A Token-Based MAC Protocol for Achieving High Reliability ... A Token-Based MAC Protocol for...

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  • A Token-Based MAC Protocol for Achieving High Reliability in VANET Ali Balador (Ph.D.) Postdoctoral Research Fellow SICS Swedish ICT Västerås AB [email protected] -- +46 730532133

    Goals

    Background

    Protocol Description

    Simulation Settings

    Highway Scenario Urban Scenario

    Conclusions

    Future Works

    Acknowledgements

    §  CAM (Cooperative Awareness Messages) or beacon [1] o  Short, periodic status messages (2-10 times per

    second) o  Broadcasted by every car o  No multi-hop intended (so far) o  Include: position, speed, direction, other status

    information (e.g. blinker status)

    §  DENM (Decentralized Environmental Notification Message) [2] o  Event-based warning message o  Broadcasted only during specific event o  Broadcast stops when event is over

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    DTB−MAC IEEE802.11P

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    §  Beacon Send Rate: 10 packet/s §  Beacon size: 500 Bytes §  Data Rate: 6 Mbps §  Transmission Range: 500 m §  Simulation time: 300 s §  Simulation package: Veins

    Simulation Scenarios §  Highway Scenario o  2.2 km highway with 2 lanes

    §  Urban Scenario o  Downtown of Milan o  2.6*2.6 km2

    References

    §  In low densities o  difficulties for token circulation o  low BDR

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    §  Metrics o  Channel utilization o  Beacon Delivery Ratio (BDR)

    Propose an alternative solution specially for high densities when IEEE 802.11p is not able to handle a high number of beacons.

    The way DTB-MAC uses the token passing not only does not produce more delay, but also improve it for some network densities.

    §  To extend DTB-MAC protocol by adding support for event-driven messages for safety applications in highway and urban scenarios

    §  To extend our token-based protocols to handle Platooning Application challenges o  Selecting a token manager when two tokens

    are detected o  Merging two platoons of cars driving in close

    proximity

    This work was partially supported by SICS Swedish ICT Västerås AB through the EU-project, SAFECOP. Moreover, Balador is funded by ERCIM Alain Bensoussan postdoctoral Fellowship.

    §  Address the short-comings of IEEE 802.11p §  Support the strict requirements on timing and

    reliability §  Using standardized 802.11-based hardwares

    Ring establishment and maintenance

    Data age list generation o  Each vehicle maintains a data age list

    logging the age of the latest successfully received beacon from individual nodes.

    o  Next token holder is the node with the highest data age on the current token holder’s list.

    Token Passing o  Token is circulated with beacon packets o  Whoever holds the token has unique right

    to access the channel o  Each token holder is responsible for the

    choice of the next token holder Transmission order

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    Data age list

    [1] “Its; vehicular communications; basic set of applications; part 2: Specification of cooperative awareness basic service,” ETSI Std. EN 637-2, Tech. Rep., November 2014. [2] “Its; vehicular communications; basic set of applications; part 2: Specification of decentralized environmental notification basic service,” ETSI Std. EN 637-3, Tech. Rep., November 2014.

    §  Support for delay-sensitive data traffic through deterministic channel access is needed o  In the current standard this support is

    compromised due to the properties of IEEE 802.11p MAC

    §  A distributed, token-based MAC method supports reliable beacon broadcast before a given deadline o  Prioritizing vehicle that is in most need to

    communicate to keep its deadline. o  Built-in retransmission opportunities (if

    bandwidth available)

    BMW Summer School 2016 Bavaria, Germany, July 18-23