無線區域網路即時性資料傳輸品質保證之動態調整競爭性通道存取資料參數

Abstract

隨著無線區域網路快速地普及，近來提升無線網路的能力越來越引人注意，目的在於提供較嚴格的服務品質保證(QoS)給即時資料傳輸。在本論文的探討中，我們評估新的IEEE 802.11e標準中所用來支援服務品質保證的機制，也就是在原本IEEE 802.11標準中的媒介存取控制層(MAC)，定義新的加強媒介存取控制層機制來提供服務品質保證。我們發現該標準中的機制EDCA可以藉由不同的存取分類(Access Category)提供令人滿意的差別服務。然而，在傳輸負載過多的狀況下，對於即時資料的傳送，EDCA並不能提供有效的服務品質保證。因此，我們提出盡力式資料(best-effort data)的控制以及允入控制(admission control)等機制，希望在高網路負載的情況下，對於即時資料的傳輸，EDCA依然能夠提供較佳的服務品質保證。主要的觀念是將即時資料傳送(real-time transmission)以及盡力式資料傳送(best-effort transmission)分開處理。擷取點(access point)根據網路的傳輸狀況，幫助工作站(station)判斷決定接受或拒絕即時資料的傳送和動態地控制盡力式資料傳送以保護正在傳送的即時資料。經由模擬驗證，我們證實了該機制在高負載狀況下能夠發揮功效。

With the fast deployment of wireless local area networks (WLANs), the ability of WLAN to support real time services with stringent quality of service requirements has come to the fore. In the thesis, we evaluate the capability of QoS support in the IEEE 802.11e standard, which is the medium access control (MAC) enhancement for QoS support in IEEE 802.11 standard. We find that EDCA provides satisfactory service differentiation among its different access categories. However, in the case of heavy load traffic, the QoS of real-time traffic can not be assured. Thus, we proposed best-effort data control and admission control schemes that enable EDCA to provide quantitative bandwidth guarantees. Real-time transmissions and best-effort data transmissions are handled differently. The access point (AP) helps stations make decisions on acceptance or rejection of real-time traffic and dynamically control the data parameters to protect the existing real-time traffic according to the network condition. Simulation results confirm the effectiveness of the proposed methods.