# Social Internet of Vehicles for Smart Cities
## 1 Introduction  
Smart cities are areas where innovation is supported through digital networks and applications [1]. Smart cities are often called sustainable, digital or connected cities [2]. The goal of converting a city into a smart environment is to alleviate the problems resulting from urbanization and increased urban population. A smart city is an urban area that provides the conditions for sustainable economic growth and quality of life. Smart solutions, like traffic congestion avoidance [3], green buildings [4] and modern industrial control systems (ICS) [5], are some of the technologies that can make today's urbanization sustainable. A smart city involves the intelligent use of technology to improve how people live, work, commute and share information [6]. A key aspect of a smart city is next generation vehicles that incorporate new sensing, communication and social capabilities as part of the wider Internet of Things concept. By providing mobile wireless sensing and communications, vehicles can facilitate data access, which is fundamental to make smart cities a reality. Wireless networks can be divided into three main categories. First, infrastructure wireless networks rely on a central station that coordinates all communications [7]. Second, non-structured networks or _ad hoc_ networks give equal roles to all stations in the network [8, 9]. Third, hybrid networks combine the first two categories [10]. An example of hybrid networks is hybrid vehicular _ad hoc_ networks (hybrid-VANETs) [11], which use _ad hoc_ networks for communication between vehicles and infrastructure networks, such as wireless local area networks (WLANs) and cellular systems for communication with a core network [12, 13]. Smart vehicles, through their advanced communication capabilities, will be able to interact not only with navigation and broadcast satellites,but also with passenger smart phones, roadside units and other smart vehicles, making them an important component of IoT and the development of smart cities [14]. VANETs combine these with new applications and methods to enable the intelligent communication between vehicles and the connection to the Internet. VANETs rely on roadside units (RSU) and on-board units (OBU) to facilitate the connectivity and the intelligence of the smart vehicle. RSUs are communication infrastructure units that are positioned next to roads to connect vehicles to a larger infrastructure or to a core network, such as a metropolitan traffic management system. The OBU is a network device integrated into smart vehicles that supports different wireless networks, such as dedicated short-range communication (DSRC) and WLAN. A VANET has a diverse range of applications, from road safety, through the detection and avoidance of traffic accidents [15], traffic control, through reduction of traffic congestion [16], as well as infotainment, through the improvement of driving comfort [17]. Recently, three of the biggest companies that provide digital content and operating systems for mobile devices, Google, Apple and Microsoft, have announced their actions toward taking over the in-car infotainment system with their operating systems dedicated to vehicles and mobile devices (CarPlay, Android Auto and Windows Mobile) [18]. The Social Internet of Things (SIoT) [19] is a network of intelligent objects that have social interactions. The Social Internet of Vehicles (SIoV) [20, 21] is an example of a SIoT where the objects are smart vehicles. The authors in [21] designed analytical models of the subsystems involved in the SIoV interaction process and proposed models that could be useful in order to deploy Social Internet of Vehicles (SIoV)-based safety, efficiency or comfort applications. Although the basic rules are the same for both social networks of humans and social networks of vehicles, there are significant differences in terms of the dynamic nature of the entities, their social interactions, the topology of the network, privacy concerns and security issues that arise.