Design and implementation of contractual based real-time scheduler for multimedia streaming proxy server

In nowadays World Wide Web topology, it is not difficult to find the presence of proxy servers. They reduce network traffic through the cut down of repetitive information. However, traditional proxy server does not support multimedia streaming. One of the reasons is that general scheduling strategy adopted by most of the traditional proxy servers does not provide real-time support to multimedia services. Based on the concept of contractual scheduling, we have developed a proxy server that supports real-time multimedia applications. Moreover, we developed the group scheduling mechanism to enable processing power transfer between tasks that can hardly be achieved by traditional schedulers. They result in a substantially improved performance particularly when both time-constrained and non-time-constrained processes coexist within the proxy server. In this paper, the design and implementation of this proxy server and the proposed scheduler are detailed. Wai-Kong Cheuk received the B.Eng. (Hons.) and M. Phil. degrees in 1996 and 2001, respectively, from the Hong Kong Polytechnic University, where he is currently pursuing the Ph.D. degree. His main research interests include distributed operating systems and video streaming. Tai-Chiu Hsung (M'93) received the B.Eng. (Hons.) and Ph.D. degrees in electronic and information engineering in 1993 and 1998, respectively, from the Hong Kong Polytechnic University, Hong Kong. In 1999, he joined the Hong Kong Polytechnic University as a Research Fellow. His research interests include wavelet theory and applications, tomography, and fast algorithms. Dr. Hsung is also a member of IEE. Daniel Pak-Kong Lun (M'91) received his B.Sc. (Hons.) degree from the University of Essex, Essex, U.K., and the Ph.D. degree from the Hong Kong Polytechnic University, Hung Hom, Hong Kong, in 1988 and 1991, respectively. He is currently an Associate Professor and the Associate Head of the Department of Electronic and Information Engineering, the Hong Kong Polytechnic University. His research interests include digital signal processing, wavelets, multimedia technology, and Internet technology. Dr. Lun was the Secretary, Treasurer, Vice-Chairman, and Chairman of the IEEE Hong Kong Chapter of Signal Processing in 1994, 1995–1996, 1997–1998, 1999–2000, respectively. He was the Finance Chair of 2003 IEEE International Conference on Acoustics, Speech and Signal Processing, held in Hong Kong, in April 2003. He is a Chartered Engineer and a Corporate member of the IEE.     

A QoS-enhanced intelligent stochastic real-time packet scheduler for multimedia IP traffic

A re-configurable, QoS-enhanced intelligent stochastic real-time optimal fair packet scheduler, QUEST, for IP routers is proposed and investigated. The objective is to maximize the system QoS subject to the constraint that the processor utilization is kept at 100%. All past work on router schedulers for multimedia traffic were of earlier generation, in that they focused on maximizing utilization whereas being QoS-aware but without explicitly maximizing the QoS. Keeping utilization fixed at nearly 100%, QoS is dynamically maximized, thus moving to the next generation. QUEST’s other unique advantages are three-fold. First, it solves the challenging problem of starvation for low priority processes; second, it solves the major bottleneck of Earliest Deadline First scheduler’s failure at heavy traffic loads. Finally, QUEST offers the benefit of arbitrarily pre-programming the process utilization ratio. Three classes of multimedia IP traffic, namely, VoIP, IPTV and HTTP have been considered. Two most important QoS metrics, namely, packet loss rate (PLR) and mean waiting time, are addressed. All claims are supported by discrete event and Monte Carlo simulations. The proposed scheduler outperforms benchmark schedulers and offers 37% improvement in packet loss rate and 23% improvement in mean waiting time over the best competing current scheduler Accuracy-aware EDF. The proposed scheduler was validated in a test-bed platform of a NetFPGA® router and results were observed with Paessler® PRTG network monitor.

     

Tolerating permanent and transient value faults

Transmission faults allow us to reason about permanent and transient value faults in a uniform way. However, all existing solutions to consensus in this model are either in the synchronous system, or require strong conditions for termination, that exclude the case where all messages of a process can be corrupted. In this paper we introduce eventual consistency in order to overcome this limitation. Eventual consistency denotes the existence of rounds in which processes receive the same set of messages. We show how eventually consistent rounds can be simulated from eventually synchronous rounds, and how eventually consistent rounds can be used to solve consensus. Depending on the nature and number of permanent and transient transmission faults, we obtain different conditions on $n$ , the number of processes, in order to solve consensus in our weak model.     

MPLS恢复模型的仿真与实现

根据MPLS故障恢复机制的原理,采用功能强大的网络仿真软件NS-2作为工具,讨论了近年来网络研究的必然趋势--利用容错技术构造高可靠网络系统.通过原理模拟出一种MPLS网络的Global恢复模型,结合平均无故障时间和恢复时间等来验证该模型在网络发生故障时,依旧能保证系统的可靠性和可用性.通过延迟、吞吐量等仿真数据得出,采用适当的压缩算法能够加速数据在网络上的传送,在保证网络传输的稳定性和可靠性的同时,可供其它同类网络故障恢复仿真参考,也可以直接应用到实际网络中.     

工业无线传感器网络节点通信中的瞬时故障恢复

无线传感器网络在工业领域应用广泛,由于电磁干扰、电源突然中断、软件突发错误等瞬时故障导致系统失效,影响系统安全,其控制和恢复在涉及安全的领域越发得到重视。考虑到瞬时故障在网络的多个层次可能都有发生,提出了一种三层故障处理机制,在芯片级采用硬件逻辑调整、在节点级采用重传和跳频、在系统级采用冗余路由等措施进行故障控制和恢复。实验结果表明,采用三层故障处理机制后,网络的丢包率和端对端的时延有效降低,节点通信的可靠性和安全性得到有效的提高。     

A fault-tolerant real-time multiprocessor with a built-in recovery mechanism

The architecture of a fault-tolerant multiprocessor with a rollback recovery mechanism is described. Fault-tolerance is attained owing to restarts of faulty processes of computations or their definite parts after detecting failures. An error occurring during the interaction of some processes leads to the multistep reconstruction of the entire computational process. An estimate of the efficiency of the proposed fault-tolerant technology is given.Translated from Kibernetika i Sistemnyi Analiz, No. 5, pp. 169–176, September–October 2004.     

改进的实时反走样透视阴影图算法及实现

为解决透视阴影图算法中,物体被非线性比例导致愈加明显的自阴影或表面波纹现象,提出一种基于GPU的实时反走样透视阴影图改进算法。该算法结合透视阴影图算法以及D.Weiskopf的dual depth layers算法,通过采用GPU深度剥离技术采样场景的双层深度值信息,并引入自适应偏移量zbias来计算场景的深度偏移量。该算法采用C语言实现,同时使用GPU顶点渲染器和像素渲染器编程有效避免程序复杂度。实验结果表明,该改进算法较好解决了透视阴影图的自阴影问题,提高了渲染阴影质量。     

多核对分区操作系统影响研究

分区操作系统是综合化航空电子领域中的核心技术。随着单核性能极限的到来,处理器结构向着多核发展。将两者结合起来,在多核分区操作系统的基础上研究分析多核处理器结构为分区操作系统带来的影响。经分析实验数据得出多核处理器结构在多核处理器中共享Cache结构和内核中临界资源并发访问两方面对分区操作系统产生影响。     

A decentralized multichannel length transformation algorithm and its parallel implementation for real-time ECG monitoring.

Multichannel algorithms have been developed for more accurate analysis of electrocardiograms (ECGs). Their benefit is the ability to use the information contained in all simultaneously acquired channels. In this paper we present a multichannel version of a nonsyntactic algorithm, based on length transformation. The proposed algorithm uses a decentralized schema for combining the results derived from each individual lead, instead of a global/centralized one (a spatial vector approach). Its performance was evaluated using the CSE database and real ECGs acquired by a 12-lead cardiograph. The results are also compared with previous-single-channel and multichannel-versions of the algorithm, showing a better performance. Since a multichannel algorithm is always a time-consuming task, it is rarely used in real-time monitoring systems. Motivated by this observation, we designed a parallel implementation of the proposed algorithm and tested its ability to be used in such systems.     

Cost analysis of recovery block scheme and its implementation issues

In this paper, a cost analysis of recovery block scheme has been presented. This study provides us the selection criterion for alternates and the software granularity under perfect acceptance tests. Two performance evaluation measures: a) cost-reliability index (CRI); b) cost of failure (COF) are studied and compared. CRI is shown to be a move restricted measure than COF. An experimental study has been carried out to supplement the analysis. Efficient placement of recovery blocks and the design of alternates has been discussed with reference to real-time applications.This work has been carried out under contract DOT-RC-92031.     

基于FPGA的实时操作系统调度器硬件化设计与实现

采用VHDL语言设计适用于硬件化的实时操作系统调度器,基于FPGA使用组合电路和时序电路完成了系统内核调度器的搭建。该调度器在Variable Multi-Processing (VMP)运行模式下,可在一个系统时钟之内完成多核处理器的任务调度,并可同时管理不同芯片系统,完成异构处理器系统的统一调度。由于该调度器是采用门电路搭建而成的,存在于芯片系统之外,因此具有极高的稳定性和系统性能,并且可以根据需要进行裁剪。     

实时交互式三维脸部表情动画研究及其实现

根据人脸的生理结构特点,使用分块造型技术进行脸部建模,提出了一个基于"脸型特征"和"五官特征"的参数化肌肉模型,通过模型上控制顶点的属性值来控制脸部形成不同的表情,并利用MAYA MEL语言实现了一个实时交互操作界面.这使得对脸部表情的研究更加方便、灵活,建模及其动画化也更加逼真、实用.     

A real-time virtual machine implementation for small microcontrollers

A way to host a full general purpose virtual machine (VM) interpreter on a very small microcontroller platform is described. This machine provides a comprehensive set of general and enhanced functionality efficiently by abstracting the VM instruction set. Measurements were made on the execution of software programs in the virtual machine while running on the target platform in order to demonstrate the machine??s capabilities. Additionally, multitasking capabilities were added to the baseline and found to perform efficiently within the VM. The results proved to be satisfactory and demonstrate that a robust virtual machine can be made available for very small embedded platforms based on simple microcontrollers, such as those that are widely found in aerospace applications.     

基于日志的数据恢复及其在Oracle中的实现

在信息系统的工程实践中,数据库出现故障后的数据恢复是一项复杂的技术问题。从事务处理和事务日志的角度阐述了数据恢复的基本方法,并特别指出了实现完全数据恢复的技术途径和实施策略,同时结合Oracle数据库系统解剖了一个典型的数据恢复范例。研究结果表明,利用事务日志可以实现无数据丢失的完全恢复。     

A cyclic MAC scheduler for collecting data from heterogeneous sensors

Many wireless sensor networks applications, e.g., structural health monitoring (SHM), require the sensors to construct a multihop network to collect the environmental data in real-time. These sensors generally generate sensing data in fixed rates, so their transmission schedules can be deterministically listed. Time division multiple access (TDMA) is especially appropriate for these applications because it can prevent radio interference, thereby reducing the transmission power and maximizing wireless spectrum reuse. However, to reserve sufficient bandwidths on distinct links of a heterogeneous WSN, a complex TDMA schedule is necessary, and a sensor node might need to keep a large TDMA schedule table in its tiny memory. To prevent a large size TDMA schedule table, this paper proposes a CyclicMAC scheduler that assigns each node a temporal transmission pattern which is merely parameterized by period and phase. The CyclicMAC scheduler determines the period to satisfy the bandwidth requirement of the node, and adjusts the phase to achieve collision-freeness and reduce the end-to-end latency as well. The end-to-end latency of the resulting schedule is proven to be optimal if the wireless links only interfere with their parent link and sibling links. As far as we know, CyclicMAC is the first that simultaneously addresses the three design issues of TDMA scheduling, which satisfies heterogeneous bandwidth requirements, minimizing schedule table size, and reducing end-to-end latency, for multihop wireless sensor networks.     

A framework for real-time implementation of low-dimensional parameterized NMPC

In this paper, a novel approach is proposed to implement low-dimensional parameterized Nonlinear Model Predictive Control (NMPC) schemes for systems showing fast dynamics. The proposed scheme is based on distributing the reconstruction of the cost function over the real lifetime of the controlled system. The framework is particularly suitable for NMPC formulations that use low dimensional control parametrization. The concrete example of a Planar Vertical Take-Off and Landing (PVTOL) aircraft stabilization problem is used to illustrate the efficiency of the proposed formulation.     

A minimized makespan scheduler with multiple factors for Grid computing systems

Most scheduling heuristics applied to Heterogeneous Computing (HC) focus on the search of a minimum makespan, instead of the reduction of cost. However, relevant studies presume that HC is based on high-speed bandwidth and communication time has ignored. Furthermore, in response to the appeal for a user-pay policy, when a user submits a job to a Grid environment for computation each implementation of a job would be charged. Therefore, the Apparent Tardiness Cost Setups-Minimum Completion Time (ATCS-MCT) scheduling heuristic considers both makespan and cost, and it composes of execution time, communication time, weight and deadline factors. This study simulates experiments in a dynamic environment, due to the nature of Grid computing being dynamic. The ATCS-MCT is compared to frequent solutions by five scheduling heuristics. This study indicates that the ATCS-MCT achieves a similarly smaller makespan, and lower cost than Minimum Completion Time (MCT) scheduling heuristic, which is the benchmark of on-line mapping.     

Color tracking with contextual switching: real-time implementation on CPU

Journal of Real-Time Image Processing - The paper proposes contributions for mean-shift (MS) and covariance tracking (CT), and makes these two complementary methods cooperate. While MS runs fast...