Performance Analysis of IEEE 802.11p Protocol in IoV under Error-Prone Channel Conditions

Abstract

The complexity of the channel condition in the Internet of vehicles (IoV) may increase the bit error rate (BER) of the intelligent vehicle terminals, resulting in data transmission failures or errors. Therefore, it is necessary to improve the performance of communication protocols under error-prone channel conditions. This article investigates the influence of the access categories’ (ACs) performance with channel errors by using four $\mathrm{A}\mathrm{C}\mathrm{s}$ to cause service differentiation based on the enhanced distributed channel access (EDCA) mechanism of the IEEE 802.11p. To address the error-prone characteristics of the channel and unsaturated traffic conditions, a three-dimensional Markov model is developed first, followed by an analysis of the characteristics and mutual transition probabilities of the seven classes of states in the model, and then, the steady-state equations of the system are developed to derive the steady-state distribution to study system performance. The model considers the backoff phase, the freezing of the backoff counter, the retransmission limit, the probability of collisions occurring, the size of the maximum and minimum contention window, and the number of interframe intervals. These parameters are chosen to meet the requirements for the protocol to operate, while also preventing overestimation of throughput and avoiding having packets being served all the time. We derive expressions for the throughput and delay of $\mathrm{A}\mathrm{C}\mathrm{s}$ under the conditions of error channels and unsaturated traffic. The impact of channel errors on the throughput and delay of $\mathrm{A}\mathrm{C}\mathrm{s}$ is evaluated by numerical simulation. Numerical results show that too many stations in the system will increase the average access delay and decrease throughput. The increase in BER will seriously decrease the performance of high-priority $\mathrm{A}\mathrm{C}\mathrm{s}$ . The throughput of the $\mathrm{A}\mathrm{C}\mathrm{s}$ is also modeled to vary with frame length and BER, and the variation curves of the optimal frame lengths for $\mathrm{A}\mathrm{C}3$ and $\mathrm{A}\mathrm{C}2$ were obtained.