Title Page
Abstract
Contents
Acronyms 18
Chapter 1. Introduction 19
1.1. Motivations 19
1.2. Contributions of the Dissertation 24
1.3. Outline of the Dissertation 25
Chapter 2. Background and Literature Review 27
2.1. Cognitive Radio 28
2.2. Spectrum Sensing: Single Node Case 30
2.2.1. Matched Filter 32
2.2.2. Energy Detector 32
2.2.3. Cyclostationary Feature Detection 35
2.2.4. Compressed Sensing 37
2.3. Cooperative Spectrum Sensing 38
2.3.1. Common Reporting Channel 41
2.3.2. Jointly Optimization of Sensing and Transmission 43
2.4. Cooperative Communications 45
Chapter 3. Cooperative Spectrum Sensing with Node Selection 47
3.1. Introduction 48
3.2. System Model and Motivations 51
3.2.1. Spectrum Sensing without Cooperation 52
3.2.2. Low RPSS Nodes 53
3.3. Cooperative Spectrum Sensing with Node Selection 54
3.3.1. Secondary Node Selection Probability 54
3.3.2. Adaptive Node Selection Scheme 55
3.3.3. Selection Probability Maintenance 58
3.4. Performance Analysis 61
3.4.1. Cooperative Detection Performance 61
3.4.2. An Analysis of Selection Probability 63
3.5. Numerical Results 65
3.5.1. Node Selection Performance 68
3.5.2. Detection Performance 70
3.6. Summary 71
Chapter 4. Conservative Cooperative Spectrum Sensing without Common Reporting Channel 74
4.1. Introduction 75
4.2. System Model 78
4.3. Conservative Cooperative Spectrum Sensing without Common Reporting Channel 79
4.3.1. Local Spectrum Sensing 79
4.3.2. Conservative Cooperative Strategy 81
4.4. Analysis of Reporting Reliability 83
4.5. Analysis of Interference to PUs 87
4.6. Numerical Results 89
4.6.1. ROC performance 90
4.6.2. Interference performance 91
4.7. Summary 94
Chapter 5. Bandwidth-Efficient Transmission Scheme without Common Reporting Channel 97
5.1. Introduction 98
5.2. System Model 103
5.2.1. Frame structure of Sensing-Transmission 103
5.2.2. Channel Model 106
5.3. Conservative Sensing and Bandwidth-Efficient Transmission Scheme 107
5.3.1. Conservative Cooperative Spectrum Sensing 108
5.3.2. Reporting Outage Probability 109
5.3.3. Bandwidth-Efficient Transmission 110
5.4. Performance Analysis of Spectrum Sensing 112
5.5. Sensing Bandwidth Efficiency Tradeoff 113
5.5.1. Expected Bandwidth Efficiency 114
5.5.2. Problem Formulation 114
5.5.3. Optimal Sensing Time 116
5.6. Numerical Results 117
5.7. Summary 125
Chapter 6. Conclusions and Future Work 127
6.1. Conclusions 127
6.2. Future Work 128
References 129
Figure 1.1: United States Frequency Allocations Chart 2011. 21
Figure 1.2: Measurement of 0-6 GHz spectrum utilization at BWRC. 22
Figure 2.1: Structure of centralized cooperative spectrum sensing. 38
Figure 3.1: Cooperative spectrum sensing in CR networks. 53
Figure 3.2: Frame structure of cooperative spectrum sensing. 54
Figure 3.3: Flow chart of cooperative sensing with adaptive node selection. 55
Figure 3.4: Structure of cooperative sensing with adaptive node selection. 56
Figure 3.5: The average number of selected nodes vs. the percentage of low PRSS nodes for different selection weights α with N = 10, Pf = 0.01, λ0 = 15.4 dB, Ph₁ = 1,...(이미지참조) 66
Figure 3.6: The average number of selected nodes vs. the percentage of low PRSS nodes for different selection weights α with N = 10, Pf = 0.01, λ0 = 15.4 dB, Ph₁ = 1,...(이미지참조) 66
Figure 3.7: The average number of selected nodes vs. the percentage of low-PRSS nodes for different selection thresholds △ with N = 10, M = 10, Pf = 0.01, λ0 = 15.4...(이미지참조) 67
Figure 3.8: The average number of selected nodes vs. the percentage of low-PRSS nodes for different selection thresholds △ with N = 10, M = 10, Pf = 0.01, λ0 = 15.4...(이미지참조) 68
Figure 3.9: The cooperative detection probability vs. the percentage of low-PRSS nodes for different selection weights α with N = 10, M = 10, Pf = 0.01, λ0 = 15.4...(이미지참조) 72
Figure 3.10: The cooperative detection probability vs. the percentage of low-PRSS nodes for different selection weights α with N = 10, M = 10, Pf = 0.01, λ0 = 15.4...(이미지참조) 72
Figure 3.11: The cooperative detection probability vs. the percentage of low-PRSS nodes for different selection thresholds △ with N = 10, M = 10, Pf = 0.01, λ0 = 15.4...(이미지참조) 73
Figure 3.12: The cooperative detection probability vs. the percentage of low-PRSS nodes for different selection thresholds △ with N = 10, M = 10, Pf = 0.01, λ0 = 15.4...(이미지참조) 73
Figure 4.1: A two-node cognitive radio network. 78
Figure 4.2: Frame structure of cooperative spectrum sensing. 81
Figure 4.3: ROC performance with τ = 10 ms, α = 1 ms, T = 50 ms, fs = 5 kHz, M = 50, σc² = 1, and γi = -15 dB.(이미지참조) 91
Figure 4.4: ROC performance with τ = 10 ms, α = 1 ms, T = 50 ms, fs = 5 kHz, M = 50, σc² = 1, and γi = -10 dB.(이미지참조) 92
Figure 4.5: ROC performance with τ = 10 ms, α = 1 ms, T = 50 ms, fs = 5 kHz, M = 50, σc² = 1, and γi = -5 dB.(이미지참조) 92
Figure 4.6: The Local SNR versus the total interference probability with τ = 10 ms, α = 1 ms, T = 50 ms, fs = 5 kHz, M = 50, σc² = 1, and γc = 0 dB(이미지참조) 93
Figure 4.7: The Local SNR versus the total interference probability with τ = 10 ms, α = 1 ms, T = 50 ms, fs = 5 kHz, M = 50, σc² = 1, and γc = 5 dB(이미지참조) 94
Figure 4.8: The Local SNR versus the total interference probability with τ = 10 ms, α = 1 ms, T = 50 ms, fs = 5 kHz, M = 50, σc² = 1, and γc = 10 dB(이미지참조) 95
Figure 4.9: The Local SNR versus the total interference probability with τ = 10 ms, α = 1 ms, T = 50 ms, fs = 5 kHz, M = 50, σc² = 1, and γc = 15 dB(이미지참조) 96
Figure 5.1: A simplified three-node cognitive radio network. 104
Figure 5.2: Frame structure of sensing and transmission for CR network. 106
Figure 5.3: Structureof reporting and broadcasting. 107
Figure 5.4: CR network topology: case dij = dSD, that is, the distance between secondary nodes are equal.(이미지참조) 118
Figure 5.5: CR network topology: case dSR = dRD = ½dSD, that is, the relay is located in the middle of the source and the destination.(이미지참조) 119
Figure 5.6: Bandwidth efficiency versus sensing time duration for different sensing constraints and transmission power with β = 3, fs = 100 kHz, T = 50 ms, α = 1 ms,...(이미지참조) 120
Figure 5.7: Bandwidth efficiency versus sensing time duration for different sensing constraints and transmission power with β = 3, fs = 100 kHz, T = 50 ms, α = 1 ms,...(이미지참조) 120
Figure 5.8: Bandwidth efficiency versus sensing time duration for different sensing constraints and transmission power with β = 3, fs = 100 kHz, T = 50 ms, α = 1 ms,...(이미지참조) 121
Figure 5.9: Bandwidth efficiency versus sensing time duration for different sensing constraints and transmission power with β = 3, fs = 100 kHz, T = 50 ms, α = 1 ms,...(이미지참조) 122
Figure 5.10: CR network topology: A relay node is located on the straight line joining the source and destination. 123
Figure 5.11: Optimal sensing time versus source-relay distance for different sensing constraints with β = 3, fs = 100 kHz, T = 50 ms, α = 1 ms, γP = -5 dB, γS = 0 dB,...(이미지참조) 124
Figure 5.12: Bandwidth efficiency versus source-relay distance for different sensing constraints with β = 3, fs = 100 kHz, T = 50 ms, α = 1 ms, γP = -5 dB, γS = 0 dB,...(이미지참조) 124