ry similar to the eCPRI piece of the DU solution and often there is re- use between the DU and the RU, if both are implemented by the same vendor. This saves development time and increases chances of successful (internal) interoperability, after all. eCPRI termination in the RU is implemented (as for the DU) as one of: Software implementations on a GPP-typically used in the low- to mid-end Radio Unit Centralized Repeated per Function Antenna Centralized Processor Unit DFE/RFIC RF Sub- To/From Fronthaul eCPRI Beam- System Terminate Forming Antenna Array 1588/ SyncE Time/ Frequency FIGURE 4-16 Key components in the integrated radio unit. 158 Open Radio Access Network (O-RAN) Systems Architecture and Design FPGA based designs Optimized ASIC IP, either implemented in a separate device or as part of a custom SoC. eCPRI termination may optionally push the (de-)compression component to the low- Physical Layer (PHY) processing element, if this element is physically on a different device. This way, the eCPRI termination complexity is reduced, and IO bandwidth between this component and the low Physical layer processor is reduced. Low physical layer and digital front end Low Physical Layer and Digital Front End (DFE) functions can be implemented in a central- ized or distributed manner, depending on the system scaling requirements. We show a few implementation options here: The Software Defined Approach (Fig. 4-17) uses a general-purpose Networking Processor or alternatively, an FPGA that integrates control plane Arm CPU cores for termination of the eCPRI traffic. The eCPRI buffers are transferred over PCIe to a secondary device that implements the Lower Physical Layer processing for all associated antenna paths, including beamforming and (relevant) DFE components. More about the DFE RF Subsystem splits is covered later. As the antenna count goes up, the Low Physical Layer/DFE functionality doesn't fit into a single device anymore. At this point, we need a scale-out scenario where the beamforming component (which is a natu