DVB-RCS2卫星交互网的调制编码技术

DVB-RCS2规范在调制编码技术方面较DVB-RCS作出了重要改进,分别研究了前向链路的自适应编码调制方式,以及回传链路突发所采用的两种传输模式,即Turbo码线性调制模式和卷积码连续相位调制模式。通过对其实现方式和关键参数的分析,探讨了DVB-RCS2体制的灵活性和高效性。     

第二代卫星交互系统浅析

基于新一代卫星回传系统的市场需求,ETSI于2011年5月、8月分别公布了DVB-RCS2-Part1和DVB-RCS2-Part2标准。分析了新标准中的部分关键技术,着重介绍了DVB-RCS2相对于DVB-RCS的改进以及增加的前向网控信令,在此基础上进一步讨论了后向链路的变化,并探讨了中国国建立卫星回传系统标准的可行性。     

第二代卫星交互系统解读

基于新一代卫星回传系统的市场需求,ETSI于11年5月、8月分别公布了DVB-RCS2-Part1和DVB-RCS2-Part2标准。文中分析了新标准中的部分关键技术,着重介绍了DVB-RCS2相对于DVB-RCS的改进以及增加的前向网控信令,在此基础上进一步讨论了后向链路的变化,并探讨了我国建立自己的卫星回传系统标准的可行性。     

DVB-RCS突发信号符号同步的近似常模算法研究

分析了DVB-RCS卫星网络中子站与主站进行交互的通信结构特点,得到了获取回传链路突发信号参数的方法。重点对相应突发信号的符号常模定时估计算法进行了推导和简化,结合系统结构特点设计了一种基于数据辅助的的近似常模算法。该算法复杂度低、达到要求定时精度使用符号数少。与其他前向型定时估计算法比较,理论分析和Monte Carlo仿真结果显示该算法在实际系统的突发参数下,均方根误差均更接近MCRB。     

AmerHis宽带多媒体卫星通信系统的空中接口

AmerHis系统上行链路采用DVB-RCS（Digital Video Broad-casting-Return Channel Satellite）标准,下行链路采用DVB-S（Digital Video Broadcasting via Satellite）标准。本文按层次介绍了该系统上行链路空中接口和下行链路空中接口的相关技术。     

DVB-RCS前向信号检测与分析

宽带化,交互式应用成为通信服务的发展趋势,针对传统DVB-S系统在卫星宽带应用中的不足,BTSI制定了DVB-RCS标准,通过DVB-RCS系统构建卫星交互网络,满足了市场的需求.文章通过对DVB-RCS协议的分析,阐明了交互式网络的系统结构和信令的组成,分析了网络接入的流程以及在此过程中信令的作用,最后对DVB-RCS前向信号的检测和信令解析提出了可行的方法.     

DVB-RCS系统网络管理的分析与研究

简要介绍DVB-RCS卫星通信系统,着重讨论了网络管理在DVB-RCS系统中的作用,分析了卫星通信系统高效动态带宽资源分配、提高链路服务质量以及简化小站管理等方面的技术问题,以及网络管理系统在通信系统带宽利用率、服务质量保障等方面性能改善上的特殊贡献。     

基于DVB-RCS的VSAT宽带卫星通信技术与应用

介绍了VSAT数据网原理、卫星通信系统宽带化的发展趋势及DVB-RCS开放标准。通过介绍基于DVB-RCS的VSAT宽带卫星通信系统在工程中的应用实例,其中包括系统业务与特点,以及各子系统的基本配置等,可以得出,随着网络和业务的宽带化,VSAT卫星通信系统正在从传统的窄带向宽带系统转变。在现有技术中,基于DVB-RCS...     

DVB-RCS协议研究

DVB-RCS通信系统是基于交互式应用的卫星通信系统,目前已受到业界的广泛关注。首先介绍了DVB-RCS系统的模型和协议结构,然后分别对前向信道和反向信道协议进行了分析,最后对所存在的问题进行了说明。     

VSAT卫星通信系统在海上平台的应用研究

针对海上油田特殊的地理位置,为更好满足中海油油田生产作业通信需求,中海油信息科技有限公司构建了新一代VSAT卫星通信系统。SkyEdge II卫星通信系统基于DVB-S2(TDM)/DVB-RCS(MF-TDMA)的宽带多媒体IP通信平台,实现卫星频率资源的高效利用、主站端站的统一管理、多种多样的业务组网。     

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     

Electric-field intrabody communication channel modeling with finite-element method

Electric-field intrabody communication (EF-IBC) is a promising new scheme for the data exchange among wearable biomedical sensors. It uses the body as the signal transmission media. Compared with existing body area network (BAN) schemes, EF-IBC can achieve higher data rate with less transmission power. Until now, the detailed EF-IBC channel mechanism is not well understood. In this work, finite-element method (FEM) is utilized for the first time to investigate the EF-IBC channel. A circuit-coupled FEM model is established for the EF-IBC channel. The FEM model is extensively verified by experimental measurements. The new physical model enables the revelation of characteristics and effects of different components in the EF-IBC channel. The FEM investigation finds that the capacitive return path is critical to the characteristics of the EF-IBC channel. Parameters of the capacitive return path are quantitatively measured. The investigation also finds that the body plays an important role to the return path capacitance. The forward body path can be well modeled by a cascade of π-shaped circuits. Based on the FEM model of the EF-IBC channel, a simplified circuit model is derived to provide an efficient tool for the transceiver design.     

Computer Communication Via Satellites--A Queueing Model

The last few years have witnessed the intensive growth of computer communication networks. The need for nationwide and multination computer communication systems brought about the development of packet-switching networks such as the ARPANET. In this paper we examine a model for computer-to-computer communication via a satellite link. In each network, a single node, the satellite communication concentrator (SCC), manages the flow of information between the terminals in the network and the satellite link. The SCC buffers messages from the terminals and retransmits them over the satellite channel. Buffer space claimed by a message is made free only after the SCC receives an acknowledgment from the receiving network; transmission errors cause the buffer to retransmit the message. The statistical behavior of such a system is considered.     

HFC网络回传通道关键点及信号混合的探讨

讨论了有线电视宽带综合信息HFC网络中回传通道关键点的设置与调试,以及回传信号在前端或分前端中CMTS头端机上的混合接入等问题.着重研究和探讨了反向链路中关键点的电平调整范围、CMTS在前端或分前端的连接方法及回传信号传输需要考虑的一些问题.     

Dynamic uplink frame optimization with adaptive coding and modulation in DVB‐RCS2 satellite networks

In the current generation of satellite networks, modulation and coding schemes can be dynamically changed in real‐time to face different link conditions. Therefore, the link budget is not anymore required to be computed under the worst case, with relevant advantages in terms of efficiency. The new digital video broadcasting‐return channel via satellite 2 standard extends the dynamic modulation and coding to the return link: by using different modulation and coding schemes within the uplink frame, the terminals experiencing good link conditions transmit at very high bitrates, whereas the terminals experiencing fade events transmit at lower bitrates. This paper addresses the problem of optimizing the uplink frame modulation and coding schemes based on the current link conditions experienced by the terminals and on their transmission capacity requirements. The problem is formulated as an Integer Program and an efficient Linear Program approximation is proposed. Simulation results validate the proposed approach. Copyright © 2013 John Wiley & Sons, Ltd.     

直升机卫星通信系统信道模拟与通信实现

针对直升机卫星通信系统中直升机旋翼对通信信道造成的周期性衰落问题,采用射频收发器AD9361模拟了信道周期性衰落模型,基于此模型在现场可编程门阵列(Field Programmable Gate Array,FPGA)上优化并实现了缝隙检测算法。根据信道衰落模型和缝隙检测算法及数据链路速率和带宽的要求,提出了一套直升机卫星通信系统可靠通信方案,即前向链路采用重发和分集接收及短码LDPC编码技术,返向链路根据前向链路缝隙检测的结果在无遮挡缝隙采用突发通信和长码低密度奇偶校验(Low Density Parity Check,LDPC)编码技术,实现可靠通信。系统测试结果表明,该方案不受直升机机型限制,系统可在40%遮挡率下实现前向链路25.6 kb/s和返向链路4 Mb/s速率下的可靠通信。     

双向网改造中回传系统设计需要注意的问题

为了参与市场竞争,必须对有线电视网络进行双向改造,而网络的双向、互动、高效主要体现在回传系统的设计和建设上,为此根据实践经验,提出双向网改中回传系统设计需要注意的几个问题,只有在这几个方面精心设计、严格把关,才能保证回传通道的性能和质量。     

一种双向链路频谱重叠共享频带的卫星通信系统

提出一种基于C,Ku,Ka频段透明转发器的双向链路频谱重叠共享频带的TDM/FDMA星型网卫星通信系统方案,小站至中心站的反向链路采用FDMA接入方式,中心站至各个小站的前向链路采用TDM广播方式。理论和仿真分析结果表明:该系统的频带效率比常规TDM/FDMA系统提高了1倍,而链路的传输性能仍可以达到实用要求。     

卫星通信系统多优先级信道预留分配策略

随着通信系统的不断发展,对融合地面系统的天地一体化网络的研究越来越多,而卫星通信系统中,由于卫星高速移动等特性,不可避免需要对呼叫的接入切换进行研究。针对天地一体化信息网络需要支持多场景多业务情况下的通信需求,考虑不同呼叫优先级不同,对多优先级的多种呼叫业务进行考虑。根据信道预留的思想,对不同优先级接入与切换呼叫设定不同的可用信道数,优先级越高的呼叫,为其留更多的可用信道以确保其接入信道成功。同时,由于动态信道预留较固定信道预留能够更好地利用信道资源,最终考虑多优先级下的动态信道预留策略。对多优先级动态信道预留与多优先级固定信道预留策略进行仿真验证,发现动态预留方案得到的系统服务质量更好。对于单一策略,发现优先级越高的用户接入与切换呼叫接入信道失败率更低。