O-DU Low Project Introduction

The O-DU low project focus on the baseband PHY Reference Design, which uses Xeon® series Processor with Intel Architecture. This 5GNR Reference PHY consists of a L1 binary and three kinds of interfaces which are validated on a Intel® Xeon® SkyLake / CascadeLake platforms and demonstrates the capabilities of the software running different 5GNR L1 features. It implements the relevant functions described in [3GPP TS 38.211, 212, 213, 214 and 215].

The L1 has three interfaces to communicate with other network functions as described below:

• Interface between L1 and Front Haul, it adopts the WG4 specification for the CUS plane communication.

• Interface between O-DU Low and O-DU High, it adopts the FAPI interface according to the WG8 AAL specification.

• Interface between O-DU Low and accelerator, DPDK BBDev was adopted as original contribution, it will follow the WG6 definition after the WG6 specification is finalized.

The following figure shows the ORAN O-CU, O-DU and O-RU blocks for a gNB implemetation. The O-DU Low projects implements the FAPI interface by a 5G FAPI TM module, the OFH-U and OFH-C by means of the FHI Library and the functionality of the High-PHY and a test MAC are available through github in the form of a binary blob for the current release. For the details refer to the Running L1 and Testmac section of this document

Scope

In this O-DU Low document, the details on how the build the modules supporting each interface, how to run the L1 and associated components, the architecture for each interface implementation and the release notes that describe each component release details are provided.

Intended Audience

The intended audience for this document are software engineers and system architects who design and develop
5G systems using the O-RAN Specifications.

Terminology

Table 1. Terminology

Term	Description
5G NR	Fifth Generation New Radio
ACS	Access Control system
API	Application Programming Interface
BOM	Bill of Materials
CP	Cyclic Prefix
DDP	Dynamic Device Personalization
DPDK	Data Plane Development Kit
eAxC	Extended Antenna Carrier
eCPRI	Enhanced Common Public Radio Interface
eNB	Enode B
ETH	Ethernet
FCS	Frame Check Sequence
FEC	Forward Error Correction
FFT	Fast Fourier Transform
FH	Front Haul
gNB	Next-generation NodeB also named as Base Station
GNSS	Global Navigation Satellite System
GPS	Global Positioning System
HARQ	Hybrid Automatic Repeat Request
HW	Hardware
IFG	Interframe Gap
IFFT	Inverse Fast Fourier Transform
IoT	Inter-Operability Testing
IQ	In-band and Quadrature
LAA	License Assisted Access
LTE	Long Term Evolution
MAC	Media Access Control
MEC	Mobile Edge Computing
M-Plane	Management Plane
mmWave	Millimeter Wave
NIC	Network Interface Controller
O-DU	O-RAN Distributed Unit: a logical node hosting RLC/MAC/High-PHY layers based on a lower layer functional split.
O-RU	O-RAN Radio Unit: a logical node hosting Low-PHY layer and RF processing based on a lower layer functional split. This is similar to 3GPP’s “TRP” or “RRH” but more specific in including the Low-PHY layer (FFT/IFFT, PRACH extraction).
OWD	One Way Delay
PDCCH	Physical Downlink Control Channel
PDSCH	Physical Downlink Shared Channel
PHC	Physical Hardware Clock
PHP	Hypetext Preprocessor
PMD	Poll Mode Driver
POSIX	Portable Operating System Interface
PRACH	Physical Random Access Channel
PRB	Physical Resource Block
PRTC	Protected Real Time Clock
PUCCH	Physical Uplink Control Channel
PUSCH	Physical Uplink Shared Channel
PTP	Precision Time Protocol
RA	Random Access
RAN	Radio Access Network
RB	Resource Block
RE	Resource Element
RLC	Radio Link Control
RoE	Radio over Ethernet
RT	Real Time
RTE	Real Time Environment
RSS	Receive Side Scaling
RU	Radio Unit
SR-IOV	Single Root Input/Output Virtualization
SW	Software
SyncE	Synchronous Ethernet
TDD	Time Division Duplex
ToS	Top of the Second
TSC	Time Stamp Counter
TTI	Transmission Time Interval
UE	User Equipment
UL	Uplink
VF	Virtual Function
VIM	Virtual Infrastructure Manager
VLAN	Virtual Local Area Network
VM	Virtual Machine
WLS	Wireless Subsystem Interface
xRAN	Extensible Radio Access Network

Reference Documents

Table 2. Reference Documents

Document	Document No./Location
FlexRAN Reference Solution Software Release Notes	575822
FlexRAN Reference Solution L1 XML Configuration User Guide	571741
FlexRAN Reference Solution LTE eNB L2-L1 Application Programming Interface [API] Specification	571742
FlexRAN Reference Solution L2-L1 nFAPI Specification	576423
FlexRAN and Mobile Edge Compute(MEC) Platform Setup Guide	575891
FlexRAN 5G NR Reference Solution RefPHY (Doxygen).	603577
Intel® Ethernet Controller E810 Dynamic Device Personalization (DDP) Technology Guide	617015
3GPP* specification series	https://www.3gpp.org/specifications
Wolf Pass Server Documentation
Intel® C++ Compiler in Intel® Parallel Studio XE
DPDK documentation	https://core.dpdk.org/doc/
O-RAN Fronthaul Working Group Control, User and Synchronization Plane Specification (ORAN-WG4.CUS.0-v04.00)	https://www.o-ran.org/specifications
ORAN Specifications	https://www.o-ran.org/specifications
IEEE-1588-2008 IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems	https://standards.ieee.org/ standard/1588-2008.html
eCPRI Specification V2.0 Interface Specification	https://www.networkdatapedia.com// post/2019/10/05/capturing-/ packets-through-ecpri-v20/ -which-enables-5g