Globalstar低轨道移动卫星通信系统

简述了低轨道移动卫星通信系统的发展过程，着重介绍了美国ＬＱＳＳ公司１９９１年向美国联邦通信委员会提出的一种低轨道移动卫星通信系统－Ｇｏｌｂａｌｓｔａｒ系统。     

低轨道移动卫星通信系统（上）

低轨道移动卫星通信系统（上）刘宗祥ＬｏｗＥａｒｔｈＯｒｂｉｔＭｏｂｉｌｅＳａｔｅｌｌｉｔｅＣｏｍｍｕｎｉｃａｔｉｏｎＳｙｓｔｅｍｌｉｕｘｈｏｎｇｘｉａｎｇ１概述低轨道（ＬＥＯ）移动卫星通信系统是８０年代后期提出的一种新构思。其基本方法是利用数十颗低轨...     

低轨道卫星在军事通信上的应用

近几年来，低轨道卫星（ＬＥＯ）通信在军事上应用的研究有了长足进展，本文主要介绍ＬＥＯ卫星在美军全球栅格网中的作用，ＯＲＢＣＯＭＭ系统在美军通信中的应用和ＬＥＯ光通信系统的设计和应用。     

中,低轨道卫星通信：第三讲 窄带中,低轨道卫星通信系统

本文介绍一些典型窄带中，低轨道卫星通信系统，诸如Ｉｒｉｄｉｕｍ、Ｇｌｏｂａｌｓｔａｒ、Ｏｄｙｓｓｅｙ、ＩＮＭＡＲＳＡＴ－Ｐ、Ｅｌｌｉｐｓｏ等的基本结构与特征参数。     

低轨道移动卫星通信系统（下）

低轨道移动卫星通信系统（下）刘宗祥４俄罗斯的低轨道卫星群移动通信系统ＫＯＣＫＯＨ低轨道卫星群全球移动通信ＫＯＣＫＯＨ系统是前苏联国际创新联合公司提出的，其基本任务是为全球提供移动通信业务。另外，该系统还具有粗略的导航定位功能，对移动站的定位精度优于１...     

大有作为的低轨道卫星通信

大有作为的低轨道卫星通信王令朝众所周知，７０年代初出现的卫星通信是从低轨道卫星开始的，但在过去２０多年中一直都没有受到很好的重视，它的发展远不及大功率高轨道卫星。然而，随着高集成化半导体技术、微处理机技术的迅速发展和移动通信需求的急剧增长，低轨道卫星...     

低轨道卫星通信系统综述

概述了低轨道卫星通信系统的发展及特点；对低轨道卫星系统的组成及使用范围给予了较详细的介绍，并给出了工作方式框图及系统框图．     

低轨道卫星通信的发展

低轨道卫星通信是近年来发展起来的一项通信系统。是使用多颗在低轨道上运行的卫星的通信系统。本文介绍了其特点，并对几种目前正在建设中的卫星通信系统进行了介绍     

全球星低轨移动卫星系统及其应用

低轨移动卫星通信的发展给实现通信的全球化和个人化带来了更多的机会和选择。不同系统的不同设计思路带来了系统之间的差异,同时也决定了其在通信市场中的位置。本文介绍全球星低轨移动卫星通信系统的设计思想、技术体系和终端设备以及目前的实施情况。     

LEO卫星通信系统覆盖时间和切换次数分析

针对近地轨道(LEO)卫星移动通信系统,该文提出一种分析不同用户覆盖时间及切换次数的方法。在充分考虑地面用户随机分布特性的基础上,建立了卫星和波束对随机用户的覆盖时间统计模型,推导了星间切换及波束间切换平均次数下限值的计算方法。最后通过铱星通信系统模型(包括铱星星座参数,地面站参数和阵列天线波束模型)对该方法进行了仿真分析,结果显示该方法能很好地近似用户随机覆盖时间统计特性及平均切换次数的下限值。     

A Novel Probability-Based Handoff Strategy for Multimedia LEO Satellite Communications

A novel bandwidth allocation strategy and a connection admission control technique arc proposed to improve the utilization of network resource and provide the network with better quality of service （QoS） guarantees in multimedia low earth orbit （LEO） satellite networks. Our connection admission control scheme, we call the probability based dynamic channel reservation strategy （PDR）, dynamically reserves bandwidth for real-time services based on their handoff probability. And the reserved bandwidth for real-time handoff connection can also be used by new connections under a certain probability determined by the mobility characteristics and bandwidth usage of the system. Simulation results show that our scheme not only lowers the call dropping probability （CDP） for Class I real-time service but also maintains the call blocking probability （CBP） to certain degree. Consequently, the scheme can offer very low CDP for rcal-time connections while keeping resource utilization high.     

农村通信中无线技术的比较分析

本文分别介绍了农村通信中所采用的GSM、PMP和STAR无线技术及模型,用一般假设和特定假设进行了实例研究,分析了结果并加以总结。     

卫星通信的发展现状和趋势

随着通信的全球化发展，通信网络逐步向立体式综合化演变，卫星通信在其中扮演的角也越来越重要。     

Performance of Low Earth Orbit Satellite Systems with Coding

The effect of block, convolutional and Turbo coding on the probability of error and the capacity are investigated for CDMA Low Earth Orbit (LEO) Satellite systems. The model employed assumes a contaminated Gaussian traffic model to be more compatible with different population areas. The conventional Gaussian distribution can be considered as a special case.     

Architectural Decisions for Communications Satellite Constellations to Maintain Profitability While Serving Uncovered and Underserved Communities

The rise of the commercial space industry has resulted in the development of mega-constellations that promise to provide global broadband. These constellations capitalize on advancements in technology, improved modeling capabilities, and reductions in launch cost. One of the significant open questions is whether these constellations will significantly increase access for uncovered and underserved communities, in addition to serving existing markets. This paper analyzes which constellation characteristics provide the best global coverage at the lowest operational cost. First, we present the demand model that assesses the number of under-served and uncovered users in a given region. Then, we present a genetic algorithm used to identify potential constellations. Finally, we conclude by identifying which characteristics are the most promising for broadband constellations, as well as predictions of how the market will develop in the coming years. Our analysis has found that geostationary (GEO) and medium Earth orbit (MEO) satellite constellations have the highest likelihood of profitability. LEO networks are on average 27% more expensive, but if designed wisely, they can be competitive. Our work shows that there are diminishing returns with large constellations, and that it is more cost effective to have a small number of highly capable satellites, rather than many low complexity satellites. Key technologies like high frequency bands and miniaturization of components can lead to further cost reductions and increase the competitiveness of LEO constellations.     

一种基于低轨卫星通信的定时同步研究

定时恢复是数字接收机中的关键技术,基于某特定LEO低轨卫星通信系统应用,重点研究了异步时钟采样恢复法的工作原理,提出了一种改进的Gardner定时误差检测算法,给出了整个定时环路的具体实现方案,并针对其性能进行了分析。仿真结果表明,在大多普勒加速度的卫星信道环境下,该方案能够满足系统设计的要求,且实现结构简单、优化,可大幅降低算法复杂度,在较高信噪比的情况下,具有更加优化的性能。     

Advanced Communications Satellite Systems

Demand for in-orbit capacity through the use of satellite systems will continue throughout the next two decades. The potential of the 30/20 GHz frequency band for fixed satellite services will be exploited. However, many technology questions must be answered if the band is to be used commercially because of the high rain fades that can occur at these high frequencies. NASA has conducted a technology development program in high gain antenna and on-board switching and processing systems which can be combined such that cost competitive services are possible at acceptable rain outage percentages. Other supporting technologies have also been pursued including transmitters, both tube type and solid state, and low noise receivers. The critical technologies have been combined into an experimental satellite payload; an experimental flight is planned to verify these technologies and enable development of operational systems. Implementation of such systems would be by commercial carriers and could occur in the early 1990's, depending on the demand for additional or bit capacity. The high capacity systems that can be made possible through the use of the 30/20 GHz band and the employment of frequency reuse technology will contribute to the continued downward trend in circuit costs and may allow new and innovative satellite services.     

LEO卫星通信中基于服务质量的综合加权接入策略

该文首先建立了LEO卫星全球业务密度,提出4种卫星接入和卫星间切换策略,并对LEO卫星通信的新呼叫阻塞概率和强制中断概率在这4种策略下的性能进行了仿真分析, 然后在简单综合加权策略的基础上,根据全球各个地区不同的地形、地表以及通信业务的特点,提出了基于服务质量的综合加权策略。仿真结果表明根据实际地理情况采用改进的综合加权策略,新呼叫阻塞率和切换失败率得到了较大的改善。