We present an algorithm for computing a compact polygonal boundary of physical phenomena that nodes in a wireless sensor network can detect. It works strictly local and is robust against measurement errors and packet loss. It can deal with non-convex shapes and assumes nothing but location awareness at the nodes and a loose time synchronization. Other than different schemes described in literature our algorithm does not rely on a hierarchical clustered communication structure. After discussing related approaches and introducing our boundary approximation scheme in detail, we show through an extensive set of simulations that it is robust and accurate.

Information about distances to other nodes in wireless sensor networks has proven advantageous not only for location discovery but is also helpful for context aware applications in general. In this paper we present a novel approach to distance estimation that does neither depend on special hardware nor on unreliable measurements of physical wireless communication properties. Instead, it is inspired by the observation that distant nodes have fewer neighbors in common than close ones and calculates distances from intersection cardinalities of sets of adjacent nodes. We discuss related work and present the new approach in detail including its mathematical foundations. A simulative performance analysis comprising different scenarios shows that our scheme yields competitive results.

In environments with limited network bandwidth or resource-constrained computing devices the high amount of protocol overhead caused by SOAP is disadvantageous. Therefore, recent research work concentrated on more compact, binary representations of XML data. However, due to the special characteristics of SOAP communication most of these approaches are not applicable in the field of Web services. First, we give a detailed overview of the latest developments in the field of XML data compression. Then we will introduce a new approach for compressing SOAP data which utilizes information on the structure of the data from an XML schema or WSDL document to generate a single custom pushdown automaton. This cannot only be used as a highly efficient validating parser but also as a compressor: its transitions are tagged with short binary identifiers which replace XML tags during compression. This approach leads to extremely compact data representations as well as low memory and CPU utilization

Positioning sensor nodes requires distance information to reference points. Due to resource limitations in sensor networks, distance determination in low-cost sensor nodes without additional hardware is difficult. Known techniques such as distance estimation based on received signal strength (RSSI) are mostly inaccurate or have limitations. We propose a new method to measure the distance between a transmitting node and a receiving node using the minimal transmission power. The determined distance is more precise than RSSI, has a low variance and is therefore particularly suitable for positioning. Finally, we implemented a demonstrator application using weighted centroid localization to show the practical implementation.

Within the past years the Web service technology emerged into more and more fields of application. In some cases the classical approach of using HTTP as a transport binding for SOAP seems no longer adequate. As a full scale application protocol HTTP causes a high amount of protocol overhead and is too inflexible for many Web Service scenarios. In this paper we initially give an in-depth review of existing transport bindings with a strong focus on data rate efficiency. Then we introduce an advanced UDP binding called PURE that significantly reduces the protocol overhead and enables interesting additional features such as point-to-multipoint communication via IP multicast and broadcast.

A major drawback of using SOAP for application integration is its enormous demand for network bandwidth. Compared to classical approaches like Java-RMI and CORBA, SOAP messages typically cause more than three times more network traffic. In this paper we will give a detailed survey of state of the art binary encoding strategies for SOAP and introduce a new experimental concept for SOAP compression, which makes use of the commonly available WSDL description of a SOAP Web service.

In this paper we present a modular and extensible visualization framework for wireless sensor networks. These networks have typically no means of visualizing their state, measurements or computational results. Visualization is therefore a key issue to develop and operate these networks. Data emitted by individual sensor nodes is collected by the visualization software and passed to a flexible multi-layer plug-in mechanism that renders the information on a canvas. Developers can easily adapt existing or develop new custom tailored plug-ins for their specific application.