【摘要】 随着6G通信研究的深入，卫星互联网作为空天地一体化网络的重要组成部分，针对用户未知卫星星历先验条件且面临显著自由空间路径损耗的挑战，提出一种基于正交时频空间（OTFS）调制的联合多普勒频移估计、卫星轨道参数反演与RIS动态波束成形方法。首先，利用OTFS调制的分数多普勒特性，从接收信号中估计复杂时变的大多普勒频移，接着通过动力学模型，提出了基于卫星轨道参数的阻尼梯度下降算法，解算卫星轨道参数及卫星实时位置。进一步，基于信道状态信息，提出动态优化RIS反射单元相位的策略，通过相干波束成形补偿自由空间路径损耗，增强接收信号功率。仿真结果表明，所提方法在无需星历先验信息的条件下，能同时实现百米级精度的卫星实时定位与显著的通信速率提升，为星地高可靠动态通信提供了理论与技术支撑。更多还原

【Abstract】 With the in-depth research of 6G communication,the satellite Internet,a key part of the space-air-ground integrated network,has gained more attention.Facing the challenges of users’ lack of prior satellite ephemeris knowledge and significant free-space path loss,a method integrating Doppler shift estimation,satellite orbital parameter inversion,and RIS dynamic beam-forming based on orthogonal time-frequency space (OTFS) modulation is proposed.Firstly,the fractional Doppler property of OTFS modulation is used to estimate complex time-varying Doppler shifts from the received signals.Then,a damped gradient descent algorithm based on satellite orbital parameters is proposed through a dynamic analysis model to calculate the orbital parameters and real-time position.Furthermore,a strategy for dynamically optimizing RIS reflecting element phases is presented based on channel state information.Therefore,coherent beam-forming is used to compensate for path loss and enhance the received signal power.Simulation results show that the proposed method can achieve real-time satellite positioning with 100-meter-level accuracy and a notable communication rate improvement without prior ephemeris information,offering theoretical and technical support for reliable satellite-to-ground dynamic communication.更多还原