Vehicle Networks - STI Innsbruck | Research institute at the · PDF file ·...
Transcript of Vehicle Networks - STI Innsbruck | Research institute at the · PDF file ·...
Vehicle Networks
V2X communication protocols
Univ.-Prof. Dr. Thomas Strang, Dipl.-Inform. Matthias Röckl
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Outline
Wireless Access for Vehicular Environments (WAVE)
IEEE 802.11p
IEEE 1609.1-4
SAE 2735
Car-2-Car Communication Consortium & ETSI TC ITS
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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
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Dai
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-CC
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09 Wireless Access for Vehicular Environments (WAVE)
IEEE 802.11p + 1609.x + SAE 2735
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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
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IEEE 1609.1
WAV
E S
tation Managem
ent Entity
WS
MEMAC
Management
PHYManagement
SAE J2735
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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
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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
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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
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IEEE 802.11pVehicle-2-Pedestrian
[Source: www.OKI.com]
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IEEE 802.11pPedestrian?
IEEE 802.11p DSRC module
GPS receiver
Regular GSM phone
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V2X frequency bands
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IEEE 802.11pFrequency band
U.S. FCC allocated 75 MHz band in 1999 for ITS
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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SAE J2735Message Dispatcher
Based on: Robinson et al. (2006): Efficient Coordination and Transmission of Data for Cooperative Vehicular Safety Applications
Implementation specific Implementation specificcommon
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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
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09 Car-2-Car Communication Consortium (C2C-CC)
&
ETSI TC ITS
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Car-to-Car Communication ConsortiumPartners
Partners
AssociateMembers
Dev.Members
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Car-2-Car Communication ConsortiumProtocol stack
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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
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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
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2b 802.2 LLC
2a WAVE MAC
1b WAVE PLCP
1a WAVE PMD
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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
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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
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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
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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
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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!
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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