무선 센서 네트워크에서 에너지 절감을 위한 계층 토폴로지 제어

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 신현식.Simple wireless sensor networks (WSNs) usually have a flat topology and transmit data using a flooding scheme of which there are several variants. However, these can cause the broadcast storming problem, reducing the efficiency and reliability of the WSN. Due to these problems, most WSNs have a cluster or tree structurebut this causes an imbalance of residual energy between nodes, which gets worse over time as nodes become defunct and replacements are inserted. Moreover, a defunct cluster head leads to a sharp drop of network connectivity. Therefore, an efficient way to improve the energy imbalance and the network connectivity is needed. In this thesis, we propose a hierarchical topology control scheme, in which each node periodically selects its own layer accommodating itself with different levels of residual energy and the amount of data to transfer, in order to balance the energy level and to increase the network connectivity. Simulations show that this scheme can balance node energy levels, and thus extend network lifetime. We also introduce a hierarchical topology control scheme for WSNs, which contains both energy-harvesting nodes and battery-powered nodes, in order to extend the lifetime of battery-powered nodes and to increase the network connectivity. In such a WSN, the energy harvesting nodes are also arranged in layers like the battery-powered nodes depending on their expected level of residual energy. This scheme is shown to increase the lifetime of battery-powered nodes preferentially by locating energy-harvesting nodes on the higher layers.Abstract i Contents iii List of Figures vi List of Tables ix 1 Introduction 1 1.1 Motivation 1 1.2 Research Contributions 4 1.3 Organization of This Thesis 5 2 Background and Related Work 7 2.1 Wireless Sensor Networks 7 2.1.1 Characteristics of WSNs 8 2.1.2 WSN Applications 10 2.1.3 Topology Control for WSNs 18 2.1.4 WSN using multiple sink nodes 22 2.2 Energy-harvesting WSNs 22 2.2.1 Hierarchical Topology Control for WSNs with Energy-Harvesting Nodes 23 3 Multi-layer Topology Control for Long-term Wireless Sensor Networks 25 3.1 Layer-Based Topology Control 25 3.1.1 Proposed Scheme 25 3.1.2 The Layering Algorithm Design 26 3.2 Layer Determination 28 3.2.1 TCI message 30 3.2.2 How a node selects its layer 30 3.3 Experimental Results 32 3.3.1 Simulation Environment 33 3.3.2 Simulation Results 35 4 Energy-aware Hierarchical Topology Control for Wireless Sensor Networks with Energy-Harvesting Nodes 41 4.1 Layer-based Topology Control with Energy-harvesting Sensor Nodes 41 4.1.1 Review of Layer-based Topology Control for Long-term WSNs with Battery-powered Nodes 42 4.1.2 The Layer Determination Algorithm 43 4.1.3 Introducing Energy-Harvesting Nodes to a Layered Topology 56 4.2 Experimental Results 58 4.2.1 Simulation Environment 58 4.2.2 Simulation Results 59 5 Conclusion 73 5.1 Summary 73 5.2 Future Research Directions 75 요약 92Docto