t Switch 100G Ethernet Switch 25-50GbE 25-50GbE 25-50GbE 25-50GbE 25-50GbE 25-50GbE Offload / Accelerator Offload / Accelerator Offload / Accelerator Offload / Accelerator Offload / Accelerator Offload / Accelerator CU-UP CU-UP CU-UP CU-UP CU-UP CU-UP IPSec IPSec IPSec PDCP-UP PDCP-UP PDCP-UP FIGURE 4-6 Scale-out to multiple blades. 2x100GbE 100GbE Ethernet Backplane 100G Ethernet Switch 25-50GbE 25-50GbE L1 Accelerator L1 Accelerator FIGURE 4-7 DU acceleration blade. 148 Open Radio Access Network (O-RAN) Systems Architecture and Design Server-based solutions Server-based systems use a standard edge server architecture (typically x86 Instruction Set Architecture (ISA) based) to provide the necessary compute to implement the DU proces- sing. The obvious advantage of this approach is that there is a ready market of available server platforms in a variety of form factors, price, and performance points. Given that "white box" servers can be assembled and sold with or without branding, profit margins are typi- cally low and competition fierce. Hardware is readily made and does not need to be designed from scratch. This saves development time and allows the vendor to ride "Moore's law" by upgrading to new hardware as soon as it's made available. Standard (Linux) software packages are also available, removing the need to develop a BSP software platform that is unique to the DU product. We will not discuss the intricacies of white box server platforms here as there are plenty of reading materials on the topic. However, to make a white box server into a DU product, there are a few challenges to be solved (Fig. 4-8): Time/frequency synchronization Fronthaul and backhaul IO Forward error correction and other acceleration. In a little more detail: Time/frequency synchronization. Given that standard white box servers do not provision for IEEE1588 or Global Positioning System (GPS) timing, this component is typically provided by an external unit. The external unit can either be a PCIe based plug-in board that incorporates a GP