## 1 Introduction  
The concept of Smart City is so broad and relatively immature that its scope is not yet fully defined. The main motivation behind this concept comes from the efficient use of the available resources [1]. The implementation of the triad computing, communication and sensing can increase the efficiency levels significantly in several areas such as hydraulic resources, waste management, crime control, traffic management and transportation, among others. Within the different notions of what a Smart City should provide, Intelligent Transportation Systems (ITS) emerge as a promising idea to increase efficiency in fuel use, gas emission, routes optimization and drivers' safety [2]. In a world society where approximately 1.35 million people die annually in a traffic-related accident, which is the eighth leading cause of death for people of all ages and the first for people between 5 to 29 years old [3]; the use of ITSs could play an important role towards the solution of this critical problem. Its approach to solving this scourge is to make vehicles go beyond human deficiencies, which means vehicles with the ability to sense their surroundings and act accordingly. In addition, the automotive companies are continuously increasing the number of sensors inside their cars to improve the user experience and increase the automation of the overall system. The rising need for electric vehicles for pollution control and the increasing trend towards the expectations of autonomous vehicles are the main demands that have ensured high growth in the development and the introduction of more sensors inside the vehicles. In fact, the automotive sensor market was valued at $13,293.2 million in 2017 and is projected to reach $30,858.5 million by 2025, growing at a compound annual growth rate (CAGR) of 11.1% from 2017 to 2025 [4]. The integration of these sensors will support advanced driver assistance systems (ADAS). The next generation of autonomous vehicles that will assist or completely replace the driving system in vehicles will be implemented on top of this technology. As a result, there has been extensive research on ADAS systems in recent years, the variety of on-board sensors (e.g., radars, cameras, and LiDARs) are used to reduce the number of traffic accidents and deaths [5]. Although ADAS applications are still in the early stages, they will transform the driving experience and simultaneously provide road safety. ADAS will soon replace the humans behind the wheel of the car, reducing the number of accidents and allowing cars to be driven efficiently. These assisted systems will require the use of robust high-precision and redundant sensors for their full operation. In this sense, in the automobile industry, semiconductor companies will play a key role in the development of these technologies. New trends for automated vehicle systems promise vehicular linking with cloud-based applications and wireless connections with their surroundings. The fusion of these sensors as a robust communication system will allow the implementation of systems such as adaptive cruise control, extension of operational area, collision warning or mitigation on moving and still objects, top view, pedestrian protection/recognition, traffic jam assist, intersection/turning assist, overtaking assistance and construction area assistance, which are key enablers in driverless cars [6]. It is in this context that the term vehicle-to-everything (V2X) communication is defined. This concept performs a key role in the ITS environment, being the way of sharing and collecting knowledge between intelligent elements (e.g., another vehicle, building, traffic light). V2X communication will pave the way to exchange information between the different applications of ITSs related to traffic safety and efficiency, automation driving, information, and entertainment (infotainment). The term includes but is not limited to, Vehicle-to-Vehicle (V2V), Vehicle-to-Network (V2N), Vehicle-to-Pedestrian (V2P), and Vehicle-to-Road Infrastructure (V2I) communication [7].