Reliable congestion control mechanism for safety applications in urban VANETs

In vehicular ad hoc networks (VANETs), cooperation between vehicles is needed for proper performance of safety applications. Beacons are periodically broadcasted by vehicles to inform their neighbors of their information, such that periodic beacons are one of the building blocks that enable the operation of safety applications. Safety applications have their own strict quality of service (QoS) requirements, and they require reliable and timely data communication within networks. When many vehicles are trying to broadcast within a confined area at the same time, frequent channel contention and congestion may occur. Therefore, channel congestion control mechanisms are key for reliable and efficient operation of safety applications. In this paper, an adaptive beacon generation rate (ABGR) congestion control mechanism is proposed to reduce channel congestion and contention. ABGR can dynamically adjust the beacon generation rate according to varying levels of vehicles' density to ensure reliable and timely delivery of beacons. Inspired by the correlation between traffic density and vehicle speed, a dynamic application-level reliability assessment scheme (T-Pro) is proposed to evaluate the reliability of various safety applications at varying density. Finally, the application-level reliability of three safety applications is evaluated using the ABGR mechanism. Numerical results show that the performance of ABGR is far higher than that of the current DSRC. The application-level reliability of three safety applications exceeds 99%, even if density reaches 450 vehicles/(km*3 lanes). (C) 2019 Elsevier B.V. All rights reserved.