One of the most interesting applications of single–sided Quality of Experience (QoE) metrics is their use in improving the quality of the service, as perceived by the user. This can be done either at the application level – by for example changing the encoding in use, or the level of error correction applied – or at the network level, for instance by choosing a different DiffServ marking strategy, or changing the access network in use. To this end, the QoE metric used needs to be fast and accurate, and the context in which the application will be used needs to provide the opportunity for performing some sort of control operation. In this paper we describe the application of QoE estimations for VoIP to improve existing network–level mobility management solutions.