## 5 Simulation Results and Performance Analysis
(b) Single-satellite multi-beam multi-user. (c) Multi-satellite single-beam multi-user. (d) Multi-satellite multi-beam multi-user. Figure 7: Simulation framework. In this paper, as shown in Figure 10(a), there is data diversity in the multi-beam satellite communication system which means that the data of one user is transmitted through different physical channels (such as different beams of one satellite or different beams of multiple satellites) after segmentation. The SINR of each beam is not superimposed, and the packet is not repeatedly superimposed and sent. In order to better show that the difference of the SINR of each beam, we have underlined the relationship between SINR and BER of different beams in Figure 11 respectively. When the SINR of the beam \(b_{22}\) is 1.5, the BER of the beam \(b_{22}\) is 0.12. When the SINR of the beam \(b_{23}\) is 2.1, the BER of the beam \(b_{23}\) is 0.13. When the SINR of the beam \(b_{13}\) is 2.5, the BER of the beam \(b_{13}\) is 0.15. In this paper, unlike traditional MIMO systems, we use beams with similar SINRs to transmit different packets to achieve data diversity. After segmenting packets at the transmitter, the received segmented packets are buffered at the receiver. After multiple TTIs, the packets will be reorganized and combined into a packet. Finally, the data packet would be processed. According to the above analysis, the multi-beam satellite cooperative transmission scheme based on cross-layer and cross-dimension resources optimization and irregular gradient adaptive packet segmentation can significantly improve the normalized system throughput. However, the normalized system throughput is different under the proposed algorithm with different iterations. Figure 10(b) shows that as the number of iterations increases, the normalized system throughput increases and then remains at a stable amount. When the normalized system throughput reaches stabilization, the increase of the number of iterations does not significantly improve the normalized system throughput, but the time required still increases. Therefore, in this paper, the number of iterations is set to 3. Figure 10: Wireless resource index optimization. Figure 9: Available and allocated resources. As shown in Figure 12, in the multi-beam satellite communication system, we adopt other resource allocation algorithm to compare with the proposed algorithm in this paper, which are congestion pricing game algorithm, dynamic bargaining algorithm, particle swarm optimization algorithm, and genetic algorithm. According to the research results in references [47; 48], we found that, at the same time, there are 3 multi-beam satellites covering users at \(55^{\circ}\), \(15^{\circ}\), \(-40^{\circ}\) or 2 multi-beam satellites covering users at \(55^{\circ}\), \(-15^{\circ}\). We analyze the influence of different numbers of satellites on the normalized system throughput. It can be clearly seen from Figure 12 that with the increase of the number of satellites, the normalized system throughput is also increasing. Among them, the worst performance is the genetic algorithm. The best one is the proposed algorithm in this paper. In other words, with the same number of satellites under optimal parameters, the proposed algorithm in this paper can better improve the normalized system throughput. After selecting the optimal resources, packets are segmented to be adapted to the optimal resources, which can make full use of resources, increase the transmission rate, and increase the system throughput at the same time. We evaluate the performance of different algorithms according to the user satisfaction index proposed above. As shown in Figure 13, the user satisfaction index using the proposed algorithm in this paper is higher. The proposed algorithm carries out cross-layer and cross-dimension optimization. Firstly, the optimization selection is carried out among different satellites. Then the optimization selection is carried out among beams of the optimal satellite.