Abstract

In this thesis, the problem of resource allocation in IS-856 is studied. The problem is first formulated in an interference model framework on reverse channel (uplink). A simple controller is then designed for the system and the closed-loop stability is analyzed using the Lyapunov technique. The possible oscillation in the network output caused by the limit cycles associated with the nonlinear elements in the control loop is analyzed in the framework of describing functions. A dynamic control strategy is developed subsequently for efficient rate assignment in the network. This is carried out in two steps: in the first step, the controller is designed for a simple case when the number of users in the network is fixed and known, and all users are full-buffered. The asymptotic stability property of the proposed controller is verified. Then, the designed controller is further developed for a dynamic network, where the number of active users is subject to change but is known to the users by means of the communication link between the base station and users. In this step, the activation/deactivation of users at different time instants is formulated as a switched system, and sufficient conditions on the speed of activation and deactivation of users are obtained in the control theoretic framework to achieve stability and the desired performance. In the next step, the obtained controller is adjusted properly for the case when the information about the number of active users is not communicated to the users (in order to allocate more bandwidth for data transmission). A controller is also designed to guarantee network stability and performance in the presence of time-delay in the feedback loop. Finally, the long-term fairness in rate allocation is studied. Simulation results are also provided throughout the thesis to elucidate the effectiveness of the proposed approach.