The need to support ubiquitous connectivity with higher data rate for mobile computers and communication devices are fuelling a growing interest in broadband wireless access (BWA) networks. WiMAX(Worldwide Interoperability for Microwave Access ), a technology based on IEEE 802.16 is a standard for Wireless Metropolitan Area Networks (Wireless MAN) which aims to provide broadband access in the "last mile" with QoS (Quality of Service) guarantees for heterogeneous class of services with different QoS requirements. The QoS requirements are given in terms of bandwidth, latency, jitter,...