This paper addresses the issue of wireless resource allocation of a Mobile WiMAX cell based on OFDMA access technique. We compare two strategies: the MAX SNR which is the most used channel assignment technique and our proposal which is based on channel condition learning. As we distinguish four IEEE 802.16e-2005 service classes: UGS, rtPS, nrtPS and ErtPS, we combine these strategies with a scheduler block in order to satisfy the QoS constraints of these classes. In addition, we take into consideration the Adaptive Modulation and Coding (AMC) scheme, through the selection of the slot which is based on the modulation scheme. The main concern here is to propose a simple method to assign WiMAX physical resources called slot to satisfy QoS constraints of a user's scheduled MPDUs, which can be easily and efficiently used in a realistic Mobile WiMAX network.