Optimization and Analysis of C-V2X Resource Scheduling Protocol Based on Resource Reservation Penalty and Active Avoidance

In Cellular Vehicle-to-Everything (C-V2X) Mode 4, the Semi-Persistent Scheduling (SPS) protocol based on sensing introduces a reservation mechanism that significantly reduces the cost of repeated reservations for vehicles, drawing widespread attention. However, under the reservation mechanism, non-periodic traffic can lead to severe time-frequency resource wastage, and channel collisions that occur prior to reservation can persist throughout the reservation period. To address these issues, this paper proposes a protocol that introduces a waste counter to record resource wastage and actively avoid collisions by sensing channel conflicts during the wastage cycles. By establishing a discrete-time Markov chain (DTMC) model to analyze both protocols, simulation results show that, compared to the original mechanism, the proposed mechanism reduces channel collisions, average wastage occurrences, and average wastage probability.