O-RAN Central Unit and Distributed

Unit

Last Updated: Jan 5, 2022

5G standards allow for deployment options with a ﬂexible, functional split between networking

elements. This allows for implementations that are cloud/centralization centric.

O-RAN standards deﬁne the central unit as the entity responsible for Transport/S1, PDCP and

RRC/Control plane processing in an option 2 split conﬁguration. Deployment options range

widely from low-end in-building processing with ≤25-50Gbps capacity to scale-out scenarios

supporting multiple Tbps aggregate processing.

The distributed unit is responsible for MAC/RLC and High-PHY processing, implemented as C

code on general-purpose (eg Arm) devices. Cost and power are minimized by using optimized

(Arm NEON) SIMD kernels and a look-aside accelerator device for forward error correction and

DSP processing acceleration.

O-RAN Block Diagram

NX P T echnology

Non NX P T echnology

Optional T echnology

Accelerator

Device

Multicore Arm Processor

T o RU

T o CU

PCIe

10 / 25 GbE