Mattia Rizzi

Improving simulation of wireless networked control systems based on WirelessHART

Recently, WirelessHART (2007) and ISA100.11a (2009) have been proposed as communication standard for a wireless fieldbus. However, Wireless Networked Control Systems performances are hard to verify in the real world, since test beds are expensive and difficult to implement. This paper proposes the use of a co-simulation framework based on the interaction of TrueTime, together with a cross layer wireless network simulator based on OMNET++. In particular, OMNET++ models show accurate aspects of network and devices, for improving overall coexistence management. A sample system controlled by a WirelessHART network has been considered; the analysis of the control performance and coexistence immunity of WirelessHART with respect to the traditional IEEE802.15.4, has been done.

Performance analysis of power line communication in industrial power distribution network

Power line communication (PLC) seems to be one of the best trade-off between cost and benefit for implementing Smart Grids in industrial context. Unfortunately, industrial environment may compromise the reliability of PLC technologies due to noisy communication channel and interfering/competing PLC systems. In this work, a multi-protocol instrument for PLC performance estimation is presented. The proposed solution is able to characterize and to decode several PLC systems with different physical modulations using a software-defined architecture. A working prototype of the proposed instrument has been characterized and used in a real industrial plant in order to study potential issues affecting PLC. Application of power line communication (PLC) in industrial environmentDesign of instrument architecture for performance evaluation of PLC standardsImplementation of instrument using software defined radio technologyExperimental characterization of the instrumentAnalyses of the performance of PLC in a real industrial environment

Timestamping and Ranging Performance for IEEE 802.15.4 CSS Systems

This paper deals with the characterization of IEEE 802.15.4 using the chirp spread spectrum (CSS) physical layer. A new test bench, which has full bandwidth capability and extreme flexibility because of the field programmable gate array-based probes, is used for managing reproducible measurement results. Several scenarios and algorithms have been considered for the estimation of the IEEE 802.15.4 CSS performance in real indoor environments. The absolute timestamping errors have been evaluated using the distributed synchronization feature (synchronous Ethernet) of the test bench probes. The ranging performance has been evaluated using both two-way ranging (TWR) and symmetrical double-sided TWR approaches. The characterization results in indoor situations show that the tested implementation of IEEE 802.15.4 CSS achieves mean timestamping errors of 200 ps, and a ranging root mean square error down to 0.5 m. Moreover, the CSS modulation highlights a good robustness against interference.

Characterization of multi-standard Power Line Communication on low-voltage grid

In the last years, the introduction of distributed energy resources increases the complexity of distribution grid management system, which requires performing communication infrastructures. Moreover, an optimal power management requires a direct data exchange with home and industrial automation and energy systems. A well known technology, the Power Line Communication (PLC), seems to be able to satisfy large parts of these demands. Nevertheless, several PLC solutions have been proposed over the years, each of them satisfying the requirements of specific applications. A measurement method able to characterize the communication performance of different PLC protocols is required due to the increasing complexity of the PLC modern infrastructures. In this work, an approach based on Software Defined Radio has been proposed. This solution is able to characterize several PLC systems, based on different physical modulations, using the same experimental set-up. The characterization of a PLC system, based on DBSK modulation, in a real environment, clearly demonstrated the feasibility of the proposed approach.

Using LoRa for industrial wireless networks

The new concept of Industry 4.0 has been developed: it includes both Internet of Things (IoT) structure and the local networks that are still needed to carry out real-time tasks. However, forecasts of mass application of consumer IoT system have stimulated the development of new wireless technologies that may also be interesting for industry. In this paper, the LoRa technology is investigated for the implementation of industrial wireless networks suitable for sensors and actuators of the Industry 4.0 era. After a brief overview of LoRa and LoRaWAN, the paper deals with the discussion about using LoRa for industrial applications compared to traditional industrial wireless systems. With only very light modifications to the upper layer of LoRaWAN communication stack, a time slot channel hopping schema is possible. The experimental results show the feasibility of the proposed approach, which is compatible with requirements of soft real-time applications in process industry. In particular, proper time, frequency, and spreading factor planning may allow 6000 nodes accessed up to one minute cycle time.

New test bench for evaluation of IEEE 802.15.4 CSS timestamping capabilities

The paper deals with a new test bench for the assessment of time-related performance of wireless systems implementing the IEEE 802.15.4 with the Chirp Spread Spectrum (CSS) physical layer. The test bench has been designed in order to clearly evaluate the timestamping capabilities of an FPGA-based implementation of the IEEE 802.15.4 CSS. The key features are the full bandwidth capability and the extreme flexibility thanks to the FPGA hardware which is completely programmable. The Synchronous Ethernet embedded in the test nodes guarantees the easy synchronization of device clocks through a wired backbone, which allows for estimation of the peak performance of the system under test. A case study is presented regarding a basic implementation of the IEEE 802.15.4 CSS; under the experimental conditions, the mean timestamping error of the evaluated system is less than 200 ps.

Evaluation of the IoT LoRaWAN Solution for Distributed Measurement Applications

Internet of Things (IoT) is based on data collection, where billions of sensors sample the real world; in other words, the IoT includes a giant distributed measurement system (DMS). A question still requiring an answer is: Are the IoT technologies usable to enhance traditional measurement systems, since they have been developed for a very similar objective? In this paper, the use of a long-range (LoRa) technology, originally developed for IoT, is investigated with the aim of implementing DMSs. After the conclusion that LoRa and LoRa wide area network architectures show a good match with measurement systems, this paper focuses on the characterization of time-related performance indicators that are important for distributed systems. The experimental results show the capability of low-cost transceiver to schedule the transmission of frames with a standard uncertainty less than

Timestamp Validation Strategy for Wireless Sensor Networks Based on IEEE 802.15.4 CSS

3~\mu \text{s}

Time of arrival estimation in power line communication systems for home smart grids

; and an acceptable long-term clock stability (Allan Deviation) of commercial available devices (nodes and packet forwarders) for application such as smart metering, smart building, and process industry.

White rabbit clock characteristics

Network time distribution relies on timestamping, which is employed by local nodes to assign a time value to incoming timing packets. Clearly, any error affecting the timestamp has a direct impact on the final synchronization accuracy of the system. In wireless sensor networks (WSNs), impairments affecting the wireless physical layer are the primary cause of such timestamping errors, and it would be advantageous to flag suspect timestamp values before feeding them into a synchronization algorithm. This paper discusses a new strategy for validating timestamps in a WSN based on IEEE 802.15.4 chirp spread spectrum. The considered system employs physical-level timestamping, which generates one timestamp for each symbol belonging to a packet. Such set of timestamps is processed using a Kalman filter (KF) that compares them with predicted values, employing statistical thresholds referred to the KF innovation process. Experimental results obtained over a long observation period shows that even in a noisy environment with several interfering communication sources, the algorithm is able to detect untrusted timestamps.