Vehicular Networking Tutorial Presentation · PDF file6 Architectural components • RSU (RSE): Roadside Unit (Equipment) • OBU (OBE): Onboard Unit (Equipment) • Network Subsystem:

1

1

Vehicular Networking

Malathi VeeraraghavanProfessor

Charles L. Brown Dept. of Electrical & Computer Engineering

University of Virginia

[email protected]

Tutorial at IEEE ICC 2010

This work was carried out as part of a sponsored research project from the US DOT FHWA grant no. DTFH61-10-H-00001

2

Outline

• DSRC

• Standards– IEEE 802.11p, 1609.1-4

– SAEJ2735

• Equipment

• Testbeds and trials

• Research literature

• Summary

• Background on IEEE 802.11

2

Dedicated Short-Range Communication (DSRC)

• Channel allocation

• History

• Players

• Programs

• Use of DSRC– Architecture

– Applications

• CALM

3

US DSRC Channel allocation

• US FCC allocated band: 5.850-5.925 GHz

• 75 MHz band

• Safety margin: 5MHz at lower end

• Critical safety channel: High availability and low latency

4

CH 172 CH 174 CH 182CH 180CH 178CH 176 CH 184

Critical safety

High power safety

Service channels (SCH)

Service channels (SCH)

Control channel(CCH)

5.85

5.86

5.88

5.89

5.90

5.92

5.91

5.87

3

5

Worldwide ITS Spectrum AllocationsWorldwide ITS Spectrum Allocations

5.8 5.9(GHz)

ITU-R5.725 5.875

ISM Band

EUROPE5.795 5.815

0.902 0.928 5.85 5.925North America

JAPAN5.79- 5.81 5.83-5.85

Frequency

First Second(Additional)

5.77

DSRC Generation:

Talk by S. Oyama, ITS America Annual Meeting, April 2002, http://www.leearmstrong.com/DSRC%20Home/Standards%20Programs/World-

Wide/DSRC%20Standards%20World%20.htm

History

• 1991: US program called Intelligent Vehicle Highway Systems (IVHS)

• 1996: National Intelligent Transportation Systems Architecture (NITSA)– basis for Intelligent Transportation System (ITS)

• 1997: Intelligent Transportation Society of America (ITSA) petitions the FCC

• 1999: FCC granted the DSRC band for ITS

• 2002: ITSA recommends American Society for Testing and Materials (ASTM) standard that was based on 802.11 (1999 standard) – stable standard, and leverage economies of scale in chipset costs

• 2004: IEEE creates 802.11p task group

• 2007: IEEE 802.11p amendment published

• 2006-2007: IEEE working group 1609 releases high-layer standards

• CEN and ETSI European history: http://www.itsnorge.no/dsrc-workhsop-om-elektronisk-bompengebetaling-26-05-08?nid=6740&lcid=1044&iid=10786&pid=itsnorway-Artikkel-Filer.-20201

6

IEEE paper 2009 by R. Uzcategui and G. Acosta-Marum

4

Players (US)

• US Department of Transportation (US-DOT)– FHWA (Federal Highway Administration)

– RITA (Research and Innovative Technology Administration) Intelligent Transportation Systems

• State DOTs (e.g., VDOT: Virginia DOT)

• Industry organizations:– ITS-America, OmniAir

– e.g., OmniAir “offers third-party, independent verification and certification of DSRC standards compliance”

• Academic institutes– CA-PATH (California Partners for Advanced Transit and Highways – U. California, Berkeley)

– UMTRI (University of Michigan Transportation Research Institute)

– UVA Center for Transportation Studies (Virginia) 7

IntelliDriveSM (VII)

• The IntelliDriveSM program is a major US initiative of the Intelligent Transportation Systems (ITS) Joint Programs Office (JPO) at DOT’s Research and Innovative Technology Administration (RITA)

• Formerly known as Vehicle Infrastructure Integration (VII)

• http://www.intellidriveusa.org/8

5

Europe consortiums

• ERTICO - ITS EUROPE– multi-sector, public/private partnership pursuing the development and deployment of Intelligent Transport Systems and Services (ITS); http://www.ertico.com/

• CAR 2 CAR Communication Consortium– non-profit industrial driven organisation initiated by European vehicle manufacturers supported by equipment suppliers, research organisations and other partners; http://www.car-to-car.org/

• Transport for London – Congestion charging: http://www.tfl.gov.uk/assets/downloads/stage-3-final-report.pdf

9

Use of DRSC: Architecture

• V2V (Vehicle to Vehicle) and V2I (Vehicle to Infrastructure) communications

• Range up to 1000m

• Data rates from 6-27 Mbps

• Low latency ~50ms

• Security using public key infrastructure (PKI)

10From Booz Allen Hamilton 2008 Talk at ITSVA conference (Kandarpa)

6

Architectural components

• RSU (RSE): Roadside Unit (Equipment)

• OBU (OBE): Onboard Unit (Equipment)

• Network Subsystem: – SDN: Service Delivery Node

– ENOC: Enterprise Network Operations Center

• Backhaul network: RSE to SDN

11

Use of DSRC: Applications

• Safety– NHTSA March 2010 report: projected fatalities in 2009: 33,963; 2008 number: 37,261

– “In 2008, there were an estimated 5,811,000 police-reported traffic crashes, in which 37,261 people were killed and 2,346,000 people were injured” NHTSA Traffic Safety Facts 2008 Data - http://www-nrd.nhtsa.dot.gov/Pubs/811162.PDF

– 2000: Direct economic costs of vehicle crashes are $230.6 billion per year (same report)

• Efficiency/mobility– Urban surface transportation congestion is estimated at $80 billion per year (src: Kapsch)

– Signal optimization

– Route guidance systems (avoid congestion)

• Commercial: Tolling/parking payment, fleet control, park&ride, electronic license plate

12

7

ISO Effort: CALMCommunication Access for Land Mobiles• http://www.isotc204wg16.org/concept

• Standardization effort

• “Support multiple access technologies including cellular 2nd generation, cellular 3rd generation, satellite, infra-red, 5 GHz micro-wave, 60 GHz millimetre-wave, and mobile wireless broadband”

• With DSRC: safety and mobility applications come first

• To support entertainment services, mobile stations need to be able to communicate over longer durations, and therefore handoffs are necessary

• “One of the essential features of the CALM concept is the ability to support heterogeneous handover, also referred to as media independent handover (MIH) between various access technologies supported by ITS stations.”

13

14

Outline

• DSRC

� Standards– IEEE 802.11p

– IEEE 1609.1-1609.4

– SAE J2735

• Equipment



• Summary


8

WAVE (Wireless Access in Vehicular Environments)

• Standards:– IEEE 802.11p for PHY and MAC

– IEEE 1609 for higher layers

• Why is a new variant 802.11p needed?– Mobile endpoints – high vehicular speed

– Greater range: 1000 m (vs. 38-46m for 802.11b)

15

IEEE 802.11p

• 802.11p is specified as an amendment to 802.11

• Major differences with 802.11

16

802.11b 802.11p

Network acquisition Association Fast

Latency Low (for safety applications)

Frequency band 2.4 GHz 5.85-5.925 GHz

Environment Indoor, low-mobility

Outdoor high-mobility

Number of channels 3 channels 7 channels, each 10MHz

Physical layer 20 MHz per channel

10 MHz per channel

DSRC Frequently Asked Questionshttp://www.intellidriveusa.org/documents/DSRC%20FAQs.pdf

9

Key difference in IEEE 802.11p

• Communication can occur Outside the Context of a BSS – variable called dot11OCBEnabled is set to true– No authentication procedures (required in all 802.11 stations)

– No association procedures (required in all BSS with an access point in 802.11)

17

Communicating outside the context of a BSS

• Stations whose dot11OCBEnabled is true simply transmit and receive on a channel known a priori– e.g. SAE J2735 Basic Safety Messages sent in 1609 WAVE Safety Message on Control Channel (CCH)

• Timing and Information frame: new management frame– allows stations to exchange management information: supported rates, QoS parameters

18

10

Other changes

• MAC layer: Since EDCA Parameter Set (AIFSN, CWmin, CWmax, TXOP for each AC) is sent by AP in Beacon in BSS, in OCB operation, use default values in MIB variable dot11EDCATable

• Minor changes in information elements

• Interesting: No changes in security section of 802.11 – handled in 1609.2

19

Annex I

20

802.11b: maximum EIRP: 36 dbm (4W)

11

IEEE 1609 WAVE Standards

• 1609.3: network and transport layers

• 1609.4: multi-channel operation

• 1609.2: security services

• 1609.1: resource manager

21

WAVE protocol stack

• Fig. 2 of Roberto A. Uzcátegui, Guillermo Acosta-Marum, “WAVE: A Tutorial,” IEEE Communications Magazine, May 2009, pp. 126-133

22

12

1609.3 outline

• Networking services

• WAVE system operations

• WBSS creation and application registration– WAVE announcement frame

– WAVE Service Advertisement (WSA)

• IPv6

• WAVE Safety Message Protocol (WSMP)

23

Networking services 1609.3

• Data-plane services– Logical link control (LLC)

– IPv6

– UDP/TCP

– Wave Short Message (WSM) Protocol (WSMP)

• Management-plane services

24

13

WAVE system operations

25

Operation without a WAVE Basic Services Set (WBSS)

Operation with a WAVE Basic Services Set (WBSS)

Only WAVE safety messages sent on the Control Channel (CCH)

Persistent WBSSprovider MAC sends WAVE announcements about WBSS and its applications in every CCH interval

Non-persistent WBSS

with WBSS: WSMs or IP over SCH

WME: important piece

• WAVE Management Entity�WBSS management

�Application registration

�IPv6 configuration

– MIB maintenance

– Channel usage monitoring

– Received Channel Power Indicator (RCPI) monitoring

26

14

Creation of a WBSS

• A WBSS is initiated at the request of an application

• A WAVE announcement frame is sent on the CCH announcing the new WBSS with its applications

• WAVE announcement frame– Wave service advertisement (created WME)

– Wave service information element (MAC frame body)

• When a WBSS is formed, its channel, rate and transmission power are announced in the announcement frame

• When there is no WBSS, this information needs to be passed down to the MAC layer in each WSM message

27

Provider and User

• Any device (OBU or RSU) can be provider or user

• Provider: generates announcements about a WBSS and associated applications

• User: joins a WBSS on receipt of an announcement

28

15

Creation of a WAVE announcement frame

29

IEEE 1609.3, page 12

WAVE announcement frame (sent on CCH)

Creation of a WAVE announcement frame

30


System parametersare loaded

16

31


What the WME constructs

WAVE service advertisement

• WAVE service advertisement is constructed by WME from information provided by applications

• Application specifies:– Provider Service Identifier (PSID)

– Provider Service Context (PSC)

– Channel Info

– WAVE routing advertisement (optional)

• WAVE announcement frame carries information about– Multiple applications

– Multiple service channels

32

17

WAVE service advertisement: PSC

• Provider Service Context– Application priority

– Channel number of the SCH for the WBSS on which this application is being supported

– Optional parameters:

o IPv6 address of the device hosting the application

o Service port number (16-bit): like TCP port number

o Provider device addressing (present if IP is being used): indicates if the device sending the WSA is the also the one hosting the application

o MAC address of the device hosting the application if different from the device sending the WSA

33

WAVE service advertisement: Channel info

• Channel Information– SCH channel number

– Adaptable: whether rate is minimum and transmit power level is maximum, or whether rate/power are fixed

– Data rate

– Transmit (tx) power level

34

18

WAVE service advertisement: WRA

• WAVE routing advertisement: about infrastructure internetwork connectivity (all mandatory if WRA is present)– Router lifetime: duration for which Default gateway information is valid

– IpPrefix: IPv6 subnet ID

– Prefix Length: subnet mask

– Default Gateway: IPv6 address of a gateway inside infrastructure that provides connectivity to the Internet

– Default Gateway MAC address

– Separate Gateway MAC: if 0, default gateway is not the device transmitting the WSA

– Primary DNS

– Secondary DNS (optional)

35

IPv6 background

• RFC 4291: IPv6 Addressing Architecture– Three types of unicast addresses

• Global

• Site local

• Link local

• RFC 4862: IPv6 Stateless Address Autoconfiguration

• RFC 4861: Neighbor Discovery for IP version 6 (IPv6)– Router advertisement format

36

19

Global-use IPv6 (unicast) address format

• Global address– significant difference from IPv4

– interface addresses are derived from a global routing prefix/subnet ID (effectively an identifier for a “network”) and Ethernet MAC address

37

n bits m bits 128-n-m bits

Interface IDsubnet IDglobal routing prefix

Interface ID: a1:67:89:ff:fe:9f:ae:b4

MAC address: a1:67:89:9f:ae:b4

insert two octets 0xff and 0xfe

Stateless autoconfiguration

• Prefixes are obtained from Router Advertisements– which are sent on all-nodes multicast address

– Prefix information option field contains prefix information

• Nodes receiving router adv. use their own interface MAC address with the received prefix to create their global IPv6 address

• Use Neighbor solicitation messages to detect duplicate addresses

38

20

Local-use (unicast) address formats

• Link-local: when no routers are present

• Site-local: for addressing inside a site without a global prefix

39

10 bits 54 bits 64 bits

Interface IDsubnet ID1111111011

10 bits 54 bits 64 bits

Interface ID01111111010Link-localaddress

Site-localaddress

IPv6 usage in WAVE(Section 6.4 of 1609.3)

• OBU calculates its global IPv6 address via stateless configuration– IpPrefix is received in WRA of a WAVE announcement frame rather than in a Router Advertisement message (note: need for DNS and gateway)

• RSU’s IPv6 is configured by a network administrator

• If an OBU is a provider of an IP based service, it only uses link-local addresses (Section 6.1 of 1609.3)

40

21

TCP or UDP

• “Most IP applications are expected to use UDP rather than TCP” - section 4.3.3.3 of 1609.3

• will probably not hold true – especially if entertainment applications are deployed

• 1609 standards defined to operate over ONLY (?) 802.11p (see Sep. 2009 update later in this section), but CALM activities may lead to this?– recall CALM discussion about handoffs for long-duration sessions

41

WSMP

• WAVE Short Message Protocol

• Time-sensitive, high-priority

• Sent directly in MAC/LLC frames

• Provider Service Identifier (PSID) used to determine the application to which WSM should be delivered at the destination

42

22

Without WBSS operation

• Only Wave Safety Message Protocol (WSMP) over the CCH

• There is no opportunity to send a WAVE announcement frame in which information about the channel can be sent

• So the WSM message format carries parameters about the selected channel

• A WAVE Safety Message (WSM) can be sent as soon as needed – e.g., an emergency brake event

43

WSM Version

Security type

Data Rate

ChannelNumber

Tx PowerLevel

Provider Service ID

WSM length

WSMData

0: unsecured1: signed2: encrypted

WSMPs can be sent on a SCH when operating within a WBSS

WSMP-to-UDP/IP forwarding(user applications)

• Interesting concept (Sections 5.5 and 6.1)– An application can reside off the WAVE device

– When WAVE device receives a WSM with a particular PSID for an application that has pre-registered as being off the device, the WAVE device will encapsulate message payload in UDP/IPv6 packet and forward it to the application

– Application should have registered its IP address and port in the UserServiceInfo part of the WME MIB (see Appendix A.1, page 62: contains PSID, IPv6 address and service port)

• Why interesting: allows vehicle OBU to interconnect with Internet endpoints without itself running IP – new internetworking mechanism

44

23

Multichannel operation 1609.4

• Four services– Channel routing: controls routing of data packets from LLC to appropriate channel

– User priority service: 8 levels of user priority mapped to the four AC classes of 802.11e MAC access (EDCA) – to be studied in depth later

�Channel coordination service: coordinates channel intervals (channel sync) so that data packets are sent on the correct channels

�MSDU data transfer service: LLC header Ethertype lookup to determine if WSMP or IP and give priority to WSMP 45

Channel coordination service

• Channels vs. intervals– CCH and SCH channels (see DSRC allocation)

– CCH and SCH intervals• Guard intervals between them

• Sync interval: CCH interval + SCh interval

• Timing information provided in WSIE (payload of a WAVE announcement frame) – UTC time

46

From IEEE 1609.4, Section 6.4

24

Can an OBU just stay on CCH?

• Yes.

• For devices remaining on CCH during the SCH interval, low-priority frames (user priority 3 or less) may be transmitted at any time

• All devices must monitor CCH during CCH intervals during which all high-priority (user priority 4 and higher) WSMP messages will be sent

47

From IEEE 1609.4, Section 6.4

Can an RSU offer applications on multiple SCHs simultaneously?

48

Shie-Yuan Wang et al., The GUI User Manual for the NCTUns 6.0 Network Simulator and Emulator, Sept. 2009

• nctu-ns, a popular simulation tool seems to imply yes.

25

Multichannel operation 1609.4

• Channel coordination management, section 8, states– “A WAVE device will be a member of only one WBSS at a time.”

– WAVE device: “A device that contains an implementation of the WAVE protocol standards, including IEEE Std 1609.2, IEEE P1609.3, IEEE Std 1609.4, and IEEE P802.11p.” - So, it could be RSU or OBU

• This means each device will only switch between one SCH and CCH

• Each RSE operated only one service channel in the Detroit POC (Booz Allen Hamilton Jan 09 report)

49

Single-channel vs. multi-channel devices

• Multi-channel devices are not required to be synchronized to operate on SCH as long as they conform to the requirements of monitoring the CCH during the CCH interval and to ensure transmission of high-priority CCH messages

50

From IEEE 1609.4, Section 8

26

MSDU Data Transfer

• In data-plane, 1609.4 sits between LLC and MAC, and in control-plane has MLME extension above MLME layer – see WAVE protocol stack

51

Frames

Management frames:WAVE announcement – CCH only

Data frames

WAVE Short Messages (WSM) :CCH and SCH

IP: SCH only

MSDU data transfer

• CCH data transfer– Only WSMP messages are allowed (IP not permitted)

• SCH data transfer– OBUs listen to WAVE announcements

– User-provider relation established

• Data transfer services– Since multichannel operation sits between LLC and MAC, it has to pass LLC to/from MAC service primitives

52

27

Security

• 1609.2: Security services

• 1609.2 Annex F: Types of attacks

• European-funded Secure Vehicular Communications (SeVe-Com) project (http://www.sevecom.org)– Good treatment of anonymity

• Also see “Threats to Security in DSRC/WAVE”– Paper by Christine Laurendeau and Michel Barbeau

– http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.70.4238&rep=rep1&type=pdf

– GPS spoofing

53

1609.2: Security Services

• Message types– Unsecured

– Signed

– Encrypted

• Algorithms– ECDSA (Elliptic Curve Digital Signature Algorithm)

– Hash algorithms: SHA-224 and SHA-256

– Asymmetric: ECIES (Elliptic Curve Integrated Encryption Scheme) used to transport symmetric key

– Symmetric: AES

54

28

Specific uses of secured messages (Section 8)

• Secured WSAs carried in WAVE announcement frames– Signed message

– Security Footer carries the signature field, timestamp (avoid replay attacks)

– Security Header carries WSIE certificate of signer (and/or certificate chain)

• Support for fragmentation– Some data such as CRLs or updated root certificates could be too large to fit in a single transmission

55

Specific uses of secured messages

• Secured WSM– Security type field in WSM header

• 0: unsecured; 1: signed; 2: encrypted

– SignedMessage structure:• signer: keying material (certificate, certificate chain) and hash algorithm

• unsigned message

• signature (digital signature itself)

• Security manager:– maintain root certificate sore and the CRL store

56

29

Certificate requests

• Applications may send WAVECertificateRequest messages over the air – Uses UDP/IP

• WAVECertificateResponse message sent

• Certificate Signing Request (CSR):– request by an entity to a CA to be issued with a certificate

• CSR signing certificate: a certificate used to sign a CSR

57

Threat model(1609.2 Annex F)

• Four classes of attackers:– Class 1: Has transmitter/receiver but no keying material.

– Class 2: Has a valid OBU or RSU.

– Class 3: Has extracted the keying material from an OBU or RSU, allowing them to either pretend to be that OBU or RSU in multiple locations simultaneously, or force the revocation of that keying material.

– Class 4: Insider at an organization with security administrative functions (HSM manufacturer, CA, vehicle manufacturer, government, etc.).

58HSM: Hardware Security Module

30

Threats(1609.2 Annex F)

• Basic Safety Message (BSM)– forge BSMs causing traffic disruption

• signing BSMs prevents this attack

– attacker tracks a vehicle

• Tolling– vehicle masquerading as a toll plaza to trick another vehicle into paying the first vehicle’s toll

– eavesdropping on credit card information

– eavesdropper uses static identifiers as cookies to track vehicle

– insider attacks to forge tolling tags

59

Threats contd.(1609.2 Annex F)

• General Internet access– future versions will require OBUs to change MAC address and IP address frequently to avoid being tracked

– IPsec considered best• 802.11i link-layer security cannot be used because 802.11p does not use Associations

• TLS and DTLS (Datagram TLS) do not protect all data over the IP link

• Long-lived IP sessions– Since system is not designed for handoff of IP sessions from one RSU to another, long-lived IP sessions happen when you’re stationary

– Less of a risk from tracking

60http://securityinnovation.com/cryptolab/pdf/WIR-104-Whyte.pdf

31

Threats contd.(1609.2 Annex F)

• Roadside e-commerce– Phishing: direct trafficto fake website to gather credit card info

– Eavesdropping to get credit card info

– Replaying an order to get goods at original driver’s expense

– Using static identifiers like cookies to track the vehicle

• Counter measures– Use DTLS to reduce eavesdropping, replay and tracking

– Authenticate the server DNS address in the PST (Provider Service Table) and check this against the DNS name in the server’s DTLS certificate to reduce the threat from phishing

61

V-HIP

• Vehicular Host Identity Protocol (V-HIP)– Select RSE's are capable of maintaining a data session as vehicles pass from 1 RSE to another (Booz Allen Hamilton Jan 09 report)

– Used in Detroit POC trial

62

32

Sevecom project(Anonymity)

• Hardware Security Module (HSM) in vehicles and RSUs– all private keys stored in HSM, and all private key operations are executed in HSM

– digital signature generation and decryption of encrypted messages

– public key operations are executed in OBU

• Pseudonymous authentication (for security and anonymity)– Each OBU has multiple certified public keys (pseudonyms)

– An OBU uses each pseudonym for a short period of time, and then switches to another, not previously used, pseudonym.

63Papadimitratos et. al, IEEE Comm. Mag, Nov. 2008

Sevecom project

• Long-term identity (public-private key pair)

• Short-tem identities (with pseudonyms)

• How to distribute Certificate Revocation Lists (CRLs) to multiple RSUs?

• Secure beaconing: – send “beacon” i.e., BSM, encrypted in the current pseudonym’s private key;

– send along with it the pseudonym certificate with the public key,

– CA signature can be verified in other OBUs, which have preinstalled CA’s public key

• Root CA public keys preloaded in OBUs64

33

Sevecom project

• Short-term identity– HSM generates a set of N (public key-private key pairs)

– Sends N public keys to its CA using its long-term ID to authenticate itself to the CA

– CA returns signed certificates with N pseudonymns

– Each pseudonym has• identifier of the CA, the lifetime of the pseudonym, the public key, and the signature of

the CA, BUT no information about the identity of the vehicle

– Once a pseudonym is discarded by OBU, cannot go back

– Non-overlapping lifetimes for pseudonyms

– Do pseudonym refills

– Since CA knows relation between pseudonyms and actual identity, authorized parties can obtain this information if required

– For further anonymity, vehicle obtains short-term credentials from foreign CAs when a vehicle enters foreign domain; foreign CA can verify identity with home CA

65

1609.1 Resource Manager

Resource Manager (RM) multiplexes the communications of multiple remote applications, called RMAs, each communicating with multiple OBUs, which run RCPs

66

• RM: Resource Manager

• RMA: RM Application

• RCP: Resource Command Processor

34

Main purpose

• “RM concept reduces the complexity of the OBUs freeing them from the requirement of executing applications onboard the vehicle”

• RMAs control OBU resources– read/write memory

– user interfaces

– specialized interfaces to other onboard equipment

– optional vehicle security devices

– All resources are mapped into the memory space of the unit

– RM commands and responses defined to allow RMAs to read/write this memory space

67IEEE paper 2009 by R. Uzcategui and G. Acosta-Marum

Update on IEEE 1609

• Talk by T. M. Kurihara, Chair, IEEE P1609 Working Groups

• September 21, 2009• https://mentor.ieee.org/802.11/dcn/09/11-09-0093-03-000p-ieee-p1609-wg-staus-report.ppt

• Note: P1609 family of standards are intended to operate with IEEE P802.11p, Wireless Access in Vehicular Environment (WAVE) and is the wireless communication system component of the U. S. Department of Transportation Intelligent Transportation Systems (ITS) Program and the Vehicle Infrastructure Integration (VII) Initiative using 5.9GHz Federal Communication Commission (FCC) allocated wireless spectrum for North America.

• Also discusses CALM

68

35

PROGRAM OF WORK(slide from Kurihara’s talk)

• P1609.0, WAVE – Architecture (PAR approved December 2006) • IEEE Trial-use Standard 1609.1TM-2006, WAVE - Resource

Manager• IEEE Trial-use Standard 1609.2TM-2006, WAVE - Security

Services for Applications and Management Messages• IEEE Trial-use Standard 1609.3TM-2007 WAVE - Networking

Services• IEEE Trial-use Standard 1609.4TM-2006, WAVE - Multi-channel

Operations• IEEE Standard 1455TM-1999(2006), IEEE Standard for Message

Sets for Vehicle/Roadside Communications• IEEE P1609.5, WAVE – Communication Manager (PAR approved

September 2008 until 2012)• IEEE P1609.11, WAVE – Wireless Access in Vehicular Environments

(WAVE) - Over-the-Air Data Exchange Protocol for Intelligent Transportation Systems (ITS) - Electronic Payment Service (PAR open until 2013)

70

Outline

• DSRC

� Standards– IEEE 802.11p

– IEEE 1609.1-1609.4

� SAE J2735

• Equipment



• Summary


36

Society of Automotive Engineers (SAE)J2735 standard

• Overview

• Example messages and parameters

• Annex A: Priorities

• Annexes B & C: Basic Safety Message

• Annex D: Probe Vehicle Data

71

SAE J2735 standardDSRC Message Set Dictionary• Specifies a set of– messages, which contain

– data frames, which contain

– data elements (smallest entities)

• Messages can be used on– DSRC

– other wireless technologies

• Annexes are useful

72

Nov. 2009 version

37

Examples of messages

• Ala Carte Message

• Basic Safety Message

• Probe Vehicle Data

• Probe Data Management

• Intersection Collision Avoidance

• Traveler Information Message

• Emergency Vehicle Alert

• Signal Request Message

• And 7 others – total of 15 message types73

Examples of Data frames

• Snapshot: one or more status elements captured and sent in Probe Vehicle Data message– FullPosition Vector (also a data frame)

– VehicleStatus (also a data frame)

– VehicleSafetyExtension (also a data frame)

74

38

FullPositionVector data frame

• Consists of data frames and data elements– Data frames

• DDateTime

• TransmissionandSpeed (transmission state and speed)

• PositionalAccuracy

– Data elements• Longitude

• Latitude

• Elevation

• Heading

• etc.

75

VehicleStatus data frame(not a complete defn.)

• ExteriorLights, LightbarInUse

• WiperStatus (dataframe)– data elements: WiperStatusFront, WiperStatusRear, WiperRate (front rate and rear rate variables)

• BrakeSystemStatus (data frame)– BrakeAppliedStatus, AntilockBrakeStatus, StabilityControlStatus, etc.

• SunSensor, RainSensor, AmbientAirTemperature, AmbientAirPressure

• Steering (data frame), AccelerationSet4Way

• VehicleData (VehicleHeight,VehicleType, etc.)

76

39

VehicleSafetyExtension data frame(just one example data element)

• EventFlags – Hazard Lights: are active

– Stop Line Violation: vehicle anticipates it will pass the line without coming to a full stop before reaching it

– ABS: system active and active > 100ms

– Traction control: active and active > 100ms

– Hard braking, flat tire, disabled vehicle, air bag deployed, etc.

77

Annexes A-J

• Annex A: Priorities

• Annexes B & C: Basic Safety Message operations

• Annex E: Probe Data Message operations

• Others cover operations related to Traveler Information, Emergency Vehicle, Roadside Alerting messages, etc.

78

40

Priorities

• J2735 layer: Message priority

• 1609.4: User priority

• 802.11: MAC priority

• J2735: User priorty is referred to as “transmission priority”

• Display priority: which message to display on driver’s screen first

• 1609.3: Application priority79

Message priority(1 to 7)

Urgent

< 10 msec from 10 to 20 msec > 20 msec

Importance

Safety of life 7 5 3

Public safety 6 4 3

Non-priority 2 1 1

80

• Safety of life:

• Crash Pending Notification: 7

• Basic safety message: 5

• Public safety:

• Signal Phase and Timing: 6

• Lane Coordination: 4

• Wave Service Annoncement: 3

• Non-priority

• Electronic payments: 2

• Area map: 1

EXAMPLES

41

1609.4 User priority

• 8 levels to support safety and non-safety applications

• IEEE 802.11 REVma has a mapping between user priority and MAC access categories

• This appears in Annex A of J2735

• Caveat: not sure if it is the same– 1609.4 cites Table 20.23 of IEEE Std 802.11 (REVma not available in the public domain)

81

From Annex A of J2735

1609.4 User Priority Access Category

7 Highest AC3

6

5 AC2

4

3 AC1

0

2 AC0

1

82

0 is higher than 2 and 1 due to historical IEEE development evolution as a way to add a new “lowest priority”

42

User priority to transmission access categories

• MAC layer does this mapping

• Internal contention first won by an AC, and then external contention

83

From IEEE 1609.4

MAC: Enhanced Distributed Channel Access (EDCA)

• Arbitration inter-frame space (AIFS): The minimum time interval between the wireless medium becoming idle and the start of frame transmission

• Contention Window (CW): Random number of time slots to wait

• Transmit Opportunity (TXOP): Maximum duration in msec; If 0, it permits only one MSDU.

84

43

Medium Access

• If free: wait for AIFS and send

• If busy: wait for AIFS and then CW85

MAC transmission priorities

• AC_VI: video

• AC_VO: voice

• AC_BE: best effort

• AC_BK: background86

From Stibor et. al (2007) paper

• Random number of slots where slot time is 8µs

• TXOP = 0 for all cases

• Actual parameter set more general for CW

44

Actual standard

87

From IEEE 1609.4

BSSID from WAVE announcement frame’s MAC header is used by OBU to associate with a WBSS. In 802.11 Association Response message, EDCA Parameter Set for use on this BSS is passed from RSU to OBU; For CCH, this is predetermined - see IEEE 802.11p

Mapping of J2735 Message priority to 1609.4 User priority• Annex A says:

– “The main purpose of the message priority is to serve as input to the protocol at the next lower layer in a transmitting device. If the lower layer supports prioritization, it might use message priority in determining how to treat a given message.”

– “In particular, the similarity between the message priority scale (1 to 7) and the IEEE 1609 User priority scale (0 to 7) does not imply that a simple mapping is appropriate.”

88

45

Annexes B and CBasic Safety Message (BSM)

• No WBSS formed

• Broadcasts – not unicast – no ACKs

• Frequent: every 100ms

• Support multiple applications– message content based on needs of applications many of which need same vehicle data

• BSM sent in WSMP (WAVE short message protocol)

• Sent on CCH: since no WBSS, only WSMPs can be sent on CCH

89

Annex E: Probe Data messages

• Probe data collected by vehicles at periodic intervals: 42 types of data!

• All collected snapshots are uploaded to RSU from OBU when vehicle is in range

• WBSS used

• SCH used

• WSMP used

• Single-attempt unicast

• RSU announces Provider Service Identifier90

46

Three types of snaphots

• Periodic– 4 seconds if speed is 20 mph (urban)

– 20 seconds if speed is 60 mph (rural)

• Event triggered– certain vehicle status elements change

• Starts and stops– when a vehicle starts or stops moving

91

Annex E: Prob Message Management

• Controls the production of snapshots by time or distance

• Modifies thresholds for triggered snapshots

• Modifies thresholds for start/stop snapshots

• Can be applied just to a random sample of vehicles

92

47

93

Outline

• DSRC

• Standards– IEEE 802.11p

– IEEE 1609.1-1609.4

– SAE J2735

� Equipment



• Summary


DSRC Product Vendors

• Kapsch – deployments in US VII Proof-of-Concept testbeds

• Savari - deployments in CA Path (SafeTrip-21) and Arizona E-VII

• Thales GEA

• Mark IV

• DSRC Consortium: Raytheon, Sirit, Transcore, Mark IV

• Genvict

• Arada

• CSSI

• TechnoCom and Card Access

• Econlite, Q-Free, IRD, EFKON

• Oki

• PhyChips – 5.8 GHz transceiver chip

• Denso Wireless Safety Units (WSUs) referred to by projects, but could not find product information readily on the Web

94http://www.researchandmarkets.com/reports/669645

48

Kapsch TrafficCom

• Products– Multiband Configurable Networking Unit (MCNU) R1551 – RSU

– eWAVE (Embedded WAVE) module: to create OBUs

– Incident detection system with video analysis

– Smart traffic sensor: highly-compact, intelligent video sensor for automatic detection and analysis for traffic safety applications

– Telematics platform: modular software system for implementing secondary telematics applications on basis of the Kapsch toll system

– WAVE starter kit: sophisticated hardware and software platform for application testing

• http://www.kapsch.net/US/EN/KTC/Pages/default.aspx

• Kapsch group has other products in GSM, access, etc.

95

Kapsch RSUMultiband Configurable Networking Unit

• Implements IEEE 802.11p and 1609.2-.4, SAE J2735

• Installed on traffic poles, street signs and highways

• Two high-speed Ethernet ports and two wireless interfaces

• Built-in GPS receiver

• Linux host – for application development

• Several radio bands supported (2.4-5.925 GHz range)

• IPv4 and IPv6 routing

• FTP and web servers

• Used in VII Proof-of-Concept testbeds

96

49

Kapsch applications

• Electronic Toll Collection

• E-Commerce

• Vehicle Safety/Crash Avoidance

• Emergency & Transit Vehicle

• Signal Preemption

• Traffic and Traveler Information

• Commercial Vehicle & Fleet Management

• Automotive OEM/Telematics

97

Savari MobiWAVETM OBU &StreetWAVETM RSU

• Linux systems

• DSRC/WiFi/3G radios, Ethernet & Bluetooth

• GPS receiver

• IEEE 802.11p, 1609.3 & .4

• Interoperable with Kapsch MCNU and Denso WSU, and Econolite, Siemens traffic controllers

• Touch-panel display

• Web based management

• SDK for application development

• Savari: supplier for the USDOT's California SafeTrip-21 and Arizona’s E-VII

98

50

Applications identified in Savari’s web site

• Enhanced Route Guidance and Navigation– Point of interest notification

– Food discovery and payment

– Map downloads and updates

– Location based shopping/advertising

– In-route hotel reservation

• Safety– Traffic signal violation warning

– Curve over-speed warning

– Emergency electronic brake lights

– Pre-crash warning

– Cooperative forward collision warning

– Left turn assistant

– Lane change warning

– Stop sign movement assistance

99

Savari applications contd.

• Electronic Payment– Toll collection, Open road tolling, Gas payment

– Drive through payment, Parking lot payment

• Fleet/Mobile Device– Asset management/tracking

• Mobile Router– In-Vehicle (bus, car, train) shared Internet connectivity

• Operations– Traffic congestion data collection

– Weather data collection

– Road surface conditions data collection

– Traffic signal priority for emergency and transit vehicles

– Parking spot locator

100

51

Thales GEA

• System– Controller

– 5.8 GHz DSRC Beacon

– Tag

– OBU

– RSU

101

http://ertico.webhouse.net/download/peace_documents/session2_thales.pdf

102

Mark IV

• OTTO on BoardTM

– OBU and RSU

• IEEE 802.11p, 1609.1/3/4, DSRC (5.9GHz)

• VxWorks operating system

• Supports IPv6, WSM, and non WAVE IP applications

• Intelligent Highway Vehicle Systems (IHVS) deployed in EZPass

• http://www.ivhs.com

52

Applications identified in Mark IV site

• In-vehicle public safety warnings and alerts

• Asset tracking and new e-commerce financial services

• Vehicle-to-roadside applications such as traffic signal coordination and prioritization

• Vehicle-to-vehicle communication for safety applications

• Internet data packet hopping

• Advanced ITS technologies such as platooning

• Roadway maintenance probes

103

DSRC consortium

• Raytheon, Sirit, Transcore, Mark IV

• Raytheon HTMS (www.raytheon.com/htms)– Highway Transportation Management Systems (HTMS)

– Electronic toll systems

• Sirit:– focussed on Automatic Vehicle Identification, Parking & Access Control, Asset Management and Supply Chain Systems

• Transcore:– RFID and vehicle tracking

– ITS system integration services

104

53

Genvict

• OBU: – SP2000, Sophia-i6, Sophia-V30

• RSU:– SHINE I, SHINE II, SHINE-G60, SHINE-P20

• 5.8GHZ microwave DSRC technology

• CEN standards

• http://www.genvict.com/en/product10.htm

105

Arada Systems

• Locomate™ - OBU and RSU

• Atheros’ MiniPCI AR5414 based WLAN chipset on the AR7100 platform (Atheros' wireless network processors)

• US DSRC

• 802.11p, 1609.3/.4

• Channel switch time <= 3ms

• http://www.aradasystems.com/Upload/ProductDataSheets/21_arada_datasheet_locomate_obu_final.pdf

106

54

CSSI

• Electronic toll collection DSRC Melodhy Armonhy Beacon

• 5.8 GHz CEN DSRC

• http://www.itsc.com.cn/files/image/20053291935270.pdf

107

Technocom and Card Access

• March 27, 2007 alliance formed

• Card Access: hardware for WAVE/DSRC

• TechnoCom: software solutions for WAVE/DSRC

• http://www.technocom-wireless.com/pdf/TechnoCom%20and%20Card%20Access3.26.07.pdf

108

55

Econolite

• Autoscope video detection system

• ASC/3 traffic controller: signal priority demonstration by combining with DSRC

• Data collection and management service

• http://www.econolite.com/docs/press/20051004_Intelligent_Intersection.pdf

109

Q-Free

• Q-Free – products and solutions for– Road user charging and traffic surveillance

– Applications• electronic toll collection for road financing, congestion charging

• truck-tolling, law enforcement and parking/access control

• Technologies– DSRC (tag)

– Automatic Number Plate Recognition (ANPR), also called Automatic License Plate Recognition (ALPR)

– GNSS (Global Navigation Satellite System)

• Based in Trondheim, Norway

• http://www.q-free.com110

56

Q-Free products

• MultiLane Free Flow (MLFF)– Uses ANPR cameras and DSRC tags

– Real-time control of all peripheral sensors of the roadside infrastructure

– Deployed in Australia, Portugal, Norway and Sweden

• Truck tolling– GNSS-OBUs and DSRC communications

– ANPR cameras for violations

• Congestion charging: to redistribute traffic

• Road user charging: return on investment

111

Q-Free products

• Traffic surveillance

• Operational Back Office (OBO): collect events from infrastructure, processes, charges customers

• GNSS, Global Navigation Satellite Systems: truck tolling with less infrastructure

• Video Tolling: with cameras rather than tags/beacons - high performance solutions with very low initial investment and path to interoperability

112

57

International Road Dynamics (IRD)

• Traffic data collection systems

• Sensors: in-road, on-road, non-intrusive

• Toll Treadle Systems

• Vehicle Weighers

• Traffic control safety

http://www.irdinc.com/products

113

International Road Dynamics (IRD)

• Traffic control safety systems– Lane Merger system

• Creates a dynamic no-passing zone

– Travel Messenger• Real-time information system to keep drivers informed

– Speed Manager• Variable Speed Limits

– Overheight Vehicle Detection

– Under Vehicle Surveillance System

– Tire Deflator114

58

Efkon Business Units

• ITS payment systems

• Radio communications for critical applications (public safety)

• Plaza based toll turn key systems

• Satellite applications

• T,TT - Transport, Traffic Telematics– Toll and ETC Systems

– Operations

– Traffic Telematics (ISO-CALM products and high level SAT solutions)

– Traffic Law Enforcement Systems (Red light and speed violations, WIM)

– AFC-Automated Fee Collection System

– Parking and Access

– Traffic Management

• Services: tolling contract in Ireland

• Products: OBUs

115

Oki Electric

• Oki DSRC technology

• Management System of Parking Lot by Monthly Contract

• Management System of Employee Parking Lot

• Management System of Exclusive Parking Lot for the Physically Disabled

• Pay Parking Lot System for Stores

• Gate System

• Self Service Gas Station Payment System

• CRM System

• http://www.oki.com/jp/SSC/ITS/eng/dsrc_prkidxe.html

116

59

117

Outline

• DSRC


– IEEE 1609.1-1609.4

– SAE J2735

• Equipment

� Testbeds and trials


• Summary


US Testbeds

• VII Proof of Concept (POC) Test– MI VII testbed (Detroit POC)

– NY VII testbed

– CA VII testbed

• SafeTrip-21 (started 2008)

• Europe and Japan testbed listing

118References provided in literature survey document

60

119

VII Project Overview• VIIC members

– BMW, Daimler, Chrysler, Ford, Honda, Nissan, GM, VW, Toyota

– Develop VII technologies to implementation readiness, validation through Proof of Concept (POC)

• Infrastructure side is supported by Booz Allen Hamilton subcontracted by the US DOT– Install RSEs in Detroit Test Environment– Setup and support VII network operations– Develop VII network services for testing during the POC

Kapsch (Moring) 2008 talk

120

Kapsch Project Participation• Detroit Vehicle Infrastructure Integration (VII) Proof of Concept (POC)

– 2007-2008 installation and operation

– Kapsch supplies MCNU (RSU) and WAVE radio, protocol, security, application; integration, test, program management services

• New York VII demonstration

– ITS World Congress in New York, Nov 2008

– Kapsch supplies MCNU units and WAVE software, system planning and engineering services

• California VII testbed

– At PATH Berkeley

– Kapsch supplies MCNU and WAVE protocol software

• CVIS

– V2V and V2I communication applications

– Kapsch supplies radio modules and protocol software

Kapsch (Moring) 2008 talk

61

POC Development Test Environment (DTE)• 55 Road-Side Equipment (RSE) Sites

(11 freeway, 44 arterial)• Over 45 Square Miles Covered

Booz Allen Hamilton (Kandarpa) 2008 Talk & Kapsch (Moring) 2008 talk

• 75 Center-Line Miles of Roadway

• Multiple Backhaul Communications

Detroit Backhaul Communications

• A communication link between the Detroit SDN and each RSE will be installed in Detroit – termed Backhaul Communications

• Different Backhaul Communications Technologies Used:– WiMax: 19 sites (6 Mbps)– Wireline: 20 sites (T1)– 3G: 16 sites (850 kbps)

• Data streams from all RSEs will be aggregated at the SDN

• Network Users will interface with the SDN through an Access Gateway (providing the necessary security protection)

Michigan DTE - SDN

AT&T managed services (aggregation

layer)

AT&T Wireline Service

WiMAX Service

ANode 1

Node 2

Sprint

EV-DO rev A Service

G. Krueger, MI DOT 2007 talkand Jan. 09 BAH report

62

POC Application Name LeadTraveler Information

Booz Allen

Signal Timing Optimization

Ramp Metering

Weather Information

Corridor Management: Planning Assistance

Corridor Management: Load Balancing

In-Vehicle Signage

VIIC

Off-Board Navigation

Make Payment for Parking

Make Payment for Toll

Vehicle Situation Indication (Heartbeat)

Traffic Signal Indication (SPAT/GID)

Applications used for POC testing

From Booz Allen Hamilton 2008 Talk

Services deployed

• Advisory Message Distribution Service (AMDS): Enables “Network Users” to send SAE J2735 compliant Road Sign, Advisory, and Probe Data Management Messages to Vehicles.

• Probe Data Service (PDS): Enables the distribution of SAE J2735 compliant Probe Data from RSE to “Network User” subscribers. The RSE to OBE Interface is encrypted using Vehicular Datagram Transaction Level Security (V-DTLS), which was specifically designed for this application.

• Information Lookup Service (ILS): Enables Network Users to look up RSE IP, Location, Status, etc., information.

• Communication Service (Comms): Enables IPv6 communications between vehicles and Network Servers

124

From BAH Jan. 09 report

63

Services deployed Contd.

• Two VIIC developed apps, which may not be supported in the future:– Tolling: 1 RSE is capable of simulating a tolling transaction

– Signal Phase and Timing\Geographic Information Description (SPAT\GID): 1 RSE is connected to a Signal Controller and broadcasts Signaling information and a canned GID Map.

125

From BAH Jan. 09 report

Traveler Informationand Corridor Management Load Balancing Applications

All Applications exceptSignal Timing Optimization Application

Signal Timing Optimization ApplicationRamp Metering Application

Public Applications Testing Locations

Weather Information and Corridor Management

Planning Assistance Applications use the

entire DTE area


64

Next exit services, traveler information

Navigation, rerouting

ParkingSchool zone

TollingSpeed limit, icy bridge, curve ahead

Signal timing, EBL

Private Applications Testing Locations


Important issues noted

• G. Krueger, Michigan DOT 2007 talk– Privacy – new vehicle ID at each RSE and opt-in for many services

– Data available – new vehicle ID precludes Origin-Destination (O-D) studies

– Funding ($3-7B) and installation –250,000 RSEs in 2 years, OPEX (15% per year) - who pays?

128

65

VII National System Network Build Up Plans

CA

MI

VA

NY


From Kapsch 2008 talk

130

In-vehicle installation

Electronic Payment App Navigation Application

66

131

New York RSE installations


132

Manhattan RSE installations


67

133

Seen on the Street


134

11th Ave Coverage Testing @ 37th St.

68

135

VII Lessons

• Equipment built to trial-use standards met objectives– Functionality

– Performance

• WSMP is effective

• Provider Service ID, WAVE Service Advertisement, WAVE Router Advertisement are valid concepts

• Standards support inter-vendor interoperability

• A range of applications are supported

• Room for improvements and enhancements in protocols– e.g., inflexible service joining/leaving rules


VII Calif. Test Bed Infrastructure

•Access to 60 miles of Right-of-Way– Three, parallel, 20-mile long North/South routes: US 101; SR 82 (El Camino Real); and I-280

•14 Road Side Equipment (RSE) sites are installed and operating, with approved FCC licenses– Mix of freeway / intersection locations

•26 more RSE sites have been selected and surveyed– Installation of RSEs will continue through 2008

•Backhaul: wired (T1 lines) and wireless (3G cellular; WiMAX, Municipal WiFi) – Communications technology choice is site dependent

•Back End Data Servers– “Service Delivery Node” located at the 511 TIC in Oakland– IP-based; additional servers can be located anywhere

From Susan Dickey’s 2008 talk

69

VII California Test Bed

Southern Peninsula,San FranciscoBay Area


VII California Test Bed Applications

• Traveler Information (using 511)

• Electronic Payment and Toll Collection

• Ramp Metering

• Cooperative Intersection Collision Avoidance Systems (CICAS)

• Curve Over-Speed Warning

• Auto Industry Applications, such as Customer Relations and Vehicle Diagnostics


70

USDOT RITASafeTrip-21 Field Operational Test

SafeTrip-21 (Safe and Efficient Travel through Innovation and Partnerships for the 21st Century)

139

http://www.intellidriveusa.org/safetrip21/#

Connected Traveler($12.4M project, started Apr. 08)

140Bart Cima, IBI group, 2008 talk

71

California Connected Traveler Field Test Bed

• Networked Traveler– alerts regarding Safety, Trip Planning, Traffic Congestion

• Mobile Millennium– ability of GPS-equipped cellular phones to generate robust, quality probe data throughout the Bay Area

• Smart Parking– provide real-time transit and highway travel times to travelers en route to San

Francisco on Highway 101, in combination with parking availability at key transit stations

• Work Zone Management– work-zone-monitoring, portable, solar-powered device built into traffic cones or

barrels known as iConeTM to monitor traffic and wirelessly relays speed and queuing information to a web server.

• Signalized Intersection Delay Monitoring– generate real-time information for travelers along signalized streets, as well as to

provide delay data to system operators for signal retiming purposes

141


I-95 Corridor CoalitionField Test Bed

• $6.4 million public-private, started Nov. 2008

• Four elements:– Intercity Trip Planner

• evaluate long-distance trip planning capabilities

– Airport Ground Transport Travel Information• provide travelers at the Baltimore-Washington International Airport real-time information on ground transportation

– Public Traffic Map Displays• large displays installed in VA to display real-time nearby roadway traffic information

– Work Zone Management

142


72

EU and Japan testbeds

• European projects:– E-Safety: CVIS, SAFESPOT and COOPERS; http://www.ibtta.org/files/PDFs/Toulminet_Gwenaelle.pdf

– More projects listed in Car-to-Car Consortium web site: http://www.car-to-car.org/index.php?id=6&L=0

• Japan projects:– AHS, Advanced Safety Vehicle (ASV), Driving Safety Support Systems (DSSS)

– Smartway project, http://www.nilim.go.jp/japanese/its/3paper/pdf/060131trb.pdf

143

144

Outline

• DSRC


– IEEE 1609.1-1609.4

– SAE J2735

• Equipment


� Research literature

• Summary


73

Research literature surveyed

• Tutorial papers [4]

• Simulation platforms and tools [7]

• Simulation studies – mostly 802.11p [10]

• Experimental studies [2]

• Testbeds/trials [7]

• Vehicular Ad Hoc Network (VANET) routing [13]

• Transport protocols [3]

• MAC protocols [5]

• Security [2]

Total: 53

145

Summary

• DSRC

• IEEE 802.11p, 1609.1-4

• SAEJ2735

• Equipment

• Testbeds & Trials


• Background on 802.11

146

74

Background on IEEE 802.11

• Wireless LANs

• Popularly called Wifi

147

Version Frequency Rate Physical-layer

802.11b 2.4GHz 11Mbps FH and DS

802.11g 2.4GHz 54Mbps OFDM

802.11a 5 GHz 54Mbps OFDM

OFDM: Orthogonal Frequence Division MultiplexingFH: Frequency HoppingDS: Direct Sequence (spread spectrum)

148

Distributed Coordination Function (DCF) – basic mode

• This mode of 802.11 is a random access MAC• When a node needs to send data, it senses the medium. If idle, wait for a period of DIFS and if the medium is still idle after DIFS, send immediately.

• If when the medium is sensed it is busy; then– wait for medium to be idle for a DIFS (DCF IFS) period – then decrement backoff timer until

• medium becomes busy again; freeze timer, OR• timer reaches 0; transmit frame

– if two stations have their timers reach 0; collision will occur; for every retransmission attempt, increase the contention window (CW), idle period after a DIFS, exponentially; 2i –1 starting with CWmine.g., 7, 15, 31.

75

149

DCF mode transmissionwithout RTS/CTS

source

destination

other

DIFSData

AckSIFS

NAV

Defer access

DIFSCW

Random backoff time

Network Allocation Vector (NAV):The source computes time to transmit the frame as it knows the size and transmission rate. This value is placed in the “Duration field” of the 802.11 MAC header. Other stations use this value to set the NAV value, during which time they defer access of the me.RTS/CTS: Request to send/Clear to send

150

DCF MAC

• Send immediately (after DIFS) if medium is idle• If medium was busy when sensed, wait a CW after it becomes idle (because many stations may be waiting when medium is busy; if they all send the instant the medium becomes idle, chances of collision are high)

76

151

802.11b DS

• Takes a 1Mbps data signal and converts it into a 11 Mbps signal

• 11 channels in the 2.4Ghz band (5Mhz spacing)

• Channels separated by center frequencies at least 30Mhz apart can operate without interference

• If total bandwidth is only 83.5 Mhz, only three 802.11 LANs using DS can have overlapping cells

• FCC only allocates between 2412 and 2462

152

Ad-hoc vs. infrastructure based

• Ad-hoc– No fixed network infrastructure needed– A wireless endpoint sends and all nodes within range can pick up signal

– Each packet carries destination and source address

– How do you know addresses of nodes in your region?

• Infrastructure mode– Access point receives and relay packets

77

153

Infrastructure based architecture

• Independent BSS (IBSS): has no access point– adhoc mode; only wireless stations

• Infrastructure BSS defined by stations sending Associations to register with an access point

Distribution System (DS)

Basic Service

Set (BSS)

Access points (AP)

154

802.11 MAC frame format

Framecontrol

Duration/ID

Address1

Address2

Address3

Address4

Seq.control

Frame body FCS

40-2312666 6 222bytes

MAC header

Protocolversion

Type Sub-type ToDS

FromDS

MoreFrag

MoreData

Retry PwrMgmt

WEP Order

22bits 4 1 1 1 1 1 1 1 1

WEP: Wired Equivalent Privacy - encryption scheme FCS: Frame Check Sequence (for error detection, like CRC)

78

155

Field explanations

• Type/sub-type field indicates the type of message– Management:

• Association/Authentication/Beacon

– Control• RTS, CTS, CF-end, ACK

– Data• Data only, or Data + CF-ACK, or Data + CF-Poll or Data + CF-Poll + CF-ACK

CF: Contention Free mode: the access point polls one station after another

156

Field explanations

• To DS and From DSTo DS From DS Message

0 0 station-to-station frames in an IBSS;

all management/control frames

0 1 From AP to station

1 0 From station to AP

1 1 From one AP to another on DS

• More Frag: 802.11 supports fragmentation of data• More Data: In polling mode, station indicates it has more data to

send when replying to CF-POLL• RETRY is 1 if frame is a retransmission; WEP (Wired Equivalent

Privacy)• Power Mgmt is 1 if in Power Save Mode; Order = 1 for strictly

ordered service

79

157

Field explanations

• Duration/ID: Duration in DCF mode (used in NAV)/ID is used in PCF mode

• Address fields

To DS From DS Address 1 Address 2 Address 3 Address 4

0 0 DA SA BSSID N/A

0 1 DA BSSID SA N/A

1 0 BSSID SA DA N/A

1 1 RA TA DA SA

RA: Receiver Address TA: Transmitter AddressDA: Destination Address SA: Source AddressBSSID: MAC address of AP in an infrastructure BSS

158

Field explanations

• Sequence control– Sequence number remains the same for all retransmissions of a data unit

– Sequence numbers of all fragments of a data unit are the same– Fragmentation Threshold determines size of fragments– Maximum size of MAC frame payload is 2312 bytes– Not included in ACK frame

• Broadcast and multicast frames are not ACK’ed

Sequencenumber

Fragmentnumber

4 bits 12 bits

DurationFramecontrol

2 2

RA FCS

6 4 bytes

Sequence control field ACK frame

80

159

Features of 802.11 MAC protocol

• Supports MAC functionality (address fields)

• Error detection (FCS)

• Error correction (sequence numbers & ACK)

• Fragmentation (More Frag)

• Flow control: stop-and-wait

160

Registration

• Why should an endpoint register with the access point:– allows the access point to decide whether or not to send a frame on its wireless link based on the destination MAC address in the frame header

• Association, reassociation and disassociation

Documents

Vehicular Networking Tutorial Presentation · PDF file6 Architectural components • RSU (RSE): Roadside Unit (Equipment) • OBU (OBE): Onboard Unit (Equipment) • Network Subsystem: