DVB-RCS卫星系统无线资源管理体系架构

基于DVB-RCS（Digital Video Broadcasting and Return Channel via Satellite）卫星无线接入技术标准的宽带卫星通信技术已成为目前研究的热点。现有的DVB-RCS标准以物理层规范为主,其中的无线资源管理技术等重要的宽带无线接入功能的定义缺乏系统性,缺少具有可实现性的无线资源管理体系的描述,尚不能构成一个较完整的卫星宽带无线接入体系结构。针对宽带卫星通信的无线资源管理技术,提出一种基于DVB-RCS的宽带卫星无线资源管理体系结构,给出其主要功能模块设计及关键技术分析,并就可能的实现方法和进一步研究方向进行讨论。     

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。     

结合事件触发的层次型分布式DVB-RCS网络管理

针对卫星通信网络管理研究集中在宏观的管理策略和管理协议而不是针对具体管理任务这一问题,结合DvB-RCS卫星通信网的特点,提出了结合事件触发的主被动网络管理机制.该管理机制分为事件触发机制、主动报告机制和被动轮询机制三部分,为DVB-RCS卫星通信网络管理系统(NMS)不同管理模块所涉及的具体网络管理任务提供了思路.同...     

Transport Layer Optimization for Cloud Computing Applications via Satellite： TCP Noordwijk＋

Cloud computing can significantly improve efficiency in Internet utilization and data management.Several cloud applications（file sharing,backup,data up/download etc.） imply transfers of large amount of data without real-time requirements.In several use-cases cloud-computing solutions reduce operational costs and guarantee target QoS.These solutions become critical when satellite systems are utilized,since resources are limited,network latency is huge and bandwidth costs are high.Using satellite capacity for cloud-computing bulk traffic,keeping acceptable performance of interactive applications,is very important and can limit the connectivity costs.This goal can be achieved installing in the Set Top Box（STB） a proxy agent,to differentiate traffic and assign bandwidth according to priority,leaving spare capacity to bulk cloud computing traffic.This aim is typically reached using a specific QoS architecture,adding functional blocks at network or lower layers.We propose to manage such a process at transport layer only.The endpoint proxy implements a new transport protocol called TCP Noordwijk＋,introducing a flow control differentiation capability.The proxy includes TPCN＋ which efficiently transfers low-priority bulk data and handles interactive data,keeping a high degree of friendliness.The outcomes of Ns-2simulations confirm applicability and good performance of the proposed solution.     

A Cross-Layer Approach to Enhance QoS for Multimedia Applications Over Satellite

The need for on-demand QoS support for communications over satellite is of primary importance for distributed multimedia applications. This is particularly true for the return link which is often a bottleneck due to the large set of end-users accessing a very limited uplink resource. Facing this need, Demand Assignment Multiple Access (DAMA) is a classical technique that allows satellite operators to offer various types of services, while managing the resources of the satellite system efficiently. Tackling the quality degradation and delay accumulation issues that can result from the use of these techniques, this paper proposes an instantiation of the Application Layer Framing (ALF) approach, using a cross-layer interpreter (xQoS-Interpreter). The information provided by this interpreter is used to manage the resource provided to a terminal by the satellite system in order to improve the quality of multimedia presentations from the end user’s point of view. Several experiments are carried out for different loads on the return link. Their impact on QoS is measured through different application as well as network level metrics.

卫星数字电视直播的发展现状及思考

介绍了我国卫星数字电视直播发展的现状,通过和国外发达国家目前的发展情况相比较,提出了一些适合我国国情的卫星数字电视直播发展思路,包括完善标准体系,建立宽带多媒体直播卫星系统等.     

基于频率插值的DVB RCS载波估计算法研究

分析了DVB-RCS交互网回传链路中MF-TDMA信号同步遇到的关键问题,设计了一种通过FFT进行频偏粗估计,再分别利用DFT系数的幅度值和相位值进行插值运算,实现载波频偏和相偏联合估计的低复杂度的两步联合估计方法。理论分析和Monte Carlo仿真结果显示该算法的频差和相偏均方根误差均接近MCRB,两步联合估计的频偏估计性能随FFT点数增加而变优,粗估计消除了较大频偏对相位估计性能的影响。     

DVB-RCS通信网的接入技术研究

DVB-RCS通信系统是一个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。文中首先介绍了DVB-RCS系统的多址接入方式,分析了系统采用多频时分多址所带来的优点,然后重点讨论了回传终端进入和退出网络的过程,分析了每个阶段的目的和意义,并对必要的信令传递过程进行了说明。最后对系统接入技术的实现难点进行了讨论。     

一种应用于DVB-RCS卫星通信系统的存储优化带宽请求算法

DVB-RCS 卫星通信系统中,已有的带宽请求算法多注重于队列延迟以及带宽利用率等性能的提高而未考虑卫星终端的存储优化针对此问题,提出了一种应用于 DVB-RCS 卫星通信系统的存储优化带宽请求算法,该算法通过预测到达数据流的容量来实现对发送队列中数据总量的控制,同时兼顾对传输时延以及传输效率的平衡。仿真表明,该算法能够合理控制系统的存储容量,并且在优化带帘利用率、控制时延抖动等方面与已有算法相比具有同样的高性能.     

DVB-RCS Turbo码的研究及其实现

针对DVB-RCS中的双二进制Turbo码,提出一种新的改进译码方法.根据该改进算法,基于流水线设计思想,设计出硬件译码结构,给出时序图.结果表明,对于ATM和MPEG两种帧,其误比特性能比max-log-map算法提高0.2 dB.