Reliable broadcasting in VANETs using Physical-Layer Network Coding

In this paper, we present a PNC-based MAC protocol for VANETs (VPNC-MAC) which makes use of the PNC to ensure efficiency and reliability of periodic beacon transmissions in VANETs. The VPNC-MAC protocol basically consists on two phases: a setup phase and the heartbeat packet exchange phase. During the setup stage, VPNC-MAC uses a location-based OFDMA signaling technique to guarantee a quick and non bandwidth consuming setup. In addition, the packet exchange phase in VPNC-MAC contains two periods of variable and adjustable length. The fist period is a guaranteed time slot period, called the VPNC-MAC session, in which the nodes exchange their packets using PNC. The second period is a contention period reserved to nodes unable to transmit during the VPNC-MAC session. The simulation results shows that the VPNC-MAC protocol outperforms the optimal CSMA (ideal TDMA) in terms of capacity of transmissions supported within a fixed duration, and overall packet reception rate.