Till Riedel

Decentralized enterprise systems: a multiplatform wireless sensor network approach

Massively deployed wireless sensor and actuator networks, co-existing with RFID technology, can bring clear benefits to large-scale enterprise systems, by delegating parts of the business functionality closer to the point of action. However, a major impediment in the integration process is represented by the variety of customized platforms and proprietary technologies. In this article, we present a three-layer, service-oriented architecture that accommodates different sensor platforms and exposes their functionality in a uniform way to the business application. Our work is motivated by real business cases from the oil and gas industry. In our implementation, we use three sensor platforms (particle, muNode, and Sindrion) integrated through the universal plug and play (UPnP) standard and incorporated into an enterprise software system. The practical tests and application trials confirm the feasibility of our solution but also reveal a number of challenges to be taken into account when deploying wireless sensor and actuator networks at industrial sites.

Using a 2DST waveguide for usable, physically constrained out-of-band Wi-Fi authentication

This paper proposes using a 2D waveguide for a novel means of authentication in public Wi-Fi infrastructures. The design of the system is presented, and its practicability and usability is comparatively discussed with that of five other tag and context based authentication schemes, two of which have not been previously realized. In accordance with the presented application scenarios, all of the schemes were implemented in a platform-independent fashion built on web technology.

Sharing sensor networks

Many industrial applications rely on sensors and sensor networks residing on machinery, transport containers or in the environment. For distributed processes in such domains the sharing of those sensor networks is crucial. This paper introduces a peer-to-peer (P2P) architecture for sharing services provided by existing sensor networks with any Internet based application. The differences between the sensor networks are abstracted using a service-oriented approach. The proposed technology is able to build up a global sensor Internet across multiple domain boundaries. Our implementation is evaluated with 300+ sensor nodes organized in a P2P network across continents.

Enabling low-cost particulate matter measurement for participatory sensing scenarios

This paper presents a mobile, low-cost particulate matter sensing approach for the use in Participatory Sensing scenarios. It shows that cheap commercial off-the-shelf (COTS) dust sensors can be used in distributed or mobile personal measurement devices at a cost one to two orders of magnitude lower than that of current hand-held solutions, while reaching meaningful accuracy. We conducted a series of experiments to juxtapose the performance of a gauged high-accuracy measurement device and a cheap COTS sensor that we fitted on a Bluetooth-enabled sensor module that can be interconnected with a mobile phone. Calibration and processing procedures using multi-sensor data fusion are presented, that perform very well in lab situations and show practically relevant results in a realistic setting. An on-the-fly calibration correction step is proposed to address remaining issues by taking advantage of co-located measurements in Participatory Sensing scenarios. By sharing few measurement across devices, a high measurement accuracy can be achieved in mobile urban sensing applications, where devices join in an ad-hoc fashion. A performance evaluation was conducted by co-locating measurement devices with a municipal measurement station that monitors particulate matter in a European city, and simulations to evaluate the on-the-fly cross-device data processing have been done.

Using web service gateways and code generation for sustainable IoT system development

Wireless Sensing and Radio Identification systems have undergone many innovations during the past years. This has led to short product lifetimes for both software and hardware compared to classical industries. However, especially industries dealing with long-term support of products, e.g. of industrial machinery, and product lifetime of 40+ years may especially profit from an Internet of Things. Motivated by a practical industrial servicing use case this paper shows how we hope to make equally sustainable IoT solutions by employing a model driven software development approach based on code generation for multi-protocol web service gateways.

Device-free and device-bound activity recognition using radio signal strength

Background: We investigate direct use of 802.15.4 radio signal strength indication (RSSI) for human activity recognition when 1) a user carries a wireless node (device-bound) and when 2) a user moves in the wireless sensor net (WSN) without a WSN node (device-free). We investigate recognition feasibility in respect to network topology, subject and room geometry (door open, half, closed). Methods: In a 2 person office room 8 wireless nodes are installed in a 3D topology. Two subjects are outfitted with a sensor node on the hip. Acceleration and RSSI are recorded while subject performs 6 different activities or room is empty. We apply machine learning for analysis and compare our results to acceleration data. Results: 10-fold cross-validation with all nodes gives accuracies of 0.896 (device-bound), 0.894 (device-free) and 0.88 (accelerometer). Topology investigation reveals that similar accuracies may be reached with only 5 (device-bound) or 4 (device-free) selected nodes. Applying trained data from one subject to the other and vice-versa shows higher recognition difference on RSSI than on acceleration. Changing of door state has smaller effect on both systems than subject change; with least impact when door is closed. Conclusion: 802.15.4 RSSI suited for activity recognition. 3D topology is helpful in respect to type of activities. Discrimination of subjects seems possible. Practical systems must adapt no only to long-term environmental dispersion but consider typical geometric changes. Adaptable, robust recognition models must be developed.

The uPart experience: building a wireless sensor network

This paper presents an experience report illustrating the design of the uPart tiny low-power sensor network platform: from the analysis phase over the definition of the application, design and construction of hardware, the implementation of the software and network to the application set-up. uPart sensor nodes were given away in the conference badge to 500 voluntary attendees of the Ubicomp 2005. In our demo application, uParts were able to recognize activities of attendees of the Ubicomp 2005 conference. Design was carried out under serve time and budget restrictions. The paper focuses on reporting design decisions and presents technical details of uPart hardware, firmware and applications. It also shows first qualitative experiences with the run of the system at the conference. The outcome of the paper is a general meta-guideline for designing sensor network systems under similar conditions.

Syncob: Collaborative Time Synchronization in Wireless Sensor Networks

This paper analyses the problem of time-synchronization of distributed sensor nodes. We present a Syncob, a method for synchronizing an arbitrary number of nodes in a distributed setting without the requirements of an infrastructure, master node or time and resource consuming protocol overhead. Syncob is therefore also very good suited for highly mobile settings with ad-hoc communication. Syncob is implemented as a physical layer protocol and provides a time synchronization deviation of max. 4 mus between any participating node. Our implementation on low-cost pPart sensor nodes shows that Syncob requires very low overhead and very low complexity for hardware and software.

ProximityHat: a head-worn system for subtle sensory augmentation with tactile stimulation

In this paper we present the iterative design process of our wearable sensory substitution system ProximityHat, which uses pressure actuators around the head to convey spatial information. It was already shown that the sense of touch can be used to augment our perception of reality. Existing systems focus on vibration signals for information transfer, but this is unsuitable for constant stimulation in everyday use. Our system determines the distance to surrounding objects with ultrasonic sensors and maps this information to an inward pressure. It was evaluated in a study with 13 blindfolded subjects in orientation and navigation tasks. The users were able to discern at least three different absolute pressure levels with high certainty. Combined with the sensors, they could also use continuous values to navigate hallways and find doors. Most users had only a few collisions, but a small group of three individuals struggled more. We attribute this to the latency and resolution of the final prototype, which led to slow walking speed and will be addressed in future work.

A flexible architecture for a robust indoor navigation support device for firefighters

In harsh indoor environments like in a firefighter operation location technologies would help to reduce casualties. However, exact indoor localization is still a research topic. We aim to create a wireless sensor network based ad hoc system which builds on the existing navigational skills of firefighters. Allowing them to shape the system as it best fits the actual operation will enhance efficiency at affordable costs. Such a system could provide the advantages of a fixed infrastructure independent of the place of action. In this paper we first analyze the architectural requirements of such a system. Second, we present a corresponding three layered system design which is comprised of network, data management and data storage layer. Third, an implementation of the architecture is presented. Fourth, a prototype implementation of the system and finally, a report on the system evaluation is given. The designed architecture is a promising approach towards a robust and flexible indoor navigation support device for firefighters.