## 4 Framework and Principles for VHO Scheme
Based on the simulation results, it can be summarized that Ac-VHO exhibits lower signaling costs compared to the other three schemes in all four scenarios. The main reasons contributing to this outcome are as follows:

* The classification of different types of RTA in the Ac-VHO scheme allows for more efficient VHO decisions, reducing the occurrence of unnecessary handovers and minimizing the ping-pong effect caused by back-and-forth handovers. * By considering the link state information and the psychological tolerance time intervals associated with different types of real-time application delay, the Ac-VHO scheme optimizes the timing of VHO execution. This targeted approach ensures that handovers occur at the most suitable moments, taking into account the specific requirements and sensitivities of each application. Figure 10: Average VHO signaling cost of the various VHO schemes against VLC link recovery rate when obstructed for: (**a**) Vmax = 0.6 m/s and \(\rho\) = 0.1; (**b**) Vmax = 1.4 m/s and \(\rho\) = 0.1; (**c**) Vmax = 0.6 m/s and \(\rho\) = 0.9; (**d**) Vmax = 1.4 m/s and \(\rho\) = 0.9. ### Average Data Rate Comparison

As the VLC link recovery rate increases, the four schemes experience more frequent connections to the VLC link after a waiting period. Consequently, the data rate also increases in accordance with the VLC link recovery rate. For link recovery rates below 1/s, both the Ac-VHO and HA-VHO schemes achieve higher average data rates compared to D-VHO and dynamic D-VHO. Ac-VHO slightly outperforms HA-VHO in terms of data rate. This indicates that Ac-VHO and HA-VHO prioritize connecting to VLC links to maximize the data rate. However, dynamic D-VHO surpasses the other three schemes once the link recovery rate exceeds 1.2/s. This is attributed to the dynamic calculation of residence time in real time based on current link blocking information in the dynamic D-VHO scheme. When the RTA activity probability is 0.1, in Figure 11a,b, the data rate of Ac-VHO remains relatively flat with an increasing VLC link recovery rate. This behavior arises from Ac-VHO's focus on making VHO decisions based on changes in RTA type. Consequently, the proposed scheme prioritizes maintaining a high data rate by utilizing a static residency scheme that incorporates dynamic link state information. Thus, the data rate of Ac-VHO remains consistently high even when the RTA activity probability is low. Figure 11: Average data rate of the various VHO schemes against VLC link recovery rate when obstructed for: (**a**) Vmax = 0.6 m/s and \(\rho\) = 0.1; (**b**) Vmax = 1.4 m/s and \(\rho\) = 0.1; (**c**) Vmax = 0.6 m/s and \(\rho\) = 0.9; (**d**) Vmax = 1.4 m/s and \(\rho\) = 0.9. On the other hand, when the MT movement speed is 0.6 m/s and the RTA activity probability is 0.1, Ac-VHO places more emphasis on executing VHO decisions based on the link blocking state. The slower MT movement speed allows the proposed scheme to capture more detailed link state information. As a result, the data rate exhibits a smooth exponential increase as the VLC link blockage recovery rate improves. ### Average Comprehensive QoE Value Comparison

The QoE of video-based RTAs is closely related to the SINR. As a result, the QoE of the four VHO schemes, when applied to video-based RTAs, tends to improve as the VLC link recovery rate increases. For VoIP-based RTAs, the QoE is dependent on the delay experienced during handover, making it a critical factor for VHO schemes. The QoE of these four time-resident VHO schemes for VoIP-based RTA is influenced by the VLC link recovery rate and the number of VHOs. The signaling cost shows a slight increase when the recovery rate exceeds 0.6. The QoE for VoIP-based RTA exhibits an inverse relationship with the signaling cost. The trend in the QoE is nearly identical when considering web-based RTA. Therefore, the comprehensive QoE of all four schemes, as depicted in the figures, demonstrates an overall increase after the VLC link recovery rate surpasses 0.6/s.