International Journal of Distributed Sensor Networks The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . 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. A Graph Embedding Method Based on Sparse Representation for Wireless Sensor Network Localization Wed, 23 Jul 2014 11:49:58 +0000 In accordance with the problem that the traditional trilateral or multilateral estimation localization method is highly dependent on the proportion of beacon nodes and the measurement accuracy, an algorithm based on kernel sparse preserve projection (KSPP) is proposed in this dissertation. The Gaussian kernel function is used to evaluate the similarity between nodes, and the location of the unknown nodes will be commonly decided by all the nodes within communication radius through selection of sparse preserve projection self-adaptation and maintaining of the topological structure between adjacent nodes. Therefore, the algorithm can effectively solve the nonlinear problem while ranging, and it becomes less affected by the measuring error and beacon nodes quantity. Xiaoyong Yan, Aiguo Song, and Hao Yan Copyright © 2014 Xiaoyong Yan et al. All rights reserved. Adaptive Quantization for Distributed Estimation in Energy-Harvesting Wireless Sensor Networks: A Game-Theoretic Approach Wed, 23 Jul 2014 09:21:31 +0000 The problem of distributed estimation in energy-harvesting wireless sensor networks (EH-WSNs) is studied. In general, the energy state of an energy-harvesting sensor varies dramatically. Existing efforts mainly concentrate on the problem of distributed estimation for battery-powered WSNs, ignoring the crucial issue of energy harvesting. Therefore, the unpredictable energy harvesting, the energy storage device, and energy consumption are modeled in a unified way to jointly address the energy harvesting and distributed estimation problem. In this paper, combining with the classical adaptive distributed estimation scheme, the problem of parameter estimation in EH-WSNs is formulated as a game of complete and perfect information. Each player decides its strategy according to the others’ energy states and actions. The subgame perfect equilibrium (SPE) is derived by backward induction. Simulation results show that the proposed SPE makes full use of the harvested energy and improves the estimation performance. Hua Liu, Guiyun Liu, Yonggui Liu, Lei Mo, and Hongbin Chen Copyright © 2014 Hua Liu et al. All rights reserved. Web Spider Defense Technique in Wireless Sensor Networks Wed, 23 Jul 2014 00:00:00 +0000 Wireless sensor networks (WSNs) are currently widely used in many environments. Some of them gather many critical data, which should be protected from intruders. Generally, when an intruder is detected in the WSN, its connection is immediately stopped. But this way does not let the network administrator gather information about the attacker and/or its purposes. In this paper, we present a bioinspired system that uses the procedure taken by the web spider when it wants to catch its prey. We will explain how all steps performed by the web spider are included in our system and we will detail the algorithm and protocol procedure. A real test bench has been implemented in order to validate our system. It shows the performance for different response times, the CPU and RAM consumption, and the average and maximum values for ping and tracert time responses using constant delay and exponential jitter. Alejandro Canovas, Jaime Lloret, Elsa Macias, and Alvaro Suarez Copyright © 2014 Alejandro Canovas et al. All rights reserved. A Method for Distributed Pipeline Burst and Leakage Detection in Wireless Sensor Networks Using Transform Analysis Tue, 22 Jul 2014 09:05:59 +0000 Bursts and leakages have turned out to be one of the most frequent malfunctions in liquid pipeline distribution systems. In recent years, the issue has gained a lot of attention in research community due to associated financial costs, environmental hazards, and safety considerations. Wireless sensor network (WSN) based leakage detection and localization can provide an exceptional level of operational efficiency, safety assurance, and real-time parametric view of the entire pipeline network. In this paper, we propose a transient pressure wave based technique coupled with wavelet analysis to achieve reliable detection and localization of abrupt bursts and leakages. The presented technique uses the information carried in the transient pressure signal. A specific pattern is induced on the pressure traces within the pipeline due to leak; we use wavelet analysis to detect these local singularities. The proposed algorithm is distributed in nature and run on low power sensor nodes. The algorithm is deployed in field on a custom pipeline test bed and performance results are documented for various testing scenarios. A comparison of proposed wavelet technique with other widely used methods has been carried out. The technique provides more than 90% accuracy in a number of deployment scenarios for high noise generating long pipeline networks. Sidra Rashid, Saad Qaisar, Husnain Saeed, and Emad Felemban Copyright © 2014 Sidra Rashid et al. All rights reserved. Proximity-Based Robust Event Detection in Wireless Sensor Networks Tue, 22 Jul 2014 06:14:00 +0000 This paper presents a proximity-based event detection scheme for wireless sensor networks. It is a hybrid scheme in the sense that it takes advantage of both neighbor-based and cluster-based schemes in distinguishing events from false alarms due to faulty nodes. It gives more weights to alarms in closer proximity, while making event decisions at the cluster heads to reduce the communication overhead. The proposed scheme can effectively reduce false alarms while accurately detecting events even for a relatively small event region. Simulation results show that it greatly lessens the tradeoff between event detection accuracy and false alarm rate. Further improvements in performance can be made by removing identified faulty nodes from the network during normal operation. Chan-O Hong and Yoon-Hwa Choi Copyright © 2014 Chan-O Hong and Yoon-Hwa Choi. All rights reserved. A Survey on Three-Dimensional Wireless Ad Hoc and Sensor Networks Mon, 21 Jul 2014 07:50:21 +0000 In parallel with steady research and development in ad hoc and wireless sensor networks, many testbeds have been implemented and deployed in real world. Furthermore, some research works have addressed design issues for deployment in three-dimensional space such as sky or ocean. Since many research challenges in three-dimensional spaces have not been explored yet as much as two dimensional spaces, it is required to define the challenging tasks to provide reliable communication in three-dimensional space. In this survey, we aim to identify the unique properties of communication environments in three-dimensional space and address the overview of the state of the art in this research area. To achieve this, the survey is organized according to two good example networks, airborne ad hoc networks (AANETs) and underwater wireless sensor networks (UWSNs). For each network, we introduce and review the related research works to focus on infrastructure, localization, topology design, and position-based routing. Finally, open research issues are also discussed and presented. Babar Shah and Ki-Il Kim Copyright © 2014 Babar Shah and Ki-Il Kim. All rights reserved. Does Human Finger’s Pressure Sensing Improve User Text Input on Mobile Device? A Study on Input Performance Improvement Based on Human Finger’s Pressure on Mobile Device Mon, 21 Jul 2014 00:00:00 +0000 This paper introduces a pressure-sensitive text input system that provides an easier and faster method for entering Korean in the rapidly expanding smartphone environment. In order to evaluate the effectiveness of the proposed system, a pressure-sensitive text input system is implemented and three Korean input experiments are conducted on mobile phones from the two largest manufacturers in South Korea (Samsung and LG). Whereas conventional Korean input methods used in Samsung and LG mobile phones require multiple touches for entering characters such as double consonants and diphthongs, the pressure-sensitive text input method allows the user to enter them with a single touch. Experimental results confirm that the proposed pressure-sensitive Korean input method was effective in reducing the number of touches required for entering consonants for Samsung’s text input method (47% reduction) and for entering vowels for LG’s text input method (20% reduction). Yoon Sang Kim and Junho Ko Copyright © 2014 Yoon Sang Kim and Junho Ko. All rights reserved. Adaptive Heterogeneous Network Handoff of Smartphone Based on the Closed Control Loop Sun, 20 Jul 2014 12:03:36 +0000 Owing to complementary characteristics of wireless networks, it is deserved to achieve automatic handoff on the modern smartphone for taking full exploitation of these accessible technologies. In this paper, we have proposed the closed loop model on smartphone switching heterogeneous wireless networks, which is full-client based without requiring additional support from the access points or gateways and modification of the network protocols. It only intuitively takes advantage of user scheme as the feedback adjustment approach to handoff policy. Furthermore, we have analyzed the closed loop handoff model to illustrate and evaluate how the user feedback of the policy acts on adapting to change context. In the experiment, we have evaluated four metrics on the closed loop handoff policy in real smartphone device: performance, energy saving, data offloading, and user experience. Wei Liu, Qiang Li, Yongle Chen, Yongping Xiong, Yubo Deng, and Limin Sun Copyright © 2014 Wei Liu et al. All rights reserved. Recognizing Boundaries in Wireless Sensor Networks Based on Local Connectivity Information Sun, 20 Jul 2014 07:19:18 +0000 This paper develops an efficient and distributed boundary detection algorithm to precisely recognize wireless sensor network (WSN) boundaries using only local connectivity information. Specifically, given any node in a WSN, the proposed algorithm constructs its 2-hop isocontour and locally makes a rough decision on whether this node is suspected to be on boundaries of the WSN by examining the associated 2-hop isocontour. Then, a heuristic operation is performed to refine this decision, with the result that the suspected boundary node set is significantly shrunk. Lastly, tight boundary cycles corresponding to both inner and outer WSN boundaries are derived by searching the suspected boundary node set. Furthermore, regarding WSNs with relatively low node densities, the proposed algorithm is adapted to improve the quality of boundary detection. Even though the proposed algorithm is initially presented under the assumption of the idealized unit disk graph (UDG) model, we further consider the more realistic quasi-UDG (QUDG) model. In addition, a message complexity analysis confirms the energy efficiency of the proposed algorithm. Finally, we carry out a thorough evaluation showing that our algorithm is applicable to both dense and sparse deployments of WSNs and is able to produce accurate results. Baoqi Huang, Wei Wu, Guanglai Gao, and Tao Zhang Copyright © 2014 Baoqi Huang et al. All rights reserved. iAMCTD: Improved Adaptive Mobility of Courier Nodes in Threshold-Optimized DBR Protocol for Underwater Wireless Sensor Networks Sun, 20 Jul 2014 00:00:00 +0000 We propose forwarding-function () based routing protocol for underwater sensor networks (UWSNs): improved adaptive mobility of courier nodes in threshold-optimized depth-based-routing (iAMCTD). Unlike existing depth-based acoustic protocols, the proposed protocol exploits network density for time-critical applications. In order to tackle flooding, path loss, and propagation latency, we calculate optimal holding time () and use routing metrics: localization-free signal-to-noise ratio (LSNR), signal quality index (SQI), energy cost function (ECF), and depth-dependent function (DDF). Our proposal provides on-demand routing by formulating hard threshold (), soft threshold (), and prime energy limit (). Simulation results verify effectiveness and efficiency of the proposed iAMCTD. N. Javaid, M. R. Jafri, Z. A. Khan, U. Qasim, T. A. Alghamdi, and M. Ali Copyright © 2014 N. Javaid et al. All rights reserved. Solar Energy Harvesting and Management in Wireless Sensor Networks Sun, 20 Jul 2014 00:00:00 +0000 Wireless networks comprise of small devices that are typically deployed in environments where paucity of energy seriously restricts essential operations. The energy source of these devices decreases very quickly during continuous operation and it is pivotal to replace or recharge frequently the power sources. Sometimes, it is very difficult to perform these functions through conventional methods. One attractive solution to this problem is the use of the energy, scattered around us in the environment. The availability of energy from the environment is random and uncertain. In this paper, we present a model, schematically and analytically, for solar energy harvesting with appropriate energy management. We provide analysis and simulations for a solar cell for standard and different irradiance levels. The power of the storage device is also simulated for different times of the day. The proposed model not only scavenges the energy but also assures the connectivity of the network by optimizing the energy consumption. Muhammad Mazhar Abbas, Mohamed A. Tawhid, Khalid Saleem, Zia Muhammad, Nazar Abbas Saqib, Hafiz Malik, and Hasan Mahmood Copyright © 2014 Muhammad Mazhar Abbas et al. All rights reserved.