SCF’s 5G nFAPI interface is a critical enabler of robust open networks

Perhaps the most important development in the RAN of the 5G era is disaggregation. This splits the network’s functions between multiple elements, supporting a high degree of flexibility and scalability. Operators want even more than that however – a key requirement is to be able to mix and match components and software from different suppliers easily, which in turn opens up the ecosystem to new competition and innovation.

SCF’s latest release, 5G nFAPI 1.0, goes a long way to fulfil that vision.

True openness is required to transform mobile operator economics in the 5G era. But it  relies on the interfaces between the network elements being standardized promptly, and with robust specifications that can be trusted and adopted by all vendors and deployers. SCF has mobilized its decade-long experience in developing robust common interfaces, to address operators’ demand for an open midhaul interface between the radio unit (RU) and the distributed unit (DU) in a disaggregated RAN.

This interface, 5G nFAPI (network functional API), addresses 3GPP’s Split 6 option for allocating network functions within a disaggregated RAN – in  this case a physical RU which supports the Layer 1 5G New Radio functions, and a virtualised DU running Layers 2 functions.

By providing an open interface, 5G nFAPI allows an RU and DU from different suppliers to work together automatically without the operator having to invest in expensive engineering.

A challenge for any open technology is gaining operator trust that it will perform as well as proprietary, integrated systems. Recent SCF operator surveys indicate that more than three-quarters of MNOs want to implement open disaggregated RAN by 2025, and that the small cell layer is where many will start. But more than half say they will not embark on this journey until they have full confidence in the interfaces.

Robust specifications that are firmly based on operator requirements, and that quickly gain the support and confidence of the supply chain, are fundamental to success.

This is where SCF’s experience of defining open interfaces has proved so valuable. Since our foundation, we have based our technical work on inputs from service providers, so every spec has directly addressed a market need. That, in turn, has helped to spur adoption across the industry, leading to open systems in commercial reality, not just on the page.

5G nFAPI leverages SCF FAPI specifications which have been developed for 3G, 4G and 5G and are used inside vast majority of independent small cells deployed today. FAPI provides standard internal interfaces between components that make up a small cell system-on-chip (SoC). It is supported by every major component provider in the sector and has matured over several generations. nFAPI is an external network interface, which wraps the 5G FAPI APIs in a transport mechanism to support interworking between radio and DU elements.

Published this week, it will provide a significant boost to the goal of achieving open, interoperable 5G networks. It will enable vendors to develop open elements quickly and stimulate operator tests and deployments, which in turn will build the confidence that is essential to success in any open platform.

Not that 5G nFAPI 1.0 is the end of the journey. SCF members are already working on further stages of technical and ecosystem evolution. As with release 1.0, this will be aligned closely with operator requirements and the inputs of members, and no doubt there will be further refinement of the priorities in response to industry reaction to 5G nFAPI 1.0.

Among the developments already planned for 5G nFAPI are enhancements to the data path transport as well as support for the full 5G FAPI API suite with P19 front end control and the P4 network monitor mode.

The release of 5G nFAPI 1.0 is timely, coming at a critical juncture when operators want to stop just discussing open interoperable networks and to start trialling and deploying them. Based as it is on inputs from so many key industry operators and vendors, and on a decade of experience of defining open networks, the new interface will play a significant role in making multivendor, disaggregated RANs a commercial reality in the early 2020s.