Key Interfaces in Open RAN

A1 Interface

Open Fronthaul T

F1 Interface

O1 Interface

Key Interfaces in Open RAN

E1 Interface

O2 Interface

X2 / Xn Interfaces

E2 Interface

NG Interfaces:

E2 Interface

• Connects the Near-Real-Time RIC to the CU and DU
• The RIC helps improve performance using smart apps (xApps)

F1 Interface

• Connects the O-DU to the Central Unit (O-CU) with two parts: F1-u (User Plane) – sends user data F1-c (Control Plane) – sends control signals

X2 / Xn Interfaces

• Help base stations talk to each other
• Used in LTE (X2) and 5G (Xn)
• It is also split into two: User data (X2-u/Xn-u), Control info (X2-c/Xn-c)

A1 Interface

• Connects the Non-Real-Time RIC to the Near-RT RIC
• Sends AI-based policies and guidance to help the network adapt

O2 Interface

• Connects the SMO to the cloud system (O-Cloud) that runs Open RAN software Helps manage the cloud setup

E1 Interface

• Connects the two parts of the Central Unit: O-CU-UP (User Plane) O-CU-CP (Control Plane)
• These two parts work separately

Open Fronthaul

• Connects the Radio Unit (O-RU) to the Distributed Unit (O-DU)
• Carries: user data, control info, and timing signals
• Often based on a tech called eCPRI

NG Interfaces:

• Connect the Central Unit (O-CU) to the 5G Core Network
• There are two types: NG-u for user data, NG-c for control messages

O1 Interface

• Connects the Service Management and Orchestration (SMO) system to RAN parts like the RU, DU, CU, and RIC
• Handles: faults, setup, performance, and security