Synchronization properties in multimedia systems

Multimedia is defined as the integrated generation, representation, processing, storage, and dissemination of independent machine-processable information expressed in multiple time-dependent and time-independent media such as data, graphics, drawings, voice, audio, and video. The characteristics of synchronization mechanisms desirable for central and distributed multimedia systems are addressed. The concept of multimedia objects as components of an object-based model for a multimedia system is introduced. The essential new synchronization requirement is restricted blocking together with synchronization features covering real-time aspects. Existing synchronization mechanisms can be altered or new ones defined to meet these requirements     

A Distributed Instrument for Performance Analysis of Real-Time Ethernet Networks

Ethernet technology is widely used in real-time industrial automation. Thanks to real-time Ethernet (RTE) protocols, defined in IEC61784-2 standard, new top-performance automation solutions can be created. Such systems may have communication cycle time down to tens of mus and cycle jitter less than 1 mus, making network testing and debugging very critical. Existing network and protocol analyzers can perform detailed local analysis, but characterization of high-performance RTE systems requires measurement of transmission delays and these instruments cannot be adequately synchronized among them to realize a distributed measurement network. This paper introduces a new low-cost distributed measurement instrument to measure timing characteristics of RTE nodes (end-to-end delays, synchronization, etc.). The proposed instrument has multiple FPGA-based probes that allow for simultaneous/synchronized logging on different place of the target RTE network. A PC-based "monitor station" stores all the data, ready for further elaboration. Architecture details are discussed, a prototype has been realized, and some experimental results are presented. For instance, synchronization accuracy between probes is below 100 ns.     

RTX在实时控制系统中的应用

RTX在Windows平台的基础上提供了一个实时子系统,实现了确定性的实时线程调度、实时环境与Windows环境之间的进程间通讯机制以及只在特定的实时操作系统中才有的对Windows系统的扩展特性。主要介绍了RTX下驱动程序的开发以及RTX与Windows之间的IPC通讯。     

基于FPGA的SPI串行接口实时以太网实现

工业以太网,从控制网络的角度来看,属于一种新型的现场控制总线,正处于不断完善和发展中。基于ENC28J60芯片的独立以太网控制器接口通信系统,不仅能实现嵌入式控制系统与以太网的互联,而且能够实时可靠地传输数据,其中包括新型实时以太网通信的原理、串行接口SPI的软硬件设计、TCP/IP协议的选择及参数设置、TCP/IP通信测试。     

Scalable,hierarchical, Ethernet transport network architecture (HETNA)

Ethernet technology is not inherently scalable, and yet, Ethernet dominates LANs, and recently has diffused to access, aggregation networks, and MANs. Ethernet is even considered for transport networks in the backbone. Many solutions from IEEE, IETF, and MEF are considered for enabling Ethernet beyond LANs and bridged LANs. In this paper we offer HETNA, a hierarchical Ethernet forwarding, which is compatible with legacy networks used by enterprises, carriers, and backbone networks, and provides scalability, mobility, protection, multicasting, and QoS support to intra- and inter-domain networks in an efficient forwarding manner. The suggested architecture can handle streaming, real-time, multicasting, and other applications as well as various addressing mechanisms (e.g., IP or URI addressing). Both connection-oriented transport services and connectionless-oriented services are possible in the suggested architecture. This architecture was simulated and prototyped, showing significant improvements over regular Ethernet in terms of buffers and control messages that enable this network to function.     

Selective congestion control for mixed-critical networks-on-chip

Modern Networks-on-Chip (NoCs) must accommodate a diversity of temporal requirements, e.g., providing guarantees for real-time senders while reducing adverse performance impact on best-effort (BE) traffic. In this work, we propose a protocol-based adaptive congestion control. By selectively detouring real-time or BE traffic (i.e load balancing) and dynamic throttling of BE, we allow improving the NoC performance without costly hardware extensions. The introduced method offers safe and efficient integration of mixed-critical workloads through the coupling of flow control mechanisms with the path selection based on the current NoC state. The requested real-time reliability of the network is achieved through a predictable synchronization with control messages supported by a formal analysis and an experimental evaluation.     

基于以太网的电力调度信息传输的开发

针对电力调度系统远程通信实时性传输的要求,分析了当前传统的电力调度通信系统的传输方法,以及以太网通信协议在信息远程传输的应用,重点结合电力系统应用的实际要求,给出了以太网在电力调度信息传输系统中的应用,从以太网应用模式、以太网通信模块设计以及数据传输机制三个方面进行了分析研究,对于进一步提高电力调度系统信息传输的实时性具有一定借鉴意义。     

Partitioned k-Exclusion Real-Time Locking Protocol Motivated by Multicore Multi-GPU Systems

Graphic processing units (GPUs) have been widely recognized as cost-efficient co-processors with acceptable size, weight, and power consumption. However, adopting GPUs in real-time systems is still challenging, due to the lack in framework for real-time analysis. In order to guarantee real-time requirements while maintaining system utilization in modern heterogeneous systems, such as multicore multi-GPU systems, a novel suspension-based k-exclusion real-time locking protocol and the associated suspension-aware schedulability analysis are proposed. The proposed protocol provides a synchronization framework that enables multiple GPUs to be efficiently integrated in multicore real-time systems. Comparative evaluations show that the proposed methods improve upon the existing work in terms of schedulability.     

Performance of synchronized master-slave closed-loop control of AC electric drives using real time motion over ethernet (RTMoE)

Multi-motor driving servomechanisms are widely used in modern industry for high-performance applications involving synchronized control of position, speed, acceleration and deceleration. Several synchronous control schemes have been developed to achieve good speed or position tracking regardless of various uncertainties and load torque perturbations. However, these solutions have some disadvantages, namely the costs associated with the necessary interfaces to transmit hardware synchronization signals between multiple drives and difficulty to integrate other tools and communication networks. Recently, Industrial Ethernet network-based control systems are becoming increasingly popular for industrial applications and factory automation. To overcome some of these disadvantages this paper proposes an approach that uses a real-time Ethernet applied to a dual-motor master-slave synchronization system, without introducing significant degradation of speed or position in the application performance. With this solution the position reference from the master encoder is transmitted by the real-time Ethernet instead of the classic hardware interface. This allows the integration of different tools and the explore of other functionalities of electric drives. The performance of the proposed solution was tested using industrial equipment through several practical experiments. It was also compared with an existing solution based on hardware interfaces, to identify advantages, limitations and cost savings of using real-time Ethernet networks solutions in synchronized AC electric drives.     

机载合成孔径雷达实时数字成象处理器的整机控制系统

本文对机载合成孔径雷达实时数字成象处理器整机控制系统的系统组成及技术特点进行了研究,扼要阐述了运行在整机控制系统中的实吋操作系统的通讯、任务调度等机制。本文讨论了在实时操作系统中整机控制系统多任务的调度、通讯及多处理器之间的通讯、数据传递等问题,以及实时系统中人机对话的问题,并提出了解决问题的方法和系统的控制流程。     

Architecture of a comprehensive radiologic imaging network

An emerging concept in picture archiving and communication systems (PACS) is the PACS infrastructure. The critical components in this infrastructure are communication systems, cluster controller, database integration, fault-tolerant design, and systems integration software. The architecture of a comprehensive communication system within this infrastructure, which will support a digital-based radiology operation, is described. This communication network consists of a real-time analog video and digital components. The video network utilizes broadband and fiber-optic communication technologies. The digital communication is based on a three-tiered network integrating Ethernet, FDDI, and Ultranet technologies. The digital network uses the standard TCP/IP protocol and has a fault-tolerant design. Both components have been in clinical operation since the summer of 1991     

Timeliness of real-time IP communication in switched industrial Ethernet networks

Through several giant evolutionary steps, Ethernet has become an almost ubiquitous technology for communication. Being versatile enough to be employed in new and various fields of application, it is now making inroads in factories. However, automated systems are different from many other applications of Ethernet,first and foremost because they require the network technology to deliver real-time performance. In the present study, a number of critical aspects of Ethernet, usually referred to as an Industrial Ethernet, are examined. More specifically, there is a focus on the application-to-application delay and jitter characteristics of such networks, when using Internet protocols such as UDP and TCP. It is demonstrated how important it is to take control of the latency in the station nodes, since the main communication delays occur inside the nodes, and different solutions are presented for controlling these delays. In particular, a priority-based protocol stack is assessed. The results show that real-time, Ethernet-based IP communication is now adequate even for demanding automated applications. In this paper, substation automation (power distribution) is used as an example of a demanding automation system.     

An integrated service architecture for managing capital marketsystems

This article studies current developments and trends in the area of capital market systems. In particular, it defines the trading lifecycle and the activities associated with it. The article then investigates opportunities for the integration of legacy systems and existing communication protocols through distributed integrated services that correspond to established business processes. These integrated services link to basic services such as an exchange, a settlement, or a registry service. Examples of such integrated services include pre-trade services (e.g., analytics) or post-trade services (e.g., surveillance). The article then presents the various levels of integration in capital market systems and discusses the standards in place. It establishes that most interactions occur at a low level of abstraction such as the network (e.g., TCP/IP), data format (e.g., FIX, XML), and middleware levels (e.g., CORBA). Finally, the article discusses a software development methodology based on the use of design patterns. These design patterns address the essential aspects of managing integrated services in a technology-independent fashion. These aspects are service wrapping, service composition, service contracting, service discovery, and service execution. The objective of the methodology is to facilitate the rapid development of new integrated services that correspond to emerging business opportunities     

Innovation of EtherCAT adaptive synchronization control in embedded CNC

EtherCAT is a real-time Ethernet protocol and has been widely used in the field of motion control owing to its high speed (100 or 1000 Mbps), low processor occupancy, and good synchronization performance in slaves. However, the master–slave synchronization method is blank in the EtherCAT protocol. The study proposes a novel master–slave synchronization method that relies on the stable sync0 of reference slave by adjusting the trigger moment of master interpolation period to settle packet loss caused by EtherCAT master–slave un-synchronization, adaptively and dynamically. Furthermore, the proposed method improved EtherCAT to a whole new level, indicating that the EtherCAT master no longer depended on the real-time operating system (RTOS). In addition, a synchronization predictive compensation mechanism was adopted to eliminate the compensation lag defect of existing synchronization methods. Compared with conventional studies, the synchronization method improved compensation efficiency, settled inaccurate compensation with evaluation derived from different working frequencies, and eliminated accumulative error in clock. Finally, the proposed method added almost no computation and communication load and only required eight or 16 bytes to modify the EtherCAT frame coding in the interpolation period. Experiments were carried out on machine tools to demonstrate the advantage of the proposed method in improving the synchronization performance, with an average communication jitter of only 32–71 ns.     

Hydrogel Patterning with Catechol Enables Networked Electron Flow

Reduction–oxidation (redox) reactions provide a distinct modality for biological communication that is fundamentally different from the more-familiar ion-based electrical modality. Biology uses these two modalities for communication through different systems (immune versus nervous), and uses different mechanisms to control the flow of the charge carriers: the flow of soluble ions is controlled using structural barriers (i.e., membranes) and gates (e.g., membrane-spanning protein channels), while the flow of insoluble electrons is controlled using redox-reaction networks. Here, a simple electrochemical approach to pattern catechols onto a flexible polysaccharide hydrogel is reported and it is demonstrated that the patterned catechol regions serve as nodes for the mediated flow of electrons through redox reactions. Electron flow through this node involves the switching of binary redox states (oxidized and reduced) and this node's redox state can be detected (i.e., “read”) by passively observing its optical absorbance, or actively switching its redox-state electrochemically. Further, this catechol node can be switched through biological mechanisms, and this enables the fabricated catechol node to be embedded within biochemical redox reaction networks to facilitate the spanning of bio-electronic communication. Thus, it is envisioned that catechols can emerge as a molecular equivalent to a transistor for miniaturize-able, deployable and sustainable redox-linked bioelectronics.     

Design and analysis of RT-Ring: a protocol for supporting real-time communications

Distributed applications with quality of service (QoS) requirements are more and more used in several areas (e.g., automated factory networks, embedded systems, conferencing systems). These applications produce a type of traffic with hard timing requirements, i.e., transmissions must be completed within specified deadlines. To handle these transmissions, the communication system must use real-time protocols to provide a communication service that is able to satisfy the QoS requirements of the distributed applications. In this paper, the authors propose a new real-time protocol, called RT-Ring, able to support transmissions of both real-time and generic traffic over a ring network. RT-Ring provides both network guarantees and high network resource utilization, while ensuring the compatibility with the emerging differentiated service architectures. Network guarantees are fully proved and high network utilization is highlighted by a comparative study with the FDDI protocol. This comparison shows that RT-Ring network capacities are greater than the corresponding FDDI capacities. In fact, by assuming the FDDI frames with a length equal to the RT-Ring slot size and by using the same traffic load the authors show that the capacities of FDDI are equal to the lower bound capacities of RT-Ring.     

Fast synchronization method for CDMA communication systems

The synchronization phase of a code division multiple access communication system might pose a limitation on the performance of the system, since unlike other communication systems it is required to obtain the state (i.e., sequence phase) of a linear feedback shift register (LFSR). Usually the state is obtained by using a brute force exhaustive search over all possibilities, which might be a computationally demanding task. In this paper, we suggest a new method for LFSR sequence phase acquisition. Our method is suitable for practical systems in which an unknown frequency drift may be present. Simulation results for the IS-95/CDMA-2000 standard show a dramatic reduction in the time required to acquire synchronization when using the new algorithm compared to the standard synchronization method     

信息物理系统的发展趋势分析

信息物理系统(cyber physical system,CPS)是在环境感知的基础上,融合计算、通信和控制能力的网络化物理设备系统,通过计算和物理进程相互影响的反馈循环,实现现实世界与虚拟世界的相互协同和交互,以增加或扩展新的功能,提供实时感知、动态控制和信息反馈等服务。本文围绕CPS的核心概念,深入探讨CPS的内涵,剖析当前CPS研究与发展所面临的巨大挑战,重点探寻其重要的科学基础和关键技术,展望未来CPS研究与发展的新趋势。     

Hardware Acceleration for Conditional State-Based Communication Scheduling on Real-Time Ethernet

Distributed real-time applications implement distributed applications with timeliness requirements. Such systems require a deterministic communication medium with bounded communication delays. Ethernet is a widely used commodity network with many appliances and network components and represents a natural fit for real-time application; unfortunately, standard Ethernet provides no bounded communication delays.