Internet of Things in Smart Cities: Comprehensive Review, Open Issues and Challenges

Smart cities rely mainly on the Internet of Things (IoT) to make an urban area smart to offer its citizens a high quality of life with optimal use of resources and preservation of the environment. IoT is the key component that collects raw data on the surrounding environment to be analyzed to extract information that supports decision-making. The widespread use of IoT results in the emergence of smart homes, smart energy, smart transportation, and smart healthcare, which build a smart city. On the other hand, challenges such as heterogeneity, scalability, security, and privacy hinder the efficient functioning of the IoT in the construction of smart cities. This article presents a comprehensive overview on the concept of IoT moving forward to the concept of smart city, highlighting key elements and characteristics, studying and reviewing state-of-the-art research on this theme. Future directions are discussed to guide researchers, who focus on interoperability between IoT platforms in smart cities and on IoT architectures based on micro-services. Case studies of successful smart cities are presented for gaining learned lessons. The impact of integrating wireless networks (5G and 6G) in the IoT is also clarified in the future direction. The significance of this research is found in its comprehensive examination of various aspects of the smart city instead of concentrating on a singular facet.