Inter-Vehicle Communications (IVC):

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

[email protected],

919-413-5083

mailto:[email protected]


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


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!”


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


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)


VANET Technologies

• DSRC typical

• Other technologies utilized, too.


VANET Exploration – A Brief History

• Recent:

– WAVE

• (IEEE 1609)

– VSC

• (completed)

– VII

• (completed)

– ITS

• (RITA, USDOT)


OSI vs. WAVE


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


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.


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


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.


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.


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!


Power Effects

• Increasing Tx power combats fading, but increases saturation.

• Controlling beacon load with distributed power control (TxPC)

increased probability of receipt.


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)


Channel Prioritization

• 4 access categories (per channel)

• Queues have different timer

settings.


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


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.


Vehicular Roadside Internet Access

• Challenges

– Load Balancing:

– Location Discovery:

– Security:

– Uninterrupted Roaming Facility:.

– Maximized Coverage Area:


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.


Vehicular Roadside Internet Access (3)


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


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.


IEEE 1609.1 (Resource Manager) (2)

• Typical data flow:


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.


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


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


IEEE 1609.3 Channel Access Options

• Channel

access

options:

– Continuous

– Alternating

– Immediate

– Extended


IEEE 1609.3 Channel Access Assignment

• Example data flow for channel access assignment


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


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


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.


Vehicle Infrastructure Integration (VII)

• Consortium: • Auto Mfg.

• Ford

• General

Motors

• Daimler-

Chrysler

• Toyota

• Nissan

• Honda

• Volkswagen

• BMW

• IT suppliers

• USDOT

• State DOT

• Professional

associations.


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.


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.


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


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


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.


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.


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


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.

http://www.its.dot.gov/index.htm


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)


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


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


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.


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.


Networking Simulation Architecture


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


Simulation Results (2)

• Ideal RSU spacing: 1000 – 1500 m


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


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.


Backup Slides


References References

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Documents

Inter-Vehicle Communications (IVC):