Ensuring a seamless connection during the mobility of various User Equipment (UE) will be one of the major challenges facing the practical implementation of the Fifth Generation (5G) networks and beyond. Several key determinants will significantly contribute to numerous mobility challenges. One of the most important determinants is the use of millimeter waves (mm-waves) as it is characterized by high path loss. The inclusion of various types of small coverage Base Stations (BSs), such as Picocell, Femtocell and drone-based BSs is another challenge. Other issues include the use of Dual Connectivity (DC), Carrier Aggregation (CA), the massive growth of mobiles connections, network diversity, the emergence of connected drones (as BS or UE), ultra-dense network, inefficient optimization processes, central optimization operation, partial optimization, complex relation in optimization operations, and the use of inefficient handover decision algorithms. The relationship between these processes and diverse wireless technologies can cause growing concerns in relation to handover associated with mobility. The risk becomes critical with high mobility speed scenarios. Therefore, mobility issues and their determinants must be efficiently addressed. This paper aims to provide an overview of mobility management in 5G networks. The work examines key factors that will significantly contribute to the increase of mobility issues. Furthermore, the innovative, advanced, efficient, and smart handover techniques that have been introduced in 5G networks are discussed. The study also highlights the main challenges facing UEs' mobility as well as future research directions on mobility management in 5G networks and beyond.

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The Heterogeneous Network (HetNet) has emerged as one of the most promising developments toward achieving the target of the Long Term Evolution-Advanced (LTE-A) systems. However, Co-Channel Interference (CCI) is one of the critical challenges of HetNet, that degrades the overall performance of a system. Therefore, an appropriate Radio Resource Management (RRM) mechanism is required to deploy and expand the HetNets properly. In this paper, a new RRM strategy called Fractional Frequency Reuse with Three Sectors and Three Layers (FFR-3SL) technique is proposed. The FFR-3SL efficiently utilizes the radio resources and alleviates the effects of CCI in LTE-A HetNets and thereby improving the system performance. In order to implement the proposed strategy, the entire macrocell coverage area is segmented into three sectors and three layers, while the total bandwidth is divided into seven subbands. Subsequently, the subbands are accurately distributed among femtocells and macrocells by employing the proposed algorithm. As a result, the co-tier and cross-tier interferences are managed on a prior basis. The Monte Carlo simulation is performed to evaluate and compare the performance of the proposed method with the existing methods. The simulation results show that the proposed method achieves higher throughput and better capacity in LTE-A HetNet system. Furthermore, the efficiency of the system is improved with regard to user satisfaction in terms of signal to interference and noise ratio (SINR) values.

Ensuring reliable and stable communication during the movements of mobile users is one of the key issues in mobile networks. In the recent years, several studies have been conducted to address the issues related to Handover (HO) self-optimization in Heterogeneous Networks (HetNets) for Fourth Generation (4G) and Fifth Generation (5G) mobile networks. Various solutions have been developed to determine or estimating the optimum and ideal settings of Handover Control Parameters (HCPs), such as Time-To-Trigger (TTT) and Handover Margin (HOM). However, the complexity, high requirements, and the upcoming structure of ultra-dense HetNets require more advanced HO self-optimization techniques for future implementation. This paper studies HO self-optimization techniques that may implemented in the next-generation mobile HetNets by reviewing state-of-the-art algorithms. The solutions discussed in this survey are more focus on Mobility Robustness Optimization (MRO), which is a significant self-optimization function in 4G and 5G mobile networks. The applied solutions will preserve the continuous connection between the User Equipment (UE) and eNBs during UE mobility, thereby enhancing connection quality. The various algorithms and techniques applied to HO have revealed different outcomes. This paper discusses the pros and cons of these techniques, and further examines HO self-optimization challenges and solutions. New future directions for the implementation of HO self-optimization are also identified. This survey will contribute to the understanding of the issues related to mobility management, particularly in relation to the self-optimization of HO control parameters in future mobile HetNets.