Interference-Aware Geocasting for VANET

With the introduction of standards such as DSRC
and WAVE, vehicular ad hoc networks (VANET) are being considered
as candidates to improve road safety. Safety applications
developed on top of VANET enable vehicle and driver improved
awareness of the road situation through vehicles sharing their
status and knowledge of the road conditions. In order for these
systems to operate, they depend on reliable communication. To
overcome fading, shadowing and other effects that cause packet
loss, such applications commonly use retransmission schemes to
improve packet delivery. However, the wireless channels used for
these applications are bandwidth constrained, and retransmission
can cause interference which in turn will degrade the reliability
of the communication channel. Therefore, it is necessary to find
a strategy that balances retransmission with channel occupancy
for optimal reliability.
In this paper, we present a cooperative retransmission algorithm
that overcomes shadowing caused by blocking objects such
as heavy vehicles in order to combat the resulting unreliability,
whilst controlling the interference caused by retransmissions.
The proposed algorithm weighs up the additional area a node
can cover, with the amount of interference a retransmission by
the same node would cause. We evaluate the performance of
the algorithm in urban scenarios using the NS-3 simulator, and
find that the proposed algorithm is effective in overcoming the
negative effects of shadows caused by blocking objects.