http://www.mdpi.com/journal/sensors/special_issues/wsn-advanced-computer-science/ Dear Colleagues, Wireless sensor networks (WSNs) are commonly used in pervasive and ubiquitous applications. WSNs are developed using both static (motes) and mobile (e.g. smart phone) sensor nodes for various applications such as smart homes, telehealth, surveillance, metering, and industry automation. In this special issue, we invite researchers and practitioners to submit their latest results and developments for the following topics: Applications using mobile phones and static sensors Algorithms and techniques for energy efficient communication Robustness and fault tolerance in WSNs Intelligent techniques and datamining for WSNs Query processing for data streams in WSNs Security and privacy issues in WSNs Telehealth services for elderly and chronic patients using WSNs Body area sensor networks Prof. Dr. Jong Hyuk Park Dr. Sajid Hussain Guest Editors{snippet name="submission_info"} http://www.mdpi.com/1424-8220/11/3/2899/ Fire hazard monitoring and evacuation for building environments is a novel application area for the deployment of wireless sensor networks. In this context, adaptive routing is essential in order to ensure safe and timely data delivery in building evacuation and fire fighting resource applications. Existing routing mechanisms for wireless sensor networks are not well suited for building fires, especially as they do not consider critical and dynamic network scenarios. In this paper, an emergency-adaptive, real-time and robust routing protocol is presented for emergency situations such as building fire hazard applications. The protocol adapts to handle dynamic emergency scenarios and works well with the routing hole problem. Theoretical analysis and simulation results indicate that our protocol provides a real-time routing mechanism that is well suited for dynamic emergency scenarios in building fires when compared with other related work. http://www.mdpi.com/1424-8220/11/3/2899/ Fri, 04 Mar 2011 00:00:00 CET Sensors 2011-03-04 11 3 Article 2899 2919 1424-8220 An Emergency-Adaptive Routing Scheme for Wireless Sensor Networks for Building Fire Hazard Monitoring 2011-03-04 doi: 10.3390/s110302899 Yuanyuan Zeng Cormac J. Sreenan Lanny Sitanayah Naixue Xiong Jong Hyuk Park Guilin Zheng http://www.mdpi.com/1424-8220/10/9/8375/ Wireless sensor networks (WSNs) generally have a many-to-one structure so that event information flows from sensors to a unique sink. In recent WSN applications, many-to-many structures evolved due to the need for conveying collected event information to multiple sinks. Privacy preserved data collection models in the literature do not solve the problems of WSN applications in which network has multiple un-trusted sinks with different level of privacy requirements. This study proposes a data collection framework bases on k-anonymity for preventing record disclosure of collected event information in WSNs. Proposed method takes the anonymity requirements of multiple sinks into consideration by providing different levels of privacy for each destination sink. Attributes, which may identify an event owner, are generalized or encrypted in order to meet the different anonymity requirements of sinks at the same anonymized output. If the same output is formed, it can be multicasted to all sinks. The other trivial solution is to produce different anonymized outputs for each sink and send them to related sinks. Multicasting is an energy efficient data sending alternative for some sensor nodes. Since minimization of energy consumption is an important design criteria for WSNs, multicasting the same event information to multiple sinks reduces the energy consumption of overall network. http://www.mdpi.com/1424-8220/10/9/8375/ Wed, 08 Sep 2010 00:00:00 CEST Sensors 2010-09-08 10 9 Article 8375 8397 1424-8220 Data Collection Framework for Energy Efficient Privacy Preservation in Wireless Sensor Networks Having Many-to-Many Structures 2010-09-08 doi: 10.3390/s100908375 Hayretdin Bahsi Albert Levi http://www.mdpi.com/1424-8220/10/8/7236/ Wireless Sensor Networks (WSNs) are being deployed in very diverse application scenarios, including rural and forest environments. In these particular contexts, specimen protection and conservation is a challenge, especially in natural reserves, dangerous locations or hot spots of these reserves (i.e., roads, railways, and other civil infrastructures). This paper proposes and studies a WSN based system for generic target (animal) tracking in the surrounding area of wildlife passages built to establish safe ways for animals to cross transportation infrastructures. In addition, it allows target identification through the use of video sensors connected to strategically deployed nodes. This deployment is designed on the basis of the IEEE 802.15.4 standard, but it increases the lifetime of the nodes through an appropriate scheduling. The system has been evaluated for the particular scenario of wildlife monitoring in passages across roads. For this purpose, different schemes have been simulated in order to find the most appropriate network operational parameters. Moreover, a novel prototype, provided with motion detector sensors, has also been developed and its design feasibility demonstrated. Original software modules providing new functionalities have been implemented and included in this prototype. Finally, main performance evaluation results of the whole system are presented and discussed in depth. http://www.mdpi.com/1424-8220/10/8/7236/ Tue, 03 Aug 2010 00:00:00 CEST Sensors 2010-08-03 10 8 Article 7236 7262 1424-8220 Wireless Sensor Network Deployment for Monitoring Wildlife Passages 2010-08-03 doi: 10.3390/s100807236 Antonio-Javier Garcia-Sanchez Felipe Garcia-Sanchez Fernando Losilla Pawel Kulakowski Joan Garcia-Haro Alejandro Rodríguez José-Vicente López-Bao Francisco Palomares http://www.mdpi.com/1424-8220/10/6/5899/ Localization is one of the most fundamental problems in wireless sensor networks, since the locations of the sensor nodes are critical to both network operations and most application level tasks. A GPS-free localization scheme for wireless sensor networks is presented in this paper. First, we develop a standardized clustering-based approach for the local coordinate system formation wherein a multiplication factor is introduced to regulate the number of master and slave nodes and the degree of connectivity among master nodes. Second, using homogeneous coordinates, we derive a transformation matrix between two Cartesian coordinate systems to efficiently merge them into a global coordinate system and effectively overcome the flip ambiguity problem. The algorithm operates asynchronously without a centralized controller; and does not require that the location of the sensors be known a priori. A set of parameter-setting guidelines for the proposed algorithm is derived based on a probability model and the energy requirements are also investigated. A simulation analysis on a specific numerical example is conducted to validate the mathematical analytical results. We also compare the performance of the proposed algorithm under a variety multiplication factor, node density and node communication radius scenario. Experiments show that our algorithm outperforms existing mechanisms in terms of accuracy and convergence time. http://www.mdpi.com/1424-8220/10/6/5899/ Wed, 09 Jun 2010 00:00:00 CEST Sensors 2010-06-09 10 6 Article 5899 5926 1424-8220 GPS-Free Localization Algorithm for Wireless Sensor Networks 2010-06-09 doi: 10.3390/s100605899 Wang Xu http://www.mdpi.com/1424-8220/10/6/5809/ In this paper four wireless sensor network operating systems are compared in terms of power consumption. The analysis takes into account the most common operating systems—TinyOS v1.0, TinyOS v2.0, Mantis and Contiki—running on Tmote Sky and MICAz devices. With the objective of ensuring a fair evaluation, a benchmark composed of four applications has been developed, covering the most typical tasks that a Wireless Sensor Network performs. The results show the instant and average current consumption of the devices during the execution of these applications. The experimental measurements provide a good insight into the power mode in which the device components are running at every moment, and they can be used to compare the performance of different operating systems executing the same tasks. http://www.mdpi.com/1424-8220/10/6/5809/ Tue, 08 Jun 2010 00:00:00 CEST Sensors 2010-06-08 10 6 Article 5809 5826 1424-8220 Power Consumption Analysis of Operating Systems for Wireless Sensor Networks 2010-06-08 doi: 10.3390/s100605809 Lajara Pelegrí-Sebastiá Solano http://www.mdpi.com/1424-8220/10/6/5569/ In sensor network, energy conservation is one of the most critical issues since sensor nodes should perform a sensing task for a long time (e.g., lasting a few years) but the battery of them cannot be replaced in most practical situations. For this purpose, numerous energy conservation schemes have been proposed and duty cycling scheme is considered the most suitable power conservation technique, where sensor nodes alternate between states having different levels of power consumption. In order to analyze the energy consumption of energy conservation scheme based on duty cycling, it is essential to obtain the probability of each state. In this paper, we analytically derive steady state probability of sensor node states, i.e., sleep, listen, and active states, based on traffic characteristics and timer values, i.e., sleep timer, listen timer, and active timer. The effect of traffic characteristics and timer values on the steady state probability and energy consumption is analyzed in detail. Our work can provide sensor network operators guideline for selecting appropriate timer values for efficient energy conservation. The analytical methodology developed in this paper can be extended to other energy conservation schemes based on duty cycling with different sensor node states, without much difficulty. http://www.mdpi.com/1424-8220/10/6/5569/ Thu, 03 Jun 2010 00:00:00 CEST Sensors 2010-06-03 10 6 Article 5569 5589 1424-8220 Modeling and Analysis of Energy Conservation Scheme Based on Duty Cycling in Wireless Ad Hoc Sensor Network 2010-06-03 doi: 10.3390/s100605569 Chung Hwang http://www.mdpi.com/1424-8220/10/6/5548/ We introduce an energy-efficient Rate Adaptive Media Access Control (RA-MAC) algorithm for long-lived Wireless Sensor Networks (WSNs). Previous research shows that the dynamic and lossy nature of wireless communications is one of the major challenges to reliable data delivery in WSNs. RA-MAC achieves high link reliability in such situations by dynamically trading off data rate for channel gain. The extra gain that can be achieved reduces the packet loss rate which contributes to reduced energy expenditure through a reduced numbers of retransmissions. We achieve this at the expense of raw bit rate which generally far exceeds the application’s link requirement. To minimize communication energy consumption, RA-MAC selects the optimal data rate based on the estimated link quality at each data rate and an analytical model of the energy consumption. Our model shows how the selected data rate depends on different channel conditions in order to minimize energy consumption. We have implemented RA-MAC in TinyOS for an off-the-shelf sensor platform (the TinyNode) on top of a state-of-the-art WSN Media Access Control Protocol, SCP-MAC, and evaluated its performance by comparing our implementation with the original SCP-MAC using both simulation and experiment. http://www.mdpi.com/1424-8220/10/6/5548/ Wed, 02 Jun 2010 00:00:00 CEST Sensors 2010-06-02 10 6 Article 5548 5568 1424-8220 An Energy-efficient Rate Adaptive Media Access Protocol (RA-MAC) for Long-lived Sensor Networks 2010-06-02 doi: 10.3390/s100605548 Hu Chen Corke O’Rourke http://www.mdpi.com/1424-8220/10/6/5503/ The Wireless Personal Area Network (WPAN) is one of the fledging paradigms that the next generation of wireless systems is sprouting towards. Among them, a more specific category is the Wireless Body Area Network (WBAN) used for health monitoring. On the other hand, Ultra-Wideband (UWB) comes with a number of desirable features at the physical layer for wireless communications. One big challenge in adoption of UWB in WBAN is the fact that signals get attenuated exponentially. Due to the intrinsic structural complexity in human body, electromagnetic waves show a profound variation during propagation through it. The reflection and transmission coefficients of human body are highly dependent upon the dielectric constants as well as upon the frequency. The difference in structural materials such as fat, muscles and blood essentially makes electromagnetic wave attenuation to be different along the way. Thus, a complete characterization of body channel is a challenging task. The connection between attenuation and frequency of the signal makes the investigation of UWB in WBAN an interesting proposition. In this paper, we study analytically the impact of body channels on electromagnetic signal propagation with reference to UWB. In the process, scattering, reflectivity and transmitivity have been addressed with analysis of approximate layer-wise modeling, and with numerical depictions. Pulses with Gaussian profile have been employed in our analysis. It shows that, under reasonable practical approximations, the human body channel can be modeled in layers so as to have the effects of total reflections or total transmissions in certain frequency bands. This could help decide such design issues as antenna characteristics of implant devices for WBAN employing UWB. http://www.mdpi.com/1424-8220/10/6/5503/ Wed, 02 Jun 2010 00:00:00 CEST Sensors 2010-06-02 10 6 Article 5503 5529 1424-8220 Studies of Scattering, Reflectivity, and Transmitivity in WBAN Channel: Feasibility of Using UWB 2010-06-02 doi: 10.3390/s100605503 Kabir Ashrafuzzaman Chowdhury Kwak http://www.mdpi.com/1424-8220/10/6/5443/ Battery consumption is a key aspect in the performance of wireless sensor networks. One of the most promising technologies for this type of networks is 802.15.4/ZigBee. This paper presents an empirical characterization of battery consumption in commercial 802.15.4/ZigBee motes. This characterization is based on the measurement of the current that is drained from the power source under different 802.15.4 communication operations. The measurements permit the definition of an analytical model to predict the maximum, minimum and mean expected battery lifetime of a sensor networking application as a function of the sensor duty cycle and the size of the sensed data. http://www.mdpi.com/1424-8220/10/6/5443/ Tue, 01 Jun 2010 00:00:00 CEST Sensors 2010-06-01 10 6 Article 5443 5468 1424-8220 Modeling of Current Consumption in 802.15.4/ZigBee Sensor Motes 2010-06-01 doi: 10.3390/s100605443 Casilari Cano-García Campos-Garrido http://www.mdpi.com/1424-8220/10/5/5233/ Future Wireless Sensor Networks (WSNs) will be ubiquitous, large-scale networks interconnected with the existing IP infrastructure. Autonomic functionalities have to be designed in order to reduce the complexity of their operation and management, and support the dissemination of knowledge within a WSN. In this paper a novel protocol for energy efficient deployment, clustering and routing in WSNs is proposed that focuses on the incorporation of autonomic functionalities in the existing approaches. The design of the protocol facilitates the design of innovative applications and services that are based on overlay topologies created through cooperation among the sensor nodes. http://www.mdpi.com/1424-8220/10/5/5233/ Tue, 25 May 2010 00:00:00 CEST Sensors 2010-05-25 10 5 Article 5233 5262 1424-8220 NEURON: Enabling Autonomicity in Wireless Sensor Networks 2010-05-25 doi: 10.3390/s100505233 Zafeiropoulos Gouvas Liakopoulos Mentzas Mitrou http://www.mdpi.com/1424-8220/10/5/5171/ Accurate and low-cost autonomous self-localization is a critical requirement of various applications of a large-scale distributed wireless sensor network (WSN). Due to its massive deployment of sensors, explicit measurements based on specialized localization hardware such as the Global Positioning System (GPS) is not practical. In this paper, we propose a low-cost WSN localization solution. Our design uses received signal strength indicators for ranging, light weight distributed algorithms based on the spring-relaxation technique for location computation, and the cooperative approach to achieve certain location estimation accuracy with a low number of nodes with known locations. We provide analysis to show the suitability of the spring-relaxation technique for WSN localization with cooperative approach, and perform simulation experiments to illustrate its accuracy in localization. http://www.mdpi.com/1424-8220/10/5/5171/ Tue, 25 May 2010 00:00:00 CEST Sensors 2010-05-25 10 5 Review 5171 5192 1424-8220 Location Estimation in Wireless Sensor Networks Using Spring-Relaxation Technique 2010-05-25 doi: 10.3390/s100505171 Zhang Foh Seet Fong http://www.mdpi.com/1424-8220/10/5/4577/ Many wireless sensor network (WSN) applications require privacy-preserving aggregation of sensor data during transmission from the source nodes to the sink node. In this paper, we explore several existing privacy-preserving data aggregation (PPDA) protocols for WSNs in order to provide some insights on their current status. For this, we evaluate the PPDA protocols on the basis of such metrics as communication and computation costs in order to demonstrate their potential for supporting privacy-preserving data aggregation in WSNs. In addition, based on the existing research, we enumerate some important future research directions in the field of privacy-preserving data aggregation for WSNs. http://www.mdpi.com/1424-8220/10/5/4577/ Tue, 04 May 2010 00:00:00 CEST Sensors 2010-05-04 10 5 Review 4577 4601 1424-8220 Privacy-Preserving Data Aggregation Protocols for Wireless Sensor Networks: A Survey 2010-05-04 doi: 10.3390/s100504577 Bista Chang http://www.mdpi.com/1424-8220/10/5/4521/ For monitoring burst events in a kind of reactive wireless sensor networks (WSNs), a multipath routing protocol (MRP) based on dynamic clustering and ant colony optimization (ACO) is proposed.. Such an approach can maximize the network lifetime and reduce the energy consumption. An important attribute of WSNs is their limited power supply, and therefore some metrics (such as energy consumption of communication among nodes, residual energy, path length) were considered as very important criteria while designing routing in the MRP. Firstly, a cluster head (CH) is selected among nodes located in the event area according to some parameters, such as residual energy. Secondly, an improved ACO algorithm is applied in the search for multiple paths between the CH and sink node. Finally, the CH dynamically chooses a route to transmit data with a probability that depends on many path metrics, such as energy consumption. The simulation results show that MRP can prolong the network lifetime, as well as balance of energy consumption among nodes and reduce the average energy consumption effectively. http://www.mdpi.com/1424-8220/10/5/4521/ Tue, 04 May 2010 00:00:00 CEST Sensors 2010-05-04 10 5 Article 4521 4540 1424-8220 A Multipath Routing Protocol Based on Clustering and Ant Colony Optimization for Wireless Sensor Networks 2010-05-04 doi: 10.3390/s100504521 Yang Xu Zhao Xu http://www.mdpi.com/1424-8220/10/5/4410/ Mobility of sensor node in Wireless Sensor Networks (WSN) brings security issues such as re-authentication and tracing the node movement. However, current security researches on WSN are insufficient to support such environments since their designs only considered the static environments. In this paper, we propose the efficient node authentication and key exchange protocol that reduces the overhead in node re-authentication and also provides untraceability of mobile nodes. Compared with previous protocols, our protocol has only a third of communication and computational overhead. We expect our protocol to be the efficient solution that increases the lifetime of sensor network. http://www.mdpi.com/1424-8220/10/5/4410/ Fri, 30 Apr 2010 00:00:00 CEST Sensors 2010-04-30 10 5 Article 4410 4429 1424-8220 Untraceable Mobile Node Authentication in WSN 2010-04-30 doi: 10.3390/s100504410 Han Kim Shon http://www.mdpi.com/1424-8220/10/4/3934/ Diabetes is difficult to control and it is important to manage the diabetic’s blood sugar level and prevent the associated complications by appropriate diabetic treatment. This paper proposes a system that can provide appropriate management for diabetes patients, according to their blood sugar level. The system is designed to send the information about the blood sugar levels, blood pressure, food consumption, exercise, etc., of diabetes patients, and manage the treatment by recommending and monitoring food consumption, physical activity, insulin dosage, etc., so that the patient can better manage their condition. The system is based on rules and the K Nearest Neighbor (KNN) classifier algorithm, to obtain the optimum treatment recommendation. Also, a monitoring system for diabetes patients is implemented using Web Services and Personal Digital Assistant (PDA) programming. http://www.mdpi.com/1424-8220/10/4/3934/ Mon, 19 Apr 2010 00:00:00 CEST Sensors 2010-04-19 10 4 Article 3934 3953 1424-8220 A Monitoring and Advisory System for Diabetes Patient Management Using a Rule-Based Method and KNN 2010-04-19 doi: 10.3390/s100403934 Lee Gatton Lee http://www.mdpi.com/1424-8220/10/4/3718/ When a sensor node roams within a very large and distributed wireless sensor network, which consists of numerous sensor nodes, its routing path and neighborhood keep changing. In order to provide a high level of security in this environment, the moving sensor node needs to be authenticated to new neighboring nodes and a key established for secure communication. The paper proposes an efficient and scalable protocol to establish and update the authentication key in a dynamic wireless sensor network environment. The protocol guarantees that two sensor nodes share at least one key with probability 1 (100%) with less memory and energy cost, while not causing considerable communication overhead. http://www.mdpi.com/1424-8220/10/4/3718/ Tue, 13 Apr 2010 00:00:00 CEST Sensors 2010-04-13 10 4 Article 3718 3731 1424-8220 Authentication and Key Establishment in Dynamic Wireless Sensor Networks 2010-04-13 doi: 10.3390/s100403718 Qiu Zhou Baek Lopez http://www.mdpi.com/1424-8220/10/4/3626/ To successfully realize the ubiquitous network environment including home automation or industrial control systems, it is important to be able to resist a jamming attack. This has recently been considered as an extremely threatening attack because it can collapse the entire network, despite the existence of basic security protocols such as encryption and authentication. In this paper, we present a method of jamming attack tolerant routing using multiple paths based on zones. The proposed scheme divides the network into zones, and manages the candidate forward nodes of neighbor zones. After detecting an attack, detour nodes decide zones for rerouting, and detour packets destined for victim nodes through forward nodes in the decided zones. Simulation results show that our scheme increases the PDR (Packet Delivery Ratio) and decreases the delay significantly in comparison with rerouting by a general routing protocol on sensor networks, AODV (Ad hoc On Demand Distance Vector), and a conventional JAM (Jammed Area Mapping) service with one reroute. http://www.mdpi.com/1424-8220/10/4/3626/ Mon, 12 Apr 2010 00:00:00 CEST Sensors 2010-04-12 10 4 Article 3626 3640 1424-8220 DMP: Detouring Using Multiple Paths against Jamming Attack for Ubiquitous Networking System 2010-04-12 doi: 10.3390/s100403626 Kim Chae http://www.mdpi.com/1424-8220/10/4/3444/ The proposed mechanism for jamming attack detection for wireless sensor networks is novel in three respects: firstly, it upgrades the jammer to include versatile military jammers; secondly, it graduates from the existing node-centric detection system to the network-centric system making it robust and economical at the nodes, and thirdly, it tackles the problem through fuzzy inference system, as the decision regarding intensity of jamming is seldom crisp. The system with its high robustness, ability to grade nodes with jamming indices, and its true-detection rate as high as 99.8%, is worthy of consideration for information warfare defense purposes. http://www.mdpi.com/1424-8220/10/4/3444/ Thu, 08 Apr 2010 00:00:00 CEST Sensors 2010-04-08 10 4 Article 3444 3479 1424-8220 Information Warfare-Worthy Jamming Attack Detection Mechanism for Wireless Sensor Networks Using a Fuzzy Inference System 2010-04-08 doi: 10.3390/s100403444 Misra Singh Mohan http://www.mdpi.com/1424-8220/10/4/3145/ Wireless multimedia sensor nodes sense areas that are uncorrelated to the areas covered by radio neighbouring sensors. Thus, node clustering for coordinating multimedia sensing and processing cannot be based on classical sensor clustering algorithms. This paper presents a clustering mechanism for Wireless Multimedia Sensor Networks (WMSNs) based on overlapped Field of View (FoV) areas. Overlapping FoVs in dense networks cause the wasting of power due to redundant area sensing. The main aim of the proposed clustering method is energy conservation and network lifetime prolongation. This objective is achieved through coordination of nodes belonging to the same cluster to perform assigned tasks in a cooperative manner avoiding redundant sensing or processing. A paradigm in this concept, a cooperative scheduling scheme for object detection, is presented based on the proposed clustering method. http://www.mdpi.com/1424-8220/10/4/3145/ Wed, 31 Mar 2010 00:00:00 CEST Sensors 2010-03-31 10 4 Article 3145 3169 1424-8220 A Method for Clustering and Cooperation in Wireless Multimedia Sensor Networks 2010-03-31 doi: 10.3390/s100403145 Alaei Barcelo-Ordinas http://www.mdpi.com/1424-8220/10/4/3100/ Wireless sensor networks involve a large number of sensor nodes with limited energy supply, which impacts the behavior of their application. In wireless multimedia sensor networks, sensor nodes are equipped with audio and visual information collection modules. Multimedia contents are ubiquitously retrieved in surveillance applications. To solve the energy problems during target surveillance with wireless multimedia sensor networks, an energy-aware sensor scheduling method is proposed in this paper. Sensor nodes which acquire acoustic signals are deployed randomly in the sensing fields. Target localization is based on the signal energy feature provided by multiple sensor nodes, employing particle swarm optimization (PSO). During the target surveillance procedure, sensor nodes are adaptively grouped in a totally distributed manner. Specially, the target motion information is extracted by a forecasting algorithm, which is based on the hidden Markov model (HMM). The forecasting results are utilized to awaken sensor node in the vicinity of future target position. According to the two properties, signal energy feature and residual energy, the sensor nodes decide whether to participate in target detection separately with a fuzzy control approach. Meanwhile, the local routing scheme of data transmission towards the observer is discussed. Experimental results demonstrate the efficiency of energy-aware scheduling of surveillance in wireless multimedia sensor network, where significant energy saving is achieved by the sensor awakening approach and data transmission paths are calculated with low computational complexity. http://www.mdpi.com/1424-8220/10/4/3100/ Wed, 31 Mar 2010 00:00:00 CEST Sensors 2010-03-31 10 4 Article 3100 3125 1424-8220 Energy-aware Scheduling of Surveillance in Wireless Multimedia Sensor Networks 2010-03-31 doi: 10.3390/s100403100 Wang Wang Ma Sun http://www.mdpi.com/1424-8220/10/4/3023/ This paper surveys the most relevant works of Data Centric Storage (DCS) for Wireless Sensor Networks. DCS is a research area that covers data dissemination and storage inside an ad-hoc sensor network. In addition, we present a Quadratic Adaptive Replication (QAR) scheme for DCS, which is a more adaptive multi-replication DCS system and outperforms previous proposals in the literature by reducing the overall network traffic that has a direct impact on energy consumption. Finally, we discuss the open research challenges for DCS. http://www.mdpi.com/1424-8220/10/4/3023/ Tue, 30 Mar 2010 00:00:00 CEST Sensors 2010-03-30 10 4 Article 3023 3056 1424-8220 Data Centric Storage Technologies: Analysis and Enhancement 2010-03-30 doi: 10.3390/s100403023 Rumín Pascual Ortega López http://www.mdpi.com/1424-8220/10/4/2957/ In order to provide the seamless navigation and positioning services for indoor environments, an indoor location based service (LBS) test bed is developed to integrate the indoor positioning system and the indoor three-dimensional (3D) geographic information system (GIS). A wireless sensor network (WSN) is used in the developed indoor positioning system. Considering the power consumption, in this paper the ZigBee radio is used as the wireless protocol, and the received signal strength (RSS) fingerprinting positioning method is applied as the primary indoor positioning algorithm. The matching processes of the user location include the nearest neighbor (NN) algorithm, the K-weighted nearest neighbors (KWNN) algorithm, and the probabilistic approach. To enhance the positioning accuracy for the dynamic user, the particle filter is used to improve the positioning performance. As part of this research, a 3D indoor GIS is developed to be used with the indoor positioning system. This involved using the computer-aided design (CAD) software and the virtual reality markup language (VRML) to implement a prototype indoor LBS test bed. Thus, a rapid and practical procedure for constructing a 3D indoor GIS is proposed, and this GIS is easy to update and maintenance for users. The building of the Department of Aeronautics and Astronautics at National Cheng Kung University in Taiwan is used as an example to assess the performance of various algorithms for the indoor positioning system. http://www.mdpi.com/1424-8220/10/4/2957/ Tue, 30 Mar 2010 00:00:00 CEST Sensors 2010-03-30 10 4 Article 2957 2974 1424-8220 Development of an Indoor Location Based Service Test Bed and Geographic Information System with a Wireless Sensor Network 2010-03-30 doi: 10.3390/s100402957 Jan Hsu Tsai http://www.mdpi.com/1424-8220/10/4/2821/ The wireless personal area network (WPAN) is an emerging wireless technology for future short range indoor and outdoor communication applications. The IEEE 802.15.3 medium access control (MAC) is proposed to coordinate the access to the wireless medium among the competing devices, especially for short range and high data rate applications in home networks. In this paper we use analytical modeling to study the performance analysis of WPAN (IEEE 802.15.3) MAC in terms of throughput, efficient bandwidth utilization, and delay with various ACK policies under error channel condition. This allows us to introduce a K-Dly-ACK-AGG policy, payload size adjustment mechanism, and Improved Backoff algorithm to improve the performance of the WPAN MAC. Performance evaluation results demonstrate the impact of our improvements on network capacity. Moreover, these results can be very useful to WPAN application designers and protocol architects to easily and correctly implement WPAN for home networking. http://www.mdpi.com/1424-8220/10/4/2821/ Mon, 29 Mar 2010 00:00:00 CEST Sensors 2010-03-29 10 4 Article 2821 2842 1424-8220 Performance Analysis and Improvement of WPAN MAC for Home Networks 2010-03-29 doi: 10.3390/s100402821 Mehta Kwak http://www.mdpi.com/1424-8220/10/4/2793/ Recent studies have shown that in realistic wireless sensor network environments links are extremely unreliable. To recover from corrupted packets, most routing schemes with an assumption of ideal radio environments use a retransmission mechanism, which may cause unnecessary retransmissions. Therefore, guaranteeing energy-efficient reliable data transmission is a fundamental routing issue in wireless sensor networks. However, it is not encouraged to propose a new reliable routing scheme in the sense that every existing routing scheme cannot be replaced with the new one. This paper proposes a Distributed and Reliable Data Transmission (DRDT) scheme with a goal to efficiently guarantee reliable data transmission. In particular, this is based on a pluggable modular approach so that it can be extended to existing routing schemes. DRDT offers reliable data transmission using neighbor nodes, i.e., helper nodes. A helper node is selected among the neighbor nodes of the receiver node which overhear the data packet in a distributed manner. DRDT effectively reduces the number of retransmissions by delegating the retransmission task from the sender node to the helper node that has higher link quality to the receiver node when the data packet reception fails due to the low link quality between the sender and the receiver nodes. Comprehensive simulation results show that DRDT improves end-to-end transmission cost by up to about 45% and reduces its delay by about 40% compared to existing schemes. http://www.mdpi.com/1424-8220/10/4/2793/ Mon, 29 Mar 2010 00:00:00 CEST Sensors 2010-03-29 10 4 Article 2793 2811 1424-8220 DRDT: Distributed and Reliable Data Transmission with Cooperative Nodes for LossyWireless Sensor Networks 2010-03-29 doi: 10.3390/s100402793 Seo Kim Hur Choi Choo http://www.mdpi.com/1424-8220/10/4/2770/ An Unattended Wireless Sensor Network (UWSN) can be used in many applications to collect valuable data. Nevertheless, due to the unattended nature, the sensors could be compromised and the sensor readings would be maliciously altered so that the sink accepts the falsified sensor readings. Unfortunately, few attentions have been given to this authentication problem. Moreover, existing methods suffer from different kinds of DoS attacks such as Path-Based DoS (PDoS) and False Endorsement-based DoS (FEDoS) attacks. In this paper, a scheme, called AAD, is proposed to Acquire Authentic Data in UWSNs. We exploit the collaboration among sensors to address the authentication problem. With the proper design of the collaboration mechanism, AAD has superior resilience against sensor compromises, PDoS attack, and FEDoS attack. In addition, compared with prior works, AAD also has relatively low energy consumption. In particular, according to our simulation, in a network with 1, 000 sensors, the energy consumed by AAD is lower than 30% of that consumed by the existing method, ExCo. The analysis and simulation are also conducted to demonstrate the superiority of the proposed AAD scheme over the existing methods. http://www.mdpi.com/1424-8220/10/4/2770/ Fri, 26 Mar 2010 00:00:00 CET Sensors 2010-03-26 10 4 Article 2770 2792 1424-8220 Acquiring Authentic Data in Unattended Wireless Sensor Networks 2010-03-26 doi: 10.3390/s100402770 Yu Chen Lu Kuo Chao http://www.mdpi.com/1424-8220/10/4/2752/ This paper presents a medium access control and scheduling scheme for wireless sensor networks. It uses time trees for sending data from the sensor node to the base station. For an energy efficient operation of the sensor networks in a distributed manner, time trees are built in order to reduce the collision probability and to minimize the total energy required to send data to the base station. A time tree is a data gathering tree where the base station is the root and each sensor node is either a relaying or a leaf node of the tree. Each tree operates in a different time schedule with possibly different activation rates. Through the simulation, the proposed scheme that uses time trees shows better characteristics toward burst traffic than the previous energy and data arrival rate scheme. http://www.mdpi.com/1424-8220/10/4/2752/ Fri, 26 Mar 2010 00:00:00 CET Sensors 2010-03-26 10 4 Article 2752 2769 1424-8220 A Time Tree Medium Access Control for Energy Efficiency and Collision Avoidance in Wireless Sensor Networks 2010-03-26 doi: 10.3390/s100402752 Lee http://www.mdpi.com/1424-8220/10/3/2416/ In time-critical wireless sensor network (WSN) applications, a high degree of reliability is commonly required. A dynamical jumping real-time fault-tolerant routing protocol (DMRF) is proposed in this paper. Each node utilizes the remaining transmission time of the data packets and the state of the forwarding candidate node set to dynamically choose the next hop. Once node failure, network congestion or void region occurs, the transmission mode will switch to jumping transmission mode, which can reduce the transmission time delay, guaranteeing the data packets to be sent to the destination node within the specified time limit. By using feedback mechanism, each node dynamically adjusts the jumping probabilities to increase the ratio of successful transmission. Simulation results show that DMRF can not only efficiently reduce the effects of failure nodes, congestion and void region, but also yield higher ratio of successful transmission, smaller transmission delay and reduced number of control packets. http://www.mdpi.com/1424-8220/10/3/2416/ Tue, 23 Mar 2010 00:00:00 CET Sensors 2010-03-23 10 3 Article 2416 2437 1424-8220 Dynamical Jumping Real-Time Fault-Tolerant Routing Protocol for Wireless Sensor Networks 2010-03-23 doi: 10.3390/s100302416 Wu Lin Xia Yao Zhang Liu http://www.mdpi.com/1424-8220/10/3/2217/ Temperature in an urban area exhibits a complicated pattern due to complexity of infrastructure. Despite geographical proximity, structures of a group of buildings and streets affect changes in temperature. To investigate the pattern of fine-grained distribution of temperature, we installed a densely distributed sensor network called UScan. In this paper, we describe the system architecture of UScan as well as experience learned from installing 200 sensors in downtown Tokyo. The field experiment of UScan system operated for two months to collect long-term urban temperature data. To analyze the collected data in an efficient manner, we propose a lightweight clustering methodology to study the correlation between the pattern of temperature and various environmental factors including the amount of sunshine, the width of streets, and the existence of trees. The analysis reveals meaningful results and asserts the necessity of fine-grained deployment of sensors in an urban area. http://www.mdpi.com/1424-8220/10/3/2217/ Thu, 18 Mar 2010 00:00:00 CET Sensors 2010-03-18 10 3 Article 2217 2241 1424-8220 A Deployment of Fine-Grained Sensor Network and Empirical Analysis of Urban Temperature 2010-03-18 doi: 10.3390/s100302217 Thepvilojanapong Ono Tobe http://www.mdpi.com/1424-8220/10/3/2150/ Wireless Sensor Networks are presented as devices for signal sampling and reconstruction. Within this framework, the qualitative and quantitative influence of (i) signal granularity, (ii) spatial distribution of sensors, (iii) sensors clustering, and (iv) signal reconstruction procedure are assessed. This is done by defining an error metric and performing a Monte Carlo experiment. It is shown that all these factors have significant impact on the quality of the reconstructed signal. The extent of such impact is quantitatively assessed. http://www.mdpi.com/1424-8220/10/3/2150/ Tue, 16 Mar 2010 00:00:00 CET Sensors 2010-03-16 10 3 Article 2150 2168 1424-8220 Data Driven Performance Evaluation of Wireless Sensor Networks 2010-03-16 doi: 10.3390/s100302150 Frery Ramos Alencar-Neto Nakamura Loureiro http://www.mdpi.com/1424-8220/10/3/2003/ Due to the battery resource constraints, saving energy is a critical issue in wireless sensor networks, particularly in large sensor networks. One possible solution is to deploy multiple sink nodes simultaneously. Another possible solution is to employ an adaptive clustering hierarchy routing scheme. In this paper, we propose a multiple sink cluster wireless sensor networks scheme which combines the two solutions, and propose an efficient transmission power control scheme for a sink-centric cluster routing protocol in multiple sink wireless sensor networks, denoted as MSCWSNs-PC. It is a distributed, scalable, self-organizing, adaptive system, and the sensor nodes do not require knowledge of the global network and their location. All sinks effectively work out a representative view of a monitored region, after which power control is employed to optimize network topology. The simulations demonstrate the advantages of our new protocol. http://www.mdpi.com/1424-8220/10/3/2003/ Thu, 11 Mar 2010 00:00:00 CET Sensors 2010-03-11 10 3 Article 2003 2026 1424-8220 Distributed Power Allocation for Sink-Centric Clusters in Multiple Sink Wireless Sensor Networks 2010-03-11 doi: 10.3390/s100302003 Lei Cao Chen Xu Wei Shao Guoan Zhang Hui Zhou Qiang Sun Yuehua Guo http://www.mdpi.com/1424-8220/10/3/1619/ An extremely reliable source to sink communication is required for most of the contemporary WSN applications especially pertaining to military, healthcare and disaster-recovery. However, due to their intrinsic energy, bandwidth and computational constraints, Wireless Sensor Networks (WSNs) encounter several challenges in reliable source to sink communication. In this paper, we present a novel reliable topology that uses reliable hotlines between sensor gateways to boost the reliability of end-to-end transmissions. This reliable and efficient routing alternative reduces the number of average hops from source to the sink. We prove, with the help of analytical evaluation, that communication using hotlines is considerably more reliable than traditional WSN routing. We use reliability theory to analyze the cost and benefit of adding gateway nodes to a backbone-assisted WSN. However, in hotline assisted routing some scenarios where source and the sink are just a couple of hops away might bring more latency, therefore, we present a Signature Based Routing (SBR) scheme. SBR enables the gateways to make intelligent routing decisions, based upon the derived signature, hence providing lesser end-to-end delay between source to the sink communication. Finally, we evaluate our proposed hotline based topology with the help of a simulation tool and show that the proposed topology provides manifold increase in end-to-end reliability. http://www.mdpi.com/1424-8220/10/3/1619/ Mon, 01 Mar 2010 00:00:00 CET Sensors 2010-03-01 10 3 Article 1619 1651 1424-8220 An Enhanced Backbone-Assisted Reliable Framework for Wireless Sensor Networks 2010-03-01 doi: 10.3390/s100301619 Ali Tufail Syed Ali Khayam Muhammad Taqi Raza Amna Ali Ki-Hyung Kim http://www.mdpi.com/1424-8220/10/3/1486/ In the paper, we propose a reliable asynchronous image transfer protocol, RAIT. RAIT applies a double sliding window method to node-to-node transfer, with one sliding window for the receiving queue, which is used to prevent packet loss caused by communication failure between nodes, and another sliding window for the sending queue, which prevents packet loss caused by network congestion. The routing node prevents packet loss between nodes by preemptive scheduling of multiple packets for a given image. RAIT implements a double sliding window method by means of a cross-layer design between the RAIT layer, routing layer, and queue layer. We demonstrate that RAIT guarantees a higher reliability of image transmission compared to the existing protocols. http://www.mdpi.com/1424-8220/10/3/1486/ Fri, 26 Feb 2010 00:00:00 CET Sensors 2010-02-26 10 3 Article 1486 1510 1424-8220 Reliable Asynchronous Image Transfer Protocol in Wireless Multimedia Sensor Networks 2010-02-26 doi: 10.3390/s100301487 Joa-Hyoung Lee In-Bum Jung http://www.mdpi.com/1424-8220/10/3/1447/ Full network level privacy has often been categorized into four sub-categories: Identity, Route, Location and Data privacy. Achieving full network level privacy is a critical and challenging problem due to the constraints imposed by the sensor nodes (e.g., energy, memory and computation power), sensor networks (e.g., mobility and topology) and QoS issues (e.g., packet reach-ability and timeliness). In this paper, we proposed two new identity, route and location privacy algorithms and data privacy mechanism that addresses this problem. The proposed solutions provide additional trustworthiness and reliability at modest cost of memory and energy. Also, we proved that our proposed solutions provide protection against various privacy disclosure attacks, such as eavesdropping and hop-by-hop trace back attacks. http://www.mdpi.com/1424-8220/10/3/1447/ Fri, 26 Feb 2010 00:00:00 CET Sensors 2010-02-26 10 3 Article 1447 1472 1424-8220 Achieving Network Level Privacy in Wireless Sensor Networks 2010-02-26 doi: 10.3390/s100301447 Riaz Ahmed Shaikh Hassan Jameel Brian J. D’Auriol Heejo Lee Sungyoung Lee Young-Jae Song http://www.mdpi.com/1424-8220/10/2/1251/ This paper presents a secure decentralized clustering algorithm for wireless ad-hoc sensor networks. The algorithm operates without a centralized controller, operates asynchronously, and does not require that the location of the sensors be known a priori. Based on the cluster-based topology, secure hierarchical communication protocols and dynamic quarantine strategies are introduced to defend against spam attacks, since this type of attacks can exhaust the energy of sensor nodes and will shorten the lifetime of a sensor network drastically. By adjusting the threshold of infected percentage of the cluster coverage, our scheme can dynamically coordinate the proportion of the quarantine region and adaptively achieve the cluster control and the neighborhood control of attacks. Simulation results show that the proposed approach is feasible and cost effective for wireless sensor networks. http://www.mdpi.com/1424-8220/10/2/1251/ Wed, 03 Feb 2010 00:00:00 CET Sensors 2010-02-03 10 2 Article 1251 1278 1424-8220 Secure Adaptive Topology Control for Wireless Ad-Hoc Sensor Networks 2010-02-03 doi: 10.3390/s100201251 Ching-Tsung Hsueh Yu-Wei Li Chih-Yu Wen Yen-Chieh Ouyang http://www.mdpi.com/1424-8220/10/1/400/ In recent years, various received signal strength (RSS)-based localization estimation approaches for wireless sensor networks (WSNs) have been proposed. RSS-based localization is regarded as a low-cost solution for many location-aware applications in WSNs. In previous studies, the radiation patterns of all sensor nodes are assumed to be spherical, which is an oversimplification of the radio propagation model in practical applications. In this study, we present an RSS-based cooperative localization method that estimates unknown coordinates of sensor nodes in a network. Arrangement of two external low-cost omnidirectional dipole antennas is developed by using the distance-power gradient model. A modified robust regression is also proposed to determine the relative azimuth and distance between a sensor node and a fixed reference node. In addition, a cooperative localization scheme that incorporates estimations from multiple fixed reference nodes is presented to improve the accuracy of the localization. The proposed method is tested via computer-based analysis and field test. Experimental results demonstrate that the proposed low-cost method is a useful solution for localizing sensor nodes in unknown or changing environments. http://www.mdpi.com/1424-8220/10/1/400/ Wed, 06 Jan 2010 00:00:00 CET Sensors 2010-01-06 10 1 Article 400 427 1424-8220 Collaborative Localization in Wireless Sensor Networks via Pattern Recognition in Radio Irregularity Using Omnidirectional Antennas 2010-01-06 doi: 10.3390/s100100400 Joe-Air Jiang Cheng-Long Chuang Tzu-Shiang Lin Chia-Pang Chen Chih-Hung Hung Jiing-Yi Wang Chang-Wang Liu Tzu-Yun Lai http://www.mdpi.com/1424-8220/10/1/292/ Flash memory has become a more widespread storage medium for modern wireless devices because of its effective characteristics like non-volatility, small size, light weight, fast access speed, shock resistance, high reliability and low power consumption. Sensor nodes are highly resource constrained in terms of limited processing speed, runtime memory, persistent storage, communication bandwidth and finite energy. Therefore, for wireless sensor networks supporting sense, store, merge and send schemes, an efficient and reliable file system is highly required with consideration of sensor node constraints. In this paper, we propose a novel log structured external NAND flash memory based file system, called Proceeding to Intelligent service oriented memorY Allocation for flash based data centric Sensor devices in wireless sensor networks (PIYAS). This is the extended version of our previously proposed PIYA [1]. The main goals of the PIYAS scheme are to achieve instant mounting and reduced SRAM space by keeping memory mapping information to a very low size of and to provide high query response throughput by allocation of memory to the sensor data by network business rules. The scheme intelligently samples and stores the raw data and provides high in-network data availability by keeping the aggregate data for a longer period of time than any other scheme has done before. We propose effective garbage collection and wear-leveling schemes as well. The experimental results show that PIYAS is an optimized memory management scheme allowing high performance for wireless sensor networks. http://www.mdpi.com/1424-8220/10/1/292/ Wed, 30 Dec 2009 00:00:00 CET Sensors 2009-12-30 10 1 Article 292 312 1424-8220 PIYAS-Proceeding to Intelligent Service Oriented Memory Allocation for Flash Based Data Centric Sensor Devices in Wireless Sensor Networks 2009-12-30 doi: 10.3390/s100100292 Sanam Shahla Rizvi Tae-Sun Chung http://www.mdpi.com/1424-8220/9/9/7320/ The power awareness issue is the primary concern within the domain of Wireless Sensor Networks (WSNs). Most power dissipation ocurrs during communication, thus routing protocols in WSNs mainly aim at power conservation. Moreover, a routing protocol should be scalable, so that its effectiveness does not degrade as the network size increases. In response to these issues, this work describes the development of an efficient routing protocol, named SHPER (Scaling Hierarchical Power Efficient Routing). http://www.mdpi.com/1424-8220/9/9/7320/ Fri, 11 Sep 2009 00:00:00 CEST Sensors 2009-09-11 9 9 Article 7320 7342 1424-8220 Power Conservation through Energy Efficient Routing in Wireless Sensor Networks 2009-09-11 doi: 10.3390/s90907320 Dionisis Kandris Panagiotis Tsioumas Anthony Tzes George Nikolakopoulos Dimitrios D. Vergados