Raise E2 Event

[LVancina]

Greetings,

I am doing some experimentation with xApps, using the flexRIC framework, and I am trying to figure out how I can notify my xApp every time an initial UE message is received by srsRAN (i.e. handle_initial_ue_message() is invoked). Could anyone point me at an example that might be helpful? Thanks!

[pgawlowicz]

Hi, currently it is not supported by our current E2 agent implementation. Also, I do not think it is supported on the FlexRIC side.

[LVancina]

That is very interesting. It sounds like you are saying that a SDL has not been implemented for srsRAN yet and it is unclear from the ORAN technical specification how one might go about doing that. Am I understanding correctly?

Also, just from studying the code (which I don't fully understand yet), I am inferring that, in order to make certain data accessible to an xApp, I will first have to create an E2SM module and add it as an E2SM service. Is that an accurate assessment? It's starting to look like a laborious process to implement an xApp that requires more data than basic KMPs. Any recommendations?

[pgawlowicz]

I believe that SDL is part of RIC platform, so it does not need to be implemented on the srsRAN side.
It is unclear, how SDL and UE-NIB should be filled. In O-RAN.WG3.RICARCH-R003-v05.00.docx, you can find two use-cases related to getting information about the connected E2 nodes, but nothing about the connected UEs. Specifically:

• 9.5.8.1 Subscribe/Notify for E2NodeInfo and E2NodeList
• 9.5.8.2 Subscribe/Push for E2NodeInfo and E2NodeList

and those two structures are:

• E2NodeList: List of known E2 Node ID and the associated E2 Node State
• E2NodeInfo: E2 Node component configuration list and RAN function list

Regarding the second question, I am not sure if you are talking about the implementation of E2 agent or xApps.
If you are interested, you can check our simplified ORAN-SC-RIC version, where we provide two KPM xApps, that work perfectly with our E2 Agent.
You can access it here:
https://github.com/srsran/oran-sc-ric/

[LVancina]

@pgawlowicz Yes, I forgot that the SDL is a RIC component, not part of the RAN. I have not been able to verify that FlexRIC has implemented a SDL, which may be a major problem for my project.

In the mean time, I am just trying to figure out how information and control messages are sent to / received from the E2 agent(s) in srsRAN as well as how I can start implementing a custom E2 service model. If you or anyone else can point me in the right direction on that, then I would be very grateful.

[pgawlowicz]

You can find the E2 code here:

• https://github.com/srsran/srsRAN_Project/tree/main/include/srsran/e2
• https://github.com/srsran/srsRAN_Project/tree/main/lib/e2

Probably, you can have a closer look at KPM and RC modules:

• https://github.com/srsran/srsRAN_Project/blob/main/lib/e2/e2sm/e2sm_kpm/e2sm_kpm_impl.cpp
• https://github.com/srsran/srsRAN_Project/blob/main/lib/e2/e2sm/e2sm_rc/e2sm_rc_impl.cpp

[pgawlowicz]

I would recommend putting intended your functionality into one of the existing modules (KPM or RC).