Admission control is a fundamental mechanism used for Quality of Service (QoS) provisioning by restricting the access to the network resources. In this paper, we consider the application of superposition coding to increase the system capacity through multiuser diversity exploitation. We propose a joint great fairness admission control and superposition coding scheme to provide a good tradeoff between the QoS level perceived by the user in the system and the utilization of the scarce radio resources. Numerical results show the robustness of our proposed scheme in enhancing the system performance by allowing the decrease of the VoIP packet dropping ratio up without an excessive loss of the BE user's throughput.