Small Cell Forum enables mix-and-match small cell components

The SCF also published new APIs to assist in the management of smart antennas and for small cells to “listen” to each other. (Getty Images)

The Small Cell Forum (SCF) today published new specifications to enable small cells to be constructed piece-by-piece using components from different vendors. And it also published new APIs to assist in the management of smart antennas and for small cells to “listen” to each other.

Prabhakar Chitrapu, SCF Chair and lead member of the technical staff for AT&T Converged Access and Device Technology, explained that there are three different layers of vendors involved in the construction of small cells. There are the silicon vendors that produce the chips, field programmable gate arrays (FPGAs) and ASICs that are the “heart of the small cell.” Secondly, there are software vendors that write code for layers 2-7 of the small cell stack. And thirdly, there are the original equipment manufacturers (OEMs) who produce the hardware.

Prabhakar Chitrapu
Prabhakar Chitrapu

“Small cells used to be a single box, and you would just put them in a factory or on a lamp post,” said Chitrapu. “But now, that architecture of all-in-one-box is getting disaggregated. The idea is the piece that used to be the radio unit can be made more inexpensively. The centralized parts absorb most of the heavy lifting in terms of processing. Typically, you have a few central units and then many radio units.”

Disaggregation also leads toward more virtualization. “If you look at the radio unit, the technology is not there to make it virtualized because it’s so compute intensive,” said Chitrapu. “But if you look at the other boxes, they’re more amenable to virtualization.”

This means that these other boxes can be built with common-off-the-shelf hardware, running a variety of software, opening the door to new vendors in the small cell ecosystem. These vendors include traditional hardware suppliers like Dell Technologies and HPE. And software suppliers could include upstarts like Altiostar and Mavenir, for example.

The new specifications published today expand upon the 5G Physical Layer API specification, published in July 2019. That spec provides an open and interoperable interface between the physical layer and the MAC layer.

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Today’s release also includes two completely new specifications, SCF223: 5G NR FAPI P19 (an RF API) and SCF224 (a digital front-end API).

Chitrapu said the RF API addresses a need that’s arisen with 5G for the management of antennas. “Earlier, you had just one or two antennas,” he said. But now, with massive MIMO antennas and their capabilities for beamforming and beam-steering, “you need to manage those smart antennas,” he added. The RF API provides for that control and management.

Finally, the new digital front-end API addresses the “listening” ability of small cells. Chitrapu said there are so many more small cells being used for 5G densification, and they’re being deployed in an organic, somewhat hodge-podge manner. The new API helps the small cells to listen for other small cells in their vicinity, enabling self-organizing networks.

The Small Cell Forum’s latest APIs also incorporate recommendations from the OpenAirInterface Software Alliance.