## 3 Results and Discussion
### Applications Key IoT Technologies for Energy-Efficient 6G in Smart Cities  
The implications of using 6G in key IoT technologies such as blockchain, VLC, and others rely on their main performance metrics. [PERSON] et al. [14] proclaimed that the implementation of 6G wireless communication depends on specific performance metrics. These performance metrics include mobility, energy and spectrum efficiency, throughput, latency, and reliability. The devices and structures tried to meet such standards to implement 6G through IoT devices in smart cities. [PERSON] et al. [31] proposed that the application of 6G and IoT devices ensures unlimited networking possibilities for people in smart cities. According to [PERSON] et al. [32], the number of smart IoT devices could reach up to fifty, making people lives easier. The application of IoT devices for 6G in smart cities provides a 100 Gbps data rate, <0.1 ms latency rate, up to 1000 km/h mobility rate,100 bps/Hz spectral efficiency, and 1000 GHz frequency. Moreover, [PERSON] [33] discussed the implication of lightweight security modules such as 6G and IoT devices, which can improve the working of smart cities. As per the authors, Smart City Networking Model using Lightweight Security Module (SCNM-LSM) improves smart city living. The application of 6G in IoT devices facilitates e-health, intelligent transportation system, managing energy resources, and networking modeling [34; 35; 36]. This depicts that the implication of IoT devices for 6G in smart cities enhances the connectivity rate, which enables people to enjoy unlimited networking possibilities during a post-pandemic situation. The application of IoT devices in 6G in smart cities can produce incredible benefits. [PERSON] et al. [36] articulated that 6G wireless communication with the help of IoT devices helps to create super-smart cities. The rationale is that 6G connectivity enhances the communication and transmission rate, providing premium-quality features to smart city residents. However, [PERSON] et al. [31] claimed that the implementation of 6G through IoT devices in a smart city can give rise to data security risks, psychological abuse, cyber risks, and others. In contrast, [PERSON] et al. [37] articulated that the application of AI in 6G can help to control the system's security risks [38]. The collaboration of AI and 6G transform the healthcare system by providing precise medical solutions and health-monitoring. This allows for healthcare workers, patients, and hospital management to keep the details secure, enhancing their benefits to the community. In addition, [PERSON] and [PERSON] [39] discussed the intelligent transport system (ITS) that is implemented in smart cities, facilitating the use of smart logistics. The authors discussed the United Nations Population Funds' predictions that 60% of the world population in the next ten years will move to smart cities that imply the use of IoT devices with 6G [40; 41]. Hence, the pattern of 6G being implemented through IoT devices has started in smart cities, which are the future of the global population. It has demonstrated that 6G application through IoT devices can help people to receive unlimited benefits. This can be seen in [PERSON] et al. [10]'s example, presenting a '15 Minute City' through 6G and IoT devices. According to [PERSON] et al. [10], the '15 Minute City' is the new urban planning model presented by Franco-Colombian scientists, using intelligent devices with the fastest connectivity rate to enhance people's livelihood. As per the authors, the '15 Minute City' is the true example of applying 6G and IoT devices to build a super-smart city. In addition, [PERSON] et al. [11] highlighted the amalgamation of IoT, blockchain, and 6G in the smart city. As per the authors, the application of 6G wireless communication in the smart city can address latency and reliability issues. Blockchain technology can handle security and privacy risks, and IoT facilities play a significant role in security, privacy, latency, and reliability [42].