# Fronthaul interface and functional split for FAPI. Small Cell Forum.
###### tags: `Internship 2nd level`

:::success
**Goal:**
- Understanding of the Fronthaul interface.
- Figured it out which functional split is acceptable for FAPI.
- Overvew of Small Cell Forum.
**Resources:**
- [The main features of a fronthaul interface](https://www.ericsson.com/en/blog/2021/6/ieee-open-fronthaul-standard)
- [Small Cell Forum](https://www.smallcellforum.org/about-us/)
- [The best functional split for FAPI](https://www.telecomsinfrastructure.com/2019/07/small-cell-forum-releases-5g-fapi-api.html)
- [Small Cell Forum webinar](https://www.youtube.com/watch?v=U9mD_0Twtvs)
:::

## Fronthaul interface
In cellular network deployments, radio units and their antenna systems are often separated from their baseband units (or radio equipment controllers). Traditionally this separation was just for analog radio frequency (RF) signals and the distance was limited from the top of the tower to the bottom. However, service providers soon saw cost advantages to pooling their radio equipment controllers in a central location to serve antennas on many towers. This fronthaul connection, so-called since it was the opposite of the well-known backhaul connection, was based on the industry standard Common Public Radio Interface (CPRI). Due to the latency and latency variation (jitter) constraints of CPRI, as well as its high bandwidth, fronthaul has traditionally been deployed as point-to-point fiber.
During the development of 5G, as radio equipment controllers were decomposed, the widely adopted CPRI fronthaul interface was being enhanced to make the fronthaul interface feasible in a packet network, such as a switched Ethernet network. In the industry, this sparked many discussions as to which functions besides RF could be moved closer to the antenna in the radio equipment.
At the same time, we began to see the potential for further cost savings, driven in part by industry demand. What if our customers’ networks could support a mix of fronthaul and backhaul traffic along with non-cellular traffic like residential broadband and enterprise service traffic? With that, the vision of a single packet transport network was born.


## About the Small Cell Forum.
Is a global membership organization committed to supporting agile, low-cost mobile infrastructure through small cells. Our mission is to make mobile cellular connectivity an accessible resource for organizations of all sizes, and to support digital transformation of industry, enterprise and communities.
We gather requirements from service providers and businesses, and directed by our Board, these inputs shape our work program. Our specifications, technical papers and enterprise-focused outputs are made freely available to benefit the wider industry.
Today our members are working on projects spanning split architectures, Edge computing, private networks, neutral host requirements, 5G small cell products, and policy and regulation.

## A functional split for FAPI.
The Forum also maintains the widely adopted FAPI specifications for 3G and LTE, as well as networked FAPI (nFAPI) for LTE supporting a MAC/PHY functional split, a key enabler for virtualisation of higher layer base station functions. In 5G this split point was also identified by 3GPP and called split option 6.