Wake-up receivers for wireless sensor networks: benefits and challenges

For successful data delivery, the destination nodes should be listening to the medium to receive data when the sender node starts data communication. To achieve this synchronization, there are different rendezvous schemes, among which the most energy-efficient is utilizing wakeup receivers. Current hardware technologies of wake-up receivers enable us to evaluate them as a promising solution for wireless sensor networks. In this article the benefits achieved with wake-up receivers are investigated along with the challenges observed. In addition, an overview of state-of-the-art hardware and networking protocol proposals is presented. As wake-up receivers offer new opportunities, new potential application areas are also presented and discussed.Peer ReviewedPostprint (published version

Energy-aware Scheduling of Surveillance in Wireless Multimedia Sensor Networks

Wireless sensor networks involve a large number of sensor nodes with limited energy supply, which impacts the behavior of their application. In wireless multimedia sensor networks, sensor nodes are equipped with audio and visual information collection modules. Multimedia contents are ubiquitously retrieved in surveillance applications. To solve the energy problems during target surveillance with wireless multimedia sensor networks, an energy-aware sensor scheduling method is proposed in this paper. Sensor nodes which acquire acoustic signals are deployed randomly in the sensing fields. Target localization is based on the signal energy feature provided by multiple sensor nodes, employing particle swarm optimization (PSO). During the target surveillance procedure, sensor nodes are adaptively grouped in a totally distributed manner. Specially, the target motion information is extracted by a forecasting algorithm, which is based on the hidden Markov model (HMM). The forecasting results are utilized to awaken sensor node in the vicinity of future target position. According to the two properties, signal energy feature and residual energy, the sensor nodes decide whether to participate in target detection separately with a fuzzy control approach. Meanwhile, the local routing scheme of data transmission towards the observer is discussed. Experimental results demonstrate the efficiency of energy-aware scheduling of surveillance in wireless multimedia sensor network, where significant energy saving is achieved by the sensor awakening approach and data transmission paths are calculated with low computational complexity

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

Movements assessment and analysis for IMU based wearable networks

Movements assessment and analysis based on Inertial Measurement Units (IMUs) is becoming a common feature for many kinds of applications, such as industrial, videogames, sports and medical. The approach predominantly used is the processing of sensors output as a waveform in which a pattern can be recognized or the initial and the final positions of the movement detected. Not only does this approach lack in precision of the measurement but also yields results that are not readily understandable, especially visually. On the other hand, visual interaction alone can be restricted by the difficulties in capturing some body positions and evaluating them. Using six degrees of freedom IMUs and similarly to techniques that rely on optical devices, but obviously without employing them, we tried to view the sensors output as a representation of the movement in space, in order to obtain the actual trajectory of the whole movement. We also gave a suitable representation of the movements and efficient analysis and comparison techniques for evaluating them. In this thesis we will describe how our approach was realized, the experiments performed and the solutions proposed, even comparing them with other solutions proposed in literature. ----------------------------------------------------------------------------------------------------- La valutazione e l’analisi di movimenti basata su dispositivi di misurazione inerziale (IMUs) sta diventando caratteristica comune in molti tipi di impieghi, come quelli industriali, video-ludici, sportivi e medici. L’approccio maggiormente utilizzato è il processamento dell’output dei sensori visto come una forma d’onda nella quale riconoscere un pattern o individuare le pose iniziali e finali del movimento. Questo approccio non solo è carente nella precisione della misurazione ma fornisce risultati di difficile lettura e comprensione, specialmente dal punto di vista visivo. D’altro canto la sola interazione visuale può essere limitata dalla difficoltà nel rilevare alcune posizioni del corpo e quindi valutarle. Utilizzando IMUs a sei gradi di libertà e in maniera simile alle tecniche basate su dispositivi ottici, ma ovviamente senza impiegarli, abbiamo cercato di interpretate l’output dei sensori come rappresentazione del movimento nello spazio, al fine di ottenere la reale traiettoria dell’intero movimento. Inoltre, abbiamo fornito un’adeguata rappresentazione dei movimenti e efficienti tecniche per la loro analisi e il loro confronto. In questa tesi descriveremo come il nostro approccio è stato realizzato, gli esperimenti condotti e le soluzioni proposte, effettuando anche dei confronti con altre soluzioni proposte in letteratura