OpenAirInterface 5G Training
Florian Kaltenberger & Raymond Knopp
Newcom# Summer School on Waveforms and
Network Architectures for the IoT in 5G
15.9.2015, Eurecom, France
Outline
 OpenAirInterface Overview
– Features
– Use cases
– The OpenAirInterface 5G Software Alliance
 OpenAirInterface Software Architecture
– Signal acquisition and transmission
– Functional blocks and Interfaces
– Some example procedures and data flows
 Lab sessions
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Scenario
Installation
Run eNB, connect UE, run iperf to measure TP
Analyze the output of logs, scope, and VCD plots
Analyze the spectrum usage using spectrum analyzer
Modify scheduler
Transmit secondary waveform
Measure TP again
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OPENAIRINTERFACE
OVERVIEW
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What is Openairinterface?
 Open-source software-based implementation of 4G LTE (Rel 10)
– Spanning the full protocol stack of 3GPP standard
E-UTRAN (eNB, partial UE)
EPC (MME, S+P-GW, HSS)
– Realtime RF and scalable emulation platforms
– Targets EURECOM and National Instruments HW platforms (others in
development)
 Objectives
– Bring academia closer to complex real-world systems
– Open-source tools to ensure a common R&D and prototyping framework for
rapid proof-of-concept designs
 Other use cases
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Interoperability with 3rd party components (UE, eNB, EPC)
Matlab/Octave tools for non real-time experimentation
Real-time channel sounding (EMOS)
802.11p Modem
Unitary simulations
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Use cases of OAI I
 Classical 3GPP setup:
– OAI EPC + OAI eNB <--> COTS UE
– Commercial/3rd party EPC + OAI eNB <-->COTS UE
– OAI EPC + Commercial/3rd party eNB <--> COTS UE
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Use cases of OAI II
 Non-3GPP setup:
– OAI eNB <--> OAI UE
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Use cases of OAI III
 Simulation/Emulation (oaisim)
– OAI eNB <--> OAI UE
– OAI EPC + OAI eNB <--> OAI UE
– Comercial/3rd party EPC + OAI eNB <--> OAI UE
 Unitary simulators
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DLSCH simulator dlsim
ULSCH simulator ulsim
PUCCH simulator pucchsim
PRACH simulator prachsim
PDCCH simulator pdcchsim
PBCH simulator pbchsim
eMBMS simulator mbmssim
 Other uses
– EMOS (real-time channel sounding)
– octave (simple experimentation)
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OpenAirInterface Features
IP packets
AT commands
MME Application
Linux IP
stack
NAS
RRC
eNB Application
RRC
S1-MME
NAS
X2AP
S1-U
S1-MME
S+P-GW Application
S11 Abstraction
S6a/Diameter
GTP-U
PDCP
PDCP
RLC
RLC
IP
IP
MAC
MAC
Ethernet
Ethernet
PHY
PHY
UEs
SCTP
UDP
eNBs
S1-U
SCTP
UDP
MME + S+P-GW
3GPP layers
Linux stack
Control Plane
Data Plane, IP packet
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Implements 4G LTE Rel10 Access Stratum (eNB & UE)
and EPC (MME, S+P-GW, HSS)
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All the stack (incl. PHY) runs entirely on a PC in real-time operating system (RTAI,
Xenomai, low-latency kernel)
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Works with ExpressMIMO (Eurecom) and USRP (Ettus/National Instruments)
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More detailed feature list here:
https://twiki.eurecom.fr/twiki/bin/view/OpenAirInterface/OpenAirFeatures
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Key Ingredients (How does OAI work)
1. Real-time extensions to Linux OS
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Today we rely on the lowlatency kernel provided by Ubuntu
(since Ubuntu 14.04)
In earlier Ubuntu versions RTAI was used
2. Real-time data acquisition to/from PC
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ExpressMIMO uses DMA to transfer signals in and out of PC
memory without hogging CPU -> very efficient
USRP transfers data over USB and therefore requires extra
CPU time for (de-)packetization of signals
3. Highly optimized DSP routines running on Intel GPP
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Exploiting vector processing (SIMD)
64-bit MMX  128-bit SSE2/3/4  256-bit AVX2
OAI features fastest FFT and Turbo decoder of its kind
4. Multi-threaded parallel processing
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Collaborative Web Tools
 www.openairinterface.org
– New website will soon be released
 OpenAirInterface SVN Repositories
– Core development is available through our SVN repository
http://svn.eurecom.fr/openair4G/trunk
– In transition to gitlab:
https://gitlab.eurecom.fr/oai/openairinterface5g
 OpenAirInterface TWIKI
– A TWIKI site for quick access by partners to our development via a
collaborative HOW-TO
– https://twiki.eurecom.fr/twiki/bin/view/OpenAirInterface/WebHome
 Mailing list
– openair4G-devel@lists.eurecom.fr
– Anyone can subscribe (send an email to sympa@lists.eurecom.fr
with the subject "subscribe openair4G-devel firstname lastname“)
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5G
THE OPENAIRINTERFACE 5G
SOFTWARE ALLIANCE
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Next Steps for OAI
 Ensure a path 4G5G through open-source policy
– Work with new carrier candidates now, short packet low-latency
carriers, contention-based access
– VRAN, MEC architectures
– Rapidly-deployable EPC/eNB (with LTE or other backhaul)
 Become a reference implementation of Rel 13/14  5G
 Serious contributors from outside Eurecom
 “ready to use” for anybody on commodity hardware (PCs
+ National Instruments)
 More global adoption for innovation and research
(Vendor labs, University Labs, etc.)  common tool
between industrial and academic research
 Business adoption in test market (Keysight)
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The OpenAirInterface Software Alliance
 Cellular systems are expected to converge from a
proprietary and expensive HW/SW platforms
towards an open SW platforms over commodity HW
– Happened already for cloud service
– Happened already for handsets
– Happened already for 2G
 To foster the innovation in wireless world, there is a
need for an open cellular ecosystem for 4G towards
5G
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Goals
 Make trusted environment
– Contributors and users need to secure themselves
– Clear open source rules
– Any individual person or non-profit organization can become a
member for free
– Membership conditions for companies
 Increase quality & simplify access
– Simple and well described binary build procedures for all the
LTE components
– Friendly to various RF systems (RRH, SmallCell, etc.)
– Anybody can build a fully open-source 4G network comprising a
couple of eNBs + EPC for less than 10K€ and 1 human week of
effort
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Industrial Users
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Alcatel-Lucent Bell Labs (Paris, New Jersey, Stuttgart)
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ChinaMobile CRAN Project (Beijing)
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Support for porting OAI software to Ettus USRP platforms (B210, X310)
Roadmap for integration on PXIe high-end industrial platforms
Air-Lynx (SME, Paris)
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Building demonstrator with OAI software for CloudRAN proof-of-concept, live real-time
deployment, 20 MHz TD-LTE
OAI software on commodity computing equipmen t (IBM x86 servers) + commercial remote
radio-heads
Keysight China (ex Agilent): interop testing for China Mobile CRAN
IBM China : parallelization architectures for China Mobile CRAN
National Instruments / Ettus Research
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Running OAI systems (OAI eNB interconnected with ALU in-house EPC development)
Contributions to core access-stratum software
Integration with in-house CPRI-based solutions and commercial RRH
VRAN Architectures
5G-waveforms (soon)
Rapidly (and less rapidly)-deployable eNB/EPC
 Currently evaluating EURECOM HW and OAI eNB/EPC/UE for public-safety
applications
Software has been analyzed independently by Intel for maturity in
CloudRAN context.
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Current status
 “Fonds de dotation” officially created
 Ongoing discussions with first round of strategic
members
 First official board meeting expected in autumn
 License switch from GPLv3 to a “modified Apache”
licensed ongoing
– Will allow non-contaminating interfacing with proprietary HW and
SW
– Will allow contributions from industry that are patented
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OPENAIRINTERFACE
HARDWARE AND SOFTWARE
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Hardware Targets for Openair4G
 ExpressMIMO2
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Eurecom board, designed and maintained by EURECOM
1.5/5/10/20 MHz, FDD/TDD
4 channels (4x4 MIMO or 4 SISO Component Carriers)
Total aggregate bandwidth: full duplex 64Msps
(Corresponds to 4x5MHz, 2x10MHz, or 1x 20MHz full duplex)
 USRP B210/X300
– Commercial Ettus/National Instruments boards
 Platforms under development
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PXIe (National Instruments)
Nutaq
Novena + Myriad RF (Lime Microsystems)
Blade RF (nuand)
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Express MIMO 2
RF RX
(4 way)
RF TX
(4 way)
PCI Express
(1 or 4 way)
Spartan 6 LX150T
12V from ATX power supply
4xLMS6002D RF ASICs
GPIO for external RF control
250 MHz – 3.8 GHz
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Express MIMO 2
• Integrated baseband/RF PCI Express board for x86based software defined radio
• Xilinx Spartan 6 FPGA
• 4 RF chains based on LIME LMS6002D
Semiconductor zero-IF RF chipsets
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Carrier frequencies: 300 MHz – 3.8 GHz
Bandwidth: 20MHz
FDD or TDD operation
~10 dBm output power
LTE RF compliance (UE, small-cell eNB)
• Status:
• more than 60 cards currently fabricated
• used by many research institutes (academic and industrial)
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USRP B210
 Designed by ETTUS (now part of NI)
 Analog Devices AD9361 RFIC Dual Channel
Transceiver (70 MHz - 6GHz)
 Full duplex, MIMO (2 Tx & 2 Rx) operation with up to
56 MHz of real-time bandwidth (61.44MS/s
quadrature)
– Slightly less in our experiments
 Data acquisition over USB3
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Comparison
USRP B210
ExpressMIMO2
Data acquisition
USB: requires extra
processing power
PCI using DMA: no
overhead for CPU
MIMO and bandwidth
capabilities
2x1 MIMO 20MHz or
2x2 MIMO 10MHz
4x4 MIMO 5 MHz, 2x2
MIMO 10Mhz, SISO 20MHz
RF performance
More sophisticated RF
cleanup
Simple RF calibration
Frequency range
70MHz – 6GHz
300 MHz – 3.8GHz
Price
€1,130.00 EUR
~€2,000.00 EUR
Duplexing
FDD
FDD or TDD
Output power
10dBm
0dBm @ 2.6GHz
10dBm @ 700MHz
Noise figure
<8dB
10-15dB
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OAI software architecture
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L1/L2 block
 OAI follows 3GPP LTE architecture
– Good knowledge of LTE is prerequisite to understand OAI
 Each block has its own data structure and functions
 Interfaces between most blocks are implemented as function
calls
 Following interfaces are
implemented using the Intertask
Interface (ITTI) framework
– RRC ↔ PDCP,
– RRC ↔ S1AP,
– PDCP ↔ S1AP
 L1/L2 thread instantiated
multiple times
– For each TX/RX subframe
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Master thread architecture (ExpressMIMO)
ExpressMIMO
(LEON)
targets/ARCH/EXMIMO/
DEFS/pcie_interface.h
Kernel
Space
PCIexpress
lte-softmodem.c
Linux driver
(openair_rf.ko)
targets/ARCH/EXMIMO/DRIVER/eurecom
User Space
L1/L2 thread 0
Master eNB
thread
(synchronization)
C API
targets/ARCH/EXMIMO/
USERSPACE/LIB
Using real-time Linux
extension (RTAI, Xenomai,
lowlatency kernel)
Octave
API
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L1/L2 thread N-1
Octave
targets/ARCH/EXMIMO/USERSPACE/OCTAVE
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Master thread architecture (USRP)
USRP
lte-softmodem.c
User Space
L1/L2 thread 0
USB
Master eNB
thread
(synchronization)
C API
UHD
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targets/ARCH/USRP/
USERSPACE/LIB
Using real-time Linux
extension (RTAI, Xenomai,
lowlatency kernel)
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L1/L2 thread N-1
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Example of real-time execution
 Include vcd plot here
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4G/5G co-existance experiments
LAB SESSION
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Lab Scenario and Goal
Experimentally study the impact of 5G waveforms on
legacy 4G systems (replicating work in [1])
eNB1
Inter-eNB
interference
eNB2
5G TDD
DL: OFDM
UL: GFDM/
UFMC
LTE FDD
DL: OFDMA
UL: SC-FDMA
Frequency 1
Frequency 2
UE1
UE1
Co-channel
interference
reduction
UEx
Uses spectrum holes
in UL (through sensing
or pre-allocated)
Kaltenberger, F.; Knopp, R.; Danneberg, M. & Festag, A.
Experimental Analysis and Simulative Validation of Dynamic Spectrum Access
for Coexistence of 4G and Future 5G Systems
European Conference on Networks and Communications (EuCnC 2015), 2015
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Lab Setup (option 1)
4G system: OpenAirInterface software radio and USRP
5G system: emulated using a signal generator
eNB+EPC
(OAI)
eNB2
Spectrum
Analyzer
5G TDD
DL: OFDM
UL: GFDM/
UFMC
LTE FDD
DL: OFDMA
UL: SC-FDMA
UEx
Signal
generator
Frequency 1
Frequency 2
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Lab Setup (option 2)
4G system: OpenAirInterface software radio and USRP
5G system: emulated using a signal generator
eNB+EPC
(OAI)
eNB2
Spectrum
Analyzer
5G TDD
DL: OFDM
UL: GFDM/
UFMC
LTE FDD
DL: OFDMA
UL: SC-FDMA
5G UE
(OAI)
Frequency 1
Frequency 2
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Outline
 OpenAirInterface Overview
– Features
– Use cases
– The OpenAirInterface 5G Software Alliance
 OpenAirInterface Software Architecture
– Signal acquisition and transmission
– Functional blocks and Interfaces
– Some example procedures and data flows
 Lab sessions
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Scenario, setup and goals
Installation of OpenAirInterface
Run eNB, connect UE, run iperf to measure throughput
Analyze the output of logs, scope, and VCD plots
Analyze the spectrum usage using spectrum analyzer
Analyze and modify eNB scheduler
Generate and transmit secondary waveform
Measure impact of secondary waveform on throughput of primary system
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Useful information
 Lab PC
– login = computer name
– Password = “linux”
 If not already installed in ~/openairinterface5G
– Get source from our gitlab server as described in
https://twiki.eurecom.fr/twiki/bin/view/OpenAirInterface/GetSourc
es
 Switch to branch and update
– cd openairinterface5g
– git checkout feature-23-ufmc
– git pull
– This branch is the same as the master but with some additional
(but unfinished) features for UFMC
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OpenAirInterface5G directories
 cmake_targets
– New directory for building all the targets
– Contains “mother” build_oai script
 targets
– Hardware specific code (drivers, tools, etc)
– lte-softmodem, oaisim
 openair1
– Basic DSP routines for implementing subset of LTE specifications under
x86 (36.211, 36.212, 36.213 3GPP specifications)
– Channel simulation, sounding and PHY abstraction software,
 openair2
– MAC/RLC/PDCP/RRC
 openair3
– Pretty much unused
 openair-cn
– EPC related parts of the eNB: S1AP, X2AP
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Compiling and running
 Initialize environment variables
– cd openairinterface5g
– source oaienv
 Compile lte-softmodem
– cd cmake_targets
– ./build_oai –w USRP –-eNB –x -V
 This creates
– ~/openairinterface5g/targets/bin/lte-softmodem.Rel10
 Configuration files
– targets/PROJECTS/GENERIC-LTE-EPC/CONF/
– Open enb.band7.tm1.50PRB.usrpb210.conf and change
o downlink_frequency=2660000000
o mme_ip_address=192.168.12.171
o S1-MME and S1-U interfaces should be the ones of your PC
 Run using
– sudo ./lte-softmodem.Rel10 –O <file.conf> -d –V
 Start the UE!
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Debug tools
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Spectrum Analyzer (UL and DL)
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Logs
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Analyze real-time behavior
gtkwave -a ~/openairinterface5g/targets/RT/USER/eNB_usrp.gtk
Wireshark
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eNB measurements (noise, signal power, etc)
UE feedback (CQI, etc.)
UL and DL HARQ statistics
VCD file
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signals in time and frequency domain
Constellation plots of PUSCH, PUCCH
Stats window
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Verbosity can be adjusted in config file
Shows L2/L3 events
PHY scope
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Shows RF performance and signal integrity
To analyze messages over S1 interface
Can also analyze MAC, RLC, PDCP, RRC if enables (see twiki for details)
Iperf/speedtest
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Shows throughout for UDP and IP
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Back to our scenario…
 Transmit secondary waveform in unused UL
resources
 Make sure the scheduler does not schedule them
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The OAI UL scheduler
 Check function schedule_ulsch_rnti in file
openair2/LAYER2/MAC/eNB_scheduler_ulsch.c
– Scheduler will always start scheduling at RB1 (RB0 and RB24
are reserved for PUCCH)
– Scheduler can only schedule N = 2a3b5c RBs per UE
–  for 5MHz: Nmax = 20; for 10MHz: Nmax = 48
–  for 5MHz, RBs 21,22,23 are free as long as there is only 1 UE
connected
–  for 10MHz, we need to reduce Nmax to 45 to keep RBs
46,47,48 free
–  modify line 821 of eNB_scheduler_ulsch.c accordingly
–  use this space for secondary waveform
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Secondary waveforms
 OFDM, GFDM:
– may be generated with GFDMlib provided by TU-Dresden [1]
 SCFDMA, UFMC:
– may be generated with OpenAirInterface, branch feature-23ufmc
– UFMC is still in a very early development and only signal
generation will work
– Signals can be generated either offline with ufmcsim or in realtime with lte-softmodem
– Folder also contains tool to convert to file for signal generator
(mat2wv)
– Build ufmcsim using ./build_oai --phy_simulators
– Run using ./ufmcsim -a -s 12 -n 1 -m 9 -B 50 -r 3 -f 0 -u
[1] https://cloudstore.zih.tu-dresden.de/public.php?service=files&t=4073588ff321c26cabf8137c6bc9a61a
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First experiment: signal generator
 For the first experiment we will use pre-generated
waveforms
– Can be downloaded from http://www.eurecom.fr/~kaltenbe/5glab
– Source can be found at
https://gitlab.eurecom.fr/florian.kaltenberger/5glab
 Load the waveforms in the signal generator
 Run a speedtest (or similar) on the UE
 Adjust signal power until degradation can be seen
 Take screenshots of the UL spectrum
 Measure throughput as a function of TX power of
secondary waveform
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Second experiment: Use OAI UE
 Compile lte-softmodem without S1 interface
– full integration with UE NAS not yet available
– ./build_oai –w USRP --eNB –x -V --noS1
 This creates
– targets/bin/lte-softmodem-nos1.Rel10
 UE is also launched using lte-softmodem
– . init_nas_nos1 UE
– ./lte-softmodem-nos1-Rel10 –U –C 2660000000
-r50 -d -V --ue-scan-carrier --ue-txgain 90
--ue-rxgain 110 --no-L2-connect
– This will make the UE synchronize to the eNB but UE will not try
to connect
– Add option -u to make the UE transmit UFMC signal
 Repeat the same procedure as in experiment 1!
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