Recently, the fast growth of communication technology has led to the design and implementation of different types of networks in different environments. One of these remarkable networks is vehicular ad hoc network (VANET).The ubiquitous connectivity among vehicles is possible through VANET in the absence of fixed infrastructure. Moreover, it provides safety and comfort to people sitting in the vehicles. In this regard, collecting information from vehicles that are moved constantly is an essential challenge. To develop an efficient method for data collection in the VANET, some parameters must be considered such as data aggregation, latency, packet delivery ratio, packet loss, scalability, security, transmission overhead, and vehicle density. Since data collection has a significant importance in the VANET, the aim of this study is to investigate the existing methods and describe the types of important issues and challenging problems that can be addressed in data collection in the VANET. The data collection techniques are investigated in four primary groups, namely, topology-based, cluster-based, geocast-based, and fog-based.Also, the mentioned parameters are important to compare all of the presented techniques. KEYWORDS communication architecture, data collection, VANET, vehicle-to-vehicle communication, vehicular ad hoc networks
| INTRODUCTIONOne of the growing disruptive innovation is the Internet of things (IoT), which allows physical devices to communicate over heterogeneous networks. 1-3 Moreover, one of the IoT applications is vehicular ad hoc network (VANET), 4 which has been developed as a powerful technology aimed at providing safety and comfort to people sitting in the vehicles. 5,6 Moreover, it affords wireless communication among vehicles, and dynamic traffic data is transferred with a high accuracy and low cost. 7,8 The VANET is a module of intelligent transportation systems (ITS) and a subdivision of mobile ad hoc network (MANET). 9,10 Typically, the vehicles are armed with sensing equipment and have a high storage and processing capacity. 11 The unique features of the VANETs include higher node density, instability of wireless channel and limited bandwidth, predictability of vehicular pathway, highly dynamic network topology that change quickly and repeatedly, sufficient energy and resources, and hard delay constraints. 12-14 A large scale of VANET is foreseen to be available in the near future because of the rapid growth of vehicles equipped with communication abilities. 15 The data dissemination and the data collection of vehicles are two significant factors supported by VANET. 16