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R11 SON Use Case Architecture Review Document: View file
Prior to R10 release, the SON use case had control loop flows for PCI and ANR configuration changes based on O-RAN O1 interface (netconf interface from O-RAN SMO to the O-CU/O-DU). Control loop messages are forwarded from Policy to SDN-R. As shown in Figure 1, the netconf client in SDN-R communicates with netconf servers in the RAN-Sim RAN simulator which has abstracted functionality representing O-DU/O-CU in the RAN.
Figure 1: SON Use Case flow for O1-based control loop actions in ONAP Rel 3 to Rel 10
A major feature of the R11 release is to include support for the O-RAN A1 interface, and start with an extensible and flexible approach.
In this release, there are two control loop flows: one each for control loop actions based on:
- O1 control loop flow. This flow is for O-RAN O1-based actions. Control loop messages from the SON Handler Microservice are forwarded to Policy, and then forwarded to the O1 (netconf) interface in SDN-R. This is largely similar to the flow in the previous releases, with SDN-R netconf client interacting with the netconf servers in RAN-Sim representing the O1 termination in the abstracted O-CU/O-DU.
- A1 control loop flow: This flow is for A1-based actions, and is new for R11 release. Control loop messages from the SON Handler Microservice are forwarded to Policy, and then forwarded to the A1 Policy Management Service in SDN-R. This leverages existing work in ONAP and OSC for the A1 interface, specifically the A1 Policy Management Service (PMS) in SDN-R/Non-RT RIC, and A1 Simulator for a simulated/abstracted A1 Termination in the O-RAN Non-RT RIC (see links below).
Links to existing work related to A1 interface:
O-RAN A1 Policies in ONAP
R9 A1 Policy Function Extensions
R8 A1 Adapter and Policy Management Extension
OSC A1 Simulator: https://docs.o-ran-sc.org/projects/o-ran-sc-sim-a1-interface/en/latest/
As shown in Figure 2, there are operational policies in the Policy module which forward the control loop messages to SDN-R/O1 and SDN-R/A1-PMS.
There are new modules in the RAN-Sim RAN Simulator to terminate the A1 messages, along with a new ran-app modules representing an abstraction of an xApp hosted in the Near-RT RIC which interacts with the O-CU/O-DU in the RAN. For more details of the enhancements to RAN-Sim for A1 Support, please see R11 Ran-Sim .
Figure 2: SON Use Case flow for O1-based and A1-based control loop actions actions in ONAP Rel 11