## 2 Challenges and Routing in 6G Networks
### Routing in 6G Networks
#### 2.2.2 Review of 6G Routing  
In academia, 6G is an especially hot topic that aims to supply users with rich quality of service (QoS) using ubiquitous mobile broadband (uMBB), Ultra-Reliable Low-Latency BroadBand Communication (ULBC), and massive Ultra-Reliable Low-Latency Communication (mULC) [82; 83]. The optimization of the network is critical for 6G to achieve its intended end-to-end QoS at rapid speeds, ultra-low response times, and enhanced mobility. Guaranteeing end-to-end quality, dependability, and service depends mainly on routing algorithms and network congestion management. High efficient routing is an important issue for the 6G networks. The literature on routing protocols in 6G networks is given in Table 2. \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline
**Refs.** & **Major Features and Characteristics** \\ \hline
2018; ref. [67] & They examined each generation of wireless technologies according to the advantages and disadvantages they have. \\ \hline
2019; ref. [68] & They conducted a study on the combination of quantum computing and machine learning with the latest technologies in the field of telecommunications. \\ \hline
2019; ref. [19] & It describes many of the technical difficulties and occasions for 6G in cordless networks above terahertz (THz). \\ \hline
2019; ref. [20] & It examines 6G in terms of time, frequency, and space resource usage, especially security issues. \\ \hline
2019; ref. [69] & The potential integration of SDN and NFV technology with 6G is presented. \\ \hline
2019, 2020, 2021; refs. [70; 71; 72; 73; 74; 75; 76; 77; 78] & The authors aimed to shed light on the far-sightedness, vision, requirements, key approaches, technologies, and architecture of 6G. \\ \hline
2019; ref. [45] & It focuses on technologies that will not be in 5G but will be in 6G. The study focuses on sub-THz, visible light communication (VLC), prevalent AI in network side technologies that will be in the 6G architecture. \\ \hline
2019; ref. [79] & They present a detailed survey of the 6G approach, trying to unify all tellurian and non-tellurian networks; they also focus on VLC and THz communication techniques, which are also prominent in 6G. \\ \hline
2019, ref. [80] & The aim of the 6G Flagship program is to gain 5G acceptance and elaborate on 6G. It focuses on developing future wireless technologies. \\ \hline
2019; ref. [81] & This ensemble aims to research the proficiencies of networks for 2030 and beyond. \\ \hline \end{tabular}
\end{table} 
Table 1: Summary of existing survey articles on 6G networks. - They proposed a novel routing strategy aimed at minimizing overall latency in a 6G wide area network
- The average end-to-end delay was found to be less than 1 ms
- The proposed proactive model performed better than the reactive model
- The study can be enriched with different ML models and future network metrics
* They propose P-HEUR, a new model that optimizes energy-saving user assignment, routing of backhaul traffic, and base station/backhaul link transitions
- The ONE approach addresses instantaneous user connections, the routing of traffic, and VNF allocation to enhance energy efficiency and user acceptance in mobile networks
* The ONE approach addresses instantaneous user connections, the routing of traffic, and VNF allocation to enhance energy efficiency and user acceptance in mobile networks  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8  
In 2021, [PERSON] et al. worked on streamlined traffic handling on 6G networks to ensure end-to-end QoS and QoE. This study discussed the fact that the management processes in existing networks will not work efficiently for 6G networks through network access and routing to traffic management and streaming adaptation because of the intricate and ever-changing scenarios of 6G. They proposed that the use of machine learning, deep learning, and deep reinforcement learning algorithms in network access can pave the way for network routing, congestion control, and network flow control, optimizing a reduction in issues within the network.