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Advisor(s)
Abstract(s)
Vehicular ad-hoc networks (VANET) enable vehicles to exchange information on traffic
conditions, dynamic status and localization, to enhance road safety and transportation efficiency.
A typical VANET application is platooning, which can take advantage of exchanging information on
speed, heading and position to allow shorter inter-vehicle distances without compromising safety.
However, the platooning performance depends drastically on the quality of the communication
channel, which in turn is highly influenced by the medium access control protocol (MAC). Currently,
VANETs use the IEEE 802.11p MAC, which follows a carrier sense multiple access with collision
avoidance (CSMA/CA) policy that is prone to collisions and degrades significantly with network
load. This has led to recent proposals for a time-division multiple access (TDMA)-based MAC that
synchronize vehicles’ beacons to prevent or reduce collisions. In this paper, we take CSMA/CA
and two TDMA-based overlay protocols, i.e., deployed over CSMA/CA, namely PLEXE-slotted and
RA-TDMAp, and carry out extensive simulations with varying platoon sizes, number of occupied
lanes and transmit power to deduce empirical models that provide estimates of average number of
collisions per second and average busy time ratio. In particular, we show that these estimates can
be obtained from observing the number of radio-frequency (RF) neighbours, i.e., number of distinct
sources of the packets received by each vehicle per time unit. These estimates can enhance the online
adaptation of distributed applications, particularly platooning control, to varying conditions of the
communication channel.
Description
Keywords
VANETs IEEE 802.11p MAC Overlay TDMA Empirical models