Enabling an acceptable QoS provision for realtime services is constrained by the lack of radio resources availability and the load network. To overcome this issue, an efficient admission control must be applied to provide user's QoS expectation while respecting the resource availability constraint. We propose in this paper different admission control strategies aiming at simultaneously improving the efficiency utilization of network resources and guaranteeing QoS for the admitted users. Numerical results show the robustness of our proposed schemes in enhancing the mean of served VoIP users while maintaining an average VoIP packet delay less than 3 ms.