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radisys.com 31 Radisys Series — Who Disaggregated My RAN? eBook Most of the initial implementations of virtualized machines for telco products adopted the strategy of creating multiple virtual machines within the same host hardware. The telco world capitalized on this strategy and much of the cloud implementation, mostly on the core network, was moved to virtualized implementations called Virtualized Network Functions (VNF). Some of the LTE network core network implementations started adopting control and user plane separation and virtualization, and many of these implementations were compliant to ETSI NFV architecture. RAN Specific Challenges in Virtualization While the virtualization principles can be applied to RAN nodes as well, there are some specific challenges especially in processing related to Layer 1 and Layer 2 functionalities. Meeting the tight timing and latency constraints in the RAN data path can be a challenge. It is also harder to separate out tightly intertwined functions and call processing across Layer 1 and Layer 2 modules. With the advent of many fast data path options and hardware accelerators, some of these challenges were solved. Intel's FlexRAN solution was one of the earliest reference designs made available for RAN vendors to start the journey to virtualized RAN implementations. Radisys and Intel have been partnering since the initial release of FlexRAN reference design to provide 4G and 5G virtualized RAN solutions. Going Cloud Native Another important trend in cloud computing has been the widespread use of containers to implement cloud- based solutions. This allows a lightweight and efficient way of spinning many instances of network functions rather than creating many virtual machine instances. This approach, called Cloud-native Network Function (CNF) is now being adopted by many vendors to virtualize the RAN. There are many design paradigms like microservices- based architecture and stateless processing in network functions that can be applied to create high performance and highly scalable RAN solutions. The goal is to design highly granular software modules and make them scale dynamically as per demand. O-RAN Cloud Architecture for RAN As operators are moving forward with their O-RAN deployments, the question remains of which virtualization approach to take: VNF or CNF? The answer to that question is in many ways subjective. Open RAN allows for either option in some of the nodes. The O-RAN Alliance uses a neutral term – "cloudified" – to represent both VNF and CNF. The O-RAN Alliance has a working group that is focused on cloudification and orchestration for RAN nodes. The O-RAN Cloud (called O-Cloud) platform is illustrated in the diagram on the next page.

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