A Discrete Time Markov Chain Based Comparison of the MAC Layer Performance of C-V2X Mode 4 and IEEE 802.11p
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Vehicle to vehicle (V2V) communication plays a pivotal role in intelligent transport systems (ITS), with cellular-vehicle to everything (C-V2X) and IEEE 802.11p being the two competing enabling technologies. This paper presents multi-dimensional discrete time Markov chain (DTMC) based models to study the medium access control (MAC) layer performance of the ETSI ITS-G5 version of IEEE 802.11p and C-V2X Mode 4. The models are coupled with an appropriate DTMC based queue model, that consists of traffic generators for periodic cooperative awareness messages (CAMs) and event driven decentralized environmental notification messages (DENMs). Closed-form solutions for the steady state probabilities of the models are obtained, which are then utilized to derive expressions for key performance indicators of the two communicating technologies. An application for a highway scenario is presented to provide numerical results, and to draw insights on the performance. In particular, a performance comparison between IEEE 802.11p and C-V2X Mode 4 in terms of the average delay, the collision probability, and the channel utilization is presented. The results show that IEEE 802.11p is superior in terms of average delay, where as C-V2X Mode 4 excels in collision resolution. The paper also includes design insights on possible future MAC layer performance enhancements of both standards.
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