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VEHICLE AD HOC NETWORKS: APPLICATIONS AND RELATED TECHNICAL ISSUES. A summary. Applications. Classification in two types: Safety applications Goal: decrease the number of accidents User applications Examples: Internet, P2P. Table on Content. Physical / Mac layer Routing

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Presentation Transcript
applications
Applications

Classification in two types:

Safety applications Goal: decrease the number of accidents

User applications Examples: Internet, P2P

table on content
Table on Content

Physical / Mac layer

Routing

Data dissemination

TCP/IP

Security

Simulations

Related projects

Conclusions

phy mac layer
Phy/Mac layer

Three main problems in VANETs (on these layers)

Robust transmission and efficient sharing of the radio medium

Large variation in node density

Ensuring QoS

physical layer
Physical layer

IEEE 802.11a/b/g

IEEE 802.11p

300m – 1km

Like 802.11a but doubled physical parameters

UTRA-TDD

mac layer medium sharing
MAC layermedium sharing

Two types:

Controlled access (e.g. TDMA)

Random access (e.g. Aloha) Preferred for VANETs

Recent proposal:

DSRC, a short-medium technology using IEEE 802.11 access technology @ 5.9 GHz.

DSRC is standardized as IEEE 802.11p as part of WAVE.

mac layer node density
MAC layerNode density

Topic is studied before in wired context but VANETs add more complexity due to spatial reuse.

Proposed solutions:

Dividing the road in small segments

Using power control

Using directional antennas Low gain in VANETs due to linear networks

mac layer qos
MAC layerQoS

Quality of Service is important, for instance, for safety applications.

Safety messages need to be send immediately and efficiently.

Two solutions:

Intelligently change the number and rate at which vehicles send messages

Change the transmission range

routing
Routing

VANET specific properties and issues:

VANETs are usually linear networks

Mobility is high but movements are predictable

Connectivity is a challenge due to the high mobility

Mobility may improve network performance

VANETs require broadcast protocols to disseminate information is a certain area

routing route connectivity
RoutingRoute connectivity

MANET unicast protocols (AODV, DSR, OLSR)

Reactive

Proactive

Geocast routing for VANETs

Forward based on geographical destination packet

Reduced routing state at each node

Requires location service

Pro-active handoff

Enhanced routing

Predict radio link breakage

Message ferrying

Increase connectivity

routing internet connectivity
RoutingInternet connectivity

WLAN-based

Drive-thru architecture

Heavy initial investments

Multi-home vehicle based

Vehicles act as mobile gateways

Share bandwidth and processing power

What is the incentive?

Combination of both!

routing safety application
RoutingSafety application

Broadcast protocols are required

Reactive protocols have unacceptable delays

Proactive protocols consume a considerable part of the bandwidth

Traditional multicast are inefficient for broadcasting.

Three described techniques:

Pure flooding (high bandwidth, high success, low delay)

Multipoint relay (MPR) diffusion technique of OLSR (lowest bandwidth, too high delay)

Geographic aware flooding

data dissemination safety applications
Data disseminationSafety applications

Data dissemination is the transport of data to theintended recipients while satisfying certain requirements such as delays, reliability, etc.

Safety applications require the limitation of dissemination:

Hop count

Vehicle location information

data dissemination user applications
Data disseminationUser applications

The problem of high mobility makes locating data very difficult in VANETs

Network partition can render data unavailable for some time

Two solutions:

Using multi-home vehicles (requires infrastructure)

Adaptive, content-driven routing and data dissemination algorithm for intelligently routing search queries in a peer-to-peer network

tcp ip stack
TCP/IP stack

TCP/IP is not well suited for VANETs

Unfairness in wireless networks cause unfairness in transport layer

Transmission errors are interpreted as congestion

Connection loss is interpreted as congestion

Many TCP extension were proposed (TCP-F,TCP-ELFN,etc.)end-to-end extensions to determine the cause of packet loss

Some completely new transport protocols were designed (ACTP, ATP)

security
Security

Security is extremely important in VANETs

Ensuring anonymity and privacy in a VANET while maintaining access control and liability is difficult

A requirement of cryptographic techniques used in VANETs must have low traffic and processing overheads

IEEE 802.11p proposes using asymmetric cryptography to sign safety messages

Pseudonyms to make communication anonymous

Requires changing pseudonyms periodically

Certification revocation might be handled

Certificate Revocation List (CRL)

Neighborhood detection of misbehaving vehicles

simulations
Simulations

The random waypoint model (RWM) may be suitable for VANETs

Two simulation approaches:

Feeding a network simulator with traces that are generated from traffic simulators

Integrated traffic and network simulator

related projects
Related projects

European projects:

CarTALK 2000

FleetNet

National projects:

Network on Wheels

PATH

Organizations:

IEEE

C2C-CC

conclusions
Conclusions

The subject of VANETs is still immature

Many studies try to solve one solution in VANET

Hardly ever, a general architecture is proposed (though probably a key success factor for VANETs)

A cross layer solution might be more likely for solving issues of VANETs instead of the OSI model