本論文針對實時應用(Real-Time Applications, RTA)裝置在存取網路媒介時所遭遇到的延遲過高問題，提出有效的改善策略。近年來由於實時應用的崛起，這些應用已大量的出現在我們的生活周遭，然而無線區域網路中時常有干擾以及壅塞，這些設備可能會因為存取網路媒介時產生競爭失敗或資料碰撞等問題，導致延遲提升，無法滿足實時應用封包的延遲要求。為此，下一代無線區域網路(Wireless Local Area Networks, WLANs)標準-IEEE 802.11be將降低實時應用的無線區域網路設備延遲問題視為制定協議的主要目標之一。因此本論文針對RTA節點存取網路媒介時延遲過高的問題進行探討，並透過預先分配網路資源的思路設計出一媒體存取控制協議，簡稱為Dynamic Uplink OFDMA Resource Allocations (DURA) MAC，以解決實時應用裝置在存取網路媒介時的延遲問題。DURA的特色是可讓無線存取點(Wireless Access Point, WAP)在擁有網路環境資訊時，提供RTA節點免競爭的網路媒介存取方式，讓RTA節點可以將資料封包優先送出，以降低RTA節點的延遲。另外，本論文也透過MATLAB進行模擬並與其他相關研究進行比較，結果顯示DURA的效能在密集網路環境中皆優於IEEE 802.11ax隨機存取機制和相關研究，並能滿足RTA節點的延遲要求。

This paper proposes effective strategies to improve the high latency problem encountered by Real-Time Ap-plications (RTA) devices when accessing media. In recent years, due to the rise of real-time applications, a large number of RTA applications have appeared in our lives. Due to interference and congestion in wireless local area networks (WLANs), RTA may face competition fail-ure or data collision when accessing the media, which will cause the delay to increase and the QoS (Quality of Service) requirements of RTA cannot be satisfied. To this end, the standard of the next-generation WLANs-IEEE 802.11be regards reducing the latency of RTA applica-tions as one of the main goals of the standard. Therefore, the paper takes the problem of excessive delay when RTA applications access media into consideration and designs a MAC (Media Access Control) protocol, named Dynam-ic Uplink OFDMA Resource Allocations (DURA), to deal with the problem. The idea of DURA is to allocate net-work resources to RTA applications in advance such that the contention and interference can be reduced and the latency of RTA applications can be shortened as well. The feature of DURA is that when the wireless access point (WAP) has the requirements of the RTA applica-tions, WAP can let these RTA applications access media without contention to reduce the latency of the RTA ap-plications. To verify the effectiveness of DURA, the paper also conducts simulations by means of MATLAB. Simu-lation results show that the performance of DURA is bet-ter than those of the IEEE 802.11ax random access mechanism and related research in dense network envi-ronments. Moreover, DURA can also meet the latency requirements of RTA applications.

第1章	介紹	1
第2章	背景知識	4
2.1資料延遲約束(Data Latency Constraint)	4
2.2封包到達週期 (Packet Flow Rate)	7
2.3相關工作	8
第3章	設計理念及假設	14
3.1相關假設	14
3.2設計理念	15
第4章	用於實時應用之低延遲網路媒介存取控制協議(DURA)	17
4.1高延遲要求優先服務(High DLC First Allocation, HDFA)	17
4.2資料傳輸周期延長 (Increase TXOP Duration, ITD)	19
4.3單RU多節點分配 (Multiple STAs in One RU, MSOR)	22
4.4調整封包大小(Packet Size Adjustment, PSA)	26
第5章	效能評估	29
5.1模擬場景與參數	29
5.2實驗結果	30
第6章	結論	38
參考文獻	39
 
圖目錄
圖一、RTA節點競爭失敗問題(FCP)示意圖	2
圖二、RTA節點傳輸失敗問題(FTP)示意圖	3
圖三、RTA節點封包延遲發生區域示意圖	4
圖四、RTA節點封包到達週期示意圖	7
圖五、多頻道操作示意圖	8
圖六、多頻道操作用於增加傳輸效能示意圖	9
圖七、多頻道操作用於增加傳輸可靠性示意圖	9
圖八、Default EDCA parameter set	10
圖九、增加RTA等級的EDCA parameter set	10
圖十、OFDMA示意圖	11
圖十一、GRA演算法分配結果示意圖	12
圖十二、IEEE 802.11ax RU可分配個數類型[8]	12
圖十三、GRA演算法碰撞示意圖	13
圖十四、協議基本運作	15
圖十五、RTG節點優先分配示意圖	18
圖十六、新增傳輸機會時間Tt2示意圖	19
圖十七、Trigger Frame format[1]	20
圖十八、User info format[1]	20
圖十九、單個RU分配兩個節點示意圖	22
圖二十、封包同時到達區間示意圖	23
圖二十一、封包同時到達區間內資料碰撞示意圖	23
圖二十二、分配RTV節點示意圖	24
圖二十三、封包同時到達區間對比示意圖	24
圖二十四、未進入PSA前分配結果示意圖	26
圖二十五、透過PSA調整後的分配結果示意圖	27
圖二十六、分配策略流程圖	28
圖二十七、ITD和MSOR搭配PSA延遲對比	30
圖二十八、ITD和MSOR搭配PSA效能對比	31
圖二十九、MSOR和GRA的延遲對比	32
圖三十、MSOR和GRA的效能對比	33
圖三十一、ITD和GRA的延遲對比	34
圖三十二、ITD和GRA的效能對比	35
圖三十三、模擬延遲效能	36
圖三十四、模擬傳輸效能	37
 
表目錄
表一、實時應用於基本服務集內部延遲要求	6
表二、RTA參數	15
表三、模擬參數	29
表四、分配策略代號	30

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