###### tags: `open5gs` `openairinterface` `RIC` `E2`

:::info
- **Location:** RT LAB
- **Date:** March 4, 2025
- **Author:** Saffana Zyan DINI
- **Contact:** Zyzy <[e-mail]>
- **Reference:**
- [End to End test open5gs and Openairinterface CU/DU split](https://hackmd.io/@HMiZWWkbRWe7Lksri7E63g/SyaWXi3ZJe)
- [OAI FlexRIC source code](https://gitlab.eurecom.fr/mosaic5g/flexric)
- https://gitlab.eurecom.fr/oai/openairinterface5g/-/blob/develop/openair2/E2AP/README.md#212-build-oai-with-e2-agent

:::
## General Source Code, Version and Config
1. Open5GS (optional for testing flexric)
- version: v2.7.2-76-gce36143f5
- VM OS : Ubuntu 22.04.6
- IP : 192.168.60.2
- ogstun : 10.45.0.1
1. Openairinterface
- version: 2025.w04-9-g94c75bee8f
- VM OS : Ubuntu 22.04.6
## Architecture

## Call Flow

## Installation Guide
### Clone and Build OAI with e2 interface

sudo git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git <directory name>
e.g. sudo git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git zy-OAI
cd cmake_targets
./build_oai -I -w SIMU --gNB --nrUE --build-e2 --ninja


check this directory to make sure build e2 and clone flexric sucsess

    ls zy-OAI/openair2/E2AP/flexric/

### Flexric Prerequisites
* A recent CMake (at least v3.22). specify for ubuntu 22.04, check https://apt.kitware.com/ for other version

    sudo apt-get update
    sudo apt-get install ca-certificates gpg wget

    test -f /usr/share/doc/kitware-archive-keyring/copyright ||
    wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/null | gpg --dearmor - | sudo tee /usr/share/keyrings/kitware-archive-keyring.gpg >/dev/null

    echo 'deb [signed-by=/usr/share/keyrings/kitware-archive-keyring.gpg] https://apt.kitware.com/ubuntu/ jammy main' | sudo tee /etc/apt/sources.list.d/kitware.list >/dev/null
    sudo apt-get update

    test -f /usr/share/doc/kitware-archive-keyring/copyright ||
    sudo rm /usr/share/keyrings/kitware-archive-keyring.gpg

    sudo apt-get install kitware-archive-keyring

    echo 'deb [signed-by=/usr/share/keyrings/kitware-archive-keyring.gpg] https://apt.kitware.com/ubuntu/ jammy-rc main' | sudo tee -a /etc/apt/sources.list.d/kitware.list >/dev/null
    sudo apt-get update

    sudo apt-get install cmake

* SWIG (at least v.4.1). in some case you also need to install library of pcre2 you can install by:

    sudo apt update
    sudo apt install libpcre2-dev
    sudo add-apt-repository ppa:deadsnakes/ppa -y
    sudo apt install python3.8 python3.8-dev
    python3.8 --version

then install SWIG

    sudo git clone https://github.com/swig/swig.git
    cd swig
    sudo git checkout release-4.1
    sudo ./autogen.sh
    sudo ./configure --prefix=/usr/
    sudo make -j8
    sudo make install


* GCC (gcc-10, gcc-12, or gcc-13)
gcc-11 is not currently supported. the default gcc version of ubuntu 22.04 is gcc-11. upgrade or downgrade the version by:

    sudo apt install -y gcc-10 g++-10
    sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 100
    sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-10 100

* install other dependancies

    sudo apt install libsctp-dev cmake-curses-gui python3-dev

* open directory checkout version for flexric

    cd zy-OAI/openair2/E2AP/flexric/
    sudo git checkout f1c08ed2b9b1eceeda7941dd7bf435db0168dd56

> git checkout v1.0.0 is only support in flexric emulation test not support in oai cu/du/gnb test.
* Build Flexric

    sudo mkdir build
    cd build 
    sudo cmake .. 
    sudo make -j8

* Install Flexric

    sudo make install


By default the service model libraries will be installed in the path /usr/local/lib/flexric while the configuration file in /usr/local/etc/flexric.
* check this 2 folder, to make sure installation success

    ls /usr/local/lib/flexric
    ls /usr/local/etc/flexric

> if you want to rebuild flexric installation you need to remove both previous folder.
* Check that everything went fine running the tests:

    sudo ctest -j8 --output-on-failure


## Usage/deployment

### Test with emulators

* Start the nearRT-RIC

    ./examples/ric/nearRT-RIC


* Start E2 Node agents

gNB-mono

    ./examples/emulator/agent/emu_agent_gnb

if CU/DU split is used, start the gNB as follows

    ./examples/emulator/agent/emu_agent_gnb_cu
    ./examples/emulator/agent/emu_agent_gnb_du


**Additionally**, feel free to customize your own config files. Here is one example:

./examples/emulator/agent/emu_agent_gnb_cu -c ~/flexric1.conf &
./examples/emulator/agent/emu_agent_gnb_du -c ~/flexric2.conf &

where, flexric1.conf is:

[NEAR-RIC]
NEAR_RIC_IP = 127.0.0.1
[XAPP]
DB_PATH = /tmp/
DB_NAME = xapp_db1

flexric2.conf is:

[NEAR-RIC]
NEAR_RIC_IP = 127.0.0.1
[XAPP]
DB_PATH = /tmp/
DB_NAME = xapp_db2

>It is also interesting to mention, multiple xApps can be run in parallel.
At this point, FlexRIC is working correctly in your computer and you have already tested the multi-agent, multi-xApp and multi-language capabilities.
The latency that you observe in your monitor xApp is the latency from the E2 Agent to the nearRT-RIC and xApp. In modern computers the latency should be less than 200 microseconds or 50x faster than the O-RAN specified minimum nearRT-RIC latency i.e., (10 ms - 1 sec) range.
Therefore, FlexRIC is well suited for use cases with ultra low-latency requirements.
Additionally, all the data received in the xApp is also written to `/tmp/xapp_db` in case that offline data processing is wanted (e.g., Machine
Learning/Artificial Intelligence applications). You browse the data using e.g., sqlitebrowser.

## Result
:dart: xapp helloworld test result
---

./examples/xApp/c/helloworld/xapp_hw

### Test with OAI
Edit CU

cd cmake_targets/ran_build/build/
sudo nano ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/cu_gnb.conf

add e2 agent in CU

e2_agent = {
  near_ric_ip_addr = "RIC IP"; # same as /usr/local/etc/flexric/flexric.conf
  sm_dir = "/usr/local/lib/flexric/"
}

Edit DU

cd cmake_targets/ran_build/build/
sudo nano ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/du_gnb.conf

add e2 agent in DU

e2_agent = {
  near_ric_ip_addr = "RIC IP"; # same as /usr/local/etc/flexric/flexric.conf
  sm_dir = "/usr/local/lib/flexric/"
}

* Start the nearRT-RIC

    ./examples/ric/nearRT-RIC


* Start the CU

    sudo ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/cu_gnb.conf --sa --rfsim


* Start the DU

    sudo ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/du_gnb.conf --sa --rfsim -E

see in log that E2 is active then test with **Start different xApps**
* Start different xApps

start the KPM monitor xApp - measurements stated in 2.1.1 E2SM-KPM

    ./examples/xApp/c/monitor/xapp_kpm_moni


start the RC monitor xApp - aperiodic subscription for "UE RRC State Change"

    ./examples/xApp/c/monitor/xapp_rc_moni


start the RC control xApp - RAN control function "QoS flow mapping configuration" (e.g. creating a new DRB)

./examples/xApp/c/kpm_rc/xapp_kpm_rc


start the (MAC + RLC + PDCP + GTP) monitor xApp

./examples/xApp/c/monitor/xapp_gtp_mac_rlc_pdcp_moni


>Please, notice that no real UE is connected. Therefore, random values within supported messages are filled.
Before starting the nearRT-RIC, check that the IP address where your nearRT-RIC will be listening is the desired one at `/usr/local/etc/flexric/flexric.conf`.
Infact the default configuration assumes all the components are located in the same localhost.

==Importance==