vehicular networks â€“ quo veheris?

Vehicular Networks – Quo Veheris?Thoughts on the past, present and future of

vehicle-to-X communication

Hannes Hartenstein(with M. Killat, F. Schmidt-Eisenlohr, M. Torrent-Moreno)University of Karlsruhe, Karlsruhe Institute of Technology

Karlsruhe, [email protected]

Hannes Hartenstein 2Keynote at Mobiquitous/ISVCS, Dublin, Ireland, July 24, 2008

Goals of vehicle-to-X communication

Active safety

Traffic efficiency

Environmental friendliness


Active safety: examples

Emergency electronic brake lights

Intersection collision warning


Traffic efficiency: examples

Enhanced route guidance and navigation

Green light optimal speed advisory

Discovery of free parking places


Environmental friendliness (cost aspects): “examples”

Bloomberg:

NYMEX CRUDE FUTURE

July 18, 2008

$128.88

2006


Outline of this talk

Assessing the current state-of-the-art in vehicle-to-X communication

Traffic telematics today: public transport, road operatorsStatus quo of vehicle-to-X system design

Two „grand challenges“ of vehicle-to-X communicationScalability: radio channel congestion controlImpact assessment of vehicle-to-X communication

A look ahead Field operational testsCooperative systems


Traffic telematics today: public transportation

© INIT AG, Karlsruhe

Buses, light railwaystalk to control center,

stations, traffic signals,each other, passengers

Data exchanged for operation and management,

passenger information

July 09, 2008 Dublin Bus decided for an

advanced ITS system from INIT

State-of-the-art – Scalability – Impact – Look ahead


Traffic telematics today: a road operators view

© Dipl.-Ing. Manfred Harrer



Traffic telematics today: the concept of V2X

Vehicle-to-X communicationResearch since the 1980sLast 10 years: gained momentum with availability of low-cost GPS receivers and wireless local area network transceivers

“Disruptive idea”: equip every vehicle with a radio communication system for direct vehicle-to-vehicle and vehicle-to-roadside communication

Various issues have been addressedSpectrum allocationCommunication protocolsApplicationsDeployment scenario, standardization

We briefly review someachievements



Non-exhaustive overview on past and recent activities



Spectrum allocation in the US and in Japan

Japan: 5.770-5.850 GHz dedicated for ITSDecember 2007: 715-725 MHz for inter-vehicle communication system

Trend towards 700 MHz channel?Side note: Bosch was proposing a “radio warning system” in the 868 MHz band in the year 2000

FrequencyGHz5.850 5.870 5.880 5.890 5.900 5.910 5.920

Control and safetySafety-of-live High power public safety

5.860

United States: allocation of 75 MHz in 1999 (same for Canada and Mexico)



Spectrum allocation in Europe

ECC Decision of 14 March 2008on the harmonised use of the 5875-5925 MHz

frequency band for Intelligent Transport Systems (ITS)

See also:Frequency Allocation, D. Seeberger,

Daimler AGhttp://www.network-on-wheels.de/downloads/final-workshop



DIFS DIFS

Contentionphase

Busy

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A A wantswants to to transmittransmit

C C wantswants to to transmittransmit

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Choose arandom waiting time

i in {0,…,CW}

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Protocol architecture and specifications (1)

IEEE 802.11p currently standardized

Derivative of OFDM-based 802.11a




PHY/MAC: IEEE 802.11p

Multichannel: IEEE 1609.4

Networking Services: IEEE 1609.3

Resource Manager: IEEE 1609.1 SecurityIEEE 1609.2

IEEE WAVE trial use standards

WAVE PHY

WAVE MAC

LLC

IPv6

UDP/TCPWSMP

Multi-ChannelOperation

WME

MIB

MLME

PLMEIEEE

160

9.3-

2007



Assessing the current state-of-the-art of V2X

Feasibility of direct and wireless multi-hop vehicle-to-vehicle and vehicle-to-infrastructure communication based on WLAN has been proven

Essential building blocks exist todaySpectrum (but 700 MHz band could be a ‘game change’)ProtocolsApplications, deployment scenariosSecurity concepts ...

Still: some “grand challenges” need our attention



Grand Challenges: an non-exhaustive overview

Does vehicle-to-X communication have a beneficial impact?

On traffic safety?On traffic efficiency?

Does it scale?Every vehicle sends out data IEEE 802.11: lots of packet collisions does vehicle-to-X communication have a beneficial impact?

Can the operation of those networks be (self-) managed?

1. Communication-centric aspect

2. System-centric aspect

3. Field operational test,cooperative systems look ahead


Types of communication for active safety

Periodic messages („Beacons“)Obtain local traffic information to detect dangerous traffic situationsOne-hop broadcastsFigure of merit: probability of reception

Event-driven messages („Emergency message“)Hazard detected, needs to be communicatedInformation disseminationFigures of merit: probability of reception, latency



Scalability challenge (1)

11 vehicles per km and lane

Each vehicle sends 10 beacons/s

Size of beacon: 500 Bytes

Communication range: 1000m

Probability of reception?

Beaconing load:

66 vehicles per km

10 Hz

4 kb

2400m (carrier sense range)

about 6.3 Mbps



Scalability challenge (2)

O.k., example on previous slide is maybe ‚extreme‘... but a density of 11 vehicles per km and lane is not.

Options to reduce channel/beaconing load:Reduce packet sizeReduce rateReduce transmit power

What is the best choice (“optimal control”)?

As long there is no theory, we depend on simulations

“Credibility” of simulation results depends on “realistic” models

Let us have a look to “realistic” models first



Elements of „realistic“ simulations

Network Simulatorns-2

Vehicular MovementPatterns

IEEE 802.11p Radio PropagationModel - Nakagami

Reception andInterference Models

BugFixIEEE 802.11

MAC PerformanceMetrics

Overhaul of IEEE 802.11 modeling and simulation architecture in NS-2,Q. Chen, F. Schmidt-Eisenlohr, D. Jiang, M. Torrent-Moreno, L. Delgrossi, H. Hartenstein, Proc. ACM MSWiM, October 2007

Since March 31, 2008:

Part of NS-2.33

... still, results depend on parameter settings ... no agreed set yet



Example result: impact of transmission power

3 Mbps, 10pckts/s, 66 vehicles per km, Nak 3, CW of 31


IncreaseTx power


Transmit power control: D-FPAV

Our view: transmit power should be adjusted adaptivelyFinal option when packet size and rate cannot be further reduced

Fairness aspect is important

Distributed control is required

Goal: network-wide guaranteed “Maximum Beaconing Load”

MbpsMaximal channel bandwidth

Maximum Beaconing Load

Used for beaconing

Available for otherdata traffic



Result: traffic differentiation via power control

Nakagami (m=3), 10 packets/s, MBL 2,5Mbps (out of 3 Mbps), comm. range max. 1000m



Impact assessment of vehicle-to-X communication

From „quality of service“ to „quality of experience“

Requires coupling of simulators for communication system, mobility and driver behavior, application

For example, coupling of NS-2, VISSIM, Matlab as proposed by Lochert et al., ACM VANET 2005

Traffic safety Typically, scenarios contain up to several hundreds of vehiclesHigh accuracy

Traffic efficiency: Large-scale scenarios with up to several tens of thousands of vehiclesLess accuracy required than with assessment of traffic safety



Traffic safety: how to show the impact?

Requires accident modeling (driver behavior model)Wrong driving decision due to missing information or wrong assessment of the traffic situation

Our “first shot” experimentExtended Wiedemann follow-the-driver model by lane-change maneuverInstalled an “inattentive” driverVaried the amount of neighborhood information that the “inattentive”driver gets delivered by vehicular communicationSimple application classifying dangerous and non-dangerous traffic situations



Traffic safety: preliminary results (1)

The figure shows ‚trend lines‘ – results can definitely be improved



Traffic safety: preliminary results (2)

Probability of collision when wish to change

lanes is expressed

Probability of collision when changing lanes

The figure shows ‚trend lines‘ – results can definitely be improved



Traffic efficiency: how to show the impact?

Assume the following V2X scenarioSpeed funnel: from 120 km/h to 60 km/h over 900mCheck average velocity in dependency of equipped vehicles

geographical location [m]aver

age

velo

city

[km

/h]

Assume now 33 km of highway with about 3000 vehicles



Traffic efficiency: speed-up via hybrid simulation

Why simulating every beacon message of tens of thousand of vehicles when the object of interest is, e.g., dissemination of warning messages/speed limits?

Because “background traffic” matters ...

Idea: use of hybrid simulationBeaconing load: put into mathematical model (for probability of reception, latency)Warning messages: use standard discrete-event simulationsCan also be used for distinguishing between other data traffic classes (e.g. safety vs services)

Speed-up: we observed a gain of about 500 compared to standard NS-2



Traffic efficiency: example of analysis

Using the hybrid simulation approach

Work by S. Assenmacher and F. Busch, TU Munich

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Impact assessment: status quo

We studied basic methodologyNot the final wordMuch room for improvement

We need better modelsSafety aspect

Accident modelsDriver behavior models (how does a driver react on V2X information?)

Efficiency aspectMathematical models needed for probability of reception or latency under various conditions

Collaboration of transportation engineers and communication experts is essential



Look ahead: field operational tests (1)

© Photo by M. Miller, Nordsys

FleetNetdemonstator 2002-2003

Network-on-Wheels demonstrator May 2008




California VII test bed http://vii.path.berkeley.edu/vii/monitor/




Again, a scalability challengealso for operation & management

Simulations and impact assessment required for network and experiment planning

EU FP7 Support Action on Field Operational Test (FESTA)

Handbook available since April 2008Covering: performance indicators, experimental procedures, data acquisition ...But also: legal and ethical issues, insurance issues ...



Look ahead: towards truly cooperative systems

V2X level

operator level

governmental level

Cooperation on various levels ...

traffic level



Summary (outline of the talk)

Assessing the current state-of-the-art in vehicle-to-X communication

Traffic telematics today: public transport, road operatorsStatus quo of vehicle-to-X system design

Two „grand challenges“ of vehicle-to-X communicationScalability: radio channel congestion controlImpact assessment of vehicle-to-X communication

A look ahead Field operational testsCooperative systems


Conclusion: vehicle-to-X communication

We came a long way ...Fundamental building blocks available today

But we still need a better understanding ...How do technology/parameter/configuration settings influence scalability and system impactAnalysis – Simulation – Field tests

When is the right time to deploy a first generation of a vehicle-to-X communication system?

Maturity is a big issue: system has to work reliably in *all* situations

My point of view: no way back!

... let us avoid this:


Selected references

A tutorial survey on vehicular ad hoc networks, H. Hartenstein, K. Laberteaux, IEEE Communications Magazine, vol. 46, no. 6, June 2008, pp. 164-171

Overhaul of IEEE 802.11 modeling and simulation architecture in NS-2, Q. Chen, F. Schmidt-Eisenlohr, D. Jiang, M. Torrent-Moreno, L. Delgrossi, H. Hartenstein, Proc.10th ACM/IEEE MSWiM, Chania, Greece, October 2007, pp. 159-168

Enabling efficient and accurate large-scale simulations of VANETsfor vehicular traffic management, M. Killat, F. Schmidt-Eisenlohr, H. Hartenstein, Chr. Rössel, P. Vortisch, S. Assenmacher, F. Busch, Proc. 4th ACM VANET, Montreal, Quebec, Canada, September 200, pp. 29-38

Distributed fair transmit power adjustment for vehicular ad hoc networks, M. Torrent-Moreno, P. Santi, H. Hartenstein, Proc. 3rd IEEE SECON, Reston, VA, USA, September 2006, pp. 479 - 488

Please also look at upcoming PIMRC’08 and VANET’08 papers

http://dsn.tm.uka.de/english/publications.php

vehicular networks â€“ quo veheris?

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