Renegotiable quality of service-a new scheme for fault tolerance in wireless networks In this paper we propose the concept that faults in telecommunications networks often manifest themselves as reductions in service quality, which can be addressed by using the notion of Quality of Service (QoS). In wireless ATM networks, the ability to provide QoS guarantees for high priority traffic in the presence of noise or faults is of utmost importance. Moreover there is a need for renegotiating existing QoS on an established connection, since the characteristics of a wireless link may well change during the lifetime of a connection due to mobile hosts’ movements or external interference. In this paper we describe a general QoS strategy as a fault tolerance mechanism, and address the problems associated with providing QoS over a wireless link. We present a QoS scheme with renegotiation capability, define an API (application programming interface) for the access to this scheme and describe our implementation for this QoS API on the SWAN system, a wireless ATM network, and summarize its performance using measurements obtained from a series of experiments based on different fault scenarios.