Priority Scheduling And Congestion Control Of Safety Messages For VANETs

Significant research efforts in industry and academia have been underway toaccelerate the development of intelligent transportation systems (ITS) for safe, efficient,and convenient driving. Much of the research effort has been devoted to meet thechallenges of effectively integrating wireless communications, computing and advancedsensor technologies into vehicular ad-hoc networks (VANET).One of the major driving factors for the investigation and deployment of VANET issafety, since a driver assistance system can quickly detect potentially dangeroussituations, and notify the driver about the approaching peril by collecting the statusinformation of the surrounding environment. So an optimal scheduling is very importantto guarantee the dissemination of an emergency message timely and reliably. In thispaper our focuses are priority scheduling and congestion control.Firstly, a dynamic priority based scheduling scheme is conceived for the safetymessages of vehicular ad-hoc networks. A spatio-temporal correlation basedmessage-priority function is developed, which monotonically decreases with thetransmission range and/or the transmission duration of a message’s disseminationincrease. Additionally, the dissemination of a message is limited to a certain life-timeand spatial area, which can adapt the dynamic network topology.Afterwards, a basic channel resource allocation algorithm for periodic safetymessage (PSM) and event-driven safety message (EDSM) is proposed, which canguarantee enough channel resources for EDSM. And on that basis, an adaptive beaconrate and power control adjusting mechanism for congestion control is proposed, whichcan avoid the network congestion and increase the channel utilization on condition thatthe accuracy and safety is guaranteed.