## 3 Results and Discussion
### Applications Key IoT Technologies for Energy-Efficient 6G in Smart Cities
The authors provided different application examples, including ITS, smart grids, smart healthcare facilities and others. Hence, the application of 6G with IoT devices can help to formulate the '15 Minute City', ITS, smart grid, smart healthcare facilities and others. Smart cities address people's issues and could lead to a revolution in people's lives. The application of 6G can facilitate connected robotics and autonomous systems, such as drone-delivery UAV systems. The drone-delivery UAV system can ensure the timely delivery of packages. In addition, the implication of 6G through IoT devices in smart cities can provide the necessary facilities for people to use self-driving cars that protect them from traffic accidents and hustle [42]. Moreover, [PERSON] and [PERSON] [43] have provided an example of the \"Bangkok Metropolitan Region\" (BMR) that entails a region known as an \"Industrial Town\", built as a smart and sustainable city. The industrial town ensures the deployment of the 6G facility with IoT devices, which can provide the fastest connectivity. The authors applied the practical mobile planning and optimization framework. They found that the implication of 6G through IoT devices in industrial towns allows for people to fulfill their techno-economic opportunities by focusing on sustainable goals. Moreover, [PERSON] et al. [44] discussed the use of IoT devices to create a better environment. The sensors from devices produce digital measurements that improve people's quality of life in every smart city. The authors shared an example of the 'CitySense System', which characterizes the quantities of different environmental elements such as carbon dioxide, methane, temperature, air, humidity, and light. The measured quantities regarding environmental pollution concerns provide solutions to maintain the environment of smart cities and ensure a healthy lifestyle for residents. In the context of smart cities, 6G wireless communication is extremely useful when building a super-smart society. The superior and premium features of 6G, enhancing communication and interaction in terms of quality of life, are remarkable when applied in smart cities [45]. AI-based Machine-to-Machine (M2M) communication is used to monitor environmental activities, ensure automation in super-smart societies and improve quality of life. Another application of smart cities is using extended reality and augmented reality (AR), virtual reality (VR) and mixed reality (MR) to form features, using 3D objects for effective communication. AR allows for individuals to interact with the physical world based on the 3D landscape. On the other hand, MR forms a real and virtual atmosphere, where the interaction takes place in real time. This is why MR is also recognized as a hybrid application of the technology, which creates a 3D environment for users [46]. Figure 3 shows that [PERSON] et al. [9] have shown that fog computing is a real-time application, minimising time, computational cost, energy and storage issues when IoT is implemented in smart cities. Fog computing is a cloud-computing combination of routers, storage data and computers with end-users in close proximity. Moreover, connected robotics and autonomous systems are also an application of the 6G wireless communication network. The 6G could be useful in the deployment of connected robots and autonomous systems, such as drone-delivery UAV systems. The 6G communication system employing robotics and autonomous systems promotes self-driving cars and improves traffic and driving patterns using the sensors. A wide range of sensors is used in 6G wireless communication, including Light Detection and Ranging (LiDAR), radar GPS, sonar and odometry and inertial measurement units. When using 6G wireless communication such as UAV, there is a system communication between the ground-based controller and systems communications [42]. Furthermore, the AI application of the 6G wireless communication can be useful in providing smart healthcare systems with health monitoring and precision medical treatment.