Littérature scientifique sur le sujet « Canaux de fondu sans fil »
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Consultez les listes thématiques d’articles de revues, de livres, de thèses, de rapports de conférences et d’autres sources académiques sur le sujet « Canaux de fondu sans fil ».
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Articles de revues sur le sujet "Canaux de fondu sans fil"
Gow, Gordon A. « Public Safety Telecommunications in Canada : Regulatory Intervention in the Development of Wireless E9-1-1 ». Canadian Journal of Communication 30, no 1 (24 janvier 2005). http://dx.doi.org/10.22230/cjc.2005v30n1a1511.
Texte intégralLapierre, Nicole. « Mémoire ». Anthropen, 2017. http://dx.doi.org/10.17184/eac.anthropen.055.
Texte intégralAuger, Reginald, et Allison Bain. « Anthropologie et archéologie ». Anthropen, 2016. http://dx.doi.org/10.17184/eac.anthropen.030.
Texte intégralThèses sur le sujet "Canaux de fondu sans fil"
Zhao, Hui. « High performance cache-aided downlink systems : novel algorithms and analysis ». Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS366.
Texte intégralThe thesis first addresses the worst-user bottleneck of wireless coded caching, which is known to severely diminish cache-aided multicasting gains. We present a novel scheme, called aggregated coded caching, which can fully recover the coded caching gains by capitalizing on the shared side information brought about by the effectively unavoidable file-size constraint. The thesis then transitions to scenarios with transmitters with multi-antenna arrays. In particular, we now consider the multi-antenna cache-aided multi-user scenario, where the multi-antenna transmitter delivers coded caching streams, thus being able to serve multiple users at a time, with a reduced radio frequency (RF) chains. By doing so, coded caching can assist a simple analog beamformer (only a single RF chain), thus incurring considerable power and hardware savings. Finally, after removing the RF-chain limitation, the thesis studies the performance of the vector coded caching technique, and reveals that this technique can achieve, under several realistic assumptions, a multiplicative sum-rate boost over the optimized cacheless multi-antenna counterpart. In particular, for a given downlink MIMO system already optimized to exploit both multiplexing and beamforming gains, our analysis answers a simple question: What is the multiplicative throughput boost obtained from introducing reasonably-sized receiver-side caches?
Ahmed, Ouameur Messaoud. « Modélisation et estimation de canaux pour les communications sans fil / ». Trois-Rivières : Université du Québec à Trois-Rivières, 2002. http://www.uqtr.ca/biblio/notice/resume/03-2246374R.html.
Texte intégralAhmed, Ouameur Messaoud. « Modélisation et estimation de canaux pour les communications sans fil ». Thèse, Université du Québec à Trois-Rivières, 2002. http://depot-e.uqtr.ca/3990/1/000102243.pdf.
Texte intégralEl, Fatni Abdelaziz. « Modélisation, analyse et conception de protocoles MAC multi-canaux dans les réseaux sans fil ». Thesis, Toulouse 2, 2013. http://www.theses.fr/2013TOU20033.
Texte intégralThe use of multi-channel communications in MAC protocols (multi-channel MAC) for wireless networks can significantly improve the network throughput compared with single channel MAC protocols since concurrent transmissions can take place simultaneously on distinct non-overlapping channels without interfering. However, due to the multi-channel environment, a novel issue must be addressed in MAC protocols, which is called "the channel assignment mechanism" in order to coordinate the channels access. The role of this mechanism is to enable nodes to agree on which channel should be used and when for data transmission in a distributed way. The absence of this mechanism or a bad coordination of the channel usage can incur the opposite effect to that intended. Thus, the efficiency of a multi-channel MAC protocol depends strictly on the efficiency of the channel assignment mechanism, which also must provide the guarantees necessary to the good behavior of the multi-channel communications. In this thesis, we focus on the modeling, analysis, and design of new multi-channel MAC protocols in wireless networks. Firstly, we focus on the formal specification and verification of fundamental properties inherent to the activities of the channel assignment and its impact on the data transfer for the main multi-channel MAC approaches proposed in the literature. Secondly, we aim to propose, model and analyze formally two new multichannel MAC protocols, resulting from the qualitative analysis conducted. Finally, a quantitative and comparative study is conducted to analyze the performance of the proposed protocols in terms of the throughput and the impact of the switching time between channels
Haggui, Haithem. « Estimation et égalisation des canaux sans fil épars utilisant l’algorithme des moindres carrés récursifs épars SPARLS ». Mémoire, École de technologie supérieure, 2012. http://espace.etsmtl.ca/1103/1/HAGGUI_Haithem.pdf.
Texte intégralAgueh, Djidjoho Max. « Protection inégale pour la transmission d'images et vidéo codées en Jpeg 2000 sur les canaux sans fil ». Nantes, 2008. http://www.theses.fr/2008NANT2069.
Texte intégralNowadays, data protection against transmission errors in wireless multimedia systems is a crucial issue. JPEG 2000, the new image representation system, addresses this issue by defining in its 11th part (Wireless JPEG 2000 - JPWL) some tools such as Forward Error Correction with Reed-solomon (RS) codes in order to enhance the robustness of JPEG 2000 based images and videos against transmission errors. Although JPWL defines a set of RS codes for data protection, it does not specify how to select those codes in order to handle error rate in wireless multimedia systems. In our work, based on the analysis of 802. 11 based Ad-hoc network traces, we first derive application level channel models (Gilbert model). Then, we propose a methodology for JPEG 2000 images and videos protection with a priori and empiric channel code rate selection. We highlight the interest of the a priori FEC allocation methodology by comparing it to non protected data transmission. We show that the effectiveness of the proposed scheme can be drastically reduced when the channel state changes because the FEC rate allocation is not adaptative. In this context, we propose a dynamic FEC rate allocation methodology which is a layer-based unequal error protection scheme. We demonstrate the effectiveness of this scheme thanks to a wireless client/server JPEG 2000 based images and video streaming application. The dynamic FEC rate allocation scheme overcomes in order of 10% other existing schemes such as the layer-based unequal error protection scheme proposed by Zhaohoui Guo et al both in terms of Peak Signal to Noise Ratio (PSNR) and successful image decoding rate. However, despite their effectiveness layer-based schemes are sub-optimal because they do not take into account the importance of data packets which limits their performances particularly in highly varying environments. We then propose an optimal FEC rate allocation methodology which is a packet-based unequal error protection scheme. The proposed scheme is slightly more complex than layer-based schemes as far as the number of packets constituting the JPEG 2000 image is low (under 1000 packets) and it offers superior performances in terms of PSNR and successful decoding rate. However, if the number of JPEG 2000 packet is significantly important (more than 1000 packets) the optimal methodology can be inefficient for real-time streaming application due it complexity. Beyond the proposition of FEC rate allocation methodologies, our work can be viewed as a step toward the guaranty of Quality of Service (QoS) in wireless multimedia applications
Shenoy, Kaup Shakti Prasad. « Communications efficaces sur des canaux sans fil : nouveaux résultats de l'égalisation, la diversité et l'alignement des interférences ». Paris, ENST, 2010. http://www.theses.fr/2010ENST0046.
Texte intégralThe first part of the thesis studies receiver designs that maximize the data throughput in the high speed downlink packet access (HSDPA). We propose two-stage equalization for both single antenna (SISO) and multiple antenna (MIMO) frequency selective channels. The first stage consists of chip-level processing and the second stage of processing takes place at the symbol level. The second part of the thesis is devoted mainly to theoretical analysis of the diversity order of linear equalization (LE) for transmission in fading channels. We show here that the same precoder also allows linear, decision feedback and ``hybrid" equalization schemes to achieve the same diversity gains as that of MLE. We also devote our attention to low-complexity implementations of these full diversity equalizers. It also appears that a redundancy proportional to channel delay spread is largely enough to allow MLE to collect full channel diversity. We present simulation results that support this observation. In the final part of the thesis we study communication over flat fading multiple input multiple output (MIMO) interference channels (IFC). We address here the most general case of the MIMO IFC and are able to show that, when an IA solution exists, these conditions are satisfied at every step of the proposed recursive algorithm and that an IA solution does not exist when these conditions are not satisfied
Kharrat, Fatma. « Techniques adaptatives et classification pour les canaux à antennes multiples ». Paris, ENST, 2006. http://www.theses.fr/2006ENST0041.
Texte intégralThis thesis report focuses on wireless communication systems with multiple transmit and multiple receive antennas. At first, we study the performance of such systems assuming a spatial multiplexing scheme at the transmitter and an ML detection at the receiver. We derive an accurate approximation for the conditional error probability on a quasi static channel. This approximation is computed when distinct modulations are applied on the transmit antennas and for any MIMO channel configuration. Then, we outline some adaptive techniques for MIMO systems: adaptive modulation and antenna selection. The first one adjusts the modulations on transmit antennas according to the channel conditions in order to maximize the spectral efficiency while satisfying a constraint on error probability. The second technique selects the set of active antennas to optimize the chosen selection criterion (e. G. Maximize the capacity, etc) providing a channel estimation. Both adaptive techniques need a relevant matric to evaluate the MIMO system performance. We propose a new adaptive modulation scheme and antenna selection algorithm where the derived error probability approximation is used as a selection metric. Finally, we consider the quantization of MIMO channels. This quantization, in our terminology classification, allows the partitioning of MIMO channels set into different classes, where each class is identified by a representative. This method could be used for adaptive techniques to find the best adjustable parameters. We describe our MIMO classification algorithm and we illustrate its application for closed-loop MIMO systems, e. G beamforming
Toham, Carine. « Routage et contrôle de puissance dans les réseaux ad hoc multi-interfaces et multi-canaux ». Grenoble INPG, 2008. http://www.theses.fr/2008INPG0108.
Texte intégralWe consider the problem of throughput improvement in multi-hop ad hoc networks. The shared radio medium implies to handle the interferences between the nodes in the network. The limited node radio range also mandates some constraints such as the distance between the transmitter and the receiver. These two main facts limit the network performance, notably the throughput. We propose a solutio~ that takes advantage of nodes equipped with multiple network cards (interfaces) and that use multiple frequency bands (channels) for transmitting data. We improve the network throughput by combining an efficient transmission link channel assignment with a suitable routing metric that privileges the alternation of good quality channels along the routes. A power control mechanism complements that scheme by favouring each channel reuse
Mossanen, Amini Réza. « Un cadre économique pour le routage et l'allocation de canaux dans les réseaux maillés sans fil avec la radio cognitive ». Mémoire, École de technologie supérieure, 2013. http://espace.etsmtl.ca/1217/1/MOSSANEN_AMINI_R%C3%A9za.pdf.
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