Persistent Scheduling with Broadcast Feedback for Cellular V2X Communication

In New Radio (NR) Sidelink Mode 2 for vehicle-to-everything (V2X) communication, each vehicle autonomously selects the wireless resource through sensing-based resource selection and reservation. Since perfect sensing and coordination in distributed scheduling is impossible, resource collisions in the resource reservation are unavoidable. NR V2X copes with the problem by frequently changing resources, which also helps resolve the resource collisions with the vehicles that newly come into the mutual communication range. However, the random and frequent hopping between resources can itself cause resource collisions, which eventually leads to performance degradation by reducing the effectiveness of sensing. In this paper, we explore an alternative approach that does not require such frequent resource switching. We use a persistent scheduling where the selected resource is not changed unless there is an actual resource collision. To cope with the coincidental resource collisions, however, we supplement it with a broadcast feedback scheme. We show that the proposed scheduling approach leads to better performance than the standard semi-persistent scheduling scheme in terms of packet reception ratio (PRR), number of persistent collisions, and the length of consecutive collision events. The performance edge is maintained even with vehicle population churn.