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VEHICLE AD HOC NETWORKS: APPLICATIONS AND RELATED TECHNICAL ISSUES

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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VEHICLE AD HOC NETWORKS: APPLICATIONS AND RELATED TECHNICAL ISSUES

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  1. VEHICLE AD HOC NETWORKS: APPLICATIONSAND RELATED TECHNICAL ISSUES A summary

  2. Applications Classification in two types: Safety applications Goal: decrease the number of accidents User applications Examples: Internet, P2P

  3. Table on Content Physical / Mac layer Routing Data dissemination TCP/IP Security Simulations Related projects Conclusions

  4. 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

  5. Physical layer IEEE 802.11a/b/g IEEE 802.11p 300m – 1km Like 802.11a but doubled physical parameters UTRA-TDD

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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!

  12. 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

  13. 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

  14. 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

  15. 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)

  16. 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

  17. 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

  18. Related projects European projects: CarTALK 2000 FleetNet National projects: Network on Wheels PATH Organizations: IEEE C2C-CC

  19. 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

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