## 5 Results
On the other side and observing the results shown in Figure 3 in [69], we can observe how when \(\rho\) tends to 1, an improved performance of the entire system is obtained (when maintaining the values of \(\alpha\) and \(\beta\)) since the overall atmospheric scattering power travels coupled to the LOS component; but when \(\rho\to 0\), then all the scattering power travels through the \(U_{5}^{G}\) field, which is statistically independent from the other field components, as represented in Figure 2. From Section 3, \(\rho\) denotes the amount of scattering power coupled to the LOS component. As a last comment, the solid blue and red lines in Figure 3 (corresponding to \(\sigma_{h_{2}}^{2}=0.0496\) and \(1.0652\), respectively, for the underwater FSO segment, while considering, in both cases, an ideal AWGN channel with an absence of turbulence for the terrestrial FSO link) will be subsequently displayed when showing the results associated with the coded transmission schemes (Figures 4-6) with the purpose of providing an immediate comparison. Regarding the case in which the CBER of any coding scheme is unknown and independent of itself, the hyperexponential fitting technique can be applied, resulting in a closed-form analytical expression for the ABER, as shown in Equation (25). There, by solely fitting the values for the parameters \(a_{c},b_{c}\), and \(c_{c}\) (see Table 1 for the schemes analyzed in this paper) in the ideal case of an AWGN channel (CBER), we can achieve a completely accurate performance for ABER. The inclusion of signaling techniques such as OOK-GScc and vw-MPPM and their behavior in Figures 4-6 corroborates that feature. Hence, assuming the same previously considered value of ABER (\(10^{-4}\)) used with the aim of comparing all those coded transmission schemes with different code rates, the required SNRs to satisfy that aforementioned ABER are included in Table 2 for the different coding techniques addressed in this paper. Note that the values for the vw-MPPM format with a code rate of \(1/4\) are taken from Figure 2b in [44]. Figure 4: Analytical ABER and Monte Carlo simulation results (circles) vs. SINR \(\gamma_{0}\) for an OOK-GScc format with code rate of \(1/4\) under weak (\(\sigma_{h_{2}}^{2}=0.0496\)), weak-to-moderate (\(\sigma_{h_{2}}^{2}=0.2453\)) and strong (\(\sigma_{h_{2}}^{2}=1.0652\)) salinity-induced turbulence and different Malaga turbulence intensities in the terrestrial FSO link. Scenarios and values of irradiance variances in the underwater medium taken from acquired data presented in [68]. In solid lines, the performance of the system when only oceanic turbulence is considered is represented. Figure 5: Analytical ABER and Monte Carlo simulation results (circles) vs. SINR \(\gamma_{0}\) for an OOK-GScc format with a code rate of \(1/8\) under weak (\(\sigma_{h_{2}}^{2}=0.0496\)), weak-to-moderate (\(\sigma_{h_{2}}^{2}=0.2453\)) and strong (\(\sigma_{h_{2}}^{2}=1.0652\)) salinity induced turbulence and different Malaga turbulence intensities in the terrestrial FSO link. Scenarios and values of irradiance variances in the underwater medium taken from acquired data presented in [68]. In solid lines, the performance of the system when only oceanic turbulence is considered is represented. For all cases, vw-MPPM offers the best performance where codewords with different Hamming weight are permitted, obtaining higher improvements in performance as the length of the data block increases. Finally, we want to remark that the accuracy of the proposed expressions in this paper is fully corroborated by numerical simulations, corroborating the validity of Equations (21) and (25).