臺灣博碩士論文加值系統

在不久的未來，未來的網路將會是異質性。像是全球互通微波存取(WiMAX)和無線區域網路(WLAN)可以各自結合彼此優點，覆蓋範圍及資料傳輸速率在混合式網路系統的基礎上。因此，提供服務品質(QoS)連接無縫式(Seamless)換手(Handoff)在WLAN與WiMAX環境是很重要的議題。然而，在目前的無線網路環境中，許多無線行動裝置使用者在具移動性(Mobility)的狀態下使用即時性服務(如聲音、視訊會議及影像等)時，會面臨跨越網路的服務邊界而進入另外一個網路的服務區域（這機制我們稱之為換手Handoff 或Handover）之時，因此引發新資源之需求，但也往往因無法取得所需之網路資源而造成嚴重的延遲或甚至造成連結的中斷。在本論文中，我們提出一個在異質無線網路環境中，以服務品質(QoS)感知RSVP方法達到使用即時性服務之服務品質(QoS)保證之方法。提出方法基於整合在WiMAX與WLAN網路中，具服務品質(QoS)感知移動架構以保證一定的服務品質(QoS)。在本論文中，藉由行動節點的移動和訊號強度執行預先換手(Pre-handoff)而選擇網路。在另一方面，假如換手(Handoff)觸發了網路擁塞，行動節點依據擁塞控制服務品質(QoS)參數而將會執行換手(Handoff)。我們提出的方法可以有效降低封包傳輸因換手(Handoff)時需重新繞路連線所造成的的延遲(Delay)時間和換手阻塞率在異質無線網路。

In the near future, future network environments will be heterogeneous. The hybrid networks based on systems such as WiMAX (Worldwide Interoperability for Microwave Access) and WLAN (Wireless Local Access Networks) can combine their respective advantages on coverage and data rates. Therefore, it is a significant issue of how to provide seamless handoff for QoS connections in WLAN and WiMAX environments. However, in the wireless networks we use today, many mobile users still cannot obtain the network resources they need when employing the real-time services like voice, video conferences, video IP phone, and so forth while handoff occurs, and it causes a serious delay or even the break of the link. Thus, our approach is proposed to guarantee the QoS with QoS aware RSVP in heterogeneous wireless networks. The proposed scheme is based on QoS aware mobility architecture to guarantee a certain QoS in integrated WiMAX and WLAN networks. In this paper, the network selection is ignited by mobility of MS and pre-handoff is performed based on signal strength. On ther other hand, if the selection is triggered by the congestion, we will perform the handoff based on congestion controlling delay according to the QoS parameters. Our proposed scheme of resource pre-reservation can reduce the delay time of re-routing while handoff occurs and handoff blocking rate in the heterogeneous wireless networks efficiently.

摘要 I
Abstract II
Contents IV
List of Figures VI
List of Tables VII

Chapter 1 Introduction 1
1.1 Quality of Service (QoS) 1
1.2 Design Motivation and Concept 3
1.3 Thesis Organization 6
Chapter 2 Related Work 7
2.1 Heterogeneous Wireless Networks 7
2.2 IEEE 802.11 WLAN 10
2.3 IEEE WiMax/802.16 Network 13
2.4 Resource ReSerVation Protocol (RSVP) 15
2.5 Issues of Supporting RSVP in Heterogeneous Wireless Network Environments 17
2.6 Related Researches 18
Chapter 3 Heterogeneous Wireless Networks 20
3.1 Overview of Hybrid Wireless Network Architecture 20
3.2 The Model for QoS Aware RSVP 21
3.3 Proposed QoS aware RSVP Scheme 22
3.4 Reserving Management 22
3.5 Handoff Decision and Network Selection 24
Chapter 4 Performance Evaluation 28
4.1 Simulation Environment 28
4.2 Simulation Results 29
Chapter 5 Conclusions and Future Work 34
5.1 Conclusions 34
5.2 Future Work 35
References 36
List of Figures
Fig 1 1 Simplified models of factors that form perception of QoS 2
Fig 2 1 Heterogeneous Wireless Network 8
Fig 2 2 Network heterogeneity 9
Fig 2 3 Relation between service, protocols and data bearer 10
Fig 2 4 An example of an IEEE 80216 mesh network 13
Fig 2 5 Scenario of RSVP 16
Fig 3 1 Heterogeneous scene in hybrid network 20
Fig 3 2 The changing of network state with the different RSS threshold 23
Fig 3 3 The MSi moves from WLAN to WiMAX and WLAN signal overlap areas 26
Fig 3 4 The process for handoff decision 27
Fig 4 1 The lost packet probability vs number of nodes 29
Fig 4 2 The handoff blocking probability in different mobility of MS 30
Fig 4 3 The handoff call dropping probability vs duration of time 31
Fig 4 4 Cancel probability vs number of WLANs 32
Fig 4 5 The delay comparison of network selecting vs speeds of MS 33
List of Tables
Table 1 1 The example of objective metrics 3
Table 1 2 The example of subjective metrics (MOS: Mean Opinion Score) 3
Table 2 1 IEEE 80211 standards and worldwide frequency bands 11

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