http://www.mdpi.com/journal/jsan Latest open access articles published in J. Sens. Actuator Netw. at http://www.mdpi.com/journal/jsan http://www.mdpi.com/2224-2708/2/2/288 In this paper we present the design and implementation of the Constrained Application Protocol (CoAP) for TinyOS, which we refer to as TinyCoAP. CoAP seeks to apply the same application transfer paradigm and basic features of HTTP to constrained networks, while maintaining a simple design and low overhead. The design constraints of Wireless Sensor Networks (WSNs) require special attention in the design process of the CoAP implementation. We argue that better performance and minimal resource consumption can be achieved developing a native library for the operating system embedded in the network. TinyOS already includes in its distribution an implementation of CoAP called CoapBlip. However, this is based on a library not originally designed to meet the requirements of TinyOS. We demonstrate the effectiveness of our approach by a comprehensive performance evaluation. In particular, we test and evaluate TinyCoAP and CoapBlip in a real scenario, as well as solutions based on HTTP. The evaluation is performed in terms of latency, memory occupation, and energy consumption. Furthermore, we evaluate the reliability of each solution by measuring the goodput obtained in a channel affected by Rayleigh fading. We also include a study on the effects that high workloads have on a server. Journal of Sensor and Actuator Networks 2013-05-14 2 2 Article 10.3390/jsan2020288 288 315 2224-2708 2013-05-14 doi: 10.3390/jsan2020288 Alessandro Ludovici Pol Moreno Anna Calveras http://www.mdpi.com/2224-2708/2/2/235 Smart embedded objects will become an important part of what is called the Internet of Things. However, the integration of embedded devices into the Internet introduces several challenges, since many of the existing Internet technologies and protocols were not designed for this class of devices. In the past few years, there have been many efforts to enable the extension of Internet technologies to constrained devices. Initially, this resulted in proprietary protocols and architectures. Later, the integration of constrained devices into the Internet was embraced by IETF, moving towards standardized IP-based protocols. In this paper, we will briefly review the history of integrating constrained devices into the Internet, followed by an extensive overview of IETF standardization work in the 6LoWPAN, ROLL and CoRE working groups. This is complemented with a broad overview of related research results that illustrate how this work can be extended or used to tackle other problems and with a discussion on open issues and challenges. As such the aim of this paper is twofold: apart from giving readers solid insights in IETF standardization work on the Internet of Things, it also aims to encourage readers to further explore the world of Internet-connected objects, pointing to future research opportunities. Journal of Sensor and Actuator Networks 2013-04-25 2 2 Review 10.3390/jsan2020235 235 287 2224-2708 2013-04-25 doi: 10.3390/jsan2020235 Isam Ishaq David Carels Girum Teklemariam Jeroen Hoebeke Floris Abeele Eli Poorter Ingrid Moerman Piet Demeester http://www.mdpi.com/2224-2708/2/2/213 In this paper, we study the channel allocation in multi-channel wireless ad hoc networks with directional antennas. In particular, we investigate the problem: given a set of wireless nodes equipped with directional antennas, how many channels are needed to ensure collision-free communications? We derive the upper bounds on the number of channels, which heavily depend on the node density and the interference ratio (i.e., the ratio of the interference range to the transmission range). We construct several scenarios to examine the tightness of the derived bounds. We also take the side-lobes and back-lobes as well as the signal path loss into our analysis. Our results can be used to estimate the number of channels required for a practical wireless network (e.g., wireless sensor network) with directional antennas. Journal of Sensor and Actuator Networks 2013-04-16 2 2 Article 10.3390/jsan2020213 213 234 2224-2708 2013-04-16 doi: 10.3390/jsan2020213 Hong-Ning Dai Kam-Wing Ng Min-You Wu http://www.mdpi.com/2224-2708/2/2/196 In many applications, the quality of data gathered by sensor networks is directly related to the signal-to-noise ratio (SNR) of the sensor data being transmitted in the networks. Different from the SNR that is often used in measuring the quality of communication links, the SNR used in this work measures how accurately the data in the network packets represent the physical parameters being sensed. Hence, the signal here refers to the physical parameters that are being monitored by sensor networks; the noise is due to environmental interference and circuit noises at sensor nodes, and packet loss during network transmission. While issues affecting SNR at sensor nodes have been intensively investigated, the impact of network packet loss on data SNR has not attracted significant attention in sensor network design. This paper investigates the impact of packet loss on sensor network data SNR and shows that data SNR is dramatically affected by network packet loss. A data quality metric, based on data SNR, is developed and a cross-layer adaptive scheme is presented to minimize data quality degradation in congested sensor networks. The proposed scheme consists of adaptive downsampling and bit truncation at sensor nodes and intelligent traffic management techniques at the network level. Simulation results are presented to demonstrate the validity and effectiveness of the proposed techniques. Journal of Sensor and Actuator Networks 2013-04-16 2 2 Article 10.3390/jsan2020196 196 212 2224-2708 2013-04-16 doi: 10.3390/jsan2020196 Yueran Gao Haibo Wang Ning Weng Lucas Vespa http://www.mdpi.com/2224-2708/2/2/172 The Internet of Things is anticipated to connect billions of embedded devices equipped with sensors to perceive their surroundings. Thereby, the state of the real world will be available online and in real-time and can be combined with other data and services in the Internet to realize novel applications such as Smart Cities, Smart Grids, or Smart Healthcare. This requires an open representation of sensor data and scalable search over data from diverse sources including sensors. In this paper we show how the Semantic Web technologies RDF (an open semantic data format) and SPARQL (a query language for RDF-encoded data) can be used to address those challenges. In particular, we describe how prediction models can be employed for scalable sensor search, how these prediction models can be encoded as RDF, and how the models can be queried by means of SPARQL. Journal of Sensor and Actuator Networks 2013-03-27 2 2 Article 10.3390/jsan2020172 172 195 2224-2708 2013-03-27 doi: 10.3390/jsan2020172 Richard Mietz Sven Groppe Kay Römer Dennis Pfisterer http://www.mdpi.com/2224-2708/2/1/156 Wireless Sensor Networks (WSNs) are versatile monitoring systems that can provide a large amount of real-time data in scenarios where wired infrastructures are inapplicable or expensive. This technology is expected to be handled by domain experts, who perceive a WSN as a (promised to be) easy to deploy black box. This work presents the deployment experience of a WSN, as conducted by domain experts, in a ground improvement area. Building upon off-the-shelf solutions, a fuel cell powered gateway and 21 sensor devices measuring acceleration, inclination, temperature and barometric pressure were installed to monitor ground subsidence. We report about how poor GSM service, malfunctioning hardware, unknown communication patterns and obscure proprietary software required in-field ad-hoc solutions. Through the lessons learned, we look forward to investigating how to make the deployment of these systems an easier task. Journal of Sensor and Actuator Networks 2013-03-11 2 1 Article 10.3390/jsan2010156 156 171 2224-2708 2013-03-11 doi: 10.3390/jsan2010156 Tomás Fernández-Steeger Matteo Ceriotti Jó Ágila Bitsch Link Matthias May Klaus Hentschel Klaus Wehrle http://www.mdpi.com/2224-2708/2/1/122 The vision for the Internet of Things (IoT) demands that material objects acquire communications and computation capabilities and become able to automatically identify themselves through standard protocols and open systems, using the Internet as their foundation. Yet, several challenges still must be addressed for this vision to become a reality. A core ingredient in such development is the ability of heterogeneous devices to communicate adaptively so as to make the best of limited spectrum availability and cope with competition which is inevitable as more and more objects connect to the system. This survey provides an overview of current developments in this area, placing emphasis on wireless sensor networks that can provide IoT capabilities for material objects and techniques that can be used in the context of systems employing low-power versions of the Internet Protocol (IP) stack. The survey introduces a conceptual model that facilitates the identification of opportunities for adaptation in each layer of the network stack. After a detailed discussion of specific approaches applicable to particular layers, we consider how sharing information across layers can facilitate further adaptation. We conclude with a discussion of future research directions. Journal of Sensor and Actuator Networks 2013-03-06 2 1 Article 10.3390/jsan2010122 122 155 2224-2708 2013-03-06 doi: 10.3390/jsan2010122 Peng Du George Roussos http://www.mdpi.com/2224-2708/2/1/109 The intention of an authentication and authorization infrastructure (AAI) is to simplify and unify access to different web resources. With a single login, a user can access web applications at multiple organizations. The Shibboleth authentication and authorization infrastructure is a standards-based, open source software package for web single sign-on (SSO) across or within organizational boundaries. It allows service providers to make fine-grained authorization decisions for individual access of protected online resources. The Shibboleth system is a widely used AAI, but only supports protection of browser-based web resources. We have implemented a Shibboleth AAI extension to protect web services using Simple Object Access Protocol (SOAP). Besides user authentication for browser-based web resources, this extension also provides user and machine authentication for web service-based resources. Although implemented for a Shibboleth AAI, the architecture can be easily adapted to other AAIs. Journal of Sensor and Actuator Networks 2013-03-06 2 1 Article 10.3390/jsan2010109 109 121 2224-2708 2013-03-06 doi: 10.3390/jsan2010109 Markus Anwander Torsten Braun Philipp Hurni Thomas Staub Gerald Wagenknecht http://www.mdpi.com/2224-2708/2/1/98 The broad use ofWireless Sensor Networks (WSN) in various fields have resulted in growing demand for advanced data collection and querying mechanisms embedded in the sensor node. Sensor Web Services (SWS) have recently emerged as a promising tool to enable external machines to have access to the information collected by public sensor webs. Machine-to-machine interactions or wireless sensor and actor networks can take advantage of this platform-independent technology to develop diverse smart grid applications. In this survey, we first briefly present the state of the art in SWS technology by describing the techniques for customizing web services to fit the sensor node capabilities such as customizing the WSDL file, compressing XML documents and redesigning TCP protocol. Then, we survey the studies that have utilized the SWS technology in smart grid applications. These studies have shown that SWS provide energy management capabilities to the consumers and the utilities, and they are well suited for smart grid integrated smart home solutions. Journal of Sensor and Actuator Networks 2013-03-06 2 1 Review 10.3390/jsan2010098 98 108 2224-2708 2013-03-06 doi: 10.3390/jsan2010098 Omar Asad Melike Erol-Kantarci Hussein Mouftah http://www.mdpi.com/2224-2708/2/1/85 The present paper focuses on various aspects regarding Hall Effect sensors’ design, integration, and behavior analysis. In order to assess their performance, different Hall Effect geometries were tested for Hall voltage, sensitivity, offset, and temperature drift. The residual offset was measured both with an automated measurement setup and by manual switching of the individual phases. To predict Hall sensors performance prior to integration, three-dimensional physical simulations were performed. Journal of Sensor and Actuator Networks 2013-02-08 2 1 Article 10.3390/jsan2010085 85 97 2224-2708 2013-02-08 doi: 10.3390/jsan2010085 Maria-Alexandra Paun Jean-Michel Sallese Maher Kayal http://www.mdpi.com/2224-2708/2/1/70 Sensor networks for various event detection applications cannot function effectively if they are vulnerable to attacks. Malicious nodes can generate incorrect readings and misleading reports in such a way that event detection accuracy and false alarm rates are unacceptably low and high, respectively. In this paper, we present a malicious node detection scheme for wireless sensor networks. Unlike others using a single threshold, the proposed scheme employs two thresholds to cope with the strong trade-off between event detection accuracy and false alarm rate, resulting in improved malicious node detection performance. In addition, each sensor node maintains the trust values of its neighboring nodes to reflect their behavior in decision-making. Computer simulation shows that the proposed scheme achieves high malicious node detection accuracy without sacrificing normal sensor nodes and outperforms the scheme using a single threshold. Journal of Sensor and Actuator Networks 2013-02-05 2 1 Article 10.3390/jsan2010070 70 84 2224-2708 2013-02-05 doi: 10.3390/jsan2010070 Sung Lim Yoon-Hwa Choi http://www.mdpi.com/2224-2708/2/1/46 In this paper we present a unified comparison of the performance of four detection techniques for centralized data-fusion cooperative spectrum sensing in cognitive radio networks under impulsive noise, namely, the eigenvalue-based generalized likelihood ratio test (GLRT), the maximum-minimum eigenvalue detection (MMED), the maximum eigenvalue detection (MED), and the energy detection (ED). We consider two system models: an implementation-oriented model that includes the most relevant signal processing tasks realized by a real cognitive radio receiver, and the theoretical model conventionally adopted in the literature. We show that under the implementation-oriented model, GLRT and MMED are quite robust under impulsive noise, whereas the performance of MED and ED is drastically degraded. We also show that performance under the conventional model can be too pessimistic if impulsive noise is present, whereas it can be too optimistic in the absence of this impairment. We also discuss the fact that impulsive noise is not such a severe problem when we take into account the more realistic implementation-oriented model. Journal of Sensor and Actuator Networks 2013-01-22 2 1 Article 10.3390/jsan2010046 46 69 2224-2708 2013-01-22 doi: 10.3390/jsan2010046 Dayan Guimarães Rausley de Souza André Barreto http://www.mdpi.com/2224-2708/2/1/25 Range-free localization algorithm continues to be an important and challenging research topic in anisotropic Wireless Sensor Networks (WSNs). Designing range-free localization algorithms without considering obstacles or holes inside the network area does not reflect the real world conditions. In this paper, we have proposed Detour Path Angular Information (DPAI) based sensor localization algorithm to accurately estimate the distance between an anchor node and a sensor node. We utilized the Euclidean distance and transmission path distance among anchor nodes to calculate the angle of the transmission path between them one by one. Then the estimated hop distance is adjusted by the angle between the anchor pairs. Based on the angle of the detoured path (which is the key factor for accuracy), our algorithm determines whether the path is straight or detoured by anisotropic factors. Our proposed algorithm does not require any global knowledge of network topology to tolerate the network anisotropy nor require high sensor node density for satisfactory localization accuracy. Extensive simulations are performed and the results are observed to be in good agreement with the theoretical analysis. DPAI achieved average sensor localization accuracy better than 0.3r in isotropic network and 0.35r in anisotropic network when the sensor density is above 8. Journal of Sensor and Actuator Networks 2013-01-17 2 1 Article 10.3390/jsan2010025 25 45 2224-2708 2013-01-17 doi: 10.3390/jsan2010025 Anup Paul Takuro Sato http://www.mdpi.com/2224-2708/2/1/1 In this paper, we propose a new approach for the detection of OFDMA and other wideband signals in the context of centralized cooperative spectrum sensing for cognitive radio (CR) applications. The approach is based on the eigenvalues of the received signal covariance matrix whose samples are in the frequency domain. Soft combining of the eigenvalues at the fusion center is the main novelty. This combining strategy is applied to variants of four test statistics for binary hypothesis test, namely: the eigenvalue-based generalized likelihood ratio test (GLRT), the maximum-minimum eigenvalue detection (MMED), the maximum eigenvalue detection (MED) and the energy detection (ED). It is shown that the eigenvalue fusion can outperform schemes based on decision fusion and sample fusion. A tradeoff is also established between complexity and volume of data sent to the fusion center in all combining strategies. Journal of Sensor and Actuator Networks 2013-01-07 2 1 Article 10.3390/jsan2010001 1 24 2224-2708 2013-01-07 doi: 10.3390/jsan2010001 Dayan Guimarães Carlos da Silva Rausley de Souza http://www.mdpi.com/2224-2708/1/3/299 Wireless sensor actuator networks are becoming a solution for control applications. Reliable data transmission and real time constraints are the most significant challenges. Control applications will have some Quality of Service (QoS) requirements from the sensor network, such as minimum delay and guaranteed delivery of packets. We investigate variable sampling method to mitigate the effects of time delays in wireless networked control systems using an observer based control system model. Our focus for variable sampling methodology is to determine the appropriate neural network topology for delay prediction and also investigate the impact of additional inputs to the neural network such as network packet loss rate and throughput. The major contribution of this work is the use of typical obtainable delay series for training the neural network. Most studies have used random generated numbers, which are not a correct representation of delays actually experienced in a wireless network. Our results here shows that adequate prediction of the time delay series using the observer based variable sampling is able to compensate for delays in the communication loop and influences the performance of the control system model. Journal of Sensor and Actuator Networks 2012-11-30 1 3 Article 10.3390/jsan1030299 299 320 2224-2708 2012-11-30 doi: 10.3390/jsan1030299 Daniel Nkwogu Alastair Allen http://www.mdpi.com/2224-2708/1/3/272 Wireless Sensor Networks (WSNs) are used in many industrial and consumer applications that are increasingly gaining impact in our day to day lives. Still great efforts are needed towards the definition of methodologies for their effective management. One big issue is themonitoring of the network status, which requires the definition of the performance indicators and methodologies and should be accurate and not intrusive at the same time. In this paper, we present a new process for the monitoring of the physical layer in WSNs making use of a completely passive methodology. From data sniffed by external nodes, we first estimate the position of the nodes by applying the Weighted Least Squares (WLS) to the method of indirect observations. The resulting node positions are then used to estimate the status of the communication links using the most appropriate propagation model. We performed a significant number of measurements on the field in both indoor and outdoor environments. From the experiments, we were able to achieve an accurate estimation of the channel links status with an average error lower than 1 dB, which is around 5 dB lower than the error introduced without the application of the proposed method. Journal of Sensor and Actuator Networks 2012-11-30 1 3 Article 10.3390/jsan1030272 272 298 2224-2708 2012-11-30 doi: 10.3390/jsan1030272 Giuseppe Colistra Luigi Atzori http://www.mdpi.com/2224-2708/1/3/254 In wireless sensor networks (WSNs), the location information of sensor nodes are important for implementing other network applications. In this paper, we propose a range-free Localization algorithm based on Neural Network Ensembles (LNNE). The location of a sensor node is estimated by LNNE solely based on the connectivity information of the WSN. Through simulation study, the performance of LNNE is compared with that of two well-known range-free localization algorithms, Centroid and DV-Hop, and a single neural network based localization algorithm, LSNN. The experimental results demonstrate that LNNE consistently outperforms other three algorithms in localization accuracy. An enhanced mass spring optimization (EMSO) algorithm is also proposed to further improve the performance of LNNE by utilizing the location information of neighboring beacon and unknown nodes. Journal of Sensor and Actuator Networks 2012-11-28 1 3 Article 10.3390/jsan1030254 254 271 2224-2708 2012-11-28 doi: 10.3390/jsan1030254 Jun Zheng Asghar Dehghani http://www.mdpi.com/2224-2708/1/3/217 The number of devices on the Internet exceeded the number of people on the Internet in 2008, and is estimated to reach 50 billion in 2020. A wide-ranging Internet of Things (IOT) ecosystem is emerging to support the process of connecting real-world objects like buildings, roads, household appliances, and human bodies to the Internet via sensors and microprocessor chips that record and transmit data such as sound waves, temperature, movement, and other variables. The explosion in Internet-connected sensors means that new classes of technical capability and application are being created. More granular 24/7 quantified monitoring is leading to a deeper understanding of the internal and external worlds encountered by humans. New data literacy behaviors such as correlation assessment, anomaly detection, and high-frequency data processing are developing as humans adapt to the different kinds of data flows enabled by the IOT. The IOT ecosystem has four critical functional steps: data creation, information generation, meaning-making, and action-taking. This paper provides a comprehensive review of the current and rapidly emerging ecosystem of the Internet of Things (IOT). Journal of Sensor and Actuator Networks 2012-11-08 1 3 Review 10.3390/jsan1030217 217 253 2224-2708 2012-11-08 doi: 10.3390/jsan1030217 Melanie Swan http://www.mdpi.com/2224-2708/1/3/183 Long-term outdoor localization remains challenging due to the high energy profiles of GPS modules. Duty cycling the GPS module combined with inertial sensors can improve energy consumption. However, inertial sensors that are kept active all the time can also drain mobile node batteries. This paper proposes duty cycling strategies for inertial sensors to maintain a target position accuracy and node lifetime. We present a method for duty cycling motion sensors according to features of movement events, and evaluate its energy and accuracy profile for an empirical data trace of cattle movement. We further introduce the concept of group-based duty cycling, where nodes that cluster together can share the burden of motion detection to reduce their duty cycles. Our evaluation shows that both variants of motion sensor duty cycling yield up to 78% improvement in overall node power consumption, and that the group-based method yields an additional 20% power reduction during periods of low mobility. Journal of Sensor and Actuator Networks 2012-10-19 1 3 Article 10.3390/jsan1030183 183 216 2224-2708 2012-10-19 doi: 10.3390/jsan1030183 Raja Jurdak Branislav Kusy Alban Cotillon http://www.mdpi.com/2224-2708/1/3/166 Despite its popularity, the development of an embedded real-time multisensor kinematic positioning and navigation system discourages many researchers and developers due to its complicated hardware environment setup and time consuming device driver development. To address these issues, this paper proposed a multisensor kinematic positioning and navigation system built on Linux with Real Time Application Interface (RTAI), which can be constructed in a fast and economical manner upon popular hardware platforms. The authors designed, developed, evaluated and validated the application of Linux/RTAI in the proposed system for the integration of the low cost MEMS IMU and OEM GPS sensors. The developed system with Linux/RTAI as the core of a direct geo-referencing system provides not only an excellent hard real-time performance but also the conveniences for sensor hardware integration and real-time software development. A software framework is proposed in this paper for a universal kinematic positioning and navigation system with loosely-coupled integration architecture. In addition, general strategies of sensor time synchronization in a multisensor system are also discussed. The success of the loosely-coupled GPS-aided inertial navigation Kalman filter is represented via post-processed solutions from road tests. Journal of Sensor and Actuator Networks 2012-09-28 1 3 Article 10.3390/jsan1030166 166 182 2224-2708 2012-09-28 doi: 10.3390/jsan1030166 Kun Qian Qian Jianguo Wang Nilesh S. Gopaul Baoxin Hu http://www.mdpi.com/2224-2708/1/2/153 In wireless sensor networks, replica node attacks are very dangerous because the attacker can compromise a single node and generate as many replicas of the compromised node as he wants, and then exploit these replicas to disrupt the normal operations of sensor networks. Several schemes have been proposed to detect replica node attacks in sensor networks. Although these schemes are capable of detecting replicas that are widely spread in the network, they will likely fail to detect replica cluster attacks in which replicas form a cluster in a small region. These attacks are also harmful because the attacker can leverage a replica cluster to harmfully impact on the much of the network. To defend against replica cluster attacks, we propose an efficient and effective replica cluster detection scheme using the Sequential Hypothesis Testing. We evaluate our proposed scheme through analysis and simulation. The evaluation results demonstrate that it accomplishes robust replica cluster detection capability. Journal of Sensor and Actuator Networks 2012-09-05 1 2 Article 10.3390/jsan1020153 153 165 2224-2708 2012-09-05 doi: 10.3390/jsan1020153 Jun-Won Ho http://www.mdpi.com/2224-2708/1/2/123 While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks. Journal of Sensor and Actuator Networks 2012-08-31 1 2 Review 10.3390/jsan1020123 123 152 2224-2708 2012-08-31 doi: 10.3390/jsan1020123 Pouria Zand Supriyo Chatterjea Kallol Das Paul Havinga http://www.mdpi.com/2224-2708/1/2/111 In this paper, we present a novel low power medium access control protocol for wireless sensor networks (WSNs). The proposed protocol, EP-MAC (Efficient MAC with Parallel Transmission) achieves high energy efficiency and high packet delivery ratio under different traffic load. EP-MAC protocol is basically based on the Time Division Multiple Access (TDMA) approach. The power of Carrier Sense Multiple Access (CSMA) is used in order to offset the fundamental problems that the stand-alone TDMA method suffers from, i.e., problems such as lack of scalability, adaptability to varying situations, etc. The novel idea behind the EP-MAC is that it uses the parallel transmission concept with the TDMA link scheduling. EP-MAC uses the methods for the transmission power adjustment, i.e., uses the minimum level power necessary to reach the intended neighbor within a specified bit error rate [BER] target. This reduces energy consumption, as well as further enhances the scope of parallel transmission of the protocol. The simulation studies support the theoretical results, and validate the efficiency of our proposed EP-MAC protocol. Journal of Sensor and Actuator Networks 2012-08-27 1 2 Article 10.3390/jsan1020111 111 122 2224-2708 2012-08-27 doi: 10.3390/jsan1020111 Mohammad Arifuzzaman Mitsuji Matsumoto http://www.mdpi.com/2224-2708/1/2/97 In a residential or nursing home environment, using ZigBee/802.15.4 wireless network specifically to collect and gather various types of personal health data proves to be a feasible choice. The Continua Guidelines has defined both the sensor-LAN IF (sensor Local Area Network Interface) PHD (Personal Health Device) and PAN IF (Personal Area Network Interface) PHD, but only a Continua certified sensor-LAN IF PHD with Zigbee HC (Health Care) profile can connect with Continua AHD (Application Hosting Device) through Zigbee/802.15.4 network and allows data communicating between AHD and PHDs. In this paper, we present a distributed Continua AHD system design that divides the AHD device containing Continua PAN IF into Continua AHD Host and Continua AHD Gateway with communication through ZigBee/802.15.4 network. Under this structure, a Continua PHD connects with a Continua AHD Host through Continua AHD Gateway within ZigBee/802.15.4 network. One immediate advantage of the proposed system is that both of the Continua sensor-LAN IF and PAN IF PHDs can connect with Continua AHD (Host) through ZigBee/802.15.4 network. To further address the QoS (Quality of Service) issue for Continua PAN IF message transmission in a ZigBee network, we present a software approach to automatically determine the types of packet transmitted and execute Continua QoS control. Together with the QoS mechanism in the enhanced ZigBee MAC Layer, this approach realizes a complete Continua QoS control mechanism for the distributed AHD system. Journal of Sensor and Actuator Networks 2012-07-25 1 2 Article 10.3390/jsan1020097 97 110 2224-2708 2012-07-25 doi: 10.3390/jsan1020097 Yung-Shun Huang Min Shih Yio-Wha Shau William T. Lin http://www.mdpi.com/2224-2708/1/2/86 As the usage and development of wireless sensor networks increases, problems related to these networks are becoming apparent. Dynamic deployment is one of the main topics that directly affects the performance of the wireless sensor networks. In this paper, biogeography-based optimization is applied to the dynamic deployment of static and mobile sensor networks to achieve better performance by trying to increase the coverage area of the network. A binary detection model is considered to obtain realistic results while computing the effectively covered area. Performance of the algorithm is compared with that of the artificial bee colony algorithm, Homo-H-VFCPSO and stud genetic algorithm that are also population-based optimization algorithms. Results show biogeography-based optimization can be preferable in the dynamic deployment of wireless sensor networks. Journal of Sensor and Actuator Networks 2012-06-27 1 2 Article 10.3390/jsan1020086 86 96 2224-2708 2012-06-27 doi: 10.3390/jsan1020086 Gaige Wang Lihong Guo Hong Duan Luo Liu Heqi Wang http://www.mdpi.com/2224-2708/1/1/59 Storing, collecting and querying data across miniaturized battery powered Wireless Sensor Networks (WSN) is a key research focus today. Distributed Data-Centric Storage (DCS), an alternate to External Storage (ES) and Local Storage (LS), is thought to be a promising and efficient storage and search mechanism. There has been a growing interest in understanding and optimizing WSN DCS schemes in recent years, where the range query mechanism, similarity search, load balancing, multi-dimensional data search, as well as limited and constrained resources have driven this line of research. In this paper, an extensive state-of-the-art study is provided including the prime WSN DCS schemes, challenges that inspired these schemes, as well as drawbacks and shortcomings of existing solutions. In contrast to previous surveys that briefly discuss the contribution of a few WSN DCS mechanisms, we provide a thematic taxonomy in which schemes are classified according to the problems dealt with including range query, similarity search, data aggregation, sensor network field non-uniformity, multi-replication, load balancing and routing algorithm. Journal of Sensor and Actuator Networks 2012-06-12 1 1 Review 10.3390/jsan1010059 59 85 2224-2708 2012-06-12 doi: 10.3390/jsan1010059 Khandakar Ahmed Mark A. Gregory http://www.mdpi.com/2224-2708/1/1/36 Applications of wireless sensor network (WSN) often expect knowledge of the precise location of the nodes. Many different localization protocols have been proposed that allow nodes to derive their location rather than equipping them with dedicated localization hardware such as GPS receivers, which increases node costs. We provide a brief survey of the major approaches to software-based node localization in WSN. One class of localization protocols with good localization performance patches together relative-coordinate, local maps into a global-coordinate map. These protocols require some nodes that know their absolute coordinates, called anchor nodes. While many factors influence the node position errors, in this class of protocols, using Procrustes Analysis, the placement of the anchor nodes can significantly impact the error. Through simulation, using the Curvilinear Component Analysis (CCA-MAP) protocol as a representative protocol in this category, we show the impact of anchor node placement and propose a set of guidelines to ensure the best possible outcome, while using the smallest number of anchor nodes possible. Journal of Sensor and Actuator Networks 2012-06-08 1 1 Article 10.3390/jsan1010036 36 58 2224-2708 2012-06-08 doi: 10.3390/jsan1010036 Thomas Kunz Benjamin Tatham http://www.mdpi.com/2224-2708/1/1/3 Source nodes in wireless image sensor networks transmit much more information than traditional scalar sensor networks, thereby demanding more energy of intermediate relaying nodes and putting energy efficiency as a key design issue. Intermediate nodes are usually interconnected by error-prone links where bit-errors are common, potentially degrading the application monitoring quality. When reliability is assured by retransmission mechanisms, higher packet error rates do not affect the application quality but result in additional energy consumption due to packet retransmission, even though many monitoring applications can tolerate some loss in the quality of the received image. DWT coding can decompose an image in data subbands, each one with different relevancies for the reconstruction of the original image at the receiver side. We propose an energy-efficient selective hop-by-hop retransmission mechanism where the reliability level of each packet is a function of the relevance of the payload data, according to the resulting subbands and the number of times a 2D DWT is applied over the images captured by the sensors’ cameras. In so doing, some lost packets are not retransmitted, saving energy of intermediate nodes with low impact to the quality of the reconstructed images. In order to estimate the benefits of this tradeoff between energy consumption and image quality, we designed a comprehensive energy consumption model and applied it in extensive mathematic simulations, providing substantial information about the mean performance of the proposed approach when compared with a fully-reliable transmission mechanism. Journal of Sensor and Actuator Networks 2012-02-01 1 1 Article 10.3390/jsan1010003 3 35 2224-2708 2012-02-01 doi: 10.3390/jsan1010003 Daniel G. Costa Luiz Affonso Guedes http://www.mdpi.com/2224-2708/1/1/1 Sensor and actuator networks have been the focus of a lot of research for quite a number of years now, and results in these fields had a tremendous influence on computer science as a whole. Take for example the fact that energy efficiency questions have never played a major role before, and today, there are journals, conferences, and complete research programs on this important issue. In general, sensor and actuator networks are considered to be an important part of the Future Internet, be it in the Internet-of-Things community, in Smart-City discussions, or in the more general field of Real-World Internet. Therefore, even though we have already come a long way, there is still a lot to do in order to make sensor and actuator networks usable and useful tools for everyday life in all kinds of domains. This new journal wants to provide a forum for researchers in the field to present their ideas and results and to discuss with others in order to advance the state of the art. [...] Journal of Sensor and Actuator Networks 2012-01-31 1 1 Editorial 10.3390/jsan1010001 1 2 2224-2708 2012-01-31 doi: 10.3390/jsan1010001 Stefan Fischer