Worldwide Interoperability for Microwave Access (WiMAX) is one of the next generation broadband wireless access technologies. The WiMAX features longer transmission distance and more accomplished support of Quality of Service (QoS) than other wireless access technologies such as IEEE 802.11. Specifically, QoS has become an important role in the context of a variety of applications which utilize network resources. Radio Resource Management (RRM) always plays important role in providing the QoS guarantees. In WiMAX, Medium Access Control (MAC) protocol defines a wide variety of mechanisms for bandwidth allocation and QoS provision. Although different types of QoS classes have been defined by WiMAX, the scheduling architecture is left to be vendor specific.