Search

A crystal-free architecture of a low-power wireless node allows for a small and cheap design. The Single-Chip micro Mote (SCuM) is the first crystal-free mote-on-chip to be compatible with standards such as Bluetooth Low Energy and IEEE802.15.4, and develops as a collaboration between Kris Pister’s team at UC Berkeley and Thomas Watteyne’s team at Inria. This keynote will go through our 2019–2020 research journey around the SCuM chip. We start by detailing why a “crystal-free” architecture is such as radical move away from traditional low-power wireless radio design. We discuss the challenges of calibration and compensation in these designs, and show how we get a SCuM chip to communicate with off-the-shelf motes and participate in a standards-based IoT network. We then present an unexpected use case that crystal-free motes enable: tracking Asian hornets as they fly from a beehive back to their nest. We illustrate this presentation with numerous videos and hands-on experience. We finish this talk by discussing why crystal-free micro-robots are the next frontier of IoT research, addressing all open IoT networking research questions at once, which a tremendous potential for pioneering applications such as micro-wearables and swarm robotics. This keynote is tailored to the advanced researcher or engineer in embedded system, IoT and low-power wireless. It draws on recent activities within Inria’s EVA team (team.inria.fr/eva/), UC Berkeley’s Pister lab (bamlab.berkeley.edu) and their collaborative project around crystal-free architectures (www.crystalfree.org).

International audience; Short development cycles, application-field diversity, and requirements on network size or reliability put an ever increasing strain on Internet of Things (IoT) application developers. Real-time embedded operating systems (RTOS) aim to provide a key set of features, abstractions and services that enable faster development. To fulfill the promise of wire-like communication reliability, wireless standards such as WirelessHART, ISA100.11a and 6TiSCH have been developed and are used in the industry. Keeping these networks synchronized requires precise timing information from the underlying hardware. However, the hardware abstractions of an RTOS do come with an overhead, and the question arises on how these abstractions impact the performance of a complex network stack. To study this, we integrated Open-WSN, a standards-compliant open-source implementation of the 6TiSCH network stack, with RIOT, a prominent open-source RTOS. We compare the minimalistic "bare metal" approach of OpenWSN with RIOT's full-fledged RTOS environment. We study the impact on network performance, power consumption and real-time application properties. On the one hand, we show that using RIOT to execute a 6TiSCH stack does not degrade power consumption or network performance. On the other hand, we demonstrate how RIOT brings improvements on the time it takes to execute application tasks.

International audience; Experimentation on testbeds with Internet of Things (IoT) devices is hard. The tedious firmware development, the lack of user interfaces, the stochastic nature of the radio channel, the testbed learning curve, are some of the factors that make the evaluation process error prone. The impact of such errors on published results can be quite unfortunate, leading to misconclusions and false common wisdom. The selection of experiment conditions or performance metrics to evaluate one's own proposal may not lead to perfectly fair comparisons with state-of-the-art, either. Our research community is well aware of these problems and is actively working on solutions. We present OpenBenchmark, a cloud-based, reproducible, repeatable and comparable IoT benchmarking service. OpenBenchmark facilitates and improves the IoT experimentation workflow: it runs the experiments on supported testbeds, instruments the supported firmware according to the industry-relevant test scenarios, and collects and processes the experiment data to produce Key Performance Indicators (KPIs). This paper introduces the OpenBenchmark platform, discusses its applicability, design and implementation.

International audience; Industrial-grade performance of wireless networks has become a reality of the open Internet of Things through a low-power wireless technology called 6TiSCH. A standardization group of the same name within the Internet Engineering Task Force (IETF) has been working on a zero-configuration, IPv6-enabled solution applicable to industrial monitoring and control, smart building, home, city and agriculture. The base standardization work is virtually done. Before different stakeholders invest significant resources in developing and deploying 6TiSCH-based solutions, they need to have a certain level of assurance about whether the technology indeed meets their requirements. An unbiased performance benchmark of a standards-compliant 6TiSCH solution is therefore required by the industry, the research community and the standardization group. 6TiSCH Open Data Action (SODA) is a research project that will provide a 6TiSCH benchmark and open datasets in different industry-relevant scenarios. SODA will automate the experimentation on these scenarios so benchmarking can remain up-to-date with changes to the standards, and facilitate comparison with future technological developments, resulting in continuous delivery benchmarking. This paper introduces the SODA project and seeks community involvement on the definition of scenarios and Key Performance Indicators, and on the usage of the tools that will be provided.

International audience; 6TiSCH is a technology being standardized at the IETF which brings determinism to low-power wireless communication. In a 6TiSCH network, all communication is orchestrated by a communication schedule. This paper explores the applicability of this new technology to control systems. In particular, we apply it to the inverted pendulum, a canonical control system in which a cart moves along a track to keep a pendulum –which naturally falls over – upright. This paper presents the first characterization and implementation of a closed-loop wirelessfeedback control network using completely standards-compliant IEEE802.15.4 TSCH technology. First, we implement a control loop in OpenWSN and experimentally evaluate the performance of the network by varying the radio duty cycle, number of hops, and introducing controlled external interference. We show that 100% reliability can be achieved while maintaining latencies well below the critical delay of the system. Second, we use the network on an inverted pendulum system and show that angular deviations from the upright position do not exceed 3 degrees, even in a multi-hop setup. Finally, we discuss the results in detail, and advocate for a co-design of the controller and the networking system.

International audience; Recent wireless medium access control techniques, such as the Timeslotted Synchronized Channel Hopping (TSCH) and Deterministic & Synchronous Multi-channel Extension (DSME) modes in the IEEE802.15.4-2015 standard, use frequency diversity to cope with external interference and multipath fading. The result is wire-like reliability in a network built from unreliable wireless links. Yet, the impact of using multiple frequencies on the medium access control layer is still not perfectly understood, and virtually all channel hopping solutions use "blind" channel hopping, i.e., hopping over all frequencies equivalently. The goal of this work is to improve our understanding of the behavior of the wireless medium when using multiple frequencies, which will enable the design of more efficient protocols in the future. We collect a large dense connectivity dataset over the USC Tutornet Internet of Things Testbed, with dozens of low-power wireless nodes deployed in an office building. This publicly-available dataset offers complete traces of link quality across frequency, time and space. We analyze the data and extract meaningful and practical insights on the wireless medium when using multiple frequencies.

International audience; This paper introduces SOL, which is both an efficient data representation for sensor measurements and network statistics, and a complete low-power wireless sensor management system that builds around it. A SOL system consists of multiple low-power wireless mesh networks in which motes connected to sensors and actuators send data to a single server. It offers multi-tier data replication and the associated data recovery. SOL is used in 3 pilot deployments for micro-climate monitoring, building automation and agriculture applications. In conjunction with Metronome Systems’ NeoMote and Manager devices, SOL is a turn-key ready-to-deploy end-to-end system.

Deploying and customizing networks of Internet of Things (IoT) devices remains extremely challenging. This complexity has two main sources. First, end-users must integrate diverse sensor and actuator peripherals with IoT devices to realize their application. Second, the resulting system must provide reliable mesh networking in harsh network environments at extremely low power. This paper addresses both problems by proposing μPnP-Mesh, which combines the ease of use of μPnP with the industrial performance of SmartMesh IP. μPnP provides a low-power and low-cost method for achieving plug-and-play integration of peripherals with embedded IoT devices; SmartMesh IP provides low-power reliable mesh networking. With a true plug-and-play user experience and a lifetime above 6.5 years on a pair of AA batteries, μPnP-Mesh is a ready-to-use game-changing solution for applications such as home, building and factory automation. ispartof: pages:311-315 ispartof: IEEE 2nd World Forum on Internet of Things pages:311-315 ispartof: World Forum on Internet of Things (WF-IoT) location:Milan, Italy date:14 Dec - 16 Dec 2015 status: published

International audience; Time Synchronized Channel Hopping (TSCH) is a technique known to efficiently combat external interference and multi-path fading. TSCH is at the heart of industrial low-power wireless standards such as WirelessHART and IEEE802.15.4e, and the focus of the current standardization activities at IETF 6TiSCH. In a TSCH network, communicating nodes send successive link-layer frames at different frequencies. The performance of such frequency-agile communication is not well understood. In this paper, we propose an empirical approach. We conduct an experiment to record the connectivity between 350 nodes in a typical office environment, simultaneously on each of the 16 frequencies at 2.4 GHz. Analysis reveals the impact of WiFi interference on the reliability of the IEEE802.15.4 wireless links: even when the WiFi network sits idle, IEEE802.11 beaconing causes a significant number of links to drop from 90% to 70-80% packet delivery ratio. It also reveals the impact of multi-path fading, showing how moving a pair of nodes can cause their link to go from perfect to non-existing. Results show that the quality of each link depends heavily on the communication frequency. The paper shows the effectiveness of channel hopping: by simply changing the communication frequency between successive transmissions, less nodes are required to cover a geographical area. The paper discusses the importance of the frequency to retransmit on. The 5-hour connectivity trace reveals a wealth of information. This paper is only a first step towards a much larger dataset collected over a representative number of real-world deployments.

Smart Mesh IP is the latest protocol stack from the Linear Technology's Dust Networks group, who specialize in standards-based intelligent wireless sensor networking solutions. This paper presents a technical overview of this protocol stack, the System-on-Chip built around it, and the "ecosystem" to integrate a low-power mesh network in a larger system and the Internet. A descendant of long-standing protocols such as Wireless HART, the new IEEE802.15.4e Time slotted Channel Hopping standard delivers high reliability and ultra-low power. Combined with 6LoWPAN, the Smart Mesh IP protocol stack combines the industrial performance of IEEE802.15.4e with the ease-of-use of IPv6. After presenting the historical context of this technology, this paper discusses the different design choices which had to be made when designing this protocol stack, before covering typical use cases and real-world example deployments.

This document presents a new work called 6TSCH that is starting at the IETF to enable a large IPv6 multi-link subnet with industrial-grade performances of jitter, latency and reliability. The subnet is composed of a high speed powered backbone and a number of IEEE802.15.4e TSCH wireless mesh networks attached and synchronized by specialized Backbone Routers. Route Computation may be achieved in a centralized or in a distributed fashion, and tracks are installed to forward well-known flows with deterministic properties along their multi-hop path.

Existing commercial wireless sensor network solutions use Time-Synchronized Channel Hopping (TSCH) to achieve an end-to-end reliability higher than 99.9% and industry-accepted network lifetime (5–10 years on batteries). In these types of networks, once nodes synchronize, they follow a schedule which determines the time and frequency of the channel that is used to transmit and receive. Standards such as WirelessHART apply this technique. This paper addresses the ability to scale such a scheduling approach for specific applications.

Wireless Sensor Networks (WSNs) allow for untethered sensing of the environment. It is anticipated that, within the next few years, sensors will be deployed in a variety of scenarios, ranging from environmental monitoring to health care, from public to private sector and other areas. This paper investigate the utilization of receiver-based Medium Access Control (MAC) protocol in enhancing the performance of routing protocols such as IETF ROLL's RPL. Receiver-Based MAC (RB-MAC) is a preamble-sampling MAC protocol which dynamically elects the next-hop among a number of potential relay neighbors, based on current channel conditions and status of the sensor nodes. The proposed scheme is resilient to lossy links by nature, and hence reduces the number of retransmissions. We show by analysis how it outperforms the state-of-the-art sender-based preamble sampling MAC protocols in terms of energy and delay.

This paper presents one possible approach to Signalized Left Turn Assist at intersections. A sensing platform is designed to detect the presence of cars by measuring the deflection of the magnetic field when driving by. This platform is tested experimentally under different conditions. A threshold detection algorithm is designed to determine whether a car is passing in front of the sensor. The algorithm is first run off-board using a set of previously collected magnetometer measurements, before being implemented and run on-board the platform. We show how this detection algorithm performs better as the sensor is placed close to the traffic flow and we discuss how such sensors can be networked together to form a smart intersection.

Having a wake-up receiver constantly listening is often seen as a replacement for running a duty- cycled medium access control protocol on a commercial low-power radio chip. Wake-up receivers do offer a better latency while consuming negligible power. Recent wake-up receivers show an impressively low power consumption of 52uW, but at the cost of a sensitivity of -72dBm, 20-30dB higher than the sensitivity of a commercial radio chip. This difference in sensitivity causes the wake-up receiver to have a much smaller communication range than the commercially available low power radio. In practice, this translates into requiring a denser deployment, or having to add an external power amplifier. This paper discusses the applicability of wake-up receivers in low-power wireless multihop networks. We show how, at available sensitivity levels, a wake-up receiver helps reducing the power consumption, but also requires a dramatically higher design or deployment cost.

Reducing the time the radio is on in wireless devices results in lower power consumption, so sending the same data in fewer bytes can greatly extend the lifetime of a network. In this paper, we explore the use of protocol-agnostic packet compression, a technique orthogonal to current explicit compaction techniques. Because it functions as a transparent layer inside a communication stack and makes no assumption about the specific protocols used, it is generic enough to be used on multiple technologies. Compression is performed by identifying patterns in recent packets and replacing those patterns with bit flags in the transmitted packet. We present the results of compressing actual packet traces collected from several commercial networks using this algorithm and discuss the resource trade-offs of the algorithm. Results indicate compression ratios between 40% and 80%, yielding predicted energy savings of 30-70% in a typical time- synchronized network.

Reducing the number of transmitted bytes in a wireless sensor network reduces the time the radio is on, resulting in a significant increase in battery lifetime. Toward this end we have developed a compression technique that is independent of the protocols used in the network, acts as a transparent layer, and consumes minimal computing resources. Patterns in recent packets are identified and replaced in the transmitted packet by bit flags. This algorithm was tested on packet traces collected from commercial wireless sensor networks for 40-80% compression, yielding comparable energy savings in a time-synchronized network.

Wireless communication between a pair of nodes can suffer from self interference arising from multipath propagation reflecting off obstacles in the environment. In the event of a deep fade, caused by destructive interference, no signal power is seen at the receiver, and so communication fails. Multipath fading can be overcome by shifting the location of one node, or by switching the communication carrier frequency. The effects of such actions can be characterized by the coherence length (L) and coherence bandwidth (B), respectively, given as the amount of shift necessary to transition from a deep fade to a region of average signal strength. Experimental results for a representative 2.4GHz wireless link indicate L = 5.5cm and B can vary from 5MHz at long ranges up to 15MHz for short links. For wireless sensor networks (WSNs), typically operating under the IEEE802.15.4 standard, multipath effects are therefore best handled by a channel hopping scheme in which successive communication attempts are widely spread across available carrier frequencies.

IETF ROLL has recently proposed gradient routing as a fundamental building block for data collection in Wireless Sensor Networks. This paper seconds this choice by presenting an implementation of gradient routing on current hardware, and by showing experimentally that gradient routing is robust against topological changes. To stress its self-healing quality, we design and implement a complete communication stack in which neighbor tables are built in a purely reactive fashion. We quantify the resulting topological changes, and show how gradient routing elegantly handles these dynamics. This paper presents, to the best of our knowledge, the first experimental study on gradient routing as advocated by IETF ROLL.

Component-Based Software Engineering (CBSE) does not yet fully address non-functional requirements of embedded systems. To reach this goal, we show how to extend a component model like FRACTAL with relevant abstractions such as threads, protection rings, or security domains. The FRACTAL Architecture Description Language (ADL) is extended by means of properties that tag components, bindings, and interfaces of the system architectural definition with execution schemes, dynamic reconfiguration strategies, protection and isolation patterns, or QoS features. Each extension captures a property-specific "system view" offering a sound basis to address some non-functional requirement. These extensions were experimented in the THINK framework, a C-based implementation of FRACTAL. Results show that THINK provides a generic and efficient approach to fully support these extensions thanks to a customizable toolchain.

Wireless sensor networks (WSNs) have witnessed a tremendous upsurge in recent years, both in academia and industry; this is mainly attributed to their unprecedented operating conditions and a variety of commercially viable applications. Because of their dependence on scarce battery power, communication protocols need to be energy efficient. However, finding the optimal solution is challenging as it needs to consider the whole communication stack at once. In this paper, we propose an approach that aims at optimizing jointly L2 (link) and L3 (routing) protocols. We design 1-hopMAC, a communication architecture grouping MAC and routing layers which avoids 1-hop neighborhood knowledge. 1-hopMAC can be combined, among others, with a geographic or gradient based routing protocols. We present an analytical study of energy consumption to point out the optimal configuration of 1-hopMAC