Title Page
Abstract
Contents
CHAPTER 1. Introduction 15
1.1. Backgrounds 15
1.2. Previous Studies 17
1.2.1. DAS (Distributed Antenna System) 17
1.2.2. CoMP (Coordinated Multi-Point transmission/reception) 18
1.2.3. Intra e-NodeB CoMP 20
1.3. Research Objectives 21
1.4. Chapter Organization 23
CHAPTER 2. Designing of Virtual Cell Network 24
2.1. Overview 24
2.2. Problem Statement 25
2.3. VCN System Configuration 27
2.4. Operation Scenario 33
CHAPTER 3. Uplink Inter-group Scheduling for Minimizing Interference in Virtual Cell Network (VCN) 46
3.1. Overview 46
3.2. Related Works 47
3.2.1. Fractional Frequency Reuse 47
3.3. Problem Statement 47
3.4. Proposed Uplink Grouping Algorithm 48
3.4.1. System Model 48
3.4.2. Basic Idea 49
3.4.3. Conditional SNR based Grouping 49
3.5. Performance Evaluation 54
3.5.1. Interferer Avoidance 54
3.5.2. Simulation Environment 55
3.5.3. Results 56
3.6. Summary 56
CHAPTER 4. Hierarchical Resource Management Providing Network-wise Fairness and Reducing Complexity in VCN 61
4.1. Overview 62
4.2. Related Works 62
4.2.1. Iterative Water Filling 63
4.2.2. Modified Iterative Water-Filling 64
4.3. Problem statement 64
4.4. Proposed Resource Management Algorithm 66
4.4.1. Hierarchical Network Topology 66
4.4.2. Geometrical Grouping 67
4.4.3. Frame Structure 68
4.4.4. Resource allocation 68
4.4.5. Providing Network-Wise Fairness 71
4.4.6. Considering Non-uniform Traffic Distribution 73
4.5. Performance Evaluation 74
4.5.1. Simulation Environment 74
4.5.2. Results 76
4.6. Summary 76
CHAPTER 5. Network-scale Dynamic Fractional Frequency Reuse Scheme Mitigating Inter-VCN Interference in VCN 80
5.1. Overview 80
5.2. Related Works 81
5.2.1. Fractional Frequency Reuse 82
5.2.2. Dynamic Fractional Frequency Reuse 82
5.3. Problem statement 83
5.4. Proposed Resource Management Algorithm 84
5.4.1. System Model 84
5.4.2. Basic Idea 85
5.4.3. Inter-VCN interference recognition 85
5.4.4. Frequency Reuse Factor Decision 87
5.4.5. Dynamic Subchannel Allocation 87
5.5. Performance Evaluation 89
5.5.1. Simulation Environment 89
5.5.2. Results and Discussion 94
5.6. Summary 96
CHAPTER 6. Cognitive Radio Application in VCN: Seamless Spectrum Handover Considering Differential Path-loss 98
6.1. Overview 99
6.2. Related Works 99
6.2.1. Cognitive Radio 99
6.3. Problem Statement 101
6.4. Seamless Spectrum Handover Scheme 105
6.4.1. Low to High case 109
6.4.2. High to Low case 111
6.4.3. Overall operation 111
6.5. Performance Evaluation 112
6.5.1. Outage probability 112
6.5.2. Total number of handovers 115
6.6. Summary 117
CHAPTER 7. Conclusions 120
7.1. Conclusions 120
Summary in Korean (한글 요약) 122
Bibliography 124
Curriculum Vitae 128
List of Publications 131
List of Patents 134
Table 3.1: System environment for evaluating uplink group scheduling 60
Table 4.1: System environment for hierarchical resource management 75
Table 4.2: Fairness Compensation 79
Table 5.1: System environment for hierarchical resource management 90
Table 6.1: System environment 113
Figure 1.1: DAS implementation scenario 19
Figure 1.2: CoMP implementation scenario 22
Figure 1.3: Intra e-NodeB CoMP implementation scenario 22
Figure 2.1: Problems in small cell network 26
Figure 2.2: System configuration for VCN 28
Figure 2.3: Basic conceptual diagram for VCN 30
Figure 2.4: CU (Central Unit) functionality 30
Figure 2.5: Conceptual diagram for advanced VCN 32
Figure 2.6: Conceptual diagram for self-organizing VCN 32
Figure 2.7: CU-concatenated VCN 34
Figure 2.8: RAU-concatenated VCN 34
Figure 2.9: Conceptual diagram of mobile terminal 35
Figure 2.10: Signaling procedure for building up a virtual cell 35
Figure 2.11: Complete cell merge scenario in VCN 37
Figure 2.12: Partial cell merge scenario in VCN 37
Figure 2.13: Cell separation scenario in VCN 39
Figure 2.14: Integrated scheduler in VCN 40
Figure 2.15: Example of integrated scheduling in VCN 41
Figure 2.16: Traffic shaping for interference mitigation 42
Figure 2.17: Traffic shaping for interference mitigation and antenna diversity 43
Figure 2.18: Traffic shaping for bandwidth stealing 44
Figure 2.19: Multi-cell association 45
Figure 3.1: System Model for applying uplink group scheduling algorithm 50
Figure 3.2: Basic idea of proposed uplink group scheduling algorithm 50
Figure 3.3: Probability to be interfered vs. Number of inner users 57
Figure 3.4: Uplink throughput vs. user position 58
Figure 4.1: Geometrical grouping 69
Figure 4.2: Example user distribution for grouping 69
Figure 4.3: Frame structure for proposed algorithm 70
Figure 4.4: Flow chart of proposed algorithm 72
Figure 4.5: Flow chart of compensation procedure 75
Figure 4.6: Downlink throughput vs. user distance 77
Figure 5.1: Concept of conventional fractional frequency reuse scheme 90
Figure 5.2: Basic idea of proposed algorithm 91
Figure 5.3: Signaling for recognition of neighbor virtual cell networks 91
Figure 5.4: Example of inter-VCN interference map 92
Figure 5.5: Ratio of Intra-VCN interference to Inter-VCN interference vs. Distance between VCNs 95
Figure 5.6: Downlink average throughput vs. Distance between VCNs 97
Figure 6.1: Measurement of the spectrum utilization up to 6 GHz in an urban area 102
Figure 6.2: Multi-cell cognitive radio system 102
Figure 6.3: Cell outage due to spectrum handover 104
Figure 6.4: Path loss vs. distance 104
Figure 6.5: Normalized area of cell coverage vs. SINR degradation 106
Figure 6.6: Operation of conventional spectrum handover 107
Figure 6.7: Concept of proposed spectrum handover scheme 110
Figure 6.8: Operation of proposed spectrum handover for Low to High case 110
Figure 6.9: Operation of proposed spectrum handover for High to Low case 113
Figure 6.10: Overall operation of seamless spectrum handover scheme 114
Figure 6.11: Outage probability vs. original frequency of serving RAU 116
Figure 6.12: Total number of handovers vs. original frequency of serving RAU 118