基于正交时频空技术的低轨卫星通信的安全分析

Secrecy analysis for orthogonal time frequency space technique based LEO satellite communication

为了提高低轨卫星下行通信系统的安全性能,引入协作无人机干扰机向窃听者发送干扰信号。为了弥补现有频偏补偿方法的不足,下行传输基于正交时频空技术,将时变频选信道转换为时延多普勒域中近似非衰落的信道,以应对低轨卫星高移动性带来的严重多普勒效应。采用阶矩匹配的方法,求得阴影莱斯分布星地信道叠加和的概率分布函数,进而推导出合法接收端安全中断概率的闭式解。仿真结果验证了相对于正交频分复用方案,采用无人机干扰机可以有效增强保密传输能力,以及应用正交时频空方案对提高下行低轨卫星通信的安全性能的优势。

In order to improve the security performance of low earth orbit(LEO)satellite downlink communication sys-tem,a cooperative UAV was employed to send jamming signals against the eavesdroppers.In particular,the downlink transmission was based on the orthogonal time frequency space(OTFS)technique to combat the severe Doppler effect caused by the high mobility of the LEO satellite.The closed form expression for the security outage probability(SOP)was derived at the legitimate receiver,where a novel moment matching approach was used for finding a summed proba-bility distribution function(PDF)of the shadowed-Rician(SR)distributed terms.Simulation results prove that the SOP performance advantage of the downlink LEO satellite communication achieved by OTFS over OFDM scheme,and show the effectiveness of employing unmanned aerial vehicle(UAV)jammer in terms of enhancing secrecy transmission.