SIMULATION AND ANALYSIS OF PERFORMANCE ON THE COMPASSTM ENHANCED BY GEO AND IGSO

Positioning accuracy of the Global Navigation Satellite System (GNSS) can be analyzed by Positioning Dilution Of Precision (PDOP).In order to enhance the navigating performance of Asia and the Pacific areas,this paper analyzes the next generation BeidouTM navigation satellite system (CompassTM) enhanced by Geostationary Earth Orbit (GEO) and Inclining GeoSynchronized Orbit (IGSO).As global navigation satellite system,CompassTM must be robust enough to avoid system layoff,when some nodes are not available.So,the CompassTM enhanced by GEO and IGSO constellation is proposed and analyzed its PDOP proformance,this paper shows some exciting results of performance of CompassTM enhanced by GEO and IGSO.From the simulation results,we can found that:when more than fifteen satellites are invalid,the enhanced system could be operating normally.     

GEO卫星移动通信系统信道分配策略研究

根据移动终端越区切换的物理过程,结合GEO系统的特点,建立移动终端运动的数学模型,将地面移动通信系统的无优先权、预留信道和排队方案3种信道分配方案应用于GEO系统,进行仿真分析。仿真结果表明,预留信道方案虽然能够降低切换呼损率,但却增加了初始呼叫呼损率;排队混合方案在取得与预留信道方案同样的切换呼损率时,可以获得更低的初始呼叫呼损率,排队混合方案优于预留信道方案。     

卫星系统新技术--应用机遇及发展策略考虑(下)

结合市场导向下的技术驱动重要性，重点论述现代卫星系统新技术及其在中国的应用机遇和发展策略。     

Modified methodology for computing interference in LEO satellite environments

Computing interference is very important in satellite networks design in order to assure the electromagnetic compatibility (EMC) with other radiocommunication systems. There are different methods to compute interference in geostationary (GEO) satellite systems including conventional methods using link budget equations and alternate methods such as increase in noise temperature. However, computing interference in low earth orbit (LEO) systems represents a different problem. Due to the special characteristics of this kind of orbits, the elevation angle at any site changes continuously over time, meaning a time dependent change of the propagation path length between an interfering transmitter and an interfered‐with receiver, and of the discrimination provided by the transmitting and/or the receiving antenna. Thus, conventional interference prediction methods developed for fixed links must be adapted to the case of LEO systems. To overcome this problem a mathematical model that characterizes the path length variations by an average value obtained from the probability density function of the varying distance between an interfering transmitter and an interfered‐ with receiver is proposed in this paper. This average path length enables the use of conventional link budget methods to reduce the computation time for the evaluation of interference in LEO satellite environments. Two practical examples show the possible applications of the proposed model. Copyright © 2003 John Wiley & Sons, Ltd.     

关于发展我国卫星移动通信的看法

本文主要介绍了我国卫星移动通信的发展现状及市场需求，针对当前国内外具体情况，提出了发展我国国内，国际卫星移动通信业务的合理建议。文章认为国内移动通信业务应采取先租星过渡，然后再建设自主运营，功能完备的卫星移动系统的方针；国外业务则采取慎重选择加入国际性系统的策略。     

Integrated global networks,tomorrow' communications today

This article presents an overview of the concept of a multiple purpose global satellite network. It identifies some of the main needs of telecommunication services today, and projects the potential of future demands. It also describes the great possibilities of economic expansion and mass participation in the growth and prosperity of a nation, if basic telecommunication services are accessible on a global scale. The study suggests that the rapid recovery of capital investments on universal satellite networks lies in developing regions through cost-effective service diversification.     

一种星地一体化路由设计的卫星IP网络

现有大部分支持IP的卫星系统只是提供一个连接地面路由器的物理通道,难以满足宽带接入、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,并从传输网络和路由结构两方面进行了描述.并针对星上资源紧张的现状,采用了一种地面路由星上交换的新设计思路.通过星上IP交换可实现大量终端间的单跳通信,一个可扩展的集中式IP路由结构可有效减少通过卫星的路由流量,使得通信效率提高的同时,能实现卫星网络与Internet的无缝兼容.     

同步轨道星机双基地三通道SAR地面运动目标指示算法

基于分数阶傅里叶变换(FrFT)和多通道杂波抑制干涉技术,提出一种同步轨道星机双基地SAR地面慢速运动目标检测和参数估计方法。首先根据同步轨道星机双基地SAR的特点,给出该模式下杂波对消的DPCA条件;然后从系统空间几何模型和回波信号入手,详细推导了动目标聚焦成像、杂波抑制、动目标检测和参数估计的原理,最后通过计算机仿真,验证了该文算法的有效性。     

基于STK的双层卫星星座设计及仿真

轨道与星座的设计是整个卫星通信系统设计的基础,合理的轨道设计与星座配置方案可以显著提高系统的整体性能。结合GEO卫星处理能力强,LEO卫星星地时延小的特点,以提供全球实时接入为目标,提出了一种由LEO卫星提供全球覆盖的GEO/LEO双层卫星网络星座设计方案。运用卫星覆盖带分析方法,确定由48颗LEO卫星完成全球覆盖。通过在STK仿真环境下进行计算机仿真验证,得到所设计的卫星星座可完成全天时全球覆盖。