Resumo:
Vehicular Ad hoc Networks (VANETs) constitute a specific type of mobile ad hoc network in which nodes are vehicles capable of sending and receiving messages directly between each other using wireless communication links, enabling the creation of several distributed applications without the dependence on a specific infrastructure for vehicle communication. In urban and highway environments, VANETs have been seen as an opportunity in the development of Intelligent Transportation Systems (ITS), aiming not only to improve traffic flow, security, and well-being but also to reduce pollutant emissions. However, many distributed applications for ITS require groups of vehicles to coordinate their actions consistently, reliably, and with temporal constraints. Nevertheless, in VANETs formed in urban and highway environments, vehicles travel along pathways exhibiting a mobility pattern and highly dynamic communication structure. Therefore, network topology changes, communication link disconnections, and message losses are frequent in a VANET. Hence, meeting the requirements for vehicle coordination in distributed ITS applications based on VANETs represents a challenge. In this context, this work proposes the Vehicular Causal Block Protocol (VCBP) to support the vehicle coordination requirements in distributed ITS applications based on VANETs. The proposed group communication protocol offers the facility of message multicast with guarantees of reliable delivery, temporal constraints, and causal and total ordering of messages. VCBP has been implemented and evaluated in a vehicular network simulation environment, and its performance has been compared with other protocols available in the literature. The results show that VCBP can provide enhanced message delivery guarantees with a message delivery rate similar to or better than other evaluated approaches.
