An RSU Controlled IEEE 802.11ac Based MAC Protocol for Multi-Vehicle Uplink Transmission in VANET

In this paper, we have explored the possibility of using IEEE 802.11ac as the MAC layer solution for VANET to meet the new requirements for various types of broadband services for Vehicle to Infrastructure (V2I) wireless communication. We have proposed an efficient RSU controlled MAC protocol that enables uplink MU-MIMO transmission for different priority traffic categories. Performance metrics show that the throughput enhancement of proposed MAC in MU-MIMO uplink transmission is three times the throughput of a single user transmission. We observe that due to smaller contention window size, the mean backoff time for the highest priority messages remain in the range of millisecond even at high packet arrival rate and node density. The saturation throughput analysis clearly shows two desired operating points: highest network throughput and highest network capacity. We achieve a maximum payload throughput of 64\% at an aggregate packet arrival rate of 1100 packets/sec whereas 54\% network throughput is achieved at a maximum load of 1200 packets/sec. We observe that the stable operating load remains between 1100-1200 packets/sec in our model.