EETC: to transmit or not to transmit in mobile wireless sensor networks

Mobile wireless sensor networks (MWSNs) have emerged as a promising data gathering paradigm for animal preservation. In MWSNs, it is challenging to efficiently transmit data between resource-constrained mobile sensor nodes and static gateway nodes because of its unreliable and unpredictable nature. Further, elaborate statistics must be known in advance to properly decide when packets should be transmitted, and how many of them to transmit. However, mobility of targets, and instability and intermittency of wireless connections make the system difficult to control. In this paper, we propose EETC, an optimal Energy-Efficient Transmission Control strategy for MWSNs, to deal with the problem based on Lyapunov optimization. EETC comprises two steps: (1) network status collection: collecting, by way of probing messages and acknowledgement messages, information about quality of connectivity and queue backlog; (2) decision making: the mobile sensor node decides on the number of packets that should be transmitted. Our simulation results and analysis demonstrated the performance and robustness of EETC.     

Energy efficiency in wireless sensor networks using sleep mode TDMA scheduling

Power saving is a very critical issue in energy-constrained wireless sensor networks. Many schemes can be found in the literature, which have significant contributions in energy conservation. However, these schemes do not concentrate on reducing the end-to-end packet delay while at the same time retaining the energy-saving capability. Since a long delay can be harmful for either large or small wireless sensor networks, this paper proposes a TDMA-based scheduling scheme that balances energy-saving and end-to-end delay. This balance is achieved by an appropriate scheduling of the wakeup intervals, to allow data packets to be delayed by only one sleep interval for the end-to-end transmission from the sensors to the gateway. The proposed scheme achieves the reduction of the end-to-end delay caused by the sleep mode operation while at the same time it maximizes the energy savings.     

Fuzzy-logic based routing for dense wireless sensor networks

The task of routing data from a source to the sink is a critical issue in ad hoc and wireless sensor networks. In this paper, the use of fuzzy logic to perform role assignment during route establishment and maintenance is proposed. An incremental approach is presented and compared with similar existing routing protocols. Efficient routing approaches provide network load balance to extend network lifetime, efficiency improvements, and data loss avoidance. Experiments show promising results for our proposals and its suitability for operating with dense networks, obtaining quick route creation as well as energy efficiency.     

Energy efficiency of virtual MIMO transmission schemes for cluster-based wireless sensor networks

In this paper,a cluster-based virtual multiple-input multiple-output(MIMO)transmission architecture is proposed for energy-constrained wireless sensor networks.In the proposed architecture,instead of using cluster members as cooperative nodes,multiple cluster heads cooperate to form virtual antenna array so that MIMO transmission can be implemented.According to the MIMO techniques used in this architecture,two different schemes,vertical Bell Laboratories layered space-time(V-BLAST)based cluster heads cooper...     

Energy efficient multi-channel media access control for dense wireless ad hoc and sensor networks

Traditional single-channel MAC protocols for wireless ad hoc and sensor networks favor energy-efficiency over throughput. More recent multi-channel MAC protocols display higher throughput but less energy efficiency. In this article we propose NAMAC, a negotiator-based multi-channel MAC protocol in which specially designated nodes called negotiators maintain the sleeping and communication schedules of nodes within their communication ranges in static wireless ad hoc and sensor networks. Negotiators facilitate the assignation of channels and coordination of communications windows, thus allowing individual nodes to sleep and save energy. We formally define the problem of finding the optimal set of negotiators (i.e., minimizing the number of selected negotiators while maximizing the coverage of the negotiators) and prove that the problem is NP-Complete. Accordingly, we propose a greedy negotiator-election algorithm as part of NAMAC. In addition, we prove the correctness of NAMAC through a rigorous model checking and analyze various characteristics of NAMAC—the throughput of NAMAC, impact of negotiators on network capacity, and storage and computational overhead. Simulation results show that NAMAC, at high network loads, consumes 36 % less energy while providing 25 % more throughput than comparable state-of-art multi-channel MAC protocols for ad hoc networks. Additionally, we propose a lightweight version of NAMAC and show that it outperforms (55 % higher throughput with 36 % less energy) state-of-art MAC protocols for wireless sensor networks.     

Energy conservation in wireless sensor networks: A survey

In the last years, wireless sensor networks (WSNs) have gained increasing attention from both the research community and actual users. As sensor nodes are generally battery-powered devices, the critical aspects to face concern how to reduce the energy consumption of nodes, so that the network lifetime can be extended to reasonable times. In this paper we first break down the energy consumption for the components of a typical sensor node, and discuss the main directions to energy conservation in WSNs. Then, we present a systematic and comprehensive taxonomy of the energy conservation schemes, which are subsequently discussed in depth. Special attention has been devoted to promising solutions which have not yet obtained a wide attention in the literature, such as techniques for energy efficient data acquisition. Finally we conclude the paper with insights for research directions about energy conservation in WSNs.     

Energy constraint clustering algorithms for wireless sensor networks

Using partitioning in sensor networks to create clusters for routing, data management, and for controlling communication has been proven as a way to ensure long range deployment and to deal with sensor network shortcomings such as limited energy and short communication ranges. Choosing a cluster head within each cluster is important because cluster heads use additional energy for their responsibilities and that burden needs to be carefully passed around among nodes in a cluster. Many existing protocols either choose cluster heads randomly or use nodes with the highest remaining energy. We present an Energy Constrained minimum Dominating Set based efficient clustering called ECDS to model the problem of optimally choosing cluster heads with energy constraints. Our proposed randomized distributed algorithm for the constrained dominating set runs in O(log n log Δ) rounds with high probability where Δ is the maximum degree of a node in the graph. We provide an approximation ratio for the ECDS algorithm of expected size 8H_Δ∣OPT∣ and with high probability a size of O(∣OPT∣log n) where n is the number of nodes, H is the harmonic function and OPT means the optimal size. We propose multiple extensions to the distributed algorithm for the energy constrained dominating set. We experimentally show that these extensions perform well in terms of energy usage, node lifetime, and clustering time in comparison and, thus, are very suitable for wireless sensor networks.     

Energy conserving security mechanisms for wireless sensor networks

Since wireless sensor networks are emerging as innovative technologies for realizing a variety of functions through a number of compact sensor nodes, security must be justified and ensured prior to their deployment. An adversary may compromise sensor nodes, forcing them to generate undesired data, and propagation of these data packets through the network results in wasteful energy consumption. We develop a security mechanism to detect energy-consuming useless packets, assuming that a sensor node is able to generate multiple message authentication codes (MAC) using preshared secrets. The forwarding nodes along the path verify the validity of the packet by checking the authenticity of the attached MACs. This mechanism performs well when a malicious node does not have all the cryptographic keys. However, packets, generated by the malicious node having all the keys, would be considered as legitimate, and thus, the forwarding nodes become unable to detect and discard them. To deal with this problem, we devise another mechanism in which each forwarding node is capable of checking such suspicious nodes. We have quantified the security strength through analysis and simulations to show that the proposed mechanisms make the entire network energy conserving.     

EFCon: Energy flow control for sustainable wireless sensor networks

The rapid advances in processor, memory, and radio technology enable the development of small, inexpensive sensor nodes that are capable of sensing, computation, and communication. However, the severe energy constraints of the sensors present major challenges for long-term applications. In order to achieve sustainability, environmental energy harvesting has been demonstrated as a promising approach. In this work, the energy utilization scheme is investigated for wireless sensor networks with energy harvesting nodes. The energy utilization system is divided to three parts: energy harvesting, energy consuming and energy storage. Then the sustainability problem is formulated as an energy flow control problem. An energy flow control system, called EFCon, is proposed to keep the balance between energy supplies and demands. EFCon consists of two phases, energy flow direction control and flow rate control. In the phase of energy flow direction control, the system dynamically switches among four patterns: flood flow, direct flow, compensate flow, and backup flow, according to current environmental energy condition and the residual energy condition. Once the energy flow direction is determined, a corresponding energy flow rate control strategy will be adopted for efficient energy utilization. The EFCon is implemented and validated by a long-term deployment in real testbeds. The experimental results indicate that the EFCon outperforms existing designs.     

Energy balanced data propagation in wireless sensor networks

We study the problem of energy-balanced data propagation in wireless sensor networks. The energy balance property guarantees that the average per sensor energy dissipation is the same for all sensors in the network, during the entire execution of the data propagation protocol. This property is important since it prolongs the network’:s lifetime by avoiding early energy depletion of sensors. We propose a new algorithm that in each step decides whether to propagate data one-hop towards the final destination (the sink), or to send data directly to the sink. This randomized choice balances the (cheap) one-hop transimssions with the direct transimissions to the sink, which are more expensive but “bypass” the sensors lying close to the sink. Note that, in most protocols, these close to the sink sensors tend to be overused and die out early. By a detailed analysis we precisely estimate the probabilities for each propagation choice in order to guarantee energy balance. The needed estimation can easily be performed by current sensors using simple to obtain information. Under some assumptions, we also derive a closed form for these probabilities. The fact (shown by our analysis) that direct (expensive) transmissions to the sink are needed only rarely, shows that our protocol, besides energy-balanced, is also energy efficient. This work has been partially supported by the IST/FET/GC Programme of the European Union under contract numbers IST-2001-33135 (CRESCCO) and 6FP 001907 (DELIS). A perliminary version of the work appeared in WMAN 2004 [11]. Charilaos Efthymiou graduated form the Computer Engineering and Informatics Department (CEID) of the University of Patras, Greece. He received his MSc from the same department with advisor in S. Nikoletseas. He currently continuous his Ph.D studies in CEID with advisor L. Kirousis. His research interest include Probabilistic Techniques and Random Graphs, Randomized Algorithms in Computationally Hard Problems, Stochastic Processes and its Applications to Computer Science. Dr. Sotiris Nikoletseas is currently a Senior Researcher and Managing Director of Research Unit 1 (“Foundations of Computer Science, Relevant Technologies and Applications”) at the Computer Technology Institute (CTI), Patras, Greece and also a Lecturer at the Computer Engineering and Informatics Department of Patras University, Greece. His research interests include Probabilistic Techniques and Random Graphs, Average Case Analysis of Graph Algorithms and Randomized Algorithms, Fundamental Issues in Parallel and Distributed Computing, Approximate Solutions to Computationally Hard Problems. He has published scientific articles in major international conferences and journals and has co-authored (with Paul Spirakis) a book on Probabilistic Techniques. He has been invited speaker in important international scientific events and Universities. He has been a referee for the Theoretical Computer Science (TCS) Journal and important international conferences (ESA, ICALP). He has participated in many EU funded R&D projects (ESPRIT/ALCOM-IT, ESPRIT/GEPPCOM). He currently participates in 6 Fifth Framework projects: ALCOM-FT, ASPIS, UNIVERSAL, EICSTES (IST), ARACNE, AMORE (IMPROVING). Jose Rolim is Full Professor at the Department of Computer Science of the University of Geneva where he leads the Theoretical Computer Science and Sensor Lab (TCSensor Lab). He received his Ph.D. degree in Computer Science at the University of California, Los Angeles working together with Prof. S. Greibach. He has published several articles on the areas of distributed systems, randomization and computational complexity and leads two major projects on the area of Power Aware Computing and Games and Complexity, financed by the Swiss National Science Foundation. Prof. Rolim participates in the editorial board of several journals and conferences and he is the Steering Committee Chair and General Chair of the IEEE Distributed Computing Conference in Sensor Systems.     

无线传感器网络中能量有效的波束成形机制

针对无线传感器网络中单个节点能量和通信距离均受限,以及传统波束成形机制中由于忽略能耗均衡而造成单个节点过早死亡的特点,提出了一种能量有效的波束成形机制。首先分析了节点个数、发射系数、功率受限、相位等因素对网络能耗的影响,给出了对应的设计原则。然后,基于此原则来选择参与发射的节点,并结合节点的剩余能量和相位来调整各自的发射系数。理论分析和仿真结果表明,该机制有效地增加了数据成功传输的次数,均衡了节点间的能耗,延长了网络寿命。     

On the power efficiency of cooperative broadcast in dense wireless networks

A fundamental problem in large scale wireless networks is the energy efficient broadcast of source messages to the whole network. The energy consumption increases as the network size grows, and the optimization of broadcast efficiency becomes more important. In this paper, we study the optimal power allocation problem for cooperative broadcast in dense large-scale networks. In the considered cooperation protocol, a single source initiates the transmission and the rest of the nodes retransmit the source message if they have decoded it reliably. Each node is allocated an-orthogonal channel and the nodes improve their receive signal-to-noise ratio (SNR), hence the energy efficiency, by maximal-ratio combining the receptions of the same packet from different transmitters. We assume that the decoding of the source message is correct as long as the receive SNR exceeds a predetermined threshold. Under the optimal cooperative broadcasting, the transmission order (i.e., the schedule) and the transmission powers of the source and the relays are designed so that every node receives the source message reliably and the total power consumption is minimized. In general, finding the best scheduling in cooperative broadcast is known to be an NP-complete problem. In this paper, we show that the optimal scheduling problem can be solved for dense networks, which we approximate as a continuum of nodes. Under the continuum model, we derive the optimal scheduling and the optimal power density. Furthermore, we propose low-complexity, distributed and power efficient broadcasting schemes and compare their power consumptions with those-of-a traditional noncooperative multihop transmission     

Energy efficiency of large-scale wireless networks: proactive versus reactive networking

An analytical approach to the characterization of energy consumption of large-scale wireless networks is presented. The radio model includes energy consumption of nodes at various operating states. We analyze the total energy consumption of the proactive and the reactive networking strategies, taking into account transmitting, listening, and sleeping energy. Scaling laws with respect to the increase of node density and geographical size are derived. Energy efficiency and overhead at the physical and the network layers are evaluated against message duty cycle, channel fading rate, and node mobility. The crossover point in message duty cycle below which reactive network has assured advantages is obtained. The analysis is then applied to large-scale sensor networks for applications involving data-centric and location-centric queries. The ad hoc sensor network architecture is compared with sensor networks with mobile access points.     

Energy efficient virtual MIMO communication for wireless sensor networks

Virtual multiple input multiple output (MIMO) techniques are used for energy efficient communication in wireless sensor networks. In this paper, we propose energy efficient routing based on virtual MIMO. We investigate virtual MIMO for both fixed and variable rates. We use a cluster based virtual MIMO cognitive model with the aim of changing operational parameters (constellation size) to provide energy efficient communication. We determine the routing path based on the virtual MIMO communication cost to delay the first node death. For larger distances, the simulation results show that virtual MIMO (2×2) based routing is more energy efficient than SISO (single input single output) and other MIMO variations.     

Network configuration for optimal utilization efficiency of wireless sensor networks

This paper addresses the problem of configuring wireless sensor networks (WSNs). Specifically, we seek answers to the following questions: how many sensors should be deployed, what is the optimal sensor placement, and which transmission structure should be employed. The design objective is utilization efficiency defined as network lifetime per unit deployment cost. We propose an optimal approach and an approximation approach with reduced complexity to network configuration. Numerical and simulation results demonstrate the near optimal performance of the approximation approach. We also study the impact of sensing range, channel path loss exponent, sensing power consumption, and event arrival rate on the optimal network configuration.     

无线传感器网络能量均衡分簇路由协议

针对LEACH协议存在的3大问题:簇头选举时未考虑节点剩余能量、频繁成簇造成了大量额外能耗以及欠缺对簇间能耗均衡的考虑,提出了能量有效分簇路由协议(LEACH-improved).该协议中,首轮成簇后网络中簇的分布和数量将保持不变,以后每轮各簇的簇头由上一轮簇头结合节点的能量水平来指定,借鉴泛洪算法的思想,在簇间建立多...     

Energy management in wireless sensor networks with energy-hungry sensors

The energy problem in wireless sensor networks remains one of the major barriers preventing the complete exploitation of this technology. Sensor nodes are typically powered by batteries with a limited lifetime, and even when additional energy can be harvested from the external environment, it remains a limited resource to be consumed judiciously. Efficient energy management is thus a key requirement, with most strategies assuming that data acquisition consumes significantly less energy than data transmission. When this assumption does not hold, effective energy management strategies should include policies for an efficient use of energy-hungry sensors.     

Spatio-temporal sampling rates and energy efficiency in wireless sensor networks

A multi-hop network of wireless sensors can be used to gather spatio-temporal samples of a physical phenomenon and transmit these samples to a processing center. This paper addresses an important issue in the design of such networks: determining the spatio-temporal sampling rate of the network under conditions of minimum energy usage. A new collision-free protocol for gathering sensor data is used to obtain analytical results that characterize the tradeoffs among sensor density, energy usage, throughput, delay, temporal sampling rates and spatial sampling rates in wireless sensor networks. We also show that the lower bound on the delay incurred in gathering data is O(k/sup 2/n) in a clustered network of n sensors with at most k hops between any sensor and its clusterhead (CH). Simulation results on the tradeoff between the achievable spatial sampling rates and the achievable temporal sampling rates when IEEE 802.11 distributed coordination function (DCF) is used as the media access scheme are provided and compared with the analytical results obtained in this paper.     

Energy centroid clustering algorithm to enhance the network lifetime of wireless sensor networks

Multidimensional Systems and Signal Processing - Wireless sensor networks (WSN) consists of dedicated sensors, which monitor and record various physical and environmental conditions like...     

Energy equilibrium based on corona structure for wireless sensor networks

Although multi‐hop routing can reduce communication consumption and extend network scale, energy hole is unavoidable to appear because of the relay nodes being overloaded due to take more tasks. In this paper, we formulate the energy equilibrium problem as an optimal corona division, where data fusion and data slice are both considered in data gathering process. For a circular multi‐hop sensor network with uniform node distribution and constant data reporting, we demonstrate that the energy equilibrium of the whole network is unable to be realized no matter whether data fusion and data slice are adopted. However, the maximum energy equilibrium for a given circular area can be achieved only if the area increases in geometric progression from the outer corona to the neighbor inner corona except for the outermost one. Moreover, we use a zone‐based allocation scheme to guarantee energy equilibrium of intra‐corona. The approach for computing the optimal parameters is presented in terms of maximizing network lifetime. Based on the mathematical model, we propose an energy equilibrium routing based on corona structure (EERCS). Simulating results validate that EERCS can effectively achieve energy equilibrium and prolong the lifetime of network. Copyright © 2010 John Wiley & Sons, Ltd.