ORAN: Introduction of M-plane (Management Plane)

The Management Plane (M-Plane) in O-RAN is responsible for managing the Radio Unit (O-RU). It provides a variety of functions to set parameters on the O-RU side, as required by the Control/User Plane (C/U-Plane) and Synchronization Plane (S-Plane). For example, the M-Plane can be used to:

• Manage O-RU software.
• Perform fault management.
• Configure O-RU parameters.
• Monitor O-RU performance.

The M-Plane is an important part of O-RAN because it enables a real multi-vendor Open RAN. This is because the M-Plane provides a standard interface for managing O-RUs from different vendors. This eliminates the need for operators to learn and use different management interfaces for each vendor’s O-RU.

The Open Fronthaul M-plane interface supports following FCAP functions

Ø Start-up” installation

Ø SW management

Ø Configuration management

Ø Performance management

Ø Fault Management

Ø File Management Log and Trace Management

Here is a different way to explain the M-Plane in O-RAN:

Imagine that the O-RAN network is a car. The C/U-Plane is the driver, the S-Plane is the engine, and the M-Plane is the mechanic. The driver tells the car where to go, the engine makes the car move, and the mechanic keeps the car running smoothly.

In the same way, the C/U-Plane tells the O-RAN network what to do, the S-Plane keeps the network synchronized, and the M-Plane manages the O-RUs.

• The M-Plane supports a hierarchical/hybrid model, which means that it can be used to manage O-RUs that are directly connected to the O-DU, as well as O-RUs that are connected to the O-DU through a fronthaul transport network.
• The M-Plane also supports IP and delay management for the C/U Plane. This means that it can be used to configure the IP addresses and delay budgets for the C/U Plane traffic.
• Finally, the M-Plane supports FCAPS (Fault, Configuration, Accounting, Performance, and Security) functions, including sync configuration and status. This means that it can be used to manage the faults, configuration, accounting, performance, and security of the O-RUs.

Overall, the M-Plane is a critical component of O-RAN. It enables a real multi-vendor Open RAN by providing a standard interface for managing O-RUs from different vendors. It also supports a hierarchical/hybrid model, IP and delay management for the C/U Plane, and FCAPS functions.

M-Plane architecture model

Hierarchical model. As shown in Figure, the O-RU is managed entirely by one or more O-DU(s) using a NETCONF based M-Plane interface. When the O-RU is managed by multiple O-DUs, it is typically for enabling O-DU and/or transport connectivity redundancy capabilities

Hybrid model. As shown in Figure , the hybrid architecture enables one or more direct logical interface(s) between management system(s) and O-RU in addition to a logical interface between O-DU and the O-RU. It should be noted that the NETCONF clients connecting to the O-RU may be of different classes (e.g. O-DU and NMS). For example, functions like O-RU software management, performance management, configuration management and fault management can be managed directly by the management system(s).

The M-Plane supports a single protocol stack:

• NETCONF over Ethernet with IP transported using TCP with SSH: This protocol stack is based on the NETCONF standard, which is used to manage network devices.
• SSH is used to encrypt the traffic between the O-DU and O-RU.