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Deploying OAI-RAN RF Simulator Against free5GC

Note

Author: Chieh Cheng Kuo, Kuan Lin Chen
Date: 2026/06/22

In this demo we will practice:

  • Installing OAI-RAN
  • Configuring OAI-RAN
  • Running OAI-RAN against free5GC

Topology:
topo

Tip

Based on our testing, OAI-RAN requires Ubuntu 22.04 or later, and the VM needs support AVX.

1. Install OAI-RAN VM

Repeat the steps of cloning free5gc VM from the base VM, create a new VM for the OAN-RAN simulator:

  • Name the VM oai-ran, and create new MAC addresses for all network cards.
  • Make sure the VM has internet access and can log in using SSH.
  • Change the hostname to oai-ran.
  • Make the Host-only network interface have static IP address 192.168.56.102.
  • Reboot the oaitan VM, as well as the free5gc VM.
  • You can ping 192.168.56.101 from the oairan VM, and also ping 192.168.56.102 from the free5gc VM.

2. Install OAI-RAN

Take a look at oai-ran website for more information about it. You can check out its official deployment guide or follow the steps below.

Update and upgrade OAI-RAN VM first:

sudo apt update
sudo apt upgrade

Install required tools:

sudo apt install -y \
  autoconf automake ninja-build build-essential cmake g++ git \
  libboost-all-dev libncurses-dev \
  python3-dev python3-mako python3-numpy \
  python3-requests python3-scipy \
  python3-setuptools python3-ruamel.yaml \
  libcap-dev libblas-dev liblapacke-dev

Download and build OAI-RAN:

cd ~
git clone https://github.com/openairinterface/openairinterface5g.git
cd openairinterface5g
git checkout develop

# Install OAI dependencies
cd cmake_targets
./build_oai -I

# Build OAI-RAN:
./build_oai --ninja --nrUE --gNB

3. Install free5GC WebConsole

free5GC provides a simple web tool WebConsole to help creating and managing UE registrations to be used by various 5G network functions (NF).

If WebConsole isn't installed yet, please, SSH into free5gc's VM (192.168.56.101) and follow the instructions contained on this section here.

4. Use WebConsole to Add an UE

First start up the WebConsole server:

cd ~/free5gc/webconsole
./bin/webconsole

The screen shows the port number :5000 at the end. Open your web browser from your host machine, and enter the URL http://192.168.56.101:5000

  • On the login page, enter username admin and password free5gc.
  • Once logged in, widen the page until you see “Subscribers” on the left-hand side column.
  • Click on the Subscribers tab and then on the New Subscriber button
  • Once the data shows up on the "Subscribers" table, you can press Ctrl-C on the terminal to kill the WebConsole process on the free5gc VM
  • You can view more tutorials through this link.

Note

You have to make sure that the parameters on the webconsole are consistent with the UE.

5. Setting OAI-RAN

In the oai-ran VM, there are two files need to be changed：

  • ~/openairinterface5g/targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf
  • ~/openairinterface5g/targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf

First SSH into oairan, and edit the file ~/openairinterface5g/targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf.

The gNB must be configured with the correct PLMN and slice information so that it matches the core network settings, and it must also use the correct IP addresses for the N2 and N3 interfaces so it can communicate with the AMF and UPF properly, in this example we use default ue information:

(a) Update plmn_list in the gNBs entry
    plmn_list = ({ mcc = 208; mnc = 93; mnc_length = 2; snssaiList = ({ sst = 0x01; sd = 0x010203; }) });
(b) Set amf_ip_address to the AMF's N2 interface IP address
    ////////// AMF parameters:
    amf_ip_address = ({ ipv4 = "192.168.56.101"; });
(c) Set the gNB's N2 and N3 interface IP addresses in NETWORK_INTERFACES

    NETWORK_INTERFACES :
    {
        GNB_IPV4_ADDRESS_FOR_NG_AMF              = "192.168.56.102";
        GNB_IPV4_ADDRESS_FOR_NGU                 = "192.168.56.102";
        GNB_PORT_FOR_S1U                         = 2152; # Spec 2152
    };

Next, the UE configuration, edit uicc0 in ~/openairinterface5g/targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf`:
uicc0 = {
  imsi = "208930000000001";
  key = "8baf473f2f8fd09487cccbd7097c6862";
  opc= "8e27b6af0e692e750f32667a3b14605d";
  pdu_sessions = ({ dnn = "internet"; nssai_sst = 0x01; nssai_sd = 0x010203; });
}

The data appear to be the same as what we set in WebConsole.

6. Testing OAI-RAN against free5GC

A. Start free5GC

SSH into free5gc. If you have rebooted free5gc, remember to run:

sudo sysctl -w net.ipv4.ip_forward=1
sudo iptables -t nat -A POSTROUTING -o <dn_interface> -j MASQUERADE
sudo systemctl stop ufw

Note: In Ubuntu Server 20.04 and 22.04 the dn_interface may be called enp0s3 or enp0s4 by default. Use the command ip a to help to figure it out

In addition, execute the following command:

sudo iptables -I FORWARD 1 -j ACCEPT

Tip: As per the information on the appendix page, it's possible to use a script to reload the config above automatically after reboot

Also, make sure you have make proper changes to the free5GC configuration files, then run ./run.sh:

cd ~/free5gc
./run.sh

At this time free5GC has been started.

B. Start OAI-RAN

Next, prepare three additional SSH terminals from your host machine (if you know how to use tmux, you can use just one).

In terminal 1: SSH into oai-ran, make sure OAI-RAN is built, and configuration files have been changed correctly, then run gNB in simulation mode:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf --gNBs.[0].min_rxtxtime 6 --rfsim

In terminal 2, SSH into oai-ran, and run the ue in simulation mode:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ./nr-uesoftmodem --rfsim --rfsimulator.serveraddr 127.0.0.1 -r 106   --numerology 1 --band 78 -C 3619200000 --ssb 516 -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf

In terminal 3, SSH into oai-ran, and ping 192.168.56.101 to see free5gc is alive. Then, use ifconfig to see if the tunnel oaitun_ue1 has been created (by nr-ue):

ifconfig

4: oaitun_ue1: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 500
    link/none
    inet 10.60.0.1/24 scope global oaitun_ue1
       valid_lft forever preferred_lft forever
    inet6 fe80::50f4:1d4b:3323:e3fe/64 scope link stable-privacy
       valid_lft forever preferred_lft forever

Now use ping:

ping -I oaitun_ue1 google.com

If ping gets replies, then free5GC is running properly. Congratulations!

References

About Us

Hi! I'm Chieh-Cheng Kuo, currently working on open source projects free5GC and L25GC-plus. I hope you find this blog useful, and feel free to contact me if you'd like to discuss anything!

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