The Radio Access Network (RAN) is the segment of cellular networks that provides wireless connectivity to end-users. The O-RAN Alliance has been transforming the RAN industry by proposing open RAN specifications and the programmable Non-Real-Time and Near-Real-Time RAN Intelligent Controllers (Non-RT RIC and Near-RT RIC). Both RICs provide platforms for running applications called rApps and xApps, respectively, to optimize the RAN behavior. We investigate the disaggregation of the Near-RT RIC into components that meet stringent latency requirements while presenting a cost-effective solution. For example, the O-RAN Signalling Storm Protection requires the Near-RT RIC to support end-to-end control loop latencies as low as 10 ms. We propose the novel RIC Orchestrator (RIC-O) that optimizes the deployment of the Near-RT RIC components across the cloud-edge continuum. Edge computing nodes often present limited resources and are expensive compared to cloud computing. Performance-critical components of Near-RT RIC and certain xApps should run at the edge while other components can run on the cloud. Furthermore, RIC-O employs an efficient strategy to react to sudden changes and re-deploy components dynamically. The proposal is evaluated both analytically and through real-world experiments in an extended Kubernetes deployment implementing RIC-O and the disaggregated Near-RT RIC.

This article investigates the deployment of a Near-Real-Time Radio Access Network (RAN) Intelligent Controller (near-RT RIC) on a distributed cloud infrastructure composed of multiple physical sites with different amounts of resources and associated costs. The challenge is dynamically adapting the near-RT RIC deployment to the most cost-effective arrangement while meeting the latency requirements between the near-RT RIC and the controlled nodes. We introduce an optimization model to solve the disaggregated near-RT RIC placement problem, considering a cloud-native infrastructure to minimize the placement cost while satisfying the latency-sensitive control loop requirements across the cloud-edge continuum. Moreover, we describe an experimental environment we created using geographically disparate cloud sites. We present data detailing the latencies of the communication links among these sites and the costs incurred in using this real-world infrastructure. We conduct a performance evaluation of the near-RT RIC deployment, comparing the distributed approach versus a traditional monolithic strategy and evaluating positioning costs, deployment, setup and registration times, and the control loop latency considering three scenarios. Our results show that in a cloud-native environment, the disaggregated near-RT RIC allows cost savings of up to 60% in comparison to a monolithic near-RT RIC while satisfying the control loop latency and achieving time efficiency in terms of deployment and registration of xApps and near-RT RIC components.

The proper execution and management of heterogeneous Virtualized Network Functions (VNFs) relies on the employment of efficient and comprehensive VNF platforms. However, current systems are developed without following any standardized reference architecture, thus leading to proprietary and monolithic solutions. Furthermore, those platforms lack support for recent NFV developements, such as VNF Components (VNFC) and the Network Service Header (NSH). In this work, we present an architecture for VNF platforms that is fully compliant with the European Telecommunications Standards Institute (ETSI) NFV architecture, while also enabling the execution of both VNFC and NSH. Through the development of a system prototype called COmprehensive VirtualizEd NF (COVEN) platform, we were able to evaluate the effectiveness of our proposed architecture and to demonstrate the benefits of supporting VNFC and NSH, such as flexibility and efficiency.

The deployment of services in virtualized networks can be done by composing multiple Virtualized Network Functions (VNFs). A Service Function Chain (SFC) consists of a predefined sequence of VNFs which are virtually connected and through which traffic is processed. This work proposes a framework for composing and managing the lifecycle of SFCs formed by VNFs built with Click-on-OSv. The proposal allows the execution of SFCs on different NFV orchestrators. We call the proposed approach "holistic" as it defines a generic API for the composition of SFCs that leverages particular details of different NFV orchestrators. A prototype of the framework was implemented to allow the composition and lifecycle management of SFCs formed by VNFs built with Click-on-OSv on the OpenStack Tacker NFV orchestrator. Results show that the framework is scalable and efficient.