such as from 2020 to 2022. Furthermore, the global semiconductor crisis would have aggravated the problem further if no concept such as O-RAN was applied to 5G infrastructure, as the initial rollouts corresponded with this time period in several parts of the globe. Figure 12.10 shows how O-RAN allows the adoption of hardware from different vendors when new features are released in similar hardware from different vendors allowing mixing and matching at the O-RAN hardware layer: Service Service Service Service Service Service Service Transport Network SW Vendor 1 Open RAN software Commercial off the Shelf (COTS) Servers Open RAN hardware Figure 12.10 - A deployment based on O-RAN swapping hardware vendor [image credit: Sanya] Figure 12.11 shows similar flexibility at the O-RAN software layer allowing swapping of the RAN software stack in the RAN deployment life cycle: 5G Infrastructure Design Service Service Service Service Service Service Service Transpor