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    一种面向公平保证QoS的WiMAX二级调度方案

    A Fair-Oriented Two-Level Scheduling Scheme for QoS Guarantee in WiMAX

    • 摘要: IEEE 802.16作为全球微波接入互操作系统技术标准,虽然定义了5类信流(分别是UGS,rtPS,ertPS,nrtPS和BE),并将服务质量支持机制引入媒体接入控制层,却没有规定相应的调度算法.为有效保证各种多媒体通信的服务质量,提出了一种基于正交频分多址接入技术和自适应调制编码机制的二级调度方案.该调度方案采用跨层设计思想,适用于PMP WiMAX网络下行链路中.一级调度器按照QoS优先级顺序调度位于不同类型缓存器的队头分组,从而满足rtPS业务的最大时延限定和nrtPS业务的最小速率要求;完成一级调度后,为满足用户速率公平性,二级调度器根据自适应调制编码信息及用户状态信息调度位于不同用户缓存器的队头分组.仿真结果表明该方案能够有效保证各种多媒体通信服务满足QoS要求并兼顾用户速率公平,同时也可获得较高的WiMAX系统吞吐量.

       

      Abstract: As the standard of worldwide interoperability for microwave access (WiMAX) technology, IEEE 802.16 defined five classes of traffic services, which are UGS, rtPS, ertPS, nrtPS, and BE, respectively, and introduced a supporting mechanism for quality of services (QoS) into medium access control (MAC) layer. But it did not propose the corresponding scheduling algorithm. In order to provide various multimedia communications with QoS guarantee effectively, a two-level scheduling scheme is proposed based on the orthogonal frequency division multiple access (OFDMA) technology and adaptive modulation and coding (AMC) mechanism. This scheduling scheme employes the cross-layer design methodology and can be used in the point-to-multipoint (PMP) WiMAX downlink. According to the value of QoS priority, the first-level scheduler schedules the head of line (HOL) packets in different service class buffers to satisfy the rtPS maximum delay restriction and nrtPS minimum rate requirement simultaneously. After accomplishing the first-level scheduling, the second-level scheduler schedules the HOL packets in different user buffers according to the AMC information and users’ state message for obtaining the users’ rate fairness. Simulation results show that the proposed two-level scheme can meet various QoS requirements of multimedia services well without sacrificing users’ rate fairness, and meanwhile, get the preferable WiMAX system throughput.

       

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