A Sensor Web Middleware with Stateful Services for Heterogeneous Sensor Networks

Key to the appropriate use of data is the knowledge of data quality. This knowledge is critical for products and decision-support tools that utilize real-time data, and it is also essential for the longer term application of data as well. Guidance by the National Archives and Records Administration (NARA) for appraising observational data for archive states that factors favoring long-term or permanent retention include the uniqueness, completeness, and quality of observational data and the quality and completeness of metadata [1]. The National Oceanographic Data Center (NODC), the designated archive center for oceanographic data in the U.S., requires that data submitted be documented to enable secondary use and ensure data posterity. Such metadata should include not only geospatial characteristics and time periods of observations, but also the collection methods, instrumentation used, units of measure, acceptable values, error tolerance, processing history, quality assessments and explanations of quality flags, data aggregation methods, and other pertinent information [2]. Providing this information in a consistent manner can be a challenge. However, an approach to capturing and conveying this metadata using community-developed practices for ocean observing system data and metadata is well underway. This paper presents methods of capturing data and provenance of data quality using the Open Geospatial Consortium (OGC) Sensor Web Enablement (SWE) framework. It describes the types of metadata content captured and demonstrates the utility and significance of defining and registering terms to enable semantic, as well as syntactic, interoperability. The SWE framework provides an avenue for conveying quality flags and methods used to make assurances about the integrity of oceanographic data for real-time consumption and for potential submittal to permanent archives such as NODC.

The Sensor Web is an emerging trend which makes various types of web-resident sensors, instruments, image devices, and repositories of sensor data, discoverable, accessible, and controllable via the World Wide Web. A lot of effort has been invested in order to overcome the obstacles associated with connecting and sharing these heterogeneous sensor resources. This chapter emphasizes the Sensor Web Enablement (SWE) standard defined by the OpenGIS Consortium (OGC), which is composed of a set of specifications, including SensorML, Observation & Measurement, Sensor Collection Service, Sensor Planning Service and Web Notification Service. It also presents a reusable, scalable, extensible, and interoperable service oriented sensor Web architecture that (i) conforms to the SWE standard; (ii) integrates Sensor Web with Grid Computing and (iii) provides middleware support for Sensor Webs. In addition, this chapter describes the experiments and an evaluation of the core services within the architecture.

The Web service resource framework (WSRF) was announced in January 2004 as a new way for manipulating "stateful resources" to perform grid computing tasks using Web services. This paper discusses, to our knowledge, the most complex application built to date utilizing WSRF concepts. We describe a remote job execution system that handles scheduling, data movement, security and inter-job dependencies. The application is built on top of WSRF.NET, the first publicly-available toolkit for constructing WSRF-compliant Web services. WSRF.NET is an open-source project that implements both the WSRF and WS-notification family of specifications and runs on the Microsoft.NET platform. Our explicit goal in the effort reported in this paper is not to replace the existing tools such as GRAM/GlobusRun, MDS and Condor/Condor-G but rather to evaluate - via a concrete implementation - the new capabilities provided for such grid operations via WSRF. We find that, in general, WSRF and WS-notification facilitate far richer client-side and server-side interactions than previously accomplished in the state of the art in grid computing.

We present geometric broadcast for sensor and actor networks (GBSA), a novel broadcasting protocol for heterogeneous wireless sensor and actor networks. While broadcasting is a very energy-expensive protocol, it is also widely used as a building block for a variety of other network layer protocols. Therefore, reducing the energy consumption by optimizing broadcasting is a major improvement in heterogenous sensor networking. GBSA is a distributed algorithm where nodes make local decisions on whether to transmit based on a geometric approach. GBSA does not need any neighborhood information and imposes very low communication overhead. GBSA is scalable to the change in network size, node type, node density and topology. GBSA accommodates seamlessly such network changes, including the presence of actors in heterogeneous sensor networks. Indeed GBSA takes advantage of actor nodes, and uses their resources when possible, thus reducing the energy consumption by sensor nodes. Through simulation evaluations, we show that GBSA is very scalable and its performance is improved by the presence of actors. At best of our knowledge, GBSA is the first broadcast protocol designed specifically for heterogeneous sensor and actor networks.

SOAP is the protocol used most often in web services communications. Implementations of the Web Services Resource Framework (WSRF) use SOAP as a communications protocol as well. Performance analyses for SOAP toolkits have been performed for various cases and toolkits but WSRF implementations have generally not been taken into account. This work firstly compares the SOAP performance of four WSRF implementations, namely Apache Muse, the Globus Toolkit, WSRF::Lite and UNICORE 6's WSRFLite, followed by an examination of the performance of WSRF operations. The benchmark results give an indication on how implementations fare performance–wise and can be used to decide which implementation is to be used, especially if performance is an issue.

Fault tolerant aggregation in heterogeneous sensor networks

In this work, we propose a small world model to design Heterogeneous Sensor Networks (HSNs). The proposed model takes into account the communication pattern of this network to create shortcuts directed to the monitoring node, decreasing data communication latency. The endpoints of these shortcuts are nodes with more powerful communication range and energy reserves to support the long communication range. However, this kind of communication causes a high interference in the wireless channel. For this, the proposed model uses the multi-interface and multi-channel capability of the MAC layer to reduce the number of collisions during data communication. Simulation results showed that with just a few powerful nodes, a wireless sensor network can be tuned into a HSN with small world features. Also, when the shortcuts are directed to the monitoring node and assigned to a different wireless channel, the number of collisions and the data communication latency are reduced.

Information fusion helps telemonitoring systems to better unify data collected from different sensors. This paper presents last improvements made on a telemonitoring system aimed at enhancing remote healthcare for dependent people at their homes. The system is based on SYLPH, a novel platform based on a service-oriented architecture approach over a heterogeneous Wireless Sensor Networks infrastructure to create intelligent environments. Because of SYLPH, the system allows the interconnection of several sensor networks from different wireless technologies, such as ZigBee or Bluetooth. Furthermore, the SYLPH platform can be executed over multiple wireless devices independently of their microcontroller or the programming language they use.

Supporting dynamic access to virtualized data resources via WSRF-based services

[EN] SAFE-ECH is an innovative intelligent AAL open source system for monitoring nursing homes, that creates an Ambient Intelligent environment in a residence by collecting and storing sensor monitoring data, performing intelligent data analysis and specific actions to enhance the safety, comfort and efficient care of aged people. Our system implements open standards of the Open Geospatial Consortium complying with Observations & Measurements Schema (O&M), SensorML and Sensor Web Enablement (SWE) specifications. Our system adapts to the specific needs of each nursing home, integrating the required sensors, actuators, rules and services. It is scalable and allows the management of several residences simultaneously.

USN(Ubiquitous Sensor Network) is a core infrastructure that u-life use to enable the realization in the ubiquitous society through various services of area such as u-city, u-Health. Therefore, we need a research for domestic standards to establish USN technique. Currently, status of USN standards is most standard and research that it is a technology for sensor node implementation and a protocol for energy-efficient communication and interlock with existing network. But, Standard and research for sensor network and integration management of heterogeneous sensor networks for USN application and sensing data management and USN database structure definition such as application and middleware is weak level. In this paper, we researched for standard development of domestic a sensor network and the relevant standard analysis to configure SWE(Sensor Web Enablement) of OGC(Open Geospatial Consortium) for standarded plattform technology. Also we researched that it`s a connection between domestic ITA(Telecommunications Technology Association) standards and SWE Standard.

As more and more innovative applications of wireless sensor networks emerge, the need for deploying heterogeneous sensors with different functionalities and capabilities rise rapidly. In this study, we consider a heterogeneous sensor network containing at least two types of sensors: powerful sensors and normal sensors. Powerful sensors have higher energy and computing capacities, and can communicate with normal sensors using the same network interface. Communications between powerful sensors may thus be facilitated by building an overlay on top of the normal sensors. The topology of the overlay is critical. The overlay must have a low diameter to efficiently support upper layer applications such as resource discovery. It must also consider the energy consumption of the relaying normal sensors. In this paper, we propose a distributed overlay formation protocol to achieve the above goals. Through simulation, we compare our protocol with two overlay formation protocols, fully connected graph and minimum spanning tree. The results show that our proposed protocol can achieve better performance both in message latency and energy consumption.

On the design of resilient heterogeneous wireless sensor networks based on small world concepts

Energy saving to prolong the network life is an important design issue while developing a new routing protocol for wireless sensor network. Clustering is a key technique for this and helps in maximizing the network lifetime and scalability. Most of the routing and data dissemination protocols of WSN assume a homogeneous network architecture, in which all sensors have the same capabilities in terms of battery power, communication, sensing, storage, and processing. Recently, there has been an interest in heterogeneous sensor networks, especially for real deployments. This research paper has proposed a new energy aware clustering protocol (EACP) for heterogeneous wireless sensor networks. Heterogeneity is introduced in EACP by using two types of nodes: normal and advanced. In EACP cluster heads for normal nodes are elected with the help of a probability scheme based on residual and average energy of the normal nodes. This will ensure that only the high residual normal nodes can become the cluster head in a round. Advanced nodes use a separate probability based scheme for cluster head election and they will further act as a gateway for normal cluster heads and transmit their data load to base station when they are not doing the duty of a cluster head. Finally a sleep state is suggested for some sensor nodes during cluster formation phase to save network energy. The performance of EACP is compared with SEP and simulation result shows the better result for stability period, network life and energy saving than SEP.

The World-Wide Sensor Web is generating tremendous amount of real-time sensor data streams and will enable scientists to observe phenomena that are previously unobservable. As the concept of sensor web is to connect all the sensors and their data to achieve shared goals, improving the openness and accessibility of sensor data is important. The Open Geospatial Consortium Sensor Observation Service (SOS) defines standard web service protocols for sharing sensor data online in an interoperable manner. However, SOS has a relatively weak ecosystem, which makes it difficult to build and consume, and it only supports predefined queries. On the other hand, the OASIS1 Open Data Protocol (OData) has a strong ecosystem and flexible query functions. But the soft-typing approach of OData requires it to have a commonly agreed data model to be interoperable. As we argue that the two standards can benefit from each other, we propose a sensor data mediator solution and define an SOS entity data model for OData (SOS-OData) to bridge these two standards. Our prototype demonstrates that the proposed system can convert between existing SOS and SOS-OData services. As a result, we not only can consume SOS data with the flexible OData query functions, but can also easily build an SOS-compliant service with the strong OData ecosystem. We argue that the bridging between these two standards would consequently lead us to the vision of open data for sensor web.