臺灣博碩士論文加值系統

在IEEE 802.16的標準中，網狀模式中只定義了單播與廣播方式的資料傳輸模式。以往要達成群播的目的，主要是以多個單播來依序做傳送。因此這樣的傳輸會造成整個網路的頻寬浪費以及資料接收到的延遲時間會較長。本篇論文根據集中式排程的方式提出一個群播的路由及排程方法利用動態排程與同步傳輸來改善之前群播的方法，同時也提升網路資源的使用。同步傳輸是利用無線訊號傳輸的特性，讓沒有受到傳輸干擾的鏈結可以在同個時間做內同步傳輸，但需要較好的集中式排程方式。據我們所知目前沒有人將其用在群播上，而群播樹的結構是不斷變化，使用相同的排班的方法將會影響的傳輸時間的長度。在我們提出的新方法有能力分析群播樹的架構來決定這個群播樹適合哪種排程策略來提升同步傳輸的機會以及減少傳送時間，此外我們更考慮利用同步傳輸依序的傳送不同的封包到相同接收端來完成一個群播資料的傳送，模擬結果驗證了我們的方法在不同的廣播樹下，除了擁有穩定的傳輸時間外，還可以有效增加網路的使用率以及減少資料傳輸的延遲時間。

In IEEE 802.16 mesh mode, the procedures of unicast and broadcast are defined, and procedure for multicast is not available. To multicast identical data packets to multiple receivers, the traditional approach uses multiple unicast to replace multicast to complete the delivery. Therefore, it not only wastes bandwidth of the entire network but also causes delay of data forwarding. In this thesis we propose a centralized multicast route and schedule scheme which uses dynamic scheduling techniques for concurrent transmissions to improve our previous work and boost network utilization. Concurrent transmissions exploit the characteristics of the wireless signal transmission, and use centralized scheduling to allow multiple transmissions at the same time without transmitting interference. However, as far as we know, no one uses it in multicast. The structure of multicast tree is ever-shifting which would in turn affect the length of transmission when using the same mesh scheduling scheme. The proposed multicast scheme has the ability to analyze the structure of multicast tree, and then dictates a suitable scheduling strategy based on the structure of multicast tree to enable more concurrent transmissions and decrease overall transmitting time. Moreover, we also consider the situation that multicast multiple packets to the same receivers in order to complete a multicast data delivery with concurrent transmissions. The simulation results show that when our new multicast scheme performed in different multicast trees, the proposed scheme not only has stable transmission time but also boosts the network utilization and reduces the delay time of each receiver.

誌謝 i
摘要 ii
Abstract iii
Table of Contents iv
List of Figures v
Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Objectives 2
1.3 Thesis Organization 3
Chapter 2 Related Work 4
2.1 Overview of WiMAX Mesh Networks 4
2.2 Multicast Schemes in WiMAX Mesh Networks 6
2.3 Concurrent Transmissions Schemes 7
Chapter 3 The Proposed Multicast Scheme 11
3.1 Overview of the Proposed Multicast Scheme 11
3.2 Transmission Count Normalization 13
3.3 Tree Analysis 15
3.4 Dynamic Scheduling 18
3.5 Extended Dynamic Scheduling 22
Chapter 4 Performance Evaluation 27
4.1 Simulation Setup 27
4.2 Simulation Results 29
Chapter 5 Conclusions 47
References 48

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