The Impact of Blind Retransmissions on the Age of Information in NR-V2X

In this paper, we focus on Semi-persistent Scheduling (SPS) in the context of New Radio for Vehicle-to-Everything (NR-V2X) communications. SPS is a reservation-based channel access protocol without feedback, in which nodes broadcast time-sensitive information (e.g., status updates) to their neighbors in a wireless network setting. In such scenarios, semantic-aware metrics such as the Age of Information (AoI) often capture fundamental performance trade-offs better than traditional metrics such as the Packet Delivery Ratio (PDR) or Packet Inter-Reception Time (PIR). Focusing on NR-V2X, we relate the AoI to the concepts of service availability and reliability, and investigate the impact of blind retransmissions on the AoI performance. Going beyond the assumption of exogenous data arrivals, we investigate the joint impact of the traffic generation process (sampling rate) and the channel access mechanism. The analysis reveals that in the presence of time-correlated errors, caused by consecutive packet loss due to simultaneous reservations, it is beneficial to use retransmissions instead of a higher sampling rate. For a realistic evaluation, we use an NR-V2X simulator in OMNET++ and simulate a SUMO scenario.