Dynamic Contention Window based Safety-Application Model for Vehicular Ad-hoc Networks

Abstract

The paper proposes a dynamic contention window based safety-application model to provide service to the Event Driven Messages (EDMs) over the beacon messages by varying the Contention Window (CW) size dynamically. This is done to ensure timely distribution of EDM as these messages are most critical messages and require immediate transmission in order to maintain the essence of the network. For prioritization, whenever the vehicular network detects an EDM, the system holds all the beacon messages, prioritizing EDMs and reduces the CW size by a pre-defined factor. This factor is continuously increased if consecutive EDMs are received at the vehicles queue. Consequently, for broadcasting beacons in the absence of EDM, the proposed model first evaluates backlogged packets, which is estimated by using round trip time and varies the size of CW accordingly. This is done to maintain the network performance even in the absence of EDM. The model is validated against the simulation result. It can be evident from the simulation results that our model provides smallest CW without degrading the performance of the network in terms of collision probability.