We propose a frequency planning based on zone switching diversity scheme for multicell OFDMA mobile WiMAX networks. In our approach, we focus on the use of Fractional Frequency Reuse (FFR) for guaranteeing the quality of service for the different service flows in the system. We investigate an architecture that coordinates the allocation of resources in terms of slots (the basic allocation unit in time and frequency domain in an OFDMA frame) between the Radio Resource Controller (RRC) and the Radio Resource Agent (RRA) which resides in the Base Station (BS). The proposed algorithm attempts to capture three types of diversity, namely, mutual interference diversity, traffic diversity, and selective fading channel diversity. As a consequence, the proposed algorithm for slot allocation makes a trade-off between maximizing overall throughput of the system while guaranteeing the Quality of Service (QoS) requirements for a mixture of real-time and non-real-time service flows under different diversity configurations. Our algorithm is evaluated under various cell configurations and traffic models. The results reveal important insights on the trade-off between cell interference suppression and QoS assurance