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Copyright © 2013 Scott E. Carpenter 1
Inter-Vehicle
Communications (IVC): Current Standards and
Supporting Organizations
Scott E. Carpenter
North Carolina State University,
Department of Computer Science
June, 2013
919-413-5083
Copyright © 2013 Scott E. Carpenter 2
Agenda
• Objectives
• IVC Concepts
• Standards – IEEE 802.11p
– IEEE 1609
– SAE J2735
• Organizations – Vehicle Infrastructure Initiative (VII) (a.k.a. IntelliDrive)
– Vehicle Safety Communications (VSC)
– Intelligent Transportation Systems (ITS)
• Challenges
• Conclusions
Copyright © 2013 Scott E. Carpenter 3
Objectives
• Create a Microsoft PowerPoint (PPT) presentation exploring the
following with respect to IVC :
– An overview of the IEEE 1609 standards, specifically:
• IEEE 1609.1
• IEEE 1609.2
• IEEE 1609.3
• IEEE 1609.4
• Focus on the Network Layer.
• An overview of Vehicle Infrastructure Initiative (VII) and other IVC-
related consortia.
• Recent research / applicability of geocasting.
• Are communications paradigms from IPv6 applicable?
• Pertinence of roadside internet technologies.
• Consider “problems” in terms of “I think I can do that!”
Copyright © 2013 Scott E. Carpenter 4
Inter-Vehicle Communications (IVC)
• Promises – Increased traffic efficiency
– Accident reduction / safety
improvements
– Info / entertainment
applications
• Classifications
– by service • Vehicle Control
• Information Services
– by technical
requirements • Digital bandwidth
• Latency
• Reliability
• Security and authentication
• Network configuration
• Requires wireless ad-hoc
network
Copyright © 2013 Scott E. Carpenter 5
Ad-Hoc Network Classifications
• Wireless Mesh Network (WMN)
• Wireless Sensor Network (WSN)
• Mobile Ad-Hoc Network (MANET)
– Vehicular Ad-Hoc Network (VANET)
– Internet Based Mobile Ad-hoc Network (iMANET)
– Intelligent vehicular ad-hoc network (InVANET)
Copyright © 2013 Scott E. Carpenter 6
VANET Technologies
• DSRC typical
• Other technologies utilized, too.
Copyright © 2013 Scott E. Carpenter 7
VANET Exploration – A Brief History
• Recent:
– WAVE
• (IEEE 1609)
– VSC
• (completed)
– VII
• (completed)
– ITS
• (RITA, USDOT)
Copyright © 2013 Scott E. Carpenter 8
OSI vs. WAVE
Copyright © 2013 Scott E. Carpenter 9
WAVE Protocol Stack
• 1609.1
– Resource manager (a
specific transponder-
like application)
• 1609.2
– Security issues
• 1609.3
– Networking services
• 1609.4
– Multi-channel
operation
• Note dual networking
stack:
– IPv6
– WSMP
Copyright © 2013 Scott E. Carpenter 10
IEEE 802.11p
• Extends 802.11 in the following 4 ways:
– Transmission outside the context of BSS – Because the V2I link might
exist for only a short amount of time, the IEEE 802.11p amendment
defines a way to exchange data through that link without the need to
establish a BSS. Authentication and data confidentiality mechanisms
must be provided by higher network layers.
– Timing advertisement - allows stations to synchronize themselves with
a common time reference.
– Enhanced receiver performances - Optional enhanced channel
rejection requirements, applicable only to OFDM transmissions in the
5GHz band (for both adjacent and nonadjacent channels), are
specified in order to improve the immunity of the communication
system to out-of-channel interferences.
– Use of the 5.9GHz band - Allows the use (in the U.S. and Europe) of
the 5.9GHz band (5.850-5.925 GHz) with 5MHz, 10MHz and 20MHz
channel spacings.
Copyright © 2013 Scott E. Carpenter 11
IEEE 1609 IEEE 1609 WG - Dedicated Short Range Communications Working Group
Standards (As of 6/4/2013)
Active
1609.2-2013 IEEE Standard for Wireless Access in Vehicular Environments — Security
Services for Applications and Management Messages
1609.3-2010 IEEE Standard for Wireless Access in Vehicular Environments (WAVE) -
Networking Services
1609.3-2010/Cor 1-2012 IEEE Standard for Wireless Access in Vehicular Environments
(WAVE)--Networking Services Corrigendum 1: Miscellaneous Corrections
1609.4-2010 IEEE Standard for Wireless Access in Vehicular Environments (WAVE)--
Multi-channel Operation
1609.11-2010 IEEE Standard for Wireless Access in Vehicular Environments (WAVE)--
Over-the-Air Electronic Payment Data Exchange Protocol for Intelligent Transportation
Systems (ITS)
1609.12-2012 IEEE Standard for Wireless Access in Vehicular Environments (WAVE) -
Identifier Allocations
Withdrawn / Superseded Standards Status
1609.1-2006 Trial-Use Standard for Wireless Access in Vehicular Environments
(WAVE) - Resource Manager
Withdrawn
1609.2-2006 Trial-Use Standard for Wireless Access in Vehicular Environments -
Security Services for Applications and Management Messages
Withdrawn
1609.3-2007 IEEE Trial-Use Standard for Wireless Access in Vehicular Environments
(WAVE) - Networking Services
Superseded
1609.4-2006 Trial-Use Standard for Wireless Access in Vehicular Environments
(WAVE) - Multi-Channel Operation
Withdrawn
Copyright © 2013 Scott E. Carpenter 12
Packet Reception
• The probability of packet reception can be
influenced by: – Vehicular traffic density
– Radio channel conditions
– Data rate
– Transmit power
– Contention window sizes
– Packet prioritization
• Major challenge in adjusting the parameters to
match the goals of applications.
Copyright © 2013 Scott E. Carpenter 13
Packet Prioritization
• Enhanced distributed channel access (EDCA)
principles can be used.
• Four access categories with independent channel
access queues are provided.
• Prioritized channel access (based on IEEE 802.11e)
can be shown to lead to improved channel access
times and higher probability of reception for those
packets that receive a higher priority.
Copyright © 2013 Scott E. Carpenter 14
Data Rate, Saturation
• Google driverless car collects 750 MB of sensor data
per second
– Unclear what the min. data needs are for IVC
• Yet, claims are made that IVC networks should support
a variety of vehicular applications
– even in high vehicle density scenarios without adverse impact
to capacity and delay performance.
• Out-of-the-box IEEE 802.11p alone is not sufficient to
provide an appropriate level of quality of service to
support traffic safety-related applications!
Copyright © 2013 Scott E. Carpenter 15
Power Effects
• Increasing Tx power combats fading, but increases saturation.
• Controlling beacon load with distributed power control (TxPC)
increased probability of receipt.
Copyright © 2013 Scott E. Carpenter 16
Multichannel
• Multichannel operations is one of the biggest challenges for IVC.
• 7 Channels, time-multiplexed
• (1) Command channel (CCH) • Serviced every other timeslot
• (6) Service channels (SCH)
Copyright © 2013 Scott E. Carpenter 17
Channel Prioritization
• 4 access categories (per channel)
• Queues have different timer
settings.
Copyright © 2013 Scott E. Carpenter 18
Single-Hop, Multi-Hop
• One-hop:
• Periodic
• VSC recommends rate of 10 msgs / sec, with max. latency of 100 ms and
min. range of 150 m.
• Event-driven
• Multi-hop
• Strongly dependent on vehicle location
• Classical position-based forwarding
• Contention-based forwarding (CBF)
• Single-radio devices may periodically and
synchronously switch between CCH and SCHs
• Dual-radio devices could have one radio tuned to the
CCH and the second radio tunable to one of the
available service channels
Copyright © 2013 Scott E. Carpenter 19
Communications Range - Geocasting
• Geocasting protocols:
• Reactive
• Reactive geocast protocols decide the next-hop forwarder at
each hop through a distributed contention phase among the
neighbors of the vehicle that generated the message.
• Proactive
• Proactive geocast protocols determine the message
forwarders before the effective message dissemination,
through the creation of a virtual backbone of vehicles inside
the VANET.
Copyright © 2013 Scott E. Carpenter 20
Vehicular Roadside Internet Access
• Challenges
– Load Balancing:
– Location Discovery:
– Security:
– Uninterrupted Roaming Facility:.
– Maximized Coverage Area:
Copyright © 2013 Scott E. Carpenter 21
Vehicular Roadside Internet Access (2)
• Integration Strategies
– Instantaneous link quality (ILQ) based relay protocol
– Utilize the vehicles location to estimate the ALQ for relay
selection
– A new opportunistic relay protocol for vehicular roadside AP
(from ORPVRAFC).
– Sparse deployment of roadside Wi-Fi.
• New metric for roadside Wi-Fi called contact opportunity, which
measures the fraction of distance or time that a user in vehicle is in
contact with some AP when moving through certain path. Use
empirical results from a measurement study
– Mob Torrent, an on demand user driven frame work for vehicles
which have high speed access to roadside Wi-Fi APs.
Copyright © 2013 Scott E. Carpenter 22
Vehicular Roadside Internet Access (3)
Copyright © 2013 Scott E. Carpenter 23
Security and Privacy
• Security
– Key issue is data authenticity (broadcast authentication)
• Public key infrastructure (PKI), using certificate authorities (CAs).
– Message authentication using Elliptic Curve Digital Signature
Algorithm (ECDSA)
– Large computational burden of digital signature verification
leading to exploration for alternatives.
• E.g. lightweight broadcast authentication, timed efficient stream loss-
tolerant authentication (TESLA)
• Privacy
– Tension between the receiver’s goal of strong message
authentication and the sender’s goal of strong privacy.
– Consideration for multiple pseudo-identifiers per vehicle
Copyright © 2013 Scott E. Carpenter 24
IEEE 1609.1 (Resource Manager)
• WAVE RM, acting like an application layer, allows
applications at remote sites to communication with OBU.
– Note: Processing, memory, and configuration management
requirements are removed from the OBU and thus application
independent.
Copyright © 2013 Scott E. Carpenter 25
IEEE 1609.1 (Resource Manager) (2)
• Typical data flow:
Copyright © 2013 Scott E. Carpenter 26
IEEE 1609.2 (Security Standards)
• Key features of WAVE security services:
– Provide authentication, authorization, integrity, confidentiality services.
– Designed to increase bandwidth and processing time by the minimum
amount consistent with the security requirements.
– Are not at a particular location in the stack, but may be called by any
functional entity on a WAVE device.
Copyright © 2013 Scott E. Carpenter 27
IEEE 1609.2 Security Mgmt. Services
• Security services:
– Certificate Management Entity (CME)
(CME-Sec-SAP) (CME-SAP).
– Provider Service Security Management
Entity (PSSME)
• Security processing services:
– Generate signed data
– Generate encrypted data
– Verify signed data
– Decrypt encrypted data
– Generate signed WAVE service
advertisement (WSA)
– Verify signed WSA on reception
– Generate certificate request
– Verify response to certificate request
– Verify certificate revocation list
Copyright © 2013 Scott E. Carpenter 28
IEEE 1609.3 (Networking Services)
• Specifies network and transport layer protocols and services that
support high-rate, low-latency, multi-channel wireless connectivity.
• Key services:
– LLC
– IPv6 / UDP / TCP
– WSMP
– WME
• Service requests
and channel access
assignment
• Management data
delivery
• WAVE Service
Advertisement
monitoring
• IPv6 configuration
• MIB maintenance
Copyright © 2013 Scott E. Carpenter 29
IEEE 1609.3 Channel Access Options
• Channel
access
options:
– Continuous
– Alternating
– Immediate
– Extended
Copyright © 2013 Scott E. Carpenter 30
IEEE 1609.3 Channel Access Assignment
• Example data flow for channel access assignment
Copyright © 2013 Scott E. Carpenter 31
IEEE 1609.4 (Multi-channel Operations)
• Channel coordination (OCBEnabled), per 802.11p
• MLME:
– Data Plane services
• Channel coordination
• Channel routing
• User priority
– Management services
• Multi-channel synchronization
• Channel access
• Vendor-specific action frames
• Other IEEE 802.11 services
• MIB maintenance
• Readdressing – Pseudonymity
Copyright © 2013 Scott E. Carpenter 32
IEEE 1609.4 Channel Coordination
• Data is
prioritized
according to
access
category
(directly
related to user
priority)
– Uses IEEE
802.11 EDCA
mechanism
per channel
for
prioritization
Copyright © 2013 Scott E. Carpenter 33
IEEE 1609.4 – Issues
• Channel congestion phenomenon following a channel
switch
– Synchronous channel switching
– IEEE 802.11 congestion control and error recovery
• Avoiding transmission at scheduled guard intervals.
Can be avoided by:
• a) Before delivering an MSDU to the PHY, the MAC issues a
PLME-TXTIME.request and the PHY returns a PLME-
TXTIME.confirm with the required transmit time.
• b) If the required transmit time exceeds the remaining
duration of the channel interval, the MSDU should be
queued in the MAC sublayer until a return to the proper
channel occurs.
Copyright © 2013 Scott E. Carpenter 34
Vehicle Infrastructure Integration (VII)
• Consortium: • Auto Mfg.
• Ford
• General
Motors
• Daimler-
Chrysler
• Toyota
• Nissan
• Honda
• Volkswagen
• BMW
• IT suppliers
• USDOT
• State DOT
• Professional
associations.
Copyright © 2013 Scott E. Carpenter 35
Communications Challenges
• Under VII, most of the road system will not
have radio coverage.
• Requires vehicles to store data, then forward later
• Receive data and store, present later (to user) at
opportune time.
• Locations for upload / download will be locations
where all vehicles are trying to utilize the system.
Copyright © 2013 Scott E. Carpenter 36
VII Trials
• Michigan, California.
• In mid-2007, a VII environment covering some 20 square miles
(52 km2) near Detroit will be used to test 20 prototype VII
applications
• Some auto-makers conducting their own trials.
Copyright © 2013 Scott E. Carpenter 37
VII Findings (Overall)
• Overall VII POC successful.
• However, some shortcomings in WAVE/DSRC
radio implementation.
• Majority of shortcomings result from the dynamic
nature of the mobile radio relative to the stationary
radio and to other mobile radios
Copyright © 2013 Scott E. Carpenter 38
VII Findings – DSRC, Communications
• DSRC • F‐DSRC‐1 Final range testing results showed solid radio
communications from RSE to OBE up to 1100 meters, with multipath
effects degrading communications at 660 meters, 850 meters, 900
meters, and 1,000 meters. These results also showed a link
imbalance with OBE to RSE communications only available up to 400
meters.
• F‐DSRC‐4 Testing showed that the DSRC standards do not
adequately address functionality for multiple overlapping RSE
coverage areas.
• F‐DSRC‐6 Communication quality was reduced by an “unbalanced link”
situation whereby the OBE would commence transmission of data after
coming in range of an RSE’s broadcast, but at a distance too far for the RSE
to receive the OBE’s data
• Communications Service • F‐COMM‐2 Management of network communications resources for
multiple simultaneous applications is more complex than expected
Copyright © 2013 Scott E. Carpenter 39
SAE J2735 (DSRC Message Set)
• IEEE 1609 do not provide for a standard API • Each application provider needs to develop custom
interfaces
• SAE J2735 is one such message set, providing
• Primary Message Types: • Basic Safety Message (BSM) – ex: Emergency
Electronic Brake Lights.
• Roadside Alert (RSA) is the message used in the various
traveler information applications, specifically in the
Emergency Vehicle Alert message used to inform mobile
users of nearby emergency operations.
• Probe Vehicle Message (PVM) is used by multiple
applications. Vehicles gather data on road and traffic
conditions at intervals.
Copyright © 2013 Scott E. Carpenter 40
Channel Allocation, Prioritization
• Suggested priority: • Safety of Life - Those Messages and Message Sets requiring immediate or
urgent transmission. Ex: Crash-Pending Notification.
• Public Safety - Roadside Units (RSUs) and On-Board Units (OBUs) operated
by state or local governmental entities that are presumptively engaged in
public safety priority communications (Includes Mobility and Traffic
Management Features). Ex: SPAT (Signal Phase and Timing), Electronic Toll
Collection, Heartbeat message.
• Non-Priority Communications - Fleet Management of Traveler Information
Services and Convenience or Private Systems. Ex: Off-Board Navigation
Reroute Instructions, Electronic Payments and other E-Commerce
applications.
Copyright © 2013 Scott E. Carpenter 41
Vehicle Safety Communications (VSC)
• Alternate consortium • Prior to VII
• Identified potential applications:
Communications
Application Requirement
Traffic signal violation warning V2I
Curve speed warning V2I
Emergency electronic brake light V2V
Pre-crash sensing V2V
Cooperative forward collision warning V2V
Left turn assistant V2I
Lane-change warning V2V
Stop sign movement assistant V2I
Copyright © 2013 Scott E. Carpenter 42
Intelligent Transportation Systems (ITS)
• The Intelligent Transportation Systems Joint
Program Office (ITS JPO) within the U.S.
Department of Transportation’s (U.S. DOT’s)
Research and Innovative Technology
Administration (RITA) • Responsible for conducting research on behalf of
the Department and all major modes to advance
transportation safety, mobility, and environmental
sustainability through electronic and information
technology applications, known as Intelligent
Transportation Systems (ITS)
• Current “active research”
• http://www.its.dot.gov/index.htm.
Copyright © 2013 Scott E. Carpenter 43
Key Challenges (1)
• Socio-Economic Challenges • The beneficial impact of VANETs on traffic safety
and efficiency must be shown
• Equipage penetration rate • The U. S. contains 4 million miles of roads and streets
with an estimated 300,000 signalized traffic lights and, as
of 2010, 250,272,812 registered vehicles. Only 1% of
roads are highways, though they carry 25% of all
vehicular traffic
• Assuming 40% of all vehicles will be equipped within the
next 15 years, at a nominal cost of $150 per unit in today’s
dollars, the total costs in today’s dollars to equip vehicles
would then be 250,272,812 cars x 40% x $150/car =
$15,016,368,720, or slightly more than $1B per year (in
today’s dollars)
Copyright © 2013 Scott E. Carpenter 44
Key Challenges (2)
• Technical Challenges • Accurate traffic modeling (e.g. taking into account human
reaction, or feedback loop).
• The need for adaptive transmit power and rate control
mechanisms for periodic one-hop broadcasts in dense traffic
• Security, privacy, and trust
• No communications coordinator can be assumed - distributed
control with a single, shared control channel.
• The potential for channel congestion (10 to 20 MHz range)
and multi-channel usage leading to synchronization problems.
• Dynamic network topology and vehicle mobility.
• Radio propagation issues and adverse radio channel
conditions from low antenna heights and attenuation /
reflection of moving metal vehicle bodies.
• Joint optimal transmit and power control is still an open issue
Copyright © 2013 Scott E. Carpenter 45
Simulation – Traffic Modeling
• Traffic Models • Microscopic
• Wiedemann car-following model (high fidelity)
• Nagel-Schreckenburg model (low fidelity)
• • Macroscopic
• Traffic Simulation • Commercial
• VISSIM
• AIMSUN
• Paramics
• Government • NGSIM (Federal Highway Administration)
• Research Community • SHIFT
• STRAW
• VanetMobSim
Copyright © 2013 Scott E. Carpenter 46
Traffic Simulation Challenges
• Key challenges: 1. Specifications of APIs for coupling traffic flow and
networking simulators
2. Modeling how drivers react to the additional
information provided by VANETs
3. Benchmark definitions to make simulation studies
and results comparable
4. Since traffic flow simulators do not typically model
accidents, accident models may also be needed to
represent real world vehicular dynamics.
Copyright © 2013 Scott E. Carpenter 47
Signal Modeling
• Key challenges: • Channel conditions
• Nakagami-m distribution was proposed to cover a wide range of potential
channel conditions
• Environmental factors (difficult to capture, often ignored in simulation) • Weather
• Surrounding buildings
• Traffic • e.g. large scale fading
• Receiver capability modeling
• Capture is a highly important capability for dealing with the one-channel
problem
• Modern chipsets are able to capture packets almost independently of the
order of their arrival.
• Network simulators often only provide less powerful capturing capabilities
that do not correspond to modern chipsets.
• Benchmarks
• With respect to simulation methodology, a set of standardized
benchmarks and test scenarios would be useful to make protocol and
model proposals comparable with each other.
Copyright © 2013 Scott E. Carpenter 48
Networking Simulation Architecture
Copyright © 2013 Scott E. Carpenter 49
Simulation Results
• Scenarios: • Open-air, static vehicles
• Control channel saturated for safety-critical applications when
the total offered traffic approached 1000 packets per second
(see chart)
• Urban setting (Washington, D. C.)
• Highway setting
Copyright © 2013 Scott E. Carpenter 50
Simulation Results (2)
• Ideal RSU spacing: 1000 – 1500 m
Copyright © 2013 Scott E. Carpenter 51
Other Challenges
• Data filtering and aggregation
• Fast and proper distribution
• Hardware/software compatibility
• Node densities
• Data security
• Distribution range
• Relative speed
• Mobility and handover
• Frame error rate
• Quality of service
• Hidden nodes
• Radio channel characteristics
Copyright © 2013 Scott E. Carpenter 52
Conclusions and Next Steps
• IVC research remains very active • Google Scholar search for “VANET” yields 852
articles thus far in 2013, 2048 articles in 2012.
• Only a few trials active in U.S.
• Standards seem in place • IEEE 802.11p
• IEEE 1609
• SAE J2735
• Simulation remains primary means for
evaluation of ideas • Difficult to capture many “real world” issues
• Many research opportunities remain in IVC.
Copyright © 2013 Scott E. Carpenter 53
Backup Slides
Copyright © 2013 Scott E. Carpenter 54
References References
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Copyright © 2013 Scott E. Carpenter 55
References (2) References
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Copyright © 2013 Scott E. Carpenter 56
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