On quality of service in mobile wireless networks

This paper addresses the choices that need to be made in the design of a quality of service (QoS) framework for mobile and wireless networks. An uncontrollably time varying environment, arising due to physical processes such as fading as well as systematic processes such as handoffs, is an inalienable characteristic of these networks. Therefore, the laissez faire model of purely reactive applications adapting to a black-box network does not work well for multimedia applications in the presence of wireless and mobility. However, as we empirically show, the other extreme of applying rigid quality of service models borrowed from the wired networks, with correspondingly complex network mechanisms, is also a bad idea because of the often adverse interaction between higher layer protocols with mechanisms such as rerouting and MAC control. We advocate that mobile network and wireless link layer mechanisms should be kept simple and stupid, though not oblivious of QoS, and that applications should be made more sophisticated with QoS renegotiation and adaptation capabilities. The paper describes the necessary support required in various layers of mobile wireless networks, and advocates specific solutions based on empirical validations.