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During vehicle driving, many problems will occur in the communication process of VANET, including but not limited to node conflict management, time delay, time slot division management, etc. The Media Access Control (MAC) protocol is specifically responsible for solving these problems. The existing MAC protocol with fixed time slot allocation cannot solve the problems of excessive node conflicts and low packet reception rate when current traffic is high. When designing MAC protocol for VANET, we must consider the speed and dynamic distribution of nodes, which is also the key to optimize the protocol. In this paper, we propose a new TDMA protocol, called SMDP-MAC (Adaptive Slot Management MAC Protocol Based on Dynamic Parameters). This protocol is a new protocol that divides time slots according to vehicle dynamic parameters to solve conflict problems. SMDP-MAC manages the time slot in the vehicle channel access and maintenance phase according to the vehicle's GPS information, driving direction, speed and acceleration to reduce the collision probability. In the SMDP-MAC protocol, the frame is divided into multiple timeslots based on TDMA, the timeslots in the frame are divided into two timeslot sets according to the direction of travel, and then the channel access timeslot is divided and selected according to the dynamic parameters of each vehicle (including GPS information, vehicle speed and vehicle acceleration information). After the network enters a stable state, the time slot occupation of the vehicle will also be dynamically adjusted according to the vehicle position.This paper presents the analysis and simulation results under the highway scenario and verifies the effectiveness of SMDP-MAC protocol by comparing with VeMAC, BMA and ASMAC protocols.
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