## 3 Proposed System Architecture
### Proposed System and Algorithm
Overall, our method demonstrated consistent performance across different UE speeds, effectively handling the rising number of HOs associated with higher speeds. This underscores the robustness and flexibility of our approach, crucial for ensuring continuous connectivity and optimal UE experience in dynamic network environments. ### Handover Failure (HOF)

HOF in HetNets can be caused by several factors. These include interference, load imbalances between BSs, coverage issues leading to sudden drops in received power levels, and inadequate mobility management techniques. HOF typically occurs when the UE is unable to establish a connection with the target cell or experiences a connection failure due to any of the above-mentioned factors. Figure 10a,b depict the average HOF probability for the overall UEs for different UE speeds and the overall system, respectively. The results from all algorithms show a correlation between the probability behavior of HOF and HOR. The results in Figure 10a,b reveal that VAFL achieves the lowest HOF probability. As illustrated in Figure 10a, there is a notable increase in the HOF for the FLD [25] method starting at the UE speed of 80 km/h. This sudden rise is attributed to the fact that the maximum UE speed considered in the referenced work is 72 km/h, and the HCPs attributed are not effective for UE speeds exceeding this maximum. When evaluating Figure 10b, VAFL achieves an HOF rate of 0.00017143. In contrast, the other methods have HOF rates of 0.0025778, 0.0047048, and 0.0023206 for A3, FLD [25], and AWF [15], respectively. Our method surpasses A3, FLD [25], and AWF [15] by approximately 93.34%, 96.35%, and 92.61%, respectively, demonstrating its superior performance in reducing occurrences of HOF. The superior performance is attributed to the carefully optimized settings of the

Figure 9: Average HOR (**a**) overall UEs versus UE speeds, (**b**) overall system, and (**c**) simulation time. HCPs and the development of the algorithm that thoughtfully integrates considerations of signal level and cell load into the HO decision-making process. ### Radio Link Failure (RLF)

RLF is an important metric used to assess network performance. It occurs when an HO is initiated to a target BS, but the downlink SINR of that BS drops below a predetermined threshold within a specified period. HCPs can be configured manually or estimated automatically. However, setting HCPs to their maximum values can cause RLF. This is especially true for UEs located at cell edges or at high mobility speeds, as this can lead to late HO. A high RLF rate can result in network resource wastage and a decrease in overall QoS. Therefore, it is crucial to configure optimal HCPs to reduce the RLF rate and prevent network resource wastage. Figure 11 depicts the average RLF probability for the proposed method and the comparison methods under consideration. Figure 11 displays the average RLF probability for all UEs across various UE speed scenarios, while Figure 11 showcases the average RLF probability overall the system for the considered methods. Figure 11: Average RLF probability: (**a**) overall UEs versus UE speeds and (**b**) overall system. Figure 10: Average HOF probability: (**a**) overall UEs versus UE speeds and (**b**) overall system. Based on the illustrations, it is evident that the proposed method exhibits better performance at higher UE speeds. In terms of overall system performance, our method has a lower RLF rate than A3 and AWF [15], but it is slightly higher than FLD [25]. Our proposed algorithm achieves a reduction gain of approximately 8.14% and 41.71% compared to A3 and AWF [15], respectively. However, FLD [25] slightly outperforms our algorithm with a reduction gain of approximately 0.28%. However, it is not always ideal to have a lower RLF rate because lower HCPs settings result in lower RLF rates but higher HOPP probability. Therefore, the HCPs settings should be optimized to simultaneously ensure both lower RLF rate and HOPP probability.