正交时频空(Orthogonal Time Frequency Space,OTFS)调制因其在高速移动场景下优越的抗多普勒频移特性,被视为未来低地球轨道(Low Earth Orbit,LEO)卫星通信的关键候选技术。然而,OTFS信号固有的峰均功率比(Peak-to-Average Power Ratio...正交时频空(Orthogonal Time Frequency Space,OTFS)调制因其在高速移动场景下优越的抗多普勒频移特性,被视为未来低地球轨道(Low Earth Orbit,LEO)卫星通信的关键候选技术。然而,OTFS信号固有的峰均功率比(Peak-to-Average Power Ratio,PAPR)问题,会严重降低卫星高功率放大器(High-Power Amplifier,HPA)的效率,并引入显著的非线性失真,从而恶化误码率(Bit Error Rate,BER)性能。为解决此问题,提出了一种创新的混合自适应削波(Hybrid Adaptive Clipping,HAC)与神经网络预失真(Neural Network Predistortion)的方法——HAC-NNP。自适应削波(Adaptive Clipping,AC)模块根据实时信道质量或业务需求动态调整削波门限,在PAPR抑制和信号原始失真之间取得初步平衡;轻量级的神经网络(Neural Network,NN)预失真器在发射端对削波后的信号进行处理,训练后用于补偿由“削波处理”和“卫星HPA非线性效应”共同引入的复杂失真。仿真结果表明,在典型的LEO卫星信道和HPA非线性模型下,与传统削波方法相比,该HAC-NNP方法在将PAPR降低约3.5 dB的同时,能够显著改善由削波和HPA非线性共同导致的信号失真,将BER性能恢复至接近无HPA非线性影响的理想水平。展开更多
In this paper,we analyze the physical layer security(PLS)performance of a free-space optical(FSO)communication system composed of a transmitting satellite and ground users.Specifically,the FSO fading channels follow t...In this paper,we analyze the physical layer security(PLS)performance of a free-space optical(FSO)communication system composed of a transmitting satellite and ground users.Specifically,the FSO fading channels follow the Málaga distribution.Further,we scrutinize the influence of non-zero boresight pointing errors and angle-of-arrival fluctuations on the PLS performance for the first time.We derived the probability density function and cumulative density function of the FSO link,followed by the closed-form expressions of the secrecy outage probability(SOP)and the probability of strictly positive secrecy capacity(SPSC).The asymptotic SOP expression at the high signal-to-noise ratio regime and diversity order are also provided to reveal the physical mechanism of the PLS of the considered system.Finally,Monte Carlo simulation results are presented to verify the correctness of the analytical expressions.The results afford helpful insights for the future design of satellite FSO communication systems.展开更多
基金National Natural Science Foundation of China(Grant No.62271202,62027802)Zhejiang Provincial Natural Science Foundation of China(Grant No.LZ25F010004)。
文摘In this paper,we analyze the physical layer security(PLS)performance of a free-space optical(FSO)communication system composed of a transmitting satellite and ground users.Specifically,the FSO fading channels follow the Málaga distribution.Further,we scrutinize the influence of non-zero boresight pointing errors and angle-of-arrival fluctuations on the PLS performance for the first time.We derived the probability density function and cumulative density function of the FSO link,followed by the closed-form expressions of the secrecy outage probability(SOP)and the probability of strictly positive secrecy capacity(SPSC).The asymptotic SOP expression at the high signal-to-noise ratio regime and diversity order are also provided to reveal the physical mechanism of the PLS of the considered system.Finally,Monte Carlo simulation results are presented to verify the correctness of the analytical expressions.The results afford helpful insights for the future design of satellite FSO communication systems.
