Network-Supported Layered Multicast Transport Control for Streaming Media

Multicast is very efficient in distributing a large volume of data to multiple receivers over the Internet. Layered multicast helps solve the heterogeneity problem in multicast delivery. Extensive work has been done in the area of layered multicast, for both congestion control and error control. In this paper, we focus on network-supported protocols for streaming media. Most of the existing work solves the congestion control and error control problems separately and does not give an integrated efficient solution. In this paper, after reviewing related work, we introduce our proposed protocols, namely, router-assisted layered multicast (RALM) and router-assisted layered FEC (RALF). The former is a congestion control protocol, whereas the latter is an error control protocol. They work under the same framework and provide an integrated solution. We also extend RALM to RALM-II, which is compatible with transmission control protocol (TCP) traffic. We analyze the complexity of the proposed protocols in the network and investigate their performance through simulations. We show that our solution achieves significant performance gains with reasonable additional complexity.     

Multi-resolution Layered Coding for Real-Time Image Transmission: Architectural and Error Control Considerations

We examine the rationale for and systems aspects of using layered coding for the transmission of images and video over heterogeneous communication networks. We advocate multi-resolution layered coding (MLC) and present architectural alternatives that can support it within the scope of existing standards and technologies. Since the premise of layered coding is controlled loss, the issues of error control and concealment are central. We demonstrate that MLC exhibits good error tolerance, effectively compensating for errors in situations where traditional error concealment schemes, based on the interpolation of pixels in adjacent blocks, are ineffective. In particular, MLC yields a higher peak signal-to-noise ratio (PSNR) than two-layer coding when packet loss occurs in the base layer. Finally, we show that MLC can effectively exploit efficient network error control strategies which distribute redundancy non-uniformly and provide unequal levels of protection across layers.     

A Continuous Leader-following Consensus Control Strategy for a Class of Uncertain Multi-agent Systems

In this paper, we study the robust leader-following consensus problem for a class of multi-agent systems with unknown nonlinear dynamics and unknown but bounded disturbances. The control input of the leader agent is nonzero and not available to any follower agent. We first consider a class of high order chain integrator-type multi-agent systems. By employing the robust integral of the sign of the error technique, a continuous distributed control law is constructed using local information obtained from neighboring agents. Using Lyapunov analysis theory, we show that under a connected undirected information communication topology, the proposed protocol achieves semiglobal leader-following consensus. We then extend the approach to a class of more general uncertain multiagent systems. A numerical example is given to verify our proposed protocol.      

Error control for receiver-driven layered multicast of audio andvideo

We consider the problem of error control for receiver-driven layered multicast of audio and video over the Internet. The sender injects into the network multiple source layers and multiple channel coding (parity) layers, some of which are delayed relative to the source, Each receiver subscribes to the number of source layers and the number of parity layers that optimizes the receiver's quality for its available bandwidth and packet loss probability. We augment this layered FEC system with layered pseudo-ARQ. Although feedback is normally problematic in broadcast situations, ARQ can be simulated by having the receivers subscribe and unsubscribe to the delayed parity layers to receive missing information. This pseudo-ARQ scheme avoids an implosion of repeat requests at the sender and is scalable to an unlimited number of receivers, We show gains of 4-18 dB on channels with 20% loss over systems without error control and additional gains of 1-13 dB when FEC is augmented by pseudo-ARQ in a hybrid system, Optimal error control in the hybrid system is achieved by an optimal policy for a Markov decision process     

The Path-of-Probability Algorithm for Steering and Feedback Control of Flexible Needles

In this paper we develop a new framework for path planning of flexible needles with bevel tips. Based on a stochastic model of needle steering, the probability density function for the needle tip pose is approximated as a Gaussian. The means and covariances are estimated using an error propagation algorithm which has second order accuracy. Then we adapt the path-of-probability (POP) algorithm to path planning of flexible needles with bevel tips. We demonstrate how our planning algorithm can be used for feedback control of flexible needles. We also derive a closed-form solution for the port placement problem for finding good insertion locations for flexible needles in the case when there are no obstacles. Furthermore, we propose a new method using reference splines with the POP algorithm to solve the path planning problem for flexible needles in more general cases that include obstacles.     

实时视频传输的反馈拥塞控制策略

提出了RTP/UDP/IP的视频实时传输体系结构。采用基于实时传输协议（RTP）和实时传输控制协议（RTCP）的反馈拥塞控制算法，控制发送端视频编码器输出的比特率，以使得整个基于IP的网络视频传输系统既能充分利用网络带宽又不引起网络拥塞，从而减少时延，降低丢包率，为视频数据的接收者提供一个较好的图象质量。     

Solutions to the combined sensitivity and complementary sensitivityproblem in control systems

In a recent paper, a set of necessary and sufficient conditions for the existence of solutions to the combined sensitivity and complementary sensitivity (CSCS) problem in control systems was given. However, a practical method for constructing solutions to this problem was not presented. The computation procedure that was proposed involves constructing a sequence of rational functions to approximate an irrational function and may result in complicated high-order controllers. In this paper, we consider the synthesis aspect of the CSCS problem and derive an algorithm for constructing controllers that solve our CSCS problem in a simple manner. Moreover, an error in the closed-form solution of the Nevanlinna-Pick interpolation problem is revealed     

基于AVS-M的3G视频流媒体传输与差错控制

分析了以RTP包传输视频数据，并以RTCP包进行控制的传输机制。根据3GPP规范和相关协议，设计实现了针对AVS-M码流的负载包、重传包和六种不同的RTCP包，包括引入的FB包。建立了一个包传输和控制系统。在立即反馈的基础上提出了一种基于分层重传的差错控制机制。     

基于AVS M的3G视频流媒体传输与差错控制*

分析了以RTP包传输视频数据,并以RTCP包进行控制的传输机制。根据3GPP规范和相关协议,设计实现了针对AVSM码流的负载包、重传包和六种不同的RTCP包,包括引入的FB包。建立了一个包传输和控制系统。在立即反馈的基础上提出了一种基于分层重传的差错控制机制。     

An efficient routing scheme with optimal power control in wireless multi-hop sensor networks

Power consumption is a critical problem in providing multimedia communications among wireless sensor nodes (WSNs). To reduce power consumption and satisfying QoS requirements, in this paper, we propose an efficient routing scheme with optimal power management and on-demand quality control for WSNs. Two cost functions are developed to minimize the transmitting power and maximize the link quality under the constraint that an end-to-end frame error probability should be met. The heuristic problem of minimizing power consumption under frame error constraints is formulated and resolved with a closed-form expression. With this closed-form expression, we can determine an optimal route rapidly by calculating the power requirement for each sensor node. Finally, our analytical results indicate that the proposed scheme is superior to a previous work with the same constraint and is also comparable to the results obtained from a heuristic simulation.     

一种基于组播路由的拥塞控制改进算法

本文融合了网络层组播与应用层组播以及隧道技术,在可靠组播差错恢复算法的基础上引入拥塞控制,使组播的一些中间接收者充当虚拟组播源,在拥塞发生处进行灵活的速率调节,从而灵活有效地解决异构网络中组播的拥塞控制问题,通过仿真试验对组播拥塞控制算法的评价指标进行有效的验证。     

Multiple TFRC Connections Based Rate Control for Wireless Networks

Rate control is an important issue in video streaming applications for both wired and wireless networks. A widely accepted rate control method in wired networks is equation based rate control , in which the TCP friendly rate is determined as a function of packet loss rate, round trip time and packet size. This approach, also known as TCP friendly rate control (TFRC), assumes that packet loss in wired networks is primarily due to congestion, and as such is not applicable to wireless networks in which the bulk of packet loss is due to error at the physical layer. In this paper, we propose multiple TFRC connections as an end-to-end rate control solution for wireless video streaming. We show that this approach not only avoids modifications to the network infrastructure or network protocol, but also results in full utilization of the wireless channel. NS-2 simulations, actual experiments over 1$times$RTT CDMA wireless data network, and and video streaming simulations using traces from the actual experiments, are carried out to validate, and characterize the performance of our proposed approach.     

Risk-sensitive control for a class of nonlinear systems with multiplicative noise

In this paper, we consider the problem of optimal control for a class of nonlinear stochastic systems with multiplicative noise. The nonlinearity consists of quadratic terms in the state and control variables. The optimality criteria are of a risk-sensitive and generalised risk-sensitive type. The optimal control is found in an explicit closed-form by the completion of squares and the change of measure methods. As applications, we outline two special cases of our results. We show that a subset of the class of models which we consider leads to a generalised quadratic–affine term structure model (QATSM) for interest rates. We also demonstrate how our results lead to generalisation of exponential utility as a criterion in optimal investment.     

Internet多媒体分层组播JSCC差错控制率失真优化

针对Internet多媒体群组通信中同时存在的带宽异构性和包丢失率异构性，文中将分层组播和接收者驱动的思想扩展到FEC差错控制中，提出一种分层FEC组播差错控制方法LM-FEC．LM-FEC通过不同的组播组发送信源编码层和各信源层的FEC校验数据，为接收者根据信道带宽和数据包丢失率实施差错控制提供更加灵活的选择．文中用FH-MDP模型描述接收者行为，通过JSCC率失真优化确定编码层内和编码层间的速率分配，JSCC率失真优化采用变量替换和动态规划算法求解．实验表明，该文提出的差错控制方法能够有效改善重建多媒体信号的回放质量．     

基于Round-Robin协议网络化系统的故障检测

针对基于Round-Robin通信协议网络化控制系统的鲁棒故障检测问题，考虑传感器饱和以及外部干扰，提出了一种通信协议约束下故障检测滤波器的设计方法.利用李亚谱诺夫稳定性理论和线性矩阵不等式技术得到故障检测滤波器存在的充分条件，通过求解具有凸约束的优化问题得到最优滤波器参数.所设计的故障检测滤波器不仅能够确保滤波误差系统均方渐进稳定且有较强的扰动抑制能力.通过数值仿真和DTS200三容水箱液体渗漏检测实验验证了该方法的有效性.     

组播错误控制技术

1.引言传统的点点通信(unicast)和广播通信(broadcast)是两种主要的通信方式,但随着Internet的日益普及、带宽的不断提高,利用IP组播技术在Internet上建立了虚拟的multicast backbone(Mbone),其上的点到多点通信的应用和各种工具也相继产生。人们可方便地在Mbone上举行远程视频会议,股票实时行情的分发,参与远程教育等。但可靠的组播协议的研究相对传统的点点协议而言,在错误控制、路由、流量控制、可伸缩性都具有其独有的特点,其复杂度也大得多。就错误控制和流量控制而言,传统的点点通信只涉及收发双     

Control Mechanisms for Error-Resilient MPEG-2 Video Communications over ATM Networks

The design of digital video communications systems is a very active research area. Due to the stringent requirement of video and characteristics of networking technologies, the provisioning of control mechanisms guaranteeing a certain level of service is essential for the success of distributed video applications. In this paper, we study the use of different schemes for the robust transmission of MPEG-2 video over ATM networks. We compare error-resilience performance of two data-partitioning schemes for MPEG-2 bit stream transmitted over ATM networks where two layers of priority traffic are supported with different cell discarding schemes. The effectiveness of the different control mechanisms is quantitatively evaluated in terms of cells loss rates, end-to-end delay and cell loss distributions. Our results show that the use of control mechanisms at various levels of the protocol stack is essential for the deployment of error resilient video applications.     

Optimal Control of Underactuated Nonholonomic Mechanical Systems

In this paper, we use an affine connection formulation to study an optimal control problem for a class of nonholonomic, underactuated mechanical systems. In particular, we aim to minimize the norm-squared of the control input to move the system from an initial to a terminal state. We consider systems evolving on general manifolds. The class of nonholonomic systems we study in this paper includes, in particular, wheeled-type vehicles, which are important for many robotic locomotion systems. The two special aspects of this optimal control problem are the nonholonomic constraints and underactuation. Nonholonomic constraints restrict the evolution of the system to a distribution on the manifold. The nonholonomic connection is used to express the constrained equations of motion. Many robotic systems are underactuated since control inputs are usually applied through the robot's internal configuration space only. While we do not consider symmetries with respect to group actions in this paper, the fact that the system is underactuated is taken into account in our problem formulation. This allows one to compute reaction forces due to any inputs applied in directions orthogonal to the constraint distribution. We illustrate our ideas by considering a simple example on a three-dimensional manifold, including obstacle avoidance using the method of navigation functions.     

Joint power-playout control for media streaming over wireless links

Media streaming applications over wireless links face various challenges, due to both the nature of the wireless channel and the stringent delivery requirements of media traffic. In this paper, we seek to improve the performance of media streaming over an interference-limited wireless link, by using appropriate transmission and playout control. In particular, we choose both the power at the transmitter and the playout scheduling at the receiver, so as to minimize the power consumption and maximize the media playout quality. We formulate the problem using a dynamic programming approach, and study the structural properties of the optimal solution. We further develop a justified, low-complexity heuristic that achieves significant performance gain over benchmark systems. In particular, our joint power-playout heuristic outperforms: 1) the optimal power control policy in the regime where power is most important and 2) the optimal playout control policy in the regime where media (playout) quality is most important; furthermore, this heuristic has only a slight performance loss as compared to the optimal joint power-playout control policy over the entire range of the investigation.     

Feedback linearizability and explicit integrator forwarding controllers for classes of feedforward systems

We identify a class of feedforward nonlinear systems that are linearizable by a coordinate change. Then we develop explicit expressions for the Lyapunov-based integrator forwarding recursive procedure of Sepulchre, Jankovic, and Kokotovic, which has its roots in a coordinate transformation proposed by Mazenc and Praly. The explicit expressions that we develop allow us to also find closed-form control laws for several classes of systems that are not feedback linearizable, including some that are in the feedforward form and others that are in what we refer to as the "block-feedforward" form. Performance advantages of Lyapunov-based forwarding controllers over nested saturation controllers have been well illustrated in the literature on examples. The analytical expressions for the Lyapunov functions and the control laws allow us to give quantitative performance bounds.