Minimizing emergency message collisions and maximizing network throughput in IEEE 802.11p vehicular wireless network

IEEE 802.11p is proposed as the VANET wireless MAC interface for the transmissions of emergency messages in V2V and V2I Communications. However, in a high mobility VANET, QoS of both the emergency message (EM) and handoff transmissions suffer from high collision probability of the contention-based media access mechanism and high interference exhibiting near the cell-edge that encodes a low coding rate of the Adaptive Modulation and Coding (AMC) scheme. Thus, this paper proposes an efficient MAC for IEEE 802.11p to solve above critical issues, in which the approach consists of three main mechanisms: 1) the Sigmoid-based CW Decrease (SWD) algorithm, 2) the Dynamic Initial CW (DIW) algorithm, and 3) Relay-based partition Collision Domain for Handoffs (RCDH). Note that the CW decrease formulation is determined based on the Sigmoid function. Numerical results demonstrate that the analysis results are close to the simulation results, and thus justify the correctness of the mathematical analytical model. In addition, the proposed approach outperforms the compared approaches (including the IEEE 802.11p std.) in EM transmission delay, collision probability, throughput, and MAC frame dropping probability.