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ONF clarifies role of SD-RAN in O-RAN AllianceONF clarifies role of SD-RAN in O-RAN Alliance

The Open Networking Foundation said its SD-RAN project will fit inside of the work of the O-RAN Alliance.

October 14, 2020

4 Min Read
ONF clarifies role of SD-RAN in O-RAN Alliance

MENLO PARK, Calif. – Open RAN is an important and fast moving space that has been gaining tremendous momentum over the last two years. ONF recently announced our SD-RAN project to help advance open RAN, backed by the founding members: AT&T, China Mobile, China Unicom, Deutsche Telekom, Facebook, Google, Intel, NTT, Radisys and Sercomm.

We, the ONF Board, want to take a moment to clarify how the SD-RAN project supplements and supports the work of the O-RAN ALLIANCE and the broader open RAN movement. In addition, we want to highlight how SD-RAN is working towards three specific near-term deliverables designed to help accelerate the availability and adoption of O-RAN conformant solutions.


O-RAN ALLIANCE is leading the industry in open RAN, defining the disaggregated architecture and open interfaces between the disaggregated components. O-RAN has defined a horizontal disaggregation of the RAN into the RU/DU/CU, which is already enabling a first order of interoperability with some early adopters mixing RUs with DU/CUs from different vendors via open fronthaul interfaces. This is a terrific first step on the open RAN journey.

O-RAN is also defining a vertical disaggregation, lifting control functionality out of the DU/CU into a Near-Real Time RAN Intelligent Controller (nRT-RIC), with a goal for xApps running on the nRT-RIC to be able to implement advanced SON and RRM functionality that would otherwise run embedded in the CU and DU or in other bespoke vendor-specific platforms. This level of disaggregation is still being fully defined by O-RAN, and this is where the ONF believes it can add value with an open source implementation.

ONF's SD-RAN will leverage the O-RAN architecture and vision for the nRT-RIC. SD-RAN will implement an open source nRT-RIC (called µONOS-RIC) and exemplar xApps including implementations for handover and load balancing, and will then prototype and work with operators to trial combinations of these open components with vendor proprietary (or other open versions) of RU/DU/CU, RIC and xApps.

SD-RAN will follow O-RAN specifications as they are developed. As the SD-RAN 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 help advance the O-RAN specifications. In particular:

Deliverable #1

SD-RAN will prototype extensions to the data models for the E2 and A1 interfaces to enable flexibility and support for a broad set of xApp functions and applications, with a specific goal of enabling a robust spectrum of RRM and SON functionality within xApps.


The SD-RAN community will also be collaborating with the OSC, with the intent that interoperable nRT-RIC implementations will come out of both efforts. Specifically, we would like to see that a mix of open source and vendor proprietary components can be assembled, demonstrated and ultimately deployed. Specifically:

Deliverable #2

The SD-RAN project plans to contribute an SDK for the northbound interfaces from the nRT-RIC towards the xApps to support and promote availability of interoperable xApps and rApps.

Deliverable #3

SD-RAN exemplar xApps will help demonstrate xApp interoperability between OSC NR-RIC and ONF µONOS-RIC.


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 open source µONOS-RIC platform, leveraging open interfaces based on O-RAN specifications to assemble solutions for use case development, testing and deployment.


ONF's SD-RAN project is backed by a consortium of leading operators and aligned technology companies and organizations that together are committed to creating a truly open RAN ecosystem. Notably, SD-RAN's backers include the founders and current leadership for O-RAN (AT&T, China Mobile, China Unicom and Deutsche Telekom), and SD-RAN's work is building on the architectural work being championed by O-RAN.

Our overarching goal is to help to create an end-to-end software SD-RAN stack adhering to the O-RAN architecture and specifications. The founding members of the SD-RAN project believe the project can help invigorate an ecosystem of interoperable open RAN components, and SD-RAN project members are committed to delivering O-RAN conformant RU/DU/CU devices and to working with the community to help assemble open solutions.

The ONF has a history of successfully applied disaggregation, white box and open source principles to the packet switching, broadband/PON and optical transport domains, and we are excited to now be applying what we have learned (and the software platforms we have developed) to the open RAN domain to help promote the open RAN ambitions of operators and the broader industry.


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