Adaptive Expiration Time for Dynamic Beacon Scheduling in Vehicular Ad-Hoc Networks

In Vehicle Ad-hoc Networks, beacon is generated periodically to provide adequate awareness of the surrounding vehicles and environment. Generating periodic beacons at the same rates for all vehicles, typically high rates for safety applications, consume sizeable resources on communication channel. This is in turn presents a challenge to a reliable and successful delivery. This problem gains a lot of attention and researchers started to come up with many fundamentally different solutions to adjust beacons rate for better scalability. However, adjusting beacon rate without a good estimate of beacon data lifetime may impact the accuracy of the awareness of the surrounding vehicles. Particularly, for the applications and protocols that require knowledge about network topology. Accordingly, we propose a new mathematical formula, Adaptive Expiry Time (AET), to determine the lifetime of beacon data. It is independent of beacon scheduling interval and based on neighbour position, speed and orientation. It has been evaluated using proposed Dynamic Beacon Scheduling (DBS) that adjusts beacon interval according vehicle speed. Furthermore, it has been compared to different approaches of expiry time, such as Constant Expiry Time (CET), Variable Expiry Time (VET).