In recent years, vehicular communications have gained the attention of researchers, developers and companies due to their applicability in multiple fields. This attention has also been fueled by the continuous spread of new radio technologies, most notably LTE first and recently 5G, paired by the continuous evolution of Wi-Fi 802.11. In general, the contribution of my work is the investigation of possible applications of these new technologies, that can be used both alone and combined, to improve vehicular safety in urban and suburban scenarios.
In this thesis, I plan to explore the dynamic orchestration of different radio technologies available in a typical urban scenario, where cellular coverage and 802.11ac connectivity are available. First, normal operating conditions are considered, where all cars in the scenario benefit from the simultaneous adoption of both radio technologies. Then, when a disruptive event occurs, e.g., a car crash, the use of combined technologies is confined only to a specific vehicle, that might be an ambulance, a police car or an emergency vehicle, in order to better support data communications useful to manage the emergency condition; this happens at the expense of nearby vehicles, that are confined to only one radio interface, i.e., LTE. To perform this study, I have developed an ns-3 based urban vehicle simulator, where mobility has been modeled using SUMO, with a population of 50 vehicles plus the emergency one that takes over at a given time. The simulative results I have obtained are compared with experimental data obtained using a testbed equipped with 8 Software Defined Radios (SDRs), located in Dresden (Germany). Each SDR pair can be used to emulate either the LTE base station and Wi-Fi Access Point, or the receiving station, i.e., a vehicle equipped with both LTE and the 802.11 radio interface. On the testbed, my focus has been on the communication from and to the ambulance, and on its perception of the communication channel state in the presence of different traffic levels, emulated using one SDR as noise generator.