采用DM642平台设计MPEG-4视频流传输系统

介绍了在DM642平台上实现监控系统中视频流子系统的设计方案和关键技术,提出了基于B/S架构的传输系统的设计方法,可为用户提供远程访问.该系统采用流媒体协议对MPEG-4数据进行流化和传输,具有较好的传输质量和监控效果;且支持RTSP协议远程点播功能,提高了用户与服务器的交互性.实验结果表明,该设计方法较大地提高了系统的可扩展性和开发的质量,有较强的实用性.     

机顶盒参与P2P分发的IPTV点播业务可行性研究

为了有效降低上海电信IPTV的运营和部署成本,由机顶盒参与P2P分发的IPTV点播方案是一个可能的有效方案。为了研究这个方案的可行性,首先提出了机顶盒参与P2P分发的IPTV系统主要性能指标及主要影响参数,分析上海电信IPTV系统的实际用户行为数据和实际网络拓扑,并构建大规模IPTV计算机仿真系统RVSPS,然后用真实的用户行为和拓扑激励仿真系统,分析各类参数对主要系统性能指标的影响,从技术角度详细研究机顶盒参与P2P分发的上海电信IPTV点播业务的可行性。     

基于P2P的数字版权管理系统体系及协议研究

在分析了P2P网络模式和数字版权管理(DRM)技术体系的基础上,提出了基于P2P模式的DRM系统体系,并对系统体系结构和传输协议进行了研究与探讨.基于体系的拓扑结构,提出了体系功能框架,并对其中内容管理、内容标识、付费机制和质量控制进行分析和设计.同时以数字内容的生命周期和价值链为依据,对体系工作的流程进行了深入探讨.给出了体系的数字内容上传和下载协议,实现了P2P网络模式与DRM技术体系的有效集成.     

一种基于移动代理的P2P系统主动负载均衡算法

负载均衡是P2P系统的研究热点,针对现有负载均衡算法的不足,提出了一种基于移动代理的主动负载均衡算法.该算法使用移动代理收集负载信息、生成负载迁移决策,降低了系统的通信开销,而且避免了单点失效问题和"颠簸"现象.通过引入对用户请求的评估和迁移,预见性的处理负载问题,提高了系统的服务质量.     

VoD广播协议分析和建模

以准视频点播技术为背景,通过对该技术的核心要素-VoD广播协议族进行归纳、分析,并从宝塔广播协议出发,设计了一个新的数学模型--宝塔模型,并由该模型出发分析了N-VoD系统的性能与特点.该模型在一个8 MHz模拟频道上传输两套数字节目,其点播最大延迟为8 s,大大缩短了用户等待时间.     

一种基于Echord协议的网格资源发现方法

针对网格集中式的资源发现方法存在单点失效、负载均衡差等问题,提出利用P2P技术进行网格资源发现方法.该方法通过改进Chord协议的后继节点函数和finger表,提出Echord(Enhanced Chord)协议,结合Echord协议特点,将网格中的虚拟组织构建成环状拓扑结构.网格资源被描述成基于XML的RDF形式,并按照一定的资源部署算法被均衡地发布在网格节点上.给出了如何应用Echord协议进行网格资源发现的算法.理论分析和仿真实验结果表明,相比于基于Chord的网格资源发现方法,该方法能改善系统的平均查找长度、消息传播性能、资源随机查找成功率.     

视频流广播协议的研究和建模

以准视频点播技术为背景,通过对该技术的核心要素--VoD广播协议族进行归纳、分析,并设计了一个新的数学模型--宝塔模型,并由该模型出发分析了N-VoD系统的性能与特点.该模型在一个8 MHz模拟频道上传输4套数字节目,其点播最大延迟为8 s,大大缩短了用户等待时间.     

基于CCP模型的BitTorrent集群测量研究

对P2P集群的测量与分析,有助于理解其现状及演变规律,从而对其进行优化和管理.根据赠券收集模型的一般原理并进行了优化,设计实现了一种主动测量方法及平台,可用较少的主机对全球BitTorrent集群开展持续的主动测量.该方法能在短时间内,获取每个集群中超过90%的在线节点,同时对网络本身的影响较小.在近9个月的实验中,分别测量了从Torrentz获取的3万多个BT集群.结果表明BT集群中的节点分布具有明显的地域性,而且国内外用户在客户端和端口使用上具有明显的偏好.     

基于混合云计算模式的数字内容分发平台时延性能研究

首先介绍了CDN网络、P2P网络和云计算的关系,随后基于现有的云计算的特点和性能提出了一种基于混合云模式的数字内容分发平台网络体系结构,并对该网络拓扑体系结构的时延性能进行了分析,并得出了一些有益得结论.     

提供可靠服务的P2P流媒体点播系统

针对P2P流媒体点播的稳定性和可靠性问题,该文提出一种基于节点可靠度和服务质量评价的点播系统结构RP2MoD。节点根据父节点的失效概率计算自身可靠度,并在点播时对父节点的服务质量作评价。父节点的选择、媒体数据的分配策略以及容错和恢复处理均以此为基础。理论分析和仿真表明,系统具有较强的容错能力,能提供稳定可靠的点播服务,而增加的可靠度和服务质量的相关操作对系统性能影响甚微。     

An object-oriented analysis of a BISDN control system with a focus on the UNI protocol object

The control system of a BISDN network will undoubtedly be very complex to design, implement and maintain. Its complexity has led researchers to look for ways of breaking down the problem into smaller and manageable parts. This has motivated the use of an object-oriented approach to analyse and comprehend the BISDN control system. This paper thus presents an object-oriented analysis (OOA) of a BISDN control system. This analysis is based on a method introduced by Coad and Yourdon and comprises five steps. All five steps, namely identifying subjects, identifying objects, identifying structures, defining attributes, and defining operations, will be worked out in detail with an emphasis on the user network interface (UNI) signalling protocol object. Four subjects, nine objects, and three structures are identified in the problem space at hand. This structuring offers a framework to analyse in detail the three aspects, data, structure and dynamic behaviour, of the UNI signalling protocol. A parallel between this approach and the well known approach used by the International Telecommunication Union (ITU) for specifying signalling protocols and contained in Recommendation I.130 is drawn. The Coad and Yourdon OOA approach applied to a BISDN control system can be used for the analysis of different aspects of such systems. This paper focuses on the UNI signalling protocol object which leads to a complete specification. Any protocol resulting from such analysis can be claimed to be object-oriented protocol. This approach offers modularity and thus offers a way of structuring the problem space into identifiable objects and data. Full benefits of object orientation can be gained only in the consistent use of object orientation throughout all steps in the development process. The proposed approach allows one to create libraries of generic procedures which can be reused in specific implementations.     

基于用户身份认证的安全计费系统的研究

网络规模的扩大、用户数量的增加,给网络管理、安全、计费都提出了新的需求.在方便用户的基础上,通过对数据采集模式、认证协议和一些网络安全性的探讨,构建了一个稳定、可靠、廉价、安全的网络计费系统,解决了IP地址的不足和用户移动性的增强的问题.     

VoIP transmission mechanism based on TCP

As the widespread employment of firewalls on the Internet, user datagram protocol (UDP) based voice over Internet protocol (VoIP) system will be unable to transmit voice data. This paper proposed a novel method to transmit voice data based on transmission control protocol (TCP). The method adopts a disorder TCP transmission strategy, which allows discontinuous data packets in TCP queues read by application layer directly without waiting for the retransmission of lost data packets. A byte stream data boundary identification algorithm based on consistent overhead byte stuffing algorithm is designed to efficiently identify complete voice data packets from disordered TCP packets arrived so as to transmit the data to the audio processing module timely. Then, by implementing the prototype system and testing, we verified that the proposed algorithm can solve the high time delay, jitter and discontinuity problems in standard TCP protocol when transmitting voice data packets, which caused by its error control and retransmission mechanism. We proved that the method proposed in this paper is effective and practical.     

A Provably Secure Multi-server Based Authentication Scheme

With the rapid growth of electronic commerce and demand on variants of Internet based applications, the system providing resources and business services often consists of many servers around the world. So far, a variety of authentication schemes have been published to achieve remote user authentication on multi-server communication environment. Recently, Pippal et al. proposed a multi-server based authentication protocol to pursue the system security and computation efficiency. Nevertheless, based on our analysis, the proposed scheme is insecure against user impersonation attack, server counterfeit attack, and man-in-the-middle attack. In this study, we first demonstrate how these malicious attacks can be invoked by an adversary. Then, a security enhanced authentication protocol is developed to eliminate all identified weaknesses. Meanwhile, the proposed protocol can achieve the same order of computation complexity as Pippal et al.’s protocol does.     

Power splitting–based energy‐harvesting protocol for wireless‐powered communication networks with a bidirectional relay

In this paper, we apply the power splitting–based energy‐harvesting protocol to enhance the transmission between a wireless access point and a mobile user via a helping relay. The mobile user exploits the energy supplied by the access point and forwarded by the relay to transmit its own data back to the access point, again with the helping of the relay. Here, the effect of various system parameters, including power‐splitting factor and the power‐to‐noise ratio on the system performance, is rigorously studied, with closed‐form expressions for the outage probability and system throughput as the results. Furthermore, we figure out the optimal power‐splitting ratio at which the information throughput from the user to the AP is maximized, subject to the constraint on the transmitting power at the access point. All above analytical results are also supported by Monte Carlo simulation.     

绿色通信网的设计分析

网络节能在无线网络中已经有了很多的研究,并已经取得了很好的成果,本文从有线网络的角度首先分析了有线网络现状,然后从单个交换设备、网络级和拓扑级分析可能的节能基点,并建议从网络设计、系统设计和协议设计3方面注重能量意识从而达到节能效果。最后从主要的休眠技术出发分析了节能可能对OSPF等路由协议和网络拓扑影响,从软件和硬件方面对现有的网络和拓扑稍加改变将会达到很好的节能效果。     

Packet Reservation Window Multiple Access for Microcellular Voice/Data Transmission

We propose a new packet reservation multiple access (PRMA) scheme for the joint transmission of voice and data traffics in a microcellular medium. The collision resolution protocol within the system is based on a modification of the window random access algorithm, which has superior properties compared to the conventional slotted Aloha. The proposed algorithm, which we call packet reservation window multiple access (PRWMA), works in distinct modes for voice and data without prioritization, and the user performs slightly different operations depending on the information type. Simulation results show that PRWMA outperforms PRMA by a significant margin in terms of voice user capacity.     

手机上网业务质量端到端分析方法和系统

为保障客户的上网体验,需要建立一套贴近客户感知的业务质量评估体系;需要贯通手机上网“端管云”各个环节,分析定位质差问题、开展优化提升。本文介绍了一种手机上网业务质量端到端分析方法和系统,基于4G信令构建业务感知评估体系,通过业务端到端分析模型定界到业务质差环节。     

基于主动测量的HTTP端到端体验质量测量技术研究

随着互联网的普及和发展,网络应用业务用户使用感受的测量愈发重要。HTTP作为互联网典型应用万维网服务的传输协议,对它的体验质量进行测量不仅有助于了解各个网站的用户体验,同时也将为互联网的其他应用业务的测量提供参考。通过使用基于主动测量的测量工具SimBrowser对若干网站进行测量,以及对比用户的实际体验,验证了测量方法的可行性,并初步了解了一些HTTP端到端体验质量与服务质量的关系。     

TD-SCDMA网络Iu-PS接口协议关联方案的设计与实现

为了对TD-SCDMA 网络的用户流量进行识别以及对用户行为进行分析,对Iu-PS 接口的信令面与业务面协议进行了研究,设计出一种信令面和业务面协议关联的方案。针对传统信令监测系统和业务监测系统数据处理效率的不足以及无法将信令面与业务面数据进行关联的缺陷,利用增强型散列算法以及超时处理技术,设计出一种基于关键字段关联的信令面呼叫详细记录（call detail record,CDR）和业务面呼叫详细记录合成的协议关联方案,提高了数据处理效率,并实现了信令面和业务面数据的有效关联,为后期进行流量识别以及对用户行为进行分析奠定了基础。经过现网数据测试,验证了该协议关联方案的正确性与可行性,在移动互联网流量分析领域具有推广意义。