== LTE Traffic Trace Collection ==
This wiki page contains the tutorial to collect traffic traces for realtime application such as video, web, mail etc. at RLC, MAC and PDCP layer of LTE protocol stack in ORBIT testbed using OpenAirInterface (OAI).Users were connected over the air using b210 USRPs and data/logs recorded at eNodeB were extraced using standard linux tools. A high level system diagram is given below.

||||||Figure 1: System Diagram - Trace Collection||
 || [[Image(Intro.jpg, 325px)]] || 

=== Description ===
For this experiments we need UEs, eNB having b210s USRP, two other nodes for EPC and Server are also needed. We have used grid sandbox with node8-7 as eNB; node13-7, node13-14 and node8-14 as UEs; node2-2 as EPC; node3-2 as server. More UEs can be added but we have tested with just 3 users in this experiment. A detailed system diagram with list of all the interfaces is given below. This tutorial will cover following sections:
* Setup OAI emulation framework
* Connecting UE to LTE network
* Connecting Multiple UEs
* Running OAI logging Module
* Application Design
* Trace collection and Evaluation

||||||Figure 2: GRID OAI System Design Implementaion - Trace Collection||
 || [[Image(topology.jpg, 650px)]] || 

=== Setup OAI emulation framework ===
1) Loading an image into ORBIT node

* Loading UE image: \\
  UE1: {{{omf load -i ue1.ndz -t node13-14}}}\\
  UE2: {{{omf load -i ue2.ndz -t node13-7}}}\\
  UE3: {{{omf load -i ue3.ndz -t node8-14}}}

* Loading eNB image: \\
  eNB: {{{omf load -i enb.ndz -t node8-7}}}

* Loading EPC image: \\
  EPC: {{{omf load -i epc.ndz -t node2-2}}}

* Loading Server image: \\
  Server: {{{omf load -i baseline.ndz -t node3-2}}}

After loading the image turnon the nodes using command: {{{omf tell -a on -t node13-14,node13-7,node8-14,node8-7,node3-2,node2-2}}}

2) Starting EPC : Run the following commands to enable eth0 interface and to start EPC components - HSS, MME and SPGW:
{{{
ssh root@node2-2
cd /root/openair-cn/SCRIPTS 
ifconfig eth0 192.168.3.1/24 up 
./run_hss 
./run_mme 
./run_spgw
}}}

3) Configuring Server
{{{
ssh root@node3-2
ifconfig eth0 192.168.3.2/24 up
ip route add 172.16.0.2 via 192.168.3.1
}}}

4) Starting eNodeB
{{{
ssh root@node8-7
ifconfig eth1 mtu 1440
cd /root/openairinterface5g/cmake_targets/lte_build_oai/build
sudo -E ./lte-softmodem -P /tmp/oai_enb.pcap -O /root/openairinterface5g/targets/PROJECTS/GENERIC-LTE-EPC/CONF/enb.band7.tm1.25PRB.usrpb210.conf --T_nowait
}}}

=== Connecting UE to LTE network ===
Considering UE1
{{{
ssh root@node13-14
cd /root/openairinterface5g/cmake_targets/tools/
source ./init_nas_s1 UE
cd /root/openairinterface5g/targets/bin
sudo -E ./lte-softmodem.Rel14 -U -C2685000000 -r25 --ue-scan-carrier --ue-txgain 70 --ue-rxgain 80 -W
}}}

In a separate terminal 
{{{
ssh root@node13-14
sudo ifconfig oip1 up
ifconfig oip1 mtu 800
route add default gw 172.16.0.2
}}}

The Tx and Rx gain have to adjusted based on physical location of UE and eNB