International Journal of Distributed Sensor Networks http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Security Analysis in Wireless Sensor Networks Thu, 23 Oct 2014 06:18:02 +0000 http://www.hindawi.com/journals/ijdsn/2014/303501/ In recent years, wireless sensor network (WSN) is employed in many application areas such as monitoring, tracking, and controlling. For many applications of WSN, security is an important requirement. However, security solutions in WSN differ from traditional networks due to resource limitation and computational constraints. This paper analyzes security solutions: TinySec, IEEE 802.15.4, SPINS, MiniSEC, LSec, LLSP, LISA, and LISP in WSN. The paper also presents characteristics, security requirements, attacks, encryption algorithms, and operation modes. This paper is considered to be useful for security designers in WSNs. Murat Dener Copyright © 2014 Murat Dener. All rights reserved. Robust and Energy-Efficient Data Gathering in Wireless Sensor Network Wed, 22 Oct 2014 07:22:39 +0000 http://www.hindawi.com/journals/ijdsn/2014/960242/ Robustness and energy efficiency are critical for sensor information system, in which an abundance of wireless sensor nodes collects useful data from the deployed field. The chain-based protocols (like PEGASIS (Lindsey and Raghavendra, 2002)) are elegant solutions where sensor node has high energy efficiency. Unfortunately, if one node in the chain is failed due to some reasons such as energy exhaust, then the information cannot be forwarded to the sink. To improve system robustness and balance the energy consumption, this paper proposes a robust and energy-efficient data gathering (REEDG) approach, which is an improvement over the chain-based and grid-based network structures, in sensor information collecting system. In REEDG, data gathering is executed by a data transmitting chain which is composed by a series of virtual grids. Each grid communicates only with its neighbor grid and takes turns transmitting the information to the base station. Furthermore, an adaptive scheduling scheme is proposed to trade off energy consumption on each node and data forwarding delay. Experimental results show that, when compared with state-of-the-art approaches, REEDG achieves network lifetime extension of at least 13% as measured in terms of 20% dead nodes and improves the data transmission ratio at lowest 24% as 20% nodes fail. Juan Feng, Baowang Lian, and Hongwei Zhao Copyright © 2014 Juan Feng et al. All rights reserved. A Wi-Fi Cluster Based Wireless Sensor Network Application and Deployment for Wildfire Detection Mon, 20 Oct 2014 11:27:56 +0000 http://www.hindawi.com/journals/ijdsn/2014/651957/ We introduce the wireless sensor network (WSN) data harvesting application we developed for wildfire detection and the experiments we have performed. The sensor nodes are equipped with temperature and relative humidity sensors. They are organized into clusters and they communicate with the cluster heads using 802.15.4/ZigBee wireless links. The cluster heads report the harvested data to the control center using 802.11/Wi-Fi links. We introduce the hardware and the software architecture of our deployment near Rhodiapolis, an ancient city raising on the outskirts of Kumluca county of Antalya, Turkey. We detail our technical insights into the deployment based on the real-world data collected from the site. We also propose a temperature-based fire detection algorithm and we evaluate its performance by performing experiments in our deployment site and also in our university. We observed that our WSN application can reliably report temperature data to the center quickly and our algorithms can detect fire events in an acceptable time frame with no or very few false positives. Alper Rifat Ulucinar, Ibrahim Korpeoglu, and A. Enis Cetin Copyright © 2014 Alper Rifat Ulucinar et al. All rights reserved. A Statistical Analysis Based Probabilistic Routing for Resource-Constrained Delay Tolerant Networks Wed, 15 Oct 2014 07:03:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/623193/ The nonexistence of end-to-end path between the sender and the receiver poses great challenges to the successful message transmission in delay tolerant networks. Probabilistic routing provides an efficient scheme to route messages, but most existing probabilistic routing protocols do not consider whether a message has enough time-to-live to reach its destination. In this paper, we propose an improved probabilistic routing algorithm that fully takes into account message’s time-to-live when predicting the delivery probability. Based on statistical analysis, we compute and update the expected intermeeting times between nodes. And then the probability for a message to be delivered within its time-to-live is computed based on the assumed exponential distribution. We further propose an optimal message schedule policy, by modeling the buffer management problem as 0-1 knapsack, of which the maximum delivery probability sum can be achieved by resorting to the back track technique. Extensive simulations are conducted and the results show that the proposed algorithm can greatly enhance routing performance in terms of message delivery probability, overhead ratio, and average hop count. Jixing Xu, Jianbo Li, Shan Jiang, Chenqu Dai, and Lei You Copyright © 2014 Jixing Xu et al. All rights reserved. Loop Assisted Synchronization-Free Localization for Underwater Acoustic Sensor Networks Tue, 14 Oct 2014 08:48:36 +0000 http://www.hindawi.com/journals/ijdsn/2014/829174/ Underwater acoustic sensor networks (UASNs) have attracted significant attention recently. Localization is one of the most important issues associated with UASNs. Most of the existing underwater localization algorithms require time synchronization. However, time synchronization is difficult to be achieved in the underwater networks. The beam width and three-dimensional direction of underwater acoustic sensor nodes are ignored by the existing underwater localization algorithms. This will increase the difficulty to avoid time synchronization. We develop a loop assisted synchronization-free localization to achieve synchronization-free localization algorithm when taking into account the beam width and direction of the underwater nodes. We propose link detection stage to get link state information (symmetry and length). In addition we introduce a loop-assisted localization method to solve the problem of asymmetric link ranging without time synchronization. Finally, we propose an intersections based location estimation mechanism for error problem in practical measurement and we improve the localization accuracy. The simulation results and experimental results verify the effectiveness and feasibility of the proposed work. Song Zhang, Deshi Li, Lei Li, and Zilong Liao Copyright © 2014 Song Zhang et al. All rights reserved. Distributed Vector Quantization over Sensor Network Mon, 13 Oct 2014 07:25:17 +0000 http://www.hindawi.com/journals/ijdsn/2014/189619/ A vector quantizer is a system for encoding the original data to reduce the bits needed for communication and storage saving while maintaining the necessary fidelity of the data. Signal processing over distributed network has received a lot of attention in recent years, due to the rapid development of sensor network. Gathering data to a central processing node is usually infeasible for sensor network due to limited communication resource and power. As a kind of data compression methods, vector quantization is an appealing technique for distributed network signal processing. In this paper, we develop two distributed vector quantization algorithms based on the Linde-Buzo-Gray (LBG) algorithm and the self-organization map (SOM). In our algorithms, each node processes the local data and transmits the local processing results to its neighbors. Each node then fuses the information from the neighbors. Our algorithms remarkably reduce the communication complexity compared with traditional algorithms processing all the distributed data in one central fusion node. Simulation results show that both of the proposed distributed algorithms have good performance. Chunguang Li and Yiliang Luo Copyright © 2014 Chunguang Li and Yiliang Luo. All rights reserved. Reliability Aware Routing for Intra-Wireless Body Sensor Networks Sun, 12 Oct 2014 11:29:49 +0000 http://www.hindawi.com/journals/ijdsn/2014/786537/ With the promise of cost effective, unobtrusive, and unsupervised continuous monitoring, wireless body sensor networks (WBSNs) have attracted a wide range of monitoring applications such as medical and healthcare, sport activity, and rehabilitation systems. Most WBSN’s medical and healthcare applications are real-time and life-critical, which require strict guarantee of quality of service (QoS), in terms of latency, and reliability. Reliability in routing plays key role in providing the overall reliability in WBSNs. This paper presents reliability aware routing (RAR) for intra-WBSNs that aims to provide high reliability for reliability constraint data packets. It considers the high and dynamic path loss due to body postural movements and temperature rise of the implanted biomedical sensor nodes. We have used two network models in this paper: RAR without Relays (RAR) and RAR with Relays (RARR). The simulation results reveal that RARR outperforms the other state-of-the-art schemes while RAR has slightly low reliability at low data rates as compared to RARR but significantly higher than other state-of-the-art schemes. Javed Iqbal Bangash, Abdul Hanan Abdullah, Mohammad Abdur Razzaque, and Abdul Waheed Khan Copyright © 2014 Javed Iqbal Bangash et al. All rights reserved. Performance Analysis of Resource-Aware Task Scheduling Methods in Wireless Sensor Networks Mon, 22 Sep 2014 07:51:27 +0000 http://www.hindawi.com/journals/ijdsn/2014/765182/ Wireless sensor networks (WSNs) are an attractive platform for monitoring and measuring physical phenomena. WSNs typically consist of hundreds or thousands of battery-operated tiny sensor nodes which are connected via a low data rate wireless network. A WSN application, such as object tracking or environmental monitoring, is composed of individual tasks which must be scheduled on each node. Naturally the order of task execution influences the performance of the WSN application. Scheduling the tasks such that the performance is increased while the energy consumption remains low is a key challenge. In this paper we apply online learning to task scheduling in order to explore the tradeoff between performance and energy consumption. This helps to dynamically identify effective scheduling policies for the sensor nodes. The energy consumption for computation and communication is represented by a parameter for each application task. We compare resource-aware task scheduling based on three online learning methods: independent reinforcement learning (RL), cooperative reinforcement learning (CRL), and exponential weight for exploration and exploitation (Exp3). Our evaluation is based on the performance and energy consumption of a prototypical target tracking application. We further determine the communication overhead and computational effort of these methods. Muhidul Islam Khan and Bernhard Rinner Copyright © 2014 Muhidul Islam Khan and Bernhard Rinner. All rights reserved. Advanced Sensor Technology and Applications in Industrial Control System 2014 Thu, 18 Sep 2014 06:14:26 +0000 http://www.hindawi.com/journals/ijdsn/2014/182382/ Tai-hoon Kim, Sabah Mohammed, Ruay-Shiung Chang, and Carlos Ramos Copyright © 2014 Tai-hoon Kim et al. All rights reserved. P-LEACH: An Efficient Cluster-Based Technique to Track Mobile Sinks in Wireless Sensor Networks Wed, 17 Sep 2014 06:04:51 +0000 http://www.hindawi.com/journals/ijdsn/2014/803656/ For a wireless sensor network (WSN) with a large number of inexpensive sensor nodes, energy efficiency is the major concern in designing network structure and related algorithms. If network collects sensor data using mobile sinks, object tracking mechanism must consider the energy efficiency of sensor nodes in the networks as a whole. Recently research works on WSNs with mobile sinks apply prediction techniques for sink tracking in order to improve tracking precision while keeping the number of active nodes to the minimum. In this paper, we analyze existing works for sink tracking in WSN and propose P-LEACH that is cluster-based prediction technique for WSN with mobile sinks. Simulation results show that P-LEACH performs better than previous techniques in terms of energy saving of sensor nodes and data transmission performance. Sungchol Cho, Li Han, Bokgyu Joo, and Sunyoung Han Copyright © 2014 Sungchol Cho et al. All rights reserved. A Lightweight Classification Algorithm for External Sources of Interference in IEEE 802.15.4-Based Wireless Sensor Networks Operating at the 2.4 GHz Tue, 16 Sep 2014 09:23:02 +0000 http://www.hindawi.com/journals/ijdsn/2014/265286/ IEEE 802.15.4 is the technology behind wireless sensor networks (WSNs) and ZigBee. Most of the IEEE 802.15.4 radios operate in the crowded 2.4 GHz frequency band, which is used by many technologies. Since IEEE 802.15.4 is a low power technology, the avoidance of interference is vital to conserve energy and to extend the lifetime of devices. A lightweight classification algorithm is presented to detect the common external sources of interference in the 2.4 GHz frequency band, namely, IEEE 802.11-based wireless local area networks (WLANs), Bluetooth, and microwave ovens. This lightweight algorithm uses the energy detection (ED) feature (the feature behind received signal strength indication (RSSI)) of an IEEE 802.15.4-compliant radio. Therefore, it classifies the interferers without demodulation of their signals. As it relies on time patterns instead of spectral features, the algorithm has no need to change the channel. Thus, it allows the radio both to stay connected to the channel and to receive while scanning. Furthermore, it has a maximum runtime of merely one second. The algorithm is extensively tested in a radio frequency anechoic chamber and in real world scenarios. These results are presented here. Sven Zacharias, Thomas Newe, Sinead O’Keeffe, and Elfed Lewis Copyright © 2014 Sven Zacharias et al. All rights reserved. Multi-Channel Packet-Analysis System Based on IEEE 802.15.4 Packet-Capturing Modules Tue, 16 Sep 2014 07:42:06 +0000 http://www.hindawi.com/journals/ijdsn/2014/216504/ There have been increasing demands for research into multi-channel-based wireless sensor network protocols and applications to support requirements such as increased throughput and real-time or reliable transmission. Researchers or developers of these protocols and applications have to simultaneously analyze the exchanged packets for correctness of both their contents and message exchange timelines. However, if developers were to use multiple conventional single-channel packet sniffers for this purpose, debugging during development and the verification process becomes extremely tedious and difficult because of the need to check the correctness of the protocols over multiple channels individually. Therefore, we present a multi-channel packet-analysis system (MPAS) that helps in debugging and verification for multi-channel protocols or applications. Wireless packets are detected and timestamped by each sniffer module in the MPAS for each channel, and packets are preprocessed and transmitted to a GUI-based analyzer, which then parses the received packets and shows them in order. We present the design and implementation results of the MPAS and evaluate its performance by comparing it against a widely used packet sniffer. Seong-eun Yoo, Poh Kit Chong, Jeonghwan Bae, Tae-Soo Kim, Hiecheol Kim, and Joonhyuk Yoo Copyright © 2014 Seong-eun Yoo et al. All rights reserved. QoS-Based Path Switching Mechanism in Mobile SCTP Mon, 15 Sep 2014 08:15:43 +0000 http://www.hindawi.com/journals/ijdsn/2014/282181/ In mobile SCTP, a mobile terminal has two or more network interfaces and vertical handover occurs when it moves from one network to another. The delay due to the handover process and the slow-start phase of SCTP’s congestion control after handover cause substantial performance degradation. If the mobile node goes back and forth frequently, excessive handovers occur and data transmission quality deteriorates. In order to provide the required level of QoS for on-going application, the frequency of handovers should be kept minimized. In this paper, we propose a transport layer handover mechanism using the mobile SCTP. We take the QoS requirements of application as the major criterion in deciding path switching. In our mechanism, the mobile node in overlapping area does not perform handover if the current network metrics satisfy the QoS requirements of on-going application. Both analytic evaluation and simulation results show that the proposed mechanism significantly improves the throughput by suppressing unnecessary handovers. Our research results can also be applied to distributed mobile sensor networks. Li Han, Shimin Sun, Bokgyu Joo, and Sunyoung Han Copyright © 2014 Li Han et al. All rights reserved. Theoretical and Linearity Analysis for Pressure Sensors and Communication System Development Sun, 14 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/902976/ For the safety, reliability, and fuel economy, new road vehicles and automotive pressure sensor are being equipped with tire pressure measurement system (TPMS) in the vehicle. This paper describes the theoretical analysis and linear behavior of direct-type tire pressure sensor while the vehicle is operating. A rugged pressure sensor, thin-film piezoresistive pressure sensor, design is presented as a modular design approach for TPMS, where all the main parts of the TPMS can be connected together for easiness in integration, maintenance, and replaceability. This can also result in reducing replacement cost as well as maintaining linearity behavior of pressure sensor’s property. Three-dimensional model was analyzed with material properties; the resonance frequency of the model calculated is 24 kHz and sensitivity is calculated to be 1.2 µV/V·kPa. Our result shows that a thin-film technology of sensor design is still a viable solution for vehicular sensor and system measurement development. Taikyeong Jeong Copyright © 2014 Taikyeong Jeong. All rights reserved. Applications of Soil Moisture Sensor with Electrokinetic Ion Trap Mechanism Thu, 11 Sep 2014 07:10:10 +0000 http://www.hindawi.com/journals/ijdsn/2014/139616/ A sensor comprising a pair of stainless steel planar electrodes and a capacitance meter is proposed for the real-time monitoring of the moisture content in soil. As rain falls on the ground, the moisture content of the soil between the two electrodes increases. The resulting change in the dielectric constant of the sensing material (soil) produces a corresponding change in the capacitance signal, from which the moisture content can then be inversely derived. The measurement performance of the proposed sensor is enhanced by means of an ion trap mechanism comprising two graphite mesh electrodes positioned orthogonally to the measurement electrodes. A DC voltage is applied to the two electrodes such that the anions and cations in the water are trapped by the positive and negative electrodes, respectively, thereby minimizing their effects on the sensing operation. The experimental results show that the proposed sensor achieves a high degree of sensitivity (i.e., 1.27 μF/%) for gravimetric water contents ranging from 21 to 28%. Moreover, it is shown that the sensor has a repeatability of ±0.71% and ±0.55% for low and high gravimetric water contents, respectively. Ming-Hsi Lee, De-Jian Tsai, and Chia-Yen Lee Copyright © 2014 Ming-Hsi Lee et al. All rights reserved. Efficient Wireless Vibration Data Sensing and Signal Processing Technique Based on the Android Platform Thu, 11 Sep 2014 06:20:39 +0000 http://www.hindawi.com/journals/ijdsn/2014/278560/ Recently, many researches on big-data sensing and analysis have been actively promoted. The big data, which is generated by the digital and networked environment, is referred to to form not only numerical data, but also large-scale data for storing image data and character. Usually, many data measured through sensors are very large in scale in various vibration measurements. Measurement methods for vibration analysis currently consist of a general sensing scheme using cabling to obtain vibration data. The system is difficult to use efficiently in a location where equipment installation is not easy. We proposed a novel vibration measurement system that includes a main hardware module and a wireless data transceiver module. The system is easy to use and field data are transmitted to a remote location using Bluetooth communication and the Android platform. Nonexpert personnel can obtain field vibration data for transport, even over long distances. Through experiments in field test, we verify that the stable remote sensing range reaches up to 150 m in real-time communication without any data loss. Chan-Seob Park, Ryong Baek, Woong Hoe, Byung-Gyu Kim, and Hyun-Jun Lee Copyright © 2014 Chan-Seob Park et al. All rights reserved. An Energy-Efficient Data Collection Method for Wireless Multimedia Sensor Networks Thu, 11 Sep 2014 06:10:34 +0000 http://www.hindawi.com/journals/ijdsn/2014/698452/ In wireless sensor networks (WSNs), some sensor nodes transmit their acquired data to a far distant base station directly or by linking several relay nodes. WSNs might not be able to operate if a sensor node completely consumes its battery power and does not perform its designated operation. Semiconductor technology drives sensor networks to collect video and audio data as well as environmental data. Therefore, energy is one of the most important resources in wireless multimedia sensor networks (WMSNs), and clustering is proposed to reduce energy consumption. When a mobile sink is used, a lot of energy is saved, and the lifetime of the network can be extended because the sensor nodes do not need to transmit multimedia data to a far distant base station. We propose an energy-efficient data collection method to extend the lifetime of networks that use a mobile sink. By using the neighborhood density clustering method and defining an optimal path for the mobile sink, the proposed method extends the life of the WMSN. Simulation results show that the proposed method increases the lifetime of WMSNs by up to 15 rounds, compared with LEACH. And data collection time is decreased owing to the predefined path for the mobile sink. Ilkyu Ha, Mamurjon Djuraev, and Byoungchul Ahn Copyright © 2014 Ilkyu Ha et al. All rights reserved. L2ER: Low-Latency and Energy-Based Routing Protocol for Cognitive Radio Ad Hoc Networks Thu, 11 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/963202/ Cognitive radio ad hoc networks (CRAHNs) are active, self-organized, and dynamic networks, in which cognitive users can communicate with each other in an ad hoc fashion. Various delay and energy-based routing protocols have been proposed for CRAHNs. However, these protocols do not consider the delay and node energy in the routing process, which can significantly affect performance. Delay and node energy are important factors in ad hoc networks in which devices have limited power. In this paper, we propose a new routing protocol, named low-latency and energy-based routing (L2ER) protocol; it considers both delay and energy for the routing decisions in CRAHNs. The performances of the proposed protocol are evaluated comparing to two other protocols in terms of average throughput, end-to-end delay, packet delivery ratio, and network lifetime. Simulation results show that the proposed protocol performs better than the existing protocols in many aspects. Rana Asif Rehman and Byung-Seo Kim Copyright © 2014 Rana Asif Rehman and Byung-Seo Kim. All rights reserved. Simplified Pedestrian Tracking Filters with Positioning and Foot-Mounted Inertial Sensors Thu, 04 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/850835/ Pedestrian tracking is one of the bases for many ubiquitous context-aware services, but it is still an open issue in indoor environments or when GPS estimations are not optimal. In this paper, we propose two novel different data fusion algorithms to track a pedestrian using current positioning technologies (i.e., GPS, received signal strength localization from Wi-Fi or Bluetooth networks, etc.) and low cost inertial sensors. In particular, the algorithms rely, respectively, on an extended Kalman filter (EKF) and a simplified complementary Kalman filter (KF). Both approaches have been tested with real data, showing clear accuracy improvement with respect to raw positioning data, with much reduced computational cost with respect to previous high performance solutions in literature. The fusion of both inputs is done in a loosely coupled way, so the system can adapt to the infrastructure that is available at a specific moment, delivering both outdoors and indoors solutions. Henar Martin, Juan A. Besada, Ana M. Bernardos, Eduardo Metola, and José R. Casar Copyright © 2014 Henar Martin et al. All rights reserved. The Feasibility of Exploiting IEEE 802.11n for Addressing MAC Layer Overheads in UASNs Wed, 03 Sep 2014 06:21:57 +0000 http://www.hindawi.com/journals/ijdsn/2014/292538/ Underwater acoustic sensor networks (UASNs) consist of remotely deployed sensor nodes under sea or other water environments. Due to the extreme limitations faced by radio signals under water, acoustic channels are utilized for communication in such networks. However, UASNs are challenged by the characteristics of underwater acoustic channels such as lower signal propagation speed and higher signal attenuation. On top of such a challenged physical medium, MAC schemes which are designed based on their terrestrial counter parts are required to add extra overheads to the communication channel wasting the limited network resources. MAC layer overheads such as bandwidth wastage for interframe spaces and contention for occupying physical medium put limitations to the maximum reachable throughput of UASNs. IEEE 802.11n has well defined various MAC and physical layer enhancements to overcome throughput barrier in wireless LANs which includes two frame aggregation schemes, namely, A-MPDU and A-MSDU. In this paper, we study the feasibility of applying those frame aggregations well defined in IEEE 802.11n for reducing MAC layer overheads in UASNs. Based on simulation studies, we evaluate that these frame aggregation schemes are applicable in UWSNs. Asanka Sayakkara, Sungwon Lee, and Dongkyun Kim Copyright © 2014 Asanka Sayakkara et al. All rights reserved. Energy-Efficient Policy Based on Cross-Layer Cooperation in Wireless Communication Wed, 03 Sep 2014 05:54:29 +0000 http://www.hindawi.com/journals/ijdsn/2014/831686/ Cooperative communication has emerged as a new wireless network communication concept, in which parameter optimization such as cross-layer cooperation plays an important role. Heuristic evaluation postdecision state learning algorithm (HE-PDS) is proposed in cross-layer cooperation. The proposed algorithm exploits the determinate state information and jointly considers the transmitting power and channel state condition at the physical layer and the buffer congestion control at the media access control layer. The experimental results show that the cumulative average total costs of HE-PDS algorithm decrease about ten times and 8% under the maximum delay and throughput constraints and the power costs decrease about 50% and 28% under various delay limits and about 100% and 56% under the different throughput constraints than the traditional Q algorithm and PDS algorithm, demonstrating that the proposed algorithm has much better energy-efficient performance and faster convergence speed and outperforms the traditional Q learning algorithm and PDS learning algorithm. Juan Zhang, Hong Jiang, Hesong Jiang, and Chunmei Chen Copyright © 2014 Juan Zhang et al. All rights reserved. Optimization of Sampling Cell Size for Fingerprint Positioning Tue, 02 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/273801/ The fingerprint positioning based on received signal strength has a widespread development in many applications since the technology does not depend on additional hardware deployment. However, the site survey process which is executed before fingerprint positioning is time consuming and labor intensive. Sampling cell size directly affects the localization precision and the survey workload. We propose a sampling cell size optimization method to release the survey workload while holding the precision. We adopted the Gaussian process model to estimate the received signal strength based on some samples and used the inherent maximum Euclidean error of fingerprint vectors to compute the optimal cell size. We conduct some experiments to validate the efficiency of the mechanism. And the results show that our method can largely reduce the workload of the site survey process. Wei Liu, Yongle Chen, Yongping Xiong, Limin Sun, and Hongsong Zhu Copyright © 2014 Wei Liu et al. All rights reserved. A Location Estimation Algorithm Based on RSSI Vector Similarity Degree Mon, 01 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/371350/ We present a detailed study on the RSS-based location techniques in wireless sensor networks (WSN). There are two aspects in this paper. On the one hand, the accurate RSSI received from nodes is the premise of accurate location. Firstly, the distribution trend of RSSI is analyzed in this experiment and determined the loss model of signal propagation by processing experimental data. Secondly, in order to determine the distance between receiving nodes and sending nodes, Gaussian fitting is used to process specific RSSI at different distance. Moreover, the piecewise linear interpolation is introduced to calculate the distance of any RSSI. On the other hand, firstly, the RSSI vector similarity degree (R-VSD) is used to choose anchor nodes. Secondly, we designed a new localization algorithm which is based on the quadrilateral location unit by using more accurate RSSI and range. Particularly, there are two localization mechanisms in our study. In addition, the generalized inverse is introduced to solve the coordinates of nodes. At last, location error of the new algorithm is about 17.6% by simulation experiment. Fengjun Shang, Wen Su, Qian Wang, Hongxia Gao, and Qiang Fu Copyright © 2014 Fengjun Shang et al. All rights reserved. Web of Things-Based Remote Monitoring System for Coal Mine Safety Using Wireless Sensor Network Sun, 31 Aug 2014 12:02:43 +0000 http://www.hindawi.com/journals/ijdsn/2014/323127/ Frequent accidents have occurred in coal mine enterprises; therefore, raising the technological level of coal mine safety monitoring systems is an urgent problem. Wireless sensor networks (WSN), as a new field of research, have broad application prospects. This paper proposes a Web of Things- (WoT-) based remote monitoring system that takes full advantage of wireless sensor networks in combination with the CAN bus communication technique that abstracts the underground sensor data and capabilities into WoT resources to offer services using representational state transfer (REST) style. We also present three different implemented scenarios for WoT-based remote monitoring systems for coal mine safety, for which the system performance has been measured and analyzed. Finally, we describe our conclusions and future work. Cheng Bo, Cheng Xin, Zhai Zhongyi, Zhang Chengwen, and Chen Junliang Copyright © 2014 Cheng Bo et al. All rights reserved. Adjusting Control Packet Transmission Intervals in Low Power Sensor Systems Thu, 28 Aug 2014 06:32:57 +0000 http://www.hindawi.com/journals/ijdsn/2014/139682/ In order to construct an efficient wireless sensor system, it is necessary to increase the lifetime of its battery-operated sensor nodes. To this end, a wireless body sensor system adopts a transmission power control (TPC) mechanism. However, existing TPC mechanisms adjust the transmission power level (TPL) according to the received signal strength indication (RSSI) value of the most recently received data packet. Therefore, they do not effectively cope with dynamically changing wireless body channel environments. In particular, when a wireless channel is unstable, changes in the TPL should be avoided to prevent energy consumption due to unnecessary transmission and reception of control packets. Accordingly, this paper proposes a new TPC mechanism that adaptively changes the control packet transmission interval on the basis of the current channel condition. Further, actual sensors are used to experimentally verify that the proposed mechanism (1) performs well in all channel environments and (2) facilitates the construction of an efficient wireless body sensor system. Gangman Yi, Daeun Yu, and Namgi Kim Copyright © 2014 Gangman Yi et al. All rights reserved. A Scale-Free Topology Construction Model for Wireless Sensor Networks Thu, 28 Aug 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/764698/ A local-area and energy-efficient (LAEE) evolution model for wireless sensor networks is proposed. The process of topology evolution is divided into two phases. In the first phase, nodes are distributed randomly in a fixed region. In the second phase, according to the spatial structure of wireless sensor networks, topology evolution starts from a network of very small size which contains the sink, grows with an energy-efficient preferential attachment rule in the new node’s local-area, and stops until all nodes are connected into network. Both analysis and simulation results show that the degree distribution of LAEE follows the power law. The comparison shows that this topology construction model has better tolerance against energy depletion or random failure than other nonscale-free WSN topologies. Lurong Jiang, Xinyu Jin, Yongxiang Xia, Bo Ouyang, Duanpo Wu, and Xi Chen Copyright © 2014 Lurong Jiang et al. All rights reserved. PUAR: Performance and Usage Aware Routing Algorithm for Long and Linear Wireless Sensor Networks Thu, 28 Aug 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/464963/ Aiming at requirements of performance and usage in the monitoring of tunnels with the long and linear structure, this work demonstrates a low-energy and quality of service- (QoS-) supported uneven clustering routing algorithm based on the labor cost called PUAR. PUAR realizes uneven clusters by a designed cluster radius related to the distance and the labor cost, with consideration of the residual energy and spatial layout of sensor nodes in the cluster head selection. With QoS support, PUAR uses the quality of link to reduce the packet loss and shortens the total transmitting distance to reduce the average delivery delay in multihop transmission. For the usage requirements of tunnel monitoring, PUAR utilizes the labor cost of replacing batteries to realize local or global energy balance. According to the analysis and simulation results, PUAR is found to achieve low-power consumption and reliable QoS support, and it can also reduce the operating cost of tunnel monitoring. Bin He and Gang Li Copyright © 2014 Bin He and Gang Li. All rights reserved. Cognitive Multihop Wireless Sensor Networks over Nakagami- Fading Channels Thu, 28 Aug 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/630823/ Considering the effect of imperfect channel state information (CSI), we study the performance of a cluster-based cognitive multihop wireless sensor network with decode-and-forward (DF) partial relay selection over Nakagami-m fading channels. The closed-form expressions for the exact outage probability and bit error rate (BER) of the secondary system are derived and validated by simulations. Asymptotic outage analysis in high SNR regime reveals that the diversity order is determined by the minimum fading severity parameter of all the secondary transmission links, irrespective of the CSI imperfection. It is shown that the fading severity of the secondary transmission links has more influence on the outage performance than that of the interference links. We also conclude that, for secondary nodes whose transmit power is restricted by the interference constraint of the primary user, increasing the number of relaying hops is an effective way to improve their transmission performance. Besides, increasing the number of available relays in each relay cluster can mitigate the performance degradation caused by CSI imperfection. Xing Zhang, Jia Xing, Zhi Yan, Yue Gao, and Wenbo Wang Copyright © 2014 Xing Zhang et al. All rights reserved. Smart Solutions in Elderly Care Facilities with RFID System and Its Integration with Wireless Sensor Networks Wed, 27 Aug 2014 05:12:15 +0000 http://www.hindawi.com/journals/ijdsn/2014/713946/ Healthcare and medical advances have prolonged human life and thus have led to increasing numbers of elderly individuals. To make their lives more convenient, several ubiquitous technologies have been considered, including the RFID system, which can play a vital role in elderly care by caregivers as well as by elderly individuals themselves. Caregivers can take advantage of the RFID system by recording and tracking elderly individuals’ belongings and assisting these individuals in healthcare provision by accessing their relevant information, among others. Similarly, the RFID system can help manage elderly individuals’ daily lives by reminding them of their daily schedules (e.g., reminding them to take medicine on time) and tracking their personal belongings, among others. In addition, the RFID system can mitigate human errors such as medical mistakes, delays in service provision, and hassles in tracking and identifying patients and objects. This study provides a survey of solutions proposed in the literature and discusses the potential benefits of integrating the RFID system with sensors and applying the integrated system. In addition, the study addresses the opportunities, technological challenges, and research directions for the integrated RFID system in the context of smart solutions in elderly care facilities. Gyanendra Prasad Joshi, Srijana Acharya, Chang-Su Kim, Byung-Seo Kim, and Sung Won Kim Copyright © 2014 Gyanendra Prasad Joshi et al. All rights reserved. An Efficient Localization Method Based on Adaptive Optimal Sensor Placement Wed, 27 Aug 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijdsn/2014/983618/ We propose a ZigBee-based localization method that estimates the distance between ZigBee nodes employing the strength of wireless signal. It enables us to track the location of a user by means of trilateration, using the distance between fixed nodes deployed at predetermined locations and a mobile base station. In addition, we propose a method to determine the optimal placement of the fixed nodes using minimum Bayes error estimation based on Gaussian distributions. As a result, this method can accurately estimate the position of the mobile base station with a minimum number of fixed nodes. Jin-Hee Lee, Kyeongyul Kim, Sang-Chul Lee, and Byeong-Seok Shin Copyright © 2014 Jin-Hee Lee et al. All rights reserved.