VANETs - Forschungsgruppe DSN · – VANET ACM Workshop ... » Find best strategies for VANETs’ protocols to fight against unreliable ... Nakagami distribution

Dezentrale Systeme und NetzdiensteMarc Torrent Moreno 1

Institut für Telematik, Universität Karlsruhe (TH), 2005

VANETsMarc Torrent-Moreno, Prof. Hannes Hartenstein

Decentralized Systems and Network ServicesInstitute for Telematics, University of Karlsruhe

April 15th 2005

Marc Torrent Moreno 2Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste

Main Motivation (In all American presentations ;-))

According to the U.S. National Highway Traffic Safety Administration (2003):

» ~6.3 million police-reported traffic accidents

» ~43,000 people were killed

» ~3 million persons injured

» Annual economic impact of traffic-related accidents: >$230 billion

Automotive safety systems trend go from passive to intelligent and active … Preventive


Where communications can help

… main focus: SAFETY

* Source: DaimlerChrysler AG


Technology Final Goals

» Safety on Roads (huge list of situations/applications considered)– Reducing accidents– Alleviating accident damages

» Traffic Conditions– Improve transport efficiency– Monitor traffic demand

» Environment– Reduce traffic congestion– Reduce pollution

» Driving Comfort – Driver assistance– Infotainment applications


Overview

» VANETs, Introduction

– Hot topic all over the world

– VANET ACM Workshop

– Network on Wheels Project

» VANETs @Uni-Karlsruhe

– What our view is

– What we are focusing on


VANETs, Intro

» Vehicular Ad-Hoc Network

… comes from well known concept ‘MANET’, but considers:

• Vehicle-to-vehicle communications• Vehicle-to-infrastructure communications

» Getting relevance since Oct’02: FCC allocates 75MHz of spectrum to improve safety, efficiency and comfort on roads

» Currently both industry and academia involved in ambitious projects motivated by governmental sponsorships


Related Conferences/Workshops

» IEEE Vehicular Technology Conference (VTC)

» IEEE Intelligent Vehicles Symposium (IV)

» IEEE Intelligent Transportation Systems (ITS)

» ACM International Workshop on Vehicular Ad Hoc Networks (VANET)

» International Workshop on Intelligent Transportation (WIT)


1st ACM workshop on Vehicular Ad-Hoc Networks (VANET 2004)

» Ultimate goal: to explore the development of wireless vehicular ad hoc networking technologies

» Main interest: safety and commercial applications enabled by short to medium range communication systems and/or networks (vehicle-vehicle or vehicle-roadside)

» Call for papers: new applications, networking protocols, security paradigms, network management technologies, power control, modulation, coding, channel modeling, etc.

» Impression from attendance:– Emerging and motivated research community– Lots of interest from industry

http://www.sigmobile.org/workshops/vanet2005/

2005:


Ongoing Projects Over The World

» USA:– Vehicle Safety Communications Consortium (VSCC)

http://www-nrd.nhtsa.dot.gov/pdf/nrd-12/CAMP3/pages/VSCC.htm/– DSRC/WAVE Technology

http://www.leearmstrong.com/DSRC/DSRCHomeset.htm/ (all info, up to date)http://grouper.ieee.org/groups/scc32/dsrc/index.html/ (standarization)

» Europe:– Car to Car Communication Consortium

http://www.car-to-car.org/– PReVENT

http://www.prevent-ip.org/– CarTalk

http://www.cartalk2000.net/– Network on Wheels (Germany)

http://www.network-on-wheels.de/

» Japan:– ITS Japan

http://www.its-ip.org/


Projects Main Goals

» Assess today’s and future applications

» Specify technology/system

» Push standardization process

» Find adequate market introduction strategies


Network on Wheels Project

» Picking up FleetNet project results (Demonstrator deployed)

» Founded by German Ministry of Education and Research (BMB+F)

» Started in June 2004, it will last until May 2008

» Main goals: – Solve technical challenges related to robustness, performance, scalability

and security for inter-vehicle communications– Design base architecture and platform for VANET technology– Explore applications for market introduction


VANETs Remarks (I)

» 802.11 OFDM decided as the lower layer technology (~802.11a)

» USA dedicated 75MHz at 5,9Ghz band. 7 Channels of 10Mhz

» Europe (C2CCC) in the process of getting some bandwidth

» For car manufacturers costs are a major concern:– All cars will have GPS receiver– Only one transceiver? (channel hopping?)– Base system without Digital Map? (benefit for safety, non-safety?)

» USA … they are taking decisions faster: – FCC defined 3 priorities in its report : Safety-of-Life, Safety, Non-Safety– 1 Control channel where safety applications should reside– 6 Service channels to support non-safety traffic– Standardization bodies involved: IEEE, ASTM ...


VANETs Remarks (II): Data traffic estimation req.

Non-Safety0 – 90N/AN/A> 20MbpsMovie Download(2 hours of MPEG 1) /10 min. down. time

Non-Safety0 – 90Periodic~500~100~2Kbps

Service Announc.

Non-Safety≤15Event~50~100Toll Collection

Safety300 – 1000Event~1000~100Transit Vehicle Signal Priority

Safety50 – 300Periodic~1000~100~1Kbps

Work Zone Warning

Safety ofLife

50 – 300Periodic~100~100~10Kbps

Coop. CollisionWarning

Safety ofLife

50 – 300Event~100~100Inters. CollisionWarning/Avoidance

PriorityComm. Range(m)

NetworkTraffic Type

AllowableLatency (ms)

Packet Size(B)/Bwth

Application

* Source: California PATH

•Still, applications requirements are not standardized

•The gap between Applications and Communications must be filled



VANETS@Uni-Karlsruhe


How do we see VANETs @ Uni-Karlsruhe?

VANETs are characterized by:

» Wide spectrum of applications

» Type of communication (end-to-end notion revised)

» Self-organization and self-management (fully decentralized)

» Packets vs. Information (state / data aggregation)

» Network protocol requirements (efficient geo-casting/flooding)

» Adverse medium conditions (congestion and radio channel)


What is our focus @Uni-Karlsruhe?

Our motivation:

» It is demonstrated that ‘real-world’ conditions have significant impact on protocol performance

» There is no proof of well (idealistically) studied protocols to work in real-world

» Unfortunately, VANETs will face ‘worst-conditions’ scenarios

Our Goal:

» Find best strategies for VANETs’ protocols to fight against unreliable wireless channels


What elements do we need to perform this work? (simulation)

» Realistic radio propagation models

» Realistic traffic distributions and movement patterns

» Verified simulator

What do we have now?

» Some realistic highway movement patterns (Courtesy of DC Germany)

» Realistic radio propagation model at highway scenarios using Nakagami distribution (Courtesy of DC Palo Alto)

» Verified ns-2 802.11 MAC and PHY layer (Uni-Karlsruhe) adjusted to real 802.11a Atheros Chips (values courtesy of Atheros)

… but we need more



“Broadcast Reception Rates and Effects of Priority Access in 802.11-Based Vehicular

Ad-Hoc Networks”Marc Torrent-Moreno, University of Karlsruhe

Daniel Jiang, DaimlerChrysler RTNA, Inc.

Hannes Hartenstein, University of Karlsruhe

First Problem study:

1st ACM workshop on Vehicular Ad-Hoc Networks, Oct‘04


Problem Statement

But:

» All vehicles send data → contending for the channel

» Hidden terminal problem

» Channel characteristics

Broadcastsemergency message

What is the probability of

reception for this car?


Channel modeling: the standard way …

c.r.

Unit Disc Graph Model

If no interference:• Cars inside communication

range receive the packet

• Cars outside communication

range do NOT receive the

packet


In reality …

“c.r.”

Reality

If no interference:• Cars inside “communication

range” CAN receive the packet

• Cars outside “communication

range” MAY receive the packet

Reception Probability (d)?


Dynamic Scenario (mobile and TRG or Nakagami)

700 m

- 8 lanes, 2 direcctions (912 cars)

- Constant speed different lanes

- Distance between cars: 20m

- Comm. Range: 100m, 200m

- Packet size: 200B, 500B

- 10 pckts/s

0

0.2

0.4

0.6

0.8

1

-92 -90 -88 -86 -84 -82 -80 -78 -76 -74 -72 -70

Dis

trib

utio

n

Received power (dBm)

50m distance100m distance200m distance

Nakagami received power distribution


Dynamic Scenario – Metrics

Safety Applications

Broadcast Scenario

Delay

Effectiveness

» Metrics:– Channel access time– Probability of reception


Channel Access Time

26.5 ms9.0 ms6.4500 B200m (Nak)

16.4 ms3.6 ms6.4500 B200m

3.9 ms1.2 ms2.56200 B200m

4.8 ms1.6 ms3.2500 B100m

0.9 ms0.4 ms1.28200 B100m

Non-PriorityPriorityLoad MbpsPckt SizeCom. Range

Channel Access TimeScenario

» Clearly the Priority node has always shorter Channel Access Time !


Probability of Reception (not saturated scenario)

» 200 bytes packets

» 200 m intended communication range


Result of the study

» Results– Priority access provides improvement in channel access time (AIFS and

CW can be adjusted)– When saturation occurs, nodes experience severe performance

degradation (probability of reception can be as low as 20% at half com. range)

– Non-deterministic radio model degrades performance of both types of nodes (worse effect on probability of reception of the prioritized ones)

» Conclusions– Need better understanding of distributed MAC on global scale – Priority access methods as well as relay/repetition strategies are very

important aspects of future safety-critical applications

* For more detail, please take a look at the paper


Our research right now

4 ongoing research studies

» Highway routing with realistic radio propagation models

» Effect on reception rates of new ‘capture effect’

» Robust strategies for data dissemination (flooding)

» Fair strategies to limit load of safety applications



Thank you very much for your attention !

http://dsn.tm.uka.de

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VANETs - Forschungsgruppe DSN · – VANET ACM Workshop ... » Find best strategies for VANETs’ protocols to fight against unreliable ... Nakagami distribution