Non-Negotiated Implicit ETSI VAM Clustering

Abstract: Including Vulnerable Road User (VRU) in Cooperative Intelligent Transport Systems (C-ITS) framework aims to increase road safety. However, this approach implies a massive increase of network nodes and thus is vulnerable to medium capacity issues, e.g., contention, congestion, resource scheduling. Implementing cluster schemes -- to reduce the number of nodes but represent the same number of VRUs -- is a direct way to address the issue. One of them is suggested by European Telecommunications Standards Institute (ETSI) and consists of nodes (connected pedestrians and cyclists) sending vicarious messages to enable a leader node to cover for a cluster of VRUs. However, the proposed scheme includes negotiation to establish a cluster, and in-cluster communication to maintain it, requiring extra messages of variable sizes and thus does not fully resolve the original medium capacity issues. Furthermore, these exchanges assume network reliability (i.e. a lossless channel and low latency to meet time constraints). We propose a method for VRU Awareness Message (VAM) clustering where 1) all cluster operations are performed without negotiation, 2) cluster leaders do not require sending additional messages or meet deadlines, and 3) assumes a lossy communication channel and offers a mechanism for cluster resilience. Our results show the feasibility of the concept by halving message generations compared to individual messages while keeping the awareness levels (i.e., that VRUs are accounted for).