無線區域網路服務品質保證 之高效能佇列回報機制

Abstract

HCF控制型通道存取定義在IEEE802.11e文件中，它提出了一個Sample Scheduler，它提供了配置TXOP到QoS-aware工作站。因此TXOP的計算是根據平均資料率，而它也只適用CBR的資料流。對於VBR的資料流，他們可能會超過延遲限制。先前的工作都建議在封包傳輸前，透過回報佇列的狀態到排程器，每一個QSTA可以根據他們緩衝封包的時限去配置傳輸機會。為了滿足所有請求的延遲限制，適當的佇列回報會引起相當多的不必要的動作，導致通道的使用變差。在這篇論文中，我們採用多輪詢的技術、earliest deadline first機制和提供一個高效能的佇列回報方案去提供服務品質的支援。模擬的結果顯示我們提出的方法和先前的工作比較起來，不僅僅達到服務品質的需求，而且也能更有效的管理頻寬。

HCF Controlled Channel Access (HCCA), defind in the IEEE 802.11e document, proposes a sample scheduler to allocate transmission opportunity (TXOP) to QoS-aware stations (QSTAs). Since the calculation of TXOP duration is based on the mean data rate, it is efficient for constant bit rate (CBR) traffic. For variable bit rate (VBR) traffic, however, delay bound of some admitted traffic flows may be violated. Several previous works suggested that, through reporting queue status to schedulers before transmitting packets, each QSTA can be allocated the transmission opportunity (TXOP) based on the deadline of its buffered packets. To satisfy all requested delay bounds, timely queue status reports cause considerable overheads and thus, lead to inefficient bandwidth utilization. In this paper, we adopt multi-polling technique, earliest deadline first policy (EDF) and propose an overhead efficient queue status report scheme to provide QoS support. Simulation results show that our proposed mechanism can not only meet the QoS requirements but also manage the bandwidth more efiiciently in comparison with previous works.