Analysis Of QoS Mechanisms In IEEE 802.16 Systems

IEEE 802.16 broadband Wireless Metropolitan Area Network (WMAN) technology grows unceasingly. It contributes a lot to the development of wireless access technology and the wireless market. The WiMAX Forum is for the purpose of guaranteeing the compatibility and the interoperability of different products based on IEEE 802.16 standards. Its impact is increasing in the field of Broadband Wireless Access (BWA). Today WiMAX has become the synonym of IEEE 802.16. 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, 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.To solve the problems mentioned above, this paper proposed an enhanced QoS architecture, which is based on the existing QoS architecture and the buffer module, traffic policing module, adaptive modulation code (AMC) module added; In addition, this paper designed the uplink packet scheduling (UPS) and divided it into three modules: information module, scheduling database module and service assignment module. It proposed a scheduling service discipline based on strict priority and the scheduling algorithms for rtPS, nrtPS and BE services respectively. It also evaluated the performance of the proposed mechanism in providing QoS support to real time application by simulation; 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 efficient.In addition, for the VoIP service which is become more and more popular, this paper proposed an enhanced uplink scheduling algorithm for VoIP services in IEEE 802.16 systems, which is based on voice activity detecting: the BS assigns uplink resources to the SSs considering voice state transitions of the SSs. This algorithm can solve the problems caused by the conventional algorithms, such as waste of uplink resource, MAC overhead and additional access delay. The analysis and simulation results showed that this enhanced algorithm had better performance in view of throughput and system capacity.Lastly, to solve the interworking problem of IEEE 802.11e and IEEE 802.16 standards, this paper proposed a QoS architecture by designing a radio gateway (RG) module to guarantee the end-to-end QoS in an interworking system of IEEE 802.11e and IEEE 802.16 standards. Besides, it also proposed two different QoS mapping mechanisms based on this architecture: prioritized mapping and parameterized mapping.