A real-time multicast routing scheme for multi-hop switched fieldbuses

The rapid scaling up of Networked Control Systems (NCS) is forcing traditional single-hop shared medium industrial fieldbuses (a.k.a. fieldbuses) to evolve toward multi-hop switched fieldbuses. Such evolution faces many challenges. The first is the re-design of switch architecture. To meet the real-time nature of NCS traffic, and to lay a smooth evolution path for switch manufacturers, it is widely agreed that a (if not the) promising switch architecture is an input queueing crossbar architecture running TDMA scheduling. The second challenge is real-time multicast. NCS applications usually involve complex distributed multiple-input-multiple-output interactions, which by their nature necessitate real-time multicast. In shared medium fieldbuses, real-time multicast is straightforward as data sent to the medium is heard by all nodes. On multi-hop switched fieldbuses, however, real-time multicast becomes non-trivial. In this paper, we prove real-time multicast on multi-hop switched fieldbuses is NP-Hard. What is more, real-time multicast on multi-hop switched fieldbuses is fundamentally different from Internet multicast, due to real-time requirement and the homogeneous input queueing crossbar switch architecture. Particularly, switch external links' capacities are no longer mutually independent. Such drastic change of assumptions warrants developing new routing algorithms, and a heuristic algorithm is hereby proposed.Department of Computin

Ethernet - a survey on its fields of application

During the last decades, Ethernet progressively became the most widely used local area networking (LAN) technology. Apart from LAN installations, Ethernet became also attractive for many other fields of application, ranging from industry to avionics, telecommunication, and multimedia. The expanded application of this technology is mainly due to its significant assets like reduced cost, backward-compatibility, flexibility, and expandability. However, this new trend raises some problems concerning the services of the protocol and the requirements for each application. Therefore, specific adaptations prove essential to integrate this communication technology in each field of application. Our primary objective is to show how Ethernet has been enhanced to comply with the specific requirements of several application fields, particularly in transport, embedded and multimedia contexts. The paper first describes the common Ethernet LAN technology and highlights its main features. It reviews the most important specific Ethernet versions with respect to each application field’s requirements. Finally, we compare these different fields of application and we particularly focus on the fundamental concepts and the quality of service capabilities of each proposal

Design of a New High Bandwidth Network for Agricultural Machines

Ethernet is by now the most adopted bus for fast digital communications in many environments, from household entertainment to PLC robotics in industrial assembly lines. Even in automotive industry, the interest in this technology is increasingly growing, pushed forward by research and by the need of high throughput that high dynamics distributed control demands. Although 100base-TX physical layer (PHY) does not seem to meet EMC requirements for vehicular and heavy-duty environments, OPEN Alliance BroadR Reach (soon becoming IEEE standard as IEEE 802.3bw) technology is the most promising and already adopted Ethernet-compatible PHY, reaching 100Mbps over an unshielded twisted pair. An agricultural machine is usually a system including tractor and one or more implements attached to it, to the back or to the front. Nowadays, a specific CAN-based distributed control network support treatments and applications, namely ISOBUS, defined by ISO 11783. This work deals with architectural and technological aspects of advanced Ethernet networks in order to provide a high-throughput deterministic network for in-vehicle distributed control for agricultural machinery. Two main paths of investigation will be presented: one concerning the prioritization of standard Ethernet taking advantage of standard ways of prioritization in well-established technologies; the other changing the channel access method of Ethernet using an industrial fieldbus, chosen after careful investigation. The prioritization of standard Ethernet is performed at two, non-mutual exclusive layers of the ISO OSI stack: one at L3, using the diffserv (former TOS) Ip field; one at L2, using the priorities defined in IEEE 802.1p, used in IEEE 802.1q (VLAN). These choices have several implications in the specific field of application of the agricultural machines. The change of the access method, instead, focused on the adoption of a specific fieldbus, in order to grant deterministic access to the medium and reliability of communications for safety-relevant applications. After a survey, that will be reported, the Powerlink fieldbus was chosen and some modifications will be discussed in order to suit the scope of the research

Performance Analysis in IP-Based Industrial Communication Networks

S rostoucím počtem řídicích systémů a jejich distribuovanosti získávájí komunikační sítě na důležitosti a objevují se nové výzkumné trendy. Hlavní problematikou v této oblasti, narozdíl od dřívějších řídicích systémů využívajících dedikovaných komunikačních obvodů, je časově proměnné zpoždění měřicích a řídicích signálů způsobené paketově orientovanými komunikačními prostředky, jako např. Ethernet. Aspekty komunikace v reálném čase byly v těchto sítích již úspěšně vyřešeny. Nicméně, analýzy trendů trhu předpovídají budoucí využití také IP sítí v průmyslové komunikaci pro časově kritickou procesní vyměnu dat. IP komunikace má ovšem pouze omezenou podporu v instrumentaci pro průmyslovou automatizace. Tato výzva byla nedávno technicky vyřešena v rámci projektu Virtual Automation Networks (virtuální automatizační sítě - VAN) zapojením mechanismů kvality služeb (QoS), které jsou schopny zajistit měkkou úroveň komunikace v reálném čase. Předložená dizertační práce se zaměřuje na aspekty výkonnosti reálného času z analytického hlediska a nabízí prostředek pro hodnocení využitelnosti IP komunikace pro budoucí průmyslové aplikace. Hlavním cílem této dizertační práce je vytvoření vhodného modelovacího rámce založeného na network calculus, který pomůže provést worst-case výkonnostní analýzu časového chování IP komunikačních sítí a jejich prvků určených pro budoucí použití v průmyslové automatizaci. V práci byla použita empirická analýza pro určení dominantních faktorů ovlivňujících časového chování síťových zařízení a identifikaci parametrů modelů těchto zařízení. Empirická analýza využívá nástroj TestQoS vyvinutý pro tyto účely. Byla navržena drobná rozšíření rámce network calculus, která byla nutná pro modelování časového chování používaných zařízení. Bylo vytvořeno několik typových modelů zařízení jako výsledek klasifikace různých architektur síťových zařízení a empiricky zjištěných dominantních faktorů. U modelovaných zařízení byla využita nová metoda identifikace parametrů. Práce je zakončena validací časových modelů dvou síťových zařízení (přepínače a směrovače) oproti empirickým pozorováním.With the growing scale of control systems and their distributed nature, communication networks have been gaining importance and new research challenges have been appearing. The major problem, contrary to previously used control systems with dedicated communication circuits, is time-varying delay of control and measurement signals introduced by packet-switched networks, such as Ethernet. The real-time issues in these networks have been tackled by proper adaptations. Nevertheless, market trend analyses foresee also future adoptions of IP-based communication networks in industrial automation for time-critical run-time data exchange. IP-based communication has only a limited support from the existing instrumentation in industrial automation. This challenge has recently been technically tackled within the Virtual Automation Networks (VAN) project by adopting the quality of service (QoS) architecture delivering soft-real-time communication behaviour. This dissertation focuses on the real-time performance aspects from the analytical point of view and provides means for applicability assessment of IP-based communication for future industrial applications. The main objective of this dissertation is establishment of a relevant modelling framework based on network calculus which will assist worst-case performance analysis of temporal behaviour of IP-based communication networks and networking devices intended for future use in industrial automation. Empirical analysis was used to identify dominant factors influencing the temporal performance of networking devices and for model parameter identification. The empirical analysis makes use of the TestQoS tool developed for this purpose. Minor extensions to the network calculus framework were proposed enabling to model the required temporal behaviour of networking devices. Several exemplary models were inferred as a result of classification of different networking device architectures and empirically identified dominant factors. A novel method for parameter identification was used with the modelled devices. Finally, two temporal models of networking devices (a switch and a router) were validated against empirical observations.

CarRing IV- Real-time Computer Network

Ob in der Automobil-, Avionik- oder Automatisierungstechnik, die Fortschritte in der Echtzeitkommunikation richten sich auf weitere Verbesserungen bereits existierender Lösungen. Im Kfz-Bereich führen die steigenden Zahlen computerbasierter Systeme, Anwendungen und Anschlüsse sowie die Verwendung mehrerer proprietärer Kommunikationsstandards zu einem immer komplexeren Kabelbaum. Ursächlich hierfür sind inkompatible Standards, wodurch nicht nur die Kosten, sondern auch das Gewicht und damit der Kraftstoffverbrauch negativ beeinflusst werden. Im ersten Teil der Dissertation wird das Echtzeitprotokoll von CarRing IV (CRIV) vorgestellt. Es bietet isochrone und harte Echtzeitgarantien, ohne dass eine netzwerkweite Synchronisation erforderlich ist. Mit bis zu 16 Knoten pro Ring kann ein CR-IV-Netz aus bis zu 256 Ringen bestehen, die durch Router miteinander verbunden sind. CR-IV verwendet ein reduziertes OSI-Modell (Schichten 1-3, 7), das für seine Anwendungsbereiche sowohl typisch als auch vorteilhaft ist. Außerdem unterstützt es sowohl ereignis- als auch zeitgesteuerte Kommunikationsparadigmen. Der Transparent-Modus ermöglicht es CR-IV, als Backbone für bestehende Netze zu verwenden, wodurch Inkompatibilitätsprobleme beseitigt werden und der Wechsel zu einer einheitlicheren Netzlösung erleichtert wird. Mit dieser Funktionalität können Nutzergeräte über ein CR-IV-Netz miteinander verbunden werden, ohne dass der Nutzer eingreifen oder etwas ändern muss. Durch Multicast unterstützt CRIV auch die Emulation von Feldbussen. Der zweite Teil der Dissertation stellt den anderen wichtigen Aspekt von CR-IV vor. Alle Schichten des OSI-Modells sind in einem FPGA mit Hardware Description Languages (HDLs) ohne Hard- oder Softprozessoren implementiert. Das Register-Transfer-Level (RTL)-Hardwaredesign von CR-IV wird mit einem neuen Ansatz erstellt, der am besten als tokenbasierter Datenfluss beschrieben werden kann. Der Ansatz ist sowohl vertikal als auch horizontal skalierbar. Er verwendet lose gekoppelte Processing Elements (PEs), die stateless arbeiten, sowie Arbiter/Speicherzuordnungspaare. Durch die granulare Kontrolle und die Aufteilung aller Aspekte einer Lösung eignet sich der Ansatz für die Implementierung anderer Software-Level-Lösungen in Hardware. Viele Testszenarios werden durchgeführt, um die in CR-IV erzielten Ergebnisse zu verdeutlichen und zu überprüfen. Diese Szenarien reichen von direkten Leistungsmessungen bis hin zu verhaltensspezifischen Tests. Zusätzlich wird eine Labor-Demo erstellt, die grundsätzlich auf ein Proof of Concept zielt. Die Demo stellt einen praktischen Test anstelle szenariospezifischer Tests dar. Alle Testszenarien und die Labor-Demo werden mit den Prototyp-Boards des Projekts durchgef¨uhrt, d.h. es sind keine Simulationstests. Die Ergebnisse stellen die realistischen Leistungen von CR-IV mit bis zu 13,61 Gbit/s dar.Whether be it automotive, avionics or automation, advances in their respective real-time communication technology focus on further improving preexisting solutions. For in-vehicle communication, the ever-increasing number of computer-based systems, applications and connections as well as the use of multiple proprietary communication standards results in an increasingly complex wiring harness. This is in-part due to those standards being incompatible with one another. In addition to cost, this also impacts weight, which in turn affects fuel consumption. The work presented in this thesis is in-part theoretical and in-part applied. The former is represented by a new protocol, while the latter corresponds to the protocol’s hardware implementation. In the first part of the thesis, the real-time communication protocol of CarRing IV (CR-IV) is presented. It provides isochronous and hard real-time guarantees without requiring network-wide clock synchronization. With up to 16 nodes per ring, a CR-IV network can consist of as many as 256 rings interconnected by routers. CR-IV uses a reduced OSI model (layers 1-3, 7), which is both typical of and preferable for its application areas. Moreover, it supports both event- and time-triggered communication paradigms. The transparent mode feature allows CR-IV to act as a backbone for existing networks, thereby addressing incompatibility concerns and easing the transition into a more unified network solution. Using this feature, user devices can communicate with one another via a CR-IV network without requiring user interference, or any user device or application changes. Combined with the protocol’s reliable multicast, the feature extends CR-IV’s capabilities to include field bus emulation. The second part of the thesis presents the other important aspect of CR-IV. All of its OSI model layers are implemented in a FPGA using Hardware Description Languages (HDLs) without relying-on or including any hard or soft processors. CR-IV’s Register-Transfer Level (RTL) hardware design is created using a new approach that can best be described as token-based data-flow. The approach is both vertically and horizontally scalable. It uses stateless and loosely coupled Processing Elements (PEs) as well as arbiter/memory allocation pairs. By having granular control and compartmentalizing every aspect of a solution, the approach lends itself to being used for implementing other software-level solutions in hardware. Many test scenarios are conducted to both highlight and examine the results achieved in CR-IV. Those scenarios range from direct performance measurements to behavior-specific tests. Moreover, a lab-demo is created that essentially amounts to a proof of concept. The demo represents a practical test as opposed to a scenariospecific one. Whether be it test scenarios or the lab-demo, all are carried-out using the project’s prototype boards, i.e. no simulation tests. The results obtained represent CR-IV’s real-world realistic outcomes with up to 13.61 Gbps

Time-Sensitive Networking for Industrial Automation: Challenges, Opportunities, and Directions

With the introduction of Cyber-Physical Systems (CPS) and Internet of Things (IoT) into industrial applications, industrial automation is undergoing tremendous change, especially with regard to improving efficiency and reducing the cost of products. Industrial automation applications are often required to transmit time- and safety-critical data to monitor and control industrial processes, especially for critical control systems. There are a number of solutions to meet these requirements (e.g., priority-based real-time schedules and closed-loop feedback control systems). However, due to their different processing capabilities (e.g., in the end devices and network switches), different vendors may come out with distinct solutions, and this makes the large-scale integration of devices from different vendors difficult or impossible. IEEE 802.1 Time-Sensitive Networking (TSN) is a standardization group formed to enhance and optimize the IEEE 802.1 network standards, especially for Ethernet-based networks. These solutions can be evolved and adapted into a cross-industry scenario, such as a large-scale distributed industrial plant, which requires multiple industrial entities working collaboratively. This paper provides a comprehensive review on the current advances in TSN standards for industrial automation. We present the state-of-the-art IEEE TSN standards and discuss the opportunities and challenges when integrating each protocol into the industry domains. Finally, we discuss some promising research about applying the TSN technology to industrial automation applications

A Real-Time Communication Framework for Wireless Sensor Networks

Recent advances in miniaturization and low power design have led to a flurry of activity in wireless sensor networks. Sensor networks have different constraints than traditional wired networks. A wireless sensor network is a special network with large numbers of nodes equipped with embedded processors, sensors, and radios. These nodes collaborate to accomplish a common task such as environment monitoring or asset tracking. In many applications, sensor nodes will be deployed in an ad-hoc fashion without careful planning. They must organize themselves to form a multihop, wireless communication network. In sensor network environments, much research has been conducted in areas such as power consumption, self-organisation techniques, routing between the sensors, and the communication between the sensor and the sink. On the other hand, real-time communication with the Quality of Service (QoS) concept in wireless sensor networks is still an open research field. Most protocols either ignore real time or simply attempt to process as fast as possible and hope that this speed is sufficient to meet the deadline. However, the introduction of real-time communication has created additional challenges in this area. The sensor node spends most of its life routing packets from one node to another until the packet reaches the sink; therefore, the node functions as a small router most of the time. Since sensor networks deal with time-critical applications, it is often necessary for communication to meet real time constraints. However, research that deals with providing QoS guarantees for real-time traffic in sensor networks is still in its infancy.This thesis presents a real-time communication framework to provide quality of service in sensor networks environments. The proposed framework consists of four components: First, present an analytical model for implementing Priority Queuing (PQ) in a sensor node to calculate the queuing delay. The exact packet delay for corresponding classes is calculated. Further, the analytical results are validated through an extensive simulation study. Second, report on a novel analytical model based on a limited service polling discipline. The model is based on an M/D/1 queuing system (a special class of M/G/1 queuing systems), which takes into account two different classes of traffic in a sensor node. The proposed model implements two queues in a sensor node that are served in a round robin fashion. The exact queuing delay in a sensor node for corresponding classes is calculated. Then, the analytical results are validated through an extensive simulation study. Third, exhibit a novel packet delivery mechanism, namely the Multiple Level Stateless Protocol (MLSP), as a real-time protocol for sensor networks to guarantee the traffic in wireless sensor networks. MLSP improves the packet loss rate and the handling of holes in sensor network much better than its counterpart, MMSPEED. It also introduces the k-limited polling model for the first time. In addition, the whole sending packets dropped significantly compared to MMSPEED, which it leads to decrease the consumption power. Fourth, explain a new framework for moving data from the sink to the user, at a low cost and low power, using the Universal Mobile Telecommunication System (UMTS), which is standard for the Third Generation Mobile System (3G). The integration of sensor networks with the 3G mobile network infrastructure will reduce the cost of building new infrastructures and enable the large-scale deployment of sensor network

Real-time routing with priority scheduling and power adjustment in wireless sensor networks

Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2008.Thesis (Master's) -- Bilkent University, 2008.Includes bibliographical references leaves 64-67.Many wireless sensor network applications require real-time communication, and real-time applications require packets to reach destination on time. However, applications may send packets with different priorities and hence delay bounds for packets may vary significantly. Therefore packet differentiation in the network is essential for meeting the deadline requirements. We propose a routing protocol that supports real-time communication by utilizing transmit power adjustment in order to meet the deadline of urgent packets and use energy efficiently. Our protocol also provides packet scheduling and gives precedence to urgent packets. We have conducted experiments on our sensor network testbed to observe the effects of transmit power on end-to-end delay. As expected, increasing transmit power increases the range and link quality, and reduces the number of hops to reach destination. Therefore adjusting transmit power has a great effect on delivery time and can reduce the end-to-end delay. Our protocol, Real-time Routing with Priority Scheduling and Power Adjustment, uses different levels of transmit power for packets with different priorities. It sends urgent packets with maximum power to minimize end-to-end delay and lower priority packets with reduced power to save energy and balance the load on nodes. Simulation results show that our routing protocol increases the deadline meet ratio of packets and reduces the transmit energy spent per packet when compared to routing protocols that use fixed transmit power. Additionally, results indicate that our approach lessens the interference on sensor nodes that are caused by other transmissions and helps balancing the load on the nodes.Çelikkaya, Emine BüşraM.S