In this paper we demonstrate the importance of transmit power control for avoiding saturated channel conditions and ensuring best use of the channel for safety-related purposes. We propose a distributed transmit power control method based on a strict fairness criterion, D-FPAV, to control the load of periodic messages on the channel. The benefits are twofold: i) bandwidth is made available for higher priority data like dissemination of warnings; ii) beacons from different vehicles are treated with `equal rights' and best possible reception under the available bandwidth constraints is ensured. We formally prove the fairness of the proposed approach. Then we make use of the ns-2 simulator significantly enhanced by realistic highway mobility patterns, improved radio propagation and receiver models, and the IEEE 802.11p specifications, to show the beneficial impact of D-FPAV for safety-related communications. We finally put forward a method, EMDV, for fast and effective multi-hop information dissemination of event-driven messages and show that EMDV benefits of the beaconing load control provided by D-FPAV with respect to both probability of reception and latency.
|Autor:||M. Torrent Moreno, J. Mittag, P. Santi, H. Hartenstein||Links:||Download PDF|
|Quelle:||IEEE Transactions on Vehicular Technology, Volume 58, Issue 7, S. 3684-3707, September 2009|
Direct radio-based vehicle-to-vehicle communication can help to prevent accidents by providing accurate and up-to-date local status and hazard information to the driver. In this paper, we assume that two types of messages are used for traffic safety-related communication: periodic messages (`beacons') sent by all vehicles to inform their neighbors about their current status (i.e., position), and event-driven messages sent whenever a hazard has been detected. In IEEE 802.11 DCF-based vehicular networks, interferences and packet collisions can lead to failure of reception of safety-critical information, particularly when the beaconing load leads to an almost saturated channel as it could easily happen in many critical vehicular traffic conditions.