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 )

2

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)

4

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

9

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

10

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