臺灣博碩士論文加值系統

IEEE 802.16 WiMAX 是目前相當受到矚目與擁有發展潛力的一種網路接取技術而目前較為廣泛使用的則是 IEEE 802.11 WLAN 技術。我們不難發現未來此兩種技術會有整合的趨勢，進而產生此兩種網路結合的異質性網路。TCP 是目前較為廣泛使用的傳輸層協定，可以預見的，將來會有越來越多的應用使用TCP透過這種整合後的異質性網路來上網。因此，本碩士論文主要針對此種由無線都會網路 IEEE 802.16 WiMAX 與 IEEE 802.16 WLAN所組成的異質網路上，其應用之TCP為傳輸層協定，所得到的效能進行詳細的模擬與分析研究。
主要影響TCP傳輸效能的因素在於無線都會網路的MAC層的控制與排程(Control and scheduling)協定設計的方式。由於無線都會網路是相當新的通訊技術，並且是還在制訂中的一套通訊協定，與其他通訊協定較為不同的地方在於無線都會網路所提供的服務為無線的寬頻帶存取技術(Wireless Broadband Access)，為了有效低瞭解此種MAC層的協定設計對無線環境對TCP應用的傳輸效能影響，我們採用被廣泛接受的網路模擬軟體NS-2(Network Simulator version 2)來模擬與驗證無線都會網路的各種特性與TCP應用的效能評估。希望藉由模擬與分析的方式來幫助瞭解無線都會網路這種新的網路協定對於TCP的應用有什麼值得探討與改進的地方。

The IEEE 802.16 WiMAX is becoming increasingly widely used in first/last mile internet access technology. We note that the heterogeneous network is also becoming increasingly widely used in future by combining the IEEE 802.11 WLAN technology and the IEEE 802.16 WiMAX technology. The TCP is the most popular transport layer protocol for different applications; therefore in this thesis, we investigate the effects of the IEEE 802.16 WiMAX MAC operations on TCP performance over such heterogeneous network by studying the throughput and fairness performance because we note that the design of MAC layer has significantly impact on the throughput performance of TCP.
Since the standard IEEE 802.16 is relatively new and the standardization process is still ongoing, and there are no device or testbed to evaluate the effects of IEEE 802.16 MAC control on TCP performance, we adopt the most popular and acceptable network simulator software which is “Network Simulator version 2” to simulate and to evaluate the TCP performance over the heterogeneous network and also the effect of the lossy wireless channel.
The simulation results helps us to understand where the problems of MAC layer; furthermore, we can analysis and improve it for better TCP performance.

Chapter 1 Introduction 1
1.1 IEEE 802.16 WiMAX Networks 3
1.1.1 Point-to-Multipoint Mode 5
1.1.2 Mesh Mode 6
1.1.3 IEEE 802.16 MAC Operations and Features 7
1.2 IEEE 802.11 WLAN Networks 10
1.3 Related Work 14
1.3.1 IEEE 802.16 14
A . QoS for the MAC Protocol of IEEE 802.16 WiMAX Networks 14
B . Mobility of IEEE 802.16 WiMAX Networks 15
1.3.2 TCP Performance over Heterogeneous Networks 15
1.4 Motivation 17
1.5 Thesis Organization 18
Chapter 2 Simulation Environment 19
2.1 Parameter Setting 20
2.2 Assumptions 22
2.3 Scenarios 23
2.4 Performance Metrics 24
Chapter 3 Performance Evaluation of One-Way TCP Transfers Scenario 25
3.1 Aggregate Throughput 25
3.1.1 Symmetry Mode 25
3.1.2 Asymmetry Mode 28
3.1.3 Lossy Environment 35
3.2 Fairness 39
3.2.1 Error Free Environment 39
3.2.2 Lossy Environment 43
3.3 Summary 48
Chapter 4 Performance Evaluation of Two-Way TCP Transfers Scenario 50
4.1 Aggregate Throughput 50
4.1.1 Symmetry Mode 50
A . Aggregate Downstream Throughput 50
B . Aggregate Upstream Throughput 52
4.1.2 Asymmetry Mode 54
4.1.3 Lossy Environment 57
A . Symmetry Mode 58
B . Asymmetry Mode 60
4.2 Fairness 61
4.2.1 Symmetry Mode 61
A . Downstream Fairness 61
B . Upstream Fairness 63
4.2.2 Asymmetry Mode 65
4.2.3 Lossy Environment 68
4.3 Summary 71
Chapter 5 Conclusions and Future Work 73
5.1 Conclusions 73
5.2 Future Work 75
References 76

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