5G FAPI standard

Why this work matters

FAPI is a common standard agreed between chipset and component suppliers and mobile base station integrators. It is an API for hardware components implementing 3GPP physical layer functions and “software stacks” implementing higher layers. Since SCF created the standard, FAPI has been widely adopted in the vast majority of 2G, 3G and 4G system-on-a-chip based small cells.


SCF has now published five specifications within 5G FAPI, its landmark family of common interfaces. The suite is regularly updated to ensure it meets industry needs and aligns with 3GPP standards.

5G FAPI: PHY API Specification

PHY FAPI is the main API for FAPI, defining P5 and P7 interfaces for user and control plane into the PHY. Its typical application is between a PHY layer System on a Chip and the software stack for MAC and higher layer protocols. It can also be used to enable Embedded NIC Inline Accelerators for the High-PHY function in an O-RAN DU. This latest iteration brings the L1/L2 interface support to a fully cloudified environment; it also further advances MIMO signalling to support new architectures and macro deployments.

Other specifications in the FAPI suite include:

  • ‘5G FAPI: RF and Digital Front End Control API’ – (P19) for Frontend Unit control [SCF223]
  • ‘Network Monitor Mode API’ – (P4) for 2G/3G/4G/5G [SCF224]
  • ‘5G nFAPI Specification’ [SCF225]
  • ‘5G FAPI Operations, Administration and Maintenance (OAM) Protocol for Inline High-PHY’ [SCF229]

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