## 2 Challenges and Routing in 6G Networks
### Routing in 6G Networks
#### 2.2.1 State of the Art of 6G  
The focus of the earliest studies on 6G has been around the question of whether 6G vision is really needed. One of the studies that focuses on this point is the study of [PERSON] and [PERSON], published in September 2018. They examined each generation of wireless technologies according to the advantages and disadvantages they have. They also drew conclusions about the 6G vision and what the user wants [67]. [PERSON] et al. [68] conducted a study on the combination of quantum computing and machine learning with the latest technologies in the field of telecommunications. In [19], [PERSON] et al. describe many of the technical difficulties and instances of 6G for cordless networks above terahertz (THz). The authors of [20] reviewed 6G in terms of time, frequency, and space resource utilization, especially its problems such as security. In [69], two key 5G technologies are SDN and NFV, which are projected to move to a new level with 6G. In [70; 71; 72; 73; 74; 75; 76; 77; 78], the authors aimed to shed light on the far-sightedness, necessities, key approaches, and architecture of 6G. In [45], [PERSON] et al. started with reference to [PERSON]'s prophecy in 1926; it was emphasized that this prophecy can be realized with the studies that will take place towards 2030 and that the end user will access a network surrounded by a \"huge artificial brain\". It has been stated that 6G will take on a key task at this point and that 5G has great potential; it has transformed many sectors since its launch in 2019, created new sectors, and has even influenced society and revolutions. Is there any need to talk about 6G despite the breakthroughs that 5G has made compared to existing technologies? In the study, the focus is on technologies that will not appear in 5G but will be in 6G. It focuses on sub-THz, visible light communication (VLC), prevalent AI on the network side, three-dimensional (3D) inclusion consulting of tellurian networks, airy platforms, and satellite configuration technologies, which will be in the 6G architecture. The terrestrial and non-terrestrial network architecture of 6G is shown in Figure 4. [PERSON] et al. [79] present a detailed survey approach, trying to unify all tellurian and non-tellurian networks, with a focus also on VLC and THz communication techniques, which are also prominent in 6G. The 6G Flagship schedule was started by the Finnish University of Oulu in May 2018. The aim of this program is 5G acceptance and elaborating on 6G. As the most comprehensive 6G research schedule in the world, it focuses on developing future wireless technologies. To date, the program has produced more than 1500 peer-reviewed papers and 13 6G white papers. In March 2019, 6G Flagship initiated the world's very earliest series of 6G events, the 6G Wireless Summit [80]. The Next Generation Mobile Networks (NGMN) Alliance is working intensively on 6G activities to respond to the needs of the ecosystem. In July 2018, the International Telecommunication Union created the Network 2030 center ensemble. This ensemble aims to research the proficiencies of networks for 2030 and beyond [81]. The European Commission has adopted the freshly launched Smart Networks and Services Joint Undertaking (SNS JU) toward 6G, which will be supported by a public fund of EUR 240 million in the first work program of 2021-2022. This initiative, which seeks to facilitate European players in their construction of research and development (R&D) capacities for 6G systems, will be supported by an amount of EUR 900 million to be covered by the private sector in the next seven years. At the Mobile World Congress held in Barcelona on 1 March 2022, speakers from the industry emphasized 6G technologies as the next step in transitioning from gigabit capacities to terabit capacities in performance and achieving sub-millisecond response times. It was stated that such technologies will offer strategic opportunities for the development of new markets.