Application-Level Multicast-Assisted MQTT for Emergency Message Dissemination in Vehicle-to-Everything Networks

This paper presents an Application-Level Multicast (ALM)-assisted MQTT approach that enhances the efficiency of the emergency message dissemination in Vehicle-to-Everything (V2X) environments. The proposed approach introduces a shared buffer mechanism, which allows multiple subscriber sockets to reference a single message instance, and asynchronous socket writes, which enable concurrent data transmission to multiple subscribers. These mechanisms jointly minimize broker-side latency and memory consumption, facilitating near-simultaneous message delivery to numerous vehicles. Performance evaluations demonstrate that the proposed ALM-assisted MQTT significantly reduces message delivery latency and memory usage compared to conventional MQTT, making it suitable for delay-sensitive V2X emergency scenarios.