## 3 Simulation and Results  
This section presents the performance of the channel allocation method for the NGSO satellite proposed previously in scenarios of sharing spectrum resources with GSO satellite communication systems. For simplicity, let us assume that the GSO and NGSO satellites are equipped with multi-beam antennas that can produce 7, 19, and 37 beams in the coverage area, which just make up an equilateral hexagon with different levels as illustrated in Figure 8a. The ground stations of the interfered communication system are placed in the centers of these beams, and the antenna beams of the NGSO satellite stay illuminated, which keeps transmitting information constantly. The simulation and orbital parameters are taken as shown in Tables 2 and 3. The experiments were simulated in the computer with the CPU of i7-10700 2.90 GHz. The variations of SNR and SINR in different beams with and without channel allocation are described in the following paragraphs. We only zoom in locally on Figure 9 for the 7-beam scenario because there are too many lines for the 19-beam and 37-beam scenarios. The GSO ground stations are in the centers of the beams, so the SNRs are the same for all the ground stations. For convenience, we only use one line to signify the SNRs. In the legend of Figure 9, Pi denotes the GSO ground station located in the beam number \(i\) as illustrated in Figure 8a. It is obvious that from the following figures (which regard the evaluation indexes variation of the GSO ground stations in different beams), the value of SNR remains unchanged during the whole simulation period, while the value of SINR is equal to that of SNR during the beginning and end of the simulation period. This is because, at that time, the two satellites are too distant from each other to bring about severe interference. As time goes by, the coverage area of the NGSO satellite starts to overlap with that of the GSO satellite, and the level of interference is augmented. As the NGSO satellite moves in its orbit, it appears above the coverage area of the GSO satellite from south to north. Therefore, we can see that the ground stations whose positions of beam centers are in the middle of the configuration of coverage would bear more severe interference during the simulation period. The SINR of the GSO ground stations after channel allocation increases obviously in its level. Regarding the scenario with seven beams, the enumeration method and beam search algorithm are both investigated to obtain the solution to channel allocation. The enumeration method takes about half an hour to solve for the solution, while the beam search algorithm takes only about 2 min. From the variation of SINR, we notice that the final results are almost identical, although the computational time is far less for the beam search algorithm. Figure 9a illustrates that the GSO ground stations in the centers of the beams with numbers 1, 0, and 4 suffer more severe interference gradually with the satellites  
Figure 9: SNR and SINR of different GSO ground stations in different beams for the seven-beam scenario without and with channel allocation. (**a**) SNR and SINR of different GSO ground stations in different beams for the seven-beam scenario without channel allocation; (**b**) SNR and SINR of different GSO ground stations in different beams for the seven-beam scenario with channel allocation. moving from the south to the north. The stations P2 and P6 are placed on the south part of the coverage area so the SINRs decrease earlier compared with P3 and P5. The minimum SINR of each GSO ground station depends on the distance between the station and the interference source. From Figure 9 it is evident that, after channel allocation, the minimum SINR raises from \(-5\) dB to \(27\) dB, an increment of over \(30\) dB in SINR is achieved. The average value of SINR also presents an outstanding improvement even in the most severe scenario of interference.