realistic testing of operational radio communications from ... · • interaction of em field and...
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Realistic testing of operational radio communications from and to vehicles incommunications from and to vehicles in
virtual electromagnetic environments
Over-The-Air i Vi t l
Wim Kotterman, Markus Landmann, Horst Heringklee, Rainer Perthold, Matthias Hein, Reiner Thomä Giovanni Del Galdoin a Virtual
Electromagnetic EnvironmentReiner Thomä, Giovanni Del Galdo
TU Ilmenau Institute of Information Technology
Fraunhofer Institute for Integrated Circuits
Thüringer Innovationszentrum Mobilität
IZT Innovationszentrum für Telekommunikationstechnik
1Wim Kotterman ETSI 6th WS ITS, Berlin 2014
Challenges of real-life testing C2XPropagation environment
• Multipath• Delay-, angular-, and Doppler-spread • Large-scale and small-scale effects• Interaction of EM field and antennas
Radio environment
• Variety of transmission standardsfrequencies, modulation, coding,access scheme
• Multiple users interferenceSource: CAR 2 CAR Communication Consortium
• Performance depends on dynamically changing, complex scenarios in terms of traffic and radio environment
• Multiple users, interference
• Mixture of infrastructure and ad-hoc based access• System level performance assessment • Holistic approach: including both vehicle and driver response (“driver in
the loop”)
2Wim Kotterman ETSI 6th WS ITS, Berlin 2014
the loop )
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Test Drives vs. Virtual Reality“Vi t l lit ” i t“Virtual reality” is a computer generated environment that emulates reality
• Acoustics, music and noise • Visual representation• Human interaction
Radio drive tests comprise:Radio drive tests comprise:
• Installed performance (system level test)• Driver in the loop• Realistic and live environment
Radio drive tests:
Lik l t i d t d ibl• Likely too expensive and not reproducible• Depend on existing infrastructure and existing standards• Insufficient for certification• Restrictions of ethical and legal extent
3Wim Kotterman ETSI 6th WS ITS, Berlin 2014 3
Radio drive test goes virtual
Emulating multipath, multiple users, and interference in a shielded environment
Emulation
Model of vehicular radio environment Wave field generation in anechoic chamber(stationary vehicle)
4Wim Kotterman ETSI 6th WS ITS, Berlin 2014
(stationary vehicle)
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OTAinVEEO Th Ai t ti i
EM fi ld l ti i h i h b
Over-The-Air testing inVirtual Electromagnetic Environments
• EM field emulation in anechoic chamber • System level test, installed
performance of antennas and vehicle• Controllable and reproducible• Controllable and reproducible• No interference to and from deployed
systems (shielded environment)• Testing vehicles in new prospective• Testing vehicles in new, prospective,
or foreign radio access networks• Arbitrary scenarios: ”radio crash test”/
critical interference, dynamics, ”what if”y• OTAinVEE transparent for radio
access technology• Closed-loop: dual directional
source: Fraunhofer IIS FORTE
Example: OTAinVEE set-up for LTE/LTE+
5Wim Kotterman ETSI 6th WS ITS, Berlin 2014 5
OTAinVEE: Challenges
Balance of effort: realism vs. complexity• Realistic emulation of radio wave fields (w.r.t. use of resources)• Closed-loop performance (up- and down-link, e.g. for protocol or multi-hop)• Multiuser scenarios (ad hoc!) • (Massive) Interference
Minimum requirements for emulation realism:• Dynamics of time variance incl large-scale fading (“road movie”)Dynamics of time variance, incl. large scale fading ( road movie )• Balancing RF environment complexity with test scenarios on higher layers
6Wim Kotterman ETSI 6th WS ITS, Berlin 2014 6
OTAinVEE: Balance of effort
Accurate Wave Field Synthesis (WFS)
Realism vs. complexity
Accurate Wave Field Synthesis (WFS)requires huge resources:• Any field linearly decomposed into
plane wave components
OTA antennas
Plane Wave,synthesised bysuperposition
p p• 5 m class vehicles @6 GHz and 3-D:
thousands of antenna ports• High connectivity: many
user/interference sources • One multi-input channel emulator
per antenna port: costs ~20-40 T€Cl d l ddi i ll h i• Closed-loop: additionally, the same in reception (“reciprocal” process)
Wave field synthesis by coherent superposition
Target area Primaryfields
7Wim Kotterman ETSI 6th WS ITS, Berlin 2014 7
OTAinVEE: Balance of effort
Discriminate between coherent and power/signature transmissions with
Two implementation options
Discriminate between coherent and power/signature transmissions, with different emulation strategies• Coherent
– phase of incident fields importantp p– direction of incident fields important– related to antenna performance w.r.t. MIMO, diversity– transmitted information important
• Power/signature (representation of increasing sophistication)• Power/signature (representation of increasing sophistication)– ”best bang for bucks”– in-band angular spectral density (spatially coloured noise) – system mimicking:
t l (f ) t ttemporal (frame) structuremodulation characteristics (nonsense bits allowed)
– user activity pattern, etcera
• In both cases, still scenario-specific, with multi-user influence
8Wim Kotterman ETSI 6th WS ITS, Berlin 2014 8
OTAinVEE: Balance of effort
• Devices-under-Test exceeding sweet spot size
Coherent emulation: Two-stage or hybrid OTA
Devices under Test exceeding sweet spot size• Combining synthesis with reception/transmission
through antenna patterns, in real-time• Test on bench over cables
Anechoic chamberControl room
connected to system I/O• Requirements
– antenna patterns known (not just 2D cuts)
ChannelEmulatorsDownlink
MTE x NOTA
Con
vers
ion
Up
Con
vers
ion
MTEITSTestingEquipm. DuT
2D cuts)– antennas separable: access to
connectors loading/matching– still sufficient signal processing power
Di d t
TE OTA
N OTA antennas
Channel
on sion
MITS• Disadvantages– EMC issues:
e.g. self-interference locked out– tricked out by antenna adaptivity:
t i t hi
Emulation+
AntennaEmbeddingC
onve
rsio
Up
Con
versMTEITS
TestingEquipm.
DuT
9Wim Kotterman ETSI 6th WS ITS, Berlin 2014
tuning, matching
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Control bench
OTAinVEE: Balance of effort
• In anechoic chamber
Power spectrum/signature emulation
Reflectionsand scattering
• In anechoic chamber• System and scenario dependent sophistication• Split fields into
– Communication transmissions (multi-user)
V2V
Communication transmissions (multi user)– Interference– Noise
• Discretise angular power spectrum:
Mobile commsBS
Realisticscenario
Emulatedi
Active
– No synthesis, fixed radiation directions– Multipath instead of angular spread– Hope for wide antenna patterns
• Temporal, spectral signature emulation scenario
Dynamometer, acceleration
profiles
radiators
Inactiveradiators
e po a , spect a s g atu e e u at o– Communications: transparent, with fading– Interference: depends on sophistication of
System-under-Test– Noise: spectrally and angularly coloured noise
10Wim Kotterman ETSI 6th WS ITS, Berlin 2014
Noise: spectrally and angularly coloured noise
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OTAinVEE Lab at TU IlmenauTU Ilmenau VISTAVirtual road project
2014Anechoic room
TurntableDynamometer/Dynamometer/per wheel drive
Measurements C2XChannel models C2XFhG FORTE 2 tFhG FORTE: 2-stage
2015Antenna patterns p
EmulationFhG FORTE:WFS@6GHz
11Wim Kotterman ETSI 6th WS ITS, Berlin 2014 11
Conclusions
OTAinVEE:System level test: antennas vehicle and environment:• System level test: antennas, vehicle, and environment:– Alternative to drive tests– Controllable and reproducible– No interference from and to outside world– Transparent to radio access technology– Emulation of arbitrary scenario dynamics, incl. “what if”
• Two implementations envisaged– Two-stage for accurate wave fields, but vehicle is modelled – Power/signature emulation for large DuT, but simplified wave fields g g , p
• Test scenarios– Channel dynamics (large-scale effects included)– Balanced over layers crowded when needed
12Wim Kotterman ETSI 6th WS ITS, Berlin 2014
– Balanced over layers, crowded when needed