Matthias Gauger

FlexCup: a flexible and efficient code update mechanism for sensor networks

The ability to update the program code installed on wireless sensor nodes plays an import role in the highly dynamic environments sensor networks are often deployed in. Such code update mechanisms should support flexible reconfiguration and adaptation of the sensor nodes but should also operate in an energy and time efficient manner. In this paper, we present FlexCup, a flexible code update mechanism that minimizes the energy consumed on each sensor node for the installation of arbitrary code changes. We describe two different versions of FlexCup and show, using a precise hardware emulator, that our mechanism is able to perform updates up to 8 times faster than related code update algorithms found in the literature, while consuming only an eighth of the energy.

The Family Video Archive: an annotation and browsing environment for home movies

We present the Family Video Archive as a tool to give consumers the ability to annotate and browse large collections of informal family movies. The informal nature of home movies makes it difficult to use fully-automated techniques for scene detection and annotation. Our system explores the symbiosis between automated and manual techniques for annotation. We also explore the use of a zooming interaction paradigm for browsing and filtering large collections of video scenes.

On boundary recognition without location information in wireless sensor networks

Boundary recognition is an important and challenging issue in wireless sensor networks when no coordinates or distances are available. The distinction between inner and boundary nodes of the network can provide valuable knowledge to a broad spectrum of algorithms. This article tackles the challenge of providing a scalable and range-free solution for boundary recognition that does not require a high node density. We explain the challenges of accurately defining the boundary of a wireless sensor network with and without node positions and provide a new definition of network boundary in the discrete domain. Our solution for boundary recognition approximates the boundary of the sensor network by determining the majority of inner nodes using geometric constructions, which guarantee that for a given d, a node lies inside of the construction for a d-quasi unit disk graph model of the wireless sensor network. Moreover, such geometric constructions make it possible to compute a guaranteed distance from a node to the boundary. We present a fully distributed algorithm for boundary recognition based on these concepts and perform a detailed complexity analysis. We provide a thorough evaluation of our approach and show that it is applicable to dense as well as sparse deployments.

On Boundary Recognition without Location Information in Wireless Sensor Networks

Boundary recognition is an important and challenging issue in wireless sensor networks when no coordinates or distances are available. The distinction between inner and boundary nodes of the network can provide valuable knowledge to a broad spectrum of algorithms. This paper tackles the challenge of providing a scalable and range-free solution for boundary recognition that does not require a high node density. Our solution approximates the boundary of the sensor network by determining the inner nodes using geometric constructions that guarantee that, for a given d, a node lies inside of the construction for a d-quasi unit disk graph model of the wireless sensor network. Moreover, such geometric constructions make it possible to compute a guaranteed distance from a node to the boundary. We provide a thorough evaluation of our approach and show that it is applicable to dense as well as sparse deployments.

Prototyping sensor-actuator networks for home automation

Integrating actuators into sensor networks is often considered to be the next logical step in the evolution of wireless sensor networks. However, few practical examples of such sensor and actuator networks have been demonstrated so far. In this paper, we present a prototype system that supports the easy prototyping of such applications in the area of home automation. We demonstrate the utility of this system with a simple light control application built on top of it. We also report first experiences and insights gained with the help of real-world experiments.

Removing the memory limitations of sensor networks with flash-based virtual memory

Virtual memory has been successfully used in different domains to extend the amount of memory available to applications. We have adapted this mechanism to sensor networks, where, traditionally, RAM is a severely constrained resource. In this paper we show that the overhead of virtual memory can be significantly reduced with compile-time optimizations to make it usable in practice, even with the resource limitations present in sensor networks. Our approach, ViMem, creates an efficient memory layout based on variable access traces obtained from simulation tools. This layout is optimized to the memory access patterns of the application and to the specific properties of the sensor network hardware. Our implementation is based on TinyOS. It includes a pre-compiler for nesC code that translates virtual memory accesses into calls of ViMems runtime component. ViMem uses flash memory as secondary storage. In order to evaluate our system we have modified nontrivial existing applications to make use of virtual memory. We show that its runtime overhead is small even for large data sizes.

TinyXXL: Language and Runtime Support for Cross-Layer Interactions

In the area of wireless sensor networks, cross-layer interactions are often preferred to strictly layered architectures. However, architectural properties such as modularity and the reusability of components suffer from such optimizations. In this paper we present TinyXXL that provides programming abstractions for data exchange, a form of cross-layer interaction with a large potential for optimizations. Our approach decouples components providing and using data, and it allows for automatic optimizations of applications composed of reusable components. Its runtime representation is efficient regarding memory consumption and processing overhead

Versatile support for efficient neighborhood data sharing

Many applications in wireless sensor networks rely on data from neighboring nodes. However, the effort for developing efficient solutions for sharing data in the neighborhood is often substantial. Therefore, we present a general-purpose algorithm for this task that makes use of the broadcast nature of radio transmission to reduce the number of packets. We have integrated this algorithm into TinyXXL, a programming language extension for data exchange. This combined system offers seamless support both for data exchange among the components of a single node and for efficient neighborhood data sharing. We show that compared to existing solutions, such as Hood, our approach further reduces the work of the application developer and provides greater efficiency.

Enlighten me! secure key assignment in wireless sensor networks

The availability of secret keys is a precondition for the use of many security solutions and protocols. However, securely assigning such keys to nodes is a challenging task in the context of wireless sensor networks. In this paper we present a novel solution for a secure key assignment in wireless sensor networks that can be used during the initial configuration of nodes or for an ad-hoc key assignment by mobile nodes. The idea is to transmit the key information over a side channel using a controllable light source as the sender and the light sensors available on wireless sensor nodes as receivers. We demonstrate that our solution fulfills the relevant security requirements while at the same time being cost effective and easy to use.

TinyModules: Code module exchange in TinyOS

The ability to update or exchange the program code running on sensor nodes is a core requirement in many wireless sensor network scenarios. Such code update mechanisms must take the specific resource limitations of wireless sensor nodes into account since both the transmission and the processing of updates consume considerable amounts of time and energy. We present TinyModules, a novel code update mechanism for TinyOS-based sensor networks whose idea is to divide the program code into a static part and an exchangeable TinyModule. TinyModules is highly configurable with the system developer being able to freely define which parts of the application should be exchangeable. We show that the use of TinyModules can achieve considerable savings in terms of code update size and update time with only negligible additional processing required on the nodes.