OpenMote+: a Range-Agile Multi-Radio Mote

International audienceThis article introduces OpenMote+, a prototyping platform designed for the Industrial Internet of Things (IIoT). The OpenMote+ offers a dual-radio interface for short- and long-range communications, supporting the most prominent physical and MAC (Medium Access Control) layer standards, such as IEEE 802.15.4e, IEEE 802.15.4g and 6TiSCH, and a contact-based interface based on NFC (Near Field Communications) to address the operational aspects of a network deployment, such as security key distribution and in-situ reprogramming. The OpenMote+ platform is complemented by support of the most popular open-source IIoT implementations today, such as OpenWSN, Contiki and RiOT

g6TiSCH: Generalized 6TiSCH for Agile Multi-PHY Wireless Networking

International audienceWireless networks traditionally use a single physical layer for communication: some use high bit-rate short-range radios, others low bit-rate long-range radios. This article introduces g6TiSCH, a generalization of the standards-based IETF 6TiSCH protocol stack. g6TiSCH allows nodes equipped with multiple radios to dynamically switch between them on a link-by-link basis, as a function of link-quality. This approach results in a dynamic trade-off between latency and power consumption. We evaluate the performance of the approach experimentally on an indoor office testbed of 36 OpenMote B boards. Each OpenMote B can communicate using FSK 868 MHz, O-QPSK 2.4 GHz or OFDM 868 MHz, a combination of long-range and short-range physical layers. We measure network formation time, end-to-end reliability, end-to-end latency, and battery lifetime. We compare the performance of g6TiSCH against that of a traditional 6TiSCH stack running on each of the three physical layers. Results show that g6TiSCH yields lower latency and network formation time than any of the individual PHYs, while maintaining a similar battery lifetime

No Free Lunch - Characterizing the Performance of 6TiSCH When Using Different Physical Layers

International audienceLow-power wireless applications require different trade off points between latency, reliability ,data rate and power consumption. Given such a set of constraints, which physical layer should I beusing? We study this question in the context of 6TiSCH,a state-of-the-art recently standardized protocol stack developed for harsh industrial applications. Specifically,we augment OpenWSN, the reference 6TiSCHopen-source implementation,to support one of three physical layers from the IEEE802.15.4g standard FSK 868 MHz which offers long range, OFDM 868 MHz which offers high data rate,and O-QPSK 2.4GHz which offers more balanced performance. We run the resulting firmware on the42-mote Open Testbed deployed in an office environment, once for each physical layer. Performance results show that, indeed, no physical layer outperforms the other for all metrics. This article argues for combining the physical layers, rather than choosing one,in a generalized 6TiSCH architecture in which technology-agile radio chips (of which there are now many) are driven by a protocol stack which c hooses the most appropriate physical layer on a frame-by-frame basis

A Historical Twist on Long-Range Wireless: Building a 103 km Multi-Hop Network Replicating Claude Chappe's Telegraph

International audienceIn 1794, French Engineer Claude Chappe coordinated the deployment of a network of dozens of optical semaphores. These formed “strings” that were hundreds of kilometers long, allowing for nationwide telegraphy. The Chappe telegraph inspired future developments of long-range telecommunications using electrical telegraphs and, later, digital telecommunication. Long-range wireless networks are used today for the Internet of Things (IoT), including industrial, agricultural, and urban applications. The long-range radio technology used today offers approximately 10 km of range. Long-range IoT solutions use “star” topology: all devices need to be within range of a gateway device. This limits the area covered by one such network to roughly a disk of a 10 km radius. In this article, we demonstrate a 103 km low-power wireless multi-hop network by combining long-range IoT radio technology with Claude Chappe’s vision. We placed 11 battery-powered devices at the former locations of the Chappe telegraph towers, hanging under helium balloons. We ran a proprietary protocol stack on these devices so they formed a 10-hop multi-hop network: devices forwarded the frames from the “previous” device in the chain. This is, to our knowledge, the longest low power multi-hop wireless network built to date, demonstrating the potential of combining long-range radio technology with multi-hop technology

Initial Design of a Generalization of the 6TiSCH Standard to Support Multiple PHY Layers

This report introduces early results from an experiment to integrate multiple radios in the same 6TiSCH network. It is provides an initial step towards the publication of an article tentatively titled “Generalized 6TiSCH for an Agile Multi-PHY Wireless Networking”. The work discussed the architecture of the proposed solution, and presents its performance compared to single-PHY networks.Ce rapport contient des résultats préliminaires d’une étude pour utiliser plusieurs couches physiques dans un même réseau 6TiSCH. Il s’agit d’une première étape dans le but de publier nos travaux complets, sous le titre (en anglais) “Generalized 6TiSCH for an Agile Multi-PHY Wireless Networking”. Ce rapport détaille l’architecture évaluée, et présente les performance de l’approche, en comparaison avec un réseau qui n’utilise qu’une seule couche physique

Experimental Interference Robustness Evaluation of IEEE 802.15.4-2015 OQPSK-DSSS and SUN-OFDM Physical Layers for Industrial Communications

International audienceIn this paper, we experimentally evaluate and compare the robustness against interference of the OQPSK-DSSS (Offset Quadrature Phase Shift Keying-Direct Sequence Spread Spectrum) and the SUN-OFDM (Smart Utility Network-Orthogonal Frequency Division Multiplexing) physical layers, as defined in the IEEE 802.15.4-2015 standard. The objective of this study is to provide a comprehensive analysis of the impact that different levels of interference produce on these modulations, in terms of the resulting PDR (Packet Delivery Ratio) and depending on the length of the packet being transmitted. The results show that the SUN-OFDM physical layer provides significant benefits compared to the ubiquitous OQPSK-DSSS in terms of interference robustness, regardless of the interference type and the packet length. Overall, this demonstrates the suitability of choosing the SUN-OFDM physical layer when deploying low-power wireless networks in industrial scenarios, especially taking into consideration the possibility of trading-off robustness and spectrum efficiency depending on the application requirements

Adaptive multi-PHY IEEE802.15.4 TSCH in sub-GHz industrial wireless networks

To provide wireless coverage in challenging industrial environments, IEEE802.15.4 Time-Slotted Channel Hopping (TSCH) presents a robust medium access protocol. Using multiple Physical Layers (PHYs) could improve TSCH even more in these heterogeneous environments. However, TSCH only defines one fixedduration timeslot structure allowing one packet transmission. Using multiple PHYs with various data rates therefore does not yield any improvements because of this single-packet limitation combined with a fixed slot duration. We therefore defined two alternative timeslot structures allowing multiple packets transmissions to increase the throughput for higher data rate PHYs while meeting a fixed slot duration. In addition, we developed a flexible Link Quality Estimation (LQE) technique to dynamically switch between PHYs depending on the current environment. This paper covers a theoretical evaluation of the proposed slot structures in terms of throughput, energy consumption and memory constraints backed with an experimental validation, using a proof-of-concept implementation, which includes topology and PHY switching. Our results show that a 153% higher net throughput can be obtained with 84% of the original energy consumption and confirm our theoretical evaluation with a 99 % accuracy. Additionally, we showed that in a real-life testbed of 33 nodes, spanning three floors and covering 2550 m(2), a compact multi-PHY TSCH network can be formed. By distinguishing between reliable and high throughput PHYs, a maximum hop count of three was achieved with a maximum throughput of 219 kbps. Consequently, using multiple (dynamic) PHYs in a single TSCH network is possible while still being backwards compatible to the original fixed slot duration TSCH standard

Long-Short Range Communication Network Leveraging LoRa and Wake-up Receiver

International audienceWireless sensor and actuator networks play a central role in the Internet of Things, and a lot of effort is devoted to enable energy efficient and low latency communications. In the recent years, low power communications has evolved towards multi-kilometer ranges and low bit-rate approaches such as LoRa TM. However, the medium access layer protocols rely on the well-known duty-cycling schemes, which require a trade-off between power consumption and latency for message transfer from the gateway to the nodes. Domains such as industrial applications in which sensors and actuators are part of the control loop require predictable latency, as well as low power consumption. Emerging ultra-low-power wake-up receivers enable pure-asynchronous communications, allowing both low latency and low power consumption, but at the cost of a lower sensitivity and lower range than traditional wireless receivers and LoRa TM. In this work, we propose an energy efficient architecture that combines long-range communication with ultra low-power short-range wake-up receivers to achieve both energy efficient and low latency communication in heterogeneous long-short range networks. A hardware architecture as well as a protocol is proposed to exploit the benefits of these two communication schemes. Experimental measurements and analytical comparisons show that the proposed approach remove the need for a trade-off between power consumption and latency

A system-level methodology for the design and deployment of reliable low-power wireless sensor networks

Innovative Internet of Things (IoT) applications with strict performance and energy consumption requirements and where the agile collection of data is paramount are rousing. Wireless sensor networks (WSN) represent a promising solution as they can be easily deployed to sense, process, and forward data. The large number of Sensor Nodes (SNs) composing a WSN are expected to be autonomous, with a node's lifetime dictated by the battery's size. As the form factor of the SN is critical in various use cases such as industrial and building automation, minimizing energy consumption while ensuring availability becomes a priority. Moreover, energy harvesting techniques are increasingly considered as a viable solution for building an entirely green SN and prolonging its lifetime. In the process of building a SN and in the absence of a clear and well-rounded methodology, the designer can easily make unfounded decisions about the right hardware components, their configuration and data reliable data communication techniques such as automatic repeat request (ARQ) and forward error correction (FEC). In this thesis, a methodology to better optimize the design, configuration and deployment of reliable ultra-low power WSNs is proposed. Comprehensive and realistic energy and path-loss (PL) models of the sensor node are also established. Through estimations and measurements, it is shown that following the proposed methodology, the designer can thoroughly explore the design space and make most favorable decisions when choosing commercial off-the-shelf (COTS) components, configuring the node, and deploying a reliable and energy-efficient WSN