Distributed time synchronization mechanism for large-scale vehicular networks

The performance of Vehicular Ad hoc Networks (VANETs) is greatly affected by the design of Medium Access Control (MAC) protocol adopted by these networks. In large-scale networks, the MAC protocol of the IEEE 802.11p standard may fail to provide the required Quality of Service (QoS) provisioning, in terms of delay and reliability, for safety-related applications. Therefore, new MAC mechanisms should be implemented to overcome the scalability problems and deal with the communication issues. In this paper, we propose a Distributed Time Synchronization (DTS) mechanism for cluster-based multilayer large vehicular networks. Our mechanism divides the communication area to intra-cluster communication domain and inter-cluster communication domain. In the DTS mechanism, the Road Side Unit (RSU) does not synchronize the communication of the entire network, it just manages the time synchronization of the Cluster Heads (CH) in its immediate vicinity. The remaining part of the network is synchronized in a distributed manner by the CHs themselves. To avoid data loss, each CH is equipped with a finite buffer that stocks the packets received from other CHs or from the vehicles in the clusters. We develop an analytical model to evaluate the performance of the DTS mechanism.