一种基于GEO卫星网络的IP组网方案的设计及仿真

当前,大部分支持IP的卫星系统只是提供了一个连接地面路由器的物理通道,难以满足带宽接入、多媒体服务以及星地网络一体化等新的需求.为此,提出了一个分组传输和交换均基于IP的GEO卫星系统,采用三层路由交换的组网方案,实现了同一交换域内用户信息的链路层快速转发,以及不同交换域间用户IP信息的网络层路由交换处理.最后,研究了最简单的RIP路由协议在此GEO卫星网络中的适应性,利用OPNET仿真软件对其进行了建模仿真及结果分析.     

高轨GPS信号可用性分析

针对目前国内关于高轨GPS信号可见性研究大多以几何分析为主,工程实现指导性不强的缺点,文章以GPS接收机系统指标设计为目标,引入接收机等价增益概念,结合空间几何模型与信号链路传播特点,考虑GPS发射天线增益、接收机信号处理时间、GPS星座状况、接收天线增益等实际因素,对适用于高轨GPS信号可用性进行分析。仿真表明-180 dBW接收功率下,通过接收更多GPS旁瓣信号,GPS接收机能有效应用于高轨航天器导航。     

基于LMS估计的卫星移动通信定时同步优化

针对采用长期演进(LTE)通信标准的地球静止轨道(GEO)卫星移动通信系统上行定时误差会影响单载波频分多址技术正交性的问题,在LMS线性估计算法的基础上提出了一种适用于大时延环境下单载波频分多址定时同步优化方法。该方法对用户与卫星之间传输时延的变化进行估计,通过闭环控制补偿减小上行定时误差。仿真表明:该方法在使用LTE标准帧结构时,能保护用户上行信号正交性,避免符号间干扰,且传输速率损失约为9%,远低于传统拓展帧结构方法带来的损失,验证了方法的优越性。     

HARQ–ARQ interaction method for LTE‐based mobile satellite communication system

Hybrid automatic repeat request (HARQ) and automatic repeat request (ARQ) of the terrestrial long‐term evolution (LTE) system are designed considering the very short propagation delay of terrestrial environment. Therefore, when HARQ and ARQ are applied to the LTE‐based mobile satellite communication system, the inefficiency is caused by the long propagation delay of satellite environment. This paper proposes the interaction method between HARQ and ARQ for the decrease of inefficiency in the LTE‐based mobile satellite communication system. The existing concept of layered architecture about HARQ and ARQ is also maintained in our interaction method. Simulation results reveal that our proposed scheme can provide the larger spectrum efficiency than that of the non‐interaction scheme in all environments. The performance improvement can be up to 2.04 times through the interaction method. Copyright © 2014 John Wiley & Sons, Ltd.     

倾斜轨道同步卫星通信系统及其应用探讨

本文介绍可在赤道平面以外的空间利用C频段频谱的倾斜轨道同步卫星通信系统，并对具体的星座结构、工作频段、干扰协调和系统方案等作了初步探讨。     

卫星通信在信息高速公路中的地位与作用

本文从信息高速公路的无缝隙网络构成及个人用户驱动的基本特征出发，论述了卫星通信在未来全球／区域／国家信息高速公路中的独特地位与作用；进而较详细地讨论了涉及未来信息高速公路的卫星通信的基本发展态势及一些值得引起注意和必须深入研究的重要技术问题和规则、政策问题。     

Attenuation statistics estimated from radar measurements in MEO satellite communication systems for mobile terminals

Based on experimental data, we have reported a method to scale the cumulative time, T_F,T(A), a given attenuation, A (dB), is exceeded in a MEO satellite system in fixed terminals, to the time, T_M,T(A), A is exceeded in mobile terminals. Zigzag routes and ring roads simulated city patterns; straight routes simulated freeways. In all cases, T_M,T(A) can be expressed as T_M,T(A)=ξT_F,T(A) with a probability scaling factor ξ independent of A. Although the satellite systems have been simulated at 19.77 GHz, the results concerning ξ can be considered frequency‐independent. We have used a very large number of rain‐rate maps of storms randomly observed in 1991–1992 by a meteorological radar in Northern Italy. The speed of vehicles was modelled as a lognormal random variable. We found: (a) in zigzag routes T_M,T(A)<T_F,T(A), i.e. ξ<1, with results depending on vehicle speed modelling and starting conditions; (b) in ring roads there is no difference between fixed and mobile systems (ξ≈1); (c) in straight freeways T_M,T(A)?T_F,T(A) (ξ?1) and T_M,T(A) can change significantly in different straight lines and in opposite directions (anisotropy and asymmetry) for medium–large attenuation. When compared with zigzag routes or ring roads, the performance in straight freeways is the most optimistic. The numerical values of ξ applicable to a MEO satellite system are not significantly different from those applicable to a GEO satellite system working in the same conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

三轴稳定GEO卫星漫反射光变特性

利用天文测光方法研究了地球同步轨道卫星可见光波段的反射光变特性.以三轴稳定地球同步轨道通讯卫星为研究样本,进行了可见光波段的光学非高分辨成像观测,并使用天文标准星进行定标.基于相位角序列的测光观测数据表明:在大相位角区域卫星光变曲线分布与漫反射光照数学模型计算结果有很好的一致性,以卫星主体和太阳能电池板的漫反射效应为主;而在小相位角区域与漫反射模型计算结果有明显的差异,为卫星的太阳帆板镜面反射效应影响所致.     

GEO卫星受IGSO卫星干扰情况分析研究

文章以倾斜地球同步轨道卫星(IGSO)地球站干扰对地静止轨道卫星(GEO)为研究对象,分析了IGSO卫星运行轨迹以及干扰信号出现的原理,最终得出规避干扰出现的建议或者措施,为卫星操作者提供技术参考。