Collision Avoidance in Vehicular Networks

Avanti ChimoteCharan Hebri

Kuppuraj GunasekaranSandeep N L

Saravanan Sathananda Manidas

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.

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,.

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)

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

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.

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.

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.

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.

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.

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.

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.

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.

InVANET(Intelligent Vehicular AdhocNetwork)

• Incorporating intelligence into a VANET toimprove safety

• Makes use of V2V and V2R communication• Make intelligent inferences about traffic incidents• Facilitate easy and effective communication

between vehicles with dynamic mobility

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

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.

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

Communication MethodologiesGPS 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

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

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

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.

Communication MethodologiesDisadvantages 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

GPSense Car Platforms

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

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 Vehicle2) Vehicle to Roadside

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

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

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

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.

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

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.

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.

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

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.

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

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.

Thank You!!

Questions ???