Jan Beutel

FlockLab: a testbed for distributed, synchronized tracing and profiling of wireless embedded systems

Testbeds are indispensable for debugging and evaluating wireless embedded systems. While existing testbeds provide ample opportunities for realistic, large-scale experiments, they are limited in their ability to closely observe and control the distributed operation of resource-constrained nodes-access to the nodes is restricted to the serial port. This paper presents FlockLab, a testbed that overcomes this limitation by allowing multiple services to run simultaneously and synchronously against all nodes under test in addition to the traditional serial port service: tracing of GPIO pins to record logical events occurring on a node, actuation of GPIO pins to trigger actions on a node, and high-resolution power profiling. FlockLabs accurate timing information in the low microsecond range enables logical events to be correlated with power samples, thus providing a previously unattained level of visibility into the distributed behavior of wireless embedded systems. In this paper, we describe FlockLabs design, benchmark its performance, and demonstrate its capabilities through several real-world test cases.

Prototyping Wireless Sensor Network Applications with BTnodes

We present a hardware and software platform for rapid prototyping of augmented sensor network systems, which may be temporarily connected to a backend infrastructure for data storage and user interaction, and which may also make use of actuators or devices with rich computing resources that perform complex signal processing tasks. The use of Bluetooth as the wireless networking technology provides us with a rich palette of Bluetooth-enabled commodity devices, which can be used as actuators, infrastructure gateways, or user interfaces. Our platform consists of a Bluetooth-based sensor node hardware (the BTnode), a portable operating system component, and a set of system services. This paper gives a detailed motivation of our platform and a description of the platform components. Though using Bluetooth in wireless sensor networks may seem counter-intuitive at first, we argue that the BTnode platform is indeed well suited for prototyping applications in this domain. As a proof of concept, we describe two prototype applications that have been realized using the BTnodes.

Sensing the air we breathe: the opensense Zurich dataset

Monitoring and managing urban air pollution is a significant challenge for the sustainability of our environment. We quickly survey the air pollution modeling problem, introduce a new dataset of mobile air quality measurements in Zurich, and discuss the challenges of making sense of these data.Molecular oxygen (O 2 )is a basic requirement for cellular growth and viability and many aspects of anatomy and physiology are dedicated to achieving reliable distribution. Recent work has identified a specific sensing and response system, centred around a transcription complex called Hypoxia-inducible Factor 1 (HIF-1), which forms the focus of this review. The HIF-system operates in all cell types and modulates a very broad range of cellular pathways, consistent with the broad importance of oxygen. It is implicated in a rapidly expanding range of developmental, physiological and pathological settings, and is potentially relevant to almost all areas of clinical medicine. Excitingly, the pathway can be activated with low molecular weight compounds which should offer therapeutic benefit, especially in diseases where oxygen supply is compromised.

A systematic approach to the design of distributed wearable systems

Wearable computing has recently gained much popularity as an ambitious vision for future personalized mobile systems. Its aim is intelligent, environment aware systems unobtrusively embedded into the mobile environments of their users. With the combination of complex processing requirements, the necessity of placing sensors and input/output modules at different locations on the users body, and stringent limits on size, weight, and battery capacity, the design of such systems is an inherently challenging problem. We demonstrate how systematic design and quantitative analysis can be applied to wearable architectures. We first present a model that allows various factors influencing the design of a wearable system to be incorporated into formal cost metrics. In particular, we show how to consistently incorporate specific wearable factors such as device placement requirements, ergonomics, and dynamic workload profiles into the model. We then discuss how efficient estimation algorithms can be extended and applied to the evaluation of different architectures with respect to our cost metrics. Finally, we discuss quantitative results from a proof-of-concept case study showing the trade offs between different architectures for a given wearable scenario. Summarized, we demonstrate how the description and the design of wearable systems can be put on a systematic, formal basis allowing us to treat them similar as conventional embedded systems.

Next-generation prototyping of sensor networks

Large-scale deployment of sensor networks is more and more becoming an issue to researchers and industry alike. The recently revised BTnode architecture provides two wireless radios and facilitates the interconnection of heterogeneous devices. Apart from offering interesting new opportunities in using multi-frontend devices in sensor-network research, this architecture is optimally suited for deployment-support networks as introduced in the following.

GPS-Equipped wireless sensor network node for high-accuracy positioning applications

This work presents the design, implementation, and end-to-end system concept and integration of a wireless data acquisition system for high-accuracy positioning applications. A wireless network of GPS-equipped sensor nodes, built from low-cost off-the-shelf components, autonomously acquires L1 GPS data for Differential GPS (DGPS) processing of raw satellite information. The differential processing on the backend infrastructure achieves relative position and motion of individual nodes within the network with sub-centimeter accuracy. Leveraging on global GPS time synchronization, network-wide synchronized measurement scheduling, and duty-cycling coupled with power optimized operation and robustness against harsh environmental conditions make the introduced sensor node well suited for monitoring or surveying applications in remote areas. Unattended operation, high spatial and temporal coverage and low cost distinguish this approach from traditional, very costly and time consuming approaches. The prototype data acquisition system based on a low-power mote equipped with a commercially available GPS module has been successfully implemented and validated in a testbed setting.

Deployment Techniques for Sensor Networks

The prominent visions of wireless sensor networks that appeared about a decade ago have spurred enormous efforts in research and development of this new class of wireless networked embedded systems. Despite the significant effort made, successful deployments and real-world applications of sensor networks are still scarce, labor-intensive and often cumbersome to achieve. In this article, we survey prominent examples of sensor network deployments, in particular for environmental monitoring applications, their interaction with the real world and classify a number of potential causes for errors and common pitfalls. In the second half of this work, we present methods and tools to be used to detect failures, identify and understand root causes. These instrumentation techniques and analysis tools are specifically designed or adapted for the analysis of distributed networked embedded systems at the level of components, sensor nodes, and networks of nodes.

Fast-prototyping Using the BTnode Platform

The BTnode platform is a versatile and flexible platform for functional prototyping of ad hoc and sensor networks. Based on an Atmel microcontroller, a Bluetooth radio and a low-power ISM hand radio it offers ample resources to implement and test a broad range of algorithms and applications ranging from pure technology studies to complete application demonstrators. Accompanying the hardware is a suite of system software, application examples and tutorials as well as support for debugging, test, deployment and validation of wireless sensor network applications. We discuss aspects of system design, development and deployment based on our experience with real wireless sensor network experiments. We further discuss our approach of a deployment-support network that tries to close the gap between current proof-of-concept experiments to sustainable real-world sensor network solutions

The case for reconfigurable hardware in wearable computing

Wearable computers are embedded into the mobile environment of their users. A design challenge for wearable systems is to combine the high performance required for tasks such as video decoding with the low energy consumption required to maximise battery runtimes and the flexibility demanded by the dynamics of the environment and the applications. In this paper, we demonstrate that reconfigurable hardware technology is able to answer this challenge. We present the concept and the prototype implementation of an autonomous wearable unit with reconfigurable modules (WURM). We discuss experiments that show the uses of reconfigurable hardware in WURM: ASICs-on-demand and adaptive interfaces. Finally, we present an experiment with an operating system layer for WURM.

X-SENSE: Sensing in extreme environments

The field of Wireless Sensor Networks (WSNs) is now in a stage where serious applications of societal and economical importance are in reach. For example, it is well known that the global climate change dramatically influences the visual appearance of mountain areas like the European Alps. Very destructive geological processes may be triggered or intensified, impacting the stability of slopes, possibly inducing landslides. Unfortunately, the interactions between these complex processes is poorly understood. Therefore, one needs to develop wireless sensing technology as a new scientific instrument for environmental sensing under extreme conditions. Large variations in temperature, humidity, mechanical forces, snow coverage, and unattended operation play a crucial role in long-term deployments. We argue that, in order to significantly advance the application domain, it is inevitable that sensor networks be created as a quality scientific instrument with known and predictable properties, and not as a research toy delivering average observations at best. In this paper, key techniques for achieving highly reliable, yet resource efficent wireless sensor networks are discussed on the basis of productive wireless sensor networks measuring permafrost processes in the Swiss Alps.