Outdoor Over-The-Air (OTA) OpenAirInterface 5G SA Experiment

Platform: OpenAirInterface5g and Universal Software Radio Peripherals~(USRPs)

Resources used: NI N320 (BS), N320 host computer, USRP B210, B210 host computer, power amplifiers, Commscope SS-65M-R2 Sector BS Antenna, and Laird OC69421 UE Antenna

Description: This experiment features a 5G network deployment using containerized 5G software components of OpenAirInterface5g, i.e., a containerized gNB, a containerized nrUE, and a containerized core network deployed in Intel x86 servers. The core network is deployed in the data center and connects to the base station via long distance fiber backhaul connection. The following figure shows the 5G network created from the experiment.

Note

For OAI experiments, you have two options for the core network:

Use the ARA-provided core network: In this case you can use the core network provided by ARA. No separate resource reservation and container is required for the core network.
Deploy your own core network: Here, you need to reserve another node specifically for the core network and deploy the core network in a container.

Detailed Steps for the Experiment

Login to ARA portal with your credentials.

Create two reservations using the Project -> Reservations -> Leases tab from the dashboard. Since each base station serves specific UEs in its footprint, we need to take extra care while reserving the nodes for experiments as well as setting the configuration parameters for gNB and UE. The following are BS-UE combinations which are operational for the OAI outdoor experiment. You can make use of any resource combination listed below for your experiment.

Experiment Resource Combination 1 (for Curtiss Farm)

Resource No.	Site	Resource Type	Device Type	Device ID
1	Curtiss Farm	AraRAN	Base Station	000
2	Curtiss Farm	AraRAN	User Equipment	000, 001, or 002
3	FeedMill	AraRAN	User Equipment	000, 001

Experiment Resource Combination 2 (for Agronomy Farm)

Resource No.	Site	Resource Type	Device Type	Device ID
1	Agronomy Farm	AraRAN	Base Station	000
2	Agronomy Farm	AraRAN	User Equipment	000, 001, 010, 020, or 032

Experiment Resource Combination 3 (for Wilson Hall)

Resource No.	Site	Resource Type	Device Type	Device ID
1	Wilson Hall	AraRAN	Base Station	000
2	Ames	AraRAN	User Equipment	000 or 140

Experiment Resource Combination 4 (for Gilbert)

Resource No.	Site	Resource Type	Device Type	Device ID
1	Gilbert	AraRAN	Base Station	000
2	Gilbert	AraRAN	User Equipment	003

For the core network, we can reserve any compute node. For this experiment, we use the following reservation.

Site	Resource Type	Device Type	Device ID
Data Center	Compute Node	Compute	000 or 001

Create an extra reservation for the 5G_Core using the Project -> Reservations -> Leases tab from the dashboard (Only if you are using Option 2 on the core network above, i.e., if you are creating your own core network.)

Create the containers on the respective nodes as provided in the following table.

Component/Reservation	Container Image	CPU	Memory	Network
Base Station (gNB)	`arawirelesshub/openairinterface5g:gnb_generic_v1`	8	8192	ARA_Shared_Net
User Equipment (nrUE)	`arawirelesshub/openairinterface5g:ue_generic_v1`	8	8192	ARA_Shared_Net
Core Network (Only if you use core network Option 2.)	`arawirelesshub/openairinterface5g:cn`	8	8192	ARA_Shared_Net

For FeedMill UEs, use the docker images specified in the follwoing table.

Component/Reservation	Container Image	CPU	Memory	Network
FeedMill-UE-000	`arawirelesshub/openairinterface5g:ue_generic_v1_feedmill`	8	8192	ARA_Shared_Net
FeedMill-UE-001	`arawirelesshub/openairinterface5g:ue_generic_v1_feedmill01`	8	8192	ARA_Shared_Net

Note

In case if you face any errors while launching container, refer to our FAQ.

Once the container is launched, take a note on the floating IP if you want to access the container from your PC via ARA jumpbox. The containers can be accessed via the console tab of the respective containers in the Project -> Containers tab from the dashboard or using ssh via the jumpbox server. Visit ARA Jumpbox for more information on accessing containers via jumpbox.
In both containers, run the following command to check the radios connected to the host. In case the command cannot find SDR, refer the instructions in FAQ.
```
# uhd_find_devices
```
The output of the above command should look like the following image.

Base Station

Note: The base station may show multiple SDRs, each corresponding to one sector.

User Equipment
[OPTIONAL: Execute this step only if you are running your own 5G core network. If you are using ARA-provided core network, skip this step.] In the 5G_Core container, run the following commands to start OAI 5G Core.
```
# cd oai-cn5g
# docker compose up -d
# iptables -P FORWARD ACCEPT
```
Note the IP address of the interface eth0 in the container by executing the command.
```
# ifconfig eth0
```
For this experiment, we assume that the IP address of the core network container is 10.0.4.100.
To make the gNB connected to the core network, you need to attach the gNB to the AMF of the core network. First note down the IP address of the interface eth0 of the gNB container by executing the following command in the terminal.
```
# ifconfig eth0
```
For this experiment, we assume that the IP address of gNB is 10.0.4.44.

Open the gNB configuration file with the following command.

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

Make the necessary changes as shown in the figure below.

Edit the lines, shown in the image below, with the IP address you obtained in Step 9. Use /24 subnet mask while specifying the IP address, i.e., 10.0.4.44/24

Modify the line shown in the figure below with the respective attributes and values provided in the table. The IP address given to sdr_addrs depends on the UE we use for the experiment.

User Equipment	`sdr_addrs` value
CurtissFarm-UE-000, FeedMill-UE-[000, 001]	`sdr_addrs = "addr=192.168.40.2";`
AgronomyFarm-UE-[020, 032], Ames-UE-140	`sdr_addrs = "addr=192.168.30.2";`
All other UEs	`sdr_addrs = "addr=192.168.20.2";`

Once the modification is complete, save (Press Ctrl+O) and exit (Press Ctrl+X) the nano editor.

Add a route to the core network from the gNB container with the following command at the gNB container.

Case 1: If you are using ARA-provided 5G core network: Use the following command.
```
# ip route add 192.168.70.128/26 via 10.0.4.4 dev eth0
```
Case 2: If you are using your own core network: Use the IP address obtained from Step 8 (in this example it is 10.0.4.100) in the command as follows.
```
# ip route add 192.168.70.128/26 via 10.0.4.100 dev eth0
```
To test the reachability of the 5G Core from the gNB container, run a ping in the gNB container toward the AMF of the core network.
```
# ping 192.168.70.132
```

Running the Base Station: In the gNB container, run the OAI gNB using the following commands. In case of any error, refer our FAQ.

gNB command for connecting to FeedMill-UE-000:

# cd ~/openairinterface5g
# source oaienv
# cd cmake_targets/ran_build/build
# patch -f -u ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf -i  ../../../freq.patch
# ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf --gNBs.[0].min_rxtxtime 6 --sa --usrp-tx-thread-config 1 --RUs.[0].att_tx 0 --RUs.[0].att_rx 30

gNB command for connecting to FeedMill-UE-001:

# cd ~/openairinterface5g
# source oaienv
# cd cmake_targets/ran_build/build
# patch -f -u ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf -i  ../../../freq1.patch
# ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf --gNBs.[0].min_rxtxtime 6 --sa --usrp-tx-thread-config 1 --RUs.[0].att_tx 0 --RUs.[0].att_rx 30

gNB command for connecting to Agronomy Farm UE with ID 020:

# cd ~/openairinterface5g
# source oaienv
# cd cmake_targets/ran_build/build
# ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf --gNBs.[0].min_rxtxtime 6 --sa --usrp-tx-thread-config 1 --RUs.[0].att_tx 0 --RUs.[0].att_rx 27

gNB command to connect to all other UEs:

# cd ~/openairinterface5g
# source oaienv
# cd cmake_targets/ran_build/build
# ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf --gNBs.[0].min_rxtxtime 6 --sa --usrp-tx-thread-config 1 --RUs.[0].att_tx 0 --RUs.[0].att_rx 33

An important parameter that users want to change is the center frequency. Even though it is advisable to keep it default, the center frequency can be modified using the following two parameters in the above-mentioned configuration file.
1. absoluteFrequencySSB
2. dl_absoluteFrequencyPointA
The parameters above take NR ARFCN values for the specific center frequency. You can use the online 5G NR ARFCN Calculator to get the absoluteFrequencySSB in case if you are not familiar with the low-level calculation. To obtain the corresponding dl_absoluteFrequencyPointA, subtract 1272 from the absoluteFrequencySSB value.
Starting nrUE: In the UE container, run the OAI nrUE using the following commands. In case of error or UE not connecting to gNB, refer FAQ.

Note

If you want to connect multiple UEs to the same BS, configure the UEs as provided here before executing the following commands.

nrUE commands for FeedMill-UE-000
```
# cd ~/openairinterface5g
# source oaienv
# cd cmake_targets/ran_build/build
# ./nr-uesoftmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf -r 106 --numerology 1 --band 78 -C 3619200000 --ue-fo-compensation --sa -E --ue-txgain 0 --nokrnmod 1
```
nrUE commands for all UEs
```
# cd ~/openairinterface5g
# source oaienv
# cd cmake_targets/ran_build/build
# ./nr-uesoftmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf -r 106 --numerology 1 --band 78 -C 3416160000 --ue-fo-compensation --sa -E --ue-txgain 0 --nokrnmod 1
```
Important

It may happen that the UE (for example, Ames-UE-140) may not get connected in the first attempt due to factors such as interference and line-of-sight~(LoS) blockage. In such cases, stopping and running the UE command again provides a higher chance of getting the UE connected.

Console Traces

On establishing a successful connection, the commands provide the following output.

gNB Console Trace

nrUE Console Trace

Note

When the connection is established, we can observe a new interface oaitun_ue1 at the nrUE container with an IP address assigned by the SMF of the core network. In order to find the IP address, open (or SSH into) another terminal for nrUE container and run the command ifconfig. For this experiment, we assume that the IP obtained is 10.0.0.2.

In this experiment, the interface name assigned to the nrUE by the SMF is given as oaitun_ue1, which is used in the commands provided in the steps below.
Ping test to the Core Network: On the nrUE container, run the following command to ping the core network to ensure stable connection.
```
# ping -I oaitun_ue1 192.168.70.135
```
An example output of the ping command is shown below.

For recording the ping output to a text file (say ping_output.txt), we can use the following command.
```
# ping 192.168.70.135 -I oaitun_ue1 | tee ping_output.txt
```
For sending 10 packets with an inter-packet interval of 0.5 seconds, use the -c and -i options, respectively, as follows.
```
# ping 192.168.70.135 -I oaitun_ue1 -c 10 -i 0.5 | tee ping_output.txt
```
The file can be further copied to local machine using the instructions provided in Experiment Data Collection.

Throughput Test

For Case-1 with ARA-provided Core Network

If you are using ARA-provided core network, you can measure ONLY the uplink throughput. Execute the following command at the nrUE container.
```
# iperf -c 192.168.70.135 -u -b 2M --bind 10.0.0.2
```
The iPerf client command provides the throughput as follows:

For Case-2 with Your Own Core Network

Downlink Throughput: For measuring the throughput, we use the tool iperf. For the downlink throughput, follow the steps below.
1. Run the iperf server in the nrUE container using the following command. Remember to use the ip address of the oaitun_ue1 interface. In what follows, we assume the IP to be 10.0.0.2.
```
# iperf -s -i 1 -u -B 10.0.0.2
```
2. Run the iperf client in the 5G core container. Remember to use the IP address of the oaitun_ue1 interface in nrUE after the -c flag. In what follows, we assume the UE IP to be 10.0.0.2.
```
# docker exec -it oai-ext-dn iperf -c 10.0.0.2 -u -b 2M --bind 192.168.70.135
```
  The iPerf client measures the throughput as shown in the figure in Step 15.
Uplink Throughput: For the uplink, we need to run the iperf server at the 5G core and iperf client at the nrUE.
1. For the uplink throughput, first, run the iperf server at the 5G core network.:
```
# docker exec -it oai-ext-dn iperf -s -i 1 -u -B 192.168.70.135
```
2. Run iperf client in the nrUE container. Remember to use the IP address of the oaitun_ue1 interface at nrUE after the --bind flag. In what follows, we assume the UE IP to be 10.0.0.2.
```
# iperf -c 192.168.70.135 -u -b 2M --bind 10.0.0.2
```
  The iPerf client measures the throughput as shown in the figure in Step 15.

Connecting multiple UEs to BS

It is possible in this experiment to connect multiple UEs to the same BS. For example, Curtiss Farm BS (CurtissFarm-BS-000) has two UEs (CurtissFarm-UE-001 and CurtissFarm-UE-002) in its vicinity ready for establishing links. For establishing a second link, we need to create an additional lease for the second UE at Curtiss Farm and launch the UE container following the same procedure as described above.

In addition to launching containers, we need to modify the IMSI value in the configuration file of both UEs using the following steps:

Open the UE configuration file.
```
# nano /root/openairinterface5g/targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf
```
For connecting multiple UEs, it is important to note that each UE should have different values for the imsi attribute in the configuration file. By default the configuration file has the imsi value 001010000000001. For the first UE, we can keep it as it is and, for the second UE, we can change it to 001010000000002 (changing the last digit) as follows:

After modifying imsi, save and exit from the file. Use Ctrl+X to save and exit if you are using the nano editor.
Run the nrUE at each UE using Step 12 described above.

Tip

If you want to perform weather measurements along with the RAN experiments, refer to ARA Weather APIs.