# Outage Performance of SWIPT-D2D-Based Hybrid Satellite-Terrestrial Networks
## 4 Numerical Results  
In this section, we conduct numerical investigations for the proposed PS-D2D-based and TS-D2D-based HSTNs, and validate our analytical OP expressions through Monte Carlo simulations. Unless otherwise explicitly specified, the parameters are set as \(\omega=0.7\), \(R_{p}=0.5\,\text{bps}/\text{Hz}\), \(\tau=0.1\), \(\gamma^{\prime}{}_{p}=0.414\), \(\gamma_{p}=1.828\), \(\gamma_{p,ts}=2.182\), \(\Omega_{\text{rr1}}=\Omega_{\text{r1}u2}=1\), and \(m_{\text{r1}u2}=1\), and \(\eta_{s}=\eta_{r}\) as the SNR. The shadowed Rician fading parameters for the satellite-terrestrial link \(S-R\) are considered under the average shadowing (AS) condition as \(m_{sr}=5\), \(b_{sr}=0.251\), and \(\Omega_{sr}=0.279\) in reference [27]. The shadowed Rician fading parameters for the satellite-terrestrial direct link \(S-U_{2}\) are considered under the heavy shadowing (HS) condition as \(m_{\text{s}u2}=2\), \(b_{\text{s}u2}=0.063\), and \(\Omega_{\text{s}u2}=0.0005\) in reference [27]. To make the relative approximation error negligible, we set \(L=20\) in the \(L\)-step staircase approximation approach. To verify the proposed analysis models, \(10^{5}\) channel realizations of shadowed Rician and Nakagami-\(m\) fading are generated. Figure 3 depicts the OP curves of \(U_{1}\) against the SNR with different Nakagami coefficients for the TS-D2D and PS-D2D schemes with \(\rho=0.7\). Herein, the satellite-terrestrial direct link \(S-U_{1}\) is considered under the AS condition. Even though the threshold data rate of the TS-D2D scheme is slightly higher than that of the PS-D2D scheme, the outage performance of \(U_{1}\) for the TS-D2D scheme is still better than that for the PS-D2D scheme. This is due to the increased amount of energy harvested and utilized for the ID of the TS-D2D scheme than that for the PS-D2D scheme. Furthermore, the terrestrial relay link achieves a higher outage performance gain for the TS-D2D scheme than that for the PS-D2D scheme. Figure 3: The OP of \(U_{1}\) versus the SNR with different Nakagami coefficients for the TS-D2D and PS-D2D schemes. Figure 4 illustrates the OP curves of \(U_{1}\) against the PS coefficient with different Nakagami coefficients under HS and AS conditions for the PS-D2D scheme with \(\eta_{s}=23\) dB. Herein, the satellite-terrestrial direct link \(S-U_{1}\) is considered under HS and AS conditions, respectively. It can be observed that the outage performance gradually improves as the PS coefficient increases. This is due to the fact that \(U_{1}\) utilizes more energy for ID. Significantly, \(U_{1}\) can achieve the optimal outage performance by using all the energy for ID with \(\rho=1\). However, the cooperation from \(U_{1}\) to \(U_{2}\) will be ineffective. Figure 5 exhibits the OP curves of \(U_{2}\) against the SNR with different Nakagami coefficients for the TS-D2D and PS-D2D schemes with \(\rho=0.7\). Herein, the satellite-terrestrial direct link \(S-U_{1}\) is considered under the AS condition. Even though the transmit power of the TS-D2D scheme is similar to that of the PS-D2D scheme, the outage performance of \(U_{2}\) for the PS-D2D scheme is still better than that for the TS-D2D scheme. This is due to the presence of the energy transmission time slot of the TS-D2D scheme, which results in a higher threshold data rate for the TS-D2D scheme than that for the PS-D2D scheme. Figure 4: The OP of \(U_{1}\) versus the PS coefficient with different Nakagami coefficients under HS and AS conditions for the PS-D2D scheme. Figure 5: The OP of \(U_{2}\) versus the SNR with different Nakagami coefficients for the TS-D2D and PS-D2D schemes. Figure 6 presents the OP curves of \(U_{2}\) against the PS coefficient with different Nakagami coefficients under HS and AS conditions for the PS-D2D scheme with \(m_{m1}=1\) and \(\eta_{s}=25\) dB. Herein, the satellite-terrestrial direct link \(S-U_{1}\) is considered under HS and AS conditions, respectively.