## 7 Case Studies of Smart Cities  
In this section, we present selected case studies of smart cities on an international scale [24; 25; 26; 27]. It should be noted that these case studies (Barcelona, Stratford, Singapore) are handpicked based on recognition and the exemplary status of the renowned smart cities, providing a showcase but not a thorough analysis of the smart city testbeds. Barcelona has carried out significant reforms to become a smart city. To achieve the initial goals of a smart city, Barcelona is employing information and communication technologies (ICTs) to lead companies, institutions, specific sites, universities, technology centers, incubators, housing, dissemination, and entrepreneurs towards digital renovation and excellence [25]. With the aim of supporting smart city initiatives in terms of connectivity, Barcelona is employing 3G and 4G technologies, Wi-Fi mesh network, sensor network, public Wi-Fi network, new mobility plan, new heating and cooling systems, new energy networks, and underground tunnels. In addition, to better serve the city in terms of fast response, fiber optic cables are being deployed, covering 325 km of the city. Currently, Barcelona is moving towards a 5G-enabled smart city hub for Southern Europe [28; 29; 30]. Throughout the last decade, Stratford has emerged as a \"smart city\" by launching a smart metering program to address new energy saving regulations and stimulate economic growth. To achieve the launch goals, Motorola's 802.11n wide area network (MWAN) was deployed city wide. The Motorola AP 7181 802.11n was used as the external access point, and an AXS1800 GPON system was used to transmit the encrypted smart meter data. In the beginning, the meters were manually read once a month. To perform the audit, smart meters were installed in 200 houses based on a 40-access-point grid network. During the trial period, the meters were remotely accessed daily to determine how to reduce electricity consumption [26]. Recently, Stratford has moved on to 5G technology in order to boost the smart city services offered to its citizens [31]. Singapore has been consistently moving towards more sustainable urban development and a smarter city planning. One of the key motivations behind the city's transformation is the need for a smart transport system so that some of the city's constraints, such as land and lack of natural resources, would be overcome. Published research shows that in Singapore, roads already occupy 12% of the land area and the number of cars has increased to 9,700,000, marking a 62% lead over buses, taxis, and two-wheelers. To implement the intelligent transport system, sensors were deployed by leveraging the ultrahigh-speed 1 Gbps national broadband access and wireless broadband infrastructure [27]. Smart technologies not only help monitor traffic but also enable the capabilities to predict future congestion that can lead to optimal route management. In addition, to accommodate people with disabilities, RFID cards are used to extend the transit times at traffic light poles. Recently, Singapore has extended its smart city services and applications towards maritime IoT via the deployment of 5G technology [32].