# A Survey of Handover Management in Mobile HetNets: Current Challenges and Future Directions
## 4 Handover Decision Techniques
### UE Velocity-Aware HO Decision Approaches
The partial optimization of HCP parameters results in inefficient HO triggering, lowering overall system efficiency. Similarly, Manual optimization, non-optimal analysis of HCPs, and central optimizations are the obstacles to optimal HO triggering. This necessitates the use of distributed optimization approaches because each UE needs specific HCP values. In this research [91], the authors developed a distributed optimization strategy for 5G networks based on weight functions. According to UE requirements, the system automatically predicts the weight values for each unique user. The weight values for SINR, UE load, and UE speed are first evaluated by the weighting mechanism. Following the initial evaluation of input parameters, the outputs are transmitted to the second weight function to produce the final output weight value, which will be utilized as an indicator for the optimization of HCP for a particular user. The proposed weight algorithm's results were compared against HOPP, HOP, RSRP, and RLF. The benefit of this proposed strategy is that it does not interfere with other participating UE's HCP values, resulting in an improvement in RSRP and a reduction in HOPP and RLF overall. Similarly, in [44], they used a fuzzy logic approach based on UE's velocity along with RSRP and RSRQ as input parameters. The optimisation approach aims to introduce a robust HCP combination for 5G and next-generation networks. They evaluated the algorithm with different mobility speed scenarios in 5G networks for HOP, HOPP, HOF, HOL, and HIT as compared to HOPP, HOP and RLF of their previous work [85]. HCP values for some grouped velocities cannot be fixed because these can change rapidly with the change in velocity and other parameters. To establish these groups for fuzzy systems, an impact of change in velocity must be measured on HCP values. In mobile communications, HetNets and network densification are perceived as an essential approach for handling the ever-increasing capacity and data rate demand, its impact on the handover (HO) rate is often ignored. The benefits offered by HetNets directly affects by the number of HO's and delays caused by moving users. The authors in [151] developed a velocity-aware HO skipping algorithm via stochastic geometry method, for cellular HetNets to overcome the HO effects and to improve the data rates. The HO skipping or bypassing scheme skips the cell that have highest SINR value along the user trajectory to prolong the service or connection duration with the serving cell. This process resultantly reduces the number of HOs and its related effects on the performance. Specifically, the simulation results indicate that the velocity-aware HO skipping methods can generate up to 77% higher data rate gains than the typical HO strategy that always maintains the optimal RSRP based relationship. In [152], a velocity-aware HO triggering method for cellular HetNets was developed that relied on the coordination of MIH (Media-Independent Handover)and PMIPv6 (Proxy Mobile IPV6) to facilitate user mobility while reducing packet loss and HOL. They segmented the procedure into several parts, such as velocity tracking to obtain stabilized values, updating the velocity values based on GPS tracking to obtain UE lifespan for better decision making, and finally performing triggering choice. They effectively improved packet loss and HOL issues but ignored HOP and HOPP. In article [76], the authors intended to show the effect of different HCP values on the performance of 5G network by analyzing fixed HCP settings. They used various scenarios to explain the necessity for applying more advanced approaches in 5G networks. They have used HOM's and TTT's predefined values with the predefined velocity of UE to check the behavior of UE based on HOP, HOPP, and RLF. According to the simulation results, lower HCP values can minimize the number of HOF while increasing the HOPP. These results can further highlight that the medium HCP values may be the best solution when using some fixed HCP environment for specific velocities.