Mention ”Informatique”

The scarce resources in wireless systems compounded with their highly variable and errorprone propagation characteristics stress the need for efficient resource management. Scheduling is a key tool to allocate efficiently the radio resource. While fading effects have long been combated in wireless networks, primarily devoted to voice calls, they are now seen as an opportunity to increase the capacity of novel wireless networks that incorporate data traffic. For data applications, there is a service flexibility afforded by the delay tolerance of elastic traffic and by their ability to adapt their rate to the variable channel quality. Opportunistic scheduling exploit these characteristics by making use of channel state information to ensure that transmission occurs when radio conditions are most favourable. When user applications have heterogeneous characteristics and quality of service requirements, opportunistic scheduling becomes a challenging task. In this thesis, opportunistic scheduling transmission schemes for supporting downlink non-real time services are proposed and analyzed for novel cellular and wireless broadband systems. The proposed schemes are designed for covering various QoS requirements for users while increasing the system utilization. We investigated the two main approaches adopted in the literature to devise efficient channel-aware policies for elastic traffic: Wireless Fair Queueing and Proportional Fair Scheduling: • Wireless fair queueing makes use of channel state information to avoid allocating resources to users that cannot emit as they are in rather bad channel state while striving to fulfil fairness properties as defined by the GPS model. Existing wireless fair queueing algorithms use information relative to the channel state in a rather simplistic way. A given user is in a binary state: in a good channel state and can consequently exchange data; or in a bad channel state and cannot therefore exchange data. Opportunistic scheduling goes a step further and makes use of channel state information to give priority to users experiencing relatively better channel quality and thus increases system efficiency. In our work, we propose a new opportunistic wireless fair queueing scheduler for 802.16 systems. Our scheduler notably enhances the overall system performance through opportunistic scheduling as compared to existing approaches while fulfilling users’ QoS needs in terms of minimum xix