Departament de Teoria del Senyal i Comunicacions UNIVERSITAT POLITÈCNICA DE CATALUNYA Ph.D. Thesis ADAPTIVE RADIO RESOURCE MANAGEMENT FOR OFDMA-BASED MACRO- AND FEMTOCELL NETWORKS Thesis by Emanuel Bezerra Rodrigues In Partial Fulfillment of the Requirements for the Degree of Doctor from the Universitat Polit`ecnica de Catalunya Advisor: Prof. Fernando Casadevall Palacio Departament de Teoria del Senyal i Comunicacions (TSC) Universitat Polit`ecnica de Catalunya (UPC) Barcelona, May 28, 2011 With love to my wife Gladia, and to our little baby. Abstract User and cellular operator requirements and expectations have been continuously evolving, and con- sequently, advanced radio access technologies have emerged. The International Mobile Telecommu- nications - Advanced (IMT-Advanced) specifications for mobile broadband Fourth Generation (4G) networks state, among other requirements, that enhanced peak data rates of 100 Mbps and 1 Gbps for high and low mobility should be provided. In order to achieve this challenging performance, Or- thogonal Frequency Division Multiple Access (OFDMA) has been chosen as the access technology, and femtocells have been considered for improving indoor coverage. In order to fully explore the flexibility of these technologies and use the scarce radio resources in the most efficient way possible, intelligent and adaptive Radio Resource Management (RRM) techniques are crucial. There are many open RRM problems in wireless networks in general, and OFDMA-based cellular systems in particular. One of such problems is the fundamental trade-off that exists between efficiency in the resource usage and fairness in the resource distribution among network players. Several opportunistic RRM algorithms, which dynamically allocate the resources to the network players that present the highest efficiency indicator with regard to these resources, have been proposed to maximize the efficiency in the resource usage. The trade-off between efficiency and fairness appears when the resources have different efficiency indicators to different network players (multi-user or multi-cell diversity). The use of opportunistic resource allocation to explore these diversities causes unfair situations in the resource distribution. On the other hand, schemes that provide absolute fairness deal with the worst case scenario, penalizing players with better condition and reducing the system capacity. In this thesis, several RRM policies and techniques are proposed to balance this compromise in macrocell and femtocell networks. In the particular case of macrocell systems, we propound a new network management paradigm based on the control of a cell fairness index in scenarios with Non-Real Time (NRT) or Real Time (RT) services. Two fairness control approaches are studied: instantaneous (short-term) control by means of generalized fairness/rate adaptive RRM techniques and average (mid-term) control using utility-based frameworks. For femtocell networks, a novel interference avoidance technique able to balance the trade-off between spectral efficiency in the femtocell tier and fairness among the Femtocell Access Points (FAPs) is formulated. This RRM v strategy is based on a high-level, mid/long-term frequency planning that takes into account the topology of groups of neighboring FAPs. The RRM techniques considered in this thesis are evaluated by means of extensive system-level and/or numerical simulations. Regarding the macrocell scenario, it is shown that the proposed adaptive RRM techniques are valuable tools for the mobile operators, because they are general- izations of well-known classic strategies found in the literature and they can effectively guarantee different fairness levels in the system and control the trade-off between efficiency and fairness. Fur- thermore, it is concluded that the utility-based strategies that perform an average fairness control can provide performance results as good as the fairness/rate adaptive techniques, which are based on instantaneous optimization, using less computational resources. Finally, it is demonstrated that the proposed interference avoidance technique for femtocell networks can guarantee a seamless co- existence between neighboring FAPs in any interference topology. Furthermore, this technique can be implemented in both centralized and distributed network architectures and generates very low signaling overhead. vi Acknowledgements Firstly and above all, I would like to thank God for giving me health and all the internal resources needed for the fulfilment of this doctoral endeavor. All my gratitude to my beloved wife Gladia Lima, who has always supported and encouraged me. Due to her love and patience, this dream has come true. Many thanks to my family, specially my mom M´ercia Bezerra, who raised me with love and helped me to form the human being I am now. I would like to thank very much my advisor, Prof. Fernando Casadevall, for receiving me with open arms in Barcelona, and for his commitment and generosity in sharing his wisdom. He has been an inspiration in both personal and professional aspects. My acknowledgments to all the professors and employees of the Department of Signal Theory and Communications (TSC), specially Prof. Jordi P´erez-Romero, for the rich technical discussions and friendship. I would also like to thank the Network of Excellence in Wireless COMmunications++ (NEW- COM++), which has been a very important forum of academic partnership. Many thanks to Prof. Marco Moretti and Pawel Sroka, who have collaborated with this research. I am very grateful for the financial support of the Brazilian government by means of the schol- arship of the Improvement Co-ordination of Superior Level People (CAPES). Many thanks to Prof. Rodrigo Cavalcanti, Prof. Jo˜ao C´esar Mota and Gunnar Bark for their recommendation letters. I am also specially grateful for the guidance of Prof. Rodrigo Cavalcanti, who has closely followed the progress of my doctoral work. I would like to acknowledge the work of the anonymous reviewers of this thesis and the papers submitted to different journals, magazines and conferences. Their valuable comments helped to improve the quality of this work. Last, but not least, many thanks to the friends I have known here in Barcelona, specially my colleagues at the Mobile Communications Research Group (GRCM), for their help and friendship. vii Contents List of Figures xiii List of Tables xvii List of Algorithms xix List of Abbreviations xxi List of Symbols xxv 1. Introduction 1 1.1. BackgroundandMotivation . .......... 1 1.2. ObjectivesoftheThesis. ........... 5 1.3. ResearchMethodology. .......... 6 1.4. ContributionsoftheThesis. ............ 7 1.5. ListofPublications ............................. .......... 8 1.6. ResearchStructureoftheThesis . ............ 9 2. Radio Resource Management for OFDMA Systems 13 2.1. Introduction................................... ......... 13 2.2. Orthogonal Frequency Division Multiple Access . ................ 14 2.3. Radio Resource Management Techniques for OFDMA Systems ............. 17 2.4. OptimizationTools.............................. .......... 19 2.5. SystemArchitecture ............................. .......... 22 2.6. RRM for the Downlink of OFDMA Macrocell Networks . ........... 23 2.7. RRM for the Downlink of OFDMA Femtocell Networks . ........... 28 2.8. Fundamental Trade-Off between Efficiency and Fairness . ............... 32 3. Fairness/Rate Adaptive Resource Allocation for Macrocell Networks 37 3.1. Introduction................................... ......... 37 3.2. Management of Trade-Off between Efficiency and Fairness Using Rate Adaptive Optimization ....................................... .... 38 3.3. Fairness/Rate Adaptive Resource Allocation for OFDMA Systems ........... 41 3.3.1. Fairness-Based Sum Rate Maximization (FSRM) . ........... 43 3.3.2. Fairness-Based Sum Rate Maximization with Proportional Rate Constraints (FSRM-P) ........................................ 43 ix Contents 3.3.3. Fairness-Based Max-Min Rate with Proportional Rate Constraints (FMMR-P) 44 3.4. Proposed Resource Allocation Techniques . ............... 45 3.4.1. Initial Dynamic Sub-carrier Assignment . ............. 47 3.4.2. Fairness-Based Dynamic Sub-carrier Assignment . .............. 47 3.4.3. Fairness-Based Adaptive Power Allocation . ............. 51 3.4.4. Particularization of the Fairness/Rate Adaptive Policies............. 55 3.5. SimulationResults .............................. .......... 58 3.5.1. Preliminary Analysis of the Classic Rate Adaptive Techniques . 60 3.5.2. Convergence Analysis of the Fairness/Rate Adaptive Techniques . 61 3.5.3. Rate Distribution and Rate Proportionality Analyses............... 63 3.5.4. FairnessAnalysis ............................. ....... 65 3.5.5. EfficiencyAnalysis ............................. ...... 68 3.5.6. SatisfactionAnalysis . ......... 72 3.5.7. CPUTimeAnalysis.............................. ..... 74 3.6. Conclusions .................................... ........ 76 4. Utility-Based Resource Allocation for Macrocell Networks 79 4.1. Introduction................................... ......... 79 4.2. Management of Trade-Off between Efficiency and Fairness Using Utility Theory . 80 4.3. Utility-Based Resource Allocation for OFDMA Systems . ................ 83 4.3.1. Non-RealTimeServices . ....... 84 4.3.2. RealTimeServices ............................. ...... 88 4.4. Adaptive Resource Allocation Frameworks . .............. 92 4.4.1. Utility-Based Alpha-Rule for Non-Real Time Services .............. 92 4.4.2. Utility-Based Beta-Rule for Real