# The Challenges and Compatibility of Mobility Management Solutions for Future Networks
## 2 Design Principles and Requirements for Upcoming MM Techniques
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Requirement** & **Ongoing Scenario** & **The Scenario in 5G and Beyond** & **MM Requirements** \\ \hline
1 & Complexity is considered based on user requirements in a homogenous network [7] & The complexity is the sum of heterogeneous radio access technology (RAT) scenarios, the dense nature of the network, various QoS requirements of users, and backhaul scenario [10] & 1. Flexibility to accommodate heterogeneity 2. Tractable solution (low computational 006 Fmplexity) 3. Low power utilization for a dense network \\ \hline
2 & Up to 400 km/h mobility support & Mobility support up to 500 km/h [5] & Accommodating various demands of mobility profiles \\ \hline
3 & Services and data are entertained in a core network & Demanded data and services can be entertained at network edges by multi-access edge computing (MEC) [4] & Ensuring QoS service for applications during mobility for service replication [8] and migration \\ \hline
4 & 6 GHz frequency band & Sub 6 GHz, Terahertz communication [11; 12], millimeter wave (mmWave) [13] & The level of robustness has a prominent impact on MmWave and (visible light communication (VLC), hence challenging continuous connectivity \\ \hline
5 & Fine granularity of localization and tracking \(<\)50 m [14] & Fine granularity of localization and tracking \(<\)10 cm [14] & Capability to offer better granularity in a dense or urban environment \\ \hline
6 & MM protocols are standardized for 2G to 4G networks and devices & These are different from 2G to 4G & Support of backward Compatibility \\ \hline
7 & Radio tower-based (static) network & Relay stations and BS may be used on drones in 5G and future networks [15; 16] & Mobility provision for BS and UE \\ \hline
8 & Connectivity in the range of radio access network (RAN). & Connectivity between RANs & Provisions for efficient radio access technology (RAT) selection process as well as multi-RAT MM support \\ \hline
9 & The network is driven by a vendor [4] & The network has become softwarized [4] & Capability to use MEC, software-defined network (SDN), near-field communication (NFC), etc. \\ \hline
10 & The density of user equipment is nearly 100,000 users per km\({}^{2}\) & The density of user equipment is nearly 1,000,000 users per km\({}^{2}\) & Support of mobility for an increasing number of users \\ \hline
11 & Provision of services for mobile broadband applications & There is support for applications with different QoS requirements such as ultra-reliable low latency communications (URLLC), massive machine type communications (mMTC), and enhanced mobile broadband (eMBB) applications & Provision of mobility support according to the context \\ \hline
12 & The complexity of the network is handled and operated by a human being & Data traffic is booming, with more complex networks and devices [17; 18; 19] & Low energy consumption in such a complex network \\ \hline
13 & The traditional optimization for spectrum range & Complex optimization for new spectrum range [20; 21] & Low energy consumption by using a new spectrum range \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Functional requirements of MM mechanisms. also required to transform future networks [2]. This will also have adverse effects on the QoS parameters at the time of roaming, which will also be elaborated on in later sections. Likewise, we also face another concern (challenge) for the MM mechanisms, especially when the base station is moved, such as in drones [23] or a squad of vehicles moving together or joining and disjoining vehicles or extremely fast user movement (200 to 600 km/h), etc. Furthermore, the purpose of the latest MM techniques is to embed software (SDN) for controlling the mobility between the RATs [24]. Still, these embedded techniques have not been particularized in some other encountered aspects, such as the burden of the number of messages exchanged, time convolution, etc.