  This paper presents OpenCV2X, the first publicly available, open-source
simulation model of the Third Generation Partnership Project (3GPP) Release 14
Cellular Vehicle to Everything (C-V2X) sidelink, which forms the basis for 5G
NR Mode 2 under later releases. This model is fully compliant with the existing
vehicular service and application layers, including messaging sets as defined
by the automotive and standards communities providing a fully standardised,
cross-layer communication model. Using this model, we show how the current
sidelink scheduling mechanism performs poorly when scheduling applications with
highly aperiodic communication characteristics, such as ETSI Cooperative
Awareness Messages (CAMs). We then provide the first indepth evaluation of
dedicated per-packet aperiodic scheduling mechanisms, in contrast to schemes
that parameterise the existing algorithm. This paper highlights that the level
of aperiodicity exhibited by the application model greatly impacts scheduling
performance. Finally, we analyse how such scheduling mechanisms might co-exist.
