由於802.11技術提供彈性與便利性無線網路存取功能，目前大多數的消費電子產品也都把Wi-Fi功能訂為產品的基本功能，所以消費者使用無線網路的頻率也大大提升，另外一些大型賣場、速食店與捷運也都配置無線熱點，民眾隨時隨地都可以透過無線熱點連至網路。此外多媒體應用服務的快速增加，大眾想要透過無線網路獲得語音、音樂與影像服務的需求也大幅增加，過去透過無線網路下載一般資料還沒有問題，但是如果是要提供越來越大量的多媒體服務就不得不考慮QoS需求，像是保證網路頻寬以及有限制的delay與jitter來確保這些多媒體網路服務的品質。802.11e是IEEE針對QoS需求所制訂的標準，802.11e提出EDCA與HCCA的QoS機制，目前WiFi產品中有實作出的QoS機制為EDCA，其屬於contention based。而HCCA屬於polling based，且需要在AP與STA端加入控制電路，在硬體實現與控制上都增加不少困難度，所以一般無線產品上大多無此功能。雖然EDCA可以提供無線網路QoS機制增加網路的性能，但是EDCA實現也需要增加額外的硬體電路像是：Backoff engine、CWmin register、CWmax register、Virtual collision handler, ...,等，這也增加了網路裝置的成本與電路設計上的困難，本論文主要希望能在driver sublayer透過簡單的scheduling algorithm達到QoS效果，用以取代無線裝置EDCA電路，減低無線裝置硬體設計上的複雜性與成本，論文的最後會比較DCF與EDCA與我們提出driver layer scheduling algorithm實際在Ralink無線網卡上執行的效果，結果可以看出driver layer scheduling algorithm執行結果可以達到無線網路所需的QoS效果。另外我們也對所提出的排程演算法進行數學分析，證明對於不同的網路連線，可以藉由調整優先權參數達到參數化(parameterized)以及差異化(differentiated)QoS的目標。

Because the IEEE 802.11 technology provides flexible and convenient wireless access capability, many consumer electronic products include Wi-Fi as one of the basic functions. Therefore, consurmers frequently use wireless networks no matter where they are in supermarkets, food stores, or stations. When surfing the Internet, the multimedia service applications are growing rapidly. People increasingly enjoy voice, music and video services via wireless networks. Therefore, Quality-of-Service (QoS) technology in wireless networks becomes essential. A QoS scheme needs to guarantee bandwidth, limited delay and limited jitter to ensure the Internet service quality. The IEEE defines 802.11e standard to enhance traffic QoS by parameterization and differentiation of the Enhanced Distributed Channel Access (EDCA) and HCF Controlled Channel Access (HCCA) mechamisms. Currently, most Wi-Fi products vendors only implement the contention-based EDCA mechamism. The HCCA is polling-based mechamism requiring additional control circuits in the Access Point (AP) and Station (STA). Similarly, EDCA also needs additional hardware circuits such as backoff engine, CWmin register, CWmax register, virtual collision handler,…, ect. Both hardware implementation difficulty and cost of HCCA and EDCA are high. In this thesis, we propose a simple scheduling algorithm called Media access control in Driver Sublayer Scheduling (MDSS) to perform QoS management among traffic flows. We prove that the proposed MDSS avoids hardware implementation and thus reduces cost and complexity of Wi-Fi MAC. To perform comparison, we use the Ralink WiFi adapter to realize the traditional DCF, EDCA, and the proposed MDSS scheduling. The oringinally EDCA function in the adapter is turned off by programming contention window parameters to minimum. Simulations and experiments show that the MDSS provides well QoS management without additional hardware cost in the MAC chip. Besides, we also perform mathematical analysis of the MDSS to prove that the MDSS achieves the parameterized and differentiated QoS according to various traffic requirements.

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