本論文針對無線區域網路(Wireless Local Area Networks, WLANs)中，現有的(Orthogonal Frequency Division Multiple Access, OFDMA)上傳機制所造成的傳輸延遲問題，提出有效的解決策略。現今隨著無線網路迅速發展，人們對於WLANs的需求越來越高，為了滿足使用者的需求，IEEE 802.11ax標準加入了OFDMA的機制，讓多個節點可以同時傳輸資料。而在IEEE 802.11ax上傳機制中，有兩種傳輸方式: 1)透過競爭的方式傳輸，2)透過AP調度的方式傳輸。這兩種傳輸方式皆可能出現後面要傳送資料的節點因傳輸延遲時間太長而造成封包丟棄的問題。因此本論文提出一種新的分配機制，用於解決節點傳輸延遲問題。此機制將選擇資料量較少的節點先分配傳輸。另外本論文亦提出一判斷方式以切割資料，來降低傳輸延遲時間。根據模擬結果顯示此機制可以有效降低傳輸延遲時間，並有效的提高網路的效能。

The paper proposes effective solutions to the transmission delay problem caused by the OFDMA (Orthogonal Frequency Division Multiple Access) uplink transmission delay in wireless local area networks (WLANs). Nowadays, with the rapid development of wireless networks, the demand for WLANs is getting higher and higher. To meet the needs of high traffic load, the IEEE 802.11ax standard adopts the OFDMA mechanism to allow multiple users to transmit at the same time. In IEEE 802.11ax uplink transmissions, there are two transmission methods: 1) Random Access (RA) and 2) Scheduled Access (SA). Both two transmission methods suffer the long transmission delay problem. Therefore, the paper proposes a new resource allocation mechanism to solve the long transmission delay problem. The proposed mechanism can select the node with a small amount of data to allocate resources first. Moreover, the proposed mechanism also designs a criterion to cut the data to reduce the transmission delay time. According to the simulation results, the proposed mechanism can effectively reduce the transmission delay time and improve the performance of the network.

第1章	介紹	1
第2章	背景知識	13
第3章	最小化傳輸延遲問題模型建	17
第4章	傳輸延遲最小化RU分配方案(RU Allocation with Transmission Delay Minimization Scheme (RATDM))	23
4.1理論基礎	23
4.2AP切割資料的方式	28
第5章	效能評估	31
5.1實驗場景及參數設定	31
5.2實驗結果	32
5.3實驗總結	35
第6章	結論	36
參考文獻	36
 
圖目錄
圖一、DL MU-OFDMA傳輸	2
圖二、TF的封包格式	3
圖三、UORA傳輸機制	4
圖四、AP所告知的傳輸時間較短	5
圖五、BSR傳輸	6
圖六、BSR的封包格式	6
圖七、BSR傳輸(padding)	7
圖八、OBSS圖	8
圖九、PSR操作時序圖	8
圖十、OPSR 操作時序圖	9
圖十一、SA RU和RA RU 操作時序圖	10
圖十二、OFDMA	13
圖十三、20MHz 頻道中的 RU 位置	15
圖十四、網路模型	17
圖十五、AP排程	19
圖十六、資料量較大的節點先分配RU	24
圖十七、資料量較小的節點先分配RU	25
圖十八、AP分配較小RU	26
圖十九、AP分配較大RU	27
圖二十、RATDM運作方式	29
圖二十一、AP選擇不同大小的RU分配網路延遲	32
圖二十二、AP選擇不同大小的RU分配網路效能	33
圖二十三，AP選擇不同節點先分配RU的網路延遲	34
圖二十四，AP選擇不同節點先分配RU的網路效能	35
 
表目錄
表一、不同頻寬的RU個數	14
表二、20 MHZ 頻段中可用的 RU 分配方案	14
表三、在20MHz中不同RU中的數據速率(Mbps)	15
表四、MCS的SNR門檻值	16
表五、符號的定義	18
表六、模擬參數[18]	31

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