The Research, Design And Implementation Of Mac-layer Scheduling Algorithm In Wimax System

As a kind of wireless metropolitan area network technology, WiMAX has gotten the nod of many vendors, experts and scholars at home and abroad. Meanwhile it has become hot spots in the current field of communication. WiMAX has a lot of advantages, such as extensive coverage, long transmission distance, quick transmission rate, multi-service support capabilities and efficient networking mode supported. It is based on IEEE 802.16 family of standards, which defines its PHY layer and MAC layer specifications. The physical layer, which using OFDM technology for data transmission in the wireless environment, provides a reliable guarantee. According to different attributes of the business, the MAC layer defines four kinds of service types: UGS, rtPS, nrtPS and BE services. At the same time, the standard for the MAC layer provides connection-oriented delivery mechanisms and improves the business flow management mechanisms to guarantee the QoS needs of each business. However, the standard does not give a specific scheduling algorithm. In the condition of high-speed, multi-service and bandwidth limited, how to conduct of resource scheduling effectively requires further research on WiMAX technology.This paper mainly studies on scheduling algorithm for QoS assurance mechanism.First, a brief introduction of the WiMAX technology-related is given.Then, the detailed analysis about IEEE 802.16d protocol is conducted. Especially, the agreement that has been well-defined QoS assurance mechanism is in-depth research. Between these, the bandwidth request\distribution process is mainly analyzed.Subsequently, by analyzing the characteristics of existing scheduling algorithms and taking into account the characteristics of services in WiMAX, scheduling solution is established. In contrast to the existing scheduling structure, the classification strategy based on improved DFPQ scheduling algorithm is proposed. After that, the hierarchical scheduler at all levels is spelled out.In the last part of this article, WiMAX system simulation platform with the GloMoSim network simulation environment is built. Using the platform, the traditional and improved scheduling strategies are simulated. Compared with the traditional hierarchical scheduling strategy, the improved strategy reduces the average delay of real-time business and improves the throughput of real-time business in the assurance of total throughput. The simulation results show that the modified scheduling strategy meets the QOS requirements of various services and it is superior to the traditional hierarchical scheduling policy.