Robert Schmidt
7227cfb320
N2 handover
This MR introduces full support for N2 handover, covering handover
decision, preparation, execution, and notification between source and
target NG-RAN nodes.
Key features:
1. Handover Decision & Preparation:
- Implement N2 handover decision based on UE measurement reports.
- Generate the Handover Preparation Information message, including
RRCReconfiguration.
- Send Handover Required message from the source NG-RAN to the AMF.
2. Handover Execution:
- Decode and handle the Handover Request on the target NG-RAN.
- Process the Handover Command on the source gNB, triggering
RRCReconfiguration.
- Initiate Handover Notify after successful completion.
3 NGAP & RRC Enhancements:
- Implement NGAP encoding/decoding functions for Handover Required,
Handover Request, Handover Command, Handover Failure, and Handover
Notify (3GPP TS 38.413).
- Adds NG-RAN Status Transfer support (UL/DL) for PDCP COUNT
preservation during mobility:
- support for NGAP Uplink and Downlink RAN Status Transfer messages
(TS 38.413 §9.2.3.13-14) to enable proper PDCP COUNT value
transfer during handover or recovery: NGAP encoding/decoding for
RAN Status Transfer, PDCP helpers to extract and apply COUNT (HFN
+ SN) per DRB. This aligns with TS 38.300 §9.2.3.2.1 and TS 23.502
§4.9.1.3.3, ensuring PDCP status preservation in AM.
4. Testing:
- Introduce a Telnet command to manually trigger N2 handover using UE
ID and neighbor PCI.
- Add configuration file for testing N2 handover with a target gNB.
This document outlines how to use the OAI CI framework and gives a quickstart.
[[TOC]]
Quickstart
There is a script main.py that
- reads scenario files from XML
- executes the steps (e.g., deployment of CN/gNB/UE, attach, ping, ...)
To simplify, a script run_locally.sh can be used to run a single scenario
locally. First, download images for gNB&UE (we assume you already downloaded
the CN) and tag them "latest", which is expected by run_locally.sh:
docker pull oaisoftwarealliance/oai-gnb:develop
docker tag oaisoftwarealliance/oai-gnb:develop oai-gnb
docker pull oaisoftwarealliance/oai-nr-ue:develop
docker tag oaisoftwarealliance/oai-nr-ue:develop oai-nr-ue
Now, run the scenario:
cd ~/openairinterface5g/ci-scripts/
./run_locally.sh xml_files/container_5g_rfsim_simple.xml
Output should look like
[2025-08-07 18:07:49,631] INFO: ----------------------------------------
[2025-08-07 18:07:49,631] INFO: Creating HTML header
[2025-08-07 18:07:49,631] INFO: ----------------------------------------
[2025-08-07 18:07:49,766] INFO: ----------------------------------------
[2025-08-07 18:07:49,767] INFO: Starting Scenario: xml_files/container_5g_rfsim_simple.xml
[2025-08-07 18:07:49,767] INFO: ----------------------------------------
[2025-08-07 18:07:49,767] INFO: placing all artifacts for this run in /home/richie/oai/cmake_targets/log/container_5g_rfsim_simple.xml.d/
[...]
[2025-08-07 18:07:49,771] INFO: ----------------------------------------
[2025-08-07 18:07:49,771] INFO: Test ID: 1 (#1)
[2025-08-07 18:07:49,771] INFO: Deploy OAI 5G CoreNetwork
[2025-08-07 18:07:49,771] INFO: ----------------------------------------
it will run an end-to-end test, connecting one UE to the gNB, and ping, before
undeploying. As shown, logs will be under
/home/richie/oai/cmake_targets/log/container_5g_rfsim_simple.xml.d/. The
python code also produces an HTML report in ci-scripts/test_results.html.
Running with local changes
In order to run the tests as above, with local changes, please build images locally.
It is not yet possible to override an existing image with changes made locally to a source file and run it directly through the CI framework. However, it is possible to override an existing image with local changes, and run the scenario manually following the console logs steps provided above. This is described in the 5G RFsimulator README.