1,720,962 research outputs found
CRYSTAL Clear – Making Interference Transparent (EWSN Dependability Competition)
No full textTo address the challenges of the EWSN dependability competition we extended our synchronous transmission protocol, CRYSTAL, with techniques to mitigate interference -- channel hopping and noise detection -- and with the capability to deliver aperiodic events to multiple actuators
RPL, the Routing Standard for the Internet of Things ... Or Is It?
No full textRPL, the IPv6 Routing Protocol for Low-Power and Lossy Networks, is considered the de facto routing protocol for the Internet of Things (IoT). Since its standardization, RPL contributed to the advancement of communications in the world of tiny, embedded, networking devices, by providing, along with other standards, a baseline architecture for IoT. Several years later, we analyze the extent to which RPL lived up to the expectations defined by the IETF requirements, and tie our analysis to current trends, identifying the challenges RPL must face to remain on the forefront of IoT technology
Interference-Resilient Ultra-Low Power Aperiodic Data Collection
No full textAperiodic data collection received little attention in wireless sensor networks, compared to its periodic counterpart.
The recent Crystal system uses synchronous transmissions to support aperiodic traffic with near-perfect reliability, low latency, and ultra-low power consumption. However, its performance is known under mild interference—a concern, as Crystal relies heavily on the (noise-sensitive) capture effect and targets aperiodic traffic where “every packet counts”.
We exploit a 49-node indoor testbed where, in contrast to existing evaluations using only naturally present interference to evaluate synchronous systems, we rely on JamLab to generate noise patterns that are not only more disruptive and extensive, but also reproducible. We show that a properly configured, unmodified Crystal yields perfect reliability (unlike Glossy) in several noise scenarios, but cannot sustain extreme ones (e.g., an emulated microwave oven near the sink) that instead are handled by routing-based approaches. We extend Crystal with techniques known to mitigate interference—channel hopping and noise detection—and demonstrate that these allow Crystal to achieve performance akin to the original even under multiple sources of strong interferenc
D-RPL: Overcoming memory limitations in RPL point-to-multipoint routing
Full text linkRPL, the IPv6 Routing Protocol for Low-Power and Lossy Networks, supports both upward and downward traffic. The latter is fundamental for actuation, for queries, and for any bidirectional protocol such as TCP, yet its support is compromised by memory limitation in the nodes. In RPL storing mode, nodes store routing entries for each destination in their sub-graph, limiting the size of the network, and often leading to unreachable nodes and protocol failures. We propose here D-RPL, a mechanism that overcomes the scalability limitation by mending storing mode forwarding with multicast-based dissemination. Our modification has minimal impact on code size and memory usage. D-RPL is activated only when memory limits are reached, and affects only the portion of the traffic and the segments of the network that have exceeded memory limits. We evaluate our solution using Cooja emulation over different synthetic topologies, showing a six-fold improvement in scalability
The Wireless Control Bus: Enabling Efficient Multi-Hop Event-Triggered Control with Concurrent Transmissions
Full text linkEvent-triggered control (ETC) holds the potential to significantly improve the efficiency of wireless networked control systems. Unfortunately, its real-world impact has hitherto been hampered by the lack of a network stack able to transfer its benefits from theory to practice specifically by supporting the latency and reliability requirements of the aperiodic communication ETC induces. This is precisely the contribution of this article.Our Wireless Control Bus (WCB) exploits carefully orchestrated network-wide floods of concurrent transmissions to minimize overhead during quiescent, steady-state periods, and ensures timely and reliable collection of sensor readings and dissemination of actuation commands when an ETC triggering condition is violated. Using a cyber-physical testbed emulating a water distribution system controlled over a real-world multi-hop wireless network, we show that ETC over WCB achieves the same quality of periodic control at a fraction of the energy costs, therefore unleashing and concretely demonstrating its full potential for the first time.Team Manuel Mazo J
Janus: Dual-radio Accurate and Energy-Efficient Proximity Detection
No full textProximity detection is at the core of several mobile and ubiquitous computing applications. These include reactive use cases, e.g., alerting individuals of hazards or interaction opportunities, and others concerned only with logging proximity data, e.g., for offline analysis and modeling. Common approaches rely on Bluetooth Low Energy (BLE) or ultra-wideband (UWB) radios. Nevertheless, these strike opposite tradeoffs between the accuracy of distance estimates quantifying proximity and the energy efficiency affecting system lifetime, effectively forcing a choice between the two and ultimately constraining applicability.
Janus reconciles these dimensions in a dual-radio protocol enabling accurate and energy-efficient proximity detection, where the energy-savvy BLE is exploited to discover devices and coordinate their distance measurements, acquired via the energy-hungry UWB. A model supports domain experts in configuring Janus for their use cases with predictable performance. The latency, reliability, and accuracy of Janus are evaluated experimentally, including realistic scenarios endowed with the mm-level ground truth provided by a motion capture system. Energy measurements show that Janus achieves weeks to months of autonomous operation, depending on the use case configuration. Finally, several large-scale campaigns exemplify its practical usefulness in real-world contexts
Dual-radio discovery and ranging for infrastructure-less social distancing with Janus
No full textDevices to support social distancing must be energy-efficient and accurate. Bluetooth Low Energy (BLE) meets the first criteria but falls short on the latter. Ultra-wideband (UWB) measures distances with <10 cm error but with relatively high consumption. Therefore, we built Janus, a dual-radio protocol that uses the strengths of each
Measuring close proximity interactions in summer camps during the COVID-19 pandemic
Full text linkPolicy makers have implemented multiple non-pharmaceutical strategies to mitigate the COVID-19 worldwide crisis. Interventions had the aim of reducing close proximity interactions, which drive the spread of the disease. A deeper knowledge of human physical interactions has revealed necessary, especially in all settings involving children, whose education and gathering activities should be preserved. Despite their relevance, almost no data are available on close proximity contacts among children in schools or other educational settings during the pandemic.
Contact data are usually gathered via Bluetooth, which nonetheless offers a low temporal and spatial resolution. Recently, ultra-wideband (UWB) radios emerged as a more accurate alternative that nonetheless exhibits a significantly higher energy consumption, limiting in-field studies. In this paper, we leverage a novel approach, embodied by the Janus system that combines these radios by exploiting their complementary benefits. The very accurate proximity data gathered in-field by Janus, once augmented with several metadata, unlocks unprecedented levels of information, enabling the development of novel multi-level risk analyses.
By means of this technology, we have collected real contact data of children and educators in three summer camps during summer 2020 in the province of Trento, Italy. The wide variety of performed daily activities induced multiple individual behaviors, allowing a rich investigation of social environments from the contagion risk perspective. We consider risk based on duration and proximity of contacts and classify interactions according to different risk levels. We can then evaluate the summer camps’ organization, observe the effect of partition in small groups, or social bubbles, and identify the organized activities that mitigate the riskier behaviors.
Overall, we offer an insight into the educator-child and child-child social interactions during the pandemic, thus providing a valuable tool for schools, summer camps, and policy makers to (re)structure educational activities safely
Harmonizing Actuation and Data Collection in Low-power and Lossy Networks: From Standard Compliance to Rethinking the Stack
No full textTechnology is evolving towards a higher degree of automation and connectivity, with concepts of Pervasive Computing, Smart Factories, Cyber-Physical Systems (CPS) and the Internet of Things (IoT)promising to integrate countless communicating devices into objects around us at home, in the streets, and on industrial sites. These embedded devices are often very small in size, autonomously-powered, and have restricted computational and communicational capabilities.
Low-power and Lossy Networks (LLNs) are multi-hop, typically wireless, self-organising networks aimed at interconnecting hundreds or thousands of such embedded devices. They inherit many techniques from wireless sensor networks, though going beyond their original task of collecting sensor readings. New applications comprising actuators, control loops, user interface devices and requiring connectivity of every ``smart thing'' with the Internet, pose new challenges to the network protocol stacks.
These stacks should not only efficiently support data collection from numerous low-power sensors, but provide scalable data forwarding in the opposite direction, making every single device in the LLN addressable and reachable from a central controller or from the Internet. This type of forwarding is needed to send commands to wireless actuators in the LLN or to enable request-response communication between a low-power device and a remote server.
Control loops additionally require real-time guarantees from the communication system. We demonstrate in this thesis that reconciling the battery lifetime with high reliability and low latency is still a challenge for existing protocols even at the scale of few hundreds of network nodes.
Moreover, current techniques have a significant performance gap between their data collection and actuation forwarding components on memory-constrained platforms.
This gap limits the applicability of the stacks, as the overall performance is determined by the weaker component.
Motivated by two real-life applications, we first study novel techniques that eliminate the performance gap in the
standard IPv6 stack for LLNs, making the actuation traffic forwarding as performant as the data collection one in networks that are five times larger than what the original standard stack is able to support. Second, we demonstrate that the reliability of packet delivery in the standard-compliant solution is limited in practice at around 99% while its routing overhead causes significant inefficiency in energy consumption. Therefore, we change focus to a forwarding mechanism based on the principle of synchronous transmissions, made popular by Glossy. It is a recent and, thus, non-standard technique, known for excellent reliability, speed and energy efficiency of the flooding-based data dissemination service it provides. This service is a perfect match for actuation, but a similarly efficient data collection protocol did not exist. To close this gap, we design Crystal, a novel data collection protocol based on the same core principle of synchronous transmissions.
We show that, depending on the application, Crystal reaches per-mille or even parts-per-million radio duty cycle.
It does that with a packet loss rate lower than 10e-5 under external Wi-Fi interference of a noisy office building, and
provides a much higher reliability and energy efficiency than the state of the art under even stronger interference generated by JamLab. We thoroughly evaluate the proposed solutions both in realistic simulations and two large-scale testbeds. We follow a principled approach based on understanding of the environment and the properties of the network topologies. The latter are acquired by our connectivity assessment tool Trident, which itself is one of the contributions of this thesis.
Through these contributions, this thesis pushes forward the applicability of LLNs, by improving their scalability, reliability, latency, energy efficiency and interference resilience, both in the context of an existing standard and in a clean-slate design. Further, by achieving this superior performance via network stacks that natively support both collection and actuation traffic, this thesis provides a stepping stone for applications that strongly rely on both,
notably including the low-power wireless control applications
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