By David Orloff

One of the most exciting developments in the industry in the past year has been serious momentum building behind a fully open RAN. Small Cell Forum has been contributing to multivendor, interoperable networks for a decade, and now its efforts are set to play a central role in emerging 5G platforms.

With the open RAN set to be a significant theme of this year’s Mobile World Congress, SCF’s latest work on common interfaces will be hugely topical. We are officially announcing one of our most significant work items for 2019, 5G FAPI This project will result in two sets of APIs (application programming interfaces), which will support openness at chip and network levels.

Both are 5G iterations of mature and well-established SCF technologies for 4G. Both enable something that has been near-impossible in the macro RAN, until now – interoperability, allowing deployers to mix and match elements from different suppliers to achieve the optimal solution for their particular needs, and to introduce significant price competition into the ecosystem.

This is very important to operators. In a survey of over 70 MNOs, conducted by Rethink Technology Research at the end of 2018, over two-thirds of respondents said that opening up their supply chain, and achieving multivendor systems, were among their top 10 commercial goals for 5G.

However, over half of those operators added that they lacked confidence in being able to achieve the goal before 2025. That is why initiatives like 5G FAPI are so critical. They show how openness can be achieved in the small cell network, where it is easier to drive this change because there is less vendor incumbency; a track record of competition and innovation; and open specs have been the norm from the earliest days of the industry, when SCF successfully submitted its Iuh interface to 3GPP.

The first 5G FAPI release is an extension of the original FAPI specifications, which are incorporated in most small cell chips today. The specs define internal interfaces between the chipset and software layers, allowing for interoperability between the 3G, 4G or 5G PHY, and software elements such as the security coprocessor or scheduler. This addresses a gap in current 3GPP specs, and has backing from a wide range of influential companies, including both Intel and Qualcomm.

Then, 5G nFAPI (network FAPI) extends the concept to virtualized small cell networks and provides an interface between the remote radio unit (RRU), and a centralized baseband unit (BBU), on which some or all of the baseband functions are virtualized. This will be especially important to indoor enterprise networks, which are critical to many 5G use cases. In that environment, nFAPI will be essential to support the most common architecture – a group of cells controlled by a central, virtualized unit.

As in the days of Iuh, working with standards bodies will be important in the 5G era too, to ensure SCF developments become as mainstream as possible, and help the industry to gravitate to a deployable set of specifications – at a time when there is great uncertainty about which particular aspects of 3GPP’s complex standards will be broadly implemented. Confidence that a technology will be well-supported is critical to uptake of dense 5G, and while the industry at large still has to decide which of the 3GPP’s defined splits for virtualized RANs to prioritize, SCF is wholly focused on one architecture, which will enable real world 5G use cases. This will reduce time to market for commercial equipment.

It will also be important to work with open source initiatives, which are having an increasingly strong influence over the evolution of new architectures and supply chains. SCF has already announced a cooperation with Open Air Interface (OAI) to place 5G FAPI into open source, and so attract even more innovation to the platform, and we are sure other partnerships will follow in the emerging open source RAN ecosystem.

In terms of driving economically attractive deployments of dense HetNets, 5G FAPI – combined with its established 4G counterparts – could prove to be SCF’s most significant development to date.