MtdMdlifMeasurements and Modeling of Vehicle-to … · 2012-07-02 · MtdMdlifMeasurements and Modeling of Vehicle-to-Vehicle Radio Channels ... a mathematical model for controlled

M t d M d li fMeasurements and Modeling ofVehicle-to-Vehicle Radio Channels

Johan KåredalDept. of Electrical and Information Technology

Lund University, Sweden

Radio Channel ResearchRadio Channel Research

Main objective: Understand the underlying mechanisms behind theMain objective: Understand the underlying mechanisms behind the propagation of a signal from transmitter to receiver in order to construct a mathematical model for controlled synthesis of channels

E er a e isBasic principle:

Every wave is characterizedby a number of properties:

Multipath propagation

properties: delay-time-of-arrival, Doppler ferquency etcferquency etc.

IEEE VTS Workshop on Wireless Vehicular Communications, Halmstad 2010 2 / 31

OverviewOverview

• Propagation channels– Fundamentals– Research objectives

• Initial measurements – LUND’07 campaignImportant channel charactersics– Important channel charactersics

– Development of a channel model• Follow-up measurements – DRIVEWAY’09 campaignp p g

– Application-specific scenarios– Propagation channels in intersections

• Conclusions


Cellular vs Vehicle to Vehicle PropagationCellular vs. Vehicle-to-Vehicle Propagation

• Elevated position• Scatterer-free• Static

• Ground-level position• Surrounded by scatterers• DynamicDynamic

• Ground-level position • Different frequency band• Ground-level positionGround level position• Surrounded by scatterers• Dynamic

• Many important scatterersare moving

• Coverage region not a

Ground level position• Surrounded by scatterers• Dynamic

circle around Tx• Vehicle-to-vehicle

channels are subject to f fl i


faster fluctuations

Doppler Shifts in V2V PropagationDoppler Shifts in V2V Propagation

RXTX RXTX

TX RXTX

TX

RX

RXTX RX

RXTX RXTX

RXTX RXTX

RXTX


RXTX

Research ObjectivesResearch Objectives

• Obtain a general understanding of vehicle-to-vehicle propagationchannels

U d l i h i– Underlying mechanisms– System impact– Gain from multiple-antenna systemsGain from multiple antenna systems– Antenna/channel interaction

• Build simulations models for system evaluation– Vehicle-to-vehicle propagation channels are different from

many other propagation channels


OverviewOverview





• Conclusions


Vehicle to Vehicle Channel Measurements

• TX/RX mounted on small

Vehicle-to-Vehicle Channel Measurements

Antenna• TX/RX mounted on small trucks

Antenna elements

• 4x4 MIMO measurement campaign at 5.2 GHz

Non omni

• Measurements with cars in same and opposite lanes

Non-omni-directional antenna patternspatterns


Measured Traffic EnvironmentsMeasured Traffic Environments

1 Hi h ti1. Highway section

• Wall separating directions of traveldirections of travel

• Sound abatement walls

2 Rural road2. Rural road

• Few road-side objects

Littl t ffi• Little traffic

3. Urban street

• Busy traffic

• Buildings, road signs etc.


General Observations PathlossGeneral Observations - Pathloss

Rural environment: Highway environment:

• Few scatterers contribute to signal• Always line-of-sight conditions• Two ray propagation → predictable

• Multi-path propagation• Line-of-sight sometimes obstructed• Power law dependence (P = P d - n )


• Two-ray propagation → predictable • Power law dependence (P = P0d n )

General Observations Time/DelayGeneral Observations – Time/Delay

Time-delay characteristics:Time delay characteristics:

t = 0 st = 0 2 st = 0 4 st = 0 6 st = 0 8 st = 1 st = 1 3 st = 1 5 st = 1 7 st = 1 9 st = 2 1 st = 2 3 st = 2 5 st = 2 8 st = 3 st = 3 2 st = 3 4 st = 3 6 st = 3 8 st = 4 1 st = 4 3 st = 4 5 st = 4 7 st = 4 9 st = 5 1 st = 5 3 st = 5 6 sRX t = 5 8 st = 6 st = 6 2 sLOS t = 6 4 st = 6 6 st = 6 9 st = 7 1 st = 7 3 st = 7 5 st = 7 7 st = 7 9 st = 8 1 sDiscrete comp.

Houses, road signs etc.

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Diffuse

0 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 400TX

0 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 4000 100 200 300 400

Diffuse comp.

Other vehicles

Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]Propagation distance [m]

• Rapidly varying channel• Discrete components carry significant energy and change delay bin with time


p y g gy g y• Diffuse components following LOS

General Observations Doppler/DelayGeneral Observations – Doppler/Delay

Local scattering function:

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Discrete components

Local scattering function:

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10001500500Doppler frequency [Hz]Delay [ns]














• Discrete components: small Doppler spread, but can change delay bin rapidly• Diffuse components: large delay and Doppler spread


Diffuse components: large delay and Doppler spread• Time-variant Doppler spectrum → Non-stationary conditions

Stationarity TimeStationarity-Time

Highway opposite direction Highway same direction Urban same directionHighway, opposite direction Highway, same direction Urban, same direction

23 ms 1479 ms 1412 ms

The time during which the localscattering function is ”sufficiently constant” is definedas the stationarity time


Analysis of Diffuse ContributionAnalysis of Diffuse Contribution

Scattering point along roadside

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1 ]

Doppler characteristics

Amplitude statistics of diffuse

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pler

shift

[vλ-1characteristics

of diffuse componentscan be modeled

components can be modeled using scatterers

Tap statistics following LOS

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with complex Gaussian path gains


0 50 100 150 200 250 300-200

Delay [m]

A Geometry Based Stochastic ModelA Geometry-Based Stochastic Model

DiffuseMobile Diffuse scatterers

Mobile discrete scatterers

Static discrete scatterers

Dependent on scatterersantenna pattern


Adding up all components using different antenna patterns → MIMO channels

Modeling Discrete ComponentsModeling Discrete Components

Analysis of discrete components:1. High-resolution algorithm2 T ki l ith2. Tracking algorithm

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and LOS (!) are fading

Characterization by:

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i. distance decayii. path gain as

stochastic process220 225 230 235 240 245 250 255 260

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Channel EmulationChannel Emulation

f f• Example of measured impulse response:

• Example of emulated impulse response:

DiscreteDiscrete components

• Example comparison of measured d l t d t l tiand emulated antenna correlation:

Diffuse components


Conclusions from Initial MeasurementsConclusions from Initial Measurements

We fo nd thatWe found that:• Vehicle-to-vehicle propagation channels are fundamentally different

from cellular propagation channelsp p g• Vehicle-to-vehicle propagation channels are non-stationary• A geometric-stochastic propagation channel model is suitable

…but also concluded that:• Measurements with trucks are practical but will influence the• Measurements with trucks are practical, but will influence the

measured channel (antenna height)• Measurement conduct (cars in convoy or opposite directions on

h h ) l d b fhighways etc.) is commonly used, but not representative for manyvehicle-to-vehicle applications (e.g., intersection collision avoidance)

M ti ti f f th t !


→ Motivation for further measurements!

OverviewOverview





• Conclusions


MotivationMotivation

• Vehicle-to-vehicle (V2V) communication is envisioned for applications within traffic safetyA t th li ti lli i id t hi h• Amongst those applications are collision avoidance systems, whichare expected to be useful in street intersections

• The properties of the wireless propagation channel is whatp p p p gultimately dictates system performance

• Inital V2V channel measurements typically:d ” l ” t t l t d iti– used ”regular” antenna arrays at an elevated position

– were conducted with cars driving in (a) convoy or (b) oppositedirection

Analyze the propagation channel properties for important scenarios where V2V applications are useful


Measurement Set UpMeasurement Set-Up

Vehicle-to-vehicle measurements:• Regular cars:

standard hatchback stylestandard hatchback style• Realistic antenna design:

4-element linear array of patchy pantennas integrated in rooftopradome

• Realistic antenna placement• Realistic antenna placement

Consequences:Sh d i b f• Shadowing by car roof inclination

• Shared space with other antennas (e g GPS)


antennas (e.g., GPS)

Measured ScenariosMeasured Scenarios

Identify scenarios where V2V comunications will be (particularly) useful, e.g.,

lli i id I t ti T l– collision avoidance,– emergency vehicle warning,– hazardous location notification

Intersections Tunnels

Intersections

hazardous location notification,– wrong-way driving warning,– co-operative merging assistance, Merging lanes

Merging lanes

– slow vehicle warning,– lane change assistance

Congestion

Merging lanes

Tunnels


Measurement ConductMeasurement Conduct

Measurements done whileboth cars approaching an intersection from

di l di iperpendicular directions

Four types of intersections:Four types of intersections:

AntennaAntennaelements two and threethree


Two Different Urban IntersectionsTwo Different Urban Intersections

”Narrow urban”:• Width 14-17 m (building-to-

b ildi )building)• Single lane• Parked cars along streetParked cars along street• Some traffic

”Wide urban”:Wide urban :• Width 20-43 m• Two lanes and turn lanes• Traffic lights• Busy traffic


Time Varying Power Delay ProfilesTime-Varying Power Delay Profiles

Narrow urban (Tx2-Rx2): Wide urban (Tx2-Rx2):

Componentsi i b f

Large increase in numberf t h b th

Strong componentsil bl ”l ”arriving before

line-of-sightof components when bothcars are in intersection

available ”long” before LOS


A Closer Look at Wide Urban IntersectionA Closer Look at Wide Urban Intersection

Best fit provided012345

Rx 012345

Rx 012345

6

Rx 012345

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Rx 012345

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Rx 012345

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Rx 012345

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RxBest fit providedby building left of receiver car!

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Tx

Study these pathsin more detail

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Additional propagation Drawing scattering ellipses correspondingAdditional propagationdelay of paths comparedto LOS can be deducedfrom power delay profile

Drawing scattering ellipses correspondingto this delay on a site map for each time instant where the path is visible revealsthe origin of the components


p y p g p

A Closer Look at Wide Urban cont’dA Closer Look at Wide Urban, cont’d

A high resolution algorithm isA high-resolution algorithm is used to track the time-varying contribution from each patheach path

For long durations, the twopaths contribute to half of the total signalthe total signal

Roadside buildings can provide importantpropagation paths for this type of application.However, the ”narrow urban” scenario did not


However, the narrow urban scenario did not show same results → dependence on geometry

ComparisonComparison

Define ”distance to collision”as sum of distances to intersecting point: d1+d2

LOS occurs!

”wide urban”wide urban

Few availablepropagation pathsbefore LOS

The difference (3 dB) is similar to contri-bution from buildingd1

The ”wide urban” intersection provides

gin ”wide urban”

The wide urban intersection provides the stronger signal, not due to LOS being availble earlier, but through moreavailable propagation paths!

d2


available propagation paths!

Directional EstimationDirectional Estimation

A high resolution algorithm (SAGE)A high-resolution algorithm (SAGE) allows for a refined identification of interacting objects (”scatterers”) in urban scenariosurban scenarios

Initial results show that:1. Single-reflection processes are

dominating2. Other vehicles are not “seen” in

h i h l


the propagation channels

OverviewOverview





• Conclusions


ConclusionsConclusions

• Vehicle-to-vehicle propagation channels are fundamentallydifferent from cellular channels, especially due to non-stationarity

• Channel models based on assumptions of stationarity cannot be used → a geometry-based model was found suitableg y

• Vehicle-to-vehicle propagation channels can be challenging in it ti h i t t li ti i t d d imany situations where important applications are intended, e.g., in

intersections

• The dependence of antenna placement needs further investigation


PublicationsPublications

• A. Paier, J. Kåredal, N. Czink, C. Dumard, T. Zemen, F. Tufvesson, A. Molisch, C. F. Mecklenbräuker, ”Characterization of Vehicle-to-Vehicle Radio Channels from Measurements at 5.2GHz,” Wireless Personal Communications, vol. 50, no. 1, pp. 19-29, 2009.

• J. Kåredal, F. Tufvesson, N. Czink, A. Paier, C. Dumard, T. Zemen, C. Mecklenbräuker, A. Molisch, ”A geometry-g ybased stochastic MIMO model for vehicle-to-vehicle communications,” IEEE Transactions on Wireless Communications, vol. 8, no. 7, pp. 3646-3657, 2009.

• A. Molisch, F. Tufvesson, J. Kåredal, C. F. Mecklenbräuker, ”A Survey on Vehicle-to-Vehicle PropagationChannels,” IEEE Wireless Communications, vol. 16, no. 6, pp. 12-22, 2009.J Kå d l F T f T Abb O Kl A P i L B dó A M li h ”R di h l• J. Kåredal, F. Tufvesson, T. Abbas, O. Klemp, A. Paier, L. Bernadó, A. Molisch, ”Radio channel measurements at street intersections for vehicle-to-vehicle applications,” Proc. IEEE Vehicular Technology Conference (VTC2010-spring), Taipei, Taiwan, pp. 1-5, May 16-19, 2010.

• A. Paier, L. Bernadó, J. Kåredal, O. Klemp, A. Kwoczek, ”Overview of vehicle-to-vehicle radio channelmeasurements for collision avoidance applications ” Proc IEEE Vehicular Technology Conference (VTC2010-measurements for collision avoidance applications, Proc. IEEE Vehicular Technology Conference (VTC2010spring), Taipei, Taiwan, pp. 1-5, May 16-19, 2010.

• A. Molisch, F. Tufvesson, J. Kåredal, C. Mecklenbräuker, ”Propagation aspects of vehicle-to-vehiclecommunications - an overview,” Proc. IEEE Radio and Wirless Symposium (RWS), San Diego, CA, USA, pp. 179-182, Jan. 18-22, 2009.

• J. Kåredal, F. Tufvesson, N. Czink, A. Paier, C. Dumard, T. Zemen, C. Mecklenbräuker, A. Molisch, ”Measurement-based modeling of vehicle-to-vehicle MIMO channels,” Proc. IEEE International Conference on Communications (ICC), Dresden, Germany, June 14-18, 2009.

IEEE VTS Workshop on Wireless Vehicular Communications, Halmstad 2010

Publications (cont’d)Publications (cont’d)

• A. Paier, T. Zemen, J. Kåredal, N. Czink, C. Dumard, F. Tufvesson, C. Mecklenbräuker, A. Molisch, ”Spatial diversity and spatial correlation evaluation of measured vehicle-to-vehicle radio channels at 5.2 GHz,” Proc. IEEE Digital Signal Processing Workshop/Signal Processing Education Workshop (DSP/SPE), pp. 326-330, Jan 1-4, 2009.

• L. Bernadó, T. Zemen, A. Paier, J. Kåredal, B. Fleury, ”Parametrization of the local scattering function estimatorfor vehicular-to-vehicular channels,” Proc. IEEE Vehicular Technology Conference (VTC2009-fall), Anchorage, AK, USA, pp. 1-5, Sept. 20-23, 2009.

• A. Paier, T. Zemen, L. Bernado, G. Matz, J. Kåredal, N. Czink, C. Dumard, F. Tufvesson, A. Molisch, C. Mecklenbräuker ”Non WSSUS vehicular channel characterization in highway and urban scenarios at 5 2 GHzMecklenbräuker, Non-WSSUS vehicular channel characterization in highway and urban scenarios at 5.2 GHz using the local scattering function,” Proc. International Workshop on Smart Antennas (WSA), pp. 9-15, 2008.

• L. Bernadó, T. Zemen, A. Paier, G. Matz, J. Kåredal, N. Czink, C. Dumard, F. Tufvesson, M. Hagenauer, A. Molisch, C. F. Mecklenbräuker, ”Non-WSSUS Vehicular Channel Characterization at 5.2 GHz - SpectralDivergence and Time-Variant Coherence Parameters,” Proc. URSI General Assembly, 2008.g , y,

• A. Paier, J. Kåredal, N. Czink, H. Hofstetter, C. Dumard, T. Zemen, F. Tufvesson, C. Mecklenbräuker, A. Molisch, ”First results from car-to-car and car-to-infrastructure radio channel measurements at 5.2GHz,” Proc. IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), Athens, Greece, pp. 1-5, Sept. 3-7, 2007.

d l k f d f l h kl b k• A. Paier, J. Kåredal, N. Czink, H. Hofstetter, C. Dumard, T. Zemen, F. Tufvesson, A. Molisch, C. Mecklenbräuker, ”Car-to-car radio channel measurements at 5 GHz: Pathloss, power-delay profile, and delay-Doppler spectrum,”Proc. IEEE International Symposium on Wireless Communication Systems (ISWCS), Trondheim, Norway, pp. 224-228, Oct. 17-19, 2007.


Thank you!Thank you!


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MtdMdlifMeasurements and Modeling of Vehicle-to … · 2012-07-02 · MtdMdlifMeasurements and Modeling of Vehicle-to-Vehicle Radio Channels ... a mathematical model for controlled