== !OpenAirInterface LTE == 

[[Include(Documentation/Short/Prereq)]]

This tutorial also assumes basic familiarity with [http://en.wikipedia.org/wiki/LTE_%28telecommunication%29 LTE standard]. It uses [http://www.openairinterface.org/ OpenAirInterface] open source software implementation of LTE basestation (eNodeB or eNB) and modem (user equipment or UE) developed at [http://www.eurecom.fr/en Eurecom]. The tutorial given here is based on the [https://twiki.eurecom.fr/twiki/bin/view/OpenAirInterface/HowToConnectOAIENBWithOAIUEWithoutS1Interface] tutorial.

The image used for this experiment is oai-nos1.ndz. Image uses Ubunutu 14.04 and has low-latency 3.13 kernel install and UHD drivers needed for B210/X310 USRPs (UHD 3.8.2)) as well as the !OpenAirInteface source code installed in /root/openairinterface5g/. More details on various build options are available on [https://twiki.eurecom.fr/twiki/bin/view/OpenAirInterface/AutoBuild OpenAirInterface build page].

In this tutorial we will use nodes equipped with USRP B210 and have the basestation on node1-1 and modem on node1-2 on sandbox 1. 

=== Prepare the nodes ===

 1. Load the image with the !OpenAirInterface code on the nodes. After imaging the nodes are '''turned off automatically'''. [[CollapsibleStart(omf load -i oai-nos1.ndz -t all)]] [[Include(Documentation/Short/LoadImage)]][[CollapsibleEnd]] 
 1. Turn ON the nodes that successfully imaged (give them some time and check their status with '''omf stat''' before proceeding). [[CollapsibleStart(omf tell -a on -t all)]][[Include(Documentation/Short/TellOn)]][[CollapsibleEnd]]

=== Execute the experiment ===

Primary objective is to establish the LTE connection between the UE and eNB.
  1. '''ssh into nodes:''' Open two ssh sessions from the console to the two nodes
  2. '''Prepare configuration files:''' The configuration file used for eNB is ''enb.band5.tm1.usrpb210.conf'', located at ''/root/openinterface5g/targets/PROJECTS/GENERIC-LTE-EPC/CONF/''. Another configuration may be used, or a new configuration file can be created using one of the existing ones, so that the parameters can be adjusted.
  3. '''Run the lte-softmodem:''' The following commands need to be run in order the execute the LTE softmodem. By default, the IP address of eNB is 10.0.1.1, and the IP of UE is 10.0.1.9. These parameters can be changed in ''/root/openinterface5g/targets/bin/init_nas_nos1''. The user can also choose whether to run the version with or without the graphical analyzer. In order to run the experiment with the graphical analyzer, make sure you have used the '-X' flag to ssh into the console and then into the nodes.

    a. On both nodes, run

{{{
source /root/openairinterface5g/targets/bin/init_nas_nos1
}}}

    b. On eNB (node1-1), run

{{{
sh /root/openairinterface5g/targets/bin/init_nas_nos1 eNB

/root/openairinterface5g/targets/bin/oailtenoviz -d -O /root/conf/enb.band5.tm1.usrpb210.conf 2>&1 | tee ENB.log
}}}

or, to run it without the graphical analyzer

{{{
/root/openairinterface5g/targets/bin/lte-softmodem-nos1.Rel10 -d -O /root/conf/enb.band5.tm1.usrpb210.conf 2>&1 | tee ENB.log
}}}

    c. On UE (node1-2), run

{{{
/root/openairinterface5g/targets/bin/lte-softmodem-nos1.Rel10 -U -C879000000 -r25 --ue-scan-carrier --ue-txgain 100 --ue-rxgain 110 -A 2 2>&1 | tee UE.log
}}}

The connection should now be established. As a simple test, you should be able to ping the eNB node from the UE node by running

{{{
ping 10.0.1.1
}}}