Modeling the medium access control layer performance of cellular vehicle-to-everything mode 4 and IEEE 802.11p

Abstract

The capability of vehicle-to-everything (V2X) communication to wirelessly exchange information on speed and location of vehicles over an ad hoc network envisions promise substantially reducing vehicle collisions, congestion, fuel usage and pollution. V2X communication plays a pivotal role in intelligent transport systems (ITS), with IEEE 802.11p and cellular V2X (C-V2X) being the two competing enabling technologies. This thesis focuses on discrete-time Markov chain (DTMC) based modeling of the medium access control (MAC)-layer performance of the two enabling technologies for evalua- tion, comparison and enhancement. Firstly, DTMC-based models for the MAC layer operations of IEEE 802.11p and C-V2X Mode 4 are developed, considering periodic and event-driven messages. The results show that IEEE 802.11p is superior in average delay, whereas C-V2X Mode 4 excels in collision resolution, which leads to its higher throughput. Then, the models are extended to support the parallel operation of four multi-priority data streams, which are crucial for quality of service (QoS). Results show that IEEE 802.11p is superior in maintaining fairness among multi-priority data streams. It is also shown that the higher delay values in C-V2X lead to unfavorable packet delays in the low priority streams. The thesis studies the allocation of multiple candidate single-subframe resources (CSRs) per vehicle as a solution. It proposes a methodology to determine the number of CSRs for each vehicle based on the number of total vehicles, and to assign the multiple data streams for simultaneous transmission. The numerical results highlight the achievable delay gains of the proposed approach and its negligible impact on packet collisions.