# OTFS-Based Handover Triggering in UAV Networks
## 7 Numerical Analysis
### Against Number of UAVs  
In this part of numerical analysis, we compare the handover performances of the candidate schemes against the number of deployed UAVs. In these simulations, we use \(n^{\prime}=12\), an HST speed of \(500\) Km/Hr, and the worst case of \(P_{th}=0\) dB. Also, we assume perfect DD channel estimation, i.e., \(MSE_{\mathcal{H}}=0\) in (38).  
Figures 9-11 show the handover overhead, the average throughput, and the ping-pong ratio of the compared schemes against the number of UAVs. Generally, as the number of UAVs increases, the handover overhead and the ping-pong ratio increase, while the average throughput decreases. This is because when increasing the number of UAVs, using \(P_{th}=0\) dB as a worst-case scenario, the HST will always be handed over among the deployed UAVs, as there will always be a high possibility of finding a better  
Figure 8: Ping-pong ratio against \(P_{th}\).  
Figure 6: Handover overhead against \(P_{th}\).  
Figure 7: Average throughput against \(P_{th}\).  
UAV with a higher data rate than the currently connected one. This possibility will be further increased as we increase the number of UAVs deployed, resulting in increasing the handover overhead and the ping-pong ratio, as given in Figures 9 and 10. As given in (55), average throughput is inversely related to handover overhead, and the handover overhead has the dominant effect over the average data rate on the value of the average throughput. Thus, it declines when increasing the number of UAVs, as illustrated in Figure 10, due to the increased handover overhead depicted in Figure 9. Additionally, the handover metrices of all schemes saturate as the number of deployed UAVs grows. This is due to the high density of UAVs, which shortens the separation distances among candidate UAVs. As a result, candidate UAVs offer nearly equal handover metrics, leading to a saturation in their performance. From these figures, the proposed scheme achieves significant improvements in handover metrics compared to other schemes. It also exhibits the lowest rates of increase in handover overhead and ping-pong ratio, as well as the lowest rate of decrease in average throughput. This superior handover performance is attributed to its stable handover decisions, resulting from constant DD channel gains. As a numerical example, when the number of UAVs is equal to two, the proposed scheme achieves 0.001 s, 17.3 Mbps, and 0.0005 for the handover overhead, the average throughput, and the ping-pong ratio, respectively. However, the OFDM (RSS) scheme achieves 0.007 (0.014) s, 4.2 (2.3) Mbps, and 0.0051 (0.384), respectively. When the number of UAVs is set to 14, the proposed scheme achieves a handover overhead of 0.0019 s, average throughput of 13.6 Mbps, and ping-pong ratio of \(7\times 10^{-4}\). However, the OFDM (RSS) scheme achieves 0.0171 (0.0324) s, 2.03 (1.16) Mbps, and 0.0084 (0.8816) for handover overhead, average throughput, and ping-pong ratio, using 14 UAVs, respectively.  
Figure 10: Average throughput against the number of UAVs.  
Figure 9: Handover overhead against the number of UAVs.