On the trade-off between AoI performance and resource reuse efficiency in 5G NR V2X sidelink

In 5G New Radio (NR)-Vehicle-to-Everything (V2X) Mode 2 sidelink, vehicles autonomously select resources for periodic broadcasts using either Dynamic Scheduling (DS) or SemiPersistent Scheduling (SPS). SPS typically reduces collisions by selecting radio resources based on channel sensing and persisting on the same radio resource, which is shown to improve efficiency of spatial reuse. However, our study shows that this does not always improve the Age of Information (AoI). Persistence induces bursts of message losses, creating extended gaps between successful updates. Consequently, DS – despite potentially achieving lower Packet Delivery Ratio (PDR) – often achieves better AoI for realistic performance targets. These findings reveal a fundamental trade-off between reliability (PDR) and timeliness (AoI) and highlight the need for careful persistence management in vehicular communication systems.