Hybrid Wireless Sensor Networks Research Articles

Design of hybrid wireless sensor network to monitor bioelectric signals focused on the study of epilepsy

Epilepsy is considered a disorder in which a person has cer- tain episodes of disturbed brain activity. There are dierent studies that allow monitoring physiological signals associated with a possible epileptic episode. However, these require wired connections and therefore moni- toring is restricted to factors such as limited physical movements and loss of information by disconnecting sensors. Hence, there is not a sys- tem to monitor patients in a mobile (ambulatory) and wireless fashion. This paper describe a design of a wireless sensor network for a body area network (BAN ) for continuous monitoring (electroencephalogram (EEG), electrocardiogram (ECG)) and events monitoring (electrogastro- gram (EGG)) dened by the expert. The system is based on a TDMA protocol that allows sensor nodes to continuously transmit their infor- mation as well as the event nodes access to the network when needed. The system is mathematically studied and numerical results are veried through discrete event simulations.

A hybrid wireless sensor network framework for range-free event localization

In event localization, wireless sensors try to locate the source of an event from its emitted power. This is more challenging than sensor localization as the power level at the source of an event is neither predictable with precision nor can be controlled. Considering the emerging trend of long sensing range for cost-effective sensor deployment, locating events within a region much smaller than the sensing area of a single sensor has gained research interest. This paper proposes the first range-free event localization framework, which avoids expensive hardware needed by the range-based counterparts. Our approach first develops a sensing range model from the statistical information on the emitted power of a type of events so that user-defined event-detection quality can be provisioned using a minimal network of static sensors. Then an accurate event location boundary estimation technique is developed from the sensing feedbacks, which also facilitates guided expansion of the area of possible event location (APEL) to deal with sensing errors. Finally, user-defined event-localization quality guarantee is provisioned cost-effectively by inviting mobile sensors on-demand to target positions. Analytical solutions are provided whenever appropriate and comprehensive simulations are carried out to evaluate localization performance. The proposed event localization technique outperforms the state-of-the-art range-based counterpart (Xu et al., 2011) in realistic environment with path loss, shadow fading, and sensor positioning errors.

Optimization of DV-hop localization algorithm in hybrid optical wireless sensor networks

Automatic localization is one of the major issues in Wireless Sensor Networks (WSN). DV-hop algorithm is a well-known localization algorithm in WSN but with limited localization accuracy. In this paper, an improved DV-hop localization algorithm in hybrid optical wireless sensor networks is proposed based on the optimization of the parameters in WSN. Various factors that affect the localization accuracy of the DV-hop algorithm in WSN are investigated, including the communication radius of the node, the number of beacon nodes and the number of the total nodes. As the DV-hop algorithm is applied into hybrid optical sensor and WSNs (O-WSN) with rectangular topology, different parameters have to be optimized accordingly. Simulation results show that the square topology outperforms the rectangle topology more than 45 % under the same network parameters using the improved DV-hop algorithm. Therefore another improved DV-hop called Sub-Square Weighted DV-hop (SSW DV-hop) is proposed for the rectangle topology. Both simulation and experiment results demonstrate that applying the SSW DV-hop algorithmin O-WSNs could significantly improve the localization accuracy.

Hybrid wireless sensor network for building energy management systems based on the 2.4 GHz and 400 MHz bands

In this paper, a hybrid wireless sensor network (WSN) system is considered and implemented for the building energy management systems. Characteristics of the radios, which are based on the 2.4GHz and 400MHz bands, respectively, are analyzed for the building environments. For battery-operated portable sensors, narrow-bandwidth radios of the 400MHz band are employed in a star connection between their parent nodes. Between the parent nodes, a mesh network is constructed for an efficient and fast data transmission based on the wide-bandwidth radios of the 2.4GHz band. The hybrid WSN system is implemented and tested for a building environment and provides a reliable wireless communication link for gathering sensing data.

Energy-Efficient Scheduling for Mobile Sensors Using Connection Graphs in a Hybrid Wireless Sensor Network with Obstacles

This paper considers the scheduling problem of mobile sensors in a hybrid wireless sensor network (WSN) with obstacles. In a WSN, static sensors monitor the environment and report where events appear in the sensing field. Then, mobile sensors are dispatched to these event locations to perform in-depth analysis. The sensing field may contain obstacles of any shape and size. A big challenge is how to efficiently dispatch the mobile sensor to find an obstacle-avoiding shortest path. To remedy this issue, we propose an efficient scheduling mechanism based on connection graphs in this paper. Specifically, the region of network is divided into grid cells with the same size. Consequently, the search space of the shortest path is restricted to the connection graphs composed of some grid cells. Through simulation, we verify the effectiveness of our method. The paper contributes to developing an energy-efficient dispatch solution in the presence of obstacles.

Efficient Data Collection for Large-Scale Mobile Monitoring Applications

Radio frequency identification (RFID) and wireless sensor networks (WSNs) have been popular in the industrial field, and both have undergone dramatic development. RFID and WSNs are well known for their abilities in identity identification and data transmission, respectively, and hence widely used in applications for environmental and health monitoring. Though the integration of a sensor and an RFID tag was proposed to gather both RFID tag and sensed information, few previous research efforts explore the integration of data transmission modes in the RFID and WSN systems to enhance the performance of the applications. In this paper, we propose a hybrid RFID and WSN system (HRW) that synergistically integrates the traditional RFID system and WSN system for efficient data collection. HRW has hybrid smart nodes that combine the function of RFID tags, the reduced function of RFID readers, and wireless sensors. Therefore, nodes can read each other's sensed data in tags, and all data can be quickly transmitted to an RFID reader through the node that first reaches it. The RFID readers transmit the collected data to the back-end servers for data processing and management. We also propose methods to improve data transmission efficiency and to protect data privacy and avoid malicious data selective forwarding in data transmission. Comprehensive simulation and trace-driven experimental results show the high performance of HRW in terms of the cost of deployment, transmission delay and capability, and tag capacity requirement.

Mobile Sensor Networks

Wireless sensor networks (WSNs) provide a convenient way to monitor the physical environment. They consist of a large number of sensors that have sensing, computing, and communication abilities. In the past, sensors were considered as static, but the network functionality would degrade when some sensors were broken. Today, the emerging hardware techniques have promoted the development of mobile sensors. Introducing mobility to sensors not only improves their capability but also gives them flexibility to deal with node failure. The article studies the research progress of mobile sensor networks, which embraces both system hardware and dispatch software. For system hardware, we review two popular types of mobile sensor platforms. One is to integrate mobile robots with sensors, whereas the other is to use existing conveyances to carry sensors. Dispatch software includes two topics. We first address how to solve different coverage problems by using a purely mobile WSN and then investigate how to dispatch mobile sensors in a hybrid WSN to perform various missions including data collection, faulty recovery, and event analysis. A discussion about research challenges in mobile sensor networks is also presented in the article.

A Two-Phase Dispatch Heuristic to Schedule the Movement of Multi-Attribute Mobile Sensors in a Hybrid Wireless Sensor Network

The paper considers a hybrid wireless sensor network with static and mobile sensors, where each static sensor can detect only one attribute of event while a mobile sensor can analyze multiple attributes of events. Static sensors monitor the environment and report where events appear. Mobile sensors then move to these event locations to conduct more in-depth analysis. A critical issue is how to schedule the traveling paths of mobile sensors so as to extend their lifetime. We formulate this issue as a multi-round multi-attribute sensor dispatch problem and prove it to be NP-complete. Then, we develop a two-phase dispatch heuristic that adopts the concepts of Pareto optimality and spanning-tree construction. Our heuristic allows arbitrary numbers of mobile sensors and event locations and tries to reduce and balance the energy consumption of mobile sensors in each round. Through simulations, we verify the effectiveness of our heuristic. The paper contributes in defining a new sensor dispatch problem and developing an energy-efficient solution to the problem.

Wireless Sensor Network Platform for Intrinsic Optical Fiber pH Sensors

This paper explores the potential of creating a hybrid wireless sensor network (WSN) through the establishment of a generic WSN platform, which allows for the effective integration of a number of novel optical fiber (wired) sensors. The aim is to maximize the potential of a sensor system created using advanced optical sensor techniques coupled to the WSNs. In this design, each wireless mote in a WSN is configured as a generic platform for ease of integration of the optical fiber sensor modules. In the work carried out, a typical configuration is used comprising a LED light source, a filter, a photodiode, and an amplifying circuit. Thus, each mote is able to record and process the signals generated from the optical fiber sensors and transmit the data obtained on the measurements made wirelessly to a base station. To verify both the hybrid concept and the effectiveness of a generic platform established, the system is tested using an intrinsic pH optical fiber sensor developed by some of the authors and especially chosen to be integrated into the platform. When the sensor is subjected to a range of solutions with varying pH values from 1 to 9, the sensor data generated from the system are collected at the base station. The experimental results obtained confirm the functionality of the platform designed, and its ability to allow real-time optical fiber sensor data monitoring, processing, and transmission. The success of the creation of this type of hybrid WSN platforms thus opens up new sensing opportunities using a wide range of optical fiber sensors, thus showing a potential impact on some measurement applications where conventional WSNs cannot meet the systems requirements.

Modified Particle Swarm Optimization for Hybrid Wireless Sensor Networks Coverage

Efficient network coverage and connectivity are the requisites for most Wireless Sensor Network deployments, particularly those concerned with area monitoring. The Coverage Control Technology is one of the basic technologies of wireless sensor network, and is mainly concerned about how to prolong the network lifetime on the basis of meeting users’ perception demand. To optimize wireless sensor networks coverage, an algorithm which is based on particle swarm optimization with dynamic clonal selection is proposed. This algorithm controls the clonal quantity and variation range of particle which represents the locations of all mobile sensor nodes, by coverage rate and similarity among the swarm to avoiding being trapped in local optimum. By comparison of the simulation results with other algorithms, this optimization algorithm could improve the performance of network coverage more effectively.

Development of Zigbee-Wifi-Wimax Hybrid Wireless Sensor Network based Telemedicine System

This paper is an outcome of an on-going research project sponsored by department of (DST), Ministry of Science and Technology, Government of India, in which a wireless sensor network based on ZigBee-WiFi-Wi-Max hybrid wireless sensor network (WSN) has been developed. This system has been used for implementing telemedicine system as an information gateway between old age homes and nearby hospitals, for the purpose of transmitting health data wirelessly over a distance of about 20 km range. This system is developed in two separate modules, one consisting of ZigBee based WSN which is applied for wireless data transmission up to a distance of two kilometres, and the other comprises of WiFi-Wi-Max based WSN used to transmit data up to a distance of twenty kilometres. The hybrid wireless network has been tested for distance range, speed of data transfer and time delays for bulk data transfer. Several observations were collected and it has been proved experimentally that the developed system is low cost, consumes relatively low power, and transmits data efficiently without significant time delay in bulk data transmission. Another solution which has been designed and validated is to transfer all data to a database residing on web. This database can be accessed via 3G – GRPS connection on PDA, Mobile phones at any location across the globe. For areas without pre-existing physical cable or landline telephone networks, wireless application protocol (WAP) may be a viable alternative for broadband access between remote ZigBee networks and hospital information centre that has been economically unavailable. In the ZigBee-Wi-Max hybrid system first low distance information (within old age home) is transmitted wirelessly using ZigBee technology. Then this information is transferred to Web server and it can be assessed on Laptops/ Computers having internet connection, mobile phones, personnel digital assistant (PDAs) using GPRS connection. The performance of the hybrid system has been evaluated based on numeric result of testing.

A Vector Algebraic Algorithm for Coverage Compensation in Hybrid Wireless Sensor Networks

In wireless sensor networks, coverage holes are caused by energy depletion at some nodes, and the aim of this paper is to study how to utilize the redundant nodes with remaining energy. Particularly, this paper proposes a vector algebra based algorithm by exploring redundant nodes as an extra dimension for coverage compensation. This algorithm consists of two parts. One is to find the locations of potential redundant nodes for coverage compensation; and the other is to opportunistically select the best redundant nodes by jointly considering the hole boundaries and the remaining energy of nodes. Simulation results are provided to demonstrate that the proposed algorithm minimizes the energy consumption when repairing the holes for full coverage. Furthermore, compared with other algorithms, the proposed one exhibits better performance in terms of moving distance and energy consumption.

Coverage Optimization of Hybrid Wireless Sensor Networks Based on Modified Particle Swarm Algorithm

A strategy for controlling mobile nodes based on PSO algorithm with neighborhood disturbance was proposed for improving the network coverage rate in wireless sensor networks. The non-dominated sorting strategy was led into basic PSO algorithm to seek best particle and adaptive neighborhood disturbance operation was used to conquer the drawback of PSO falling into local optimum. Therefore, the effect of network coverage had been improved and the network energy consumption can be reduced.

A Proposed Hybrid Wireless Sensor Networks Deployed on the Sea

Wireless sensor networks are envisioned to perform monitoring tasks over the large portion of the world covered by oceans. However, deploying wireless sensor networks on the sea poses many challenges. To deal with the problems, we proposed a hybrid wireless sensor networks deployed on the sea which combines the advantages of wireless sensor networks (WSNs) and Underwater Acoustic Sensor Networks (UWA-SNs ) together. In this paper, we first introduced the structure of the double-head sensor node, and then discussed the applications of the hybrid networks, such as ocean monitoring, test bed and intrusion detection. We also present the analysis of deployment of the hybrid sensor networks.

Energy efficient mechanism using flexible medium access control protocol for hybrid wireless sensor networks

Energy efficiency is a primary consideration in a wireless sensor network (WSN). This is also a major parameter when designing a medium access control (MAC) protocol for WSNs. Hierarchical clustering structure is regarded suitable for WSNs due to its good performance in energy conservation. In this work, an adequately flexible mechanism for clustering WSNs is designed, in which some creative or promotional metrics are utilized, such as cluster head selection algorithm, cluster optional reconstruction, interested data transmission, multiple path routing protocol. All these strategies were cooperated to maximize energy saving of whole system. An appropriate MAC protocol for this mechanism is proposed, by flexibly switching the status of diverse sensor nodes in different strategies. The simulation results show that the proposed MAC protocol is suitable for clustering WSNs and performs well in aspects of energy efficiency, flexibility and scalability.

Advances in ambient intelligence technologies

This special issue contains selected papers from the 3rd International Conference on Ambient Systems, Networks and Technologies (ANT 2012), which was held at Niagara Falls, Ontario, Canada, August 27–29, 2012. The conference attracted a large number of scientific papers that contributed to the state-of-the-art in the areas of pervasive and ambient information systems. All the papers selected for this special issue have undergone two rounds of rigorous review process. Based on the reviewers’ feedback, seven papers were selected for publication from eight best papers invited from ANT 2012. The accepted papers cover interesting works on new developments in ambient intelligence such as adaptable intelligence systems, smart environments, body area networks, and network security. The first paper by Zhang, Khedri, and Jaskolka, ‘‘An Aspect-Oriented Language for Feature Modeling’’, proposes a new language called AO-PFA for developing ambient systems. Built on top of Product Family Algebra (PFA) and by using the aspect-oriented technology, AOPFA offers capabilities in dealing with unpredictable changes in ambient applications. The paper by Hoelzl, Kurz, and Ferscha, ‘‘Goal Oriented Recognition of Composed Activities for Reliable and Adaptable Intelligence Systems’’, focuses on activity and context recognition, an important research topic for adaptable ambient intelligence systems. The paper proposes a goal oriented approach to dynamically create and instantiate models to recognize high level composed activities in an opportunistic way. The paper by Li, He, and Arora, ‘‘ThermoNet: FineGrain Assessment of Building Comfort and Efficiency’’, describes ThermoNet, a hybrid wireless sensor network solution for monitoring and optimizing energy consumption of the Heating, Ventilation, and Air Conditioning systems in large buildings. The paper reports some interesting findings based on the data collected from a realworld environment. The paper by Menon, Jayaraman, and Govindaraju, ‘‘Probabilistic Spatio-Temporal Retrieval in Smart Spaces’’, deals with uncertainties of object tracking in smart spaces. The paper proposes a data model that supports computation of probabilities of spatio-temporal queries giving the uncertainty of the location of an occupant. The paper by Knapen et al., ‘‘Exploiting GraphTheoretic Tools for Matching in Carpooling Applications’’, studies carpooling for commuting and proposes a Global CarPooling Matching Service (GCPMS) that provides advice on how to combine commuting trips by carpooling. In order to evaluate the matching performance of the GCPMS, a multi-agent system is also developed and some initial experimental results are reported. The paper by Khan et al. ‘‘A New Patient Monitoring Framework and Energy-Aware Peering Routing Protocol (EPR) for Body Area Network Communication’’, proposes a new architecture of Body Area Networks for indoor hospital environments. The paper presents an EPR for reducing the traffic load and energy consumption while increasing the number of packets successfully delivered to the destinations. The final paper by Beitollahi and Deconinck, ‘‘ConnectionScore: A Statistical Technique to Resist Application-Layer DDoS Attacks’’, describes a Q. Z. Sheng J. Ma School of Computer Science, The University of Adelaide, Adelaide, SA 5005, Australia e-mail: qsheng@cs.adelaide.edu.au

ThermoNet: fine-grain assessment of building comfort and efficiency

Understanding the performance of the heating, ventilation, and air conditioning (HVAC) system in large buildings is a prerequisite for optimizing their energy efficiency. Fine grain performance analysis has not, to our knowledge, received adequate attention thus far. To address this issue we evaluate the thermal comfort and the energy efficiency of a relatively modern HVAC system in a large building based on building-wide high-fidelity environmental data collected via a wireless sensor network over 12 months. Access to fine grain information reveals temporal and spatial dynamics that help quantify the level of (non-)compliance with the system’s control objective and the building’s thermal comfort standards: we find over-conditioning at multiple time scales which offers opportunities for reduced operating cost, and identify building anomalies and ill-conditioned rooms that need maintenance. The paper moreover describes ThermoNet, our hybrid wireless sensor network solution for monitoring a legacy building, which uses duty cycling and adaptive power control to achieve high data yield with low power consumption.

Sensor Deployment for Full Detection on Delay Tolerant Event in Hybrid Wireless Sensor Networks

Sensor Deployment for Full Detection on Delay Tolerant Event in Hybrid Wireless Sensor Networks

Hybrid WSN and RFID indoor positioning and tracking system

Wireless sensor networks (WSNs), consisting of a large number of nodes to detect ambient environment, are widely deployed in a predefined area to provide more sophisticated sensing, communication, and processing capabilities, especially concerning the maintenance when hundreds or thousands of nodes are required to be deployed over wide areas at the same time. Radio frequency identification (RFID) technology, by reading the low-cost passive tags installed on objects or people, has been widely adopted in the tracing and tracking industry and can support an accurate positioning within a limited distance. Joint utilization of WSN and RFID technologies is attracting increasing attention within the Internet of Things (IoT) community, due to the potential of providing pervasive context-aware applications with advantages from both fields. WSN-RFID convergence is considered especially promising in context-aware systems with indoor positioning capabilities, where data from deployed WSN and RFID systems can be opportunistically exploited to refine and enhance the collected data with position information. In this papera, we design and evaluate a hybrid system which combines WSN and RFID technologies to provide an indoor positioning service with the capability of feeding position information into a general-purpose IoT environment. Performance of the proposed system is evaluated by means of simulations and a small-scale experimental set-up. The performed analysis demonstrates that the joint use of heterogeneous technologies can increase the robustness and the accuracy of the indoor positioning systems.

Optimal Mobile Sensor Scheduling for a Guaranteed Coverage Ratio in Hybrid Wireless Sensor Networks

This paper proposes an optimal mobile sensor-scheduling algorithm for recovering the failure sensors in hybrid wireless sensor networks (WSNs). To maintain a guaranteed coverage over the area of interest, spare mobile sensors in WSNs will be activated to replace the failure sensors. The optimal scheduling problem is formulated into two optimization problems, one of which precisely determines the minimum value of the largest distance required to travel for mobile sensors, while the other one gives the optimal dispatch for mobile sensors to minimize the total travel distance. Furthermore, a distributed suboptimal scheduling, which only requires the local matching information of mobile sensors, is developed as well. Both regular and random network topologies are provided to illustrate the proposed algorithms in the simulation.