共查询到20条相似文献,搜索用时 906 毫秒
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针对分层多播接收者的可用带宽异构性问题,提出了一种自适应动态分层多播拥塞控制算法(ADLM).ADLM自适应地运用最优层输率分配算法来满足接收者的异构性,ADLM可以根据网络情况变化动态地调整分层的数量以及每一分层的层速率.仿真实验表明,该拥塞控制策略比分层组播控制常用的典型策略(RLC)更有效地利用网络带宽,解决网络带宽的异构性问题,同时ADLM是TCP友好的,较好地改进了分层多播拥塞控制的性能. 相似文献
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传输多媒体流的一种有效方法是采用多速率多播,但多速率多播的速率控制面临许多挑战,如异构性、公平性、实时性及服务质量(QoS)等。提出了一种两阶段优化的策略进行多媒体多播速率控制。把问题公式化为求系统效用最大化的最优化问题,推导出有效的算法。方法综合考虑了服务质量、异构性等,且满足协议间的公平性和多播会晤内各接收者间的公平性。仿真实验表明算法的有效性,与现有的算法相比系统总效用大大提高。 相似文献
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为缓解基站的视频流量过载,本文针对时延敏感的实时视频业务,设计一种D2D协作视频多播传输方案。该方案采用可伸缩视频编码(Scalable Video Coding, SVC)对视频流进行编码处理,利用SVC流的分层结构特征来应对多播信道间的差异性。在SVC编码的基础上,为了改善用户观看体验及提升用户所接收的视频质量,所提出的协作式视频传输方案引入有效吞吐量这一概念,在一定时延约束下,根据信道反馈信息灵活地对不同信道上的不同SVC视频层进行码率调整。仿真结果表明,所提出的方案能够有效地减小端到端时延,有效丢失率,提高有效吞吐量。 相似文献
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针对动态和异构网络环境下的实时视频多播,提出了一种基于终端系统的QoS过滤解决方法.该方法以收发两端所建立的双向反馈通道为基础,通过优化算法动态调整发送端的视频层次划分和层速率分配,灵活适应不同接收端的QoS要求.仿真实验表明,这种方法能够在保证TCP友好的同时,以较少的分层数目满足高质量、大容量的视频多播服务. 相似文献
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一、概述 为了实现带有实时性质的数据(例如交互式的话音和视频数据)从端到端的网络传递业务,由Internet的音频-视频传输工作组提出了实时传输协议,它的主要设计目标是满足多参与者多媒体会议的技术需要,但其应用范围远不止于此。下面我们首先对它作一个概括性的介绍。RTP的基本特征 实时传输协议(Real-time Transport Protocol,简称RTP)很适合用于发送多媒体数据(如音频流或视频流)给一个接收者(单播)或多个接收者(多播)。数据通常单方向传送,接收方不给确认信息。 与RTP同时存在的另一个协议是实时传输控制协议(RTCP),它让接收者给RTP发送者一个反馈信息(以及反之)。例如,接收应用程序可以告诉发送应用程序减慢视频流的速度。当速度减慢后,视频图象仍然可以显示,但可能出现跳动或分辨率降低。RTCP规范中的准则可以帮 相似文献
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提出了一种新的适用于分层多播拥塞控制方案中的往返时间(RTT)估算方法。该估算方法中
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多播会话中未被抑制的接收者进行RTT测量,被抑制接收者进行单向延时测量来估算RTT值,
同时该方法采用优先级因子将经常被抑制的接收者和具有较大RTT的接收者考虑在内。
仿真结果表明该算法是可行的。 相似文献
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Achieving inter-session fairness for layered video multicast 总被引:1,自引:0,他引:1
Wei Kuang Lai Chieh Ying Pan 《Broadcasting, IEEE Transactions on》2002,48(3):215-222
The Internet is increasingly used to deliver multimedia services. Since there are heterogeneous receivers and changing network conditions, it has been proposed to use adaptive rate control techniques such as layered video multicast to adjust the video traffic according to the available Internet resources. A problem of layered video multicast is that it is unable to provide fair bandwidth sharing between competing video sessions. We propose two schemes, layered video multicast with congestion sensitivity and adaptive join-timer (LVMCA) and layered video multicast with priority dropping (LVMPD), to achieve inter-session fairness for layered video multicast. Receiver-driven layered multicast (RLM), layer-based congestion sensitivity, LVMCA, and LVMPD are simulated and compared. Results show both proposed schemes, especially LVMPD, are fairer and have shorter convergence time than the other two schemes. 相似文献
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We propose a framework for efficient scalable video multicast over downlink orthogonal frequency-division multiplexing (OFDM) systems with multiple transmit antennas. In conventional video multicast systems, the achievable transmission rate is determined by the user with the worst channel condition, and the system saturates the capacity when the number of users increases. To accommodate the heterogeneous channel conditions and device capabilities of various users, scalable video coding (SVC) encodes video streams into base and enhancement layers. We exploit the advances in multi-antenna OFDM and the layered nature of SVC, and propose a framework for scalable video multicast which guarantees the base layer quality for all users while making best use of limited resource for the enhancement layer of users with good channel conditions. We show that the resource allocation that includes the transmit precoding, subcarrier allocation, and bit and power allocation is a very difficult optimization problem. A low-complexity suboptimal algorithm is proposed which is suitable for practical implementations. Simulation results are provided to show the effectiveness of the proposed solution. 相似文献
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Congestion control for IP multicast on the Internet has been one of the main issues that challenge a rapid deployment of IP multicast. In this article, we survey and discuss the most important congestion control schemes for multicast video applications on the Internet. We start with a discussion of the different elements of a multicast congestion control architecture. A congestion control scheme for multicast video possesses specific requirements for these elements. These requirements are discussed, along with the evaluation criteria for the performance of multicast video. We categorize the schemes we present into end-to-end schemes and router-supported schemes. We start with the end-to-end category and discuss several examples of both single-rate multicast applications and layered multicast applications. For the router-supported category, we first present single-rate schemes that utilize filtering of multicast packets by the routers. Next we discuss receiver-based layered schemes that rely on routers group?flow control of multicast sessions. We evaluate a number of schemes that belong to each of the two categories. 相似文献
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McCanne S. Vetterli M. Jacobson V. 《Selected Areas in Communications, IEEE Journal on》1997,15(6):983-1001
The “Internet Multicast Backbone,” or MBone, has risen from a small, research curiosity to a large-scale and widely used communications infrastructure. A driving force behind this growth was the development of multipoint audio, video, and shared whiteboard conferencing applications. Because these real-time media are transmitted at a uniform rate to all of the receivers in the network, a source must either run at the bottleneck rate or overload portions of its multicast distribution tree. We overcome this limitation by moving the burden of rate adaptation from the source to the receivers with a scheme we call receiver-driven layered multicast, or RLM. In RLM, a source distributes a hierarchical signal by striping the different layers across multiple multicast groups, and receivers adjust their reception rate by simply joining and leaving multicast groups. We describe a layered video compression algorithm which, when combined with RLM, provides a comprehensive solution for scalable multicast video transmission in heterogeneous networks. In addition to a layered representation, our coder has low complexity (admitting an efficient software implementation) and high loss resilience (admitting robust operation in loosely controlled environments like the Internet). Even with these constraints, our hybrid DCT/wavelet-based coder exhibits good compression performance. It outperforms all publicly available Internet video codecs while maintaining comparable run-time performance. We have implemented our coder in a “real” application-the UCB/LBL videoconferencing tool vic. Unlike previous work on layered video compression and transmission, we have built a fully operational system that is currently being deployed on a very large scale over the MBone 相似文献
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因特网上视频多点传输算法研究 总被引:4,自引:1,他引:3
本文研究因特网上进行视频多点传输的问题.在分析了资源预约协议和智体反馈控制机制的基础上,基于分层编码技术提出一种新的视频传输算法.文中利用ns-2网络模拟器进行了性能评价,结果表明该算法在保证视频基本服务质量的条件下,具有较好的公平性和可扩放性. 相似文献
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WDM光网络中光层组播技术的研究 总被引:1,自引:0,他引:1
本文分析了光层组播原理。在物理层实现组播 ,使该技术在整个互联网实施实时交互音像通信和有效抑止“电子瓶颈”效应有着重大作用。文中对两种不同结构具有光层组播的OXC进行了分析比较。并且对WDM光网络中的无阻塞组播通信波长满足条件进行了分析探讨。 相似文献
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组播技术的出现为基于P2P的视频会议系统提供了负载更小的开发方案,但在传统的组播技术支持下,分配到每台主机上的负载量依然可观。为解决突发负载问题,文中提出了一种基于主机性能评价的应用层组播算法,利用拓扑信息减少冗余数据在网络上传输,根据主机性能平衡负载分配,减轻主机负担。之后,在此组播算法之上,阐述了一种传统视频会议系统的优化实现方案。 相似文献