% OAI Hands-On Session % Rajeev Gangula, Chandra R. Murthy, Rakesh Mundlamuri, Vinay Kulkarni, Venkatareddy Akumalla % December 15, 2025

What do we cover in the OAI Hands-On Session?

The aim of this tutorial is to:

Set-up of end-to-end monolithic 5G/NR SA setup with RFsimulator from source
Add a custom UE
Configuring TDD pattern
Configuring bandwidth
CU-DU split
Working with multiple UE's

Install required software utilities

1. Git

sudo apt-get update
sudo apt-get install git

2. Wireshark

Make sure to select yes when the Wireshark installation asks you whether non-superusers should be able to capture packets. Otherwise, you will have to run in sudo mode.

sudo add-apt-repository ppa:wireshark-dev/stable
sudo apt update
sudo apt install -y git net-tools wireshark

3. Networking

sudo apt install -y iperf3

Install required software utilities

4. Docker

sudo apt install -y apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu  $(lsb_release -cs)  stable"
sudo apt update
sudo apt install -y docker docker-ce

Add your username to the docker group, otherwise you will have to run in sudo mode.

sudo usermod -a -G docker $(whoami)

Now, close the terminal tab and re-open it.

OAI 5G core: Procedure to pull and run docker images

clone the repository

git clone https://github.com/RajeevGa/ieee_ants2024_oai_tutorial.git
cd ieee_ants2024_oai_tutorial/cn

If you dont have a docker account, create a docker account in docker signup

docker login -u <username>

Enter your password

OAI 5G core: Procedure to pull and run docker images

Now, pull the 5G core docker images

docker compose pull

start core network

docker compose -f docker-compose.yaml up -d

watch status of the core network

watch docker compose -f docker-compose.yaml ps -a

All the docker containers should be healthy

Procedure to install and run OAI basestation (gNB) and the user equipment (nrUE)

Open a new ssh terminal and clone the ran repository

git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git

compile the gNB and nrUE

cd openairinterface5g/
git checkout 2024.w46
source oaienv
cd cmake_targets/
./build_oai -I  
./build_oai -w SIMU --gNB --nrUE --ninja

Key parameters to check in the configuration files: mcc, mnc, sst, sd

5G Core:

~/ieee_ants2024_oai_tutorial/cn/conf/config.yaml

gNB:

~/ieee_ants2024_oai_tutorial/ran/conf/gnb.sa.band78.106prb.rfsim.conf

nrUE:

~/ieee_ants2024_oai_tutorial/ran/conf/ue.conf

Run the gNB

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo -E ./nr-softmodem --rfsim -O ~/ieee_ants2024_oai_tutorial/ran/conf/gnb.sa.band78.106prb.rfsim.conf

Verify gNB connected to 5G Core:

[NGAP]   Send NGSetupRequest to AMF
[NGAP]   3584 -> 0000e000
[NGAP]   Received NGSetupResponse from AMF
[GNB_APP]   [gNB 0] Received NGAP_REGISTER_GNB_CNF: associated AMF 1

Run the UE from a second terminal:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo -E ./nr-uesoftmodem -r 106 --numerology 1 --band 78 -C 3619200000 --rfsim --ssb 516 -O ~/ieee_ants2024_oai_tutorial/ran/conf/ue.conf

Verify end-to-end connectivity: you should see the following in the logs:

gNB:

Check for RRC_CONNECTED state:

[NR_MAC]    330. 0 UE b010: Received Ack of Msg4. CBRA procedure succeeded!
[NR_RRC]   [UL] (cellID bc614e, UE ID 1 RNTI b010) Received RRCSetupComplete (RRC_CONNECTED reached)

Check for Authentication:

[NR_RRC]   UE 1 Logical Channel DL-DCCH, Generate SecurityModeCommand (bytes 3)
[NR_RRC]   [UL] (cellID bc614e, UE ID 1 RNTI b010) Received Security Mode Complete

Check for PDU sessions:

[NR_RRC]   [DL] (cellID bc614e, UE ID 1 RNTI c40a) Generate RRCReconfiguration (bytes 307, xid 3)
[RRC]   UE 1: PDU session ID 10 modified 1 bearers
[NR_RRC]   [UL] (cellID bc614e, UE ID 1 RNTI c40a) Received RRCReconfigurationComplete
[NR_RRC]   msg index 0, pdu_sessions index 0, status 2, xid 3): nb_of_pdusessions 1,  pdusession_id 10, teid: 2817854240 
[NR_RRC]   NGAP_PDUSESSION_SETUP_RESP: sending the message

nrUE:

Check for RRC_CONNECTED state:

[NR_RRC]   State = NR_RRC_CONNECTED
[NR_RRC]   [UE 0][RAPROC] Logical Channel UL-DCCH (SRB1), Generating RRCSetupComplete (bytes33)

Check for Authentication:

[NAS]   [UE] Received REGISTRATION ACCEPT message

Check for oaitun_ue1 creation:

[NR_RRC]    Logical Channel UL-DCCH (SRB1), Generating RRCReconfigurationComplete (bytes 2)
[OIP]   Interface oaitun_ue1 successfully configured, IPv4 10.0.0.7, IPv6 (null)

Correspondingly, an interface should have been brought up:

oaitun_ue1: flags=209<UP,POINTOPOINT,RUNNING,NOARP>  mtu 1500
        inet 10.0.0.7  netmask 255.255.255.0  destination 10.0.0.7
        inet6 fe80::60bd:b117:1bb0:47c4  prefixlen 64  scopeid 0x20<link>
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 500  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 5  bytes 240 (240.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Wireshark traces

Log the traces using tcpdump as follows

sudo tcpdump -i oai-cn5g -w monolithic.pcap

5G Standalone Call flow

Ping test

Check the UE's IP address: interface oaitun_ue1 using ifconfig
The IP address 192.168.70.135 is the IP address of the oai-ext-dn container.
Ping:

ping -I oaitun_ue1 192.168.70.135                 # from host, "UL", to oai-ext-dn
docker exec -it oai-ext-dn ping <UE IP address>   # from container, "DL"

Iperf test

Iperf3 testing between oai-ext-dn (in Docker) and the UE (running locally)

docker exec -it oai-ext-dn bash
iperf3 -s

on the host in new terminal, run iperf3 client and bind the UE IP address:

iperf3 -B <UE IP ADDRESS> -c 192.168.70.135 -u -b 50M -R # DL
iperf3 -B <UE IP ADDRESS> -c 192.168.70.135 -u -b 20M    # UL

Add a custom UE

Create a UE config file ue2.conf with the following structure.

uicc0 = {
  imsi = "001010000000002";
  key = "fec86ba6eb707ed08905757b1bb44b8f";
  opc= "C42449363BBAD02B66D16BC975D77CC1";
  dnn= "oai";
  nssai_sst=1;
}

Add this UE infomation to the core database in cn/database/oai_db.sql

Add the imsi, key and opc infomation of the UE to the AuthenticationSubscription table as follows

INSERT INTO `AuthenticationSubscription` (`ueid`, `authenticationMethod`, `encPermanentKey`, `protectionParameterId`, `sequenceNumber`, `authenticationManagementField`, `algorithmId`, `encOpcKey`, `encTopcKey`, `vectorGenerationInHss`, `n5gcAuthMethod`, `rgAuthenticationInd`, `supi`) VALUES
    ('001010000000002', '5G_AKA', 'fec86ba6eb707ed08905757b1bb44b8f', 'fec86ba6eb707ed08905757b1bb44b8f', '{\"sqn\": \"000000000000\", \"sqnScheme\": \"NON_TIME_BASED\", \"lastIndexes\": {\"ausf\": 0}}', '8000', 'milenage', 'C42449363BBAD02B66D16BC975D77CC1', NULL, NULL, NULL, NULL, '001010000000002');

Add the imsi, dnn and nssai_sst infomation of the UE to the SessionManagementSubscriptionData table as follows

INSERT INTO `SessionManagementSubscriptionData` (`ueid`, `servingPlmnid`, `singleNssai`, `dnnConfigurations`) VALUES
('001010000000002', '00101', '{\"sst\": 1, \"sd\": \"FFFFFF\"}','{\"oai\":{\"pduSessionTypes\":{ \"defaultSessionType\": \"IPV4\"},\"sscModes\": {\"defaultSscMode\": \"SSC_MODE_1\"},\"5gQosProfile\": {\"5qi\": 6,\"arp\":{\"priorityLevel\": 15,\"preemptCap\": \"NOT_PREEMPT\",\"preemptVuln\":\"PREEMPTABLE\"},\"priorityLevel\":1},\"sessionAmbr\":{\"uplink\":\"1000Mbps\", \"downlink\":\"1000Mbps\"},\"staticIpAddress\":[{\"ipv4Addr\": \"10.0.0.3\"}]},\"ims\":{\"pduSessionTypes\":{ \"defaultSessionType\": \"IPV4V6\"},\"sscModes\": {\"defaultSscMode\": \"SSC_MODE_1\"},\"5gQosProfile\": {\"5qi\": 2,\"arp\":{\"priorityLevel\": 15,\"preemptCap\": \"NOT_PREEMPT\",\"preemptVuln\":\"PREEMPTABLE\"},\"priorityLevel\":1},\"sessionAmbr\":{\"uplink\":\"1000Mbps\", \"downlink\":\"1000Mbps\"}}}');

Restart the 5G core and use the config file ue2.conf while running OAI UE

Most common errors:

NGAP setup failure
Unidentified/Illegal UE
PDU session reject

Debug: wireshak traces and the logs

Configuring TDD Pattern

The TDD pattern can be found in the ran config file, an example TDD pattern with a periodicity 5ms can be seen below

# dl_UL_TransmissionPeriodicity
      # 0=ms0p5, 1=ms0p625, 2=ms1, 3=ms1p25, 4=ms2, 5=ms2p5, 6=ms5, 7=ms10
      dl_UL_TransmissionPeriodicity                                 = 6;   # periodicity of the TDD Pattern
      nrofDownlinkSlots                                             = 7;   # DL slots per each TDD period
      nrofDownlinkSymbols                                           = 6;   # DL symbols in a mixed slot
      nrofUplinkSlots                                               = 2;   # UL slots per each TDD period
      nrofUplinkSymbols                                             = 4;   # UL symbols in a mixed slot

Note: The subcarrier spacing choosen for the above mentioned configurations is 30 KHz

This can be configured as per our requirements, for example a TDD pattern with a periodicity 2.5ms can be seen below

# dl_UL_TransmissionPeriodicity
      # 0=ms0p5, 1=ms0p625, 2=ms1, 3=ms1p25, 4=ms2, 5=ms2p5, 6=ms5, 7=ms10
      dl_UL_TransmissionPeriodicity                                 = 5;   # periodicity of the TDD Pattern
      nrofDownlinkSlots                                             = 2;   # DL slots per each TDD period
      nrofDownlinkSymbols                                           = 6;   # DL symbols in a mixed slot
      nrofUplinkSlots                                               = 2;   # UL slots per each TDD period
      nrofUplinkSymbols                                             = 4;   # UL symbols in a mixed slot

Excercise: Perform iperf tests in both DL and UL. What do you observe?

Changing bandwidth configuration

Change the bandwidth to 20MHz configuration

Parameters that need to configured in the ran configuration file are

absoluteFrequencySSB                                        = 640704;  # SSB GSCN
dl_carrierBandwidth                                         = 51;
ul_carrierBandwidth                                         = 51;
initialDLBWPlocationAndBandwidth                            = 13750;   # RIV
initialULBWPlocationAndBandwidth                            = 13750;   # RIV

To run gNB

sudo -E ./nr-softmodem --rfsim -O ~/ieee_ants2024_oai_tutorial/ran/conf/gnb.sa.band78.51prb.rfsim.conf

To run UE

sudo ./nr-uesoftmodem -r 51 --numerology 1 --band 78 -C 3609300000 --rfsim --ssb 228 -O ~/ieee_ants2024_oai_tutorial/ran/conf/ue.conf

Resources for calculating SSB GSCN and resources for calculating RIV

similarly, a configuration file for 100MHz has been provided gnb.sa.band78.273prb.rfsim.conf

To run gNB

sudo -E ./nr-softmodem --rfsim -O ~/ieee_ants2024_oai_tutorial/ran/conf/gnb.sa.band78.273prb.rfsim.conf

To run UE

sudo ./nr-uesoftmodem -r 273 --numerology 1 --band 78 -C 3649260000 --rfsim --ssb 516 -O ~/ieee_ants2024_oai_tutorial/ran/conf/ue.conf

CU-DU F1 split

To start CU:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo -E ./nr-softmodem -O ~/ieee_ants2024_oai_tutorial/ran/conf/gnb-cu.sa.f1.conf

To start DU:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo -E ./nr-softmodem --rfsim -O ~/ieee_ants2024_oai_tutorial/ran/conf/gnb-du.sa.band78.106prb.rfsim.conf

Run the UE:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo -E ./nr-uesoftmodem -r 106 --numerology 1 --band 78 -C 3619200000 --rfsim --ssb 516 -O ~/ieee_ants2024_oai_tutorial/ran/conf/ue.conf

Multiple UE's

To start gNB:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo -E ./nr-softmodem --rfsim -O ~/ieee_ants2024_oai_tutorial/ran/conf/gnb.sa.band78.106prb.rfsim.conf

To start UE1:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ~/ieee_ants2024_oai_tutorial/ran/multi-ue.sh -c1 -e
sudo -E ./nr-uesoftmodem -r 106 --numerology 1 --band 78 -C 3619200000 --rfsim -O /home/rakeshmundlamuri7/ieee_ants2024_oai_tutorial/ran/conf/ue1.conf --rfsimulator.serveraddr 10.201.1.100

To start UE2:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ~/ieee_ants2024_oai_tutorial/ran/multi-ue.sh -c2 -e
sudo -E ./nr-uesoftmodem -r 106 --numerology 1 --band 78 -C 3619200000 --rfsim -O /home/rakeshmundlamuri7/ieee_ants2024_oai_tutorial/ran/conf/ue2.conf --rfsimulator.serveraddr 10.202.1.100

To login to ue1 namespace

sudo ip netns exec ue1 bash

To login to ue1 namespace

sudo ip netns exec ue2 bash

You can now perform ping and iperf tests

ping from UE1

ping -I oaitun_ue1 192.168.70.135                 # from host, "UL", to oai-ext-dn

ping from UE2

ping -I oaitun_ue1 192.168.70.135                 # from host, "UL", to oai-ext-dn

To remove the namespaces

sudo ~/ieee_ants2024_oai_tutorial/ran/multi-ue.sh -d1 -d2

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Install required software utilities

1. Git

2. Wireshark

3. Networking

Install required software utilities

4. Docker

OAI 5G core: Procedure to pull and run docker images

OAI 5G core: Procedure to pull and run docker images

Procedure to install and run OAI basestation (gNB) and the user equipment (nrUE)

Key parameters to check in the configuration files: mcc, mnc, sst, sd

Wireshark traces

5G Standalone Call flow

Ping test

Iperf test

Add a custom UE

Most common errors:

Configuring TDD Pattern

Changing bandwidth configuration

CU-DU F1 split

Multiple UE's