Lisa Underberg

ParSec: A PSSS approach to industrial radio with very low and very flexible cycle timing

Industry 4.0 is a subject of current relevance which targets detailed information acquisition from industrial production processes. Wireless communication to ease this acquisition process is highly interesting but suffers today from problems of low reliability, high latency and small flexibility. ParSec addresses these subjects by investigating an innovative, CDMA based approach with very low latency of <; 50 μs, flexible resource block scheduling and BER of ≤ 10-9. While the latency figure is completely based on the assumption that a minimum of 3 symbol durations are needed the BER comes from the requirement specification. Two forms of FEC are used to achieve this requested figure. The radio will be used in the frequency range from 5,725 to 5,875 GHz and work without listen before talk. A rapid prototype has been built to conduct channel measurements and prove the promised properties of the PSSS255 approach. The project is conducted in the framework of other “Industrial Radio” oriented projects supported by the German federal ministry of education and research (BMBF).

Parallel Sequence Spread Spectrum: Analytical and simulative approach for determination of bit error probability

Communication in industrial applications like factory automation (FA) demands very low latency combined with high reliability. Since state of the art wireless technologies are not entirely fulfilling FA requirements, novel approaches are being developed. In this context Parallel Sequence Spread Spectrum (PSSS) is a promising technology, which enables shortest latencies, whereas its bit error performance has not yet been analyzed. Similar to Direct Sequence Spread Spectrum (DSSS), where data symbols are spread each with an appropriate sequence, PSSS spreading is performed based on a cyclically shifted m-sequence. Each cyclic shift of the base m-sequence is code, which enables a CDMA scheme. This paper deduces a theoretical and simulative approach determining the bit error performance for an ideal CDMA and for a time offset between several nodes in an AWGN channel. Based on this analysis, performance constraints and reliability limits such as requested synchronization accuracy are revealed.

Coverage Range Analysis of Wireless Technologies for Industrial Automation

Reliable wireless communication is crucial to current and future industrial applications, but is however not yet applicable in many scenarios. Thus novel approaches are being investigated at the moment, from which three physical (PHY) layer technologies are depicted for detailed evaluation in this paper. Preceding the performance analysis, industrial application requirements and constraints as spatial extent, number of nodes, cycle time, PER and user data length are summarized. Error rates and coverage ranges are calculated and presented for Ultra Wide Band (UWB), Frequency Hopping Spread Spectrum (FHSS) and Parallel Sequence Spread Spectrum (PSSS) assuming an AWGN channel.

Industrial WSN Based on IR-UWB and a Low-Latency MAC Protocol

Abstract Wireless sensor networks for industrial communication require high reliability and low latency. As current wireless sensor networks do not entirely meet these requirements, novel system approaches need to be developed. Since ultra wideband communication systems seem to be a promising approach, this paper evaluates the performance of the IEEE 802.15.4 impulse-radio ultra-wideband physical layer and the IEEE 802.15.4 Low Latency Deterministic Network (LLDN) MAC for industrial applications. Novel approaches and system adaptions are proposed to meet the application requirements. In this regard, a synchronization approach based on circular average magnitude difference functions (CAMDF) and on a clean template (CT) is presented for the correlation receiver. An adapted MAC protocol titled aggregated low latency (ALL) MAC is proposed to significantly reduce the resulting latency. Based on the system proposals, a hardware prototype has been developed, which proves the feasibility of the system and visualizes the real-time performance of the MAC protocol.

Aggregated time-critical MAC protocol for factory automation

Communication in industrial applications like wireless factory automation demands high reliability and low latency. Due to the fact that state of the art wireless sensor networks do not entirely fulfill the high requirements, new approaches have to be developed. An ultra-wideband system in combination with a MAC protocol for time-critical applications seems to be a promising approach. This paper introduces an optimized MAC protocol to guarantee the stringent real-time requirements of factory automation. Based on a realistic network scenario and IEEE 802.15.4 impulse-radio ultra-wideband physical layer simulations, both reliability and latency are examined. Moreover, the impact of retransmissions is analyzed. The proposed MAC protocol minimizes the resulting latency meeting entirely the requirements of factory automation.

Measurements for the development of an enhanced model for wireless channels in industrial environments

Novel wireless systems are often first evaluated by simulation, before prototypes are tested and the concepts are standardized. In order to ensure relevant simulation results, the wireless channel has to be modelled properly and application oriented. Currently, only few considerable industrial channel models are available. The IEEE 802.15.4a model is the most commonly used. CM 7 applies for LOS modelling and CM 8 for NLOS environments. Both are only applicable for distances up to 8 m. In order to enhance the existing channel models, an extended wide band measurement campaign including seven scenarios at three different industrial locations was performed. From different LOS and NLOS measurement series in a warehouse, a manufacturing shop and a mechanical workshop, values for the path loss exponent, RMS delay spread, coherence bandwidth and fading statistics were obtained, valid for distances up to 40 m. Setup, scenarios and the results of these measurements are presented in this paper. The abundance of metallic reflectors and scatterers leads to a dense multipath environment, which causes Rayleigh distributed small scale fading for both LOS and NLOS scenarios. The path loss exponent is smaller than 2 for LOS scenarios and the PDPs show very small power decay constants due to the rich scattering environment. Moreover, the RMS delay spread was found to increase proportionally to the distance. Corresponding to this, the coherence bandwidth decreases inversely proportional to the distance. The measurement results are compared to the related work and especially with the IEEE 802.15.4a channel model.

ParSec: Wireless industrial communication first PSSS measurements in industrial environment

Wireless technologies gain importance in various fields of industrial communication as they facilitate control and data acquisition tasks. In this context, Parallel Sequence Spread Spectrum (PSSS) is a promising new approach. The parametrization of a PSSS system is very flexible and thus can be precisely adapted to the applications requirements. Independent of the PSSS parametrization, the transmission resources can be assigned efficiently since their management is very flexible. With full duplex and a resource stream in both up- and downlink, even a network with high node density and varying QoS requirements can be served in a single PSSS system. Especially cycle times smaller than 1 ms are possible. A PSSS system for ultra low latency and highly reliable industrial applications is parametrized in the German research project ParSec. In ParSec, the PSSS system is evaluated analytically as well as in practice. In order to allow early measurements, in ParSec a rapid prototype system was developed, with which first PSSS measurements were performed. This paper gives an overview of the fundamental PSSS concept, while it points out the overall systems potential in industrial communication. Moreover, the measurement results are discussed to evaluate the bit error distribution in a PSSS frame. Rolf Kraemer IHP Microelectronics Frankfurt (Oder), Germany.

Coverage Range Analysis and Performance Evaluation of Wireless Technologies in Industrial Channel Conditions

While current reliable and ultra low latency industrial communication is based on wired fieldbus systems, wireless communication is the key to enable future industrial applications. However, the reliability of state-of-the-art wireless technologies is not sufficient for many industrial application scenarios. Thus, novel wireless approaches are being investigated at the moment, from which three promising physical layer (PHY) technologies are depicted for detailed evaluation in this paper: Ultra Wide Band (UWB), Frequency Hopping Spread Spectrum (FHSS) and Parallel Sequence Spread Spectrum (PSSS). In order to assess each system’s performance, Key Performance Indicators (KPI) are derived from industrial application constraints. In this paper, industrial applications are therefore categorized by vital requirements such as spatial extent, number of nodes, cycle time, PER and user data length. The depicted technologies are evaluated regarding the KPIs error rate and coverage range in AWGN and industrial fading channel conditions.

Time-critical MAC protocol based on IEEE 802.15.4 IR-UWB optimized for industrial wireless sensor networks

Communication in industrial applications like wireless factory automation demands high reliability and low latency. Since state of the art wireless sensor networks do not entirely meet the high requirements, new approaches have to be developed. An ultra-wideband system in combination with a suitable MAC protocol seems to be a promising approach. The proposed ultra-wideband system already provides reduced interference and coexistence issues. Nevertheless, the MAC protocol has to be optimized to guarantee the stringent real time requirements of factory automation. This paper introduces an optimized MAC protocol to be used in combination with the IEEE 802.15.4 impulse-radio ultra-wideband physical layer. Based on a realistic network scenario and physical layer simulations, both reliability and latency are examined.