Technique d'accès pour la communication machine-à-machine dans LTE/LTE-A

Machine type communications is seen as a form of data communication, among devices and/or from devices to a set of servers, that do not necessarily require human interaction. However, it is challenging to accommodate MTC in LTE as a result of its specific characteristics and requirements. The aim of this thesis is to propose mechanisms and optimize the access layer techniques for MTC in LTE. For uplink access, we propose two methods to improve the performance of random access in terms of latency: a packet aggregation method and a Transmission Time Interval bundling scheme. To further reduce the uplink latency and enable massive number of connected device, we propose a new contention based access method (CBA) to bypass both the redundant signaling in the random access procedure and also the latency of regular scheduling. For downlink reception, we propose two methods to analyze the performance of discontinuous reception DRX mode for MTC applications: the first with the Poisson distribution and the second with the Pareto distribution for sporadic traffic. With the proposed models, the power saving factor and wake up latency can be accurately estimated for a given choice of DRX parameters, thus allowing to select the ones presenting the optimal tradeoff.Les communications de type machine-à-machine M2M sont considérées comme des formes de communication de données qui ne requièrent pas nécessairement d'interaction humaine. Cependant, ce type de communication n'est pas efficace dans les réseaux cellulaires, en raison de leurs caractéristiques spécifiques, telles que. L'objectif de cette thèse est de proposer des mécanismes et d'optimiser les techniques de la couche d'accès radio LTE pour les communications M2M. Pour l'accès au canal de liaison montante, nous proposons deux méthodes afin d'améliorer la performance d'accès aléatoire en terme de latence et de consommation énergétique: une méthode d'agrégation de paquets et une autre de transmission multiple pendant l'intervalle de temps de transmission. Afin de réduire encore plus le temps de latence de liaison montante et permettre une connexion d'un grand nombre de machines au réseau, nous proposons une nouvelle méthode d'accès basée sur la contention CBA pour éviter d'une part la signalisation redondante pour accéder au canal et d'autre part la latence de l'ordonnanceur. Pour la réception de liaison descendante, nous proposons deux méthodes pour analyser les performances du mécanisme de réception discontinu DRX pour les applications M2M: la première se base sur une distribution de Poisson, la suivante sur une distribution Pareto pour le trafic sporadique. Avec les modèles proposés, le facteur d'économie d’énergie et la latence pour transiter du mode sommeil au mode actif peuvent être estimés avec précision pour un choix donné de paramètres DRX, permettant ainsi de sélectionner ceux permettant d'atteindre le compromis optimal

Spectrum Sharing Methods in Coexisting Wireless Networks

Radio spectrum, the fundamental basis for wireless communication, is a finite resource. The development of the expanding range of radio based devices and services in recent years makes the spectrum scarce and hence more costly under the paradigm of extensive regulation for licensing. However, with mature technologies and with their continuous improvements it becomes apparent that tight licensing might no longer be required for all wireless services. This is from where the concept of utilizing the unlicensed bands for wireless communication originates. As a promising step to reduce the substantial cost for radio spectrum, different wireless technology based networks are being deployed to operate in the same spectrum bands, particularly in the unlicensed bands, resulting in coexistence. However, uncoordinated coexistence often leads to cases where collocated wireless systems experience heavy mutual interference. Hence, the development of spectrum sharing rules to mitigate the interference among wireless systems is a significant challenge considering the uncoordinated, heterogeneous systems. The requirement of spectrum sharing rules is tremendously increasing on the one hand to fulfill the current and future demand for wireless communication by the users, and on the other hand, to utilize the spectrum efficiently. In this thesis, contributions are provided towards dynamic and cognitive spectrum sharing with focus on the medium access control (MAC) layer, for uncoordinated scenarios of homogeneous and heterogeneous wireless networks, in a micro scale level, highlighting the QoS support for the applications. This thesis proposes a generic and novel spectrum sharing method based on a hypothesis: The regular channel occupation by one system can support other systems to predict the spectrum opportunities reliably. These opportunities then can be utilized efficiently, resulting in a fair spectrum sharing as well as an improving aggregated performance compared to the case without having special treatment. The developed method, denoted as Regular Channel Access (RCA), is modeled for systems specified by the wireless local resp. metropolitan area network standards IEEE 802.11 resp. 802.16. In the modeling, both systems are explored according to their respective centrally controlled channel access mechanisms and the adapted models are evaluated through simulation and results analysis. The conceptual model of spectrum sharing based on the distributed channel access mechanism of the IEEE 802.11 system is provided as well. To make the RCA method adaptive, the following enabling techniques are developed and integrated in the design: a RSS-based (Received Signal Strength based) detection method for measuring the channel occupation, a pattern recognition based algorithm for system identification, statistical knowledge based estimation for traffic demand estimation and an inference engine for reconfiguration of resource allocation as a response to traffic dynamics. The advantage of the RCA method is demonstrated, in which each competing collocated system is configured to have a resource allocation based on the estimated traffic demand of the systems. The simulation and the analysis of the results show a significant improvement in aggregated throughput, mean delay and packet loss ratio, compared to the case where legacy wireless systems coexists. The results from adaptive RCA show its resilience characteristics in case of dynamic traffic. The maximum achievable throughput between collocated IEEE 802.11 systems applying RCA is provided by means of mathematical calculation. The results of this thesis provide the basis for the development of resource allocation methods for future wireless networks particularly emphasized to operate in current unlicensed bands and in future models of the Open Spectrum Alliance