6. Deterministic MAC Protocol Based on Clustering for VANETs

This chapter proposes a direction aware cluster-based multichannel MAC (DA-CMAC) protocol for Vehicular Ad-Hoc Networks (VANETs) in which vehicles travelling in the opposite direction may result in a short communication period. Clustering based on the direction of travel can reduce the cost of reconfiguration due to the short communication period. Each cluster consists of Cluster Head (CH), Cluster Members (CMs) and Gateway Vehicles (GV). CH calculates priorities of CMs based on the value of eligibility function that is received from the CM and assign each CM a unique priority based on the future position of CM, CM ID, and eligibility function. The eligibility function is calculated using the number of connected neighbors, average speed deviation, and the average distance between neighbors and itself. Clusters are independently managed and locally reconfigured as vehicles travel. Moreover, the proposed DA-CMAC protocol manages the channel access and allocates time slots to its CMs, reducing access and merging collisions in the channel, by grouping the time slots into two sets based on the direction of movement. Each CMs are allocated with one time slot in both control service channel to achieve fairness in channel access. Simulation results of DA-CMAC are compared with HCA protocol. Simulation results show that the DA-CMAC protocol have higher reliability of packets, fewer CH changes and fewer number of access collisions compared with HCA protocol.