Content-based deep communication control for networked control system

In smart cities, the networked control system plays a significant role in transportation systems, power stations or other critical infrastructures, and it is facing many security issues. From this point, this paper proposes a content-based deep communication control approach to guarantee its security. Based on the layer architecture, this approach analyzes the interactive content in depth according to different industrial communication protocols, and implements the access control between two distinct enclaves. For OPC Classic, we acquire the dynamic port provided by OPC server, and open a new connection belonging to this port; for Modbus/TCP, we not only analyze the ordinary function codes and addresses, but also check the register or coil values by using the multi-bit Trie-tree matching algorithm. Besides, the white-listing strategy is introduced to satisfy the special requirements of industrial communication. Our experiment results show that, on the one hand the proposed approach provides OPC and Modbus/TCP defenses in depth; on the other hand it has less than 1 ms forwarding latency and 0 packet loss rate when the rule number reaches 200, and all these meet the availability requirements in the networked control system. In particular, this approach has been successfully applied in several real-world petrochemical control systems.     

A communication architecture for spontaneous systems

In this article a communication architecture concept for spontaneous systems is provided. The concept integrates application-level spontaneous group communication and ad hoc networking together. A service gateway is applied as a key architecture element to connect multiple technologies and networks together. A set of methods to enable plug and play, addressing and mobility, peer-to-peer connectivity, and use of services is provided. Finally, the provided methods are discussed based on the realized research experiments.     

Network architecture and communication protocols for mobile computing

We discuss the design and implementation of network and transport layer protocols for mobile networking. The network architecture used is unique in that it separates the mobile network(s) from fixed networks and provides connectivity between the two via special gateways. These gateways split all transport connections and provide QoS guarantees to mobile users for all their open connections. We provide summaries of our protocols and discuss possible improvements.     

Hypercube-based architecture for high speed communication systems

An implementation is presented of digital demultiplexing and demodulation algorithms for an advanced satellite communication system on a hypercube. The mapping on a hypercube provides the high speed necessary for processing hundreds of single channel per carrier/frequency division multiple access (SCPC/FDMA) voice/data channels. Data demultiplexing and demodulation are parts of the recovery of the transmitted digital data in a MODEM. A demultiplexer comprises a filter bank followed by the computation of FFT. A demodulator primarily consists of circuits to recovery carrier signal, clock frequency and data. The computation of FFT on a hypercube is well established (Hwang and Briggs 1984). Therefore, this paper analyses the filter bank and carrier and data recovery algorithms to find an efficient mapping in a multiprocessor environment connected in a hypercubic configuration. A few models to implement these algorithms on a hypercube are provided. Comparison of the speed-up achieved on a hypercube vrsus that on a sequential computer is provided for the three models.     

An architecture for real-time multimedia communication systems

A multimedia communication system includes both the communication protocols used to transport the real-time data and the distributed computing system (DCS) within which any applications using the protocols must execute. The architecture presented attempts to integrate these communications protocols with the DCS in a smooth fashion in order to ease the writing of multimedia applications. Two issues are identified as being essential to the success of this integration: the synchronization of related real-time data streams, and the management of heterogeneous multimedia hardware. The synchronization problem is tackled by defining explicit synchronization properties at the presentation level and by providing control and synchronization operations within the DCS which operate in terms of these properties. The heterogeneity problems are addressed by separating the data transport semantics (protocols themselves) from the control semantics (protocol interfaces)     

An architecture and protocol for communications satellite constellations regarded as multi-agent systems

This paper presents an architecture for satellites regarded as intercommunicating agents. The architecture is based upon a postmodern paradigm of artificial intelligence in which represented knowledge is regarded as text, inference procedures are regarded as social discourse and decision-making conventions, and the semantics of representations is grounded in the situated behaviour and activity of agents. A particular protocol is described for agent participation in distributed search and retrieval operations conducted as joint activities.     

二阶多智能体系统的有限时间收敛的一致性控制

本文研究了二阶多智能体系统在有限的时间内实现一致性收敛的问题。主要研究对象是多智能体系统,该系统的网络拓扑图是固定的无向强连通网络拓扑结构图,采用一个领导多个跟随的模型,通过设计控制器,对理论结果进行了Lyapunov时间稳定性理论的证明,最终实现了二阶多智能体系统有限时间的一致性控制,并给出了该二阶多智能体系统有限时间内一致性收敛的条件。最后通过计算机对收敛结果进行MATLAB仿真验证,证明此控制器的可行的,能够实现有限时间内的一致性收敛。     

Analysis and simulation methods for performance evaluation of a multiple networked embedded architecture

This paper deals with the modeling and the validation of multiple networked embedded computer systems supporting in-vehicle applications. In this context, the authors developed a modular modeling and simulation technique. This approach allowed the development of reusable component models with clearly defined interfaces. The building of a whole application model is then obtained by the integration of these components, so that model construction and result analysis are made easy. In fact, thanks to the formal definition of components, interfaces, and composition rules, this step is automatically achieved. In the context of the CAROSSE project, we implemented this methodology in the Carosse-Perf tool. Herein, the authors detail the methodology together with its modeling principles and the resulting definition of basic components and interfaces. Finally, they apply it to a case study drawn from a PSA Peugeot-Citroen application.     

基于事件驱动的多智能体系统蜂拥控制

提出一种基于事件驱动的控制策略来研究多智能体系统的蜂拥行为。针对实际系统中相对速度信息难以连续交换的情况,设计了由事件驱动机制触发速度信息交互的控制算法。理论上证明了所设计的事件驱动策略能使系统实现稳定的蜂拥运动同时保持网络的连通性。最后,数值仿真验证了理论结果。     

Smart error-control strategy for low-power communication in wireless networked control system

We consider a Wireless Networked Control System (WNCS) in an indoor environment and discuss the impact of wireless channel characteristics on the stability and performance of wireless feedback control-loop system. The presence of mobile/static obstacles and other radio interferences in indoor space causes random transmission errors and therefore, it becomes challenging to establish timely and reliable communication among distributed WNCS nodes (sensor, controller and actuator). To overcome communication errors in an energy-efficient way, we propose a novel Forward Error Correction (FEC) based smart error control mechanism which at its core employs a cascaded fuzzy inference system. The proposed strategy unifies three heterogeneous metrics, e.g. Signal-to-Noise Ratio, Line-of-Sight/Non-Line-of-Sight detection and packet ACK/NACK information, to accurately estimate the radio links quality and to select an appropriate error correction code. The performance of the proposed approach have been evaluated in simulated environment that includes realistic indoor fading channel model and IEEE 802.15.4 2.4 GHz modulation format for the network nodes. Based on obtained results, we conclude that the proposed smart error control scheme not only offers better trade-off in terms of packet error rate and energy efficiency as compared to static FEC codes and IEEE802.15.4 ARQ (Automatic Repeat-reQuest) mechanism, but also achieves increased stability of WNCS.     

Enabling efficient reprogramming through reduction of executable modules in networked embedded systems

We present a systematic modular design approach for networked embedded systems. We effectively reduce the module file size to enable efficient network reprogramming, while at the same time retain necessary information to maintain module flexibility. We further handle module dependencies in a fine-grained manner, which improves system reliability while keeping the system configuration to its minimum requirement. We have implemented the modular approach based on a micro embedded OS, SenSpire OS, for AVR and MSP430 platforms. The evaluation results show that the proposed SELF module file format is 4.6–7.6 times smaller than the standard ELF format, and is 1.6–2.4 times smaller than the CELF format (a Compact ELF format for the Contiki OS). SELF retains necessary information to enable flexible modular programming and inter-module communications. We have further developed a long-term energy efficiency model to explore the tradeoffs of different reprogramming approaches.     

Admissible short-time uncertainty in networked control systems

Increasing in number, busses and wireless networks are used as signal transmission in control systems. Networked control systems of this kind are characterized by occasional or arbitrary time delay or interruptions of minor loops. These influences are modelled as short-time uncertainties, in contrast to robust control systems in the literature, which are mainly studied as families with time-invariant uncertainties. Severe uncertainties are taken into consideration even if they cause short-time instability. An uncertainty can be valuated admissible if the accompanying signal amplitude or energy increase remains bounded. A third-order example with unstable behavior in a short-time interval is carried out in detail. I dedicate this article to my fellow professor O. Univ.-Prof. Dr. Gerfried Zeichen. Very affectionately yours, A. W.     

Secure vehicular communication systems: design and architecture

Significant developments have taken place over the past few years in the area of vehicular communication systems. Now, it is well understood in the community that security and protection of private user information are a prerequisite for the deployment of the technology. This is so precisely because the benefits of VC systems, with the mission to enhance transportation safety and efficiency, are at stake. Without the integration of strong and practical security and privacy enhancing mechanisms, VC systems can be disrupted or disabled, even by relatively unsophisticated attackers. We address this problem within the SeVeCom project, having developed a security architecture that provides a comprehensive and practical solution. We present our results in a set of two articles in this issue. In this first one, we analyze threats and types of adversaries, identify security and privacy requirements, and present a spectrum of mechanisms to secure VC systems. We provide a solution that can be quickly adopted and deployed. In the second article we present our progress toward the implementation of our architecture and results on the performance of the secure VC system, along with a discussion of upcoming research challenges and our related current results.     

Dispersion compensation optical fiber modules for 40 Gbps WDM communication systems

Dispersion compensation was originally proposed to equalize pulse distortion.With the development of wavelength division multiplexing (WDM) techniques for large capacity optical communication systems,dispersion compensation technologies have been applied into the field.Fiber-based dispersion compensation is an attractive technology for upgrading WDM communication systems because of its dispersion characteristics and good compatibility with transmission optical fibers.Dispersion compensation fibers and the modules are promising technologies,so they have been receiving more and more attention in recent years.In this work,high performance dispersion compensation fiber modules (DCFMs) were developed and applied for the 40 Giga bit-rate systems.First,the design optimization of the dispersion optical fibers was carried out.In theory,the better the refractive index profile is,the larger the negative dispersion we could obtain and the higher the figure of merit (FOM) for the dispersion optical fiber is.Then we manufactured the fiber by using the plasma chemical vapor deposition (PCVD) process of independent intellectual property rights,and a high performance dispersion optical fiber was fabricated.Dispersion compensation fiber modules are made with the dispersion compensating fibers (DCFs) and pigtail fibers at both ends of the DCFs to connect with the transmission fibers.The DCFMs present the following superior characteristics:low insertion loss (IL),low polarization mode dispersion,good matched dispersion for transmission fibers,low nonlinearity,and good stability for environmental variation.The DCFMs have the functions of dispersion compensation and slope compensation in the wavelength range of 1525 to 1625nm.The experiments showed that the dispersion compensation modules (DCMs) met the requirements of the GR-1221-CORE,GR-2854-CORE,and GR-63-CORE standards.The residual dispersions of the G.652 transmission lines compensated for by the DCM in the C-band are less than 3.0ps/nm,and the dispersion slopes are also compensated for by 100%.With the DCFMs,the 8×80km unidirectional transmission experiments in the 48-channel 40Gbps WDM communication system was successfully made,and the results showed that the channel cost was smaller than 1.20dB,without any bit error.     

A model for fault-tolerant networked control system using TTP/C communication

Safety-critical aerospace functions are generally required to have failure rates less than 10/sup -9/ per hour (FAA, 1988) and an architecture that supports several such functions is required to have failure rates less than 10/sup -10/ per hour. Although the requirement for an individual automobile may be more relaxed, similar requirements apply for automobiles in general (Rushby, 2001), because of their large number as compared to aircraft. Consumer-grade electronics have failure rates that are orders of magnitude worse than this. Hence, redundancy to improve failure rates and fault tolerance to prevent faults from propagating both are essential elements of a safety critical networked control system (NCS). TTP/C is a member of the time-triggered protocol (TTP) family that satisfies Society of Automotive Engineers Class C requirements for hard real-time fault-tolerant communication. A model is presented for a fault-tolerant NCS using TTP/C communication. Appropriate features of TTP/C are incorporated in the model. A simulation is presented for the electric power steering node with switching controller, which makes the node tolerant to the parameter faults column.     

A ubiquitous mobile communication architecture for next-generation heterogeneous wireless systems

Rapid progress in research and development of wireless networking and communication technologies have created different types of wireless systems (e.g., Bluetooth, IEEE 802.11, UMTS, and satellite networks). These systems are envisioned to coordinate with each other to provide ubiquitous high-data-rate services to mobile users. In this article, the architecture for ubiquitous mobile communications (AMC) is introduced that integrates these heterogeneous wireless systems. AMC eliminates the need for direct service level agreements among service providers by using a third party, a network interoperating agent. Instead of deploying a totally new infrastructure, AMC extends the existing infrastructure to integrate heterogeneous wireless systems. It uses IP as the interconnection protocol. By using IP as the gluing protocol, transparency to the heterogeneities of the individual systems is achieved in AMC. Third-party-based authentication and billing algorithms are designed for AMC. New mobility management protocols are also developed to support seamless roaming between different wireless systems.     

时延网络控制系统控制方法研究综述

本文介绍了网络控制系统的基本概念,分析了网络控制系统的优缺点,并主要针对网路控制系统中的时延问题,论述了6种时延网络控制系统控制方法:增广状态离散时间模型法、缓冲队列法、摄动法、随机最优控制方法、鲁棒控制方法、模糊逻辑调节法.本文对6种控制方法各自的特点和适用范围进行了较为详细地讨论,并对各自的优缺点进行了对比分析,对进一步研究适合于时延网络控制系统自身特点的控制方法进行了展望.本文研究的内容是当今控制领域研究的热点问题之一,无论对网络控制系统的研究与应用,还是对网络控制系统中时延问题的解决都具有一定的意义和参考价值.     

Distributed servers architecture for networked video services

In an on-demand video system, the video repository generally has limited streaming capacities and may be far from the users. In order to achieve higher user capacity and lower network transmission cost, distributed servers architecture can be used, in which multiple local servers are placed close to user pools and, according to their local demands, dynamically cache the contents streamed from the repository. We study a number of caching schemes as applied in the local servers depending on whether the repository is able to multicast movie contents to the local servers or not, and whether the local servers can exchange their cached contents among themselves or not. Our caching schemes keep a circular buffer of data for the movie requested, and hence movies are partially cached. By adjusting the size of the buffer, such caching is able to achieve better tradeoff between network channels and local storage as compared to the traditional caching in which a movie is treated as an entity. For each caching scheme, we study the tradeoff between the local storage and the network channels, and address how the total cost of the system can be minimized by appropriately sizing the buffer. As compared to a number of traditional operations (request batching and multicasting, true-VOD, etc.), we show that distributed servers architecture is able to achieve much lower system cost to offer on-demand video services     

State feedback controller design of networked control systems

This paper is concerned with the controller design of networked control systems (NCS). A new model of the NCSs is provided under consideration of both the network-induced delay and the data packet dropout in the transmission. In terms of the given model, a controller design method is proposed based on a delay-dependent approach. The feedback gain of a memoryless controller and the maximum allowable value of the network-induced delay can be derived by solving a set of linear matrix inequalities. Two examples are given to show the effectiveness of our method.