## 3 Overview of HO Management in 5G UDSC Network
### Mobility Management in 5G UDSC Network  
The purpose of mobility management in cellular networks is to find, identify and track users according to their locations to deliver them cellular services. It is primary function of the GSM and UMTS network to offer high quality of cellular service to their users irrespective of their locations. It means if the users are using their devices close to mobile terminal or present in hilly areas, all of them must be covered by GSM cellular networks. Henceforth, communication constancy, reliability, steadfast performance are all the ultimate goals of mobility management in the cellular networks [53; 54]. Location management and HO are the two types of mobility management. In location management, UE informs the mobile station network that it is now associated to its specific location. After receiving the notification, location updating, and paging process starts. Network operates signaling process and paging progress through these location signals [55]. In B5G air based network, UAV path needs to change nearby to the terrestrial to reduce the communication delay as higher altitude of UAVs introduces loss of path in connectivity accordingly, so drone altitude depends upon use cases of applications and higher RSRP value and higher interference from neighbor base stations resultant in higher HO ratio [56]. Both air-to-ground and ground cellular network channel face high cochannel interference also on high frequencies UAV's creates Doppler shift that causes inter carrier interference (ICI). Another issue is limited rechargeable battery power that limit the duration of UAV flight operation time. By contrast, UAV-BSs connecting with the macro base stations (MBSs) or the core network need high capacity wireless back haul links. Practically, the limited back hauls will become the bottleneck and affect the QoS of mobile users [57; 58]. Back haul network is categorized by heterogeneous links for BS-wired links and UAV-wireless links and core network require high capacity wireless backhaul associations so the inadequate back hauls create the blockage and disturb the QoS. Satellite move on velocities differs for many services whether the task is fast data acquisition or real time information exchange [59; 60].  
Mobility in 5G beyond networks is mainstream for researcher due to the advance technologies range and directions are limited. In HO, the channel connection needs to be switch to other channel using information regarding reference signal strength and other network parameters. To optimize this process, it is very difficult to handle these parameters as they have equally influence on network. Some of them are interference management, energy consumption, load balancing, coverage, and capacity. These parameters also have the effect on ping-pong rate, call dropping/blocking probability, and early or late HOs [61]. Research have been proposed for the efficient HO mechanism using many theories and techniques/tools especially artificial learning to optimize the HO process [62]. 3 GPP model explain the five basic UAV case studies based on velocities, mobility pattern, altitude, and movement. They also mentioned the maximum speed of 160 km/h and altitude 300 m, respectively. Depends upon application requirement UAV can exchange altitude, mobility, flight mode, and HO information with operator but under constraint of reliability, latency, and throughput [63]. The other problem with UAV is line of sight that create different interference conditions as terrestrial user would not face this problem. For management and operations of UAV system, identification, robust and efficient connectivity of UAV is a key interest. HO management and how we can acquire 5G HO through RL will be discussed in the remaining portion of this paper [64; 65].