The Open Networking Foundation (ONF) announced the formation of the SD-RAN project (Software Defined Radio Access Network) to pursue the creation of open source software platforms for mobile 4G and 5G RAN deployments. Initially, the project will focus on building an open source Near Real-Time RAN Intelligent Controller (nRT-RIC) compatible with the O-RAN architecture. Initial support for the project comes from AT&T, China Mobile, China Unicom, Deutsche Telekom, Facebook, Google, Intel, NTT, Radisys and Sercomm.
A primary goal of the SD-RAN project is to enable an external intelligent controller so that operators have both visibility and control over their RAN, including ownership and control over how spectrum is utilized and optimized. The initial development work in the new ONF project focuses on a near-real time RIC called µONOS-RIC (pronounced “micro-ONOS-RIC”).
µONOS is a microservices-based SDN controller created by the refactoring and enhancement of ONOS, the SDN controller developed by ONF for operators which is already in production tier-1 networks worldwide. µONOS-RIC is built on µONOS, and hence features a cloud-native design supporting active-active clustering for scalability, performance and high availability along with the real-time capabilities needed for intelligent RAN control.
µONOS-RIC is designed to control an array of multi-vendor open RAN equipment consistent with the O-RAN Alliance architecture. In particular, the O-RAN Alliance E2 interface is used to interface between µONOS-RIC and the vendor-supplied RAN RU/DU/CU RAN components. Apps running on top of the µONOS-RIC are responsible for functionality that traditionally has come from vendor-proprietary systems.
Complementing work at O-RAN Alliance, TIP
The participating members of the SD-RAN project plan to prototype and trial an advanced architecture that enables intelligent RIC xApps to control a broad spectrum of SON and RRM functionality that historically has been implemented as vendor-proprietary features on bespoke base station equipment and platforms. The work is seen as complementary to various efforts across the industry, including within the O-RAN Alliance, the O-RAN software community and the TIP OpenRAN Project Group.
SD-RAN will follow O-RAN specifications as they are developed and will also make use of components of existing open source to facilitate interoperability. As the project pioneers new functionality, all extensions and learnings that come from building the system will be contributed back to O-RAN Alliance, with the intent that these extensions can inform and advance the O-RAN specifications.
Furthermore, the TIP OpenRAN 5G NR Project Group recently launched the RAN Intelligence and Automation (RIA) subgroup to develop and deploy AI/ML based applications (as xApps) for a variety of RAN use cases including SON, RRM and massive MIMO. TIP’s RIA subgroup will use ONF’s uONOS-RIC platform, leveraging open interfaces based on O-RAN specifications to assemble solutions for use case development, testing and deployment.
Field trial in 2021
The SD-RAN project already has a working skeleton prototype of the µONOS-RIC controller above a RAN emulation platform through the E2 interface. This implementation is demonstrating handover and load balancing at scale, supporting over 100 base stations and 100,000 user devices with less than 50ms handover latency (less than 10ms latency for 99 percent of all handovers).
The aim is to hold a first field trial by early 2021, working with RAN vendors to integrate carrier-grade RU/DU/CU components while in parallel implementing xApps to demonstrate SON and RRM functionality. Interested parties are encouraged to contact ONF for additional information.
