Best-effort resource sharing by users with QoS requirements

Communication networks typically provide a basic best-effort service category, in which resources are shared by concurrent users. As no QoS guarantees are provided, a user will submit to best-effort service only if the expected QoS meets some minimal, user-specific, requirements. This results in an inherent conflict of interest among users, which we capture through a dynamic noncooperative game model and investigate its structure and properties. Specifically, we study the operating points of such systems, i.e., their Nash equilibria. First, we investigate the optimal user strategies, which involve a prediction of the evolving system state, and show that they are of the threshold type. We then establish that a Nash equilibrium point exists and is unique. An algorithmic scheme for computing the Nash equilibrium is provided. In practice, rather than making complex predictions, users typically employ simple decision rules, based on what they learn by experience. Interestingly, it can be shown that the Nash equilibrium of the considered system is a stationary point of such learning schemes. Moreover, we demonstrate that the decisions of users which employ such schemes converge to the Nash equilibrium. Finally, we discuss the implications of the study on network design and management.