The Research And Optimized Design For QoS Mechanism Based On IEEE 802.16 In WMAN

October,2007, the United Nations International Telecommunication Union (ITU) formally approved the WiMAX wireless broadband access technology to become the global standard for mobile devices and WiMAX became the world's fourth largest 3G standards after WCDMA, CDMA2000 and TD-SCDMA in the name of OFDMA TDD WiMAX. With the second-generation mobile WiMAX-IEEE 802.16m speeding up the certification process, standards-setting organization IEEE expects to formally complete standards setting in mid-2010, when, IEEE 802.16m will become the world's first meeting the definition of 4G technology standard ITU defined.At the same time, the crucial technology of WiMAX-Quality of Service(QoS) has drawn more and more attentions, and has become the hotspot of WiMAX technology study. IEEE 802.16, the specification for fixed, nomadic, portable and mobile BWA systems, is promising to support heterogeneous classes of traffic with differentiated QoS. The proposed Medium Access Control (MAC) protocol defines four types of service flows, the mechanism for message exchange between BS and SS (such as the connection set-up, BW-request and UL-MAP message) and the uplink scheduling for UGS service flow. The MAC has also proposed a QoS architecture. However, the details of scheduling algorithms for rtPS, nrtPS, BE service flow and the admission control process are left unspecified.Based on the above, this paper proposed an enhanced QoS architecture, which is based on the existing QoS architecture of IEEE 802.16 MAC-layer and the buffer module, traffic policing module, adaptive modulation code (AMC) module added; Our simulation results depict the enhanced QoS in terms of end-to-end delay with dynamic redistribution of bandwidth. Effective scheduling algorithms were considered and from the results we can infer that, the considered hybrid-scheduling algorithms provides less end-to-end delay for real time services. This concludes the provision of allotting more SSs under a single BS, maintaining the end-to-end delay within the permissible range, and found that GPSS gives the better end-to-end delay; As the detail of the admission control process is unspecified, this paper defined a dynamic bandwidth allocation admission control process based on priority, and compared it with the conventional fixed bandwidth allocation admission control process. The result shows that the proposed admission control mechanism is more performance and efficient.In addition, for the VoIP service which is become more and more popular, this paper proposed a traffic aware scheduling algorithm for VoIP applications in WiMAX networks. We study the performance of our proposed method and compare it with that of some conventional methods. The tradeoff between delay and bandwidth efficiency is discussed, and it is shown that using our scheduling method using our proposed scheduling method can lead to a better delay, support more VoIP subscribers and bandwidth efficiency.Lastly, to solve the interworking problem of WiMAX and IMS, work in this paper has fulfilled the extension of UMTS Bearer Service to WiMAX access by establishing an end-to-end QoS frame. The frame puts forward the method of signaling negotiation and mapping for WiMAX QoS and IMS QoS, successfully solves the problem of interworking of different QoS mechanism over segmented bearer services, and therefore achieves the unified QoS guarantee throughout the whole WiMAX-IMS network for complex multimedia services with per-user differentiation and low jitters, which other traditional frame can not provide.