In the fifth-generation (5G) and future sixth-generation (6G) networks, improving spectral efficiency and system capacity is still the main concern. Adding LEO satellite to the construction of 5G and 6G can make the network structure three-dimensional, which lets the network construction get rid of the limitation of ground space propagation distance and makes the wider area enjoy the convenience of 5G and 6G. However, due to the large link distance between space and the ground, the communication of LEO satellite in Ka band is greatly affected by rain attenuation and shadow fading. In order to improve the ergodic capacity of LEO satellite downlink, this paper attempts to apply nonorthogonal multiple access (NOMA) to hybrid channels with rainfall fading and shadow fading. In the simulation results, the ergodic capacity of orthogonal frequency division multiple access (OFDMA) and NOMA is compared, and it is found that the system capacity of hybrid channel can be improved by increasing the power allocation factor of NOMA. The experiments have studied the influence of LEO satellite's orbital height, fading degree, and transmission power in the communication link on the performance of LEO satellite system in this paper. The experimental results show that the lower the orbit height is, the better system performance will become under the same fading degree. Moreover, the energy consumed gradually decreases with the transmission power becoming small.

中文翻译：

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NOMA在LEO卫星雨衰衰落混合信道中的性能分析

在第五代（5G）和未来的第六代（6G）网络中，提高频谱效率和系统容量仍然是主要关注点。在5G、6G建设中加入LEO卫星，可以使网络结构立体化，让网络建设摆脱地面空间传播距离的限制，让更广的区域享受到5G、6G的便利。然而，由于空间与地面之间的链路距离较大，Ka波段LEO卫星的通信受雨衰和阴影衰落的影响较大。为了提高LEO卫星下行链路的遍历能力，本文尝试将非正交多址（NOMA）应用于降雨衰落和阴影衰落的混合信道。在模拟结果中，比较正交频分多址（OFDMA）和NOMA的遍历容量，发现通过提高NOMA的功率分配因子可以提高混合信道的系统容量。本文通过实验研究了LEO卫星的轨道高度、衰落度和通信链路中的发射功率对LEO卫星系统性能的影响。实验结果表明，轨道高度越低，在相同衰落度下系统性能越好。此外，随着发射功率变小，消耗的能量逐渐减少。本文通过实验研究了LEO卫星的轨道高度、衰落度和通信链路中的发射功率对LEO卫星系统性能的影响。实验结果表明，轨道高度越低，在相同衰落度下系统性能越好。此外，随着发射功率变小，消耗的能量逐渐减少。本文通过实验研究了LEO卫星的轨道高度、衰落度和通信链路中的发射功率对LEO卫星系统性能的影响。实验结果表明，轨道高度越低，在相同衰落度下系统性能越好。此外，随着发射功率变小，消耗的能量逐渐减少。