To support the diverse mixture of 5G use cases, the Small Cell Forum (SCF) has published a suite of documents to enable small cells to be constructed piece-by-piece, using components from different suppliers.

The objective for developing the 5G functional application platform interface (FAPI) is to stimulate a competitive ecosystem for suppliers of 5G small cell hardware, software and equipment. The 5G FAPI specifications define various hardware and software interfaces and are agnostic to the type of small cell RAN architecture.

“One of the most important parts the SCF’s remit is to create the right conditions for an open, multi-vendor ecosystem to flourish, driving competition and innovation. We anticipate that 5G FAPI will be universally adopted and implemented in all 5G RAN products, irrespective of which disaggregation network architecture is deployed,” said Prabhakar Chitrapu, chair of SCF and a member of the technical staff at AT&T.

The full set of specifications is available on the SCF website. The suite expands the 5G Physical Layer API specification published in July 2019 and includes two new specifications:

• SCF223: 5G NR FAPI P19 Front-End Interface Specification.
• SCF224: Network Monitor Mode API for Small Cells.

“5G-era networks will be very different from their predecessors, often disaggregated, with radio and baseband processes split in various ways between the cloud/data-centers and the cell site. They will also be very dense, with large numbers of small cells enhancing capacity to enable new classes of applications.” — Prabhakar Chitrapu

FAPI is an initiative within the small cell industry to encourage competition and innovation among suppliers of platform hardware, platform software and application software. It defines a common API which the suppliers of each component meet, ensuring interoperability and competition.

The API approach imitates a long engineering tradition of providing an “interchangeability of parts” to ensure that system suppliers can access the latest innovations in silicon and software, requiring the least amount of custom re-engineering.

The suite of 5G FAPI documents reflects the extended collaboration among companies involved in the small cell industry, including Cisco, Intel, ip.access, Picocom and Qualcomm Technologies.