Ensuring Quality of Service (QoS) in wireless networks poses an open problem in many application domains. We propose an automatic on-line QoS monitoring and management infrastructure that can be incorporated into existing network setups. Based on model-based assessment of current and future QoS conditions, our solution will control traffic in the network through a combination of admission control, enforced handover, traffic shaping and transmission parameter adjustments. Correctness of the model is evaluated through experimental evaluation and simulations. We implement a prototype of the proposed system using open-source components.