卫星移动多媒体广播系统——日韩S-DMB

卫星直播系统和卫星移动多媒体广播系统是两项最重要的卫星广播技术。本文详细介绍了日本和韩国共同采用的卫星移动多媒体广播系统标准S-DMB，包括系统结构、关键技术和系统性能。也给出了中国发展卫星移动多媒体广播系统的技术建议。     

教育卫星数字化宽带网接收系统的设计与调试

中国教育卫星宽带多媒体传输网的运行,标志着我国卫星教育节目传输进入了Ku频段和宽带、多媒体、数字化时代.介绍了教育卫星数字化宽带网接收系统,以理论和实践相结合的方法,阐述了系统的组成、工程参数的计算、器材的选择以及系统的安装和调试.     

卫星宽带与多媒体业务

Internet和多媒体服务的快速增长为宽带卫星系统的发展提供了良好的机遇,本文分析了多媒体业务和卫星宽带的结合,讨论了多媒体宽带卫星的系统结构。     

数字广播电视技术与卫星应用(四)

第四讲卫星多媒体广播技术随着1992年世界无线电管理大会(WARC)对广播卫星业务(声音)波段进行了重新分配,面向车载高速移动终端、手持便携终端和固定接收终端的数字多媒体广播的需求与日俱增。到目前为止,已经有几个基于本国覆盖或者跨国覆盖的数字多媒体直播卫星系统开始运行。为了提供必要的技术和运行方面的参考信息,推动数字卫星多媒体直播系统的发展,指导为制定统一技术标准的实践活动,国际电联参考了ITU-R BS.774建议书和ITU-R BO.789建议书的有关细节,推出了数字多媒体直播系统技术标准(ITU-R BO.1130-4建议书)。这个标准中推荐了在1.4GHz～2.7GHz广播卫星业务频段上开展面向车载、便携和固定接收终端的五大数字卫星多媒体直播系统。这些系统包括：System A,System B,System D_S,System D_H和System E (System C专供地面多媒体广播)。下面简介其     

卫星-CATV-Internet宽带网

本文从介绍宽带多媒体网络的技术要求开始,进一步分析宽带卫星多媒体通信系统如何符合宽带多媒体网络的技术要求,卫星与Internet、卫星VSAT－CATV－Internet综合网络,最后介绍几种最新宽带卫星多媒体通信系统。     

卫星通信系列讲座之五宽带多媒体卫星通信

随着因特网的迅速发展,宽带多媒体卫星通信将在未来的通信市场中将占有极其重要的位置。本文简要阐述了宽带多媒体卫星系统的特点和关键技术,介绍了若干实用的宽带多媒体卫星系统。最后指出了其发展趋势。     

卫星—CATV—Internet宽带网

本从介绍宽带多媒体网络的技术要求开始,进一步分析宽带卫星多媒体通信系统如何符合宽带多媒体网络的技术要求,卫星与Internet、卫星VSAT-CATV-Internet综合网络,最后介绍几种最新宽带卫星多媒体通信系统。     

我国研制成功移动卫星多媒体应用系统

经过两年多努力,中国北京北方波 尔科技有限公司成功地研发出一套移动卫星多媒体应用系统,从而实现了中国小型化的无线宽带移动卫星应用领域零的突破。     

韩国全球首推卫星手机多媒体广播服务

2005年1月10日．以手机作为用户主要接收终端的韩国卫星数字多媒体广播系统开始试运营。据悉．这是全球第一个通过卫星实现移动多媒体广播服务的系统．该系统的运营标志着韩国正式步入了卫星数字多媒体广播时代。     

宽带卫星网络的发展现状

在卫星通信中,宽带卫星通信的主要目标是为多媒体和高数据速率的Internet应用提供一种无所不在的通信方式。对于时延要求低以及具有广播/组播性质的高速数据业务(如大容量数据传输、多媒体广播、因特网宽带接入、卫星远程应用、多媒体双向互动等业务)来说,卫星具有极大的优越性。宽带卫星网络也称下一代卫星通信网络。宽带卫星通信网具有地面覆盖面广、承载业务种类多、可快速部署、带宽利用率较高、星上交换快捷、可提供一体化网络等特点,能满足不同用户的业务需求。发展宽带卫星系统己成为当前通信的新热点之一。     

多媒体数据管理技术

在信息领域中,多媒体数据所占的比例越来越大,但多媒体数据的管理技术却远不及多媒体数据的处理技术成熟,这在一定程度上影响了多媒体技术的应用和推广。对文件系统,关系数据库系统等传统数据管理技术在管理多媒体数据方面的不足作了一些剖析,重点分析了多媒体数据库和超媒体这两种多媒体数据管理技术的各自的特点,意在探索多媒体应用系统中对信息资源的有效组织与访问的技术方法。     

Interactive multimedia satellite access communications

Recent advances in satellite technology are making possible the development of broadband satellite access (BSA) systems for two-way access to multimedia Internet services. This article provides an overview of BSA systems with an emphasis on resource management and interworking techniques to support IP-based multimedia services. The article draws on collaborative research performed over the past few years as part of the Broadband Satellite Communications Major Project of the Canadian Institute of Telecommunications Research. Some key innovations are described: combined free/demand assigned multiple access (CFDAMA) for dynamic satellite bandwidth allocation; an architecture for DiffServ provisioning over BSA systems; and a dynamic TCP Vegas protocol as a proxy service for split-TCP connections over BSA systems.     

Dimensioning and effective handling of signalling channels in a multimedia GEO Satellite platform

The deployment of highly powerful and sophisticated new-generation satellite broadband systems implies that a large portion of their bandwidth on the radio interface has to be devoted to conveying signalling information. Adequately dimensioning such a signalling bandwidth is an important design objective allowing the effective exploitation of the overall system resources and the cost-effective provision of a target quality of service to multimedia traffic. The performance of two basic techniques for accessing the signalling channels in a reference multimedia geostationary platform is investigated in this paper: random (slotted Aloha) and dedicated access. It is demonstrated here that dedicated access, despite rational appearances, allows 50% saving of signalling bandwidth while satisfying both the system and user constraints in terms of grade and quality of service respectively. This is accomplished by providing a statistical centralized connection admission control on Earth and an intelligent scheduling of the resource requests on board the satellite.     

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.     

IP路由协议在MF-TDMA卫星系统中适应性研究

MF-TDMA卫星通信系统可以实现卫星资源的有效利用和灵活组网,具有很大的潜在应用市场。同时,以IP技术为核心的宽带网络迅速发展,卫星通信作为一种广域网手段,实现对IP业务的接入,是其发展的必然趋势。主要研究了目前地面网络中常用的几种IP路由协议在MF-TDMA卫星通信系统中的适应性,利用OPNET网络仿真软件对MF-TDMA卫星通信系统进行仿真建模。通过对仿真结果的分析,给出了适合MF-TDMA卫星通信环境下的IP路由协议。     

Spread-spectrum techniques for the provision of packet access on the reverse link of next-generation broadband multimedia satellite systems

This paper will examine the potential performances of spread-spectrum-based access techniques via the interaction channel of an Internet protocol (IP)-based multimedia satellite system. In particular, a theoretical analysis of the spread-Aloha technique will be given for the case of forward error correction coded systems. Then, the performance of spread-Aloha access will be confirmed by simulation and compared with that of a conventional time-division multiple-access (TDMA)-based combined free/demand assignment multiple-access system. It appears that spread-Aloha-based techniques, although achieving a lower maximum throughput than the TDMA-based access scheme, may provide a better experience to the user due to the lower transmission latency. Finally, the prospect of a spread-spectrum-based access scheme combining Aloha and reservation mechanisms will be briefly overviewed.     

Designing the interworking of terrestrial and satellite IP-basednetworks

The design of effective interworking between a multimedia terrestrial backbone and a satellite access platform is a key issue for the development of a large-scale IP system designed for transporting multimedia applications with QoS guarantees. This article focuses on the design of a gateway station that acts as an interworking unit between the two segments of the systems. The guarantee of differentiated QoS for applications within the envisaged global IT system is achieved effectively by assuming that the IP IntServ model in the satellite access system is combined with a DiffServ fixed core network, in which the RSVP aggregation protocol is implemented. Thus, the design activity of the IWU mainly focuses on the following issues: seamless roaming between the two heterogeneous wireless and wired environments, efficient integration between the two IP service models (IntServ and DiffServ), and suitable mapping of terrestrial onto satellite bearer for traffic with different profiles and QoS requirements     

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.     

新一代卫星数据广播系统PCVSAT

ＰＣＶＳＡＴ卫星多媒体广播系统，是把ＰＣ机和ＶＳＡＴ合二为一的最新发展。本文介绍了ＰＣＶＳＡＴ中心主站和基本组构成，ＰＣＶＳＡＴ技术特点和ＰＣＶＳＡＴ在数据 多媒体领域的应用。     

Interactive channel for multimedia satellite networks

Multimedia, including Internet traffic, can currently be multiplexed within the DVB/MPEG-2 formats and delivered direct to home users. Traditionally a slow terrestrial telephone link between the user and Internet service provider is used to request data. A direct return channel system will facilitate users' high-bit-rate bidirectional communication via satellite. The return link could be used for the fast Internet access or large data exchanges that will be necessary in a multimedia world. The satellite system not only removes the need for wires but also increases transfer speeds. Satellite interactive terminals can establish network connections via satellite and a ground-based hub. The DVB/MPEG-2 format carries up to 45 Mb/s in the forward link, and a multifrequency time-division multiple access scheme allows up to 2 Mbit/s in the return direction. The return channel of the interactive channel for multimedia satellite networks underwent final standardization by ETSI in early 2000. This article reviews the system concept of a typical implementation. The key features of the return channel air interface, from transmission parameter to login procedure, are explained. In general, Internet packets are expected to be carried via DVB/MPEG-2 in the forward direction and via ATM in the return direction. The IP transportation techniques are described