Vehicle Networks

V2X communication protocols

Univ.-Prof. Dr. Thomas Strang, Dipl.-Inform. Matthias Röckl

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Outline

Wireless Access for Vehicular Environments (WAVE)

IEEE 802.11p

IEEE 1609.1-4

SAE 2735

Car-2-Car Communication Consortium & ETSI TC ITS

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Wireless Access for Vehicular EnvironmentsRationale

What was the motivation behind a vehicle specific WLAN? What prevented the existing IEEE 802.11-family from being adopted as is?

[Sou

rce:

Dai

mle

r/C2C

-CC

]

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09 Wireless Access for Vehicular Environments (WAVE)

IEEE 802.11p + 1609.x + SAE 2735

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Wireless Access for Vehicular EnvironmentsOverview

No. of layer

ISO/OSI ref model Data Plane Management Plane

7 Application e.g. HTTPWAVE

Application (Resource Manager)

4 Transport TCP/UDPWSMP

WAV

E S

tation Managem

ent Entity

WS

ME

3 Network IPv6

2bData Link

802.2 LLC

2a WAVE MAC MACManagement

1bPhysical

WAVE Physical Layer Convergence Protocol (PLCP) PHY

Management1a WAVE Physical Medium

Dependent (PMD)

IEEE 1609.4IEEE 802.11pLo

wer

Laye

rsN

etw

ork

Ser

vice

s

1609.1 Resource Manager1609.2 Security Services1609.3 Networking Services1609.4 Multi-channel operations

IEEE 1609.3IEEE 1609.2

Hig

her

Laye

rs

IEEE 1609.1

WAV

E S

tation Managem

ent Entity

WS

MEMAC

Management

PHYManagement

SAE J2735

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pRequirements

Changes in baseline 802.11 standards are required to:support longer ranges of operation (up to ~1000 meters), the high speed of the vehicles (up ~500 km/h relative velocities), the extreme multipath environment (many reflections with long delays (up to ~5 μs max excess)), the need for multiple overlapping ad-hoc networks to operate with extremely high quality of service, and the nature of the automotive applications (e.g. reliable broadcast) to be supported.

Based on: IEEE 802.11p & Tan (2008): Measurement and Analysis of Wireless ChannelImpairments in DSRC Vehicular Communications

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pOverview

IEEE 802.11p is based on:IEEE 802.11a PHY: OFDM modulationIEEE 802.11 MAC: CSMA/CAIEEE 802.11e MAC enhancement: message prioritization

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11p Communication entities

Communication between:roadside units and mobile radio units (Vehicle-2-Infrastructure),mobile units (Vehicle-2-Vehicle), orportable units and mobile units (Vehicle-2-Pedestrian)

Infrastructure:Roadside Units (RSUs)Gantries (e.g. tolling gantries)Poles, traffic lights, etc.

Mobile/Portable equipment:On-board Unit (OBU)

Based on IEEE 802.11p

Denso DSRC platform

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pVehicle-2-Pedestrian

[Source: www.OKI.com]

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pPedestrian?

IEEE 802.11p DSRC module

GPS receiver

Regular GSM phone

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

V2X frequency bands

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pFrequency band

U.S. FCC allocated 75 MHz band in 1999 for ITS

5.85

0

5.85

5

5.86

0

5.86

5

5.87

0

5.87

5

5.88

0

5.88

5

5.89

0

5.89

5

5.90

0

5.90

5

5.91

0

5.91

5

5.92

0

5.92

5

5.82

5

5.83

0

5.83

5

5.84

5

Uplink

Downlink

Ch 172 Ch 174 Ch 176 Ch 180 Ch 184Ch 182Ch 178

PublicSafety/Private

Public SafetyIntersectionsControl

Channel

PublicSafety/Private

PublicSafety/Private

Inter-sections

Control High Availability

Dedicated Public SafetyShort Rng

ServiceMedium Rng

Service

Shared Public Safety/Private

PublicSafety/Private

PublicSafety

Veh-Veh

40 dBm

33 dBm

23 dBm

Power Limit

Power Limit

Power Limit

44.8 dBm

Based on B. Cash (2008): North American 5.9 GHz DSRC Operational Concept / Band Plan

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11p Multi-channel

Control Channel (CCH):Broadcast communicationDedicated to short, high-priority, data and management frames:

Safety-critical communication with low latenciesInitialization of two-way communication on SCH

Service Channel (SCH):Two-way communication between RSU and OBU or between OBUsFor specific applications, e.g. tolling, internet accessDifferent kinds of applications can be executed in parallel on different service channelsRequires the setup of a WAVE Basic Service Set (WBSS – “Ad-hoc group”) prior to usage of the SCH

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pOperation modes

Without WAVE Basic Service Set (WBSS)

Operation modes

Safety-critical, low latency messages and control messages

Mainly broadcastOnly on CCH

With WAVE Basic Service Set (WBSS)

Two-way transactions (e.g. tolling, internet access)Required to use a SCHRequires initiation on CCHIn contrast to the Independent Basic Service Set (IBSS), WBSS does not require authentication and association procedures

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pPHY

OFDM-based modulation similar to IEEE 802.11aHalved channel bandwidth of IEEE 802.11a: 10 MHz channels

half data rate: 3-27 Mbpsdoubled symbol duration: 8.0 μs 10 MHz

156.25 kHz

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pPHY: Comparison to IEEE 802.11a

Longer guard period Less Inter-symbol InterferenceBetter resistance against multipath error

IEEE 802.11a IEEE 802.11pData rate 6, 9, 12, 18, 24,

36, 48, 54 Mbps3, 4.5, 6, 9, 12, 18, 24, 27 Mbps

Modulation BPSK OFDMQPSK OFDM16-QAM OFDM64-QAM OFDM

BPSK OFDMQPSK OFDM16-QAM OFDM64-QAM OFDM

Error Correction Coding Convolutional Coding with K=7

Convolutional Coding with K=7

Coding Rate 1/2, 2/3, 3/4 1/2, 2/3, 3/4

# of subcarriers 52 net 52 net

OFDM Symbol Duration 4.0 μs 8.0 μs

Guard Period 0.8 μs 1.6 μs

Occupied bandwidth 20 MHz 10 MHz

Frequency 5 GHz ISM band 5.850-5.925 GHzDedicated frequency band

Less Co-Channel Interference

Re-order of sub-carriersBetter multipath mitigation

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 802.11pMAC

Based on Distributed Control Function (DCF) with CSMA/CAMAC-level acknowledgements for unicast communication, but no acknowledgements for broadcast communication

unreliable broadcast communicationRTS/CTS is only used on SCHBecause of higher range, slot time and SIFS should be longer

Addressing:RSUs have a fixed 48-bit MAC addressOBUs generate a random MAC address upon start-up of the deviceIf a MAC address collision occurs the OBU automatically changes its MAC address

Prioritization based on IEEE 802.11e EDCA (Enhanced Distributed Channel Access), defined in IEEE 1609.4

IEEE 802.11a

IEEE 802.11p

Slot time 9 μs 13 μsSIFS time 16 μs 32 μsCWmin 15 15

CWmax 1023 1023

SIFS – Short Inter-Frame Space

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 1609.4Extension for multi-channel coordination

IEEE 1609.4 is a functional extension to IEEE 802.11e MAC to enable multi-channel coordinationFunctions:

Channel routingData buffers (queues)PrioritizationChannel coordination

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 1609.4 Channel Coordination

Each Universal Time Coordinated (UTC) second is split into 10 Sync IntervalsEvery Sync Interval is composed of alternating:

CCH Intervals: Every node monitors the CCH andSCH Intervals: Nodes can monitor one of the SCHs

All WAVE devices have to monitor the CCH during the CCH IntervalDuring the SCH Interval nodes may switch to a SCH (RX or TX)At the start of each UTC second the first Sync Interval beginsSynchronization is performed via GPS

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 1609.3Networking Services

IP-based communication:IPv6-based with optional:

Mobile IPv6 (MIPv6) andNetwork Mobility (NEMO)enhancements

UDP or TCP on transport layerTransmission on SCH only

Non-IP-based communication:Based on WAVE Short Message Protocol (WSMP)Transmission on CCH or SCH

No. of

layerData Plane

4 TCP/UDPWSMP

3 IPv6

2b 802.2 LLC

2a WAVE MAC

1b WAVE PLCP

1a WAVE PMD

CCH/SCHSCH

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

IEEE 1609.3WAVE Short Message Protocol (WSMP)

Networking protocol specifically designed for V2X communicationsWAVE Short Message (WSM)structure:

WSMP can use CCH and SCHDuring the SCH Interval low priority messages can be transmitted on CCH for stations that do not switch to a SCH, high priority frames and WAVE Announcement frames shall be transmitted during the CCH IntervalIn order to access a SCH, the nodes have to be member of the WBSSWBSS roles:

Provider: Initiates a WBSS by sending a WAVE AnnouncementUser: Joins a WBSS based on the receipt of the WAVE Announcement

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

SAE J2735Message Dispatcher

Based on: Robinson et al. (2006): Efficient Coordination and Transmission of Data for Cooperative Vehicular Safety Applications

Implementation specific Implementation specificcommon

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

SAE J2735Basic message set definition

SAE J2735: Dedicated Short Range Communication (DSRC) Message Set Dictionary

ASN.1 representation of message structuresHierarchical definition of messages and substructuresBasic message set is not so basic any more, i.e. comprehensive:

16 different message frames, which use54 different data frames, which are parametrized through 162 different data elements

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09 Car-2-Car Communication Consortium (C2C-CC)

&

ETSI TC ITS

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Car-to-Car Communication ConsortiumPartners

Partners

AssociateMembers

Dev.Members

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Car-2-Car Communication ConsortiumProtocol stack

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Car-to-Car Communication ConsortiumObjectives of the First Demonstration (October 2008)

Demonstrate thefunctionality of CAR 2 CAR Communication Consortium system with 5 selected use cases

Warning of road worksEmergency vehicleBroken down vehicleMotorcycle use case / intersection scenarioSituation Monitor

interoperability between different communication platforms9 vehicle manufacturers (Opel, BMW, Daimler, Volvo, Renault, Fiat, Volkswagen, Audi, Honda, …)4 communication supplies (NEC, Hitachi / Renesas, Delphi, Denso)1 after market supplier(Alpine)

impact of vehicle-to-x communication

Objectives

[Slid

e by

M. K

ranz

]

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Demonstration self-restrictedto just two message types: CAM and DEN

Demonstration of technology although notfully specified yet. Thus, as compromise, mask layer 3..6 (i.e. APP on top of LLC)

Cooperative Awareness Message (CAM)Type of Vehicle, Position, Speed, HeadingBroadcasted by all vehicles with 1 Hz

Decentralized Environment Notification Message (DEN)Type of Event, Region of EventBroadcasted by RSU or Vehicle

No. of layer Data Plane

7

Demo-APP

6

5

4

3

2b 802.2 LLC

2a WAVE MAC

1b WAVE PLCP

1a WAVE PMD

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Use Cases – Warning of Road Works

Construction sites and temporary maintenance working areas areaccident black spots:

Changed traffic flowMore traffic signs Lane width changes, lane merging, “stress”, and other factors

The CAR 2 CAR system informs the driver on the details of the situation well before entering the potentially dangerous area

Geographic extent and affected areaDuration of road worksReason of road works…

Use Case 1

[Slid

e by

M. K

ranz

]

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Use Cases – Emergency Vehicle (EV)

When it comes to situations affecting the safety of lives every minute and every second is crucial. Road users are obliged to make way forEmergency vehicles (EVs) like ambulances or police cars. Potentialproblems are:

Source of sirenCrossing emergency vehicles at “green” lightsDestination of emergency vehicle

The CAR 2 CAR system informs the driver about the location of the source of the sirenwhere the emergency vehicle is headingon what lane the emergency vehicle will be overtaking

only if the emergency vehicle is expected to cross his route

Use Case 2

[Slid

e by

M. K

ranz

]

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Use Cases – Broken Down Vehicle / Post Crash Warning

Accidents and break downs are dangerous for any involved orassisting person as well as for approaching vehicles. Problems are:

Line of sight obstruction, e.g. behind a curve or hill top or due to weather conditionsTimely warning of affected traffic participants

If a vehicle detects a incident based on emergency flasher status, crash sensors, or onboard diagnosis, it can use the CAR 2 CAR system toinform about the type and location of the incidentraise awareness and alertness to the traffic situationact as “modern warning vest”

Use Case 3

[Slid

e by

M. K

ranz

]

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Use Cases – Motorcycle Warning / Intersection Assistance

European In-depth motorcycle accident analyses highlights thathuman error, and more specifically not seeing the motorcycle comingor misinterpreting distance and speed is the primary cause ofaccidents involving motorcycles. Reasons are:

Motorcycles have a smaller silhouette and are easier to “overlook”Motorcycles do not have a crumble zone

The CAR 2 CAR system informs the drivers of the involved vehiclesabout the presence of other traffic participantsby sending a respective warning message if a crash is predicted

Use Case 4

[Slid

e by

M. K

ranz

]

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Car-2-Car Communication ConsortiumFocus and on-going discussions

Focus on vehicle-to-vehicle communication (well, focus get’s blurred more and more …)Multi-hopGeo-based addressing and routingDual-receiver concept:

Parallel reception on 2 channelsOptional: dual-transmitter

Simulation scenarios and scalability …

If you are lookingfor an interestingthesis topic in thisarea, contact me!

Lect

ure

Veh

icle

Net

wor

ks, T

hom

as S

trang

and

Mat

thia

s R

öckl

, WS

200

8/20

09

Car-2-Car Communication Consortium / ETSI TC ITSRelationship

European industrial development of V2X communication by C2C-CCCreated the European derivative of IEEE 802.11pStandardization by the European Telecommunications Standards Institute (ETSI) Technical Committee ITS

ETSI is the relevant European standardization body for telecommunication protocols

Transferring the standardization process from C2C-CC to ETSI TC ITS C2C-CC WGs act as preparatory platforms & discussion fora for ETSI TC ITS WGs.One critical issue with the transfer of standardization to ETSI are the ETSI voting rules, which may add a strong bias to the whole process