GRAPMAN: Gradual Power Manager for Consistent Throughput of Energy Harvesting Wireless Sensor Nodes

International audienceIn this work, Wireless Sensor Network (WSN) applications that require long-term sustainability are considered. Energy harvesting forms a promising technology to address this challenge, by allowing each node to be entirely powered by energy harvested from its environment. To be sustainable, each node must dynamically adapt its Quality of Service (QoS), regarding the harvested energy using a power management strategy. This strategy is implemented on each node by the Power Manager (PM). In this paper, GRAPMAN (GRAdual Power MANager) is proposed, a novel PM for Energy-Harvesting WSN (EH-WSN) powered by pseudo-periodic energy sources. Unlike most state of the art PMs, GRAPMAN aims to achieve high average throughput while maintaining consistent QoS, i.e. with low fluctuations with respect to time, by looking for the highest throughput that can be supplied by the node over a finite time horizon while remaining sustainable. We show through extensive trace-driven network simulations that GRAPMAN outperforms state of the art PMs in both average throughput and throughput consistency

On the performance of distributed space-time coded cooperative relay networks based on inter-relay communications

International audienceA new protocol, called fully distributed space-time coded (FDSTC) protocol having information exchange between relays, is proposed and compared with the conventional distributed space-time coded (DSTC) protocol using non-regenerative relays (NR-relays) and regenerative relays (R-relays). Closed-form error probabilities are derived to verify the simulations. In terms of error performance, the FDSTC protocol gets significant average signal-to-noise ratio (SNR) gains (3.7 dB for NR-relays and 18.1 dB for R-relays). In addition, the impact of the relative distance of relays on the required SNR is reduced up to 70%. The system diversity order using the FDSTC protocol is higher than that using the DSTC protocol (especially, the FDSTC protocol obtains full diversity with NR-relays). As a result, at the same spectral efficiency, FDSTC has better performance in terms of outage probability in high SNR regions. In terms of energy efficiency, the FDSTC protocol is shown to outperform DSTC for long-range transmissions

Non-Regenerative Full Distributed Space-Time Codes in Cooperative Relaying Networks

International audienceDistributed space-time codes (DSTC) are often used in cooperative relaying networks whose relays can support a single antenna due to the limited physical size. In this paper, full DSTC protocol in which there is a data exchange between relays before forwarding signals to destination is proposed to improve the performance of a cooperative relaying system. A lower bound for the average symbol error probability (ASEP) of full DSTC cooperative relaying system in a Rayleigh fading environment is provided. In the case when the Signal to Noise Ratio (SNR) of the relay-relay link is much greater than that of the source-relay link, the upper bound on ASEP of this system is also derived. From the simulations, we show that the average SNR gain of full DSTC system over DSTC system is 3.8dB and the maximum SNR gain is 5dB when the relay-relay distance is small and the relays are in the middle of the source and the destination. The effect of the distance between the relays shows that the performance does not degrade so much as the distance between relays is lower than a half of the source-destination distance. Moreover, we also show that when the error synchronization range is lower than 0.5, the impact of the transmission synchronization error of the relay-destination link on the performance is not considerable

Protocoles de communication faibles latences et faibles consommations à base de wake-up radio

International audienceLa durée de vie est une caractéristique importante des réseaux de capteurs. La communication etant généralement la tâche la plus gourmande en energie, de nombreux protocoles de communication ont eté proposés afin de réduire les communications, ils reposent majoritairement sur le concept du réveil périodique des noeuds. Toutefois, ces dernières années, de nouveaux types de récepteurs Ultra Low Power (ULP), appelés wake-up radios, sont apparus. Ces dispositifs permettent l'écoute en continu du canal de communication tout en ayant une consommation d'énergie au moins un ordre de grandeur inférieur à celle des emetteurs-récepteurs typiques. La wake-up radio ne peut réveiller le reste du système qu'en cas de besoin, minimisant ainsi l'écoute inutile. Dans cette étude, nous présentons une expérimentation et une étude analytique qui permettent le dimensionnement des protocoles de communication utilisant les wake-up radios

Asynchronous MAC Protocol for Spectrum Agility in Wireless Body Area Sensor Networks

International audienceA Wireless Body Area Sensor Network (WBASN) is a special-purpose Wireless Sensor Network (WSN) that supports remote monitoring and entertainment applications. The energy consumption plays an important role in the design of this specific sensor network. Unfortunately, the performance of WBASNs decreases in high interference environments such as the Industrial, Scientific and Medical (ISM) band where wireless spectrums are getting crowded. In this paper, an energy-efficient Medium Access Control (MAC) protocol named C-RICER (Cognitive-Receiver Initiated CyclEd Receiver) is specifically designed for WBASN to cognitively work in high interference environment. C-RICER protocol adapts both transmission power and channel frequency to reduce the interferences and thus, the energy consumption. The protocol is simulated thanks to OMNET++ simulator. Simulation results show that, depending on the interference level, C-RICER is able to outperform the traditional RICER protocol in terms of energy consumption, packet delay, and network throughput

Un écosystème Julia pour prototyper efficacement des radios logicielles

National audienceSDRs are immensely popular as they allow to have a flexible approach for sounding, monitoring or processing radio signals through the use of generic analog components and lots of digital signal processing. As, in this paradigm, most of the processing are done at software level (i.e. on a CPU), an efficient software methodology has to be envisioned. Right now, most of the existing methods focus either on low-level languages (e.g. C or C++) for good runtime performance at the cost of easy prototyping or on high-level languages (such as Python) for flexibility at the price of runtime performance. In this article, we propose a new methodology based on Julia language that addresses this two-language problem and paves the way for efficient prototyping without giving up runtime performance. To prove the benefits of the proposed approach, a performance benchmark with several optimisation levels compares the Julia approach with C++ and Python ones.Ce papier présente une nouvelle approche de prototypage rapide et efficace à partir du langage Julia. Les radios logicielles sont des architectures radio-fréquences (RF) qui permettent de capter un signal électro-magnétique et de le traiter numériquement avec des processeurs de calcul. Du fait leur flexibilité RF et numérique, les radios logicielles sont des outils précieux largement déployés dans des contextes très divers. La majorité de la chaîne de traitement se faisant via un logiciel, il convient de choisir un langage de programmation qui garantisse cette flexibilité. Les stratégies classiques s'appuient sur des langages de description bas-niveau (e.g. C/C++), pour garantir les performances d'exécution au détriment de la simplicité de conception, ou des approches haut-niveau (e.g. Python) pour offrir une grande capacité d'abstraction au détriment des performances. Dans cet article, nous introduisons une nouvelle méthodologie basée sur le langage Julia qui adresse ce problème du "double langage". Nous proposons un ensemble d'outils pour piloter des radios logicielles et nous démontrons par l'intermédiaire d'un benchmark que les performances obtenues avec l'approche Julia sont très intéressantes

Performances de LoRa sur les canaux de Rice et Nakagami

International audienceLes applications telles que les fermes connectées, les villes intelligentes ou l'industrie 4.0 utilisent de plus en plus les Low Power Wide Area Networks (LPWAN), permettant un bon compromis entre la portée, le débit et la consommation d'énergie. Cependant, seulement quelques études théoriques sont disponibles pour aider à la conception de ces réseaux avant un déploiement. Une nouvelle approche basée sur la fonction de Marcum est proposée ici pour estimer la probabilité d'erreur binaire de LoRa. La méthode proposée est appliquée avec un bruit gaussien pour les canaux de Nakagami et Rice

Evaluation rapide et précise des performances d'une communication LoRa basée sur la fonction de Marcum

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How robust is a LoRa communication against impulsive noise?

International audienceIn the last decade Internet of Things (IoT) grew up in an exponential behavior with applications requiring long range and low power wireless transmissions. Factory of the Future (FoF), also called Industry 4.0, aims to use IoT technologies to enhance productivity, therefore adding high reliability constraints. Several IoT standards were proposed and LoRa has emerged as a high potential candidate for a variety of applications. LoRa modulation is based on a chirp spread-spectrum technique and offers efficient transmission up to 50 kbps over several kilometers. The performance of LoRa in terms of symbol or bit error probability has been theoretically analyzed in few recent papers for a Gaussian channel. However, the industrial environment is often corrupted with impulsive non Gaussian noise generated by high-power equipment. In this paper, the impact of impulsive noise, modeled by the Middleton Class-A noise, is introduced and the robustness of a LoRa communication is studied. Compared to the Gaussian case, simulations show that impulsive noise may severely degrade system performance. This Signal-to-Noise Ratio loss can reach up to 10 dB, but increasing the spreading factor can reduce the noise impact