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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

Nowadays, with the rapid progress of Internet-based and distributed systems such as cloud computing, peer-to-peer networking, and Internet of Things (IoT), significant improvements in almost every engineering and commercial field have been made. On the basis of IoT, smart cities are formed utilizing intelligent information processing, universal connectivity, ubiquitous sensing, and real-time monitoring. Energy conservation is one of the significant issues in current IoT development due to the poor battery endurance of IoT objects. Over the last years, with smart cities' explosive growth, a huge range of studies regarding energy efficiency have been done. The diversity of sparse data and multi-sourcing is utilized in developing IoT scenarios. In order to use efficiently of these data to improve the IoT services, data fusion plays an important role. It saves network resources, improves data transmission efficiency, and extracts useful information from raw data. To the best of our knowledge, there is still a lack of a comprehensive and systematic study about surveying and analyzing the available energy-efficient data fusion techniques in the IoT. Thus, this article aims to address this gap using a systematic method.

In recent years, cloud manufacturing (CMfg) has been developed as an intelligent manufacturing system, in which geographically distributed manufacturing resources are available as services in the cloud platform. Choosing and integrating single services into a combined service to fulfill the client's requests requires higher emphasis. However, by increasing customers' trend to utilize CMfg, service providers are encouraged to publish services with various functional and non-functional characteristics. Thus, service composition and optimal selection has become one of the most challenging topics in CMfg. Hence, an inclusive review of current studies on this NP-hard issue is extremely desirable. This article first, selects the recent studies in the field of single-objective service composition in CMfg and classifies and surveys them comprehensively in terms of QoS parameters, energy consumption, user constraint, and so forth. This article aims to provide a useful roadmap for future researchers who are intended to explore novel work in this field. The search for articles was conducted in November 2020.

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