# Overview
This tutorial contains instructions for running the openairinterface eNB and UE on various platforms.
It adapts the Eurecom tutorial at : https://gitlab.eurecom.fr/oai/openairinterface5g/wikis/HowToConnectOAIENBWithOAIUEWithoutS1Interface
for the ORBIT and COSMOS testbeds.

# Prerequisites
1. Two nodes, with appropriate hardware, within RF range
1. Currently supported: USRP x310, USRP 2974, USRP b210
1. Load the image `tutorial-oai.ndz` onto both nodes
1. Turn the nodes on
1. If graphical display is desired, enable x11 tunneling to console and then to nodes
1. ssh to the nodes

## On node 1
1. run `/opt/oaiscripts/build_oai.sh` to build for the current hardware and kernel
1. edit the file `/opt/oaiscripts/run_enb.sh` for the SDR in use, for example, set SDR IP addr and max gain
1. run `/opt/oaiscripts/run_enb.sh`


Example script, change parameters as needed:
run_enb.sh:
```
#! /bin/bash
#sdr_addrs takes standard uhd arguments, such as:
#"type=x300,addr=192.168.40.2"  #x310 over direct network
#"type=x300,resource=rio0"      #x310 over pcie
#"type=b210"                    #b210 over usb
#values for RUs.[0] override config file, must be set per usrp type
#-d enables xforms charts

cd /opt/openairinterface5g
source oaienv
cd ./cmake_targets
./lte_build_oai/build/lte-softmodem \
-O $OPENAIR_HOME/ci-scripts/conf_files/enb.band7.tm1.25PRB.usrpb210.conf \
--nokrnmod 1 --noS1 --eNBs.[0].rrc_inactivity_threshold 0 \
--RUs.[0].att_tx 40 --RUs.[0].att_rx 0 \
--usrp-args "type=b200" \
-d
```

## On Node 2
1. run /opt/oaiscripts/build_oai.sh to build for the current hardware and kernel
1. edit the file /opt/oaiscripts/run_ue.sh for the SDR in use, for example, set SDR IP addr and max gain
1. run /opt/oaiscripts/run_ue.sh

Example script, change parameters as needed:
run_ue.sh
```
#! /bin/bash
#sdr_addrs takes standard uhd arguments, such as:
#"type=x300,addr=192.168.40.2"  #x310 over direct network
#"type=x300,resource=rio0"      #x310 over pcie
#"type=b210"                    #b210 over usb
#values for RUs.[0] override config file, must be set per usrp type
#-d enables xforms charts

cd /opt/openairinterface5g
source oaienv
cd ./cmake_targets/lte_build_oai/build
./lte-uesoftmodem \
-C 2680000000 -r 25 \
--ue-scan-carrier --nokrnmod 1 --noS1 \
--ue-rxgain 120 --ue-txgain 30 --ue-max-power 0 \
--ue-nb-ant-tx 1 --ue-nb-ant-rx 1 \
--usrp-args "type=b200" \
-d
```


# Results

## Once Both nodes are running
* if all is successfull, you shouuld see new interfaces on the two nodes, with addresses:
  * 10.0.1.1
  * 10.0.1.2
* you should be able to run ping, iperf, and so on




# Understanding xforms terms and plots
* Explanations from:
  * [Mathworks LTE](https://www.mathworks.com/help/lte/physical-channels.html)

* PBCH: physical broadcast channel
  * The PBCH carries part of the system information required for terminals to access the network
* PUSCH: physical uplink control channel
* PDCCH: physical downlink control channel
  * The PDCCH conveys control information, scheduling decisions for PDSCH reception, and for scheduling grants enabling transmission on the PUSCH.
* PUSCH: physical uplink shared channel
* PDSCH: physical downlink shared channel
  * The PDSCH carries user data and paging information to the terminal.


# Details and Troubleshooting
## Calibration
* physical attenuation
* received signal at UE
* received signal at eNB
* pdsch constellation at UE
* pdsch constellation at eNB

## Expected Performance
This depends on a number of factors, including:
* the total bandwidth (number of resource blocks)
  * 5mhz:25prb
  * 10mhz:50prb
  * 20mhz:100prb
* p(d/u)sch modulation:
  * qpsk
  * 16qam
  * 64qam
  * 256qam
* FDD vs TDD
* number of MIMO channels
* control vs data channel split

For the default config file in this tutorial, it's:
* 1/1 non-mimo
* FDD band 7
* 5mhz/25PRB
* up to 256qam, depending on signal
* control / data split of (0.25/0.75?)
* so you can expect up to 19mbps downlink at 64qam, and 25mbps downlink at 256qam


## Specifics per domain
### sb2.cosmos-lab.org
1. set usrp address to "type=x3xx,resource=rio0"
1. on eNB, set att_tx=70, att_rx=10
1. use RFSWITCH service to set all switches to port 1 for antenna

### sb2.orbit-lab.org
1. set usrp address to "type=x3xx,addr=192.168.40.2"
1. bring up usrp ethernet interface, set ip to 192.168.40.1/16

### sb1.orbit-lab.org
1. set usrp address to "type=b210"
1. UE_rxgain: 120
1. UE_txgain: 30
1. UE_maxpower: 0
1. eNB_att_tx: 40
1. eNB_att_rx: 0


### sb4.orbit-lab.org ===
1. set usrp address to "type=b210"
1. configure RF matrix for 60db of attenuation between eNB and UE node chosen