Admission Control (AC) algorithms in mobile cellular networks support continuity of active communication sessions by guaranteeing availability of free resources. In this paper, we first describe the factors that condition AC design and show that AC in broadband mobile networks presents new challenges compared to AC in telephone cellular networks. We tailor the guard channel admission control strategy to the characteristics of mobile WiMAX networks. For AC validation and performance evaluation we use OPNET Modeler WiMAX Suite. To this end, we create in the simulator a framework for AC implementation. Then, we incorporate the Guard Capacity (GC) algorithm, which is the preferred choice of telephone cellular networks’ operators as GC is simple yet efficient. The accuracy of implementation is validated through simulation.