All Rights Reserved © Alcatel-Lucent 20102 |Protocols for V2V Networks| June 2010
Contents
Introduction
Vehicular Mobility Models
Wireless Access in Vehicular Environment (WAVE)
Inter-Vehicle Routing Protocols
Conclusion
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Introduction
Vehicular Ad-hoc Networks
Vehicle-to-infrastructure (V2I or I2V)
Vehicle-to-vehicle (V2V)
Application
Transportation safety
Transportation efficiency
User services
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Applications[1]
Transportation Safety
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Applications[1]
Transportation efficiency
Service to users
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Motivation & Background
Motivation
Simulation
The first step in development of protocols
Need to have mobility models for simulation
Background
Two perspectives to consider a mobility model
Macroscopic: considers traffic density, traffic flow, etc
Microscopic: focuses on the movement of each individual vehicle and on the vehicle behavior with respect to others
Simple Mobilitycan’t reflect real-world traffic !
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Realistic Mobility Model Components
Proposed concept map for the generation of realistic vehicular mobility models[2]
From Reference [xx]
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Realistic Mobility Model Components
Two fundamental blocks
Motion Constraints
Describes how each vehicle moves (its relative degree of freedom)
Traffic Generator
Generates different kinds of cars
Deals with their interactions according to the environment
Other blocks
Accurate/realistic topological maps, smooth deceleration and
acceleration, obstacles, attraction points, simulation time, non-
random distribution of vehicles, intelligent driving patterns
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Generating Mobility Models
Classification of vehicular mobility models[2]
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Synthetic Model
Based on mathematical models
Can be further separated into 5 classes
Stochastic: containing purely random motions
Traffic stream: based on hydrodynamic phenomenon
Car following: based on the motion of cars ahead
Queue: model roads as FIFO queues
Behavior: based on rules imposed by social influences
Major drawback: lack of realism towards human behavior
General Schemefor Car Following Models
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Survey-based Model
Important source of macroscopic mobility information
Use extensive statistics of people’s behaviors
Commuting time, lunch time, traveling distance, etc
Example) UDel Mobility Model
Based on major large-scale surveys
Provided by US department of Labor
Major drawback: survey/statistical data only able to providecoarse grain mobility
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Trace-based Models
Extracting generic mobility patterns from movement traces
Various measurement campaigns
CrawDaD, UMASSDieselNet, MIT Reality Mining, USC MobiLib, etc
Some drawbacks
Difficult to extrapolate patterns not observed directly by traces
An extrapolated model from motion traces for bus systems cannot be applied to the traffic of personal vehicles
Limited availability of vehicular traces
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Traffic Simulator-based Models
Use simulators that built on real traces or behavior surveys
Fine grain simulators developed for urban traffic engineering
PARAMICS, CORSIM, VISSIM, TRANSIMS, SUMO, etc
Some drawbacks
Can’t be used straightaway for network simulators (no interfaces)
Purchase of a license (commercial products)
Mobility Models and Network Simulators have been developed independentlySo, there is a need to bridge them !
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Isolated Mobility Models
Interaction between Network and Traffic Simulators
Pros
Independent developments in mobility and network modeling
Cons
Mobility must be generated prior to simulation
No interaction between them
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Embedded Mobility Models
Interaction between Network and Traffic Simulators
Pros
Both models natively and efficiently interacting
Cons
Poor quality of the (simplified) network simulator
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Federated Mobility Models
Interaction between Network and Traffic Simulators
Pros
Benefit from the best of both worlds (state-of-the-art mobility models with modern and efficient network simulators)
Cons
Both simulators need to be run simultaneously
Development of the interlinking interface
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Trium Vira in Realistic Simulation
Interaction between Network, Traffic, and Radio Propagation Simulators[2]
Realistic radio propagation and fading model
Quality of the radio channel between two vehicles significantly depends on the mutual mobility
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Motion Constraints Featuresin Major Vehicular Mobility Models[2]
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Features included by the Traffic Generatorin Major Vehicular Mobility Models[2]
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Background
ITSA (Intelligent Transportation Society of America)
FCC (Federal Communications Commission)
Grant in October of 1999
DSRC (Dedicated Short-Range Communications)-based ITS radio services
75 MHz of spectrum in the 5.85-5.925 GHz range
ASTM (America Society of Testing and Materials)
ITSA recommended the adoption of a single standard for PHY and MAC layers of
architecture and proposed one developed by the ASTM based on IEEE 802.11
IEEE
IEEE 802.11p (in 2004)
IEEE 1609 standards set
WAVE(Wireless Access in Vehicular Environments)
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Wireless Data Links[1]
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WAVE Standard Family
WAVE communication stack
Protocols Standard
Document
Purpose of the standard OSI model
layer numbers
WAVE PHY & MAC IEEE 802.11p Specifies the PHY & MAC functions required of an IEEE
802.11 device to work in the rapidly varying vehicular
environment
1 & 2
WAVE Architecture IEEE 1609.0 Describes the WAVE/DSRC architecture and services
necessary for multi-channel DSRC/WAVE devices to
communicate in a mobile vehicular environment
1 - 4
WAVE resource
manager
IEEE 1609.1 Describes an application that allows the interaction of
OBUs with limited computing resources and complex
processes running outside the OBUs in order to give the
impression that the processes are running in the OBUs
N/A
WAVE security
services
IEEE 1609.2 Covers the format of secure messages and their
processing
N/A
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WAVE Standard Family
WAVE communication stackProtocols Standard
Document
Purpose of the standard OSI model
layer numbers
WAVE networking
services
IEEE 1609.3 Provides addressing and routing services within a WAVE
system
2 - 4
Multichannel
operation
IEEE 1609.4 Provides enhancements to the IEEE 802.11p MAC to
support multichannel operation
2
Communication
manager
IEEE 1609.5 Specifies communication management services for WAVE
(To collect in a single document, the communication
management services previously included in 1609.3 and
1609.4 based on experience in use during the trial-use
period)
2 - 4
Electronic Payment
Services
IEEE 1609.11 Provides an open standard for the relevant interface in
DSRC based transaction systems, providing a common
interoperable service for device identity and payment
authentication, and payment data transfer
7
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General Terms
Terminologies
RoadSide Unit (RSU)
Operate only when stationary and support information exchange with OBUs
On-Board Unit (OBU)
Operate when in motion and support the information exchange with RSUs or other OBUs
Provider
Advertiser of a service
User
One that associates with a service
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General Terms
Terminologies
Control Channel (CCH)
A radio channel used for exchange of management frames and WAVE Short Messages
Service Channel (SCH)
Secondary channels used for application specific information exchanges
Persistent Service
One that is announced periodically, during each CCH interval
Non-persistent Service
One that is announced only when it is established
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General Terms
Terminologies
WAVE Management Entity (WME)
WAVE Routing Advertisement (WRA)
WAVE Service Advertisement (WSA)
WAVE Short Message (WSM)
WAVE Short Message Protocol (WSMP)
PSID (Provider Service IDentifier)
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IEEE 802.11[3]
Architecture
MAC
DCF (Distributed Coordination Function)
PCF (Point Coordination Function)
EDCA (Enhanced Distributed Coordinated Access)
Ad hoc network
Infrastructure network
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IEEE 802.11
Frame type
Management
Control
Data
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IEEE 802.11
DCF
CSMA/CA
Because stations are unable to listen while transmitting
Physical carrier sensing
–Analyze all packets
Virtual carrier sensing
–Duration field of request-to-send (RTS), clear-to-send (CTS)
Network allocation vector (NAV)
Inter-Frame Space (IFS)
–SIFS, PIFS, DIFS, EIFS
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IEEE 802.11
Authentication/association
Active/passive probing
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IEEE 802.11a[4]
IEEE 802.11a-1999 or 802.11a
An amendment to the IEEE 802.11 specification
A higher data rate of up to 54 Mbit/s using the 5 GHz
52-subcarrier OFDM (Orthogonal Frequency-Division Multiplexing)
Modulation TechniqueOFDM operating bands and channels
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IEEE 802.11e[5]
EDCA (Enhanced distributed channel access)
Contention-based part of HCF
Prioritized QoS
Packets with priority value
Mapping intoa corresponding ACs(4 Access Categories)
EDCA (MAC Layer)
Higher Layer
Priority Access category (AC) Designation
(informative)
Lowest
Highest
AC_BK Background
AC_BK Background
AC_BE Best Effort
AC_BE Best Effort
AC_VI Video
AC_VI Video
AC_VO Voice
AC_VO Voice
Channel access mapping (User priority Access category)
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IEEE 802.11e
EDCA
4 AC functions
▶ Own contention parameters
: CWmin, CWmax, AIFS, TXOP
Transmission attempt
▶ New Inter-Frame Space (IFS) for each AC- Arbitration Inter-Frame Space (AIFS)
- AIFS[AC] = SIFS + AIFSN[AC] ∙ SlotTime
Default EDCA parameter set
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IEEE 802.11p[6]
Purpose
Describe the functions and services that allow an IEEE 802.11TM-
compliant device to communicate directly with another such device
outside of an independent or infrastructure network
At PHY level
Adaptation of IEEE 802.11a radio
10 MHz wide channels (75 MHz of DSRC spectrum at 5.9GHz)
Improved receiver performance requirements
Improved transmission mask
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IEEE 802.11p
Outside the context of a BSS
Only if dot11OCBEnable is true
Set the BSSID field to the wildcard BSSID value
No authentication, association, data confidentiality services
Vendor Specific Action frame: one means for STAs to exchange management information prior to communicating data frames outside the context of a BSS
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IEEE 802.11p
Format of individual frame types
Management frames
Timing Advertisement frame format
Information Notes
Timestamp The value of the timing synchronization function (TSF) timer of a frame’s
source
Capability
Country Optional
Power Constraint Optional and may only be present if the Country element is present
Time Advertisement Optional
Extended Capabilities Optional
Vendor Specific One or more vendor specific information elements may appear in this
frame. This information element follows all other information elements
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IEEE 802.11p
Format of individual frame types
Management frames
Information elements
–Vendor Specific information element
–Time Advertisement information element
Element ID Length Organization Identifier Vendor specific content
Octets 1 1 j n-j
Element ID Length TimingCapabilities
Time Value (if needed)
Octets 1 1
Time Error(if needed)
1 10 5
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IEEE 802.11p
Format of individual frame types
Management frames
Information elements
– EDCA Parameter Set element
Default EDCA parameter set for STA operation if dot11OCBEnabled is true
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IEEE 1609.0 WAVE Architecture[7]
Purpose
Describe the architecture of the DSRC/WAVE operations currently
represented by the family of IEEE 1609 standards and IEEE 802.11p
References (selective)
ASTM E2213-03 - 2003
IEEE Std 1609.1-2006, IEEE Std 1609.2-2006, IEEE Std 1609.3-2007, IEEE
Std 1609.4-2006,
IEEE Std 802.2–1998, IEEE Std 802.11-2007, IEEE P802.11p/D6.0 – 2009
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IEEE 1609.0 WAVE Architecture
Objective of WAVE
Provide a networked environment supporting very high speed
transactions among vehicles (V2V), and between vehicles and
infrastructure components (V2I) or hand held devices (V2D) to enable
numerous safety and mobility applications
WAVE System Components
The purpose of the communication provided by WAVE is to provide the application access to resources of a remote peer in a consistent,
interoperable, and timely manner to meet the application requirements
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IEEE 1609.0 WAVE Architecture
Protocol Architecture
Note: The figure illustrates the relationship among the IEEE 1609 and
IEEE 802.11 standards (before adding Communication Manager (P1609.5)
and Over-the-air Data Exchange for e-Payment Systems (P1609.11)
project proposals.
A sending application must also provide the MAC address of the destination device, including the possibility of a group address
WSMs are delivered to the correct application at a destination based on the PSID
Time synchronization for channel coordination, processing service requests and advertisements
IEEE 1609.3 - WAVE Management Entity (WME)
IEEE 1609.4 - extensions to MLME
UDP / TCP
LLC
PHY
WAVE MAC
(including channel coordination)
Air
Inte
rfa
ce
IPv6
WSMP
Data PlaneManagement Plane
TSAP
PHY SAP
MAC SAP
LSAP
WSM SAP
WAVE Management
Entity (WME)WM
E
SA
P
MLME Extension
PHY Sublayer
Management Entity
(PLME)
WAVE Security
Services
SE
C
SA
P
MAC Sublayer
Management Entity
(MLME)
LSAP
ML
ME
X
SA
P
ML
ME
SA
P
PL
ME
SA
P
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IEEE 1609.0 WAVE Architecture
Channel Types
A single Control Channel (CCH) [default for WAVE devices]
Multiple Service Channels (SCH)
Communication Services
Applications may choose to send their traffic in the context of a WAVE
service or not
If use WAVE service, devices associated with a service tune to the designated SCH in order to exchange data
Otherwise, their communication options are limited to WSMs sent on the CCH
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IEEE 1609.0 WAVE Architecture
Device Roles
Provider
User
Priorities
A service priority level (application)
MAC transmission “user” priority (lower layers)
The MAC priority for WSM packets is assigned by the generating application on a packet-by-packet basis
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IEEE 1609.0 WAVE Architecture
• Channel Coordination
– Time & Frequency Resources
• Segmented to provide a range of communications options
– Management & high priority (e.g., safety) traffic on CCH
– General application traffic on SCHs
• WAVE channels (default for single-channel device)
– Coordinated based on intervals that are synchronized using a
common system time base, preferably generated by a global time
reference, e.g., Coordinated Universal Time (UTC) such as that
provided by the Global Positioning System (GPS)
• Synchronization
– Also required for security purpose
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IEEE 1609.0 WAVE Architecture
• Service Initiation– By a provider application via a request to the WME
• Provider Service Context (PSC)
• Persistence
• Destination MAC address of intended recipient device(s)
• The number of advertisement repetitions (for a persistent service)
• SCH to use
• Optionally, direct the WME to choose the best available SCH
– On receipt of a WAVE advertisement
• Checks whether the provider application indicated by the PSID in the advertisement is of interest to any user applications
• Tune the local device to the correct SCH at the correct time(set any other layer configuration appropriately to support the communications)
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IEEE 1609.0 WAVE Architecture
• WAVE System Operations
– Attention to interactions of the applications and the WAVE
Cf) The set of channels on which services may be established is contained in
the WME MIB (depending upon the regulatory domain in which the unit is
operating)
– Communications without a service
• WSMP on the CCH only
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IEEE 1609.0 WAVE Architecture
• WAVE System Operations
– Communications with a service
• WAVE Service
– Supported by time and frequency (channel) resources allocated at
some set of participating devices within communication range, in
support of one or more applications
– Initiated at the request of the application at one device (provider)
and announced on the CCH
• Two types of services
– Persistent
– Non-persistent
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Provider Service Table
WAVE Routing Advertisement
Timing Quality Information
IEEE 1609.0 WAVE Architecture
The WAVE Advertisement
A WAVE management frame
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IEEE 1609.0 WAVE Architecture
• SCH Communications
– Upon receipt of an indication from the WME informing it of the service
association
• An application (whether provider or user) is free to generate data packets
(WSM or IP) for transmission on the SCH
• Service termination
– Example reasons
• Completion of the application activity
• Loss of connectivity
• Local communication resources being used for higher priority services
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IEEE 1609.0 WAVE Architecture
Adding/subtracting applications from an advertisement
For a persistent service
Different sets of services may be offered over time on the same SCH (i.e., the contents of the announced Provider Service Table may be dynamic)
Time synchronization and channel coordination
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IEEE 1609.0 WAVE Architecture
• Addresses and Identifiers in WAVE
– MAC address (included in the service advertisements for portal)
• Unicast/Broadcast
• Multicast
– Permitted but not required
• MAC anonymity (not yet)
– IPv6 address (included in the service advertisements for service provider devices)
• Global/Link-local/Multicast
– Protocol (UDP/TCP)/Port (included in the service advertisements for service
provider applications)
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IEEE 1609.0 WAVE Architecture
• Addresses and Identifiers in WAVE
– Application identification using PSID and PSC (included in the service
advertisements for service provider applications)
• PSC
– Associated PSID and contain supplementary information
• PSID
– Also used by the receiving device to deliver received WSMs ti the
appropriate higher layer entity
• IPv6 Neighbor Cache
• Security consideration (not yet)
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V2V Routing Protocols
VADD & SADV
Moving Vehicles
Stationary Sites
Local broadcasting info-stations
Sensors
Hotspots
Delivery a message from mobile vehicle
to the fixed site besides street miles away
For delay tolerant applications (DTN)
Multi-hop forwarding through VANET
Assumptions)
1. A vehicle knows its own location via GPS,knows its neighbors’ location by beacon message.
2. Vehicles are equipped with pre-loaded digital maps → Road information and
traffic statistics available
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Vehicle-Assisted Data Delivery in Vehicular Ad-hoc Networks
Store, Carry and Forward
Use predictable traffic pattern and vehicle mobility to assist efficient
data delivery
Key issue
Select a forwarding path with the smallest packet delivery delay
Guidelines
Make the best use of wireless transmission
Forward the packet via high density area
Use intersection as an opportunityto switch the forwarding direction andoptimize the forwarding path
58 |Protocols for V2V Networks| June 2010
VADD[8]
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VADD
VADD: Three Modes
Intersection Mode
Optimize the packet forwarding direction
Straight Mode
Geographically greedy forwardingtowards next target intersection
Destination Mode
Broadcast packet to destination
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VADD
VADD Model
Find out the next forwarding direction
with probabilistically the shortest delay
Probabilistic Method
Estimate the expected delivery delayfrom current intersection to the destinationfor each possible forwarding directions
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VADD
Intersection Forwarding Protocol
Known the priority list of outgoing directions, check the available
carriers to ensure packet is forwarded to the preferred directions
Need to consider Location & Mobility
VADD Intersection Protocols
Location First VADD (L-VADD)
Direction First VADD (D-VADD)
Multi-Path D-VADD (M-VADD)
Hybrid VADD (H-VADD)
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VADD (basic)
L-VADD
D-VADD
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Simple Loop-free
Drawback
1. Vulnerable to Forwarding Loop
2. Negative on delivery ratio
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VADD (advanced)
MD-VADD
H-VADD
Try and Error
Try L-VADD first, switch to D-VADD/MD-VADD when L-VADD fails
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SADV[9]
Motivation
Performance of VADD under different vehicle densities
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Mean Packet Delivery Delay Packet Delivery Delayunder 100 Vehicles
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SADV
A Static-Node Assisted Adaptive Routing Protocol in Vehicular Networks
Improve the routing performance under low vehicle densities
Vehicle densities vary with time everyday
Gradual deployment of vehicular networks
SADV design
Deploy static nodes (can be embedded in traffic lights) at intersections to assist packet delivery
Prevent packets from being delivered through detoured paths
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SADV
A Static-Node Assisted Adaptive Routing Protocol in Vehicular Networks
Basic idea
A packet in node A wants to be delivered to a destination
The best path to deliver the packet is through the northward road
The packet is stored in the static node for a while
The packet is delivered northward when node C comes
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SADV
A Static-Node Assisted Adaptive Routing Protocol in Vehicular Networks
Static Node Assisted Routing
State Transition Diagram of the Intersection Mode
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SADV
A Static-Node Assisted Adaptive Routing Protocol in Vehicular Networks
Link Delay Update
Expected link delay are estimated based on statistical information
– Vehicle densities on the roads vary with time
– Vehicle density is quite stable during a period of time
Use static nodes to help get more accurate delay estimation
Multi-Path Data Dissemination
Multi-path routing has the potential to further decrease packet delivery delay
– Link delay estimation may not be very accurate
– Increase the chance of hitting a better path
Packets are delivered through multiple paths only at static nodes
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SADV
A Static-Node Assisted Adaptive Routing Protocol in Vehicular Networks
Performance of SADV under Different Vehicle Densities
Mean Packet Delivery Delay Packet Delivery Delayfor Individual Packets
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CAR[10]
Connectivity-Aware Routing in Vehicular Ad Hoc Networks
Key idea
Position-based routing protocol that is able to not only locate positions of destinations but also to find connected paths between source and destination pairs
These paths are auto–adjusted on the fly, without a new discovery process
Main features
Destination location and path discovery
Data packet forwarding along the found path
Path maintenance
Error recovery
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Conclusion
Other related technologies
Mobile IPv6, Mobile Networks (NEMOs), Delay and Disruption Tolerant Network (DTN), etc
Main challenges of VANETs
Technical challenges
Socio-economic challenges
Modeling
Mobility model (how to couple simulators)
Accident model (for safety-related studies)
Radio channel model
Packet reception capabilities of the receiving interface (ex. Capturing)
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Reference
[1] Papadimitratos, P. La Fortelle, A. Evenssen, K. Brignolo, R. Cosenza, S., “Vehicular
communication systems: Enabling technologies, applications, and future outlook on
intelligent transportation,” IEEE Communications Magazine, Vol. 47, Issue 11, 2009
[2] Harri, J., Filali, F., Bonnet, C., “Mobility models for vehicular ad hoc networks: a
survey and taxonomy,” IEEE Communications Surveys & Tutorials, Vol. 11, Issue 4, 2009
[3] IEEE 802.11TM-2007, Information Technology – Telecommunications and information
exchange between systems – Local and metropolitan area networks – Specific requirements
– Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specification,
June 2007
[4] IEEE WG, “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications: High-speed Physical Layer in the 5GHz Band,” IEEE 802.11 Standard, 1999.
[5] IEEE WG, “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications: Medium Access Control (MAC) Quality of Service Enhancement,” IEEE 802.11
Standard, 2005.
73 |Protocols for V2V Networks| June 2010
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Reference
[6] IEEE P802.11pTM D11.0 Draft Standard for Information Technology - Telecommunications
and information exchange between systems – Local and metropolitan area networks –
Specific requirements – Part 11: Wireless LAN Medium Access Control (MAC) and Physical
Layer (PHY) specification: Amendment 6: Wireless Access in Vehicular Environments
(WAVE), March 2010.
[7] IEEE P1609.0TM/D0.8 Draft Standard for Wireless Access in Vehicular Environment
(WAVE) – Architecture, May 2009.
[8] Jing Zhao and Guohong Cao, ”VADD: Vehicle-Assisted Data Delivery in Vehicular Ad Hoc
Networks ,” IEEE Transactions on Vehicular Technology, Vol. 57, Issue 3, May 2008.
[9] Yong Ding, Chen Wang, and Li Xiao, “A static-node assisted adaptive routing protocol in
vehicular networks,” ACM VANET 2007, Montreal QC, Canada, 2007.
[10] V. Naumov and T. R. Gross, “Connectivity-Aware Routing (CAR) in Vehicular Ad-hoc
Networks,” IEEE INFOCOM, Anchorage, Alaska, USA, 2007.
74 |Protocols for V2V Networks| June 2010