## 4 Simulation Results and Analysis
From the simulation results in Figure 4, it can be seen that when the scintillation index, which characterizes the intensity of ocean turbulence, initially increases, the system performance does not deteriorate significantly. For example, \(\sigma_{I}^{2}=0.1074/0.2066\), and when the scintillation index increases, the corresponding two performance curves are basically close, while when \(\sigma_{I}^{2}=0.4548\), the performance gap between the scintillation index and the scintillation index increases, and the performance decreases significantly. The reason for this is that the asymptote formula for system outage probability represented by Equation (29) shows that its asymptote is related to \(m,k,ac,\xi^{2}\) several system attenuation parameters that characterize the intensity of small-scale Nakagami fading in RF links, large-scale shadow fading parameters, ocean turbulence intensity, and UWOC link pointing error. When setting the ocean turbulence scintillation index \(\sigma_{I}^{2}=0.1074/0.2066\), it can be observed that compared to other parameter values \((m,k)=(2.0,2.6)\), \(\xi=4.0\), the asymptotic value of the system average bit error rate in high SNR areas is basically determined by the fading  
Figure 3: The outage probability of RF-UWOC hybrid double hop system varies with the average SNR at different UAV heights and horizontal distances. parameter \(m=2\) of the RF link, which is independent of the intensity of ocean turbulence. When the intensity of ocean turbulence increases \(\sigma_{I}^{2}=0.4548\), it is \(ac=1.01\) less than the values \(m,k,5^{2}\) of the other three parameters, so the asymptotic value of this curve will be determined by the ocean turbulence coefficient \(ac=1.01\). Obviously, the performance of the outage probability curve corresponding to ocean turbulence \(\sigma_{I}^{2}=0.4548\) will be even worse than the performance \(\sigma_{I}^{2}=0.1074/0.2066\) of these two curves. Under the same conditions of ocean turbulence, the probability of system outage decreases with the increase in the average signal-to-noise ratio, and there is also performance improvement with the introduction of coherent HD. All of these indicate that increasing the received signal-to-noise ratio and using coherent reception are beneficial for improving system performance. Figure 5 shows the theoretical outage probability and MC simulation values of the hybrid dual-hop RF-UWOC relay communication system as a function of the average signal-to-noise ratio when the channel parameters of the first hop RF link are fixed but the jitter dispersion \(\sigma_{s}=25/35/65\) cm of the second hop UWOC link is changed, Correspond to the pink, blue, and red curves in the figure respectively. At this point, the horizontal and vertical distances between UAV and R in the first hop RF link are set to: (900 m, 2000 m), and the coefficients that follow generalized K-fading are set to: \(m=2.0,k=2.6\). The pointing error \(\xi^{2}=w_{z_{q}}^{2}/4\sigma_{s}^{2}\) of the second hop UWOC link varies with jitter deviation (at this point, the receiver radius \(r_{a}=30\) cm and beam width \(w_{z}=30\) cm); underwater transmission distance \(d=20\) m, ocean turbulence scintillation index \(\sigma_{I}^{2}=0.1074\). From the simulation results in Figure 5, it can be seen that as the jitter deviation \(\sigma_{s}\) value representing pointing error gradually increases, the overall curve of the system outage probability changing with the average signal-to-noise ratio gradually rises, that is, the outage probability performance shows a downward trend. The reason for this is that the value represents the amplitude of random jitter between the received light intensity at the receiver and the center of the receiving aperture. Obviously, the larger the jitter amplitude, that is, the larger the value, the less signal energy will fall into the receiving aperture, the lower the received signal-to-noise ratio (SNR), and the probability of outage will inevitably decrease.