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.