  Cooperative vehicle safety (CVS) systems operate based on broadcast of
vehicle position and safety information to neighboring cars. The communication
medium of CVS is a vehicular ad-hoc network. One of the main challenges in
large scale deployment of CVS systems is the issue of scalability. To address
the scalability problem, several congestion control methods have been proposed
and are currently under field study. These algorithms adapt transmission rate
and power based on network measures such as channel busy ratio. We examine two
such algorithms and study their dynamic behavior in time and space to evaluate
stability (in time) and fairness (in space) properties of these algorithms. We
present stability conditions and evaluate stability and fairness of the
algorithms through simulation experiments. Results show that there is a
trade-off between fast convergence, temporal stability and spatial fairness.
The proper ranges of parameters for achieving stability are presented for the
discussed algorithms. Stability is verified for all typical road density cases.
Fairness is shown to be naturally achieved for some algorithms, while under the
same conditions other algorithms may suffer from unfairness issues. A method
for resolving unfairness is introduced and evaluated through simulations.
