Performance Evaluation of Hybrid Distributed-Centralized TDMA in High-Density Vehicular Networks

This letter considers the hybrid of distributed and centralized time division multiple access (TDMA) mechanism in high-density vehicular networks, where vehicles within a certain road section perform distributed access based on the slot map broadcast by a centralized unit, i.e., road side unit (RSU). By both theoretical analysis and simulation, we mainly explore how the medium access control (MAC) performance is affected by the continuous vehicle entering and leaving the road section. First, we express the
$n$
-step transition probability of the number of vehicles that have successfully acquired a time slot, based on which the average success ratio of vehicles within
$N$
frames is calculated. Then we present the method to derive the success probability of a certain vehicle within
$N$
frames and its average access delay. Furtherly, simulations verify the correctness of our theoretical analysis, and it is shown that fast access can be ensured if the vehicles are unblocked on the road.