# Design, Deployment and Evolution of Heterogeneous Smart Public Lighting Systems
## 1 Introduction
Apart from enabling the remote control of each luminaire independently of the others, as well as the remote monitoring of its functional parameters (power consumption, lamp temperature, electrical parameters), this widespread network allows to collect data gathered by sensors (air pollution, vehicular traffic, water flooding, etc.) possibly mounted on streetlights, or transmitted by IoT wireless devices located in their surroundings. For instance, smart streetlights equipped with wireless communication interfaces can detect nearby vacant parking lots and inform interested drivers; they can alert waste collectors when the neighborhood bins need to be emptied, or can monitor the traffic flow and send key data to an intelligent transport system platform. Ultimately, according to the smart lighting paradigm, streetlights are no longer isolated elements, but establish a capillary, multifunctional, city-wide communication network, capable of relaying information, gathering data and delivering services to and from millions of IoT devices. Public smart lighting becomes a dynamic platform serving as a backbone for \"smart city\" developments. Cities can thus rethink the role of the public-light asset, which offers opportunities to deliver new services and generate revenues, instead of just being a cost factor. Moreover, smart lighting infrastructure might play a crucial role also for 5G (and beyond) cellular networks. In fact, the need to provide cellular users with ever-increasing transmission rates, necessarily calls for ever-smaller cells, along with the adoption of massive MIMO antennas and millimeter wave communications. To meet both the seamless coverage requirement at such high frequencies (which requires line-of-sight propagation) and the desired data rate for each user, the spatial density of 5G base stations (BSs) is anticipated to come up to 40-50 base stations/km\({}^{2}\)[14]. Future 5G networks will be, therefore, ultra-dense; in this perspective, the integration of smart lighting infrastructures and 5G networks is a great opportunity, as the streetlight density in urban environments perfectly meets the ultra-dense deployment requirement of next generation cellular networks, with the additional benefit that the 5G BSs would find the power supply already available in each light fixture. Focusing attention on LED streetlights, the paper is organized as follows. Section 2 is a survey of the literature on smart street lighting, whereas Section 3 discusses the general architecture of a smart lighting infrastructure and its main tasks. Section 4 focuses on the savings that can be achieved thanks to remotely controlled LED fixtures. The different communication technologies that can support the smart lighting service are thoroughly presented in Section 5, where their advantages and downsides are discussed. Section 6 describes the steps needed for the deployment of a smart lighting infrastructure,whereas Section 7 outlines the IoT services that such infrastructures may provide in the next future as well as their integration with 5G networks. Final conclusions are drawn in Section 8.