無線區域網路資料速率估計排程演算法

Abstract

中文摘要

隨著今日無線網路上即時性應用的增加，我們需要某些方案來提供更適合的服務，而混和式協調功能(HCF)即是為了提供網路協定(IP)品質的服務保證給IEEE 802.11e架構下的無線區域網路而設計。比起傳統的盡力式傳輸模式，IEEE 802.11e對於不同的應用提出了針對優先性分級的架構，以達到服務品質的區別。在本論文中，我們將提出適用於IEEE 802.11e混合式協調功能控制之通道存取機制(HCCA)排程器的資料速率估計演算法。

從IEEE 802.11e所提供的參考排程方案的評估，我們得知排程中負責的資料流若非嚴格的固定位元率(CBR)時，這個方案的效能並不是很好。因此我們需要設計一個更有彈性的方式，對於擁有不同特性應用的服務品質保證站台(QSTA)，動態地調整分配之傳送機會(TXOP)的估計。藉由提出的排程演算法，服務品質增進擷取點(QAP)能夠為這些對服務品質敏感的資料流，提供一些可以保證的服務品質參數，如延遲、封包漏失率與頻寬。提出的演算法的效能已藉由在網路模擬器第二版(NS-2)的電腦模擬來做評量，並將與IEEE 802.11e草案中提出的參考排程器作一個比較。

Abstract As the real-time applications used in today’s wireless network grow, we need some schemes to provide more suitable service for them. HCF was designed to provide IP quality of service guarantees in IEEE 802.11e WLANs. Compared with the traditional best-effort transmission scheme, IEEE 802.11e presents architecture to do traffic differentiation according to different QoS requirements. This thesis presents a data rate estimation algorithm for the scheduler of the IEEE 802.11e Hybrid Coordination Function (HCF) Controlled Channel Access (HCCA) mechanism.

From the evaluation of referenced scheduling scheme provided in IEEE 802.11e, we know that it does not perform well on traffic which is not strictly CBR. Therefore, we need to design a more flexible scheme to dynamically adjust the estimation of TXOP allocated to the QSTA with different characteristics of applications. With the proposed scheduling algorithm, the QAP can provide guaranteed quality of service parameters such as delay, packet loss rate, and throughput for the QoS-sensitive traffic. The performance of the algorithm is evaluated through computer simulation on network simulator 2 (ns-2) and compared with the referenced scheduler proposed in the draft of IEEE 802.11e task group.