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# <center><i class="fa fa-edit"></i> Introduction to FlexRIC</center>
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[TOC]

### INTRODUCTION
5G shifts the current paradigm beyond new radio and spectrum in three major areas:
- from monolithic to disaggregated architecture;
- from proprietary protocols and closed systems to commodity hardware and standardized interfaces;
- from a communicationoriented to service-oriented networking;

In general, what is needed from networking equipment, such as a base station, is simplicity, reliability and high-performance. Towards this end, the whitebox approach suggests a new model, where advanced networking with different or evolving use case-specific requirements is just general-purpose computing on commoditized equipment with possibility to remotely monitor, control and program network entities, known as software-defined networking (SDN). While the need for SDN in 5G and beyond is well-established, there is still a lack of proper software-defined radio access networking (SD-RAN) design and a prototype implementation that adheres to the fundamental design principles of 5G.

### FlexRAN

FlexRAN was the first attempt to realize a real time SD-RAN platform for research purposes. It applies the principles of SDN (i.e., decoupling of control plane and user plane) by defining a south-bound control protocol, which connects the radio access network (RAN) to a centralized controller. However, its protocol is tightly coupled with the underlying radio access technology (RAT), and its architectural design was not designed to support 5G’s required modularity for protocol and service extensions in a multi-RAT, multi-vendor environment.Further, FlexRAN adds overhead by requiring applications to poll for new messages (e.g., statistics updates). Additionally, FlexRAN does not scale as the number of UEs increases: for instance, we measured a x10 times more CPU usage and x3 times memory utilization in considered scenarios.

### O-RAN
O-RAN is a recent operator-led attempt to standardize SD-RAN by specifying the control protocol between the RAN and a RAN Intelligent Controller (RIC), termed E2. E2 exposes RAN internals to external applications (designated as “xApps”) to perform different tasks, e.g., radio resource management, through a set of “service models” (SM). SMs expose functionality that can be monitored or controlled, e.g., key performance indicators. For the purpose of validating the design, O-RAN provides a reference implementation of the RIC.

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