# A Survey of Handover Management in Mobile HetNets: Current Challenges and Future Directions
## 5 Open Issues and Future Directions  
A lot of work has already been done to address the HO and mobility issues in future mobile networks, but significant work still needs to be done in this area. Handover management is a critical aspect of wireless networks, particularly in 5G dense networks where there is a high density of cells and a large number of devices connecting to the network with dynamic requirements like high-speed mobility, low latency, high reliability and high data rates, etc. Similarly, a lot of emerging technologies such as; wireless augmented reality, gaming, high-definition video streaming, voice and video calling, ITS, V2V, V2X, IoT, HSR, UAV, automated driving vehicles, etc. introduced new challenges in these networks. Research in this area is already focusing on various techniques such as machine learning, deep learning, network slicing, and network virtualization to improve handover management and to make it more efficient and flexible. There are still many open areas to be addressed, such as the need for better prediction algorithms, the need for new protocols to reduce HOL, HOPP, RLF, the number of handovers, and the need for solutions that can scale to handle the large number of handovers that will be required in 5G small cell dense networks. In this section, we will briefly highlight a few of the key points related to the future research directions. 1. Software Defined Networking (SDN): The implementation of SDN in 5G HetNets aims to address the dynamic and complex nature of various network architectures by centralizing control and management. One of the key focus areas in this context is optimizing the handover process, which is transferring a connection from one network to another, to improve the overall performance and user experience in 5G HetNets. Here are some of the research challenges in the context of SDN-based handover optimization in 5G HetNets: * Developing accurate and efficient handover decision algorithms * Minimizing handover interruption time * Managing network resources during handover * Managing the load balance SDN can play a key role in addressing the above-mentioned research challenges by providing centralized control and management, which can be used to optimize the handover process and improve the overall performance and reliability of 5G HetNets [173; 165; 174; 175; 176; 177]. 2. Machine Learning: ML-based handovers in 4G/5G HetNets can improve wireless networks' overall performance and efficiency by making more accurate and efficient handover decisions. However, several key research challenges need to be addressed to fully realize the potential of machine learning in this area. These challenges include dataset availability and quality issues, privacy and security, online and offline learning, centralized and distributed learning, frequent handovers, signaling overhead, energy efficiency, and load balancing. These challenges need to be addressed in order to develop accurate and efficient machine learning algorithms for handovers in HetNets and to ensure that these algorithms can handle the complexity and uncertainty of real-world wireless networks [178; 179; 180; 181; 182]. 3. Deep Learning: DL has been proposed as a solution for handover management in 4G/5G HetNets due to its ability to learn and make predictions from large amounts of data. This can be useful in HetNet environments, where the number of possible network states and configurations is high. Deep learning can be used to predict the likelihood of a handover event, optimize the allocation of resources, improve QoS and QoE, enhance security and privacy, reduce HOL and improve the real-time performance, and make the decision-making process of the handover more transparent and interpretable. Overall, the use of deep learning in handover management in HetNets can enable more intelligent and efficient handover decisions, which can improve the system's performance and enhance the user experience. 4. Dual Connectivity (DC): DC is a technique used in HetNets to improve handover performance.