  Cellular vehicle-to-everything (C-V2X) enables safety-critical connected
vehicular service by exchanging basic safety messages (BSMs) among nearby
vehicular users (VUEs). Timely transmission of BSMs is crucial to avoid stale
information at VUEs. However, successive packet losses can lead to large
inter-packet gaps (IPGs), reducing the BSMs' reliability. This paper
investigates the tail behavior of IPG and information age (IA) distributions in
C-V2X mode 4, a decentralized resource allocation method based on
semi-persistent scheduling (SPS). We study the improvements and trade-offs
introduced by SAE one-shot transmission to decrease the number of successive
BSM losses at destination VUEs. The study employs high-fidelity system-level
simulations that closely follow the SPS process of CV2X mode 4 to evaluate the
performance of interleaved one-shot SPS transmissions. The numerical results
demonstrate significant improvement in the IPG and IA tail distributions in
various simulation scenarios. Additionally, we propose an accurate analytical
model to characterize the IPG tail behavior of C-V2X BSM transmissions. The
proposed model is validated by comparing its results with those obtained using
the system-level simulations. Our validation shows that the proposed model
generates analytical results that coincide with the asymptotic slopes of IPG
distribution in different BSM transmission modes.
