# Key Technologies for 6G-Enabled Smart Sustainable City
###### Abstract  
With the advancement of information and communication technologies (ICTs), the way we live and communicate with each other is changing rapidly. As urban environments continue to evolve, the smart sustainable city (SSC) has sparked considerable attention. We are hoping for a new era in which numerous devices and machines including vehicles, sensors, and robots are all connected to communicate, respond, and operate in real time. The next-generation communication system, the sixth generation (6G), is expected to play a crucial role in improving the efficiency of urban operations and services. In this paper, we first provide the recent trends and key features of standardization in the SSC. To make the future SSC, we highlight key candidate technologies of 6G such as non-terrestrial networks, advanced mobile edge computing, vision-aided wireless communication, artificial intelligence (AI)-based wireless communication, and integrated sensing and communication. We put forth the main technical challenges given to each prime technology along with the potential benefits to pave the way for 6G-enabled SSC. We further address how the potential benefits of prime technologies enable various urban practice cases for 6G-enabled SSC.  
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Footnote †: journal: Electronics Electronics  
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Footnote †: journal: Electronics Electronics Electronics  
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Footnote †: journal: Electronics Electronics Electronics Electronics  
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Footnote †: journal: Electronics Electronics Electronics Electronics Electronics  
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Footnote †: journal: Electronicsfirst generation (1G) was introduced in the 1980s. Note that the fifth generation (5G) was commercialized in 2019 and 5G services are now active in more than 90 countries. It is worth noting that 5G is creating an ecosystem for business innovation that involves smart cities. With the advent of 5G technologies, both academia and industry are doing research activities for the sixth generation (6G) [6; 7]. 6G networks are considered one of the prime candidates to enable SSC to facilitate the emergence of new applications and services [8; 9]. In this paper, we introduce 6G key candidate technologies that could be key enablers to realize future SSC.  
The primary goal of this paper is to provide an up-to-date overview of various aspects related to the 6G-enabled SSC. These include standardization features, key enabling technologies, and potential benefits along with future research directions. Through this paper, we hope that it can be an opportunity to outline a way forward to realize a hyper-connected society and to target specific goals to achieve it by 6G prime technologies in the near future. The main contributions of this paper are summarized as follows:  
* We highlight key features of standardization for SSC from an ICT perspective. In this paper, we articulate the importance of ICT infrastructure and candidate ICT technologies for 6G-enabled SSC.
* We put forth the prime technologies that can boost the evolution of SSC. Upon this categorization, we account for the main technical challenges given to each prime technology along with the potential benefits to pave the way for 6G-enabled SSC.
* We shed light on urban practice cases for 6G-enabled SSC. We address how the potential benefits of prime technologies enable various scenarios and applications.  
The remainder of this paper is organized as follows. In Section 2, we present the definition of a smart city and then provide the smart city policies of various countries. In Section 3, we present smart city standards based on ICTs. In Section 4, we provide a brief explanation of the evolution of mobile communication systems and then investigate the key technologies for a 6G-enabled SSC. In Section 5, we provide our concluding remarks.