# IVC 5G O-RAN Summary

###### tags: `UNILA`

## Summary 28th of July 2021
# "O-DU and O-CU"

1. O-CU
CU: The centralized unit software that runs the Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) layers. The gNB consists of a CU and one DU connected to the CU via Fs-C and Fs-U interfaces for CP and UP respectively. A CU with multiple DUs will support multiple gNBs. The split architecture lets a 5G network utilize different distributions of protocol stacks between CU and DUs depending on midhaul availability and network design


Multi-RAT CU => 4G, 5G, and other protocol processing
DU and RUU
- real-time L2 Functions
- Baseband processing
- radio frequency processing

O-CU Related Components


O-CU APIs
• RRC-SDAP
• RRC-PDCP
• SDAP-PDCP

2. O-DU
DU: The distributed unit software that is deployed on site on a COTS server. DU software is normally deployed close to the RU on site and it runs the RLC, MAC, and parts of the PHY layer. This logical node includes a subset of the eNodeB (eNB)/gNodeB (gNB) functions, depending on the functional split option, and its operation is controlled by the CU.


O-DU Internal Interfaces


L1/L2 Interface, 5G FAPI specifications by Small Cell Forum
- P5: PHY configuration interface
- P7: Main data path interface
- P19: RF control interface (O-DU will use an adaptation module at Frontend to handle P19 interface)

L2 Interfaces
- O-DU-OAM-Agent_MAC Interface
- RLC-MAC Interface
- MAC-Scheduler Interface