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The IEEE 802.16 standard, which includes specification for the medium access control (MAC) and physical (PHY) layers, was designed to handle the requirements of different contemporary applications with diverse QoS requirements. IEEE 802.16 standard is equipped with signaling and bandwidth allocation algorithms that can accommodate many connections with a variety of QoS requirements at one subscriber station (SS). The connections may be varied in their bandwidth and latency requirements, so several researchers proposed an IEEE 802.16 schedulers with different objectives to provide for wireless resource allocations over a different range of traffic models. In this paper, we conduct a comprehensive performance study of scheduling algorithms in Point to multipoint mode of WiMAX. We first make a classification of WiMAX scheduling algorithms, then simulate a representative number of algorithms in each class taking into account the characteristics of the IEEE 802.16 standard. We evaluate the algorithms with respect to their abilities to support multiple classes of service, providing quality of service (QoS) guarantees, fairness amongst service classes and bandwidth utilization. To the best of our knowledge, no such comprehensive performance study has been reported in the literature. Simulation results indicate that none of the current algorithms is capable of effectively supporting all WiMAX classes of service. We demonstrate that an efficient, fair and robust scheduler for WiMAX is still an open research area. We conclude our study by making recommendations that can be used by WiMax protocol designers.