## 3 Overview of HO Management in 5G UDSC Network
### HO Management in 5G UDSC Network  
To manage radio resources, HO play an important role in 5G. Transmission in mobile systems in 5G require greater bandwidth and greater communication service rate for distinct nodes or terminals. So, HO assure to provide good quality of service and continuous communications to maintain overall network performance in 5G [66]. Integrated UAVs communications into intelligent mobility and HO management/prediction with 5G and beyond using AI techniques will help to tackle frequent HOs with reliability and coverage. Different technologies embed in 5G; number of problems occur in HO process [67]. In HO, one need to implement well informed terminal to handle the higher data rates, basestations, and increased number of mobile devices. UAVs and user equipment's are same by characteristics, but the HO characteristics are different and radio environment of both cases as their mobility models are different [68]. Performance depends upon the HO rates such as failed/successful HO. RACH, timer's expiration, after a certain maximum number of re transmissions results in radio link failures. As the protocols for operations are different for UE and UAV so it is necessarily to decide first by elevation angle of the reference signal, velocity of user device, vertical location, and user device path loss/delay spread measurement. In the case of UAVs, they are not always connected to nearest BS as they are hunting for strongest RSRP so signal may come far from the drone also antenna beam concentrates to cover the ground coverage and drone usually fly on side lobes of antenna. UAVs fly in angular regions of 120\({}^{\circ}\), 240\({}^{\circ}\), and 270\({}^{\circ}\) and may connect to other BSs located in the region because they gain the inadequate signal strength. In this respect the UAV location and flight information help to make efficient HO i.e., enrich the existing signal report mechanisms, BS to help for HO using improved control of the RSRP measurement load [69]. The altitude of UAV matters a lot in terms of HOs as drone making height from 10-150 m then HO/minute also increase from 1-5 m. Integration of UAVs with beyond 5G wireless networks create the space for enhance cell selection process in 3D mobility patterns [70]. Following the guidelines in [71], Table 2 illustrate the classification of HO decision schemes, e.g., RSS based, QoS based, function based, intelligence based, and context based. Advantages of small cell can be enlisting such as spectrum efficiency, high data rate, energy/money saving, less congestion, easy HO while there are also some disadvantages i.e., implementation cost and operational reliability, frequent authentication, and active or passive (on/off) state update. HO means that one can change its base terminal to its nearby terminal when moving from one point to another without interrupting the communication [72]. Innate challenges for HO in beyond 5G are following no services, improved routing, minimum latency, and security and these challenges become more harder in the scenario of multi-RATs, zero latency, network densification and high mobility. Beside these issues the load balancing for BS at the time of HO is also a main issue specially in the case of terrestrial network where the UEs move from houses to offices at morning and evening time respective of areas. HO is in different types according to connectivity such as intra macrocell, inter macrocell, and multi-Rat's handoff. In dense HetNets HO mechanism is still an open issue, trade off between handoffs rates and interference level in the network and establish different types of interference to other UEs. Basically, there is network switching process occur in HO [73]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**RSS Based** & **QoS Based** & **Function Based** & **Intelligence** & **Context Based** \\  
There are 3 basic steps in HO which are as follows: (1) discovery: in this step, network has to find such network which provide good quality of service to user.