## 2 Related Work: A Review of Relevant Survey Papers
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline \hline
**Ref.** & **Description** & **Considered Platform** \\ \hline
[28] & This comprehensive review examined HO techniques over DC and innovative solutions such as ML-based approaches in future UD-HetNet to address the mobility management issues in LTE-A and advanced WCS. & LTE-A/5G UD-HetNet \\ \hline
[29] & The mobility management general concept, possible research directions, and major challenges such as HO issues, signaling overhead, power consumption, security, and latency faced by upcoming new WCS were discussed in detail. Moreover, some effective solutions were demonstrated to meet/encounter future network mobility management requirements. & 5G HetNet \\ \hline
[30] & Based on 5G architecture and service types, a brief survey was conducted in this paper to explore the concept of VHO in the future wireless system. In addition, it also analyzed how SDN/NFV and MEC technologies can be utilized to manage mobility and HO issues in NG-WCS. & 5G HetNet \\ \hline
[31] & It examined previous research on mobility and HO management, characterizations, and fundamental causes of mobility issues in UD-HetNet. It provides the fundamental causes of mobility challenges in future networks and highlights potential solutions and opportunities for upcoming development. An overview of the challenges and practical considerations to be addressed in NG networks is also provided. & 5G UD-HetNet \\ \hline
[32] & This paper discussed the key enabler technologies required to improve the QoS and meet the NG-WCS requirements. NG-WCS background, benefits, and different network layouts were studied extensively. Moreover, existing ML-based techniques to overcome the challenges related to mobility and HO in NG-WCS are also reviewed in detail. & 5G UD-HetNet \\ \hline
[33] & A comprehensive review and analysis of various ML-based techniques for HO management in future dense network environments are carried out in this article. Several open challenges with possible solutions based on ML are also suggested to improve the future network performance & 5G UD-HetNet \\ \hline
[34] & In this paper, the HO management challenges and HO decision algorithms for LTE-A are studied in detail. The pros and cons of each HO decision scheme based on input system parameters and KPIs are also reviewed. & LTE-A/4G/HetNet \\ \hline
[35] & This article extensively reviewed various HO self-optimization schemes, particularly MRO and LBO, for evaluating the seamless HO in NG-WCS. This article also highlighted the pros and cons of the previously proposed schemes, challenges faced by HO self-optimization schemes, and possible solutions to overcome the mobility and HO issues in future HetNet environment. & 5G-NR \\ \hline
[36] & The basic HO execution procedure and HO management overview in LTE-A and NR are discussed. Moreover, the general concept of radio access mobility (RAM), such as idle and connected mode mobility and possible challenges related to RAM in cellular networks, are presented. & 5G UD-HetNet \\ \hline
[37] & The authors address the 5G-enabling key technologies, challenges, and opportunities related to ML-based HO management schemes and possible solutions to address these challenges. & 5G UD-HetNet \\ \hline
[37] & In this study, we explain the general concept of 4G and 5G. The architecture, services, and technologies of the 5G system to improve mobility and HO issues in future WCS are also discussed. Moreover, various schemes such as SDN, ML, FLC, and dynamic HO control parameters (D-HCPs) are also examined to improve the HO performance in 5G HetNet. Finally, important future challenges that degrade the HO and mobility performance in 5G systems and possible recommendations for solutions are also discussed in detail. & 5G UD-HetNet \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of related surveys on HO and mobility management with our survey paper.