# Smart Bandwidth Assignation in an Underlay Cellular Network for Internet of Vehicles
## 1 Introduction  
Cooperative driving is expected to provide advance services in order to increase road safety, improve traffic management and create different new business opportunities for mobility services. In this way, the automobile industry is expected to increase their profit margin of Euro 54 billion in 2012 to Euro 79 billion by 2020 [1]. In the scenario of ITS, cooperative vehicular systems are a key factor not only to report information to the drivers in real time but also to gather accurate information about the traffic flow and events that occur during driving. Then, vehicles in a VANET can be considered as moving nodes that can address FCD (Floating Car Data), thanks to the creation of V2V and Vehicle-to-Infrastructure (V2I or I2V) links, giving rise to -ITS (Cooperative-ITS) [2]. In this context, the evolution of the Internet of Things (IoT) paradigm into new application scenarios as VANETs, introduced the definition of new terms such as Internet of Vehicles (IoV) [3], creating a development framework that requires specific QoS attributes, as very a low latency to provide fast response to the events on the road [4]. Then, moving the concept of IoT into IoV, we find an ecosystem where vehicles (cars, trucks, motorbikes) and elements of the infrastructure (signals, sensors, actuators, etc. ), besides pedestrians in an urban scenario, are interconnected thanks to an IP-based communication platform. Therefore, all these nodes (static and in movement at very different relative speeds) can generate, aggregate, consume and exchange information directly (using device-to-device communications) orindirectly (through a traffic management center, for example), with the goal of resolving different kinds of events, to result in providing a more safe, efficient and eco-friendly Intelligent Transport Systems. As a result of this information exchange, vehicles can benefit from the information which might have been generated not only by surrounding information sources (sensors located on the road, elements of the infrastructure) but even by other vehicles that are located at a certain distance, for example, to obtain information about the traffic density on the road. Nevertheless, a cooperative vehicular scenario like this must face multiple communication challenges, such as the adverse propagation conditions, high vehicles' mobility pattern and their unpredictable direction of motion, not to mention the limited communication resources. Then, the technologies adopted to provide the communication architecture are a key factor that determine the performance of the network. Two candidate technologies are competing to enable V2X (Vehicle-to-Everything) communications: IEEE 802.11p and cellular network communications. Although IEEE 802.11p was specifically designed for V2X communications and to cater for ITS applications, it suffers from certain technical limitations. The main identified deficiency is poor performance in high vehicle density scenarios resulting from the MAC (Medium Access Control) layer implementation based on a regular IEEE 802.11 CSMA (Carrier Sense Multiple Access). Moreover, it does not guarantee the QoS which is essential to fulfill the different performance requirements of ITS applications [5; 6]. In the scope of cellular networks, LTE-A supports D2D (Device-to-Device) functionality since 3 GPP Rel.12, so it has already been tested in other IoT scenarios where nodes are static with the aim of maximizing the energy efficiency of the nodes. However, this technology was not meant to meet stringent V2X requirements in terms of latency, reliability and mobility. These limitations have motivated the research community to investigate cellular-based V2X communications. Additionally, D2D systems offer four different types of gain, i.e., proximity gain, hop gain, pairing gain and reuse gain. Based on these advantages, the applicability of D2D techniques for V2V communications has been analyzed in different works, such as [7].