Advanced carrier sensing to resolve local channel congestion

Robert K. Schmidt, Achim Brakemeier, Tim Leinmüller, Frank Kargl, Günther Schäfer

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    16 Citations (Scopus)


    Communication performance in VANETs under high channel load is significantly degraded due to packet collisions and messages drops, also referred to as local channel congestion. So far, research was focused on the control of transmit power and the limitation of the messages rate to mitigate the effects of high load. Few attention has been paid to the carrier sensing setup, i.e controlling WHEN the channel is indicated as clear. In previous work, we identified that the Clear Channel Assessment (CCA) as part of the carrier sensing is a very efficient way of controlling the spatial reuse under high load. The CCA threshold determines at which received power level the channel is sensed busy. In this paper, we propose a stepwise CCA Threshold Adjustment (CTA) depending on how long the packet has been waiting already for medium access. This basic and robust approach mitigates significantly the problem of local message queue drops and hence local congestion. The simulation study confirms the reduction of the average and maximum medium access delay as well as the prevention of message queue drops. Even under inaccurate CCA thresholds among the vehicles, fairness in medium access can be maintained by using CTA. In all cases, the awareness of each vehicle is dramatically improved within the safety-critical area of each vehicle.
    Original languageUndefined
    Title of host publicationProceedings of the Eighth ACM international workshop on Vehicular inter-networking, VANET 2011
    Place of PublicationNew York
    PublisherAssociation for Computing Machinery (ACM)
    Number of pages10
    ISBN (Print)978-1-4503-0869-4
    Publication statusPublished - Sep 2011
    EventEighth ACM international workshop on Vehicular inter-networking, VANET 2011 - Las Vegas, NV, USA
    Duration: 23 Sep 201123 Sep 2011

    Publication series



    WorkshopEighth ACM international workshop on Vehicular inter-networking, VANET 2011
    Other23 September 2011


    • METIS-285047
    • Congestion control
    • IR-79509
    • VANET
    • clear channel assessment
    • EWI-21358
    • EC Grant Agreement nr.: FP7/269994
    • spatial reuse
    • vehicular ad hoc networks
    • SCS-Cybersecurity
    • carrier sensing

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