OpenAirInterface LTE

Notes on a working OAI LTE project using a Samsung Galaxy S4 Mini, mainly pointers to build guides used and summary of obstacles encountered.

Result: Data transmission with an off the shelf cell phone up to 8Mbps (iperf) with very limited range using two antenna for tx and rx (proper duplexer project pending). That is, the phone must be experimentally positioned a less than a half meter from the LimeSDR and moved around until a good constellation display is found for best results.

Guides for installation:
[1]Main OAI page for setup with usrp device
[2]open-cells LimeSDR setup
[3]Recent (8/22/2017) all-in-one box build of OAI eNodeB and EPC components.

Hardware used:
Dell OptiPlex 9010 - quad core i7-3770 CPU @ 3.40GHz with USB3 support and hyperthreading turned off per OAI [4]recommendations
Bash script to turn off hyperthreading (/usr/local/bin/set-hyper-threading) from discussion [5].
Ubuntu 16.04 LTS Xenial - with low latency kernel

root@DellOptiPlex9010:~# uname -a
Linux DellOptiPlex9010 4.13.0-36-lowlatency #40~16.04.1-Ubuntu SMP PREEMPT Sat Feb 17 00:18:34 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

The latest available lowlatency kernel can be found with a search for the kernel module gpt.ko that will be needed to run the gateway module

# apt-file search gtp.ko  | grep lowlatency
linux-image-4.13.0-36-lowlatency: /lib/modules/4.13.0-36-lowlatency/kernel/drivers/net/gtp.ko
# apt install linux-image-4.13.0-36-lowlatency

Beware if that particular kernel is no longer the primary boot image in grub.conf after an apt upgrate - or manually pick the kernel on startup, or change grub.conf to boot that particular image [6] - example /etc/default/grub:

GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 4.13.0-36-lowlatency"

So now we have a platform with i7-3770, no hyperthreading and lowlatency ready for OAI LTE.
And off we go:

~/src/oai$ git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git     Near 200MB 
cd  openairinterface5g
~/src/oai/openairinterface5g$ source oaienv
~/src/oai/openairinterface5g$ ./build_oai -I --install-optional-packages          <-- left this running in a screen, installs a bunch of pkgs -- hope it does not break my 2G stuff!

---

later ----

came home to find a question in the screen, about allowing non-root users to run wireshark packet capture - choose the not-recommended 'yes'
then fail on python ssl - had to fix with

python -m easy_install --upgrade pyOpenSSL

from [7] re-run ./build_oai above and completed successfully
Next run

~/src/oai/openairinterface5g$ source oaienv     Since I exited the screen with env set
~/src/oai/openairinterface5g$ ./cmake_targets/build_oai --eNB -w LMSSDR -c -C -x
< ... >
-- Build files have been written to: /home/chuck/src/oai/openairinterface5g/cmake_targets/lte_build_oai/build
Compiling lte-softmodem
Log file for compilation has been written to: /home/chuck/src/oai/openairinterface5g/cmake_targets/log/lte-softmodem.Rel14.txt
lte-softmodem compiled
Log file for compilation has been written to: /home/chuck/src/oai/openairinterface5g/cmake_targets/log/oai_lmssdrdevif.Rel14.txt
oai_lmssdrdevif compiled
liboai_device.so is linked to LMSSDR device library
10. Bypassing the Tests ...

More on build options:
A fellow in the discourse how-to-install-limesdr-on-openinterface-enodeb uses: ./build_oai -I --eNB -x -w LMSSDR Add -x to enable xforms (soft scope), -w hardware EXMIMO, USRP, BLADERF, ETHERNET, LMSSDR, None (Default) --eNB Makes the LTE softmodem -I Installs required packages such as LibXML, asn1.1 compiler, freediameter, ... <-- I did this seperately above

Above command had -c clean Erase all files to make a rebuild from start
-C clean-all Erase all files made by previous compilations, installations

The open-cells limesdr-installation used

./cmake_targets/build_oai -c -w LMSSDR --eNB --UE

for -c clean, -w hardware, --eNB and also --UE Makes the UE specific parts (ue_ip, usim, nvram) from the given configuration file -- default given config file is /home/chuck/src/oai/openairinterface5g/openair3/NAS/TOOLS/ue_eurecom_test_sfr.conf
What you end up with after that build is:

 targets/bin/liboai_device.so ->  targets/bin/liboai_lmssdrdevif.so.Rel14
 targets/bin/liboai_lmssdrdevif.so.Rel14
 targets/bin/lte-softmodem.Rel14

and any custom LimeSDR tweaks like setting external clock reference or printing confirmation of antenna uses go in

targets/ARCH/LMSSDR/USERSPACE/LIB/lms_lib.cpp

plus it's just fun to read in itself with /usr/local/include/lime/LimeSuite.h open in another term. Of course rebuild lte-softmodem after any tweaks or experiments.

Do Download and Patch EPC from [8]
Install 3rd party software for EPC

source oaienv
cd scripts
./build_hss -i
Installing mysql -  root user password:  Pa$$word            <intentionally including example password> 
installs freeDiameter - auth like RADIUS  https://en.wikipedia.org/wiki/Diameter_(protocol)
installs apache, php    -- for phpMyAdmin   pick apache
Configure database for phpmyadmin with dbconfig-common? Yes
phpmyadmin password:   Pa$$word

That was to install all the prereqs for hss - it will be built later, meanwhile prepare for

 $ ./build_mme -i
freeDiameter - no
asn1c rev - no
libgtpnl - yes      hope this does not conflict with osmosgsn, ggsn  GTP
wireshark - done previously (non-root CAN run it)


 $ ./build_spgw -i
libftpnl - no this time

Next, actually compile them - just up-arrow and delete the -i

./build_hss
'/home/chuck/src/oai/openair-cn/build/hss/build/oai_hss' -> '/usr/local/bin/oai_hss'
oai_hss installed
$ ls /usr/local/bin/oai_hss
/usr/local/bin/oai_hss

./build_mme
mme compiled
'/home/chuck/src/oai/openair-cn/build/mme/build/mme' -> '/usr/local/bin/mme'
mme installed
auth_request compiled
'/home/chuck/src/oai/openair-cn/build/mme/build/auth_request' -> '/usr/local/bin/auth_request'
auth_request installed

./build_spgw
spgw compiled
'/home/chuck/src/oai/openair-cn/build/spgw/build/spgw' -> '/usr/local/bin/spgw'
spgw installed

We are going to use this configuration:

HSS is on localhost: 127.0.0.1
eNB is on 127.0.0.10
MME is on 127.0.0.20
SPGW is on 127.0.0.30

I learned something about loopback lo interface here - you already have all 255^3 addresses available ready to use!

# ping 127.90.90.90
PING 127.90.90.90 (127.90.90.90) 56(84) bytes of data.
64 bytes from 127.90.90.90: icmp_seq=1 ttl=64 time=0.025 ms
64 bytes from 127.90.90.90: icmp_seq=2 ttl=64 time=0.032 ms

So backup and edit the config file openairinterface5g/targets/PROJECTS/GENERIC-LTE-EPC/CONF/enb.band7.tm1.25PRB.lmssdr.conf to use this:

mme_ip_address = ( { ipv4 = "127.0.0.20";          -- rest the same

NETWORK_INTERFACES : 
     ENB_INTERFACE_NAME_FOR_S1_MME = "lo";
     ENB_IPV4_ADDRESS_FOR_S1_MME = "127.0.0.10/8";

     ENB_INTERFACE_NAME_FOR_S1U = "lo";
     ENB_IPV4_ADDRESS_FOR_S1U = "127.0.0.10/8";

Here is a good discussion of the nodes and interfaces (S1-MME, S1-U, etc) to help visualize the interconnects [9]
Install This Configuration for EPC in home ~ This uses the package d/l from [10]

sudo mkdir -p /usr/local/etc/oai
sudo cp -rp ~/opencells-mods/config_epc/* /usr/local/etc/oai

cd src/oai/openair-cn; source oaienv; cd scripts
./check_hss_s6a_certificate /usr/local/etc/oai/freeDiameter hss.OpenAir5G.Alliance
HSS S6A: Did not find valid certificate in /usr/local/etc/oai/freeDiameter
HSS S6A: generating new certificate in /usr/local/etc/oai/freeDiameter...
Creating HSS certificate for user 'hss.OpenAir5G.Alliance'
...
Certificate is to be certified until Feb 24 18:51:15 2019 GMT (365 days)

Write out database with 1 new entries
Data Base Updated
/home/chuck/src/oai/openair-cn/scripts
HSS S6A: Found valid certificate in /usr/local/etc/oai/freeDiameter

So that cert is good for ONE YEAR Warning if still using it then

# less /usr/local/etc/oai/freeDiameter/hss.cert.pem
         Validity
            Not Before: Feb 24 18:51:15 2018 GMT
            '''Not After : Feb 24 18:51:15 2019''' GMT

./check_mme_s6a_certificate /usr/local/etc/oai/freeDiameter mme.OpenAir5G.Alliance
File /usr/local/etc/oai/freeDiameter/mme.cert.pem not found
MME S6A: Did not find valid certificate in /usr/local/etc/oai/freeDiameter
MME S6A: generating new certificate in /usr/local/etc/oai/freeDiameter...
Creating MME certificate for user 'mme.OpenAir5G.Alliance'
...
Certificate is to be certified until Feb 24 18:53:02 2019 GMT (365 days)

Write out database with 1 new entries
Data Base Updated
/home/chuck/src/oai/openair-cn/scripts
MME S6A: Found valid certificate in /usr/local/etc/oai/freeDiameter

Then in /usr/local/etc/oai/spgw.conf change SGI to YOUR Internet facing interface:

PGW_INTERFACE_NAME_FOR_SGI = "enp0s31f6";  
to 
PGW_INTERFACE_NAME_FOR_SGI = "eno1";

This is already set:
PGW_MASQUERADE_SGI = "yes";

Warning: the config file /usr/local/etc/oai/hss.conf contains:

## HSS options
#OPERATOR_key = "1006020f0a478bf6b699f15c062e42b3"; # OP key matching your database
#OPERATOR_key = "11111111111111111111111111111111"; # OP key matching your database

The OPERATOR_key or 'OP' is an important part of the UE authentication, along with the key Ki and OPc. In fact, when the hss starts up is recalculates all the subscribers OPc from their key and this OPERATOR_key so they have to match what you use to write the OPc to the SIM card later. I picked a random OP (openssl rand -hex 16) and calculated the OPc from that with auchss.py [11].

Next discussion about MCC,MNC and headache getting an ebay special Galaxy S4Mini GT-I9195 [12] working on LTE with Sysmocom SIMS