# IoT-Enabled Smart Sustainable Cities: Challenges and Approaches
## 1 Introduction
Consequently, through the introduction of IoT innovation, smart sustainable cities can improve different aspects of their urban management (as shown in Figure 1), for instance, urban mobility, public transportation, e-governance, safety, security, public lighting, and environmental monitoring. The adoption of IoT technologies is expected to allow to monitor, control, and manage all the available resources, such as electric power, soil, water, people, and so on. Figure 1: Key areas to deal with in a smart city. In order to reach these challenging objectives, the first step is represented by the definition and deployment of a reliable connectivity infrastructure that, in most cases, is supported by wireless networks--as they enable an information exchange with a more flexible and low-cost deployment than wired ones. Nevertheless, due to the complexity of sustainable smart city scenarios, in most cases heterogeneous communication technologies and different network architectures should be adopted, depending on the characteristics of specific services that need to be implemented (e.g., required low or high data bit rate), or operational constraints (e.g., the availability of a power source), the area to be covered (implying long-range or short-range communication links), and other aspects proper of the specific scenario to be dealt with. After the deployment of a reliable connectivity infrastructure, which represents the backbone of an IoT-based smart city, it is possible to define the application level in different aspects of urban management, leading to the implementation of services of interest for citizens and institutions. The aim of this paper is twofold: (i) we provide a review of the literature on smart cities, based on different indicators, and (ii) we address the main challenges and propose solutions related to the improvement of these indicators. Through the analysis of the existing literature, we identify the key challenges and propose IoT-based solutions on how a medium-sized city, such as the city of Parma, Emilia Romagna region, Italy, could improve the services offered to its citizens. In this way, we want to give a reference to researchers, companies, and institutions from different areas to suggest the main challenges that future smart cities have to face in different technological contexts, together with insights and references for smart cities' administrators, giving them the opportunity to better approach the technological revolution that will pave the way to the smart cities of the future. The rest of the paper is organized as follows. In Section 2, we provide an overview on primary topics to be taken into account in a smart city, namely, the connectivity infrastructure and the set of indicators to be satisfied. Section 3 presents an overview of possible solutions which a municipality can introduce considering different application areas, with particular attention to the choices of the city of Parma. In Section 4, we deepen our analysis on the smart sustainable urban mobility topic, which represents one of the key evolution directions for the future of a smart city. In Section 5, an overview on global future research directions is discussed. Finally, in Section 6 we draw our conclusions.