Research On The Scheduling Mechanism In WiMAX Systems

WiMAX (Worldwide Interoperability for Microwave Access) is an IEEE 802.16-2004 standards-based broadband wireless technology, aiming at the unification of air interface for the fixed wireless access. IEEE 802.16d provides quality of service and high transfer rate. With the development of networks, more and more multimedia applications with different quality of service have been developed. In order to ensure various quality of service, IEEE 802.16d media access control layer defines four kinds of service types according to different application requirements. These four service types are UGS, rtPS, nrtPS and BE. How to allocate the radio resources according to the four different types of service to achieve the full use of wireless resource and to guarantee the quality of service is the important content of the research.There are two kinds of networks for WiMAX systems, the PMP network and the Mesh network. In this paper, two kinds of scheduling mechanisms in different networks are described. In the PMP network, a QoS model is established with a probabilistic method. A momentum scheduling algorithm is presented to guarantee QoS requirements. To guarantee the real-time services'maximum delay requirement, the new algorithm sets a waiting time priority. A channel gain relative priority is also set to improve the throughput of the WiMAX system. In the Mesh network, the paper presents a combination of centralized and distributed scheduling mechanism. The paper presents an optimal boundary in the chain topology at the principle of minimum signaling overhead. The paper also presents the optimal stratification point of a circular coverage area.After simulating and analyzing the designed two kinds of scheduling mechanisms, the results show that, the PMP scheduling mechanism can satisfy the QoS requirements of high priority service types, and the low priority service types have opportunity to transmit packets. The Mesh scheduling mechanism decreases the loads needed by scheduling and save the wireless resource. The mechanism improves the efficiency of the transfer of effective resources. These two mechanisms provide some application value for WiMAX products.