International Journal of Distributed Sensor Networks The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Acquisition and Monitoring System for TEG Characterization Tue, 03 Mar 2015 10:03:06 +0000 This paper presents an acquisition system for measuring and characterization of thermoelectric generators (TEGs) for energy harvesting purposes on wireless sensors networks (WSNs). This system can monitor and characterize up to three TEGs simultaneously and is comprised of two main electronic circuits: the first one is composed of 12 input channels being three for reading voltage, three for reading current by making use of instrumentation amplifiers (ACS712), and six thermocouples for signal reading (<400°C). The second electronic circuit consists of a proportional-integral-derivative (PID) controller with two pulse width modulation (PWM) input channels for controlling the heat (thermoresistance) and cooling (controlled cooler) sources, respectively, following a predefined temperature gradient. The TEG measured data for the voltage, current, and temperature can be acquired in real-time with an application written on Delphi language and displayed both through a numeric and graphical display. In order to validate the precision and accuracy two commercial TEG modules (inbC1-127.08HTS) compatible with temperatures up to 200°C without signal degradation were used in series. The functional prototype of the implemented system had a cost under ≈430 USD, making it suitable where a good knowledge of the electrical characteristics of TEGs is of major interest, especially on cogeneration systems. O. H. Ando Jr., C. L. Izidoro, J. M. Gomes, J. H. Correia, J. P. Carmo, and L. Schaeffer Copyright © 2015 O. H. Ando Jr. et al. All rights reserved. Efficient Intelligent Energy Routing Protocol in Wireless Sensor Networks Mon, 02 Mar 2015 13:21:41 +0000 In wireless sensor networks energy is a very important issue because these networks consist of lowpower sensor nodes. This paper proposes a new protocol to reach energy efficiency. The protocol has a different priority in energy efficiency as reducing energy consumption in nodes, prolonging lifetime of the whole network, increasing system reliability, increasing the load balance of the network, and reducing packet delays in the network. In the new protocol is proposed an intelligent routing protocol algorithm. It is based on reinforcement learning techniques. In the first step of the protocol, a new clustering method is applied to the network and the network is established using a connected graph. Then data is transmitted using the -value parameter of reinforcement learning technique. The simulation results show that our protocol has improvement in different parameters such as network lifetime, packet delivery, packet delay, and network balance. Farzad Kiani, Ehsan Amiri, Mazdak Zamani, Touraj Khodadadi, and Azizah Abdul Manaf Copyright © 2015 Farzad Kiani et al. All rights reserved. A Novel Scheduling Algorithm Based on Game Theory and Multicriteria Decision Making in LTE Network Mon, 02 Mar 2015 08:53:03 +0000 Fourth generation wireless networks provide mobile users with high data rate and quality of services, such as Long Term Evolution (LTE), which has been developed by the 3rd Generation Partnership Project (3GPP). However, 3GPP is not a standardized scheduling algorithm to utilize LTE properties in smart grid applications. This paper proposes a two-level scheduling scheme composed of cooperative game theory (bankruptcy and shapely) and Technique for Order Performance by Similarity to Ideal Solution (TOPSIS). The proposed algorithm improves resource allocation for three smart grid applications, namely, voice, video surveillance, and metering data. On the first level, bankruptcy and shapely value algorithm fairly distribute the resources among smart grid applications. On the second level, TOPSIS algorithm allocates the resources among application’s users based on their criteria and the application’s preferences. Moreover, the system’s performance has been evaluated in terms of throughput, delay, and fairness index. The proposed algorithm is compared with existing algorithms, such as proportional fairness, modified largest weighted delay first, and exponential rule schemes. The results show a significant improvement compared to other algorithms. This paper presents a novel technique consisting of both TOPSIS and game theory algorithms to study three smart grid applications. The novel algorithm has proven to be an effective scheduling technique for smart grid applications. Mohammad Nour Hindia, Ahmed Wasif Reza, and Kamarul Ariffin Noordin Copyright © 2015 Mohammad Nour Hindia et al. All rights reserved. E-Cube+ Routing Protocol for Wireless Sensor Networks in the Presence of Network Failures Mon, 02 Mar 2015 08:43:29 +0000 Providing reliable communication represents one of the major barriers to wireless sensor networks. In this paper, we propose a fault-tolerant tableless routing protocol called E-cube+, inspired from e-cube routing protocol, to support intelligent rerouting. A range of fault-tolerant routing properties of E-cube+ (such as loop-freeness, failure recovery guarantees, and bounded latency) have been derived and analyzed. Experiment results also show that E-cube+ is able to route data properly without complicated and energy-intensive routing table lookup processes even when node failures occur. Bo-Chao Cheng, Guo-Tan Liao, Yuan-Fu Chen, and Huan Chen Copyright © 2015 Bo-Chao Cheng et al. All rights reserved. QoS Analysis for a Nonpreemptive Continuous Monitoring and Event-Driven WSN Protocol in Mobile Environments Mon, 02 Mar 2015 08:27:22 +0000 Evolution in wireless sensor networks (WSNs) has allowed the introduction of new applications with increased complexity regarding communication protocols, which have to ensure that certain QoS parameters are met. Specifically, mobile applications require the system to respond in a certain manner in order to adequately track the target object. Hybrid algorithms that perform Continuous Monitoring (CntM) and Event-Driven (ED) duties have proven their ability to enhance performance in different environments, where emergency alarms are required. In this paper, several types of environments are studied using mathematical models and simulations, for evaluating the performance of WALTER, a priority-based nonpreemptive hybrid WSN protocol that aims to reduce delay and packet loss probability in time-critical packets. First, randomly distributed events are considered. This environment can be used to model a wide variety of physical phenomena, for which report delay and energy consumption are analyzed by means of Markov models. Then, mobile-only environments are studied for object tracking purposes. Here, some of the parameters that determine the performance of the system are identified. Finally, an environment containing mobile objects and randomly distributed events is considered. It is shown that by assigning high priority to time-critical packets, report delay is reduced and network performance is enhanced. Israel Leyva-Mayorga, Mario E. Rivero-Angeles, Chadwick Carreto-Arellano, and Vicent Pla Copyright © 2015 Israel Leyva-Mayorga et al. All rights reserved. Systems and Algorithms for Wireless Sensor Networks Based on Animal and Natural Behavior Mon, 02 Mar 2015 08:17:11 +0000 In last decade, there have been many research works about wireless sensor networks (WSNs) focused on improving the network performance as well as increasing the energy efficiency and communications effectiveness. Many of these new mechanisms have been implemented using the behaviors of certain animals, such as ants, bees, or schools of fish. These systems are called bioinspired systems and are used to improve aspects such as handling large-scale networks, provide dynamic nature, and avoid resource constraints, heterogeneity, unattended operation, or robustness, among many others. Therefore, this paper aims to study bioinspired mechanisms in the field of WSN, providing the concepts of these behavior patterns in which these new approaches are based. The paper will explain existing bioinspired systems in WSNs and analyze their impact on WSNs and their evolution. In addition, we will conduct a comprehensive review of recently proposed bioinspired systems, protocols, and mechanisms. Finally, this paper will try to analyze the applications of each bioinspired mechanism as a function of the imitated animal and the deployed application. Although this research area is considered an area with highly theoretical content, we intend to show the great impact that it is generating from the practical perspective. Sandra Sendra, Lorena Parra, Jaime Lloret, and Shafiullah Khan Copyright © 2015 Sandra Sendra et al. All rights reserved. GABs: A Game-Based Secure and Energy Efficient Data Aggregation for Wireless Sensor Networks Mon, 02 Mar 2015 06:51:38 +0000 This paper endeavors to investigate the security and energy issues in wireless sensor networks from prior art such as game theory and various embodiments of methods like public-key cryptography. Due to the needs of interacting with the physical world, thanks to a plethora of innovative applications, the state of the art in wireless sensor networks (WSNs) is focusing on multiple purposes such as monitoring, tracking, and security while relying upon some assumptions about distributed data, whereas these assumptions may not hold in a real scenario. The content herein models homogeneous WSN environment of highly linked nodes, in a theoretical game with synchronized actions, where, in order to transmit their readings securely across the network in some level of hierarchy, using the technique of data aggregation, sensor nodes with communication and computational resources constraint should establish trusted and direct links between their neighbors for the privacy and integrity of their data against faulty nodes, while ensuring energy saving. The study considers the ZigBee known as IEEE 802.15.4 standard for its high trustworthiness and low power consumption in wireless sensor network and compares different topology models. Tristan Daladier Engouang, Yun Liu, and Zhenjiang Zhang Copyright © 2015 Tristan Daladier Engouang et al. All rights reserved. A Secure Storage System for Sensitive Data Protection Based on Mobile Virtualization Sat, 28 Feb 2015 07:53:07 +0000 Recently, the development of smart phones has been reported the number of security vulnerabilities. Although these smart phones have a concept of Sandbox for the security, sensitive personal information has been still exposed by internal data exchange or root privilege acquisition. In this paper, we propose a system framework for secure storage of sensitive data in smartphone. The system is divided into general domain (GD) and secure domain (SD) in mobile device utilizing domain separation technique of virtualization, and SD provides a secure execution environment to protect sensitive data and secure services. In addition, our system introduces the secure functions such as authentication/access control, and encryption/key management and secures filesystem to be run in SD and addresses a detailed secure filesystem as a key function for secure storage. Lastly, the experiments are conducted to measure the performance overhead imposed by security features in SD and by overall system with interdomain communication from GD to SD. These experiment results show suitability of our system and suggest applicability of various secure functions which can be applied in our secure storage system. Su-Wan Park, JaeDeok Lim, and Jeong Nyeo Kim Copyright © 2015 Su-Wan Park et al. All rights reserved. Dynamic Rendezvous Based Routing Algorithm on Sparse Opportunistic Network Environment Thu, 26 Feb 2015 06:10:07 +0000 An opportunistic network is a network where the nodes need to communicate with each other even if existing routes between them may not permanently exist due to the nodes’ random movement. Most routing algorithms employ a paradigm by which a node can keep the receiving messages, carrying the messages with them when moving and then forwarding the messages to the opportunistic meeting nodes when possible. This routing model works well in the networks with high-to-moderate node density in which the opportunity that the moving nodes can meet with each other is rather high. On the other hand, the delivery ratio becomes remarkably low in the sparse network environment especially when there is a strict constraint on message delivery deadline. In this paper, we introduce the novel concept of rendezvous place where the passing nodes can announce, deposit, or pick up their own messages without having to meet the other nodes carrying the desired message. The rendezvous place can be detected automatically and its area’s shape is dynamically changed according to the interaction among nodes. The results from extensive simulations show that our routing algorithm can achieve higher delivery ratio and utilize lower energy consumption than traditional opportunistic routing algorithms especially in sparse network environment. Jiradett Kerdsri and Komwut Wipusitwarakun Copyright © 2015 Jiradett Kerdsri and Komwut Wipusitwarakun. All rights reserved. Initial Validation of Mobile-Structural Health Monitoring Method Using Smartphones Wed, 25 Feb 2015 14:08:43 +0000 The structural health monitoring system has made great development nowadays, especially on bridge structures. Meanwhile, most SHM systems reported were designed, integrated, and installed into large-scale infrastructures by professionals and equipped with expensive sensors, data acquisition devices, data transfer systems, and so forth. And it is impossible to install SHM system for every civilian building. For this status, a kind of new idea for structural health monitoring using smartphone is introduced in this paper. A smartphone, with embedded responding SHM software and inner sensors or external sensors, can be used not only as a single wireless sensor node but also as a mini-SHM system. The method is described in detail, and then the swing test, cable force test in laboratory, and cable force test on an actual bridge based on the iPhone were conducted to validate the proposed method. The experimental results show that Mobile-SHM using smartphone is feasible. The realization of Mobile-SHM method using smartphones may be considered as a milestone in making SHM popular in the lives of people. Yan Yu, Ruicong Han, Xuefeng Zhao, Xingquan Mao, Weitong Hu, Dong Jiao, Mingchu Li, and Jinping Ou Copyright © 2015 Yan Yu et al. All rights reserved. Adaptive Topology Reconfiguration from an Actor Failure in Wireless Sensor-Actor Networks Wed, 25 Feb 2015 10:46:06 +0000 Wireless Sensor-Actor Network (WSAN) usually consists of numerous sensor nodes and fewer actors, and the connectivity of interactors is critical to the whole network. Due to the hash deployed environments and limited energy supply, actor nodes may fail and impact the performance of the whole network. Since the failure of a cut-vertex will disrupt connectivity and divide the topology into disjoint segments, most of the previous researches have already considered this scenario. However, the impact of an abruptly actor’s failure to the network will be far more than that. This paper focuses on the problem of an actor’s failure and gives a more comprehensive view of the faulty actor, that is, not only restricts to the cut-vertex. Length-Aware Topology Reconfiguration Algorithm (LTRA) is proposed on the basis of two vital definitions named as length impact index (LII) and vertex cut set (VCS). LTRA is a hybrid method which selects a best candidate for each actor (if it has) and then initiates in a distributed manner. Main idea of this approach is that candidate will move to replace the faulty one once the failure occurs. In addition, the candidate is selected from one-hop neighbors of each actor. Finally, performance of LTRA is validated by extensive simulation experiments. Shengfeng Zhang, Xiaobei Wu, and Cheng Huang Copyright © 2015 Shengfeng Zhang et al. All rights reserved. pQueue-MAC: An Energy Efficient Hybrid MAC Protocol for Event-Driven Sensor Networks Tue, 24 Feb 2015 06:26:44 +0000 Although a lot of MAC protocols have been proposed to deal with burst traffic in wireless sensor networks, most of them do not optimize the energy efficiency of low and nonperiodic traffic, which actually wastes a lot of energy. To solve the problem, we propose a novel MAC protocol, called pQueue-MAC, to achieve high energy efficiency when no event is detected and still guarantee immediate yet energy efficient data transmission when events are detected. pQueue-MAC uses preamble sampling to check potential communications in low traffic condition. Specifically, through short channel listening, nodes can decide whether there is data destined for them, based on which nodes choose to sleep for energy conservation or keep active for data exchange. Moreover, adaptive channel listening scheme is adopted for dynamic traffic load. When load increases, based on the load information collected from son nodes by piggybacking, cluster heads adaptively allocate TDMA slots and embed the new schedule information into the beacon frame broadcasted to son nodes. We have implemented pQueue-MAC on STM32W108 chips that offer IEEE 802.1.5.4 standard communication and conducted extensive experiments to evaluate its performance. Experimental results show that pQueue-MAC outperforms other typical MAC protocols in hybrid traffic load situation, since it achieves higher energy efficiency and lower transmission latency. Liantao Wu, Shuguo Zhuo, Zhibo Wang, and Zhi Wang Copyright © 2015 Liantao Wu et al. All rights reserved. An Alternating Variable Step-Size Adaptive Long-Range Prediction of LMS Fading Signals Mon, 23 Feb 2015 12:11:03 +0000 We propose a linear alternating variable step-size adaptive long-range prediction (AVSS-ALRP) scheme to predict fading signals which is especially suitable for a versatile two-state land mobile satellite (LMS) channel model at S-band. A three-step design procedure is presented to optimize the prediction performance. Firstly, we establish the Gilbert-Elliot channel model based on first-order Markov chain for satellite communication downlink and take advantage of smoothing average to obtain channel observed values. At a second stage, eigenvalue decomposition method is applied to predict future long-range channel state instead of weighted prediction. Finally, combining variable step-size least mean squares and adaptive long-range prediction, we introduce the VSS-ALRP algorithm to predict LMS channel fading signals in the case of “good” state, and the obtained prediction results would be revised based on the linear prediction of error when shadowing condition is in the “bad” state. Simulation results show that the proposed scheme can not only offer an accurate prediction for long-range channel state and fading signals over the two-state Gilbert-Elliot channel model and greatly enhance the fading signals’ autocorrelation, but also have considerably better performance than long-range prediction (LRP) algorithm from the results of mean square error (MSE) and correlation coefficient. Xi Liao, Rui Xue, Dan-feng Zhao, and Yang Wang Copyright © 2015 Xi Liao et al. All rights reserved. Lifetime Optimization of an Indoor Surveillance Sensor Network Using Adaptive Energy-Efficient Transmission Mon, 23 Feb 2015 10:37:58 +0000 An indoor surveillance system is proposed and carried out in this paper. The surveillance system consists of a home server, omnirobots, and static monitoring nodes. The omnirobots and static monitoring nodes form a surveillance sensor network which comprises several star-like wireless sensor networks. The static monitoring nodes sleep periodically and can be woken up by the pyroelectric infrared sensor. If an abnormal event happens, the static monitoring node will capture images and produce alert messages. An adaptive energy-efficient transmission method is proposed to prolong and balance the lifetime of each static monitoring node. The static monitoring nodes can adjust their transmission power according to the distance to the omnirobots. Meanwhile, the omnirobots can also adjust their positions to extend the lifetime of the surveillance sensor network. Experimental results demonstrate that the transmission power of the static monitoring nodes is minimized sufficiently. A 160 × 120 image can be transmitted within 2.1 s in the surveillance sensor network. The energy consumption of transmitting images without transmission security mechanism reduces by 21%. And it saves 11.7% of energy that an image is transmitted with the lowest transmission power. The surveillance sensor network can be conscious of the node loss and self-recovers timely. Guifang Qiao, Guangming Song, Ying Zhang, Jun Zhang, and Jin Peng Copyright © 2015 Guifang Qiao et al. All rights reserved. Coverage Restoration Method for Wireless Sensor Networks of Distributed PV System Mon, 23 Feb 2015 09:15:48 +0000 Continuous capacity increase of distributed grid-connected photovoltaic (PV) system produces more obvious disturbance on the grid. Monitoring network technology can provide protection for the safety and stability of power grid operation, but sensor nodes of the monitoring network will fall to failure due to environmental interference. According to the performance degradation problem caused by nodes failure in PV monitoring network, particle swarm optimization (PSO) of natural selection based on random weight is proposed in this paper to optimize monitoring performance. This method can restore the monitoring network by arousing redundant nodes. Simulation results show the effectiveness of the proposed algorithm. Zhixin Fu, Zhen Liu, Yue Yuan, Min Zhao, and Qiaomu Li Copyright © 2015 Zhixin Fu et al. All rights reserved. Sensor Node Deployment Based on Electromagnetism-Like Algorithm in Mobile Wireless Sensor Networks Mon, 23 Feb 2015 08:11:01 +0000 The dynamic deployment of sensors in wireless networks significantly affects the performance of the network. However, the efficient application of dynamic deployments which determines the positions of the sensors within the network increases the coverage area of the network. As a result of this, dynamic deployment increases the efficiency of the wireless sensor networks (WSNs). In this paper, dynamic deployment was applied to WSNs which consist of mobile sensors by aiming at increasing the coverage area of the network with electromagnetism-like (EM) algorithm which is a population-based optimization algorithm. A new approach has been improved in calculating the coverage rate of the sensors by using binary detection model so as to carry out the dynamic deployments of sensors and it has been thought to reach realistic results efficiently. Simulation results have shown that the EM algorithm can be preferred in the dynamic deployment of mobile sensors within the wireless networks. Recep Özdağ and Ali Karcı Copyright © 2015 Recep Özdağ and Ali Karcı. All rights reserved. A New Energy Efficient and Reliable MedRadio Scheme Based on Cooperative Communication for Implanted Medical Devices Mon, 23 Feb 2015 07:29:14 +0000 The most significant shortcoming of implanted devices is the battery life. With advanced technology, implanted devices can have the capability to communicate with other health-related devices, but this also means the energy consumption requirement is greater than ever. Less power consumption would extend the duration of the batteries of implanted medical devices. In this paper, an energy efficient and reliable communication service device scheme that does not require any modification to the existing wireless network structure or the implanted devices under consideration is proposed. The scheme is intended to save a target device’s energy necessary for resending communication signals by introducing a neighbor group header node and cooperative (wearable) nodes. The simulation results show that the scheme would result in energy savings of 70 percent with one or two cooperative nodes as compared with the current best approach. Jen-Ming Hsu, Tzu-Chiang Chiang, Yao-Chang Yu, Wei-Guang Teng, and Ting-Wei Hou Copyright © 2015 Jen-Ming Hsu et al. All rights reserved. Appliance Recognition in an OSGi-Based Home Energy Management Gateway Mon, 23 Feb 2015 07:13:21 +0000 The rational use and management of energy is considered a key societal and technological challenge. Home energy management systems (HEMS) have been introduced especially in private home domains to support users in managing and controlling energy consuming devices. Recent studies have shown that informing users about their habits with appliances as well as their usage pattern can help to achieve energy reduction in private households. This requires instruments able to monitor energy consumption at fine grain level and provide this information to consumers. While the most existing approaches for load disaggregation and classification require high-frequency monitoring data, in this paper we propose an approach that exploits low-frequency monitoring data gathered by meters (i.e., Smart Plugs) displaced in the home. Moreover, while the most existing works dealing with appliance classification delegate the classification task to a remote central server, we propose a distributed approach where data processing and appliance recognition are performed locally in the Home Gateway. Our approach is based on a distributed load monitoring system made of Smart Plugs attached to devices and connected to a Home Gateway via the ZigBee protocol. The Home Gateway is based on the OSGi platform, collects data from home devices, and hosts both data processing and user interaction logic. Federica Paganelli, Francesca Paradiso, Stefano Turchi, Antonio Luchetta, Pino Castrogiovanni, and Dino Giuli Copyright © 2015 Federica Paganelli et al. All rights reserved. Evolutionary Game-Based Trust Strategy Adjustment among Nodes in Wireless Sensor Networks Mon, 23 Feb 2015 07:12:06 +0000 Wireless sensor networks (WSNs) provide network services through the cooperation of sensor nodes, while the basis of cooperation depends on the trust relationships among the nodes. In this paper, we construct an evolutionary game-based trust strategy model among the nodes in WSNs, and we subsequently introduce a strategy adjustment mechanism into the process of game evolution to make up for the deficiency that the replicator dynamic model cannot reflect the requirement of individual strategy adjustments. Afterward, we derive theorems and inferences in terms of the evolutionary stable state through dynamic analyses, providing a theoretical basis for WSN trust management. Furthermore, we verify the theorems and inferences with different parameter values, especially the trust incentive and the upper limit of data retransmission after packets are lost, and both of them are closely related to the evolutionary stable state. The experiments demonstrated that, under certain conditions, the involved nodes can finally reach a stable state of the system by constantly adjusting their trust strategy. At the same time, the speed of evolution of our strategy adjustment mechanism in achieving the stable state is much faster than that of the usual replicator dynamic evolution method. Yuanjie Li, Hongyun Xu, Qiying Cao, Zichuan Li, and Shigen Shen Copyright © 2015 Yuanjie Li et al. All rights reserved. Direction of Arrival Estimation Based on the Multistage Nested Wiener Filter Sun, 22 Feb 2015 14:26:27 +0000 A novel direction of arrival (DOA) estimation technique based on data level and order recursive Multistage Nested Wiener Filters (MSNWF) which is used in adaptive beamforming for subarray signal is proposed in this paper. The two subarrays using the same array geometry are used to form a signal whose phase relative to the reference signal is a function of the DOA. The DOA is estimated by calculating the phase-shift between the reference signal and its phase-shifted version. The performance of this DOA estimation technique is significantly improved due to the application of order recursive MSNWF for the rejection of interference signals. The computation of the proposed method is simple, and the number of detectable signal sources could exceed the number of antenna elements. Xiaodong He and Bin Tang Copyright © 2015 Xiaodong He and Bin Tang. All rights reserved. Making It Trustable: Acoustic-Based Signcryption Mutual Authentication for Multiwearable Devices Sun, 22 Feb 2015 12:46:31 +0000 We address the problem of authentication and secure communication between wearable devices. As people rely heavily on such mobile and wearable devices, the need for seamless and secure communication across these spectra of devices becomes increasingly important. In order to provide secure communication, mutually trusted authentication becomes the first line of protection to guard our personal information. We propose an acoustic-based signcryption mutual authentication (ASMA), which is a key-agreement protocol by employing timestamp and owning functions of multiple-times identity authentication, password change, and devices addition and alteration. Through series of experiments verifying the reliability and accuracy, the protocol shows that it can ensure secure data transmission and data sharing for multiwearable devices. Shuhua Zhu, Xiaojie Li, Chunsheng Zhu, Lei Shu, and Wei Sun Copyright © 2015 Shuhua Zhu et al. All rights reserved. Energy Hole Mitigation through Cooperative Transmission in Wireless Sensor Networks Sun, 22 Feb 2015 12:31:42 +0000 The energy balancing capability of cooperative communication is utilized to solve the energy hole problem in wireless sensor networks. We first propose a cooperative transmission strategy, where intermediate nodes participate in two cooperative multi-input single-output (MISO) transmissions with the node at the previous hop and a selected node at the next hop, respectively. Then, we study the optimization problems for power allocation of the cooperative transmission strategy by examining two different approaches: network lifetime maximization (NLM) and energy consumption minimization (ECM). For NLM, the numerical optimal solution is derived and a searching algorithm for suboptimal solution is provided when the optimal solution does not exist. For ECM, a closed-form solution is obtained. Numerical and simulation results show that both the approaches have much longer network lifetime than SISO transmission strategies and other cooperative communication schemes. Moreover, NLM which features energy balancing outperforms ECM which focuses on energy efficiency, in the network lifetime sense. Li Fei, Yi Chen, Qiang Gao, Xiao-Hong Peng, and Qiong Li Copyright © 2015 Li Fei et al. All rights reserved. Robust Localization Algorithm Based on the RSSI Ranging Scope Wed, 18 Feb 2015 06:42:03 +0000 Wireless signal can be easily influenced by the environment in the propagation process. The signal propagation model is the most appropriate model for current indoor environment to ensure the ranging accuracy based on received signal strength indicator (RSSI). In this paper, we propose a robust localization algorithm based on the RSSI ranging scope by which the RSSI ranging error caused by using a fixed parameter in signal propagation model is dramatically eliminated. Our contributions in this paper are twofold. First, the influence of RSSI ranging error on positioning accuracy is well discussed in detail in the scope of the wireless signal propagation model. Second, we develop a robust localization algorithm which creates a one-to-one mapping between the RSSI value and the distance scope based on the value scope of path loss exponent in the signal propagation model. Simulation results indicate that the proposed localization algorithm based on the RSSI ranging scope is robust under different environments, when the real path loss exponent is difficult to measure accurately. Yan Huang, Jianying Zheng, Yang Xiao, and Miao Peng Copyright © 2015 Yan Huang et al. All rights reserved. Modeling the Seismic Impacts on Communication Networks in Smart Grid Tue, 17 Feb 2015 11:30:30 +0000 In Smart Grids, the real-time information measured by distributed sensors is transmitted through communication networks to create an automated energy delivery network. The communication reliability of communication networks in Smart Grids is of great importance, especially under the impact of natural disasters, which are the most common threats to the reliability of power grids. In this paper, the seismic impacts on communication networks in Smart Grids are analyzed, including the modeling of earthquakes, the fragility probability computing of power grids, and the seismic impacts on power line communication (PLC) channel. Based on these analyses, the network capacity is analyzed and the postearthquake network capacity is obtained through the formulations based on an arbitrary network model. The achievable data rates of a practical network are obtained through simulations on a simulated random topology according to practical parameters. To enhance the communication robustness of Smart Grids against earthquakes, a robust routing protocol based on greedy perimeter stateless routing (R-GPSR) is proposed. The simulation results show significant improvements in the reliability and expectation channel capacity of the communication network under the impacts of earthquakes with different magnitudes. Wenhao Wang, Zhi Sun, and Bocheng Zhu Copyright © 2015 Wenhao Wang et al. All rights reserved. Distributed Hybrid Localization Using RSS Threshold Based Connectivity Information and Iterative Location Update Sun, 15 Feb 2015 06:51:47 +0000 Resource constraints of wireless ad hoc and sensor networks prohibit high accuracy range-based localization schemes which require specialized hardware for ranging. On the other hand, cost-effective range-free schemes offer lower accuracy and grant their applicability only to large-scale networks. This paper proposes an efficient distributed hybrid solution which integrates received signal strength (RSS) based ranging and connectivity-based range-free approaches to improve the localization accuracy without any extra ranging hardware and to be adaptable to any network size. First, it configures the connectivity information using available RSS measurements and a predefined RSS threshold. Optimal RSS threshold value that minimizes the error for a particular network to be localized is derived as a function of the total number of nodes and the network size. And then, localization accuracy is further improved by introducing the use of regulated hop-count values. Finally, locations of the nodes are iteratively updated using both connectivity information and RSS-based distance information between the nodes to get more precise localization accuracy. Effectiveness of the proposed scheme is evaluated with both experiments and simulations, and results show that the proposed scheme achieves significant performance improvement over existing schemes. Nyein Aye Maung Maung and Makoto Kawai Copyright © 2015 Nyein Aye Maung Maung and Makoto Kawai. All rights reserved. A Two-Stage Range-Free Localization Method for Wireless Sensor Networks Thu, 12 Feb 2015 07:10:54 +0000 Range-free localization plays an important role in low-cost and large scale wireless sensor networks. Many existing range-free localization methods encounter high localization error, especially for the network with a coverage hole. One reason for high localization error is unreasonable distance estimation method. Another reason is that unknown nodes use the shortest distance which has large cumulative distance error to estimate their positions. In this paper, a two-stage centralized range-free localization algorithm (TCRL) is proposed. In the first stage, we design a novel rational distance estimation method to alleviate the distance estimation error between neighbor nodes based on the connectivity information and geometric features. In the second stage, a novel neighborhood function is derived from the estimated distances between neighbor nodes. Then a new localization strategy is proposed based on greedy idea. Finally, the proposed algorithm is compared with the same type algorithms in two network scenarios, namely, random deployment and random deployment with a coverage hole. The simulation results show that TCRL achieves more accurate and reliable results than most of existing range-free methods in the two network scenarios. Wen Yingyou, Li Zhi, Meng Yinghui, and Zhao Dazhe Copyright © 2015 Wen Yingyou et al. All rights reserved. Multiobjective Optimization for Topology and Coverage Control in Wireless Sensor Networks Thu, 12 Feb 2015 06:40:55 +0000 Coverage, connectivity, and network lifetime are important issues in wireless sensor networks (WSNs). Balancing the energy consumption in the network, reducing the transmission range of nodes, and density control of active nodes are approaches to extend the network lifetime. However, transmission range reduction and smaller number of active nodes can affect the network topology and may cause the network to be disconnected. So, there exist conflicts among lifetime, coverage, and connectivity. In this paper, these conflicting issues are considered and an evolutionary multiobjective optimization approach based on nondominated sorting genetic algorithm-II (NSGA-II) is proposed to optimize them. Simulation results demonstrate that the proposed algorithm can improve the network lifetime and coverage while maintaining the network connectivity. Seyed Mahdi Jameii, Karim Faez, and Mehdi Dehghan Copyright © 2015 Seyed Mahdi Jameii et al. All rights reserved. Enhancing WLAN Performance with Rate Adaptation Considering Hidden Node Effect Wed, 11 Feb 2015 14:13:07 +0000 In IEEE 802.11 WLANs, many rate adaptation studies have proposed rate adaptation schemes to differentiate channel-related loss and collision loss in order to enhance WLAN performance. Most of these studies focus on rate adaptation schemes on the client side when many clients transmit uplink traffic to an access point (AP). However, considering the high proportion of downlink traffic in WLANs, rate adaptation on the AP side has a greater impact on WLAN performance and is more influenced by the downlink traffic on neighboring APs. In addition, considering that many APs are deployed in the real world, some APs use the same channel and are hidden from each other. In this paper, we first analyze the impact of hidden nodes on the rate adaptation scheme. We then propose a new rate adaptation scheme, called Hidden node Effect aware Rate Adaptation (HERA). HERA optimizes the RTS exchange by utilizing RTS transmission success/failure and makes rate decrease decisions based on frame error rate (FER) in order to enhance WLAN performance. We evaluate the performance of HERA through extensive simulation, comparing it with other well-known rate adaptation schemes. Simulation results show that HERA outperforms other rate adaptation schemes by up to 161% in terms of downlink throughput in hidden node environments. Chang-Woo Ahn and Sang-Hwa Chung Copyright © 2015 Chang-Woo Ahn and Sang-Hwa Chung. All rights reserved. Stochastic Polling Interval Adaptation in Duty-Cycled Wireless Sensor Networks Tue, 10 Feb 2015 06:05:09 +0000 In past decades, to achieve energy-efficient communication, many MAC protocols have been proposed for wireless sensor networks (WSNs). Particularly, asynchronous MAC protocol based on low power listening (LPL) scheme is very attractive in duty-cycled WSNs: it reduces the energy wasted by idle listening. In LPL scheme, a sensor node wakes up at every polling interval to sample the channel. If the channel is busy, the sensor node will stay in wake-up mode for receiving the data packet. Otherwise, it goes to sleep and saves power. However, wrong choice of polling interval in LPL scheme causes unexpected energy dissipation. This paper focuses on the polling interval adaptation strategy in LPL scheme with the aim of maximizing energy efficiency, defined as the number of packets delivered per energy unit. We propose a novel polling interval adaptation algorithm based on stochastic learning automata, where a sensor node dynamically adjusts its polling interval. Furthermore, our simulation results demonstrate that the polling interval asymptotically converges to the optimal value. Sungryoul Lee Copyright © 2015 Sungryoul Lee. All rights reserved. Energy Efficient MAC for QoS Traffic in Wireless Body Area Network Tue, 03 Feb 2015 11:37:37 +0000 Lifetimes and latencies of devices in wireless body area networks (WBANs) that monitor the health conditions of patients largely determine their utility under such a setup. It is seen that the medium access method used in the body area network can play a significant role in determining the quality of service such medical devices can provide. IEEE 802.15.6 standard for WBAN includes different types of medium access, namely, CSMA/CA, scheduled, and polling access schemes, or a combination of these techniques. In this paper, medium access methods proposed in IEEE 802.15.6 standard are investigated to assess their effectiveness in meeting the lifetime and quality of service requirements of WBANs. We then propose sleeping schedules for contention and polling access schemes to extend the device lifetime. Simulation studies are done for the investigation using a typical configuration of the medical devices found in a hospital setting. It is found that priority polling technique can give a combination of high lifetime and a low latency. Various other results offer important insights into the behaviour of these techniques under WBAN conditions. Anil K. Jacob and Lillykutty Jacob Copyright © 2015 Anil K. Jacob and Lillykutty Jacob. All rights reserved.