基于核密度估计的可变码率视频流量预测算法

为解决实时可变码率(VBR)视频在传输中难以准确预测流量的问题,提出一种变带宽核密度估计算法。该算法以核密度估计算法为基础,针对VBR视频的场景切换特性动态改变各样本点的带宽,加快算法收敛速度。仿真结果表明,与变步长归一化最小均方法相比,该算法能够减少10%左右的预测误差,保证流量预测具有较高的预测精度。     

H.264/SVC比特自适应分配的等级B帧码率控制算法

为减少码率控制中实际输出码率与目标码率之间的误差,改善视频序列编码尾部质量下降的缺陷,同时针对可伸缩视频编码中码率控制算法的不足,提出一种自适应比特分配的码率控制算法。算法基于对根据相邻图像帧之间的相关性以及对恒定质量的考虑,在图像组(GOP)之间平均分配目标比特,而在GOP内部则根据编码复杂度自适应分配目标比特,同时适当调整初始量化参数(QP),再根据目标比特分别计算P帧、B帧的QP。对不同的视频序列进行了实验测试,其结果验证了算法的准确性和有效性。     

MPEG-4 FGS流媒体的常质量GOP带宽分配机制

分析MPEG-4FGS的位平面R-D模型，提出一种基于场景的常质量GOP带宽分配机制及GOP带宽分配的静态算法和动态算法，以保证同一场景内连续GOP的质量稳定．实验结果表明：常质量GOP带宽分配机制能够平滑一场景内连续GOP的质量，并且连续帧的质量波动也较小．     

场景切换视频自适应帧间码率控制

针对视频帧中可能出现的大量场景切换,提出一种基于非连接点的场景切换检测算法,提高编码性能,该场景检测算法复杂度低,在运动估计的同时,完成视频场景切换检测。场景切换将导致GOP(group of pictures)长度的变化,并可能出现GOP长度太短的情况。提出改进的自适应GOP时域滤波技术,避免由于GOP太短引起的编码性能下降。针对视频场景切换检测分割出的不同长度的GOP,提出一种基于率失真模型的帧间码率控制算法,利用视频的失真与码率及视频帧复杂度的关系,对帧间码率分配进行优化,提高重构视频帧的总质量。实验结果表明,基于场景检测的自适应帧间码率控制算法能够获得较好的编码性能。     

一种H.265视频带宽实时预测模型

针对视频直播过程中带宽抖动导致视频帧丢失造成用户体验降低问题,提出了一种H.265视频带宽实时预测（VBRP）模型。模型基于马尔可夫链,专注于H.265编码的直播视频流,研究了在GOP（group of pictures）编码模式下B帧出现的统计特性,发现B帧大小对视频流传输速率的影响较大。应用此特性可预测出直播流中B帧的大小,并根据网络带宽选择性丢弃B帧,同时引入步长调整因子AF和误差阈值FT,均衡模型在预测B帧时的训练频率和预测帧数。最后基于模型实现VBRP预测算法并在直播系统中验证算法的有效性。     

基于自适应GOP的三维提升小波视频编码技术

在三维提升视频编码框架中,视频运动场景切换时相邻视频帧之间的时间相关性将显著减弱,使得解码视频图像在场景切换处质量急剧下降.针对这一问题,提出了一种新的基于视频亮度分量的场景切换检测方法,并根据场景切换自适应分配图像组(groupof picture GOP)大小.实验结果表明,该自适应分配GOP策略有效提高了三维提升小波视频图像的编解码质量,降低了场景切换对视频编码的影响.     

基于自相似流量预测的TCP拥塞控制算法

针对高带宽网络环境下传统TCP Reno的拥塞控制效率低的问题,提出了一种适用于随机丢失网络的TCP拥塞控制改进算法.介绍并分析了网络流量自相似特性和预测的时间尺度,并进行了TCP链路流量预测及可用带宽估计,当网络出现丢包时根据估计的带宽动态设置慢启动阈值.OPNET仿真结果表明,该算法在高随机丢包的情况下吞吐量得到了明显改善.     

基于WiMAX的实时业务带宽优化调度策略

WiMAX是一项无线城域网(WMAN)技术,支持实时与非实时等多种业务,SS可以向BS动态申请所需求的带宽,由IEEE 802.16协议定义.但协议中没有具体定义实时服务QoS所需要的带宽调度策略.因此,如何高效地分配使用带宽,成为一个亟需解决的问题.本文提出一种自适应的实时轮询业务带宽分配策略,SS依据当前带宽需求和以往的实际分配带宽,提前预测实时业务数据包所需求的确切带宽.文中给出了数学分析模型和仿真.仿真结果表明,与传统的带宽分配机制和其他自适应算法相比,该自适应的带宽分配算法能更好地改善系统性能,提高吞吐量,减少时延和减少缓冲区需求.     

基于SVC与多网络接口的DASH调度算法

基于HTTP的动态自适应流媒体(DASH)技术是主流的互联网视频传输技术之一,可适应动态网络和异端客户端,然而传统DASH使用高级视频编码(AVC),存在编码块复用性低、码率波动性高等问题。为此,在终端设备具有多网络接口的环境下,以可伸缩视频编码(SVC)代替AVC,提出一种基于视频块优先级的联合调度算法。通过SVC编码将整个缓冲区组织为一个包含时间维度和编码层次维度的二维空间,确定视频块在二维缓冲区的位置,将其放入待下载队列,并按照优先级对队列中的视频块进行重新排序。根据每个网络接口的带宽,将队列中的视频块分配给不同接口执行下载操作。实验结果表明,相比于单接口基于带宽和缓冲的调度算法,该算法的平均视频质量提高46.04%,切换次数降低36.84%,并且可使缓冲水平下降44.11%。     

EPON中基于滑动周期的动态带宽分配改进算法

动态带宽分配(DBA)算法是EPON技术的关键.传统的间插轮询自适应周期长度(IPACT)算法被证明在不规则流量下会遭遇严重的带宽利用率下降.基于滑动周期的SLICT算法可以解决这一问题,然而公平收敛性和带宽利用率之间的冲突限制了其在高突发性网络环境下的性能.本文提出一种改进的SLICT算法,在每次授权时都综合考虑网络实时负载变化.仿真结果证明改进的SLICT算法可以同时达到高带宽利用率和有保证的公平收敛性,性能较现有算法有进一步提高.     

面向RCBR网络的变比特率MPEG视频流的自适应预测

变比特率视频业务是将来多媒体业务的主要组成部分，为保证高质量，实时传输的需要，准确把握视频特征，结合网络传输机制为多媒体通信提供更好的服务质量（QoS)是目前亟待解决的问题之一，该文针对面向RCBR（Renegotiated Constant Bit Rate)网络的变比特率MPEG视频提出了基于编码结构的自适应预测算法，它充分利用了视频流的周期相关性，能准确快速，无延迟地对视频帧的码率进行预测，通过网络动态地为视频分配合适的带宽，不仅能达到高质量，低延迟抖动的视频服务，并且提高了网络的利用率，与分配固定带宽的网络相比，其网络缓冲的排除性能和网络的利用率有明显提高。     

Sparse basis selection: new results and application to adaptive prediction of video source traffic

Real-time prediction of video source traffic is an important step in many network management tasks such as dynamic bandwidth allocation and end-to-end quality-of-service (QoS) control strategies. In this paper, an adaptive prediction model for MPEG-coded traffic is developed. A novel technology is used, first developed in the signal processing community, called sparse basis selection. It is based on selecting a small subset of inputs (basis) from among a large dictionary of possible inputs. A new sparse basis selection algorithm is developed that is based on efficiently updating the input selection adaptively. When a new measurement is received, the proposed algorithm updates the selected inputs in a recursive manner. Thus, adaptability is not only in the weight adjustment, but also in the dynamic update of the inputs. The algorithm is applied to the problem of single-step-ahead prediction of MPEG-coded video source traffic, and the developed method achieves improved results, as compared to the published results in the literature. The present analysis indicates that the adaptive feature of the developed algorithm seems to add significant overall value.     

多业务流量预测动态带宽分配方法

静态带宽资源分配方法或基于业务分类的动态带宽分配方法等很难适应业务流特性,无法保证各级业务的服务质量。设计了流量预测及带宽分配模型,给出了流量预测计算方法,提出多业务流量预测动态带宽分配方法（MSTPDBA）,该方法基于业务预测流量的大小进行可用带宽的重新分配。仿真实验证明了MSTPDBA的有效性,能控制不同业务的时延,并提高了系统带宽资源的利用率。     

Bandwidth allocation in UWB WPANs with ECMA-368 MAC

The new ECMA-368 MAC for UWB WPANs consists of two channel access methods: the distributed reservation protocol (DRP) and prioritized contention access (PCA). The exact method of medium access slot (MAS) allocation in DRP is not specified in the standard. The contribution of this paper is twofold. First, the paper describes a distributed resource allocation method in which a number of interference–avoidance rules are used to reserve slots for devices. Devices maintain sending and receiving tables to track activities in the neighbourhood. The proposed method is a simple, effective solution to the DRP MAS allocation problem, avoiding reservation conflicts and interference from hidden terminals. Secondly, for VBR MPEG-4 video traffic, we propose a bandwidth requirement calculation method based on traffic prediction. In the proposed scheme bandwidth is allocated based on accurate traffic predictions, therefore matching network resources to the traffic demand. Application QoS is maintained while network utilization is kept high. Furthermore, the simple, adaptive linear predictor does not incur much computation overhead. Simulation results have demonstrated the accuracy of the proposed prediction algorithm and effectiveness of the bandwidth allocation method.     

Scene-Change Aware Dynamic Bandwidth Allocation for Real-Time VBR Video Transmission Over IEEE 802.15.3 Wireless Home Networks

IEEE 802.15.3, an emerging wireless technology, was designed to provide high-quality multimedia services at home. Dynamic bandwidth allocation for a multimedia connection should be considered in order to achieve higher channel utilization, less buffer and less delay, especially for variable bit rate (VBR) multimedia connections. For real-time VBR videos, the bandwidth requirement should be predicted adaptively for effective channel-time requests. Previously, the adaptive least-mean square (LMS) algorithm with fixed step size was applied to predict channel time requirements due to its simplicity and relatively good performance. However, the performance might degrade when scene changes occurred. In this paper, we modify the variable step-size LMS algorithm and apply it as our predictor (VSSNLMS) so that the prediction errors on scene changes can be effectively reduced. Using the prediction results of VSSNLMS, we propose a dynamic bandwidth-allocation scheme that is scene-change aware and can guarantee the delay bound of real-time VBR videos. Simulation results show that the VSSNLMS predictor is superior to previous LMS-type predictors in performance, and the proposed scheme has better performance in channel utilization, buffer usage, and packet loss     

Fuzzy-based adaptive bandwidth control for loss guarantees

This paper presents the use of adaptive bandwidth control (ABC) for a quantitative packet loss rate guarantee to aggregate traffic in packet switched networks. ABC starts with some initial amount of bandwidth allocated to a queue and adjusts it over time based on online measurements of system states to ensure that the allocated bandwidth is just enough to attain the specified loss requirement. Consequently, no a priori detailed traffic information is required, making ABC more suitable for efficient aggregate quality of service (QoS) provisioning. We propose an ABC algorithm called augmented Fuzzy (A-Fuzzy) control, whereby fuzzy logic control is used to keep an average queue length at an appropriate target value, and the measured packet loss rate is used to augment the standard control to achieve better performance. An extensive simulation study based on both theoretical traffic models and real traffic traces under a wide range of system configurations demonstrates that the A-Fuzzy control itself is highly robust, yields high bandwidth utilization, and is indeed a viable alternative and improvement to static bandwidth allocation (SBA) and existing adaptive bandwidth allocation schemes. Additionally, we develop a simple and efficient measurement-based admission control procedure which limits the amount of input traffic in order to maintain the performance of the A-Fuzzy control at an acceptable level.     

一种基于流量预测的资源动态管理算法

分析了基于有效带宽理论(effectivebandwidththeory)的静态资源分配方案的弊端。在此基础上,提出了一种基于流量预测的资源动态管理算法,并且把资源动态管理算法具体应用到QoS的区分服务(DifferentiatedService)体系中,算法在区分服务网络的边缘路由器上实现。最后,在ns 2的仿真环境下对两种算法进行了比较,试验结果证明无论在丢包率还是链路利用率上,资源动态管理算法都比静态资源分配方案有明显的优势。