連豊力Lian, Feng-Li臺灣大學:電機工程學研究所謝育霖Shieh, Yui-LinYui-LinShieh2010-07-012018-07-062010-07-012018-07-062008U0001-2707200816401400http://ntur.lib.ntu.edu.tw//handle/246246/187953無線網路系統於近年已逐漸被廣泛應用與研究。在由多個無線路由器所建構的無線網路平台，行動式終端機考慮到每位使用者占用的網路頻寬與無線訊號強度接收情況，如何選擇所連接的路由器是一個重要的議題。在客戶端漫遊下資訊傳輸的過程中，每位客戶端若能考量到整個網路平台內的頻寬公平性，通常有助於提高網路使用率及資訊交換的效率。了要達到提高客戶端於切換路由器時的效能，在本論文中，我們提出了基於訊號衰減與封包遺失比率的演算法，用以達成決定切換路由器的時機。此方法不僅改善傳統上對於切換路由器的方式，並且降低於演算法本身的複雜度。傳統的訊號接收強度越強為優先法與加入臨界值於接收訊號強度法，亦用來與我們所提出的演算法做比較。經過多次模擬與實驗，結果顯示基於訊號衰減與封包遺失比率的演算法可以達到較好的切換路由器時機。同時也能提高整體系統的效能與穩定性。戶端公平性分配在多個無線路由器與多個客戶端的環境下扮演了極重要的角色，考量到公平性分配的同時亦會影響到漫遊客戶端對於切換路由器的時機。以系統生產率實現為主的演算法在本論文中被詳細的討論。經由實驗和模擬，我們可以發現結合了基於訊號衰減與封包遺失率和以系統生產率實現為主的演算法，不僅提高了整體無線網路的系統生產量同時亦改善了漫遊客戶端於切換路由器時對於系統效能上不必要的浪費。In recent years, wireless network systems have been widely researched and used in applications. The method in making the choice of access point while taking the bandwidth and signal strength into consideration by the mobile terminal is an important issue in a wireless network platform composed of multiple devices. During the process of information transmission to mobile clients, if the client can recognize the Max-Min fairness of the entire network, it can usually help increase the efficiency of the network usage and information exchange. o achieve the increase in efficiency when the client conducts the switch between access points, we propose the algorithm of SDPL in this thesis. This algorithm serves the purpose of deciding the timing for handoff. This method not only improves the conventional way of handoff between access points, but also lowers the complexity of the algorithm itself. The traditional method of higher priority by signal strength and the augment threshold value in RSS is also compared with the algorithm we have proposed. After many times of simulation experiments, the results indicate that SDPL algorithm can achieve better timing in handoff and also increase the stability and efficiency of the whole system. ax-Min fairness plays an important role in the setting of multiple access points and multiple clients. Taking Max-Min fairness of the system into consideration will also affect the timing of the mobile client to handoff. The FbF algorithm is discussed in close detail in this thesis. Through experiment and simulation, we discover an algorithm that combines both SDPL and FbF not only enhances the system throughput of the whole wireless network system but also, at the same time, lessens the waste of efficiency of mobile device during handoff between access points.摘要 IBSTRACT IIIONTENTS VIST OF FIGURES IXIST OF TABLES XVHAPTER 1 INTRODUCTION 1.1 Motivation and Introduction 1.2 Wireless Platform 3.3 Contribution of the Thesis 7.4 Organization of the Thesis 8HAPTER 2 BACKGROUND KNOWLEDGE AND LITERATURE SURVEY 11.1 Literature Survey and Related Researches 12.2 Handoff Structure in Wireless Overlay Networks 15.2.1 Handoff Architectures 16.2.2 Decision Time Algorithms 17.3 Fairness Notion in Routing Path 19HAPTER 3 PROBLEM FORMULATION 21.1 Roaming in a Wireless Network System 22.2 Handoff Architectures and Algorithms in Homogeneous Wireless Data Networks 23.2.1 RSS in Handoffs 24.2.2 Path Loss and Shadowing 29.2.3 SDPL 31.3 Interaction of Multiple Clients within Multiple APs 31.3.1 Wireless Network Model 32.3.2 System Description 33.4 Fairness 34HAPTER 4 HANDOFF DECISION ALGORITHM 37.1 Control Architecture of Handoff Algorithm 37.2 Method 1: Strong Signal First (SSF) 41.2.1 Method Description 41.2.2 Control Architecture Design 43.3 Method 2: Augment Threshold Value in RSS 44.3.1 Method Description 44.3.2 Discussion 45.4 Method 3: Signal Decay and Packet Loss Ratio Algorithm (SDPL) 46.4.1 Method Description 46.4.2 Control Architecture Design 47.5 Method 4: SDPL with BbF & TbF 48.5.1 Fairness Notion in Multi-Client and Multi-AP Wireless Hotspots 48.5.2 Method Description 49.5.3 Control Architecture Design 57.6 Method 5: SDPL with FbF 58.6.1 Method Description 58.6.2 Discussion 61HAPTER 5 SIMULATION STUDY AND EXPERIMENTAL RESULTS 63.1 Scenario Description 64.1.1 Experiment Environment Description 65.1.2 Simulation Environment Description 71.2 Method 1: Strong Signal First (SSF) 72.2.1 Simulation Result 72.2.2 Experimental Result 77.2.3 Discussion 87.3 Method 2: Augment Threshold Value in RSS 88.3.1 Simulation Result 88.3.2 Experimental Result 91.3.3 Discussion 93.4 Method 3: Signal Decay and Packet Loss Ratio Algorithm (SDPL) 94.4.1 Simulation Result 94.4.2 Experimental Result 98.4.3 Discussion 101.5 Method 4: SDPL with BbF 102.5.1 Simulation Result 102.5.2 Experimental Result 109.5.3 Discussion 111.6 Method 5: SDPL with FbF 111.6.1 Simulation Result 111.6.2 Experimental Result 117.6.3 Discussion 120HAPTER 6 CONCLUSION AND FUTURE WORK 121.1 Conclusion 121.2 Future Work 122PPENDIX 125.1 Fairness [33: Bertsekas and Gallager 1992] 125.2 Max-Min Flow Control [33: Bertsekas and Gallager 1992] 126EFERENCES 1293027341 bytesapplication/pdfen-US無線網路系統無線路由器網路頻寬無線訊號強度行動式終端機頻寬公平性訊號衰減封包遺失系統生產率Wireless network systemaccess pointbandwidthsignal strengthmobile terminalMax-Min FairnessSDPLsystem throughputthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/187953/1/ntu-97-R95921068-1.pdf