GEO移动通信卫星星上处理交换技术

提出了一种新的星上处理交换技术方案,并对不同配置方式给出了性能分析和数值计算结果。分析表明,这种透明转发与星上处理相兼容的星上处理交换技术方案,只需要较少规模的星上处理单元,就能以较高的概率满足话音一跳通信的需求,相比于星上全处理降低了复杂度,相比于透明转发提高了通信质量,且适用于多种通信体制。     

卫星互联网光电混合交换技术综述

在激光链路与微波链路共存的空间环境下,卫星互联网光电混合交换的发展有助于推动空天地一体化的建设。针对卫星互联网业务的特点与传输需求,对电域交换技术和光域交换技术的现状进行调研和分析,总结现有交换技术在卫星互联网构建中的适用性。同时,根据分析结果,构建星上的端到端网络,并以此为基础完成星上光电混合架构的设计,主要包括接口、电域适配模块、光域适配模块、光电汇聚模块、光交换模块、分组交换模块与管理控制模块。     

大容量光电交换技术研究

高效灵活地利用已有带宽,充分、高效和灵活地调度和控制各种粒度的业务,保证业务的生存性是光交换网络亟需解决的技术问题。为此文章探讨了融合光通路数据单元（ODUk）/分组的新型交换机制、光纤/ODUk/分组混合交换机制。文章认为新的交换机制和多粒度交换结构是超大容量实现和构建的关键,业务多粒度生存性及协调机制、业务适配、带宽分配、管理和控制、损伤监测等是需要研究的重点问题。     

静止轨道移动通信卫星方兴未艾

卫星移动通信包括海事卫星通信、航空卫星通信和陆地卫星移动通信等，主要用于行进中的车、船、飞机等移动体和个人，以及山村、边远地区的固定用户。卫星移动通信覆盖区域广、不受地理障碍约束和用户运动限制的优势使光纤通信相形见绌，为此它已成为卫星通信发展的主要潮流之一。其趋势是高中低轨道卫星系统并存发展。区域性移动通信将主要采用静止轨道移动通信卫星，而全球性移动通信则主要采用中、低轨道移动通信卫星。　　一、开路先锋美国１９７６年２月发射了世界上第１颗静止轨道移动通信卫星──海事卫星Ｍａｒｉｓａｔ。后主要…     

基于保护资源的混合光交换网络

提出一种基于保护资源的混合光交换方案P_HyLABS。该方案利用光电路交换(OCS)网络中的保护资源(波长信道),构建光突发交换(OBS)网络层,与OCS工作光路组成的OCS网络层一起,组成OCS/OBS混合交换网络。仿真结果表明,由于将OCS传送的电路交换的优势与OBS传送的统计复用能力进行了较好的结合,与单一的OCS网络和OBS网络相比,P_HyLABS混合交换在保证数据高效传输的同时,可应对呈高突发性的数据传送,在多失效的网络环境下也能部分恢复数据传送。     

自适应混合光交换的研究

针对已有混合光交换的不足之处,提出了自适应混合光交换.这种光交换方式能根据网络业务的状态,自适应调整光交换方式,从而提高了链路利用率,降低了网络丢包率.同时讨论了自适应混合光交换的边缘节点、核心节点的结构及其各部分功能.     

光电混合自动目标识别技术研究

现代图像处理技术已发展成为包含计算机图像处理、光学图像处理及光电混合处理的综合性技术.光电混合自动目标识别技术是把光学处理和数字处理有机地结合起来,用光学处理高速完成成像变换和相关等运算量极大的任务,计算机灵活精确地完成控制分析和判断任务.     

Advanced satellite switching centre with on-board diagnostics

Design and operation of a satellite switching centre (SSC) with its own built-in diagnostics network are described. This SSC, designed for on-board applications, utilizes state-of-the-art technologies and techniques which have enhanced its performance significantly when compared to similar existing satellite switching centres. Additionally, unique features of this SSC are presented, specifically with respect to the built-in diagnostic circuit which fully describes the SSCs health without disturbance of traffic signals. Finally, system aspects of utilizing such satellite switching centres are addressed.     

基于宽带多媒体卫星网络的MAC协议

提出了一种基于MF-TDMA的宽带卫星MAC协议联合随机预约接入协议(CRRAP)。协议采用随机预约和捎带预约结合,按需分配和自由分配结合来实现的。仿真结果表明,相对于现有的方法,CRRAP减少了高信道负荷下的时延,提高了吞吐性能,并具有较高的信道利用率。     

Critical issues of onboard switching in DVB-S/RCS broadband satellite networks

The next generation of broadband satellite networks is challenged to accommodate multimedia services while concurrently integrating with terrestrial IP networks. With IP applications dominating the Internet, carrying IP traffic over the satellite has been under intensive study. Originally developed to bring digital television home through satellites, the DVB-S and DVB-RCS standards empower interactive satellite communications with economical standardized satellite terminals. Furthermore, onboard switching technology is increasingly gaining attention, due to optimized bandwidth usage, fully meshed network topology through one satellite hop, and quality of service guarantee. This article investigates the onboard switching technologies in DVB-S/DVB-RCS broadband satellite networks. Aside from the network system infrastructure and switch hardware architecture, the QoS mechanisms supported by the switch onboard the satellite are discussed in depth.     

Analysis of satellite on-board time-space-time switching networkswith multiple separated space switches

Advanced satellite on-board baseband switching processors have time-space-time (T-S-T) structures which are similar to the terrestrial switching networks (Sw-Nw). Generally, the satellite systems require higher reliability than ground equipment because of more severe environment and lack of repair. This paper proposes fault-tolerant satellite on-board T-S-T Sw-Nw with multiple separated space switches instead of a single spare switch. The authors analyze the mean time to unreliable operation (MTUO), as a performance and reliability index for the T-S-T systems with multiple separated space switches as well as conventional T-S-T systems. The MTUO varies depending on the threshold level of blocking-probability and the offered traffic. In general, T-S-T Sw-Nw with multiple space switches have better performance and reliability than those with the single space switch, and their performabilities are appreciably improved, especially for one additional spare space switch. This study can be extended to analyze the performance and reliability of entire satellite communication systems including the on-board baseband Sw-Nw, Rx interfaces, and Tx interfaces     

An advanced satellite communication system with on-board fast packet switching capabilities

This paper is focused on a satellite communication system having on-board fast packet switching capabilities. Different alternatives for the up-link access technique and for the architecture of the onboard switching fabric are considered. In particular an efficient time division multiple access technique with slots assigned on demand and a novel switching approach are proposed. Performances in terms of mean access delay and mean on-board switching delay are derived by analytical approaches and computer simulations.     

Advanced RF switching and on-board regeneration technologies for digital satellite communications

In this paper, functional blocks of a generic on-board processing payload are identified, and some key technology implementation issues for on-board RF and/or baseband switching, signal regeneration and processing are addressed. The design and performance characteristics of a microwave switch matrix and a 120 Mb/s coherent quadrature phase shift keying demodulator for satellite applications are presented. This hardware is realized with monolithic microwave integration technology. Significant performance improvement and reduction in size and weight, as well as enhanced subsystem reliability, have been demonstrated, making these technologies attractive for flexible communications satellite payload architectures of the future. Transmission analysis is performed to quantify link budget advantages that could be obtained by using on-board regeneration.     

A survey of future broadband multimedia satellite systems, issuesand trends

The demand for advanced information services is growing in terms of both the number of users and the services to be supported. Voice and low-rate data services are insufficient for users in a world where high-speed World Wide Web access is taken for granted. The trend is toward global information networks offering flexible multimedia information services to users on demand, anywhere, anytime. Potential services include video on demand, interactive video, fast Internet access, telemedicine, tele-education, and large file transfer. The need to support bandwidth-intensive multimedia services places new and challenging demands on satellite systems and networks. Flexibility, efficiency, mobility, and the ability to guarantee end-to-end quality of service are at a premium     

TCP协议在宽带多媒体卫星通信系统中的性能分析与增强（上）

作为承载多媒体业务的一种重要协议,TCP协议在宽带多媒体卫星通信（BSM,Broadband Satellite Multimedia）系统中的地位十分重要,然而TCP的内在机制（滑动窗口、慢启动、拥塞避免等）差,即而出现了许多针对卫星应用环境的TCP增强策略。由于篇幅关系,本文分为两个篇次：（上）主要分析TCP协议在卫星应用环境中的局限性并介绍目前常见的TCP性能增强方法,（下）主要关注TCP性能增强方法中最常用的性能增强代理（PEP,Performance Enhancement Proxy）的原理和性能,最后对目前TCPPEP中的行业标准“基于SCPS—TP协议的PEP”进行介绍.     

TCP协议在宽带多媒体卫星通信系统中的性能分析与增强（下）

由于目前大部分用户终端系统仍采用标准TCP协议,用户无法对TCP协议相关参数进行设置和调整,短期内新的改进协议也很难大规模应用于终端系统,因此针对TCP传输性能的优化只能在卫星段进行,最常见的是性能增强代理（PEP,Performance Enhancement Proxy）法,即通过增加硬件设备,将TCP端到端语义连接断开实现协议性能的增强。PEP的实现方案有很多,根据层次不同可分为基于链路层PEP、基于运输层PEP、基于应用层PEP。其中基于运输层PEP应用最为广泛,主要通过TCP进程之间的交互实现对TCP性能的增强;根据实现方式不同还可以分为TCP欺骗（TCP spoofing）和TCP分段（TCP splitting）两种。PEP的优势在于,终端系统感觉不到PEP的存在,也无需针对PEP做任何改动。