## 4 Results  
In this section, we will evaluate the proposed scheme via a simulation. The satellite orbit height of the OneWeb system is 1200 km, each orbit plane contains 40 satellites, the included angle between each satellite is \(9^{\circ}\) and the orbit inclination of the OneWeb, SpaceX and Telesat is between \(37.4^{\circ}\) and \(87.9^{\circ}\)[34]. When the orbit height becomes higher, the frequency offset brought by the satellite will be reduced, which is conducive to reducing the adverse impact of the frequency offset on the system. Therefore, we consider the height of the LEO satellites as 1200 km. The satellite orbit inclination is \(86.4^{\circ}\). The two satellites are located on the same orbital plane with an included angle of \(9^{\circ}\). The time period for each satellite that can connect with the IoT UT is 16 min. The terminal antenna adoptsthe reflector antenna defined in [35]. The normalized antenna radiation pattern can be expressed as  
\[G(\theta)=\left\{ \begin{array}{l}1,\theta=0^{\circ}\\ 4\Big{|}\frac{I_{1}(ka\sin\theta)}{ka\sin\theta}\Big{|}^{2},0^{\circ}{<}|\theta| \leq 90^{\circ}\end{array} \right. \tag{39}\]  
where \(J_{1}(x)\) denotes the first kind of first-order Bessel function, \(a\) is the radius of the circular hole of the antenna, \(k=2\pi f/c\) represents the wave number, \(f\) is the central frequency of the system and \(c\) denotes the speed of light in vacuum. \(\theta\) represents the angle measured from the bore sight of the antenna's main beam. Table 1 shows the link parameters of the system. A Rician channel is adopted, and the Rician factor is 13.3 dB. When the transmitted signals from two satellites do not arrive at the terminal at the same time, the transmitted signals from different satellites will cause interference and affect the demodulation performance. In the case of an ideal frequency offset compensation, the BER performance of the dual-stream signals arriving at the terminal with different time intervals is analyzed. Figures 6 and 7 show the case of no time interval, a half CP time interval and two CP time intervals. When the reflector antenna is used, the mutual interference between the two satellites of the signals is small. Thus, different time intervals have little effect on the demodulation performance of the system. In order to verify the power control performance of different power control schemes, the dual transmission with no power control, open-loop power control and closed-loop power control are investigated. The shadow fading is considered for suburban and rural scenarios, and the variance value is given by [33]. The target SINR is set to 7 dB. The power adjustment cycle is set to 1 s. Perfect synchronization is assumed. Figures 8 and 9 show the SINR versus time curve under different power control schemes. Compared with the no power control scheme, the SINR with power control schemes are more stable. In addition, the closed-loop power control scheme is more stable than the open-loop power control. However, the closed-loop power control scheme needs the feedback information  
Figure 10 shows the dynamic characteristic of the frequency offset experienced by the two satellites. It can be seen that the frequency offset caused by the satellites is different. At the receiver of the IoT terminal, the frequency offset caused by different satellites should be compensated individually. Figure 11 shows the comparison of the terminal communication rate under a perfect frequency offset compensation and the proposed synchronization schemes. Moreover, the effects of the power control scheme are also investigated with the proposed synchronization scheme. When the transmission power is 5 dbw, the communication rate can hardly be maintained above 1 Gbps. When the transmission power increases to 10 dbw, the communication rate can be maintained above 1 Gbps for about ten minutes. When adopting the power control scheme, the transmit power of two satellites will change according to the adopted power control scheme, and the SNR can maintain a relatively stable range.