Open RAN |
||||||||||||||||||||||||||||||||||||||
E2AP
The interface that is designed for communication between DU/CU and Near-Real Time RIC is called E2. The protocol for the communication over E2 interface is called E2AP. This kind of naming conventions is similar to 3GPP naming convention (e.g, NGAP as Protocol for NG interface, X2AP as Protocol for X2 interface, S1AP as Protocol for S1 interface etc). The algorithms happening inside of RIC would be up to each individual implmentation and out of the scope of this note, but E2AP (protocol and message structure) should be same for every RIC and CU/DU.
The types of Messages (signaling messages) running over E2 interface is defined in O-RAN specification as follows.
< O-RAN.WG3.E2SM-KPM - Table 5-1: Relationship between E2SM services and E2AP Information elements >
As you notice from the table above, the elemenary E2AP procedure can be grouped into only a few types : SUBSCRIPTION, INDICATION, CONTROL, UPDATE. The overall procedure of these types can be illustrated as follows (NOTE : The diagram on the left column is from The O-RAN SC RIC). As you would notice here, almost all the procedure except CONTROL procedure is initiated by SUBSCRIPTION. Another common thing to be noticed is that most of the procedure (except CONTROL) is initiated (Requested) by RIC and RAN is supposed to do some action (e.g, Report, Perform Policy, Insert) as per requested by RIC.
Reference
|
||||||||||||||||||||||||||||||||||||||