802.11 通訊協定下之強固式多媒體輪詢策略

Abstract

在無線通訊中，頻寬一直是個很重要的資源，特別是在多媒體傳輸上，頻寬資源利用的好壞將影響整個系統的效率。在 IEEE 802.11 標準中，對於非競爭週期，並沒有制定關於資源分配的方法。因此，Ranasinghe等人提出分散式不足額頻寬循環輪替法(distributed deficit round robin) 針對無線網路上傳輸多媒體資訊，來管理其頻寬分配。除此之外，為了改善系統的效能，Ganz引進了超級輪詢 (super-poll)的概念，比較超級輪詢與單一輪詢 (single poll) 之輸出效能，證實超級輪詢可提升到85%。本論文將利用分散式不足額頻寬循環輪替法與超級輪詢法的優點，並加以整合，提出改進IEEE 802.11通訊協定的強固式輪詢方法。經模擬驗證得出，傳輸延遲比集中協調式功能(point coordination function, PCF) 最大可快到8倍，而且所增加的額外負擔並不顯著，是在可容許的範圍內。

Bandwidth is an important and shared resource in wireless communication. Especially, in multimedia transmission, resource allocation algorithm will affect system performance. The IEEE 802.11 standard did not institute scheduling scheme for contention-free period to allocate resource. Thus, Ranasinghe et al. proposed Distributed Deficit Round Robin (DDRR) method to manage bandwidth allocation for multimedia transmission in wireless networks. Besides, to increase system performance, Ganz et al. introduced super-poll concept into IEEE 802.11 Point Coordination Function (PCF). They showed that the super-poll method improves the throughput up to 85% when compared with the single poll mechanism. In this thesis, based on DDRR and super-poll, we present a more efficient algorithm, called Robust Polling Scheme (RPS), for bandwidth allocation. This scheme is an improvement of the IEEE 802.11 protocol. The simulation results show that the transmission delay of RPS is reduced up to eight times as small as the native PCF method and throughput is also acceptable.