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BASIC_SIM.md

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Running OAI Basic Simulator

This page is valid on the following branches:

  • master starting from tag v1.1.0
  • develop starting from tag 2019.w11

1. Building the basic-simulator.

After the build simplification, the basic simulator is available directly from the standard build.

$ source oaienv
$ cd cmake_targets
$ ./build_oai --eNB --UE

Both eNB (lte-softmodem) and UE (lte-uesoftmodem) are present on cmake_targets/lte_build_oai/build folder.

More details are available on the build page.

2. Running the basic simulator.

The basic simulator is a oai device replacing the radio heads (for example the USRP device). It allows connecting the oai UE and the oai eNodeB through a network interface carrying the time-domain samples, getting rid of over the air unpredictable perturbations.

This is the ideal tool to check signal processing algorithms and protocols implementation and having debug sessions without any HW radio equipment.

The main limitations are:

  • A single OAI UE will connect to the OAI eNB
  • No channel noise

2.1. Starting eNB

The basic simulator is able to run with a connected EPC or without any (the so-called "noS1" mode).

Example 1: running in FDD mode with EPC.

$ source oaienv
$ cd cmake_targets/lte_build_oai/build
$ ENODEB=1 sudo -E ./lte-softmodem -O $OPENAIR_HOME/ci-scripts/conf_files/lte-fdd-basic-sim.conf --basicsim

Edit previously the ci-scripts/conf_files/lte-fdd-basic-sim.conf file to modify:

  • N_RB_DL field to change the Bandwidth (25, 50, 100)
  • CI_MME_IP_ADDR with the EPC IP address
  • CI_ENB_IP_ADDR with the container (physical server, virtual machine, ...) on which you are executing the eNB soft-modem

Example 2: running in TDD mode without any EPC.

$ source oaienv
$ cd cmake_targets/lte_build_oai/build
$ ENODEB=1 sudo -E ./lte-softmodem -O $OPENAIR_HOME/ci-scripts/conf_files/lte-tdd-basic-sim.conf --basicsim --noS1

2.2. Starting UE

Before starting the UE, you may need to edit the SIM parameters to adapt to your eNB configuration and HSS database.

The file to use for conf2uedate is openair3/NAS/TOOLS/ue_eurecom_test_sfr.conf

You need to set the correct OPC, USIM_API_K, MSIN (this is the end par of the IMSI), HPLMN (the front part of IMSI) to match values from HSS.

$ source oaienv
# Edit openair3/NAS/TOOLS/ue_eurecom_test_sfr.conf
$ cd cmake_targets/lte_build_oai/build
$ ../../nas_sim_tools/build/conf2uedata -c $OPENAIR_HOME/openair3/NAS/TOOLS/ue_eurecom_test_sfr.conf -o .
$ sudo -E ./lte-uesoftmodem -C 2625000000 -r 25 --ue-rxgain 140 --basicsim [--noS1]

The -r 25 is to use if in the conf file of the eNB you use N_RB_DL=25. Use 50 if you have N_RB_DL=50 and 100 if you have N_RB_DL=100.

The -C 2625000000 is the downlink frequency. Use the same value as downlink_frequency in the eNB configuration file.

The --noS1 is mandatory if you started the eNB in that mode.

3. Testing the data plane

3.1. In S1 mode

First we need to retrieve the IP address allocated to the OAI UE.

On the server that runs the UE:

$ ifconfig oaitun_ue1
oaitun_ue1 Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
            inet addr:192.172.0.2  P-t-P:192.172.0.2  Mask:255.255.255.0
...

192.172.0.2 is the IP address that has been allocated by the SPGW in the EPC.

On the server that runs the EPC:

$ ping -c 20 192.172.0.2
  --- 192.172.0.2 ping statistics ---
  20 packets transmitted, 20 received, 0% packet loss, time 19020ms
  rtt min/avg/max/mdev = 13.241/18.999/24.208/2.840 ms

You can ping the EPC from the UE:

$ ping -I oaitun_ue1 -c 20 192.172.0.1
  --- 192.172.0.1 ping statistics ---
...
  20 packets transmitted, 20 received, 0% packet loss, time 19019ms
  rtt min/avg/max/mdev = 13.015/18.674/23.738/2.917 ms

For DL iperf testing:

On the server that runs the UE.

$  iperf -B 192.172.0.2 -u -s -i 1 -fm -p 5001

On the server that runs the EPC.

$  iperf -c 192.172.0.2 -u -t 30 -b 10M -i 1 -fm -B 192.172.0.1 -p 5001

For UL iperf testing:

On the server that runs the EPC.

$  iperf -B 192.172.0.1 -u -s -i 1 -fm -p 5001

On the server that runs the UE.

$  iperf -c 192.172.0.1 -u -t 30 -b 2M -i 1 -fm -B 192.172.0.2 -p 5001

3.2. In noS1 mode

The IP addresses are fixed. But we can still retrieve them programmatically.

For the UE it is quite the same:

$ ifconfig oaitun_ue1
oaitun_ue1 Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
            inet addr:10.0.1.2  P-t-P:10.0.1.2  Mask:255.255.255.0
...

For the eNB:

$ ifconfig oaitun_enb1
oaitun_enb1 Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
            inet addr:10.0.1.1  P-t-P:10.0.1.1  Mask:255.255.255.0
...

Pinging like this:

$ ping -I oaitun_ue1 -c 20 10.0.1.1
$ ping -I oaitun_enb1 -c 20 10.0.1.2

And the same for iperf:

$ iperf -B 10.0.1.2 -u -s -i 1 -fm
$ iperf -c 10.0.1.2 -u -b 1.00M -t 30 -i 1 -fm -B 10.0.1.1