<p>In order to be competitive with emerging mobile systems and to satisfy the ever growing request for higher data rates, the 3G consortium, 3rd Generation Partnership Project (3GPP), is currently developing concepts for a long term evolution (LTE) of the 3G standard. The LTE-concept at Ericsson is based on Orthogonal Frequency Division Multiplexing (OFDM) as downlink air interface. OFDM enables the use of frequency domain link adaptation to select the most appropriate transmission parameters according to current channel conditions, in order to maximize the throughput and maintain the delay at a desired level. The purpose of this thesis work is to study, implement and evaluate different link adaptation algorithms. The main focus is on modulation adaptation, where the differences in performance between time domain and frequency domain adaptation are investigated. The simulations made in this thesis are made with a simulator developed at Ericsson. Simulations show in general that the cell throughput is enhanced by an average of 3% when using frequency domain modulation adaptation. When using the implemented frequency domain power allocation algorithm, a gain of 23-36% in average is seen in the users 5th percentile throughput. It should be noted that the simulations use a realistic web traffic model, which makes the channel quality estimation (CQE) difficult. The CQE has great impact on the performance of frequency domain adaptation. Throughput improvements are expected when using an improved CQE or interference avoidance schemes. The gains with frequency domain adaptation shown in this thesis work may be too small to motivate the extra signalling overhead required. The complexity of the implemented frequency domain power allocation algorithm is also very high compared to the performance enhancement seen.</p>

In order to be competitive with emerging mobile systems and to satisfy the ever growing request for higher data rates, the 3G consortium, 3rd Generation Partnership Project (3GPP), is currently developing concepts for a long term evolution (LTE) of the 3G standard. The LTE-concept at Ericsson is based on Orthogonal Frequency Division Multiplexing (OFDM) as downlink air interface. OFDM enables the use of frequency domain link adaptation to select the most appropriate transmission parameters according to current channel conditions, in order to maximize the throughput and maintain the delay at a desired level. The purpose of this thesis work is to study, implement and evaluate different link adaptation algorithms. The main focus is on modulation adaptation, where the differences in performance between time domain and frequency domain adaptation are investigated. The simulations made in this thesis are made with a simulator developed at Ericsson. Simulations show in general that the cell throughput is enhanced by an average of 3% when using frequency domain modulation adaptation. When using the implemented frequency domain power allocation algorithm, a gain of 23-36% in average is seen in the users 5th percentile throughput. It should be noted that the simulations use a realistic web traffic model, which makes the channel quality estimation (CQE) difficult. The CQE has great impact on the performance of frequency domain adaptation. Throughput improvements are expected when using an improved CQE or interference avoidance schemes. The gains with frequency domain adaptation shown in this thesis work may be too small to motivate the extra signalling overhead required. The complexity of the implemented frequency domain power allocation algorithm is also very high compared to the performance enhancement seen.

La préservation de l’environnement et des ressources naturelles pour les prochaines générations est aujourd’hui considérée comme un des axes les plus prioritaires dans presque tous les secteurs économiques. Le secteur des Technologies de l’Information et de la Communication est loin d’être épargné de cette tendance écologique. Nous considérons dans cette thèse la problématique de la conservation d’énergie dans le contexte technologique actuel caractérisé par: • La coexistence d’une multitude de technologies d’accès sans fil offrant un environnement riche et dynamique • Des terminaux mobiles multimodaux • Limitations persistantes des sources d’énergie sur les terminaux mobiles. Dans ce contexte très riche, les possibilités offertes aux usagers sont à double tranchant. D’un côté, elles peuvent très bien améliorer la QoS en offrant toujours la meilleure connectivité en fonction du contexte de l’utilisateur. D’un autre côté, et sans une bonne optimisation de la consommation d’énergie sur le terminal, la disponibilité de celui-ci peut vite diminuer et donc faire baisser la QoE à cause de l’énergie nécessaire pour gérer plusieurs interfaces radio en parallèle. Nous considérons essentiellement les liens entre les stations de base (ou les point d’accès) et les terminaux mobiles. Notre objectif étant d’analyser la consommation d’énergie sur ces liens pour ensuite proposer des contributions permettant de mieux la maitriser. Nous focalisons essentiellement sur l’exploitation des multiples interfaces et du multi-flux pour étudier, analyser et proposer des solutions dynamiques et adaptatives d’ordonnancement, de sélection et de gestion d’interfaces minimisant la consommation d’énergie / Since the last decades, environmental issues are becoming among the major concerns for most human activities, including the Information and Communication Technologies sector. This will surely influence upcoming networking technologies, architectures and usage practices. New approaches and methodologies are required in order to evaluate and to reduce the Carbon Footprint toward what is commonly denoted as Green Networks. Within the ICT sector, the main efforts are related to energy saving techniques. These efforts started in early stages within wireless technologies, mainly because of energy limitations on mobile devices such as mobile phones and wireless sensors. Additionally, because of health considerations, standardization bodies and government had set stringent policies and limits on electromagnetic radiation levels that can be emitted by radio stations. For these reasons, many academic and industrial research and development activities had led to a number of relatively energy efficient solutions. In this thesis, we consider energy efficiency in the context of Heterogeneous Wireless Access Networks. These are composed of multi-standards wireless network solutions, with non uniform topologies and cell sizes and Multi-Modal mobile terminals able to manage simultaneously different connections. The main contributions of our studies include the proposal of new optimization solutions regarding user association and scheduling techniques at both flow and packet levels for multi-homed mobile terminals. An overall context-based solution is also proposed in order to provide end-to-end energy efficient networking solutions