energies Review A Review of Smart Cities Based on the Internet of Things Concept Saber Talari 1, Miadreza Shafie-khah 1,2,*, Pierluigi Siano 2, Vincenzo Loia 3, Aurelio Tommasetti 3 and João P. S. Catalão 1,4,5 1 C-MAST, University of Beira Interior, R. Fonte do Lameiro, 6201-001 Covilhã, Portugal; [email protected] (S.T.); [email protected] or [email protected] (J.P.S.C.) 2 Department of Industrial Engineering, University of Salerno, 84084 Fisciano (SA), Italy; [email protected] 3 Department of Management & Innovation Systems, University of Salerno, 84084 Fisciano (SA), Italy; [email protected] (V.L.); [email protected] (A.T.) 4 INESC TEC and Faculty of Engineering of the University of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal 5 INESC-ID, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal * Correspondence: [email protected]; Tel.: +351-275-242055 Academic Editor: Joseph H. M. Tah Received: 8 January 2017; Accepted: 20 March 2017; Published: 23 March 2017 Abstract: With the expansion of smart meters, like the Advanced Metering Infrastructure (AMI), and the Internet of Things (IoT), each smart city is equipped with various kinds of electronic devices. Therefore, equipment and technologies enable us to be smarter and make various aspects of smart cities more accessible and applicable. The goal of the current paper is to provide an inclusive review on the concept of the smart city besides their different applications, benefits, and advantages. In addition, most of the possible IoT technologies are introduced, and their capabilities to merge into and apply to the different parts of smart cities are discussed. The potential application of smart cities with respect to technology development in the future provides another valuable discussion in this paper. Meanwhile, some practical experiences all across the world and the key barriers to its implementation are thoroughly expressed. Keywords: cloud platform; Internet of Things (IoT); smart city; demand response 1. Introduction 1.1. Concepts 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 Energies 2017, 10, 421; doi:10.3390/en10040421 www.mdpi.com/journal/energies Energies 2017,, 10,, 421421 2 of 23 considered a two-way relay network with an orthogonal frequency division multiple accesses to achieverelay network higher with efficiency an orthogonal in smart frequencygrid communications. division multiple accesses to achieve higher efficiency in smartThe grid IoT communications. archetype is in the power of smart and self-configuring devices which are well linked togetherThe IoTby archetypeglobal grid is ininfrastructures. the power of smartIoT ca andn be self-configuring typically defined devices as a which real areobject, well largely linked dispersed,together by with global low grid storage infrastructures. capabilities and IoT pr canocessing be typically capacities, defined while as aaiming real object,at enhancing largely reliability,dispersed, withperformance low storage and capabilities security of and the processing smart citi capacities,es as well whileas their aiming infrastructure at enhancing [3]. reliability, On this performancebasis, in the present and security paper, ofa survey the smart of the cities IoT-ba as wellsed assmart their cities infrastructure information [3 from]. On related this basis, reports in the is presentconducted. 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 Figure1 1.. TheThe perceptionperception layerlayer includesincludes aa groupgroup ofof Internet-enabledInternet-enabled devices that are able to perceive, detect objects, gather information, and exchange information with other devicesdevices through through the the Internet Internet communication communication networks. networks. Radio Radio Frequency Frequency Identification Identi Devicesfication (RFID),Devices cameras,(RFID), sensors,cameras, Global sensors, Positioning Global SystemsPositioning (GPS) Systems are some (GPS) examples are some of perception examples layer of perceptiondevices. Forwarding layer devices. data Forwarding from the perception data from layer the toperception the application layer to layer the underapplication the constraints layer under of thedevices’ constraints capabilities, of devices’ network capabilities, limitation network and the applications’limitation and constraints the applications’ is the task constraints of the network is the tasklayer. of IoT the systems network use layer. a combination IoT systems of use short-range a combination networks of short-range communication networks technologies communication such as technologiesBluetooth and such ZigBee as Bluetooth which are and used ZigBee to carry which the ar informatione used to carry from the perception information devices from toperception a nearby devicesgateway to based a nearby on the gateway capabilities based of the on communicatingthe capabilities parties of the [ 4communicating]. Internet technologies parties such[4]. Internet as WiFi, technologies2G, 3G, 4G, and such Power as WiFi, Line 2G, Communication 3G, 4G, and Powe (PLC)r Line carry Communication the information over(PLC) long carry distances the information based on overthe application. long distances Since based applications on the application. aim to create Since smart applications homes, smart aim cities, to create power smart system homes, monitoring, smart cities,demand-side power energysystem management,monitoring, demand-side coordination en ofergy distributed management, power coordination storage, and of integration distributed of powerrenewable storage, energy and generators, integration the lastof layerrenewable which energy is the application generators, layer, the is last where layer the informationwhich is the is applicationreceived and layer, processed. is where Accordingly, the information we are ableis rece toived design and better processed. power distributionAccordingly, and we management are able to designstrategies better [5]. power distribution and management strategies [5]. Figure 1. IoT layers. 1.2. Motivations The smart smart city city is is becoming becoming smarter smarter than than in the in thepast past as a asresult a result of the of current the current expansion expansion of digital of technologies.digital technologies. Smart Smartcities citiesconsist consist of various of various kinds kinds of ofelectronic electronic equipment equipment applied applied by by some applications, such such as as cameras cameras in in a amonitoring monitoring syst system,em, sensors sensors in ina transportation a transportation system, system, and and so on. so Furthermore,on. Furthermore, utilization utilization of individual of individual mobile mobile equipment equipment can can be be spread. spread. Hence, Hence, with with taking taking the heterogeneous environment into account, various term terms,s, like characteristic of objects, participants, motivations and security policies would be studied [[6].6]. Reference Reference [7] [7] presented presented some some of the key features ofof potential potential smart smart cities cities in 2020.in 2020. Smart Smart citizens, citizens, smart smart energy, energy, smart buildings,smart buildings, smart mobility, smart mobility, smart technology, smart healthcare, smart infrastructure, smart governance and education Energies 2017, 10, 421 3 of 23 Energies 2017, 10, 421 3 of 23 smartand finally technology, smart smartsecurity healthcare, are the aspects smart infrastructure,of smart cities. smart The features governance of a and smart education city are and shown finally in smartFigure security 2. are the aspects of smart cities. The features of a smart city are shown in Figure2. Figure 2. The key aspects of smart cities. In an IoT environment, devices can be aggregated according to their geographical position and 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 also assessed by applying analyzing systems. Sensor services for gathering specific data are utilized with some ongoing projects regarding the monitoring