Performance Evaluation Of Multiband CSMA/CA With RTS/CTS For M2M Communication With Finite Retransmission Strategy

International audienceM2M communication is information exchange between machines and machines without any human interaction. M2M commu-nication based on cellular network suffers from the extremely large number of devices in service coverage. In cellular network case, the large number of devices lead to communication problem caused by collisions between the senders. In this work we study the collision probability, saturation throughput and packet error rate for the carrier sense multiple access collision avoidance (CSMA/CA) protocol with request to send and clear to send (RTS/CTS) mechanism in the case of frequency band division. We propose in this paper a modified version of CSMA/CA-RTS/CTS to be compatible with the band repartition technique and we prove that an important gain is introduced in terms of system performance especially for loaded networks. Different backoff stage numbers with different finite retransmission limit values are investigated. Simulations highlight that dividing the RTS band into independent channels reduces drastically the RTS collision probability and in particular the packet error rate. A gain in terms of saturation throughput is also demonstrated especially in charged networks mode

Effects of grain sampling procedures on fusarium mycotoxin assays in wheat grains

International audienceFusarium mycotoxins are increasingly studied agronomically, chemically, and pathologically in the context of food safety, as a means of preventing new major health crises. Reliable mycotoxin techniques and sampling procedures are required for assessment of the effects of different sources of variation on grain mycotoxin content in agronomic experiments. Analyses were performed with the aim of formulating guidelines for grain sampling to increase the reliability of grain mycotoxin measurement in agronomic experiments. Two toxins in wheat samples, deoxynivalenol and nivalenol, were targeted. With a nested linear mixed model, it was estimated that the uncertainty of nivalenol determination was low (+/-15 microg/kg), whereas that for deoxynivalenol determination was higher (+/-38 microg/kg). It was also found that grinding of the grain decreased the variability of the results. Moreover, despite the heterogeneity in grain mycotoxin content across a given field, it was shown that heads can be harvested manually for agronomic experiments provided that sampling is representative (evenly distributed over the entire plot area). Finally, delaying the assay until after harvest was found to affect the results obtained and should therefore be avoided

DFT-s-OFDM for sub-THz Transmission -- Tracking and Compensation of Phase Noise

For future wireless communication technologies, an increase in capabilities such as throughput is strongly expected. Transmission in the sub-THz bands (>90 GHz) seems to be the potential solution to meet the ever-increasing capacity demands due to the large unexploited bandwidth. Oscillators used at these frequencies generate phase noise that induces critical distortions in the signal that must be addressed. The correlated nature of PN makes it difficult to overcome. Nowadays, there is a growing interest in considering the extension of multicarrier based waveforms of the 5G new radio for transmissions in the sub-THz bands. In this paper, we introduce a new algorithm called the interpolation filter (IF), which efficiently estimates and compensates PN effects on DFT-s-OFDM systems. Specifically, it is based on the use of stochastic properties of the PN and is compatible with the 3GPP phase tracking reference signal scheme. We highlight a performance improvement over known techniques when using high-order modulation.Comment: Paper accepted and will be presented at the IEEE CCNC 2023 Conference that will be held in Las Vegas from January 8th to 11th, 202

Effect of seeders and tillage equipment on vertical distribution of oilseed rape stubble

International audienceWhen the spreading of a disease depends on the proportion of infected residues remaining at soil surface it is of crucial importance to analyse the effects of tillage practices on the vertical distribution of stubble. This is the case with phoma stem canker (blackleg), whose epidemics are initiated in autumn, by air-borne ascospores released from stubble located at the soil surface. We compared initial vertical distribution of oilseed rape residues to those observed after sowing and various tillage operations (rotary harrowing, stubble disking, chiselling and mouldboard ploughing). Almost 20% of the initially buried residue was brought back to soil surface with seeding. Rotary harrow brought 40% of the residue buried in the 0-10 cm layer up to the surface and left unburied about 70% of surface residue. Stubble disking appeared to be more efficient for residue burial than chiselling. Mouldboard plough was the only tool that buried all residues. A simple model was developed that predicted burial and return to the soil surface of potentially infected residues as a function of tillage practices used after harvest. Simulation of different tillage sequences showed that the order in which tools were used also affected location of residues. Our results highlighted the importance of tillage in the cultural control of phoma stem canker and will contribute to the definition of integrated pest management strategies for oilseed rape

Fusarium head blight: epidemiological origin of the effects of cultural practices on head blight attacks and the production of mycotoxins by Fusarium in wheat grains

International audienceFusarium head blight is an ancient disease and is very common throughout the world. In this article, we review current knowledge concerning the effects of cultural practices on the development of head blight and the production of toxins in the field. The qualitative effects of these practices on the severity of the disease and/or the production of toxins are in the process of being elucidated but, in many cases, detailed studies have not yet been carried out or conflicting results have been obtained. However, it should be noted that these effects have not yet been quantified. Three different cultural practices are today considered to be of prime importance for combating this disease and the production of mycotoxins: deep tillage, the choice of the preceding crop in the rotation and the choice of appropriate cultivar, as varietal effects exist

Effects of crop management and surrounding field environment on insect incidence in organic winter oilseed rape (Brassica napus L.)

Many organic farmers hesitate to grow winter oilseed rape (WOSR), despite its usefulness for crop rotations and animal fodder, because it is attacked by many insects, which are difficult to control without chemical treatments. In a geographically broad network of farmer’s fields, we analysed the effect of various crop management factors and of the surrounding field environment on a large range of insects known to damage WOSR: root maggot (Delia radicum L.), cabbage stem flea beetle (Psylliodes chrysocephala L.), rape stem weevil (Ceuthorhynchus napi Gyl) and pollen beetle (Meligethes aeneus F.). Our results confirm the effect of sowing date, plant density and soil tillage regime on root maggot attacks and cabbage stem flea beetle larva infestation. Early sowing tended to increase root maggot damage whereas it was associated with a lower level of attack of cabbage stem flea beetle. High plant density tended to decrease the damage or the attack of all insects. We show that nitrogen availability in the soil affect cabbage stem flea beetle, stem weevil levels and pollen beetle damage: the negative effect of soil nitrogen content on pollen beetle damage may be related to the significant effect of nitrogen on plant vigour and, therefore, to the compensation of pollen beetle damage on new racemes. If all insects were considered together, the proportion of land under WOSR in the region and the surrounding environment had a significant effect on pest occurrence. In regions with a high proportion of land under WOSR, the proportion of plants attacked by root maggot and pollen beetle tended to increase. Conversely, regions with high proportions of land under WOSR tended to have a smaller proportion of plants with cabbage stem flea beetle larvae or damage, whatever the environment surrounding the field. For almost all the pests considered, the fields displaying the most severe pest attacks in regions with more than 1.2% WOSR were bounded by trees, hedges and bushes. Conversely, in regions with a lower percentage of land under WOSR, woodland around the field reduced the occurrence of pest attack

Analysis of Frequency Channel Division Strategy for CSMA/CA with RTS/CTS Mechanism

International audience—In this work we study the collision probability, saturation throughput and statistical delay for the carrier sense multiple access collision avoidance (CSMA/CA) protocol with request to send and clear to send (RTS/CTS) mechanism in the case of frequency channel division. We propose in this paper a modified version of CSMA/CA-RTS/CTS to be compatible with the channel repartition technique and we prove that an important gain is introduced in terms of system performance especially for loaded networks. Simulations highlight that dividing the channel into independent sub-channels reduces drastically the RTS collision probability. Moreover, a gain in terms of saturation throughput and delay is shown especially in dense networks. Index Terms—Carrier senses multiple access/collision avoid-ance (CSMA/CA), Frequency channel division, RTS/CTS, MAC protocol

Channel estimation strategy for LPWA transmission at low SNR: application to Turbo-FSK

International audienceTurbo Frequency Shift Keying has been considered as a promising physical layer for low power wide-area network connectivity. Because of its constant envelope amplitude and the efficiency of its iterative receiver performance close to Shannon's limit can be achieved. However, results published so far in the literature for the waveform have assumed perfect channel estimation or Signal-to-noise (SNR) levels that are higher than the SNR levels considered for these applications. This paper analyzes a channel estimation strategy based on a specifically adapted pilot sequence. Simulations have been performed to evaluate the performance of the proposed approach. Performance loss induced by imperfect channel estimation algorithms is estimated

Étude d'irradiations électroniques de faible énergie d'hexadécanethiols chimisorbés sur des nanoparticules d'or et des surfaces d'or à basse température

Le domaine des monocouches autoassemblées (SAMs) est bien connu depuis une vingtaine d'année, quoique les phénomènes de bris moléculaire dans un tel environnement compact ne commencent qu'à être étudiés. Ces monocouches sont ordonnées et hautement structurées telles que le démontrent les études de microscopie à effet tunnel (STM) et de spectroscopie infrarouge en réflexion-absorption (IRRAS). Les expériences d'irradiations électroniques de faible énergie sur des SAMs ont démontré un processus résonant d'attachement dissociatif des électrons (DEA) à une énergie spécifique de 10 eV. Les modifications induites par l'impact des électrons sont préférentiellement situées à l'interface film/vide car la proximité du substrat métallique entraîne une relaxation non radiative des états excités anioniques, [RC-H][indice supérieur *-] . On a mesuré un temps de vie de désexcitation de l'état excité de 0,2-0,5 fs pour les méthyles d'une SAM de butanethiols alors qu'il est de 5-10 fs pour les méthyles d'une SAM d'hexadécanethiols. Considérant que le temps de dissociation du lien C-H est d'une durée d'environ 5,2 fs et que le système de relaxation soit en compétition de manière efficace, ceci explique que pour les chaînes plus courtes, la dissociation n'est pas perceptible car aucune modification dans le spectre infrarouge (IR) n'est apparente en fonction de la charge appliquée. Le mécanisme utilisé pour expliquer la diminution des bandes infrarouges est la déshydrogénation, phénomène exothermique d'environ 6 eV lors d'irradiations électroniques de 10 eV."--Résumé abrégé par UMI