卫星DVB在因特网接入业务中的应用

介绍了卫星DVB接入因特网的应用模式，采用卫星回传信道时的系统组成以及需要解决的问题，并展望了其应用前景。     

DVB—S简介（七）

3.4 R-S(204,188,T=8)码的编码和解码 R-S码是由 Reed和Solomon于1960年提出来的。DVB—S中的R-S码生成多项式G(X)=(X λ~1),其中λ为本原元,λ=02H。域生成多项式P(X)=X~8 X~4 X~3 X~2 1。最小码距17字节。它可纠8个字节长的随机性或突发性错误。 DVB—S中的R-S(204、188、T=8)码在GF     

基于DVB-S的IP数据广播

卫星通信具有覆盖区域广、通信容量大、广播特性以及通信费用不受地理区域影响特点 ,使其在广域通信得到空前的发展。特别是其广播特性 ,在数据广播业务上较其他通信方式有无可比拟的优势。近几年来 ,由于计算机的广泛应用和普及 ,数据和多媒体业务平均年增长率达２５ %～４０% ,远高于电话业务。特别是ＩＰ业务 ,其规模和业务量６～１２个月左右就翻一番。多媒体业务包括文字、数据、图形、图像、视像和声音等多种媒体 ,其传输速率从２ｋｂｉｔ／ｓ到十几Ｍｂｉｔ／ｓ,其交互类型有对称型、非对称型和单向型之分。其中非对称型和单向型非常…     

DVB—S简介（九）

下面我们还是用表3.6.3产生的3/4收缩卷积码来进行Viterbi译码,表3.6.2中共108bit码元,卫星信道在QPSK调制时误码率pe=10~(-1)～10~(-2),在108码元中选择8bit码元位置,使该码元处产生误码。用随机数方法产生8bit码元位置,分别在3,17,38,54,62,66,90,103。Pe=8/108=7.4×10~(-2)(上述3,17,……103是用随机办法产生的一次结果,下一次再用随机数方法产生又会是另外的     

DVB—S简介（十三）

6.2 相位模糊和解决办法 6.2.1 四次方律锁相环的相位模糊 由锁相环基本原理知道,如果斜率为正,在φ_i处是锁相环的平衡点,那么4φ=2nπ+φ_i,上各点都是锁定的,其中φ_i为剩余相差,当环路增益足够高,假设剩余相差可以忽略不计,那么4φ=2nπ,说明在0、π/2、π、3π/2这四个点都是稳定的平衡点。这样锁相环输出的相干载波有四种可能初相角cos ω_ct,     

DVB—S简介（三）

3.2.2 线性分组码的编码、检错和纠错 (1)线性分组码的编码 线性分组码是把信源编码器送出的二进制序列分段处理。假设信源编码器输出的二进制序列是——C_1C_2…C_kC_(k 1)…C_(m-k)…C_m…每次线性组码从     

通过卫星的IP: "DVB-RCS"数字视频广播--经由卫星的回传信道

目前 ,Ｎｅｗｔｅｃ公司正在开发一个完整的商业化ＤＶＢ -ＲＣＳ网络 ,该开发工作是与Ｓｐａｃｅｂｒｉｄｇｅ公司和ＡｌｃａｔｅｌＢｅｌｌ公司共同合作进行的。本文阐述了开放的ＤＶＢ -ＲＣＳ标准的主要目标应用 ,网络的主要输入是商业模型和服务水平协议(ＳＬＡ) ,它们明显是与计费和委托机制相关的。同时还谈到了为补偿卫星时延的ＴＣＰ协议增强代理 (ＰＥＰ)的使用。最后介绍了网络元素的细节、网络中心站以及卫星交互式终端。1　ＤＶＢ -ＲＣＳ :“开放的标准”ＤＶＢ在世界范围内的成功主要归功于它包含一套开放的标准 ,这些标准在…     

DVB—S信道解码技术研究与实现

本介绍了DVB-S信道解码的过程,并提出一个DVB-S信道解码（即DVB-S前端机）的实现方案,介绍了其硬件和软件的组成与实现过程。     

DVB—S简介（十二）

6 载波和位时钟的恢复、QPSK正交相干解调——系统方案描述 本节的核心是围绕着QPSK如何进行解调以重新得到的I、Q信号。对QPSK信号通常采取正交相干解调。要实现正交相干解调就要产生一个与原载波同频同相的载波(或称相干载波),该过程称为载波恢     

DVB—C系统部分功能的仿真研究

本介绍DVB－C系统的组成，并作为相应的讨论，在硬件仿真部分，讨论了同步头反转和随机化块的仿真中需要注意的问题，然后对GDF和VHD两种方法进行比较，最后得出仿真结论。     

利用GEO卫星接入因特网

阐述了利用对地静止轨道GEO卫星链路接入因特网的特点,介绍了目前为解决卫星链路时延长带来的问题所采用的一些方法。     

An Integrated Medium Access Control and Traffic Management Architecture for DVB-RCS SkyplexNet Satellite Systems

The growing development of standard Internet services and the emerging exploitation of several broadband multimedia contents disclosing in the last years, significantly promoted scenarios where Satellite Networks can play key roles. Several satellite networks are currently implemented according to the Digital Video Broadcasting-Return Channel via Satellite (DVB-RCS) standard, assuming to operate with a transparent satellite and an hub-centric (star) network topology. The present work addresses the SkyplexNet (SKN) system: an advanced Broadband Satellite Network for meshed connectivity developed by Alenia Spazio, within the framework of ESA Artes 3 – Line 1 Program, according to the DVB-RCS standard with duly extensions for the on-Board multiplexing capability of the Skyplex Units currently embarked on HotBird VI and W3A satellites. In this paper an architecture design study aiming at integrating the Medium Access Control (MAC) and Traffic Management (TM) functionality in a DVB-RCS like Network is presented. The envisaged Traffic Management schemes shall enable the SKN System to guarantee an adequate support of various Quality of Service (QoS) requirements and their application according to pre-defined Traffic Profiles established at connection set up phase with the support of physical medium access management functions. The functional architectures studied for the SKN Inter-Working Layer, from Internet protocols to SkyplexNet ones, and the SKN MAC layer have been also analysed on the interoperability level of these layers in order to deploy such functions as SKN connection mapping, packet scheduling and Bandwidth on Demand (BoD) policies. In this paper two different schemes of Traffic Management and MAC are presented reporting a detailed analysis of advantages and drawbacks of both approaches to be taken into account for future SkyplexNet system implementations. Fabrizio Di Cola is a Network and System Engineer of the Telecommunication Mission Unit of Alenia Spazio company (Italy). He received the M.S. degree in Telecommunication Engineering from University of Rome “La Sapienza” in 1998 and he is in Alenia Spazio since 2000. He is currently involved in the design and deployment of the Ground Segment of EuroSkyWay and SkyplexNet satellite systems as responsible for the Satellite User terminals Design and Development. He also contributes to System Engineering in the framework of several ESA and EC projects. From 1999 up to 2000, he worked as Researcher in the University of Bradford (Bradford, UK), Telecommunication Research Centre, within the “Satellite Mobile Group”. His activity focused on several aspects of the Mobility Management within telecommunications network integrating satellite and terrestrial networks. Emiliano Micaloni was born in Rome, Italy, in 1977. He is a Junior Telecommunication System Engineer involved since 2003 in a collaboration between University of Rome “La Sapienza” and the TLC Mission Unit of Alenia Spazio company (Italy). He received his Master Degree in Electronic Engineering from the University of Rome “La Sapienza”, Italy, in 2002, defending a thesis on Connection and Congestion Control for Geostationary Satellite Networks. Currently his area of interest concerns the Medium Access Control in the SkyplexNet Satellite Network, also contributing at the development activities for the SkyplexNet Satellite Terminals. In 2002–03 he collaborated with the “Computer Science and Systems” Department of “La Sapienza“ implementing solutions for Traffic Management and Quality of Service in Satellite Networks. All his activities are carried out in the framework of different ESA and EU IST projects. Luigi Secondiani received his M.S. degree in Telecommunication Engineering from University of Rome “La Sapienza” in 1997. From 1998 to 1999 he received a post-degree grant issued by the “Infocom” Department of the University of Rome “La Sapienza” in the frame of the ACTS 4th framework programme. Since December 1999 he works as a Network Engineer in Alenia Spazio-TLC Mission Unit, and he is currently involved in Alenia's activities on EC, ESA and NATO programmes. His main research interests mainly lie on interworking between Next Generation Satellite Systems (NGSS) and IP networks, with particular emphasis on network architectures, terminal's architectures and routing issues. Giuseppe Tomasicchio is a Senior Telecommunication System Engineer of the TLC Mission Unit of Alenia Spazio company (Italy). He received his degree in 1989 from University of Bari (Italy) in the Artificial Intelligence field. He received a Post-degree Diploma on Technologies of Educational Communication in 1991 and a Post-degree Engineering Specialisation Diploma in Signal Processing in 1994 from University of Bari. Currently he is responsible of the Ground System Design of EuroSkyWay/SkyplexNet satellite systems and of the Network Operations and Service Centres engineering in satellite networks devoted to multimedia applications in the framework of different ESA and EC projects. In 1997–98 he was responsible at CERN (Geneva, Switzerland) of the Data Acquisition System involving the readout, calibration, event display and the networking setup tasks of high energy physics experiments. From 1994 to 1998 he was at INFN (Italian Institute for Nuclear Physics) as researcher. In 1994 he was an IS-specialist in the Italian Government data processing centre and collaborated with the Government Seismic Service for GIS processing. He worked in 1991–92 as a fellow of DIGITAL Corporation for a join research activity at INFN in the field of Image processing and Pattern recognition applied to raw-data images produced from detectors in high energy physics experiments at CERN. He is author of several scientific and engineering papers.     

利用卫星通信技术实现Internet接入

随着Internet的快速发展,利用卫星的宽带IP多媒体广播解决Internet带宽的瓶颈问题,通过卫星进行多媒体广播的宽带IP系统逐渐引起了人们的重视,宽带IP系统提供的多媒体(音频、视频、数据等)信息和高速In-ternet接入等服务已经在商业运营中取得一定成效。目前,已有网络使用卫星通信的VSAT技术,发挥其非对称特点,即上行检     

基于DVB-RCS和WiMAX的卫星宽带无线接入体系设计

卫星宽带通信已成为目前研究的热点.现有的DVB-RCS卫星无线接入标准以物理层规范为主,尚未构成完整的卫星宽带无线接人体系.本文基于DVB-RCS技术,针对卫星宽带无线接入的需求和特点,结合地面WiMAX宽带无线接入技术,给出了卫星宽带无线接人体系的功能架构设计,并具体分析了各主要功能的设计与实现方法.     

基于混沌预测的宽带DVB-RCS卫星接入信道动态分配方案研究

该文概述了基于卫星数字视频广播-反向信道系统(DVB-RCS)标准的宽带卫星通信网的特点,并重点研究了多址接入信道的动态分配策略,在利用混沌理论对网络中的自相似业务流量进行预测的基础上,提出了一种新型混合按需分配多址接入方案。该文还利用OPNET软件建立了仿真系统,用于比较不同方案的性能。仿真结果表明,在高信道负载以及网络中业务流具有较高自相似程度的条件下,该文所提出方案具有更优越的性能。     

Internet卫星接入技术

为高速接入Internet,宽带接入技术应运而生,本文对目前流行的几种Internet宽带接入方式进行了简要比较,并重点介绍了Internet的卫星宽带接入技术及其应用领域和发展前景。     

Suitability of DAMA and Contention-Based Satellite Access Schemes for TCP Traffic in Mobile DVB-RCS

The problem of optimizing access and bandwidth sharing among transmission control protocol (TCP) connections in the mobile digital video broadcasting return channel via satellite (DVB-RCS) is tackled in this paper. After sketching the general system architecture, we explicitly deal with the dynamic assignment of bandwidth to TCP connections on the return link, which is accomplished by a network control center (NCC) placed onboard the satellite. Mobile users access the satellite in multifrequency time-division multiple access (MF-TDMA), whereas they receive data from the NCC in time-division multiplexing (TDM). Two different techniques, based on deterministic and random access, are compared in terms of bandwidth usage and average completion time per connection, when the mobile user acts as both server and client. In the server case, to increase the TCP throughput, both packet-level forward error correction (FEC) on data sent by mobile users and a duplicated and delayed acknowledgment technique for TCP acknowledgment traffic from the NCC to the mobile users are applied. An analysis of the packet losses and a simulation campaign of file transfers by employing a realistic channel model has been carried out. The results of the analysis show the convenience of adopting a technique, in addition to the optimal data redundancy in different cases, such as the server or client role of users, their willingness to pay, the file size, and the environment type.     

基于卫星的宽带Internet接入

为了体现宽带网络建设的完善性与先进性,综合阐述了现有卫星通信技术,通过对宽带卫星通信特点的分析,将其与光纤通信进行了对比,阐述了宽带卫星通信的必要性,设计了实际场景下的宽带卫星通信方式,并作为企业或政府的参考。     

利用卫星系统实现宽带因特网接入

利用现有的卫星数据视频广播 (DVB)标准和协议建立宽带因特网系统 (BIS)是目前卫星直播的主要业务之一。这样能够提供快速的 Web浏览、文件下载、实时数据更新和其他广播业务。这些服务使得卫星广播系统同时快速地传输文件、音频和视频信息成为可能。宽带因特网是一个未来的网络 ,能够同目前标准的卫星网络进行无缝连接 ,计划宽带因特网将在未来的发展中与有线电视、x DSL、无线系统、光纤和数字地面前端系统进行无缝集成。1卫星数据广播系统世界最新的通信技术一直在致力于开发卫星数据广播系统与现有的卫星网络进行无缝连接 ,使用 DV…     

An Overview of Satellite Access Networks

This paper provides an overview of satellite technologies that can be used to deliver IP-based services. A snapshot of the current and future satellite capability is given, followed by an appraisal of architectures and worked examples of satellite links used for IP access. The last section explores the key issue of integration from the viewpoints of user traffic and network management.