This document discusses collision avoidance in vehicular networks through vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication. VANETs use moving vehicles as nodes that connect to each other to form a mobile network for safety and services. The primary goals are safety measures by sharing location and speed between nearby vehicles. Challenges include frequent changes in network topology. V2V directly communicates hazards but has limited range, while V2I uses roadside units for longer-range connectivity but requires infrastructure installation. Current systems include commercial services and standards organizations working on VANET technologies and applications.

1. Collision Avoidance in Vehicular
Networks
Avanti Chimote
Charan Hebri
Kuppuraj Gunasekaran
Sandeep N L
Saravanan Sathananda Manidas

2. Vehicular Ad-hoc Networks(VANET)
• A Vehicular Ad-Hoc Network, or VANET is a technology that
uses moving vehicles as nodes in a network to create a mobile
network. VANET turns every participating vehicle into a
wireless router or node, allowing vehicles approximately 100
to 300 meters of each other to connect and, in turn, create a
network with a wide range.
• As vehicles fall out of the signal range and drop out of the
network, other vehicles can join in, connecting vehicles to one
another so that a mobile Internet is created.
• VANET is a subgroup of MANET where the nodes refer to
vehicles. Since the movement of Vehicles are restricted by
roads, traffic regulations we can deploy fixed infrastructure at
critical locations.

3. Vehicular Ad-hoc Networks(VANET)
• The primary goal of VANET is to provide road safety measures
where information about vehicle’s current speed, location
coordinates are passed with or without the deployment of
Infrastructure.
• Apart from safety measures, VANET also provides value added
services like email, audio/video sharing etc,.

5. Communication Types
• Vehicle to Vehicle (V2V)
• Vehicle to Infrastructure (V2I)
• Vehicle to Roadside (V2R)
Hybrid Models
• Vehicle to Vehicle (V2V) & Vehicle to Infrastructure (V2I)
• Vehicle to Vehicle (V2V) & Vehicle to Roadside (V2R)

7. VEHICLE TO VEHICLE
COMMUNICATION (V2V)
• Vehicle to Vehicle communication approach is most suited for
short range vehicular networks.
• It is Fast and Reliable and provides real time safety
• It does not need any roadside Infrastructure.
• V2V does not have the problem of Vehicle Shadowing in
which a smaller vehicle is shadowed by a larger vehicle
preventing it to communicate with the Roadside
infrastructure

8. VEHICLE TO VEHICLE
COMMUNICATION (V2V)
Challenges
• In V2V the connectivity between the vehicles may not be
there all the time since the vehicles are moving at different
velocities due to which there might be quick network
topology changes.
• The anonymity problem: The addresses of vehicles on
highways are unknown to each other.
• Periodic broadcasts from each vehicle may inform direct
neighbors about its address, but the address-position map will
inevitably change frequently due to relative movements
among vehicles.

9. VEHICLE TO VEHICLE
COMMUNICATION (V2V)
• It is the receiver’s responsibility to decide the relevance of
emergency messages and decide on appropriate actions.
• Location based broadcast and multicast are the proper
communication methods for collision avoidance in V2V
Communication.
• Without any roadside infrastructure, multihop forwarding
must be enabled to propagate the messages or signals
• Hence, V2V communication is not very useful in case of
Sparsely connected or low density vehicular networks.

10. VEHICLE TO VEHICLE
COMMUNICATION (V2V)
• Stringent delay requirement: A rear-end collision occurs when
the Available Maneuvering Time (AMT) is less than the
Needed Maneuvering Time (NMT).
• NMT is dominated by the driver’s perception response time,
which is determined by many factors, and therefore difficult
to change. To prevent a rear-end collision, a vehicle must
receive the Message or Signal sufficiently prior to the lead
vehicle’s initiation of deceleration to provide more AMT.

11. VEHICLE TO
INFRASTRUCTURE/ROADSIDE
COMMUNICATION (V2I/V2R)
• Vehicle to Infrastructure provides solution to longer-range
vehicular networks.
• It makes use of preexisting network infrastructure such as
wireless access points (Road-Side Units, RSUs).
• Communications between vehicles and RSUs are supported by
Vehicle-to-Infrastructure (V2I) protocol and Vehicle-to-
Roadside (V2R) protocol.
• The Roadside infrastructure involves additional installation
costs.

12. VEHICLE TO
INFRASTRUCTURE/ROADSIDE
COMMUNICATION (V2I/V2R)
• The V2I infrastructure needs to leverage on its large area
coverage and needs more feature enhancements for Vehicle
Applications.

13. CURRENT WORKS IN VANETS
• Dash Navigation, Inc. a start-up in Sunny Valley, CA
started offering a service in 2009 called The Dash Driver
Network that allows drivers to broadcast their location and
speed in exchange for receiving updated traffic information
compiled from other vehicles in the network.
• This system is centralized and relies on wireless internet
connectivity which is not widely available on roads and
highways around the globe. Because the collecting entity is a
central, trusted location, privacy concerns are mitigated.

14. CURRENT WORKS IN VANETS
• The CAR 2 CAR communication Consortium , a non-
profit organization initiated by European vehicle
manufacturers with the objective of improving road traffic
safety and efficiency published in 2007 a manifesto in which it
proposes standards for V2V and V2I communications among
other things.
• In 2008, The European Union deployed systems relying on
V2V and V2I communications by reserving a radio frequency
across the EU for vehicle applications aiming at enabling co-
operative systems between carmakers.

15. CURRENT WORKS IN VANETS
• The Google Driverless Car is a project by Google that
involves developing technology for driverless cars. The system
combines information gathered from Google Street View with
artificial intelligence software that combines input from video
cameras inside the car, a LIDAR sensor on top of the vehicle,
radar sensors on the front of the vehicle and a GPS position
sensor attached to one of the rear wheels that helps locate
the car's position on the map. Google anticipates that the
increased accuracy of its automated driving system could help
reduce the number of traffic-related injuries and deaths,
while using energy and space on roadways more efficiently.

16. InVANET(Intelligent Vehicular Adhoc
Network)
• Incorporating intelligence into a VANET to
improve safety
• Makes use of V2V and V2R communication
• Make intelligent inferences about traffic incidents
• Facilitate easy and effective communication
between vehicles with dynamic mobility

17. InVANET Goals
• Improve traffic safety and comfort of driving
• Minimize accidents, traffic intensity, locating
vehicles
• Up-to-date traffic information
• Intersection Collision warning
• Local danger warning
• Weather information

18. Technologies Used
• Sensor technologies(Infra-red sensing/Video and Camera Image
Perception/RADAR/gyro sensor/inertial sensor), process data
through mathematical algorithms to come up with a virtual
understanding of the vehicle environment
• In-vehicle digital maps and positioning
technologies(GPS/WiFi/WiMax) as sensing systems to accurately
identify the vehicle position and interpret the environment
• If there is a gridlock/high traffic density detected by a roadside
infrastructure then the roadside system can broadcast the
information to all its nodes/vehicles
• In turn using the DTN capabilities of VANETs, the information can be
trasmitted to other vehicles heading towards this junction.
• Likewise, it can convey to the incoming vehicles other paths,
depending on a centralized system co-ordination of finding non-
traffic routes at that point of time.

19. InVANET Functionality
• Each vehicle equipped with WiFi/WiMax device acts as a node
• Unique ID and IP address for each vehicle
• Each node can communicate with any other node
• Any vehicle can register its identity to a roadway WAP
• Information provided by the vehicles directly to the WAPs
• Collective information stored by the WAPs at a dynamic server
database

20. Communication Methodologies
GPS for location identification
• Information retrieval units in VANETS
• Location information is important to calculation of distance
and velocities in VANETS
• Cameras and RADARs have some drawbacks like corners of
invisibility

21. Communication Methodologies
Advantages of GPS
• GPS provides global co-ordinates for every object under
interest
• Using GPS location, the velocity of the vehicle can be found
with a certain level of accuracy
• When the node/vehicle enters the range of the roadside
infrastructure, the GPS device on the vehicle sends it location
to the infrastructure
• The roadside system can then calculate the velocity based on
timely communication of location from the nodes

22. Communication Methodologies
Advantages of GPS (Contd.)
• Since GPS uses satellite communication, we can assume that,
given the resources of GPS available, the information is
available anytime.
• Using GPS co-ordinates we can overlay different maps over it
to get some other meta information
• Other value-added services such as nearest stores, gas station
etc can be found

23. Communication Methodologies
Disadvantages of GPS usage in VANETs
• Since GPS uses satellite communication for its working and
hence will have transmission delays.
• Since collision avoidance is a critical real-time task, we need a
technology which performs better in real-time.
• So such problems can be addressed using assistance from
other technologies
• RFID assisted GPS is one idea investigated in such an area.

24. Communication Methodologies
Disadvantages of GPS (Contd.)
• Since GPS uses satellite communication, we can assume that,
given the resources of GPS available, the information is
available anytime.
• Using GPS co-ordinates we can overlay different maps over it
to get some other meta information
• Other value-added services such as nearest stores, gas station
etc can be found
• The main problem with absolute positioning is distortion and
interference in wireless channel
• Also, for collision avoidance application absolute positioning is
not required and only relative positioning is sufficient

25. GPSense Car Platforms

26. Dedicated Short Range
Communication (DSRC)
• Challenges in VANET:
• Changing topology due to mobile nodes
• Routing / Broadcasting with reliability
• Avoid collisions
• Critical response time for alerts
• Sparse or Dense traffic
• No prior control messages
• Security
• Integrity and Authenticity

27. Dedicated Short Range
Communication (DSRC)
• VANET Active Safety of Passengers and more reliable
• 802.11p Add wireless access to vehicular networks and
implements OSI stack
• Wireless Protocol with Licensed band of 5.9GHz, 7
channels, Range of 1000m, Data rate 6 to 27Mbps
• Mainly used in communication of
1) Vehicle to Vehicle
2) Vehicle to Roadside

28. Dedicated Short Range
Communication (DSRC)
Extended from 802.11 Standard
• Extension to 802.11
• Implements message Priority
Scheduler which is required multi-
channel coordination
• Implemets CSMA/CA
• Extension to 802.11a
• Has 10MHz Channel Bandwidth
• Timing, Frequency and data rate
parameters are configurable
MAC Layer
Physical Layer

29. Channel Allocation in DSRC
• 1 Control channel – For Alert Messages
• Free from interference of other devices
Streaming Video
Single Channel Bandwidth
Alert for collision
6 Service Channels
1 Control Channel for Alerts

30. Security in DSRC
• Scheduler in every OBU
• Pre-emptive policy for
Higher Priority Messages
• Each OBU has a valid
certificate issued by
CA(Certification Authority)
based on unique license plate
registration
• Based on Digital signature
sent by OBU, using Public key
decryption message is verified

31. Non-GPS Mechanisms
• One alternate solution to GPS is the Global Navigation
Satellite System (GLONASS). It is a radio-based satellite
navigation system. This is in operation with global coverage
and of the same precision as GPS, but the disadvantages of
GPS still hold good for GLONASS.
• The instability of satellite based systems, make us think about
alternative technologies which will accurately describe a
vehicle's position.
• Map Matching (using Geographic information systems) where
a vehicle's position is being identified using some fixed point
in map like "university library", "Shands hospital". One can
then calculate the distance after a vehicle has passed the
point. The main disadvantage is loss of accuracy.

32. Non-GPS Mechanisms
• Distributed Relative Ad-hoc positioning: Here if any one of the
vehicles has GPS, the others can relative calculate the distance
using the GPS enable vehicle and simulate its position in
global map. This requires no Infrastructure support. But it is
highly accurate.
• Wi-Fi networks: Wi-Fi networks can be used in closed
environment like University, where the environment is
controlled by access points at regular places

33. Routing Methodologies
• In V2V communication, the collision warning messages are
broadcast from vehicle to vehicle across multiple hops
without the involvement of a roadside unit.
• In case of V2R the warning messages are first sent to a
roadside unit, and then broadcast by the roadside unit to all
vehicles in range.
• In V2R/V2V Hybrid Model, Vehicles which receive a warning
message via V2V communication will send it to a roadside unit
if they did not receive a warning message with the same event
ID from roadside units.

34. Evaluation metrics in VANET at
application and Network layer
• Delay Time:- Compared to ideal time vehicle would take in
absence of signals and other vehicles
• Estimation Error:- Accuracy of information availaible in the
range specified
• Transmission delay:- Average delay of a packet when the
packet is generated, until the time it gets successfully received
by all neighbors
• Packet Delivery Ratio:- Ratio of the number of messages
received by the destination to the number sent by the sender.

35. Evaluation metrics in VANET at
application and Network layer
• Jitter:- Jitter is the variation in the end-to-end delay between
packets arriving at the destination
• Connection duration:- To monitor a meaningful interaction
between different parties
• Load on the Network:- Number of packets sent, received and
dropped
• Awareness Percentage:- Fraction of nodes passing the location
that had information about the location before entering it

36. VANET Simulators
• Deploying and testing VANETs involves high cost and intensive
labor.
• Simulations of VANET often involve large and heterogeneous
scenarios. Compared to MANETs, when we simulate VANETs,
we must account for some specific characteristics found in a
vehicular environment.

37. VANET Simulators
• Vehicular mobility generators are needed to
increase the level of realism in VANET
simulations.
• Network simulators perform detailed packet-
level simulation of source, destinations, data
traffic transmission, reception, background
load, route, links, and channels.
• VANET simulators provide both traffic flow
simulation and network simulation

39. VANET Traces
• Currently, minimum amount of traces exist for VANET testing.
• One such trace is obtained from a multi-agent microscopic
traffic simulator (MMTS) that was developed by K. Nagel (at
ETH Zurich, now at the Technical University in Berlin,
Germany).
• Around 260'000 vehicles are involved in the simulation with
more than 25'000'000 recorded vehicles direction/speed
changes in an area of around 250 km x 260 km.
• For the evaluation of inter-vehicle routing schemes, they use a
24 hour detailed car traffic trace file generated by MMTS.

40. Thank You!!
Questions ???