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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
Marc Torrent Moreno 3Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
Where communications can help
… main focus: SAFETY
* Source: DaimlerChrysler AG
Marc Torrent Moreno 4Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 5Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 6Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 7Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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)
Marc Torrent Moreno 8Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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:
Marc Torrent Moreno 9Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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/
Marc Torrent Moreno 10Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
Projects Main Goals
» Assess today’s and future applications
» Specify technology/system
» Push standardization process
» Find adequate market introduction strategies
Marc Torrent Moreno 11Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 12Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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 ...
Marc Torrent Moreno 13Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Dezentrale Systeme und NetzdiensteMarc Torrent Moreno 14
Institut für Telematik, Universität Karlsruhe (TH), 2005
VANETS@Uni-Karlsruhe
Marc Torrent Moreno 15Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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)
Marc Torrent Moreno 16Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 17Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Dezentrale Systeme und NetzdiensteMarc Torrent Moreno 18
Institut für Telematik, Universität Karlsruhe (TH), 2005
“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
Marc Torrent Moreno 19Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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?
Marc Torrent Moreno 20Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 21Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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)?
Marc Torrent Moreno 22Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 23Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
Dynamic Scenario – Metrics
Safety Applications
Broadcast Scenario
Delay
Effectiveness
» Metrics:– Channel access time– Probability of reception
Marc Torrent Moreno 24Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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 !
Marc Torrent Moreno 25Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
Probability of Reception (not saturated scenario)
» 200 bytes packets
» 200 m intended communication range
Marc Torrent Moreno 26Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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
Marc Torrent Moreno 27Institut für Telematik, Universität Karlsruhe (TH), 2005 Dezentrale Systeme und Netzdienste
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