Teses / dissertações sobre o tema "Canaux de fondu sans fil"
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Zhao, Hui. "High performance cache-aided downlink systems : novel algorithms and analysis". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS366.
Texto completo da fonteThe 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.
Texto completo da fonteAhmed, 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.
Texto completo da fonteEl, 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.
Texto completo da fonteThe 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.
Texto completo da fonteAgueh, 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.
Texto completo da fonteNowadays, 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.
Texto completo da fonteThe 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.
Texto completo da fonteThis 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.
Texto completo da fonteWe 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.
Texto completo da fonteBel, Hadj Mabrouk Ahmed. "Etude théorique et expérimentale d'un moyen d'essais permettant de reproduire les canaux de radiocommunication intra-véhicule". Rouen, 2016. http://www.theses.fr/2016ROUES005.
Texto completo da fonteVincent, Hogue Marie-Josée. "Étude comparative des estimateurs de canaux en vue d'une implantation dans un système de télécommunication sans fil de type MIMO-OFDM". Thèse, Université du Québec à Trois-Rivières, 2009. http://depot-e.uqtr.ca/1370/1/030132773.pdf.
Texto completo da fonteMheich, Zeina. "Schémas pratiques pour la diffusion (sécurisée) sur les canaux sans fils". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01059512.
Texto completo da fonteChartois, Yannick. "Étude paramétrique avancée de canaux SISO et MIMO en environnements complexes : application au système HiperLAN/2". Télécom Bretagne, 2005. http://www.theses.fr/2005TELB0003.
Texto completo da fonteMorlat, Pierre-François. "Evaluation globale des performances d'un récepteur multi-antennes, multi-standards et multi-canaux". Lyon, INSA, 2008. http://theses.insa-lyon.fr/publication/2008ISAL0133/these.pdf.
Texto completo da fonteA multi-antenna receiver structure able to deal with two 802. 11 b and/or 802. 11 g signais simultaneously in a 40 MHz bandwidth (different to the classical WLAN bandwidth 20 MHz) is defined in this thesis. This structure seems to be very relevant in order to increase QoS taking into account problem of spectral resources. Moreover, a global system evaluation scheme of the multi-* structure is proposed. So, each critical part of the receiver is not considered separately but in a global system approach. First of all, the benefits of the SIMO processing, taking into realistic propagation conditions is given in several multi-* configurations. Ln a second part of the work, it is showed the capability of the 1 x2 SI MO processing to mitigate the effect of RF impairments. After all, a numerical architecture ensuring the processing of both WLAN channels simultaneously received by the multi-branches is validate in order to develop a material demonstrator
Picol, Sylvie Patricia Marie-Yvonne. "Conception et réalisation de la partie numérique d'un simulateur matériel pour les canaux de propagation MIMO". Rennes, INSA, 2007. https://tel.archives-ouvertes.fr/tel-00339423.
Texto completo da fonteThe need to improve the capacity of wireless networks, for the data transmission and multimedia applications of the digital communication systems, has to focus on MIMO communication techniques to increase the data rate and the quality of services. MIMO systems use antenna arrays at both the transmit and the receive sides of a radio link and exploit the spatial dimension for the transmission. The performance of a communication system can be evaluated using a hardware simulator of radio propagation channels. This Ph. D. Deals with the design and the implementation of the digital block of a hardware simulator of MIMO propagation channels, for both UMTS and WLAN networks. The hardware simulation of radio channel provides the necessary processing speed. Other advantages of the hardware simulation are the real time performance evaluation and the comparison of different systems in a time varying radio propagation channel under the same test conditions. Two approaches have been considered, one for indoor environments, the other for outdoor environments. The proposed digital architectures were studied and implemented within FPGA. Performance and complexity evaluation shows the interest of these architectures. This work was carried out under the project SIMPAA 2, with the support of the "Région Bretagne"
Ben, Slimane Jamila. "Allocation conjointe des canaux de fréquence et des créneaux de temps et routage avec QdS dans les réseaux de capteurs sans fil denses et étendus". Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0224/document.
Texto completo da fonteThe general context of the present memory is about the cross-layer optimization of wireless sensors networks based on ultra wide band technology UWB. The proposed solutions ensure the share and the efficient allocation of spectral and temporal resources, the optimization of the energy consumption and the support of multi-constraints quality of services QoS. The most challenging issue is providing a tradeoff between the resource efficiency and the multiconstrained QoS support. For this purpose, we proposed a new Wireless Hospital Sensor Network (WHSN) three-tiered architecture in order to support large-scale deployment and to improve the network performance. Then we designed a channel allocation scheme (UWBCAS,)and a prioritized multi-channel multi-time slot MAC protocol (PMCMTP) to enhance network performance and maximize the resource utilization. Finally, we proposed a joint duty cycle scheduling, resource allocation and multi-constrained QoS routing algorithm (JSAR) which simultaneously combines, a duty cycle scheduling scheme for energy saving, a resource allocation scheme for efficient use of frequency channels and time slots, and an heuristic for multi-constrained routing protocol
Badr, Maya. "Codage Espace Temps pour les canaux MIMO à accès multiple". Phd thesis, Télécom ParisTech, 2010. http://pastel.archives-ouvertes.fr/pastel-00006005.
Texto completo da fonteBadr, Maya. "Codage espace temps pour les canaux MIMO à accès multiple". Phd thesis, Paris, Télécom ParisTech, 2010. https://pastel.hal.science/pastel-00006005.
Texto completo da fonteExtensive research has been carried out these last few years on the single-user MIMO STBC design using advanced algebraic tools, namely cyclic division algebra. Families of single-user codes have been carefully constructed to achieve the DMT of the MIMO channel. Motivated by the promising results obtained in the single-user scenario, the aim of this thesis is to construct new families of multi-user STBCs. Multi-user MIMO (MU-MIMO) channels have recently attracted considerable attention because of its essential practical implication in today’s and future communication systems. The current study focuses on MIMO MAC where multiple users communicate with one receiver. A coherent communication system is considered, where the receiver has a perfect CSI while the transmitters do not have any CSI, but are aware of the channel statistics. The construction of the proposed multiple-access codes is based on an in-depth understanding of the information theoretic aspects of the MAC that give insight on the behavior of the channel. In order to simplify the problem, a MAC with single-antenna at the transmitters and an arbitrary number of antennas at the receiver is first considered in a synchronous and an asynchronous scenario. Next, the general MIMO-MAC with multiple-antenna at both the transmitters and the receiver is investigated. Finally, the multiple-access relay channel is considered, where one or more relays help the users communicate with the destination while the cooperation between the users is not allowed. In this case, we applied the code constructed for the MIMO MAC in a distributed way
Maatougui, Lamyae. "Développement d'un récepteur intelligent dédié aux systèmes sans fil basés sur les modulations M-OAM". Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0015.
Texto completo da fonteIn this work of thesis, we propose an original communication system allowing to reach high data rate and to fulfill the requirements of quality of service necessary for the communications short range dedicated to intelligent transport. This system is based on the Ultra Wide Band Impulse (IR-ULB) technology and on new modulation scheme named M-OAM (M-states Orthogonal Amplitude Modulation). M-OAM modulations are based on the principle of modulations M-QAM by replacingthe carriers used for QAM modulation with orthogonal waveforms ULB type MGF (Modified Gegenbauer Function). These modulations were evaluated under the conditions of AWGN channel and IEEE 802.15 channels which take account of the real parameters of the road. Besides the high speed required by inter-vehicular communications, it is necessary to ensure simultaneous information exchange between several users of the road. Accordingly, new adaptive multiple access system is proposed. Each user has the possibility to use the adequate modulation OAM according to the desired speed. The receiver of this system is characterized by an intelligent aspect thanks to the integration of the principle of Cognitive Radio (RC) which makes it able to detect the signal arrival and to identify the parameters of the used modulation in order to adapt the demodulation in an autonomous way. A good quality of service is ensured by the proposed novel demodulation method based on the Higher Orders Statistics (HOS) to eliminate the Gaussian noise. The good performances of M-OAM communication system M-OAM as well as the whole of the suggested aspects are validated in experiments within IEMN-DOAE laboratory. In the last part of this document we presented the realization of prototype using real time processing developed on FPGA plateform and exploiting parallelisable algorithms on reconfigurable architectures
Biaou, Ulrich. "Étude et mise en oeuvre d'une plateforme hybride basée sur du sans fil pour l'efficience énergétique et le contrôle d'accès dans le train". Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0042/document.
Texto completo da fonteThe need of new services in railway trains (services for metering, energy efficiency, the comfort and safety of users etc.) may eventually saturate the wired communication systems installed since twenty years ago years. The several advantages of wireless sensor networks (easy deployment, ability to adapt on different environments and low energy consumption) offer many possibilities for energy management systems. The aim of this thesis is to study and implement a wireless network sensors inside trains for energy efficiency. Thus, some communication protocols dedicated to energy management were presented and then a comparative study of the various wireless communication networks carried out. This comparative study shows that the ZigBee network is the most suitable for the platform. The proposed hybrid architecture allows the use of the existing IP network as the backbone of all ZigBee networks. In order to take into account the effect of the railway environment in the planning and deployment of the network, a study of the propagation channel was carried out, based on measurements realized in a subway and a RER car. The impact of the coexistence between ZigBee and WiFi and of the human presence on wireless communication have been demonstrated. The prototype of a platform based on the ZigBee network, allows data collection, informations traitement and monitoring, was carried out
Ferrand, Paul. "Communications coopératives dans les réseaux autour du corps humain". Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00941101.
Texto completo da fonteKhalili, Ramin. "Des propriétés de transmission pour la couche IP". Paris 6, 2005. http://www.theses.fr/2005PA066516.
Texto completo da fonteSoua, Ridha. "Wireless sensor networks in industrial environment : energy efficiency, delay and scalability". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00978887.
Texto completo da fonteSahraoui, Sélima. "Contribution à l'estimation des canaux relatifs aux signaux utile et interférent dans un système full-duplex dédié aux communications véhiculaires". Thesis, Valenciennes, 2019. http://www.theses.fr/2019VALE0008.
Texto completo da fonteIn this work of thesis, we propose new channel estimation approaches for a full-duplex system dédicated to vehicular communications. Both the self-interference (SI) and intended (SOI) channel are estimated. We propose different estimation méthods according to whether the pilots of the signals are transmitted jointly or separately. In the separate transmission, an estimation based on a new pilot configuration is proposed as well as a hybrid method which use both pilot configuration and training sequences.We also propose an optimisation of the conventional training-based method.It consists of improving the estimation of each training symbole. In the joint transmission, we propose two algorithms that aims to improve the estimation performances compared to the existing methods. In the first proposed method, the two channels are first estimated in the frequency domain using the Landweber iterations. The second proposition consists of using a projection matrix to manipulate only the pilots and avoid the noise that is caused by the SOI unknown datas. Finally, we propose a time and frequency-selective channel estimation for low and medium doppler frequency. Some of the proposed estimators are implemented on a real Full Duplex communication system which use Multi-reconfigurable antennas to perform the passive cancellation
Benammar, Meryem. "Gestion de l'interférence dans les réseaux à diffusion : incertitude du canal et contraintes de sécurité". Thesis, Supélec, 2014. http://www.theses.fr/2014SUPL0026/document.
Texto completo da fonteDue to the open nature of wireless communications, the transmissions on such mediums are subject to many limitations: interference (due to the increasing traffic on the network), channel uncertainty ( due to users’ mobility) and security. The most accurate information theoretic model for cellular wireless communications is the Broadcast Channel that consists of a source transmitting two distinct messages to two receivers through a channel that we model by a conditional probability distribution. Interference Management is the bottleneck of coding for such channels, as increasing the rate of a message results in an increased amount of interference at the opposite receiver. It thus consists in finding the optimal tradeoff between the two messages rates while ensuring zero decoding error probability at both receivers. When interference is coupled with channel uncertainty (channel probability distribution unknown to the source) or with simultaneous transmissions (many users interested in the same message) or even to eavesdropping, the known techniques for interference management appear to be sub-optimal. The purpose then of this thesis was to develop interference mitigation techniques for Broadcast Channels with uncertainty resorting to more involved coding strategies, for the Broadcast Channels with a helper with multiple users under many regimes of interference, and last but not least, for the Wiretap Broadcast CHannel through new outer bounding techniques
Demeslay, Clément. "Contributions pour le standard IoT LoRa : améliorations du récepteur classique et de sa sécurisation". Electronic Thesis or Diss., Brest, 2023. http://theses-scd.univ-brest.fr/2023/These-2023-MATHSTICBO-Telecommunications-DEMESLAY_Clement.pdf.
Texto completo da fonteThis thesis aims to propose enhancements for the LoRa Internet of Things (IoT) standard in order to 1) improve thedemodulation performances in the presence of multi-path channels and 2) develop security mechanisms at the physical layer to strengthen the secrecy of communications.For the first line of contribution, a study of the impact of multi-path channels is conducted and a closed-form expression of the symbol error rate is derived. Capitalizing on this study, the enhanced LoRa RAKE receiver leveraging constructively the paths energy is proposed, for the realistic scenario of channel replicashaving delays close to the main path while taking into account synchronization. For the second line of contribution, the impact of traditional Band and Tone jammers on the LoRa demodulation is investigated and highlights the sub-optimal performances of such jammers. Then, a waveform self-jamming scheme is proposed, considerably reducing demodulation capabilities of interceptors thus further enhancing the secrecy of communications. The induced Peak-to-Average Power Ratio (PAPR) by the scheme is analyzed and a mitigation technique is proposed. Finally, experiments on Software Defined Radio (SDR) equipment are achieved and demonstrate the sustainability of this self-jamming scheme
Andriés, Mihai Ionut. "Recherche de méthodes expérimentales de simulation de canaux de propagation en chambre réverbérante à brassage de modes". Phd thesis, INSA de Rennes, 2013. http://tel.archives-ouvertes.fr/tel-00825623.
Texto completo da fonteBezzina, Amira. "Interference and Resource Management in Wireless Urban Networks". Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS579.
Texto completo da fonteData traffic has been witnessing an incessant growth especially in urban wireless networks. Thus, operators need to provide high quality services with good coverage and low costs. Two interesting solutions can be considered to overcome this issue: the deployment of Multi-Radio Multi-Channel Wireless Mesh Networks or Smallcell deployment. New resource allocation and interference management schemes adapted for networks are proposed in this thesis. For MR-MC WMNs, we propose a new interference-aware game-theoretic algorithm called IGCA to manage the limited number of channels in order to alleviate the "a priori" interference between mesh routers by using a potential game. In the second part of this research work, we focus on resource allocation and power control problems in dense smallcell networks. Our ultimate goals are to alleviate the interference in downlink communications and make an efficient spectrum reuse when the urban mobile network is quite congested. The key idea is to find a trade-off between minimizing the transmit power of cells and maximizing the resource allocation with respect to an SINR threshold. To do so, we first propose a resource and power allocation algorithm called TCRPA that considers only smallcell users' demands. We formulate the optimization problem as a MILP and solve it using a cluster-based approach. Second, we extend this work to consider macro-users demands aside with the small-users ones in the defined optimization problem. We propose, TORPA, a new semi-centralized scheme, to solve the expanded MILP. Our simulation results show that our proposals succeed to meet our expectations
Soua, Ridha. "Wireless sensor networks in industrial environment : energy efficiency, delay and scalability". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066029.
Texto completo da fonteSome industrial applications require deterministic and bounded gathering delays. We focus on the joint time slots and channel assignment that minimizes the time of data collection and provides conflict-free schedules. This assignment allows nodes to sleep in any slot where they are not involved in transmissions. Hence, these schedules save the energy budjet of sensors. We calculate the minimum number of time slots needed to complete raw data convergecast for a sink equipped with multiple radio interfaces and heterogeneous nodes traffic. We also give optimal schedules that achieve the optimal bounds. We then propose MODESA, a centralized joint slots and channels assignment algorithm. We prove the optimality of MODESA in specific topologies. Through simulations, we show that MODESA is better than TMCP, a centralized subtree based scheduling algorithm. We improve MODESA with different strategies for channels allocation. In addition, we show that the use of a multi-path routing reduces the time of data collection .Nevertheless, the joint time slot and channels assignment must be able to adapt to changing traffic demands of the nodes (alarms, additional requests for temporary traffic) . We propose AMSA , an adaptive joint time slots and channel assignment based on incremental technical solution. To address the issue of scalability, we propose, WAVE, a distributed scheduling algorithm for convergecat that operates in centralized or distributed mode. We show the equivalence of schedules provided by the two modes
Smirani, Sinda. "Étude du codage réseau au niveau de la couche physique pour les canaux bidirectionnels à relais". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00962333.
Texto completo da fonteShigueta, Roni. "Channel Allocation in Mobile Wireless Networks". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX037/document.
Texto completo da fonteThe intensive use of mobile data services has increasingly increased resource consumption over wireless networks. The main resource used for wireless communication is the frequency spectrum. As data traffic rises sharply, new bands of the frequency spectrum are not available in the same proportion, making the frequency spectrum increasingly scarce and saturated. Several proposals have been presented to optimize frequency channel allocation in order to mitigate interference between nearby links that are transmitting data. Many of them use a single criterion and does not consider the user behavior to guide the channel allocation process. Users have routine cycles and social behavior. They routinary move to work, to school, use their mobile devices generating data traffic, and they meet with friends forming clusters. These characteristics can be explored to optimize the channel allocation process.This thesis presents a channel allocation strategy for wireless networks based on user behavior. Our main contribution is to consider some characteristics of the user behavior, such as mobility, traffic, and popularity in the channel allocation process. In this way, we prioritize the channel allocation for the nodes that will remain in the network in a future time window, with higher traffic in the network, and with more popularity. We adopt a distributed approach that allows limiting the number of messages exchanged in the network while quickly responding to changes in the network topology. In our performance evaluation, we consider scenarios in ad hoc and vehicular networks, and we use some synthetic mobility models, such as SLAW and Manhattan grid, and the traces dataset of Cologne city. In the scenarios, we compare our mechanism with different types of approaches: i.e., a centralized (named TABU), a random (named RANDOM), a with largest spectral distance (named LD), and a with single channel (named SC). We evaluate metrics such as aggregated throughput, packet delivery rate, and end-to-end delay. Simulations considering ad hoc scenario with unicast routing show that our strategy presents improvements in terms of throughput at the order of 14.81% than RANDOM and 16.28% than LD channel allocation. In vehicular scenario, our strategy shows gains of packet delivery rate at the order of 11.65% and 17.18% when compared to RANDOM and SC methods, respectively. In both scenarios, the performance of our strategy is close to the upper bound search of the TABU centralized approach, but with lower overhead
Bemani, Ali. "Affine Frequency Division Multiplexing (AFDM) for Wireless Communications". Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS610.pdf.
Texto completo da fonteIn the realm of next-generation wireless systems (beyond 5G/6G), the vision is clear: to support a broad range of services and applications. This includes ensuring reliable communications in environments marked by high mobility, such as high-speed railway systems and various vehicular communications. Despite the deployment of various multicarrier techniques like orthogonal frequency division multiplexing (OFDM) and single-carrier frequency division multiple access (SC-FDMA) in standardized communication systems, the challenge persists. These techniques, while effective in time-invariant frequency selective channels, face performance degradation in high mobility scenarios due to the destruction of orthogonality among subcarriers caused by significant Doppler frequency shifts. Addressing this, the search for new, robust modulation techniques is paramount. It stands as a key area of investigation aiming to resolve the reliable communications issue for next-generation wireless networks within doubly-selective wireless channels. In this thesis, a novel solution, affine frequency division multiplexing (AFDM), is proposed. This new chirp-based multicarrier waveform is based on the discrete affine Fourier transform (DAFT), a variant of the discrete Fourier transform characterized with two parameters that can be adapted to better cope with doubly dispersive channels. This thesis provides a comprehensive investigation into the principles of AFDM within high mobility communications. It provides insight into the explicit input-output relation in the DAFT domain, unveiling the consequential impact of AFDM parameters. The manuscript details the precise setting of DAFT parameters, ensuring a full delay-Doppler representation of the channel. Through analytical demonstrations, it asserts that AFDM optimally achieves the diversity order in doubly dispersive channels due to its full delay-Doppler representation. The thesis also proposes two low-complexity detection algorithms for AFDM, taking advantage of its inherent channel sparsity. The first is a low complexity MMSE detector based on LDL factorization. The second is a low complexity iterative decision feedback equalizer (DFE) based on weighted maximal ratio combining (MRC) of the channel impaired input symbols received from different paths. Additionally, the thesis presents an embedded channel estimation strategy for AFDM systems, leveraging AFDM's ability to achieve full delay-Doppler representation of the channel. In this approach, an AFDM frame contains a pilot symbol and data symbols, with zero-padded symbols employed as guard intervals to prevent interference. A practical channel estimation algorithm based on an approximate maximum likelihood (ML) approach and compatible with this pilot scheme is also provided. The thesis concludes by delving into the expanded applications of AFDM, specifically in integrated sensing and communication (ISAC) and extremely high frequency (EHF) band communications. It is demonstrated that to identify all delay and Doppler components linked with the propagation medium, one can use either the full AFDM signal or only its pilot part consisting of one DAFT domain symbol and its guard interval. Furthermore, the chirp nature of AFDM allows for unique and simple self-interference cancellation with a single pilot, eliminating the need for costly full-duplex methods. The thesis also highlights AFDM's efficient performance in high-frequency bands (with or without mobility), where the maximal spreading of its signal in time and frequency ensures a coverage gain. Unlike other waveforms, AFDM not only provides maximal time-frequency spreading but also ensures robust and efficient detection, characterized by one-tap equalization and resilience to carrier frequency offset (CFO) and phase noise
Benyamina, Djohara. "Conception des réseaux maillés sans fil à multiples-radios multiples-canaux". Thèse, 2010. http://hdl.handle.net/1866/4317.
Texto completo da fonteGenerally, network design problems consist of selecting links and vertices of a graph G so that a cost function is optimized and all constraints involving links and the vertices in G are met. A change in the criterion of optimization and/or the set of constraints leads to a new representation of a different problem. In this thesis, we consider the problem of designing infrastructure Wireless Mesh Networks (WMNs) where we show that the design of such networks becomes an optimization problem with multiple objectives instead of a standard optimization problem (a cost function is optimized) to take into account many aspects, often contradictory, but nevertheless essential in the reality. This thesis, composed of three parts, introduces new models and algorithms for designing WMNs from scratch. The first part is devoted to the simultaneous optimization of two equally important objectives: cost and network performance in terms of throughput. Three bi-objective models which differ mainly by the approach used to maximize network performance are proposed, solved and compared. The second part deals with the problem of gateways placement, given its impact on network performance and scalability. The concept of hop constraints is introduced into the network design to reduce the transmission delay. A novel algorithm based on a clustering approach is also proposed to find the strategic positions of gateways that support network scalability and increase its performance without significantly increasing the cost of installation. The final section addresses the problem of reliability in the presence of single failures. Allowing the installation of redundant components in the design phase can ensure reliable communications, but at the expense of cost and network performance. A new algorithm is developed based on the theoretical approach of "ear decomposition" to install the minimum number of additional routers to tolerate single failures. In order to solve the proposed models for real-size networks, an evolutionary algorithm (meta-heuristics), inspired from nature, is developed. Finally, the proposed models and methods have been evaluated through empirical and discrete events based simulations.
Rezgui, Jihene. "Gestion adaptative des ressources dans les réseaux maillés sans fil à multiples-radios multiples-canaux". Thèse, 2010. http://hdl.handle.net/1866/4568.
Texto completo da fonteIn the last few years, Wireless Mesh Networks (WMNs) area brought a new field of advanced research among network specialized scientists. This is due to the many advantages which WMN technology offers, such as: easy and inexpensive installation, reliable connectivity and flexible interoperability with other existing networks (Wi-Fi, WiMax, Cellular, Sensors, WPAN networks, etc.). However, several problems still remain to be solved such as the scalability, the security, the quality of service (QoS), the resources management, etc. These problems persist for WMNs, therefore the researchers propose to improve the existing protocols or to conceive new protocols for WMNs. In order to solve some of the current limitations met in the wireless networks and to improve QoS of real time multimedia applications in such networks, our research will be divided primarily into three parts: traffic admission control, traffic differentiation and handoff-aware channel assignment schemes. In the first part, we propose a distributed admission control scheme for WMNs, namely, Routing on Cliques (a clique is defined as a subset of logical links that interfere with each other) Admission Control (RCAC). Particularly, we propose an analytical model to compute the appropriate acceptance ratio and guarantee that the packet loss probability in the network does not exceed a threshold value. The model also allows computing end-to-end delay to process flow requests with delay constraints. In the second part, we design an efficient scheduler for Mesh Deterministic Access (MDA) in IEEE 802.11s-based WMNs, called Enhanced Differentiated-MDA (ED-MDA) to support voice and video applications with strict requirements on delay and on blocking/dropping probability. ED-MDA together with Enhanced Admission Control, namely EAC, reserves the minimum amount of necessary resources while maintaining an acceptable handoff call dropping and high resource utilization. The final section addresses handoff-aware channel assignment (CA) problem in Multiple Radios WMNs (MR-WMNs). In this section, we first propose a multi-objective optimization model that, besides maximizing throughput, improves fairness and handoff experience of mesh clients. In this model, the Jain’s index is used to maximize users’ fairness and to allow same channel assignments to links involved in the same high handoff traffic, thus reducing handoff-triggered re-routing characterized by its high latency. Second, we solved this model to obtain exact solutions by the CPLEX software for a limited number of nodes. We therefore propose to use centralized heuristics/meta-heuristics algorithms as an offline CA process to obtain near-optimal solutions for larger instances (real size network). Moreover, in order to adapt to traffic dynamics caused especially by user handoffs, an online CA scheme is proposed that carefully re-assigns channels to interfaces with the purpose of continuously minimizing the re-routing overhead/latency during user handoffs. This online scheme is improved using load balancing.
Bencharif, Lotfi. "Localisation en intérieur basée sur l'apprentissage automatique : exploitation des informations sur l'état des canaux Wi-Fi". Thèse, 2020. http://depot-e.uqtr.ca/id/eprint/9546/1/eprint9546.pdf.
Texto completo da fonteRolim, Fernandes Carlos Estêvao. "Méthodes statistiques d'ordre élevé pour l'identification aveugle de canaux et la détection de sources avec des applications aux systèmes de communicaton sans fil". Phd thesis, 2008. http://tel.archives-ouvertes.fr/tel-00460158.
Texto completo da fonteMenhaj, Lamyae. "Développement d'un récepteur intelligent dédié aux systèmes sans fil basés sur les modulations M-OAM". Thesis, 2017. http://www.theses.fr/2017VALE0015/document.
Texto completo da fonteIn this work of thesis, we propose an original communication system allowing to reach high data rate and to fulfill the requirements of quality of service necessary for the communications short range dedicated to intelligent transport. This system is based on the Ultra Wide Band Impulse (IR-ULB) technology and on new modulation scheme named M-OAM (M-states Orthogonal Amplitude Modulation). M-OAM modulations are based on the principle of modulations M-QAM by replacingthe carriers used for QAM modulation with orthogonal waveforms ULB type MGF (Modified Gegenbauer Function). These modulations were evaluated under the conditions of AWGN channel and IEEE 802.15 channels which take account of the real parameters of the road. Besides the high speed required by inter-vehicular communications, it is necessary to ensure simultaneous information exchange between several users of the road. Accordingly, new adaptive multiple access system is proposed. Each user has the possibility to use the adequate modulation OAM according to the desired speed. The receiver of this system is characterized by an intelligent aspect thanks to the integration of the principle of Cognitive Radio (RC) which makes it able to detect the signal arrival and to identify the parameters of the used modulation in order to adapt the demodulation in an autonomous way. A good quality of service is ensured by the proposed novel demodulation method based on the Higher Orders Statistics (HOS) to eliminate the Gaussian noise. The good performances of M-OAM communication system M-OAM as well as the whole of the suggested aspects are validated in experiments within IEMN-DOAE laboratory. In the last part of this document we presented the realization of prototype using real time processing developed on FPGA plateform and exploiting parallelisable algorithms on reconfigurable architectures