# A Comprehensive Study of the Use of LoRa in the Development of Smart Cities
## 1 Introduction  
The New Urban Agenda (Agenda 2030) adopted at the United Nations Conference related to Sustainable Urban Development (Habitat III) in the year 2016, has the goal of prompting cities to archive the identified Sustainable Development Goals by the year 2030. The Agenda 2030 states that \"well-planned and well-managed urbanization can be a powerful tool for sustainable development\". In this context, cities can experiment strategies of circular economy for the optimization of resources, waste reduction, reuse, and recycling [1].  
Under the perspective of a circular economy, a city focuses on waste management, keeps assets, and enables digital technology. A study [2] identified several sectors for the implementation of a circular economy in a city. Those sectors are: built environment, energy, mobility, waste, toilets, industrial production, agri-food, citizens, and communities. Indicators and criteria of circularity in built environments proposed in this study [2] are shown in Table 1.  
The inclusion of IoT is considered an important enabler of circular economy in a smart city. The above-mentioned study [2] considers IoT relevant to producers and designers, as they can obtain feedback in real time about products and infrastructures and keep materials in constant circulation. On the other hand, the work about IoT discussed by the Ellen MacArthur Foundation in the World Economic Forum mentioned that intelligent assets can sense, communicate, and store information bythemselves. Therefore, this could lead to products that can monitor their deterioration and alert the user, figure when they need to be repaired, and schedule their own maintenance [3].  
The smart city intends to convert its existing infrastructure into intelligent goods that are capable of providing enough information to make decisions more efficiently in real time. To achieve this goal, millions of sensors around the globe need an efficient, long-range, and low-energy-consuming technology. Low-Power Wide-Area Network (LPWAN) solutions like LoRa, SigFox, and NB-IoT meet these requirements [4].  
The data generated by the components of an IoT ecosystem can contribute in two relevant ways to a smart city model: (1) in the generation of a circular economy and (2) in the creation of intelligence to improve decision-making processes by citizens or city managers.  
The aim of this study is the comprehension of technological and functional aspects of IoT based on LoRa, which could support the development of a circular economy and help to generate smarter solutions for decision-making. LoRa has attracted the interest of researchers because it is an open standard, which contributes to the development of sustainable smart cities, since they are linked to the concepts of circular economy. Additionally, the intention of this work is to identify the technological or practical barriers that have limited the development of solutions and to find possible future trends that could exist in the context of smart cities and IoT and how they could be exploited by the industry and academy.  
The rest of the present paper is structured as follows. Section 2 presents the state of the art of smart city, IoT, and LoRa technology. Section 3 presents the method used for the qualitative analysis. Section 4 presents an analysis of the results obtained from a systematic literature review (SLR), with the purpose of determining the main aspects that have made LoRa one of the most used technologies in the development of smart cities applications. Then, Section 5 discusses the strengths and weaknesses of LoRa-based implementations, and finally Section 6 presents our conclusions.