d to small cells. mm Wave deployments will use small cells, but there will also be many small cells oper- ating in the sub-6 GHz frequency range. Private enterprise networks bring together technologies of small cells, edge services, and distributed EPC. 4 NG-RAN Architecture The small cell industry has developed common APIs to allow an open RAN small cell ecosystem. One of these APIs, called FAPI, is internal to a small cell and is widely adopted by the small cell industry. FAPI is defined between one instance of MAC and one instance of the PHY layer. nFAPI is a wrapper around FAPI that supports 3GPP split option 6 with the MAC located in a CU, and the PHY located in the DU. nFAPI is designed to operate over non-ideal connections such as Ethernet found in indoor enterprise small cell networks. 4.6.2 Market Drivers Interest in small cells and the continued drive to increase their deployment can be broadly split into two main market drivers: first, the desire to improve indoor coverage for mobile users; and second, the need to densify networks to support increasing data throughput demands. Indoor coverage for mobile users has always been problematic due to the challenges of radio waves propagating into buildings. This challenge is becoming progressively harder as the insulation characteristics of buildings improve, which makes it even harder for radio waves to enter, and the increase in carrier frequencies used for cell transmission result- ing in lower inherent abilities for radio wave penetration. With 5G networks deploying higher frequencies than any previous generations of networks (2G, 3G, and 4G all focused on sub-6 GHz, whereas 5G additionally introduces mmWave), this makes indoor coverage an increasingly pressing deployment problem to solve with small cells. The market driver for indoor coverage is also related to the outdoor small cell market driver, in that the majority of mobile users generate most of their data while stationary and indoors. Today, this is frequently offloaded to a Wi-Fi network, but as 