Volume 67, Issue 1 - Special Issue: Methods for a reliable wireless communication in the industry / Lutz Rauchhaupt

The factories of the future will be highly digitalized in order to enable flexible and interconnected manufacturing processes. Especially wireless technologies will be beneficial for industrial automation. However, the high density of metallic objects is challenging for wireless systems due to multipath fading. In order to understand the signal propagation in industrial environments, this paper provides results from a number of channel measurement campaigns funded by the German research initiative “Reliable wireless communication in the industry”. We give an overview of different measurement scenarios covering visible light communication and radio communication below 6 GHz. We analyze large and small scale parameters as well as delay statistics of the wireless channels. Finally, we discuss the importance of the results for the definition of industrial channel models.

Zusammenfassung Im Kontext von Industrie 4.0 werden verstärkt drahtlose Kommunikationssysteme in industrielle Anwendungen integriert. Die Anforderungen der Fertigungsautomation, welche besonders streng hinsichtlich Zuverlässigkeit und Latenz sind, werden bisher nur teilweise durch spezifische kabellose Systeme wie WirelessHART oder WSAN erfüllt. Damit Funksysteme auch in kritischen Anwendungen der Fertigungsautomation eingesetzt werden können, verfolgt das ParSec-Projekt den vielversprechenden Parallel Sequence Spread Spectrum (PSSS)-Ansatz. Dieser Artikel stellt das ParSec-System basierend auf PSSS vor. Das Funktionsprinzip des PSSS-Ansatzes wird erläutert und die Vorteile hinsichtlich eines flexiblen Kommunikationsprotokolls werden beschrieben. Die Integration des ParSec-Funksystems in ein bestehendes Industrial Ethernet-System wird diskutiert.

Concurrent Transmissions (CT) based flooding appears as a highly reliable and low latency mechanism to achieve source-to-sink communication of packets within a Wireless Sensor Network (WSN). CT are usually misunderstood, since they are mainly analyzed in the baseband domain. A comprehensive analysis, including the effects of the carrier, demonstrates that they cannot work in simple phase-modulated communication systems due to the beating effect. In contrast, non-coherent frequency receivers offer a very robust behavior. CT applicability in IEEE 802.15.4 is mainly because of two factors: transmissions are usually demodulated as non-coherent MSK (as opposed to coherent OQPSK) and the Direct Sequence Spread Spectrum (DSSS), that helps minimizing the error rate.

Nowadays, spectrum in industrial radio systems is already overoccupied. Therefore, future Industry 4.0 applications require coexistence management of different wireless communication systems. For identification of active systems, we propose Compressed Edge Spectrum Sensing (CESS). Here, we focus on practical aspects and show that the sampling rate can still be highly reduced.

Zusammenfassung Das Konzept Industrie 4.0 sieht steigende Flexibilität und Mobilität im Produktionsprozess vor. Daher werden bei der Funkkommunikation zunehmend höhere Anforderungen an das Zeit- und Fehlerverhalten gestellt. Zum Einsatz kommen mehrere gleichzeitig aktive Funkkommunikationssysteme. Diese Systeme müssen im Gesamtsystem koexistieren. Zur Sicherstellung der Koexistenz dient das Koexistenzmanagement. Ein aussichtsreicher Ansatz besteht darin, dieses Koexistenzmanagement mit regelungstechnischen Methoden zu untersuchen. In diesem Beitrag wird die Modellierung des Interferenzverhaltens beschrieben. Dafür wird das Zeitverhalten einer Nachrichtenübertragung mit der Petri-Netz Notation in max-plus Algebra nachgebildet. Zur Validierung des Modells wird ein industrienaher Hardware-in-the-Loop Aufbau genutzt.

Today many hybrid (wired & wireless) industrial communication networks with a huge variety of heterogeneous technologies and protocols are present in the manufacturing and automation domain. The increasing requirements regarding e. g., latency, reliability, or determinism create the need for a holistic network management concept in order to assure a network-wide Quality-of-Service (QoS) resource provisioning and the assurance of the admissioned resources. Consequently, a monitoring of the whole network is required to feed the network management system with the needed information about the underlying network processes. Various technical approaches using different methods of extracting the information from network traffic are available for the purpose of QoS parameter observance and measurement at the moment. Therefore, this paper provides a state of the art research about network management and QoS provisioning respectively QoS assurance concepts. In addition, the passive network monitoring approach using the flow export technique based on the Internet Protocol Flow Information Export (IPFIX) is investigated for a utilisation in the nowadays industry domain based on a conceptual case study with a wireless protocol. As a conclusion, an evaluation is performed in order to clarify the limits and the overall usability of IPFIX for the monitoring of industrial networks in order to support future network management systems.

Reliability of wireless communication is the key to the next stages of the imminent industrial evolution known as Industry 4.0. Removing the bonds of cabling and wires will provide the ability of free movement and the possibility of deployment in previously unreachable locations. To build confidence in the reliability of wireless transmission systems, a method for measuring said reliability is required. This article describes such a method which forms the basis of two interlinked testbeds being developed within the scope of the Celtic Plus project ReICOvAir.