Using RA-TDMA to support concurrent collaborative applications in VANETs

Vehicular Ad-hoc Networks (VANETs) have a significant potential to enable new applications among multiple types of vehicles. In these networks, the Medium Access Control (MAC) plays an important role in providing an efficient communication channel. Currently, existing standards use the PHY and MAC of IEEE 802.11p, which is fully distributed and based on Carrier Sense Multiple Access with collision Avoidance (CSMA/CA), thus still prone to collisions. This has led to recent proposals for TDMA-based overlay protocols to prevent collisions, including one based on Reconfigurable and Adaptive TDMA (RA-TDMA). This protocol sets a TDMA round allocating slots to the nodes engaged in a given collaborative application, only, e.g., a platoon or a multimedia group. Then, other traffic, including from other TDMA rounds of concurrent applications can co-exist in space and time using the native CSMA/CA mechanism of IEEE 802.11p and the synchronization mechanism of RA-TDMA. In this paper, we do a qualitative comparison among TDMA protocols in VANETs showing the advantages of RA-TDMA. Early experimental results validate the capacity of RA-TDMA to support multiple concurrent rounds in a scalable manner.