VBR MPEG-2业务统计复用特性的研究

VBR MPEG－2业务是ATM网络中的重要视频业务类型。本文建立了两个流体流视频复用模型，对其信元丢失率和传输延时特性进行了定性分析，得到了一些重要结论。通过对VBR MPEG－2业务进行复用仿真，验证了这些结论，并对业务源参数、复用缓冲器容量、业务强度与信元丢失率、传输延时特性之间的关系进行了分析。对ATM交换机和复用器的设计与性能分析具有一定指导意义。     

基于带宽需求预测的VBR业务速率分配

本文在对VBR业务带宽需求预测的基础上 ,提出了一种综合考虑信元丢失率、信道利用率、缓冲延时和缓冲器容量需求等方面的VBR业务频带动态分配的方法。对如何确定有关控制参数等问题 ,进行了研究 ,并就运用最佳线性预测和递归最小二乘法(RLS)等估计理论 ,对VBR业务流量速率的预测和控制 ,系统的性能作了分析和模拟     

VBR业务下的ATM交换机缓冲策略研究

ATM交换机的缓冲信元是基于业务流的实时状态而动态赋值的,因此,不同类型的业务客观上对ATM交换机的缓冲器容量提出不同的要求。本文对可变比特速率(VBR)业务下的ATM交换机缓冲策略进行研究,并给出了计算机模拟结果。     

CATV网络中MPEG—2TS复用器的程序算法

本研究有线电视台（CATV）网中复用器的程序算法。首先提出程序矩阵这一概念。然后研究两种程序算法；用程序矩阵来描述的可变码率（VBR）算法和传统的固定码率（CBR）算法。尤其是VBR程序算法，能够在CATV网中对MPEG－2节目实现良好的显示，采用VBR程序算法的程序机（每一个输入流）拥有一台计数器，以便决定在现有的程序周期（一帧周期）内应发送多少个传送码流（TS）数据包，以防止出现界限干扰（Deadline Violation)，每一个输入流的实时比特率用来更新程序矩阵的参数，VBR程序算法在数字上可与CBR程序算法相比拟。模拟的结果表明，VBR程序算法与CBR算法相比较，大大减少了延迟（即界限干扰概率），带宽利用率也高。     

会议电视业务及其市场需求

简要介绍会议电视业务的特点，国外会议电视技术发展历程与现状，我国近来年建设会议电视网的情况，以及建设四川省会议电视网的设想；分析了会议电视业务的主要应用与市场需求。指出随着我国经济的迅速发展，各级政府部门行政管理、工商经贸活动以及电视教育等领域将广泛应用会议电视业务，逐步迎来我国会议电视大发展的新时期。（ｅｄ）     

国际电联有关广播电视业务1997年会议情况及结果通报

国际电联无线电通信部门（ITU－R）第10研究组（SG10）（声音广播业务）和第11研究组（SG11）（电视业务）于1997年4月7日至4月25日同时在日内瓦召开了其所属的工作组（WP）、任务组（TG）及研究组全体会议，出席会议的代表均以各国政府主管部门的身份参加会议。经粗略统计，大约有来自40多个国家和3个国际电视组织的200多名代表出席。广电部这次派出包括科技司、国际台、中央电视台、广科院的4名代表组成的中国电信专家组分别出席SG10和SG11的各工作组会议。由于本届会议内容丰富，实用性强，新技术含量高，将在此作较详实的报导，…     

视听资料索引

视听资料索引（一）播控中心系统与设备多媒体时代电视的作用专刊电视学会志（日），１９９５．１１１０７６总论１０７７媒体社会的动向１０７８未来电视方向１０７９个人生活中未来电视的作用１０８０多媒体时代的广播业务技术的可能性与观众的选择１０８１作为多媒体信...     

Gamma自回归视频模型的研究

分别介绍了VBR视频业务的发展情况，传统的业务模型DAR(1)，并给出了相关的结论证明。最后，介绍了一种新的业务模型GAR(1)，给出定义，分析特性。利用此模型产生的视频仿真数据相当便捷、准确。     

邮电部开设新业务

邮电部开设新业务１９９４年年底，中国邮电电信总局在北京召开的＂新业务发布会＂上，正式推出会议电视、８００（被叫集中付费）等４种新业务。会议电视业务适合我国幅员辽阔、人口众多、交通紧张和会议频繁等特点。全国会议电视骨干网于＇９３开始组建，目前会议电视业...     

基于动态令牌轮询提供视频QoS 保证的无线ATM多址接入控制

本文提出了一种基于动态令牌轮询调度算法（DTSA）的无线多址接入控制（MAC）机制,该方案应用于无线ATM系统,为多媒体业务提供了服务质量（QoS）保证的无线接入.基站控制器为每个ATM连接建立令牌模型,根据模型进行时隙分配.为了适应诸如压缩视频流等实时VBR业务的动态特性和严格的QoS要求,定义了移动站用于通知基站其源帧率变化及队列情况的紧急消息.一旦收到紧急消息,基站将分配一定数目的令牌进入紧急令牌队列.根据结合紧急令牌队列的令牌轮询调度机制,基站可以进行灵活的时隙分配.通过仿真计算,我们发现该机制能较大地提高实时VBR业务的时延和丢失性能.本文还就影响该机制性能的设计参数进行了分析.     

A new approach to long‐range dependence in variable bit rate video traffic

Recently it has been observed that variable bit rate (VBR) video traffic displays long‐range dependence, which suggests that traditional Markovian models may not be suitable for performance evaluation of telecommunications networks carrying this traffic. Inspection of the bit rate profile of VBR video traffic suggests that shifting level processes might be more appropriate for this task. In this paper we show that a particular class of these processes matches the autocorrelation and bit rate distribution of real VBR video traffic, including exhibiting long‐range dependent behaviour. This revised version was published online in June 2006 with corrections to the Cover Date.     

基于小波支持向量机的VBR视频流量预测

：VBR视频流量具有时变性、突发性和非线性等变化特点,为了提高VBR视频流量的预测精度,提出一种小波支持向量机的VBR视频流量预测模型(WSVM)。首先对VBR视频流量时间序列进行相空间重构,然后将其输入到小波支持向量机进行学习,建立VBR视频流量预测模型,最后采用仿真实验对模型性能进行测试,并与支持向量机、小波神经网络进行对比。仿真结果表明,相对于其它预测模型,WSVM模型提高了VBR视频流量预测精度,能够更加准确反映VBR视频流量的复杂变化规律。     

Study of the impact of MPEG-1 correlations on video-sourcesstatistical multiplexing

Variable bit-rate (VBR) video is expected to become increasingly important with the large scale deployment of broadband-integrated services networks (B-ISDNs). While the modeling of VBR video sources has received significant attention, there is no widely accepted model which lends itself to mathematical analysis. Furthermore, new video compression standards are emerging, such as the MPEG family. A detailed statistical analysis of a long sample of a movie encoded with an MPEG-1 algorithm highlights that traffic generated by an MPEG-1 encoder has both a high degree of burstiness (peak/average ratio greater than five) and a strong long-term correlation (positive correlation lasts for ten/twenty minutes). In this paper, we propose and analyze a Markov model which captures both the burstiness and the temporal dependencies of MPEG traffic. Furthermore, we show that our model is a flexible traffic generator which is suitable for studying statistical multiplexing issues. Specifically, we study both the multiplexing of a VBR video source with low priority traffic and the multiplexing of several VBR video sources. The results obtained show that the long-term correlation significantly affects the tail of the delay distribution even for lightly loaded networks. The presence of a long range dependence in the MPEG traffic significantly reduces the gain in terms of network utilization which can be achieved with statistical multiplexing of i.i.d. sources     

Design of a fair bandwidth allocation policy for VBR traffic in ATMnetworks

Since real-time variable bit rate (VBR) traffic is inherently bursty, dynamic bandwidth allocation is necessary for ATM streams that carry VBR traffic. In order to provide quality-of-services (QoS) guarantees and to reduce the computational complexity, an hybrid of guaranteed and dynamic adaptive allocation scheme requires to be implemented. Typical dynamic allocations to competing streams are done in the form of linear proportions to the bandwidth requirements. We show that during temporary link congestion such proportional arrangements can give rise to unequal queue growth and, subsequently, degraded QoS. This is found to be true even for streams that belong to the same VBR class and share identical long term traffic characteristics and QoS requirements. In this paper, four allocation algorithms are presented and analyzed in terms of their fairness and QoS potential for real-time VBR traffic. We propose and show that a novel allocation strategy, termed Minmax, solves the mentioned problem of unfairness within a class. By maintaining a fair distribution of buffer length across the streams of a class, the proposed policy can achieve better and fairer QoS performance compared to the traditional methods. We present analytical results, proofs and a simulation study of the described algorithms. Four allocation policies for handling MPEG VBR video streams are simulated in the context of a wireless ATM (WATM) medium access control. The results show that in certain scenarios, the Minmax strategy can reduce losses by an order of magnitude, while decreasing delays substantially     

Accurate Prediction of Real‐Time MPEG‐4 Variable Bit Rate Video Traffic

In this letter, we propose a novel algorithm to predict MPEG‐coded real‐time variable bit rate (VBR) video traffic. From the frame size measurement, the algorithm extracts the statistical property of video traffic and utilizes it for the prediction of the next frame for I‐, P‐, and B‐ frames. The simulation results conducted with real‐world MPEG‐4 VBR video traces show that the proposed algorithm is capable of providing more accurate prediction than those in the research literature.     

An adaptive reservation scheme for VBR voice traffic in wireless ATM networks

A reservation scheme, named dynamic hybrid partitioning, is proposed for the Medium Access Control (MAC) protocol of wireless ATM (WATM) networks operating in Time Division Duplex (TDD) mode. The goal is to improve the performance of the real-time Variable Bit Rate (VBR) voice traffic in networks with mixed voice/data traffic. In most proposed MAC protocols for WATM networks, the reservation phase treats all traffic equally, whether delay-sensitive or not. Hence, delay-sensitive VBR traffic sources have to compete for reservation each time they wake up from idle mode. This causes large and variable channel access delays, and increases the delay and delay variation (jitter) experienced by ATM cells of VBR traffic. In the proposed scheme, the reservation phase of the MAC protocol is dynamically divided into a contention-free partition for delay-sensitive idle VBR traffic, and a contention partition for other traffic. Adaptive algorithms dynamically adjust the partition sizes to minimize the channel bandwidth overhead. Simulation results show that the delay performance of delay-sensitive VBR traffic is improved while minimizing the overhead.     

一种基于扩展自相似过程的VBR视频业务新模型

本文在扩展自相似过程的基础上 ,提出了一种简单的视频业务新模型。该模型的边缘分布近似Gamma分布 ,且其具有长或短的相关性。在许多时间尺度上 ,这些特性可以很好地匹配众多实际变比特率视频业务的一、二阶统计特征。仿真实验中 ,通过利用该模型模拟实际视频信号 ,我们证明它也能很好地反映实际视频业务的排队性能     

Buffer losses vs. deadline violations for ABR traffic in an ATM switch: A computational approach

The B‐ISDN will carry a variety of traffic types: the Variable Bit Rate traffic (VBR), of which compressed video is an example, Continuous Bit Rate traffic (CBR), of which telemetry is an example, Data traffic, and Available Bit Rate traffic (ABR) that represents aggregate data traffic with very limited guarantees on quality. Of these, VBR and CBR have timing constraints and need synchronous bandwidth; data traffic is relatively delay insensitive. In this paper, we consider the VBR, Data and ABR traffic types and obtain the cumulative distribution function (cdf) of the queueing delay experienced by a burst of ABR traffic in the output buffer of an ATM switch. The cdf is used to trade off buffer loss probabilities against deadline violation probabilities through adjusting the buffer size and (delay) deadline values. Large buffers result in low losses but queueing delays can become excessive and cause a high level of deadline violations. Both losses and violations are detrimental and an operating point must be chosen to achieve a balance. In this paper we study the nature of the trade off. We develop a stochastic Petri net model assuming periodic burst arrivals for VBR and Poisson arrival processes for the Data and ABR traffic types at the burst level, and solve the model analytically (numerically) using a decomposition approach. This decomposition, along with the inherent decomposability of the tagged customer approach for obtaining the cdf opens up a possibility of carrying out fast computations using a parallel machine for selecting the operating point each time that a call is admitted. This revised version was published online in June 2006 with corrections to the Cover Date.     

A multi‐level satellite channel allocation algorithm for real‐time VBR data

Integrated services over a shared satellite channel need a MAC protocol that is able to deal with real‐time traffic without substantially affecting the efficiency of the shared medium. Due to its bursty nature, MPEG coded VBR video transmission is one of the most challenging real‐time applications. In this paper, we analyse the statistical performance of a simple allocation method for VBR traffic by using an accurate statistical model of an MPEG‐2 VBR coded movie, whose traffic exhibits a peak to mean ratio of about 4. The results were obtained both analytically and by simulation, and show that our method is suitable for transmitting non‐interactive video and best‐effort traffic on the same satellite link. The efficiency of the proposed method shows no dependency on the statistical properties of the input traffic. Copyright © 2002 John Wiley & Sons, Ltd.     

Provisioning of Parameterized Quality of Service in 802.11e Based Wireless Mesh Networks

There has been a growing interest in the use of wireless mesh networks. Today’s wireless technology enables very high data rate up to hundreds of Megabits per second, which creates the high demand of supporting real-time multimedia applications over wireless mesh networks. Hence it is imperative to support quality of service (QoS) in wireless mesh networks. In this paper, we design a framework to provide parameterized QoS in 802.11e based wireless mesh networks. Our framework consists of admission control algorithms and scheduling algorithms, which aim at supporting constant bit-rate (CBR) traffic flows, as well as variable bit-rate (VBR) traffic flows. We first present deterministic end-to-end delay bounds for CBR traffic. We then prove that the delay of VBR traffic can be bounded if the traffic flow conforms to a leaky-bucket regulator. We further study different admission control algorithms for VBR traffic. Our simulation results show that, by taking advantage of statistical multiplexing, much more traffic flows can be admitted.