International Journal of Distributed Sensor Networks The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Optimization of Sampling Cell Size for Fingerprint Positioning Tue, 02 Sep 2014 00:00:00 +0000 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 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 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 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. PUAR: Performance and Usage Aware Routing Algorithm for Long and Linear Wireless Sensor Networks Thu, 28 Aug 2014 00:00:00 +0000 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 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. A Scale-Free Topology Construction Model for Wireless Sensor Networks Thu, 28 Aug 2014 00:00:00 +0000 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. Smart Solutions in Elderly Care Facilities with RFID System and Its Integration with Wireless Sensor Networks Wed, 27 Aug 2014 05:12:15 +0000 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. Transmission Power Controlled Localization with Topology Building for NLOS Environments Wed, 27 Aug 2014 00:00:00 +0000 The network which knows location of all nodes can improve the network capacity and lifetime in location-aware networks. However, localization algorithm of the network has to update its target node location due to mobility of target nodes and intermittent occurrence of interference. The update procedures cause frequent broadcasting and calculation for relocalization; therefore, maintaining the transmission power control (TPC) in the wireless sensor networks (WSNs) is valuable to the network. This paper proposes a new algorithm of transmission power controlled localization for indoor environment. Firstly, we propose minimum spanning tree (MST) based topology control with location error compensation algorithm to improve location accuracy and prevent target nodes from connecting to unstable links in non-line-of-sight (NLOS) condition. Secondly, we use TPC algorithm to improve the network lifetime. Each target node dynamically adjusts the power and the received signal strength (RSS) target by using the TPC algorithm. Experimental results show that the proposed algorithm compensates for location errors in NLOS condition while reducing the transmission power. Jin-Ho You, Jong-Hyeok Jeon, Tae-Hyung Lee, and Young-Goo Kwon Copyright © 2014 Jin-Ho You et al. All rights reserved. An Efficient Localization Method Based on Adaptive Optimal Sensor Placement Wed, 27 Aug 2014 00:00:00 +0000 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. Semidefinite Relaxation Method for Target Localization by MIMO Radar Using Bistatic Ranges Tue, 26 Aug 2014 11:52:17 +0000 We address the target localization problem by using bistatic range (BR) measurements in widely separated multiple-input multiple-output (MIMO) radar network. The BR information defines a set of elliptic equations from which the target location can be estimated. By applying the semidefinite relaxation (SDR), we transform the nonconvex BR-based localization problem into a convex semidefinite programming (SDP) problem, whose solution is guaranteed to be globally optimal without initial estimate. Moreover, we extend this method to robustly solve the localization problem in the presence of antenna position errors. Simulation results demonstrate that the proposed SDR method provides superior estimation performance over the existing method. Bin Sun, Haowen Chen, Xizhang Wei, and Xiang Li Copyright © 2014 Bin Sun et al. All rights reserved. Link Sensing-Adaptive Passive Object Localization in Wireless Sensor Networks Mon, 18 Aug 2014 09:35:35 +0000 The passive object localization (POL) problem in wireless sensor networks aims to determine the location of a target without any device attached for receiving or transmitting signal. This problem is challenging as there is very limited information available for deriving the target location. By combining the diffraction and scattering models, we propose a link sensing adaptive approach to POL, which first decides the target position attribute based on the signal strength and then localizes the target in different modes. We conduct rigorous localizability analyses and design a unit localization area scheme to achieve a higher level of localization accuracy. The efficacy of the proposed method is evaluated through comprehensive experiments in real life network environments. Tianzhang Xing, Ju Wang, Liqiong Chang, Xiaojiang Chen, Dingyi Fang, and Chase Q. Wu Copyright © 2014 Tianzhang Xing et al. All rights reserved. Event-Centric Situation Trust Data Aggregation Mechanism in Distributed Wireless Network Sun, 17 Aug 2014 00:00:00 +0000 In wireless sensor networks, the characteristics of the openness and vulnerability can lead to communication failure and node capture more easily. To cope with the deviation problem caused by the compromised nodes, this paper proposes a situation data fusion mechanism which can enhance reliability and integrality. It makes a reliability assurance scheme, which not only establishes a project distinguishing purposive and purposeless acts, but also builds a trust awareness rule based on historical trust and the correlations among current nodes. Furthermore, the data integrality is ensured in three stages, respectively. Firstly, in event detection stage, the proposed mechanism detects events and pretreats data to improve accuracy through most trust majority rule after collecting data. Moreover, during data fusion stage, data filtration is adopted to extract credible data. Additionally, the fusion weights of transactions depend on trust, so that they will change with the passage of time. As a result, the final fusion data will be closer to real value. Finally, in consistency detection stage, the detection rule with lower communication traffic is utilized to judge whether the centers are credible. Theory analyses and simulation results verify that the new mechanism can reduce the deviation. Meanwhile, reliability and stability have been validly enhanced. Fangwei Li, Yifang Nie, Fan Liu, Jiang Zhu, and Haibo Zhang Copyright © 2014 Fangwei Li et al. All rights reserved. The Optimization Model of Target Recognition Based on Wireless Sensor Network Thu, 14 Aug 2014 13:49:16 +0000 In the application of opportunistic networking in wireless sensor network, the technology of target recognition is very important. However, since the sensor reports are typically inconsistent, incomplete, or fuzzy, the technology of target recognition whereby sensor reports is a major challenge. In this paper, based on the minimization of inconsistencies among the sensor reports, a new optimization model of target recognition is presented by using a convex quadratic programming (QP) formulation. Firstly, the description method of sensor report is introduced and then we talk about how to set up this new optimization model of target recognition by using the wireless sensor network reports and how to calculate the solution of this new optimization model. Finally, theory analysis and numeric simulation indicate that this optimization model can generate reasonable fusion results, which is similar to the Dempster-Shafer (D-S) evidence inference model. Furthermore, in contrast to D-S evidence inference model, this optimization model can fuse sensor reports of the form more general than that allowed by the D-S evidence inference model without additional processes. Meantime, it can deal with the high conflict sensor reports. Zheng Dou, Yu Sun, and Yun Lin Copyright © 2014 Zheng Dou et al. All rights reserved. Intelligent Surveillance for Understanding Events in Urban Traffic Environments Thu, 14 Aug 2014 12:05:51 +0000 The main goal of intelligent surveillance consists in providing security systems with the skills required for correctly detecting and analyzing events in monitored environments. Since these environments are complex and the information is distributed through them, the use of agent-based approaches has become more and more popular when monitoring moving objects. This paper describes how an existing agent platform has been adopted and used to give support to intelligent surveillance systems. Agents deployed by means of this platform implement a behavior-based model that is flexible enough to deal with the challenges that monitored environments pose. Two case studies of urban traffic environments are discussed to prove the feasibility of the proposal. D. Vallejo, F. J. Villanueva, J. A. Albusac, C. Glez-Morcillo, and J. J. Castro-Schez Copyright © 2014 D. Vallejo et al. All rights reserved. In-Network Filtering Schemes for Type-Threshold Function Computation in Wireless Sensor Networks Thu, 14 Aug 2014 12:04:19 +0000 Data collection in wireless sensor networks (WSNs) can become extremely expensive in terms of power consumption if all measurements have to be fetched. However, since multiple applications do not require data from all nodes but to compute a function over a smaller data set, much of the available data on the network can be considered irrelevant and not worthy of spending energy. In this context, in-network filtering schemes can be used to forward only relevant data towards a sink node for processing purposes. In this work, we propose and evaluate two schemes that can drive this filtering process. Both of them are based on the integration of metaheuristics and learning algorithms inspired by nature. In particular, we consider the computation of the maximum function as case study for these schemes. We investigate the trade-off between communications costs, which are directly associated with power consumption, and error costs due to fetching not all relevant data. We show by simulation that communication costs can be significantly reduced with respect to traditional schemes while keeping the computation error bounded. Guillermo G. Riva and Jorge M. Finochietto Copyright © 2014 Guillermo G. Riva and Jorge M. Finochietto. All rights reserved. Distributed Congestion Mitigation and Medium Access in Duty Cycling Wireless Sensor Networks Thu, 14 Aug 2014 00:00:00 +0000 Duty cycling is an efficient design approach to achieve energy efficiency in wireless sensor networks. However, it may aggravate congestion due to long access delay and amplified hidden/exposed terminal problems. This paper first investigates some key facts that impact congestion and deteriorate packet transmission. With above observations, we propose a queue length based contention window adjustment approach, which allows congested nodes having high priority to access the channel. Then, a batch transmission scheme is introduced to drain accumulated packets rapidly. Finally, a random preamble mechanism is designed, so that congested nodes have more chances to get channel when other transmission is happening. Through the experiments on TelosB nodes test-bed using TinyOS, evaluation results show that our proposed schemes can mitigate congestion efficiently and have better performance than traditional approaches. Hao Liu and Ye Liu Copyright © 2014 Hao Liu and Ye Liu. All rights reserved. Industrial Wireless Sensor Networks Wed, 13 Aug 2014 09:04:18 +0000 Shancang Li, Hongjian Sun, Arumugam Nallanathan, Li Xu, Shanshan Zhao, and Qindong Sun Copyright © 2014 Shancang Li et al. All rights reserved. Advanced Convergence Technologies and Practices for Wireless Ad Hoc and Sensor Networks Wed, 13 Aug 2014 05:53:36 +0000 Jongsung Kim, Ken Choi, and Wook Choi Copyright © 2014 Jongsung Kim et al. All rights reserved. Protecting Data Source Location Privacy in Wireless Sensor Networks against a Global Eavesdropper Wed, 13 Aug 2014 00:00:00 +0000 Data source location privacy (DSLP) is of great importance for some asset monitoring applications in wireless sensor networks (WSNs). Besides the source simulation (SS) method to protect the DSLP against a global eavesdropper in WSNs, other existing methods are based on the panda-hunter game model (PHGM) without considering the communication between data sources and reporter sources, which can cause them to be ineffective. Moreover, there are two limitations in SS. First, the reporter source cannot generate effective event reports. Second, it is unsuitable to track multiobjects accurately. To address the former issue, an improved source simulation (ISS) method is proposed which adjusts the event report strategy. To solve the latter issue, an updated-panda-hunter game model (UPHGM) is proposed and a formal model of the DSLP issues is also presented. Then, based on the UPHGM, an energy-efficient grid-based pull (GBP) scheme is designed to protect the DSLP by combining a light-weight security object collection scheme with an effective grid partition method. Analysis and simulation results show that GBP outperforms SS and ISS in terms of energy cost on the whole. Rong-hua Hu, Xiao-mei Dong, and Da-ling Wang Copyright © 2014 Rong-hua Hu et al. All rights reserved. Parking Backbone: Toward Efficient Overlay Routing in VANETs Tue, 12 Aug 2014 13:09:03 +0000 In vehicular ad hoc networks (VANETs), message dissemination to one or more vehicles is very challenging, due to frequent network disconnections and uncertain locations of the destination vehicles. Deploying roadside units (RSUs) is a possible solution to overcome the challenges, but it often requires a large amount of investment. In this paper, we propose the idea of Parking Backbone, which does not need any RSUs but leverages a virtual overlay network formed by outside parked vehicles to track vehicles and to disseminate messages between moving vehicles. Our scheme consists of three parts. At first, to each road, parked vehicles both at roadside and off street are grouped into a cluster as far as possible. An urban overlay network is established based on this type of clusters for data transmission. Secondly, to a specific vehicle, a daily mobility model is established, to determine its location through a corresponding location prediction algorithm. Finally, a novel message delivery scheme is designed to efficiently transmit messages to destination vehicles through the proposed virtual overlay network. Thanks to the extensive and stable outside parking in cities, once grouped into the overlay structure, data transmission can be easily achieved over the Parking Backbone. Extensive simulation results prove that our scheme achieves high performance in message dissemination. Jinqi Zhu, Ming Liu, Yonggang Wen, Chunmei Ma, and Bin Liu Copyright © 2014 Jinqi Zhu et al. All rights reserved. Sequential Uniformly Reweighted Sum-Product Algorithm for Cooperative Localization in Wireless Networks Tue, 12 Aug 2014 11:39:40 +0000 Graphical models have been widely applied in solving distributed inference problems in wireless networks. In this paper, we formulate the cooperative localization problem in a mobile network as an inference problem on a factor graph. Using a sequential schedule of message updates, a sequential uniformly reweighted sum-product algorithm (SURW-SPA) is developed for mobile localization problems. The proposed algorithm combines the distributed nature of belief propagation (BP) with the improved performance of sequential tree-reweighted message passing (TRW-S) algorithm. We apply the SURW-SPA to cooperative localization in both static and mobile networks, and evaluate its performance in terms of localization accuracy and convergence speed. Wei Li, Zhen Yang, and Haifeng Hu Copyright © 2014 Wei Li et al. All rights reserved. EHCM: A Multihop Aided Wireless Routing Protocol Based on Flow Priority in Smart Grid Tue, 12 Aug 2014 09:15:35 +0000 In traditional smart grid, data aggregator (DA) and distribution box (DB) send the data collected by sensors to base station (BS) through cellular interface, which is called single-hop communication mode (SCM). In smart grid, different data packets have different delay priorities and the BS cannot satisfy all the delay requirements of different data because of limited resources through SCM. In order to meet the QoS requirements of different priority data, we propose a new scheme: enhanced hybrid communication mode (EHCM), by introducing multihop communication mode (MCM) into this scenario to improve the network’s performance by adding another wireless interface on each node. Our scheme EHCM consists of two parts: the intracell data transmission and the cell edge data transmission. In the first part, we propose a solution to choose a relay node according to the node’s energy consumption and its residual energy and a solution to forward packets based on its priority and residual lifetime (RLT). In the second part, the tasks of data transmission can be delivered from the congested DB nodes to the adjacent idle ones to provide optimal performance. At last, the simulation shows that our scheme can satisfy the performance requirement of smart grid. Xiaobin Tan, Qin Zheng, and Ling Liu Copyright © 2014 Xiaobin Tan et al. All rights reserved. TDMA-Based Control Channel Access for IEEE 802.11p in VANETs Tue, 05 Aug 2014 13:23:50 +0000 Motivated by an efficient broadcast service in vehicular ad hoc networks (VANETs), we propose a TDMA-based channel access scheme for IEEE 802.11p control channel (CCH). The scheme reduces the rate of transmission collisions and improves the availability of time slots on the control channel by adjusting disjoint sets of time slots to vehicles moving in opposite directions and to the left and right slot frames. Further, the location information of a node is used to allocate the time slot, which efficiently decreases the rate of access collisions. Analysis and simulation results in city scenarios are presented to evaluate the performance of our scheme, which reduces significantly the transmission conflict and has shorter time delay than ADHOC and VeMAC. Weidong Yang, Wei Liu, Pan Li, and Limin Sun Copyright © 2014 Weidong Yang et al. All rights reserved. Cognitive Radio-Based Vehicular Ad Hoc and Sensor Networks Tue, 05 Aug 2014 09:26:19 +0000 Current advancements in vehicular networking lead to amplifying the issue of spectrum scarcity. Cognitive radio (CR) has emerged as the key technology that enables flexible, efficient, and reliable spectrum exploiting by unlicensed networks to use licensed spectrum bands in an opportunistic manner to alleviate the spectrum scarcity issue. We have already proposed vehicular ad hoc and sensor networks (VASNET) as a new networking paradigm for vehicular communication by utilizing wireless sensor nodes in two mobile and stationary modes. The nodes are employed to sense vehicles’ activity, for example, car crashes. Like other unlicensed networks, VASNET is supposed to operate over unlicensed spectrum bands. However, due to emergency nature of accident alarms in VASNET that must be received in minimum period of time and avoiding packet loss, in this paper we investigate CR-based VASNET, named as CR-VASNET. Various challenges and issues are discussed in details. In order to save stationary nodes’ power and enlarge the network lifetime, an optimization technique for relay node selection is proposed. Furthermore, for primary users (PU) protection, an energy detection-based scheme is suggested to calculate the probability of PU arrival. Our theoretical discussions and simulation results proved the efficient functionality of the proposed CR-VASNET as a promising vehicular networking paradigm. Mohammad Jalil Piran, Yongwoo Cho, Jihyeok Yun, Amjad Ali, and Doug Young Suh Copyright © 2014 Mohammad Jalil Piran et al. All rights reserved. A Negotiation-Based TDMA Scheduling with Consecutive Slots Assignment for Wireless Sensor Networks Tue, 05 Aug 2014 07:56:43 +0000 TDMA protocols are recognized to save energy consumption by avoiding unnecessary idle listening and communication collision. As sensor nodes are usually equipped with limited resource supply, they are thus desirable to improve network capacity and energy efficiency by adopting TDMA scheduling for wireless sensor networks (WSNs). This paper proposes a TDMA scheduling approach, which reuses time slots among sensor nodes, for WSNs. Specifically, with the idea of consecutive slots assignment, our approach can reduce both the time and energy cost of establishing nodes’ schedule. Furthermore, the energy of node’s switching is also reduced. To avoid the transmission of a node’s result interference to all irrelevant receivers within its interference range, we develop a slot negotiation mechanism for slot assignment. We perform extensive simulations in NS-2 to evaluate our proposed approach. The results show that our approach outperforms existing TDMA scheduling in terms of time and energy overhead. Bo Zeng, Yabo Dong, and Zhidan Liu Copyright © 2014 Bo Zeng et al. All rights reserved. Organizing and Querying the Big Sensing Data with Event-Linked Network in the Internet of Things Mon, 04 Aug 2014 07:09:22 +0000 Massive sensing data are generated continuously in the Internet of Things. How to organize and how to query the big sensing data are big challenges for intelligent applications. This paper studies the organization of big sensing data with event-linked network (ELN) model, where events are regarded as primary units for organizing data and links are used to represent the semantic associations among events. Several different types of queries on the event-linked network are also explored, which are different from queries on traditional relational database. We use an instance of smart home to show the effectiveness and efficiency of organization and query approaches based on the event-linked network. Yunchuan Sun, Hongli Yan, Junsheng Zhang, Ye Xia, Shenling Wang, Rongfang Bie, and Yingjie Tian Copyright © 2014 Yunchuan Sun et al. All rights reserved. An Improved Directional Broadcast Algorithm Based on Brownian Motion Thu, 24 Jul 2014 11:34:59 +0000 Several broadcast algorithms have been developed in recent years. However, the problem of reducing routing overhead in ad hoc networks is always to be concerned. This paper proposes an improved directional broadcast algorithm based on Brownian motion for AODV protocol (DBB-AODV). We bring Brownian motion into network model and gain the distribution of the nodes which encountered destination before. This algorithm uses encounter records to predict the direction to destination and forwards RREQ packets with reasonable probability according to the distribution just mentioned. Simulation results indicate that DBB-AODV saves up to 20% of average routing overhead compared to the probabilistic protocol and about 80% of the blind flooding. Shibao Li, Linlin Lou, Yu Wang, Lu Sun, and Li Hong Copyright © 2014 Shibao Li et al. All rights reserved. Three Dimensional Wireless Ad Hoc and Sensor Networks Thu, 24 Jul 2014 06:57:15 +0000 Ki-Il Kim, Hannan Xiao, Sana Ullah, and Aneel Rahim Copyright © 2014 Ki-Il Kim et al. All rights reserved. An Optimized Strategy Coverage Control Algorithm for WSN Wed, 23 Jul 2014 13:37:06 +0000 The problem of using lesser wireless sensor network nodes to achieve coverage and connection of certain areas under given coverage conditions is a priority and hotspot issue of WSN. For this reason, in this paper, an optimized strategy coverage control (OSCC) algorithm is proposed. First of all, a relation mapping model of sensor nodes and target nodes is established by OSCC which is based on geometric figure and related theories, probability theory, converge property, and so forth to complete effective reasoning and calculate certain network models. Secondly, OSCC makes efficient analysis of the calculating results figure out the least number of sensor nodes to cover specific monitoring area. Thirdly, OSCC picks out the optimal routing solution while conducting combinatorial optimization of routing path using ant colony optimization (ACO) algorithm, thus reducing the energy spending of whole network. In the end, this paper verifies OSCC algorithm by simulation experiment and proves it can use least sensor nodes to effectively cover target area. Also, OSCC helps greatly reduce network energy consuming, minimize network resources layout costs, and enhance network life cycle, simultaneously. Zeyu Sun, Weiguo Wu, Huanzhao Wang, Heng Chen, and Wei Wei Copyright © 2014 Zeyu Sun et al. All rights reserved.