Overview of Vehicular Networking

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Overview of Vehicular Networking

• ???
• ???????

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Todays agenda

• 930-1030 this talk
• 1030-1100 break
• 1100-1200 talk by ???
• 1200-200 lunch
• 200-300 panel discussion

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Scenario
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What are in a vehicular network

• Vehicles (on-board unit)
• Road side unit/equipment
• Communication protocols
• Vehicle to vehicle
• Vehicle to road side
• Vehicle to handheld device
• Network infrastructure
• GPS
• Back-end system

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Connected car scenario
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Difference of communications
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Applications of a vehicle network

• Safety
• Intersection warning
• Vehicle-based
• Infrastructure-based
• Vehicle probe
• Travel time estimation
• Environmental data collection
• Road surface data collection
• Emergency vehicle
• preemptive traffic control
• Navigation

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Telematics vs. ITS

• Telematics
• The integrated use of telecommunications and
  informatics within road vehicles
• ITS (intelligent transportation system)
• add information and communications technology to
  transport infrastructure and vehicles

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Intelligent vehicle
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Intelligent Traffic control with telematics
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Traffic control
Intersection
Approach
Approach
Too long.
Vehicle
Traffic Light
Too short.
Approach
Approach
12
Related work
Limited!!
SCOOT (Split, Cycle and Offset Optimization
Technique)
Intersection
Detector
SCATS (Sydney Coordinated Adaptive Traffic System)
Case1 Queue is too long
Unfair..
70sec
70sec
30sec
50sec
50sec
60sec
Case2 Some problems in the intersection
50sec
70sec
50sec
60sec
70sec
30sec
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Adaptive Traffic Lights System
TrafficView
Controller
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Adaptive Traffic Lights System
Green time may be extended
Controller
Too many vehicles. I must wait
Case2 Vehicles in the Intersection
Case1 pedestrian
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Is this for real?
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Overview Vehicular Network

• Scope
• Projects
• MANET (Mobile Ad-hoc NETwork)
• Protocols
• Research issues

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National initiatives

• US
• VII (Vehicle Infrastructure Integration)
• Europe
• i2010
• ERTICO

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VII goal

• Safety
• E.g. reduce number of car accidents
• Driving quality
• E.g. shorter driving time
• New Market
• E.g. applications that run on vehicle OBU

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VII business model

• Government
• builds network infrastructure (DSRC)
• Subsidize auto-maker for OBU application
  development
• Auto-maker
• All new cars sold in US are VII-compliant
• Allow government to run safety-related
  application on OBU

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VII consortium

• Auto-makers OBE and applications
• Ford
• GM
• DCX (DaimlerChrysler)
• BMW
• VW
• Nissan
• Toyota
• Honda
• State DOT (Department of Transportation) network
  infrastructure and RSE
• Subcontract to Booz Allen Hamilton (a global
  consulting firm)

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Schedule
3B
54M
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Planned deployment
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System architecture
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Current deployment
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Future traffic estimate

• WiMax --- 60
• DSRC --- 10
• WiFi --- 10
• Satellite --- 10
• Cellular (e.g. UMTS) --- 10

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Dual Mode OBE

• OBE can be dual mode
• Public application (safety, information)
• DSRC
• Mandatory by VII
• 27Mbps, 1km range
• 802.11p (PHY, MAC), 1609 (upper layer extension)
• Private application (voice, infotainment,
  navigation)
• WiMax, WiFi, Cellular
• Value differentiator of auto-maker OBE

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i2010

• A European Information Society for growth and
  employment
• the European Commission's strategic policy
  framework laying out broad policy guidelines for
  the information society and the media in the
  years up to 2010
• 3 flagship initiatives
• Intelligent Car
• Digital Libraries
• Ageing Well in the Information Society

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Intelligent Car

• Night vision
• Advanced cruise control
• Use radar to maintain safe distance

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Intelligent car

• CyberCars
• Driver-less
• Run at low speed (30km/hr)
• Can avoid obstacles
• Park automatically
• With a fee, users would have access right
• CyberCars2
• Follow-up project
• Focus on V-to-V and V-to-infrastructure
  communication

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Intelligent Car

• CarTalk project
• Focus on vehicle-to-vehicle communication
• Information is transmitted from one car to
  another car
• Vehicles nearby form an ad-hoc network

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ERTICO

• Europe-based
• ERTICO represents the interests and expertise of
  around 100 Partners
• provides a platform for its Partners to define
  common research development needs
• acquires and manages publicly funded ITS
  development deployment projects on behalf of
  its Partners
• Plan the deployment of ITS
• Influence decision makers and opinion leaders

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Organization

• Board members
• Industry
• Renault
• Volkswagen AG
• Siemens
• FIAT/IVECO
• Navteq
• Robert Bosch
•  Public Authorities
• UK Department for Transport
• Slovenian Ministry of Transport
• Swedish Road Administration
•  Infrastructure Operators
• ASFA
• Thales
• Vodafone
•  Users
• ADAC
• RACC

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projects

• Safety
• ADASIS Forum advancing map-enhanced driver
  assistance systems
• AIDE enhancing safety with adaptive driver
  assistance systems
• ERTRAC contributing to European road transport
  research priorities
• eSafety Forum making Europe's roads safer for
  everyone
• FeedMAP enabling quick and inexpensive map
  updates
• GST creating easy access to dynamic safety
  services
• HeavyRoute supporting quicker and safer freight
  transport
• IP PReVENT supporting the driver, preventing
  accidents
•   MAPSADAS using digital maps to improve road
  safety
•   RESPONSE3 bringing ADAS to market quickly
  and safely
• SAFESPOT supporting smart vehicles on safe
  roads
• SpeedAlert Forum keeping drivers informed of
  speed limits at all times  
• Security
• EOS building a European security partnership
  for the 21st century
• EURAM generating a European risk assessment
  methodology for critical infrastructures
• Efficiency Environment
• AGILE making the most of satellite navigation
  services
• CVIS facilitating vehicle and infrastructure
  cooperation

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E-call

• A mandate for all vehicles in EU after 2010/9
• Under eSafety Forum

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E-call requirement
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Overview Vehicular Network

• Scope
• Projects
• MANET (Mobile Ad-hoc NETwork)
• Protocols
• Research issues

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Mobile Ad Hoc Networks

• Formed by wireless hosts which may be mobile
• Without (necessarily) using a pre-existing
  infrastructure
• Routes between nodes may potentially contain
  multiple hops

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Mobile Ad Hoc Networks

• May need to traverse multiple links to reach a
  destination

A
B
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Mobile Ad Hoc Networks (MANET)

• Mobility causes route changes

A
B
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Why Ad Hoc Networks ?

• Ease of deployment
• Speed of deployment
• Decreased dependence on infrastructure

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To summarize
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Applications Vehicular Ad-hoc network
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Applications Wireless Sensor Network
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Applications Mesh Network
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VANET vs. MANET

• VANET (Vehicular Ad-hoc Network) can be
  considered a subset of MANET (Mobile Ad-hoc
  Network)
• Nodes do not move in any random direction
• Nodes are powered (energy is not an issue)
• Node contact time is limited
• Intermittent connectivity might occur
• Node speed is bounded
• Mostly high speed, but occasionally stop and slow
  moving

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Overview Vehicular Network

• Scope
• Projects
• MANET (Mobile Ad-hoc NETwork)
• Protocols
• 802.11p
• WiMax
• Research issues

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802.11p

• WAVE (Wireless Access in Vehicular Environment)
• Based on .11a
• 5.9GHz
• Data rate 6-27Mbps
• Designed for general Internet access, can be used
  for ETC as well
• 7 licensed channels
• Use open off-the-shelf chipset and software
• Vehicle-to-roadside and vehicle-to-vehicle
• Command-response and peer-to-peer

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5.9 GHz DSRC BAND PLAN with 10 MHz CHANNELS
POWER LIMITS
Dedicated Public Safety
Shared Public Safety/Private
Intersections
Control
Veh-Veh
Short Rng Service
Med Rng Service
40 dBm
Power Limit
44.8 dBm
Power Limit
33 dBm
23 dBm
Power Limit
Uplink
Downlink
Public Safety/ Private
Public Safety Intersections
Public Safety/ Private
Public Safety/ Private
Public Safety/ Private
Public Safety Veh-Veh
Control Channel
Ch 172
Ch 180
Ch 184
Ch 182
Ch 178
Ch 174
Ch 176
5.850
5.855
5.860
5.865
5.870
5.875
5.880
5.885
5.890
5.895
5.900
5.905
5.910
5.920
5.925
5.835
5.845
5.915
5.840
Frequency (GHz)
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Power control

• Pubic safety application are allowed higher power
  transmission than private application
• The reference point for RF power is the center of
  front bumper of the vehicle

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WAVE

• intended to support a full range of existing uses
  for IEEE 802.11
• includes a number of new classes of applications
• roadway safety (vehicle collision avoidance)
• emergency services (police, ambulances, etc).
• New requirement in WAVE
• reliability of the data communications
• extremely low latencies required
• From association to end of data exchange lt 100ms

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Multiple applications on top of DSRC
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DSRC TECHNOLOGY CHARACTERISTICS

• Approach Active
• Bandwidth 75 MHz (5.850 - 5.925 GHz)
• Modulation QPSK OFDM (with 16QAM and 64QAM
  options) (BPSK preamble)
• Channels 7 - 10 MHz channels (optional
  combinations of 10 and 20 MHz channels)
• Data Rate 6, 9, 12, 18, 24, and 27 Mbps with 10
  MHz Channels (3 Mbps preamble) (or 6, 9, 12, 18,
  24, 36, 48, and 54 Mbps with 20 MHz Channel
  option) (6 Mbps preamble)
• Max Tx Pwr 28.8 dBm (at the antenna input)
• RSU equivalent isotropically radiated power
  (EIRP) Nominal 0 - 33 dBm (1 mW - 2 W) / Max.
  44.8 dBm (30 W)
• OBU EIRP Nominal 0 - 20 dBm (1 - 100 mW) /
  Max. 44.8 dBm (30 W)
• RSU and OBU Sensitivity - 82 dBm (QPSK) / - 65
  dBm (64QAM)
• Carrier-to-interference-ratio (C/I) 4 - 6 dB
  (for QPSK _at_ 10-4 BER coded) / 16 - 17 dB (for
  64QAM _at_ 10-4 BER coded)
• 300m (1000m max) range radio
• station can only send or transmit, but not both
  at the same time (Half-duplex)

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Some technical terms

• DSRC (dedicated short-range communication)
• Apply to many forms of short-range low-latency
  radio
• 5.85 to 5.925GHz in North America
• OBU a device performs the functions of 802.11
  station with additional WAVE functions
• RSU a device performs the functions of 802.11
  access point with additional WAVE functions
• WBSS (WAVE basic service set) A set of OBUs
  operating in a WAVE mode controller by an RSU
• WIBSS (WAVE independent basic service set) A set
  of OBUs operating in a WAVE mode that forms a
  self-contained network
• Do not use beacons
• Connection is created/tore-down on-dmand

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WAVE Configurations
BSS with RSUs and OBUs
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WAVE Configurations
BSS with OBU only
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WAVE Configurations
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WAVE Configurations
BSS Connects Onboard Computer Through the WAN to
ITS Application
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Channel Access

• Control Channel
• used for broadcast transmissions and to establish
  communications.
• Service Channels
• between Roadside Units
• between Onboard Roadside
• between OBUs.
• only RSUs can broadcast on the Control Channel.
• All IEEE 802.11 frame may be used on Service
  Channels.

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Synchronization

• All STAs (stations) within a single
  infrastructure BSS or IBSS shall be synchronized
  to a common clock.
• DSRC devices do not implement the 802.11 scanning
  function.

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WAVE Start

• For fast access, WAVE does NOT allow the 802.11
  active scanning, authentication and association
  procedures.
• WAVE beacons contain all information about the
  BSS and the offered application.
• Upon receipt of an MLME-WAVESTART.request, a
  service provider RSU shall start an
  infrastructure WAVE BSS. When an OBU receives a
  WAVE beacon, it will indicate all necessary
  information (equivalent to the results of
  scanning and association) to WAVE management
  entity (WME).

MLME MAC layer management entity
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WAVE Start

• If the WAVE management entity (WME) accepts the
  application advertised in the beacon, the OBU
  shall join the infrastructure WAVE BSS by issuing
  an MLME-JOIN.request.

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WAVE Announcement/Acknowledgement

• Only RSUs shall broadcast beacon frames on the
  control channel.
• Beacon frames contain Provider Service Tables
  (PSTs) announcing RSU application services.
• OBUs shall only use WAVE announcement action
  frames containing PSTs to announce OBU
  application services on the control channel.
• A WAVE announcement action may be broadcast or
  unicast.
• When an OBU receives a WAVE announcement frame,
  it shall indicate all necessary information to
  its WME.

WSIE WAVE Service Information Element
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WAVE Announcement/Acknowledgement

• Only RSUs shall broadcast beacon frames on the
  control channel.
• Beacon frames contain Provider Service Tables
  (PSTs) announcing RSU application services.
• OBUs shall only use WAVE announcement action
  frames containing PSTs to announce OBU
  application services on the control channel.
• A WAVE announcement action may be broadcast or
  unicast.
• When an OBU receives a WAVE announcement frame,
  it shall indicate all necessary information to
  its WME.

WSIE WAVE Service Information Element
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Channel switching

• OBUs switch channels based on Beacon or PST
  coordination or both.
• If a single channel OBU switches to a Service
  Channel and no frames addressed to that OBU are
  received within 100 ms the OBU switchs back to
  the Control Channel.

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Priority Transmissions

• DSRC transmissions gives priority to the
  transmission of safety-related messages.
• Safety messages are normally sent on the Control
  Channel but can be sent on any of the Service
  Channels in use.
• The Highest Priority Public Safety and Vehicle
  Safety Messages are broadcast from OBUs on all
  channels and by RSUs on the Control Channel and
  the Service Channel(s) in use.

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Priority Transmissions

• Prioritized DSRC services use the Enhanced
  Distributed Channel Access (EDCA) as defined in
  IEEE802.11e.
• Data frames are transmitted with the medium
  access parameters defined in the EDCA parameter.
• Traffic streams are NOT permitted on the Control
  Channel.

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WAVE User priority

• Four priority levels
• Low
• Medium
• High
• Highest
• High and Highest reserved for only high priority
  public safety applications.
• Private communications and low priority safety
  messages use Low and Medium.

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EDCA Parameter Set element

• WAVE prioritized access operations uses the EDCA
  mechanism.
• For data exchanges within a WAVE BSS, the EDCA
  parameter set received in the WAVE beacon shall
  be used.

ACI AC Index
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802.16

• aka WiMax
• Wireless Metro Internet
• Fast last mile access to network
• Target Applications
• Data
• Voice
• Video
• Real time videoconferencing
• Fast cable/fiber to end user is expensive

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Usage Scenarios
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Comparison of wireless standards
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Why WiMax?

• Better spectral efficiency than 3G
• Consider multiple antennas right from the start
• OFDM is more amenable to MIMO implementation
• Higher peak data rate
• Higher average throughput
• Support more symmetric linnks
• Lower cost
• IP architecture from bottom up
• But 3G has a better mobility support

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WiMax Features

• Broad bandwidth
• Up to 134.4 Mbit/s in 28 MHz channel (in 2-66
  GHz)
• 32Mb/s -134.4Mb/s
• 1.25/2.5/5/10/14/20/25/28MHz per channel
  (3.5/7/8.75/13.5MHz)
• Supports multiple services simultaneously with
  full QoS
• Efficiently transport IPv4, IPv6, ATM, Ethernet,
  etc.
• Wireless transportation system (ferry)
• Bandwidth on demand (frame by frame)
• Similar to HIPERLAN Type II (frame-based
  protocol) and DOCSIS (Data Over Cable Service
  Interface Specifications)
• Centralized control
• MAC designed for efficient used of spectrum
• Comprehensive, modern, and extensible security

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• Supports multiple frequency allocations from 2-66
  GHz in 802.16 (10-66GHz), 802.16a (2-11GHz)and
  802.16e (lt6GHz) 700MHz
• Single carrier (SC) for line-of-sightsituations
• OFDM and OFDMA (MC) for non-line-of-sight
  situations
• OFDM orthogonal frequency division multiplexing
• OFDMA orthogonal frequency division multiple
  access
• OFDMA 1.25 MHz, 2.5, 5, 10, 14 and 20 MHz
  channels (and more)
• Access schemesTDD (time division duplex) and
  FDD (frequency division duplex)
• Link adaptation Adaptive modulation and coding
• Point-to-multipoint (star) topology and mesh
  network extension
• Support for adaptive antennas and space-time
  coding (in 802.16a)
• Extension to mobility

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802.16 vs. 802.16e

• Downlink data rate 9.4Mbps vs. 46Mbps
• Uplink data rate 3.3Mbps vs. 7Mbps
• Multiplexing TDM vs. OFDMA
• Modulation both use QPSK, 16QAM, 64QAM
• Coverage 3-5 miles vs. 2 miles
• Frequency band 3.5GHz/5.8GHz vs. 2.3GHz/
  2.5GHz/3.5GHz
• 5.8GHz is license-exempt

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802.20

• Target for very high mobility
• gt 250 kmph
• Operate below 3.5GHz
• 4Mbps downlink and 1.5Mbps uplink
• Still under developing
• Lack of consensus
• Issues with the standardization process

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Overview Vehicular Network

• Scope
• Projects
• MANET (Mobile Ad-hoc NETwork)
• Protocols
• Research issues
• 802.11p
• Mobility
• Routing
• Information dissemination

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The Promise of DSRCCould road-accident be the
thing of the past?

• Vehicles routinely broadcast their position,
  velocity, acceleration using built-in DSRC
  communication system
• With the knowledge of nearby vehicles status,
  the onboard DSRC alerts the driver of impending
  threats
• Drivers take actions in time to avoid accidents

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Co-existence of Safety Non-Safety

• To be viable, DSRC needs to support non-safety
  as well
• E-toll, music download, etc.
• Non-safety should not interfere with safety
• IEEE solution multichannel structure for DSRC
• Divides entire DSRC spectrum into 7
  non-overlapping channels
• Safety on control channel (CCH), non-safety on
  service channels (SCH)

80
IEEE 1609.4 Multi-Channel Operation

• Conventional radios operate with one channel at a
  time
• Safety-non-safety coexistence ? switch bw CCH/SCH
  
• vehicles must switch to CCH several times a
  second
• 1609.4 requires all vehicles to synchronize the
  switching
• Concept of Sync Interval (SI) which in turn is
  divided into CCH interval (CCHI) and SCH interval
  (SCHI)
• Result cyclic transmission
• Safety tx followed by non-safety tx in a
  repetitive fashion

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DSRC Shares in Cyclic Transmission

• Safety and non-safety share the limited DSRC
  resource
• Increasing non-safety share decreases safety
  (vice-versa)
• Shares are strictly controlled through
  CHI/SCHI/SI
• Non-safety share SCHI/SI, safety CHI/SI
• Note that SCHICHISI (ignoring GI)
• 1609.4 has not specified values for these
  intervals

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Safety First

• Performance of safety has to be guaranteed
• Selection of SI and CHI has performance
  implications for safety applications

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How SI relates to safety performance?Concept of
updating frequency

• Vehicles must exchange status f times a second
• Must switch to CCH f times a second ? SI 1/f
• Most researchers believe that f 10 ?SI100ms
• Setting SI100ms guarantees that every vehicle
  will get a chance to broadcast its status every
  100ms

84
How CCHI relates to safety performance?Concept
of reliability

• SI100ms is only part of the safety requirement
• A safety broadcast may get lost due to collision
• DSRC is contention based (CSMA/CA 802.11p)
• ACK/Retx and RTS/CTS not applicable to broadcast
• CCH interval has a direct influence on
  reliability
• Larger the CCHI, lower the collision probability
• Reliability req. imposes a lower bound on CCHI

85
Why VANET simulation?

• Most of VANET research is done in simulation
• Real-world experimentation
• Currently no test-bed available
• Hard to explore scalability
• Classical problem with repeatability
• Emulation
• Uses real sw/hw in simulated environment to
  ensure accuracy
• Higher scalability, but still limited

86
The importance of a mobility model

• Mobility key component of VANET simulators
• Mobility constraints (e.g., streets, buildings)
• Affects velocities and distances between nodes,
  which affects radio transmission
• Nodes should physically interact with one another
• E.g., avoid collisions
• Central to feedback loop in many scenarios
• Cars can change trajectory in response to data

87
What we want for VANET mobility
88
Random waypoint considered harmful

• Random Waypoint (RWP)
• Benefits
• Simple
• Low overhead
• Common
• Disadvantages
• NOT representative of mobility for worst-case or
  general-case performance
• Nodes cannot interact wrt mobility
• Encourages use of open field simulation

89
RWP effects on wireless communication

• Every position on map is a waypoint with equal
  probability
• Artificially high density near center of map
• Nodes generally cannot leave the field
• Data does not leave the field
• Arbitrary stopping points and stopping times
• Affects links among nodes
• Arbitrary speeds and speed distributions

90
Mobility traces

• Advantages
• Represents real motion
• Little overhead in simulation
• Disadvantages
• Difficult to obtain
• Rarely distributed (legal issues)
• Difficult to generalize
• Does not allow feedback loop

91
Vehicular motion
Congestion leads to hot spots at intersections
Vehicles spend more time near intersections even
when uncongested
92
Car mobility wireless communication

• Nodes tend to spend more time at intersections
• Increases interference in this region
• Can reduce connectivity
• Buildings further reduce connectivity between
  nodes on different streets
• Nodes often travel in opposite or orthogonal
  directions
• Short interaction time window
• Vehicular congestion slows nodes
• Can stabilize topology, but can reduce overall
  connectivity
• A good mobility model for VANETs is critical

93
MOVE
94
Network Mobility

• IETF NEMO WG
• RFC 3963 Network Mobility (NEMO) Basic Support
  Protocol (Jan. 2005)
• Extension of Mobile IPv6
• Mobile Router (MR)
• Operates Mobile IPv6
• Establishes a bi-directional tunnel to its
  corresponding Home Agent (HA)

95
Network Mobility
All traffic must pass through the bi-directional
tunnel between the MR and its corresponding
HA. gtTriangular routing
Internet
CN_MN
2
BU
7
4
2
HA_MR
42-gt72 5/prefixlen, 6/prefixlen ?
forward to MR
95
96

• Two routes A-B-D-F (BAD), A-C-D-F (GOOD)

Source
Destination
Fig. 1. A link rupture event is more likely to
occur between vehicles A, B, and D.
97
Geographical routing?
Destination Node
Choose node A (the closest node) for the next hop
Source Node
98
Restricted Greedy Routing
99
Detecting junctions
Beacon message
Correlation coefficient
100
Intermittent connectivity on the road
101
Connection splitting
102
Information Dissemination Motivation Scenario

• Two cars crash while traveling southbound on a
  highway, nearby vehicles cooperate to
• inform the closest ambulance and police stations
• alert approaching vehicles telling them to slow
  down
• notify the highway entrances north of the
  accident
• Messages should ideally propagate
• towards specific target areas
• along the routes where the vehicle density is
  higher

103
Information Dissemination

• How to route messages towards specific target
  areas while considering the underlying vehicle
  density
• Assuming each vehicle knows its geographical
  location and communication range
• How to find the preferred paths to reach the
  target areas?

104
Thanks you

• Question?