实时友好的网络传输MPEG-4视频全局速率控制机制

本文提出了一种改进的TFRC算法,在传统的基于TCP吞吐量模型的TFRC速率控制方案中,利用RTP和RTCP协议,结合多媒体流的特征,精确估计带宽预测模型参数.在对有效带宽预测、时延抖动、丢包率等全面分析的基础上建立了全局速率控制模型.该模型结合速率自适应MPEG-4分级编码转换机制,体现分级优先特性,较好地保证了多媒体流实时友好及传输速率的平滑性要求,并给出了一定的实验验证.     

一种改进的业务带宽分配算法

根据虚信元丢失率和等效带宽分配的概念，提出了一种用于ＡＴＭ风格中的呼叫允许接入控制的虚拟等效带宽分配算法。该方法明显提高了链路带宽的利用率，同时在业务种类较多，呼叫数量较大的情况下，比理论计算方法在计算复杂度上有很大的改善，因而便于实时控制。     

等效电磁流一般和高阶表达式及其在双站散射中的应用

本文根据等效电磁流方法的概念，导出了求解物理光学场，边缘绕射场和总场的等效电磁流的一般表达式，它们可退化到目前已存在的各种等效电磁流公式；并提出了一种最佳的计算物理光学场的等效电磁流公式，根据半平面非均匀性电流的精确表达式，导出了一阶，二阶和三阶等效边缘电磁流的表达式，最后用本文导出的公式计算了菱形板的双站散射截面，计算结果和实验结果吻合良好。     

软交换下VoIP话务量与IP带宽间关系的分析及应用

随着软交换、网络IP化等技术的演进，交换机实现了控制和承载的分离，传统的信令、语音业务都通过IP网络承载的信令流和媒体流进行传送。在分析信令流的IP承载带宽时，需要考虑M3UA Sigtran、IP等各种协议栈的开销以及Mc、Nc等接口中各种信令流程下的消息流量和消息包的大小。相对于媒体流而言，信令流在整个IP带宽中占比很小，带宽规划时一般按一定比例进行估算，因此，这里对信令流的带宽关系不作进一步研究。     

流媒体技术浅议

１概述流媒体技术是近年来兴起的一种在线媒体播放技术，“流媒体”不同于传统的多媒体，它的主要特点就是以“视音频流”（Video－AudioStream）的形式进行数字媒体的传送，使人们在从很低的带宽（例如１４．４kbps）到较高的带宽（例如１０Mbps）环境下都可以在线欣赏到连续不断的较高品质的音频和视频节目。流媒体技术广泛应用在互联网多媒体新闻发布、网上路演、在线直播、网络广告、网路视频广告、电子商务、视频点播、远程教育、网路电台、实时视频会议等互联网的信息服务领域。２流媒体技术人们从网络上获取多媒体信息主要有两种方…     

一个基于动态带宽分配有效实时磁盘调度算法

多媒体服务器需要一个实时磁盘调度算法为具有软实时要求的连续多媒体流服务。传统的磁盘调度算法不适应实时多媒体流。提出一个新的实时磁盘调度DBA-SCAN（Dynamic-Band-width-Assignment-SCAN）算法。DBA-SCAN算法通过带宽预留和接纳控制机制为处于服务中多媒体流提供质量保证。对于非实时任务也预留了带宽以保证非实时任务具有合理的响应时间。DBA-SCAN采用一种积极策略在运行时动态回收未用的带宽。被回收的带宽被用于为可选任务或者更多的非实时任务服务。通过模拟实验对DBA-SCAN算法和WRR-SCAN算法进行对比,实验结果显示,DBA-SCAN为实时多媒体流提供了更好的质量。     

α,β,γ滤波器的等效带宽

常增益滤波器具有运算简单,存储量少以及不需要事先知道测量噪声和模型噪声等优点,因此在实际工程中得到了广泛应用。由于在理论分析和工程应用中往往需要知道α,β,γ滤波器等效带宽,为此文中给出了计算α,β,γ滤波器等效带宽的方法。并分析了α、β、γ滤波器的频率特性。最后给出了等效带宽的多项式拟合公式,为工程应用提供了方便、快捷的计算滤波器等效带宽的方法。     

基于TM1300的特低时延视频编解码系统的研究

本文阐述了如何在TM1300上实现特低时延的实时视频的传输，即：在带宽一定的情况下，对图像快速的编码，并将生成的码流经缓冲区缓冲后，高效地发送到解码端实时解码播放，保证解码重建图像的时延在250-350毫秒之间，甚至更少。     

一致性绕射理论的等效边缘电磁流在多边形板双站散射中的应用

介绍一致性绕射理论等效边缘电磁流（ＵＴＤＥＥＣ）的公式。该公式是基于Ｍｉｃｈａｅｌｉ的半平面等效边缘电磁流（ＥＥＣ）表达式，用平截的劈增量条计算等效边缘电磁流。这样可以消除以往计算中的虚假奇异点，对任意入射和观察方向均有良好的性态。本文用此方法计算了方板和梯形板的双站散射，并与高阶等效边缘电磁流的结果比较，具有良好的精度。     

高斯白噪声经过线性系统后的等效带宽特性研究

以随机信号经过线性系统理论为基础,研究了加性高斯白噪声经过滤波器后的带宽特性、等效带宽特性以及两者的关系,推导了以低通滤波器为例的线性系统的带宽和等效带宽公式。分析结果表明,等效带宽是说明线性系统滤波能力的一个重要参数,简单的使用带宽参数代替噪声等效带宽参数将使线性系统输出噪声功率的计算值增加,从而导致系统输出信噪比偏低,影响系统抗噪或滤波性能的评价。     

基于可用带宽满足时延和时延差别 约束的实时多播路由算法

实时多播路由中具有可加性的代价(Cost)不能确切反映网络本质特性,尤其不能反映路径带宽的凹性(Concave).已有基于代价的算法不能很好适应多播应用,需要新的模型和算法.本文采用可用带宽代替代价作为主要度量,并满足实时多播中二个重要约束度量:时延和时延差别.同时基于此三个度量,本文提出二种新的具有多项式复杂性的实时多播路由算法并比较其性能.新算法通过分析得到每路径时延和二约束之间的关系,有效降低涉及时延和时延差别此类问题的复杂性.新算法采用度量反映实时多播本质特性而具有实际推广性.     

FQLP:ATM网中一种新的实时业务调度算法

 本文提出了基于丢失优先权公平队列(FQLP)调度算法.理论分析和仿真实验表明FQLP调度算法能保证实时业务获得的网络资源不小于预约带宽,为实时业务提供确定的时延上界.FQLP调度算法利用ATM网络中的信元优先权机制,提高了网络资源的利用率.同时FQLP调度策略能保证信元的发送顺序.     

线性令牌传递网络中消息实时保证概率分析

本文针对线性令牌传递网络,提出了一种网络带宽分配方法和基于实时保证概率的网络性能分析方法,导出了消息严格实是的保证概率表达式,并给出了实用的近似算法。     

Resource Allocation for Real Time Services in LTE Networks: Resource Allocation Using Cooperative Game Theory and Virtual Token Mechanism

The LTE specifications provide QoS for multimedia services with fast connectivity, high mobility and security. However, 3GPP specifications have not defined scheduling algorithms to exploit the LTE characteristics to support real time services. In this article we propose a two level scheduling scheme composed by cooperative game theory, a virtual token mechanism, and the well known algorithms EXP-RULE and Modified-Largest Weighted Delay Firs (M-LWDF) in downlink system. By using cooperative game theory such as bankruptcy game and Shapley value, the proposed mechanism works by forming coalitions between flow classes to distribute the bandwidth fairly among all of them. Both algorithms EXP-RULE and M-LWDF have been modified to use a virtual token mechanism to improve their performance, giving priority to real time flows. By taking the arrival rate of packets into account, the proposed mechanism partially included in previous schedulers has been adapted to this work to increase remarkably the performance of the resource allocation for real time flows. The performance evaluation is conducted in terms of system throughput, Packet loss ratio, total cell spectral efficiency, delay and fairness index.     

A Novel Effective Bandwidth Based Call Admission Control for Multimedia CDMA Systems

A novel Call Admission Control(CAC)scheme is proposed for multimedia CDMA systems.The effectivebandwidth of real time calls is reserved in the CAC with the consideration of active factors.The admission of non-real timecalls is controlled by the system according to the residual effective bandwidth left from real time calls.Simulation resultshave shown that the novel CAC has greatly enlarged the admission region for real time calls and make the transmission de-lay of non-real time calls under an acceptable level.     

工业以太网非实时通信带宽的测量

介绍了工业以太网及其实时性,分析了在工业以太网中需要确定通信调度的原因,给出了测量非实时通信带宽的意义.讨论了非实时通信带宽的基本概念,并结合EPA网络给出了测量非实时通信带宽的方法,重点介绍了EPA网络某一链路上瓶颈带宽的测量.测试中控制台PC控制测试流程、设置测试参数以及结果的显示,测试代理PC执行具体的测试任务.实际测试证明测量方法可行,测试结果表明所测网络达到了要求的指标.     

Entropy Based Adaptive Flow Aggregation

Internet traffic flow measurement is vitally important for network management, accounting and performance studies. Cisco's NetFlow is a widely deployed flow measurement solution that uses a configurable static sampling rate to control processor and memory usage on the router and the amount of reporting flow records generated. But during flooding attacks the memory and network bandwidth consumed by flow records can increase beyond what is available. Currently available countermeasures have their own problems: 1) reject new flows when the cache is full - some legitimate new flows will not be counted; 2) export not-terminated flows to make room for new ones - this will exhaust the export bandwidth; and 3) adapt the sampling rate to traffic rate - this will reduce the overall accuracy of accounting, including legitimate flows. In this paper, we propose an entropy based adaptive flow aggregation algorithm. Relying on information-theoretic techniques, the algorithm efficiently identifies the clusters of attack flows in real time and aggregates those large number of short attack flows into a few metaflows. Compared to currently available solutions, our solution not only alleviates the problem in memory and export bandwidth, but also significantly improves the accuracy of legitimate flows. Finally, we evaluate our system using both synthetic trace file and real trace files from the Internet.     

Software-defined dynamic bandwidth optimization (SD-DBO) algorithm for optical access and aggregation networks

The optical access networks and aggregation networks are necessary to be controlled together to improve the bandwidth resource availability globally. Unified control architecture for optical access networks and aggregation networks is designed based on software-defined networking controller, the function modules of which have been described and the related extended protocol solution has been given. A software-defined dynamic bandwidth optimization (SD-DBO) algorithm is first proposed for optical access and aggregation networks, which can support unified optimizations and efficient scheduling by allocating bandwidth resources from a global network view in real time. The performance of the proposed algorithm has been verified and compared with traditional DBA algorithm in terms of resource utilization rate and average delay time. Simulation result shows that SD-DBO algorithm performs better.     

SAW-chirp压缩接收技术研究(英文)

介绍了现代电子战对接收机技术的新要求,分析了压缩接收机的原理及特点,指出了实现压缩接收机的关键技术:大带宽chirp信号的产生及处理;高速串行宽带视频信号的数字化处理技术;超大瞬时带宽的实现.给出了SAW调频延迟线实现压缩接收单元的具体方法,提供了包括连续波信号、调制信号的测试数据和波形,样品得到了瞬时带宽250 MHz、频率精度±375 kHz、灵敏度小于-80 dBm、动态范围大于60 dB的较好指标.     

大规模高帧频读出电路高速数据传输模型研究

本文针对大规模高帧频读出电路的数字信号输出建立了高速数据传输模型.首先由集总参数模型得到传输电路3 dB带宽及响应时间常数与各器件参数之间的关系,指明了输出级MOS管的尺寸及传输线负载是决定高速时域响应特性的关键参数.进一步采用分布参数模型,利用Elmore延时模型更精确地确定了响应时间常数的数学解析式,获得了可使带宽...