Because of the rapid rise of the population density inside urban environments, substructures and services have been needed to supply the requirements of the citizens. Accordingly, there has been a remarkable growth of digital devices, such as sensors, actuators, smartphones and smart appliances which drive to vast commercial objectives of the Internet of Things (IoT), because it is possible to interconnect all devices and create communications between them through the Internet [1
]. In the past, it was difficult or even impossible to combine these digital devices. Likewise, gathering their information for day-to-day management of activities and long-term development planning in the city is essential. For example, some public transport information, e.g., real-time location and utilization, occupancy of parking spaces, traffic jams, and other data like weather conditions, air and noise pollution status, water contamination, energy consumption, etc. should be gathered continuously. To this end, different technologies have been applied to address the specific features of each application. The required technologies cover a wide range and layer from the physical level to the data and application layers. One of these technologies, proposed in [2
], considered a two-way relay network with an orthogonal frequency division multiple accesses to achieve higher efficiency in smart grid communications.
The IoT archetype is in the power of smart and self-configuring devices which are well linked together by global grid infrastructures. IoT can be typically defined as a real object, largely dispersed, with low storage capabilities and processing capacities, while aiming at enhancing reliability, performance and security of the smart cities as well as their infrastructure [3
]. On this basis, in the present paper, a survey of the IoT-based smart cities information from related reports is conducted.
The IoT consists of three layers, including the perception layer, the network layer, and the application layer, as shown in Figure 1
. The perception layer includes a group of Internet-enabled devices that are able to perceive, detect objects, gather information, and exchange information with other devices through the Internet communication networks. Radio Frequency Identification Devices (RFID), cameras, sensors, Global Positioning Systems (GPS) are some examples of perception layer devices. Forwarding data from the perception layer to the application layer under the constraints of devices’ capabilities, network limitation and the applications’ constraints is the task of the network layer. IoT systems use a combination of short-range networks communication technologies such as Bluetooth and ZigBee which are used to carry the information from perception devices to a nearby gateway based on the capabilities of the communicating parties [4
]. Internet technologies such as WiFi, 2G, 3G, 4G, and Power Line Communication (PLC) carry the information over long distances based on the application. Since applications aim to create smart homes, smart cities, power system monitoring, demand-side energy management, coordination of distributed power storage, and integration of renewable energy generators, the last layer which is the application layer, is where the information is received and processed. Accordingly, we are able to design better power distribution and management strategies [5
The smart city is becoming smarter than in the past as a result of the current expansion of digital technologies. Smart cities consist of various kinds of electronic equipment applied by some applications, such as cameras in a monitoring system, sensors in a transportation system, and so on. Furthermore, utilization of individual mobile equipment can be spread. Hence, with taking the heterogeneous environment into account, various terms, like characteristic of objects, participants, motivations and security policies would be studied [6
]. Reference [7
] presented some of the key features of potential smart cities in 2020. Smart citizens, smart energy, smart buildings, smart mobility, smart technology, smart healthcare, smart infrastructure, smart governance and education and finally smart security are the aspects of smart cities. The features of a smart city are shown in Figure 2
In an IoT environment, devices can be aggregated according to their geographical position and also assessed by applying analyzing systems. Sensor services for gathering specific data are utilized with some ongoing projects regarding the monitoring of each cyclist, vehicle, parking lot and so forth. There have been a lot of service domain applications which utilize an IoT substructure to simplify operations in air and noise pollution control, the movement of cars, as well as surveillance and supervision systems.
The developments on the Internet provide a substructure that enables a lot of persons to interlink with each other. The following development on the Internet may make it more applicable to arrange proper interlinks between objects. In 2011, the number of interconnected things was far higher than the amount of population [8
]. Figure 3
shows the interconnection among the various objects based on the IoT [8
]. Consequently, providing IoT improves cities and affects the different features of humans’ life by creating cost-effective municipal services, enhancing public transformation, reducing traffic congestion, keeping citizens safe and healthier. Moreover, it plays a vital role in the national level associated with policy making (e.g., energy conservation and pollution reduction), monitoring systems, and needed infrastructures. Thus, it helps to supply a system with more efficiency, lower cost and more secure operation through energy conservation rules, economic attention as well as reliability level.
In personal and home applications, it can provide not only virtual entertainment but also real friendships. Controlling appliances like refrigerators and washing machines by IoT makes houses offer better energy management. Through the expansion of body area networks at home, it is possible to monitor the health situation of the elderly in their house, and this reduces treatment costs. Social networking applications like Facebook can collect the people of a city for an event or ceremony. It is helpful for making a connection with self-created communities either in texting, video or voice framework [8
Since traffic congestion causes remarkable costs for a city from an environmental and citizen’s time wasting perspective, smart transportation and logistics can help to mitigate the impact. Dynamic traffic information, online monitoring of travel times, route choice behavior can be conducted through the transport IoT and large scale WSNs. They also can develop stochastic models for mitigation plans and design algorithms for traffic control. Monitoring air and noise pollution by sensors within a IoT framework can help to take possible steps for reducing environmental concerns. Moreover, social services like providing better water quality and waste management can be obtained by monitoring water sources and water distribution systems.