  Vehicular communication requires vehicles to self-organize through the
exchange of periodic beacons. Recent analysis on beaconing indicates that the
standards for beaconing restrict the desired performance of vehicular
applications. This situation can be attributed to the quality of the available
transmission medium, persistent change in the traffic situation and the
inability of standards to cope with application requirements. To this end, this
paper is motivated by the classifications and capability evaluations of
existing adaptive beaconing approaches. To begin with, we explore the anatomy
and the performance requirements of beaconing. Then, the beaconing design is
analyzed to introduce a design-based beaconing taxonomy. A survey of the
state-of-the-art is conducted with an emphasis on the salient features of the
beaconing approaches. We also evaluate the capabilities of beaconing approaches
using several key parameters. A comparison among beaconing approaches is
presented, which is based on the architectural and implementation
characteristics. The paper concludes by discussing open challenges in the
field.
