隨著使用者使用無線網路的普及，勢必需要架設更多的基地台來服務，此時換手機制就是一個很重要的議題了。然而因為使用者在服務邊緣來回移動，會造成系統頻繁地作換手行為，產生乒乓效應，導致延遲時間增加和整體系統效能降低。我們提出了基於部分頻寬再利用之換手機制，考慮多個服務區域的傳輸頻率分配，基地台能重複使用頻寬，改善整體系統的頻率使用率。然後在部分頻寬再利用的環境下，所造成的額外干擾源會增加整體系統的不必要換手次數，我們所提出的換手機制，便是希望能夠利用部分頻寬再利用來改善整體系統的吞吐量和頻率使用率，也能夠避免額外的干擾源所增加的換手次數，並且採用訊號雜訊比和距離來做為判斷，所以相較於LTESHHO的換手演算法，我們所提出的機制能夠多減少8%的不必要換手次數。

With the popularity of wireless networks, it needs to support user’s mobility cross different base stations, hence, the handover mechanism becomes an important issue. When the user frequently moves between two cells, it will occur the Ping-Pong effect that increases the delay time and reduces the efficiency of system. In this thesis, we proposed a new handover mechanism by considering the fractional frequency reuse (FFR) over relay networks to reuse frequency in multi-cells. The proposed method can reduce the unnecessary handover caused by the interference in the system of FFR. It uses the value of signal to interference and noise ratio (SINR) and the parameter of distance to make handover decision. The simulation results indicate the proposed handover mechanism can reduce more than 8% of the handover number in average in comparison to the competing method in the best case.

Abstract ii
Table of Contents iii
List of Figures iv
List of Tables vi
Chapter 1. Introduction 1
1.1 Overview 1
1.2 Motivation and Goal 4
Chapter 2. Background and Related Work 8
2.1 Fractional Frequency Reuse (FFR) 8
2.2 Channel Model 14
2.3 Transparent and Non-transparent Relay 16
2.4 Overview of Handover 19
2.5 Shadow Fading Model 24
Chapter 3. The Proposed Scheme 25
3.1 Problem Definition 25
3.2 The Proposed Handover Process 29
3.3 Formulation of the Proposed Scheme 32
3.4 System Analysis 37
Chapter 4. Simulation 46
4.1 System Topology 47
4.2 Simulation Parameters 49
4.3 Performance Evaluation 52
Chapter 5. Conclusions 63
References 64

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