Small Cell Forum releases next generation 5G FAPI specifications demonstrating maturity of the interfaces and adding macro cell features
The suite of 5G FAPI specifications underpins the high-performance low-cost components integral to 5G mobile base stations, whether small cell or macro
London, UK – 16th June 2021 - Small Cell Forum (SCF) today announced the release of its updated 5G FAPI PHY and RF specifications, as well as an updated 5G network FAPI specification and a testing framework for S-RU and S-DUs. The updated specifications and new test support paper developed by the SCF membership demonstrate maturity and ongoing support for the FAPI interfaces, which are used in millions of the world’s System on a Chip small cells – and can now be used for macro cells as well.
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 MAC and higher layers.
FAPI has already been widely adopted in the vast majority of 3G and 4G SoC-based small cells. This update demonstrates the ongoing commitment of the ecosystem to continually improve the standard, adding new features and maintaining existing ones. The update also provides tighter integration between different specifications in the suite, enabling greater flexibility and more efficient implementations.
5G network API provides a wrapper around the other APIs to make them transportable over networks. Network FAPI 2.0 now adds support for the RF Front End Unit Control API in addition to the PHY API. The resulting combination is the Open6 fronthaul interface between an S-RU - implementing the PHY physical layer functions, and the S-DU - implementing MAC and above. All S-DU functions can be performed in software and can be virtualised.
The release documents are the result of intensive cooperation between SCF members from across the ecosystem and are available to download on the SCF website. The releases are as follows:
• 5G PHY FAPI, SCF222 v3.0, main data path and PHY mode control
• 5G RF FAPI, SCF223, v2.0, RF and Digital Front End Control API
• SON FAPI, SCF224 v1.0, network monitor mode for 2G-5G
• 5G Network FAPI, SCF225 2.0, transport wrapper for PHY and RF API
• S-RU and S-DU Test Support, SCF228 v1.0, conformance testing for Open6 products
“The 5G-FAPI specification suite continues to evolve and mature to meet the needs of an ever-wider range of network deployment scenarios for next generation networks, ” said Andrei Radulescu, FAPI Rapporteur and Senior Staff Engineer, Qualcomm Technologies Inc. “In addition to maturing support for 3GPP Rel-15, this latest update adds 3GPP Rel16 features, flexible interworking between PHY and RF APIs, and a unified message structure over internal and network interfaces. Ethernet and IP transport of PHY and RF APIs allow rich configuration and analogue beamforming over the network interface. In addition, the introduction of macro cell feature support brings high-performance, low-power components into 5G mobile base stations, of all types, whether small cell or macro.”
Ganesh Shenbagaraman, network FAPI Rapporteur and Head of Integrated Products and Ecosystems, Radisys, said: “SCF standards are enabling faster time to market for Open RAN solutions, with many small cell and DU products adopting the broader FAPI suite. This release of 5G nFAPI specification adds many optimizations and support of P19 interface over the network, paving the way for more advanced implementations.”
“SCF’s core remit is to create the right conditions for an open, multi-vendor ecosystem to flourish, driving competition and innovation, and our work around 5G FAPI lies at the centre of this, ” said Prabhakar Chitrapu, SCF Chair, said. “The enhancements being announced today will further help 5G FAPI to be universally adopted and implemented in all 5G-RAN products, irrespective of which disaggregation network architecture is deployed, enabling a vibrant multi-vendor ecosystem for 5G-era equipment lowering the barriers to entry both for suppliers and network deployers.”