||Joint Modulation Order Selection and Power Allocation for User-Centric Li-Fi Networks
||Institute of Computer Science and Information Engineering
Joint Modulation Order Selection and Power Allocation
Multi-Choice Knapsack Problem
In traditional Light-Fidelity (Li-Fi) attocell networks, the dense structure of Li-Fi access points (APs) leads to severe inter-cell interference (ICI). User-centric (UC) networks mitigate the inter-cell interference, which dynamically reform amorphous cells as the user mobility varies in time. In this thesis, we propose a new user-centric clustering and joint modulation order selection algorithm respectively with the objective of maximizing energy efficiency (EE).
In previous studies, clustering algorithms usually only aim at minimizing the distance from the centroid of the cluster to each user within the cell. Since inter-cell interference is the main challenge in Li-Fi networks, separating each cells as far as possible is also important. Therefore, in this thesis, we propose a new clustering algorithm that also considers the distance among each constructed cells. On the other hand, we leverage multi-choice knapsack problem for joint modulation order selection and power allocation. Furthermore, different from previous studies, instead of using worst-case estimated interference, a tighter-upper-bounded estimated interference is proposed, yielding better energy efficiency as the power consumption is further reduced. Using our proposed user-centric clustering algorithm, it can achieve up to approximated 87.5 % improvement in terms of energy efficiency.
List of Figures IX
List of Tables XI
Chapter 1 Introduction 1
Chapter 2 Background 2
2.1 Li-Fi 2
2.2 Energy Efficiency 3
2.3 User-centric Networks 3
Chapter 3 Related Work 5
3.1 User-Centric Clustering 5
3.2 UE Formation 5
3.3 AP Formation 6
3.4 AP Switching 6
3.5 Joint Modulation Order Selection and Power Allocation 6
3.6 Interference Estimation 7
Chapter 4 System Model 8
4.1 Lambertian Model 8
4.2 Asymmetrically Clipped Optical Orthogonal Frequency-Division Multiplexing 8
4.3 Transmission Technique 9
4.3.1 Combined Transmission 9
4.3.2 Vectored Transmission 9
4.3.3 Signal-to-Interference-plus-Noise Ratio 10
Chapter 5 Proposed Scheme 11
5.1 Notation 11
5.2 Problem Formulation 12
5.3 Contribution 13
5.4 User-Centric Clustering 13
5.4.1 UE Formation 14
5.4.2 AP Formation 14
5.4.3 AP Switching 15
5.5 Joint Modulation Order Selection and Power Allocation 16
5.5.1 VT-Aided Cells 16
5.5.2 CT-Aided Cells 19
5.5.3 Interference Estimation 20
5.5.4 Conclusion 22
5.6 Complexity Analysis 23
Chapter 6 Performance Evaluation 24
6.1 Parameter Setting 24
6.2 Performance Metrics 26
6.3.1 Comparison between different UE formation methods 26
6.3.2 Comparison among different AP formation methods and different AP switching methods 29
6.3.3 Comparison between different interference estimation 33
6.3.4 Comparison among different dMAX 35
Chapter 7 Conclusion 38
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