無線網路中具備QoS之多媒體傳輸機制設計與分析

Abstract

因通訊技術進步,在無線網路裡傳送多媒體資料變得日益普及。這些多媒體應用程式,像是影音相關服務,特別注重傳送過程中的服務品質,因為其服務品質的程度大幅影響使用者的體驗。但是,目前既存的 IEEE 802.11 無線網路對於即時性的資料傳輸以及服務品質的保證仍有很大的改善空間。在本論文裡,我們分析多媒體資料在傳輸過程中的行為模式,並且試著去解決在 IEEE 802.11無線網路中提供服務品質保證所遭遇的問題。我們首先整理了各種多媒體資料的傳輸特性,並且指出目前 IEEE 802.11 媒介存取層在處理多媒體和即時資料需改善的部分。而根據網路的拓樸,我們針對典型的基礎架構網 路 (Infrastucture) 提出一個中央管控式的媒介存取機制。接著為了跟上最新的實體傳輸協定 IEEE 802.11ac,我們配合 DL MU-MIMO 技術並 提出一個新穎的、高效能的媒介存取機制。同時我們提出了一個品質調整策略演算法來提升多媒體的使用者體驗。而為了解決在隨意網路 (Ad Hoc)中提供服務品質保證所遭遇的問題,我們挑選了新興的車載隨意網路 (VANET),並根據其網路特性調整所提出之作法,重新建置一具備服務品質保證的分散式媒介存取機制。

Nowadays, delivering multimedia traffic in IEEE 802.11 wireless net- works has become more popular than before. Multimedia applications such as voice/video applications need the quality of service (QoS) guaranteed and the user experience in an important metric. However, the existing medium access method of 802.11 wireless networks is not designed for providing real-time services, not to mention to provide guaranteed QoS. In this thesis, we analyze the traffic character of multimedia transferring and try to solve the existing problem of providing QoS in 802.11 wireless networks. We first summarize the types of multimedia traffic and figure out the difficulty of the IEEE 802.11 medium access control (MAC) protocol for delivering multimedia traffic. Ac- cording to the network type, we propose a QoS provision centralized schedul- ing algorithm for the classical infrastructure network. Furthermore, to follow up the innovation of radio technology, we propose a novel and high-efficiency channel access method called multi-polling controlled access (MPCA) for the latest released protocol, IEEE 802.11ac. In addition, we also implement a quality adjustment strategy (QAS) to provide better user-experience. Finally, to solve the problem of providing QoS in ad hoc networks, we consider the IEEE 802.11p vehicular ad hoc network (VANET) and propose a V2V QoS guaranteed channel access to support QoS.