Network FAPI

nFAPI (network FAPI) provides a transport wrapper around the established FAPI PHY APIs to create a fronthaul interface between an S-RU (Small cell Radio Unit) and S-DU (Small cell Distributed Unit). These specifications enable open small cell networks, ensuring multi-vendor interoperability between S-RU and S-DU.

5G nFAPI specifications

The 5G network functional application platform interface (5G nFAPI) is an initiative that extends for 5G the functional split between the MAC and PHY functions that enables virtualization of the MAC function. This document defines a transportable interface for MAC-PHY 5G function application platform interface (5G-FAPI) defined for 5G small cells [SCF222]. This RAN architecture virtualization MAC function [SCF159] is also known as the Option 6 [3GPP TR 38.816, v15.0.0] architecture split.

S-RU and S-DU

S-RU and S-DU Test Support

5G nFAPI [SCF225] adds a network transport wrapper around the 5G FAPI PHY API [SCF222] to create the split 6 interface between S-RU and S-DU small cell network units which SCF describes as Open6. This paper is not a specification. It considers how to test the disaggregated units S-RU and S-DU of the RAN.

About nFAPI

About 5G nFAPI

SCF has released two iterations of its nFAPI specification that enable early implementations for evaluation by mobile operators and other small cell deployers. In this informative companion document to the normative specification we provide an overview of the specification’s application, a roadmap for ongoing feature implementation and ecosystem support, and an FAQ.


Evolving industry specifications

Network FAPI provides a ‘wrapper’ for PHY FAPI and RF FAPI to make them transportable over network interfaces. The FAPI and network FAPI together define the split option 6 network interface between S-RUs and S-DUs.

The main changes to the latest version of the nFAPI specifications include:

  • Support for the RF FAPI P19 interface, enabling rich configuration and analogue beam-forming over the network interface.
  • nFAPI framework robustness enhancements to handle S-DU and S-RU deployment scenarios.
  • P7 over Ethernet transport.
  • Hardware optimized nFAPI headers.
  • Maintenance updates and corrections.

SCF release papers

You might be interested in the following documents

5G FAPI: PHY API specification

This document provides the 5G PHY API specification for an application platform interface (API) between the MAC and PHY protocol layers within the small cell ecosystem.

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5G FAPI: P19 RF and digital frontend control API

This P19 interface specification serves as a companion to the 5G FAPI P5/P7 specification.

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5G FAPI: Network monitor mode API

The functional application platform interface (FAPI) is an initiative within the small cell industry released by the Small Cell Forum.

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