Small Cell Forum publishes spec for unified 5G open RAN

small cells
The specification was developed through a collaboration of companies across the small cell ecosystem. (Pixabay)

The Small Cell Forum (SCF) is trying to stimulate competition in 5G small cell software and equipment by publishing the PHY API that provides an open and interoperable interface between the physical layer and the MAC layer.

The specification was developed through a collaboration of companies, including Intel, Qualcomm Technologies, Airspan and Picocom.

According to the SCF, 5G femto application platform interface (FAPI) is an initiative within the small cell industry to encourage competition and innovation among suppliers of platform hardware, platform software and application software by providing a common API around which suppliers of each component can compete. By so doing, SCF said it provides an interchangeability of parts, ensuring that the system vendors can take advantage of the latest innovations in silicon and software with minimum barriers to entry—and the least amount of custom re-engineering.

The move comes as operators continue on a broad front to move away from the proprietary hardware of yesteryear to more modern open and interoperable systems. As the SCF explained, a critical interface as networks get disaggregated is the fronthaul between a distributed unit (DU) for radio functions and a centralized unit (CU) for protocol stacks and baseband functions. Open specifications such as SCF’s FAPI are designed to enable operators to mix and match protocol stacks, basebands and radios from different vendors and get the benefits of deploying disaggregated, virtualized RAN (vRAN) networks.

“The economic success of 5G is reliant on interoperable multivendor networks, which require open interfaces at both silicon and network level,” said SCF Chairman David Orloff in a statement. “These uniform specifications for equipment and interfaces will enable limitless flexibility in how cells are deployed and which form factors and suppliers are included. Specifications such as 5G FAPI are key to accelerating the progress towards fully deployable, commercially viable dense 5G networks.”

The forum already has completed a lot of work in the LTE world, where its motivation for defining networked FAPI (nFAPI) was to establish a scalable ecosystem with a converged approach to virtualization across multiple suppliers. It says the continued adoption of NFV/SDN makes this is even more crucial for 5G.  

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The small cell market is guaranteed to grow with 5G. Mobile Experts expects the small cell market to continue growing at a 10% CAGR over the next five years to reach $5.2 billion by 2024, with private LTE and 5G as big growth drivers. The firm predicts “substantial adoption” of CBRS, LAA and Wi-Fi connectivity in small cells as a low-cost way for carriers to add capacity to their networks.