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 for software stacks implementing MAC and higher layers.
The SCF says the FAPI has already been widely adopted in the vast majority of 3G and 4G SoC-based small cells. Significant updates to the specifications in this release include:
- Support for two additional 3GPP Release 16 features: low-PAPR RS and 2-step RACH, for increased cell coverage and reduced access latency;
- Changes to support multi-user MIMO and massive MIMO, based on sounding reference signals (SRS), for increased cell capacity;
- High-performance operation (Control/User Plane separation, efficient padding, efficient DL Rate Matching, etc.), by reducing processing overhead;
- Alignment with split Option 7-2x, one of the split options adopted by O-RAN fronthaul specifications, for easier integration;
- Maintenance for continued support of Release 15.
The FAPI specification has evolved over more than 10 years to keep ahead of market requirements. This update demonstrates the ongoing commitment of the ecosystem to continually improve the standard, adding new features and maintaining existing ones, the SCF stated.
“The current 5G PHY FAPI release represents a further maturation of the FAPI specifications, including a significant leap from an exclusive focus on the architectures generally associated with small cells, to now support architectures where the cloud boundary might lie between high PHY and low PHY with split option 7-2x,” said Qualcomm Technologies FAPI rapporteur and senior staff engineer Andrei Radulescu.
“The latest iterations of the specifications also reflect a focus on not just functionality but performance.”
“All RANs have MAC-PHY interfaces. With small cells, the MAC and the PHY are usually provided by different vendors, and FAPI has enabled an open ecosystem”, added Picocom director of product management and FAPI Lead Vicky Messer.
“With Open RAN, a standardised MAC-PHY interface is essential for all classes of cell, and the Small Cell Forum has risen to the challenge of enhancing the FAPI specifications to embrace new requirements,” concluded Messer.
“We have a strong team of SCF members supporting the ongoing review and maintenance of these specifications going forward, and a clear roadmap for future developments,” concluded Radulescu.
To download the 5G FAPI specifications go here.
This first appeared in the subscription newsletter CommsWire on 15 November 2021.
