In this paper the DSRC/IEEE 802.11p Medium Access Control (MAC) method of the vehicular communication has been simulated on highway road scenario with periodic broadcast of packets in a vehicle-to-vehicle situation. IEEE 802.11p MAC method is basically based on carrier sense multiple accesses (CSMA) where nodes listen to the wireless channel before sending the packets. If the channel is busy, the vehicle node must defer its access and during high utilization periods this could lead to unbounded delays. This well-known property of CSMA is undesirable for critical communications scenarios. The simulation results reveal that a specific vehicle is forced to drop over 80% of its packets/messages because no channel access was possible before the next message/packet was generated. To overcome this problem, we propose to use self-organizing time division multiple access (STDMA) for real-time data traffic between vehicles. Our initial results indicate that STDMA outperforms CSMA for time-critical traffic safety applications in ad- hoc vehicular networks.
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