[show abstract][hide abstract] ABSTRACT: A lot of applications for wireless sensor networks have been proposed in the last years. Only a few of them have led to real, non-academic deployments, partially due to the differences between end user needs and academic assumptions. In this paper we discuss a real world problem arising from an ecological question (protection of an endangered species) and the theoretical solution as well as the deployed solution that actually works.
IEEE 36th Conference on Local Computer Networks, LCN 2011, Bonn, Germany, October 4-7, 2011; 01/2011
[show abstract][hide abstract] ABSTRACT: Communication neighborhood in wireless sensor networks changes often as links break or appear. Therefore, monitoring link
quality and (logical) network topology is necessary. As node placement has a large influence on the radio neighborhood and
its changes, different positions should be evaluated before starting the actual application.
In this paper we introduce Sensorium, an active monitoring system that supplies the user with an insight into the neighborhood relations between nodes and their
changes in time. It can be used before the actual deployment to evaluate different possibilities of node placement and choose
the one that offers the best connectivity.
Ad Hoc Networks - Second International Conference, ADHOCNETS 2010, Victoria, BC, Canada, August 18-20, 2010, Revised Selected Papers; 01/2010
[show abstract][hide abstract] ABSTRACT: Unidirectional links are a common property of all wireless networks. In many cases, the range of these links exceeds that of bidirectional links by far. Still, most protocols ignore their existence or simply discard them. In this paper we introduce two new medium access control (MAC) protocols called MLMAC-UL and ECTS-MAC that are able to transmit data over unidirectional links and receive acknowledgment messages for them using a neighborhood discovery protocol. Both protocols, as well as two reference protocols, were evaluated in simulations and using a real sensor network consisting of TMote Sky sensor nodes.
Sensor Technologies and Applications, 2009. SENSORCOMM '09. Third International Conference on; 07/2009
[show abstract][hide abstract] ABSTRACT: Energy consumption is a crucial factor for the lifetime of many embedded systems, especially wireless sensor networks. Most
modern microcontrollers provide various low power sleep modes. Utilizing them can lead to great energy savings. In this paper
we present an approach for power management in embedded systems, based on the event-driven operating system Reflex. The implicit power management is mostly hardware independent, lightweight and efficiently chooses the optimal power saving
mode of the microprocessor automatically.
Wired/Wireless Internet Communications, 7th International Conference, WWIC 2009, Enschede, The Netherlands, May 27-29, 2009. Proceedings; 01/2009
[show abstract][hide abstract] ABSTRACT: Experiments with wireless sensor networks have shown that unidirectional communication links are quite common. What is even more, they have also shown that the range of a unidirectional link can exceed that of a bidirectional one by far. Still, most of todays routing protocols do not use them, they only eliminate their implications. Those protocols that do use unidirectional links introduce a lot of protocol over- head. In this paper we present Buckshot Routing, a robust, yet simple source routing protocol for dense wireless networks with lossy or unidi- rectional links, which reduces the overhead generated by route discovery and route maintenance signicantly.
Ad Hoc Networks, First International Conference, ADHOCNETS 2009, Niagara Falls, Ontario, Canada, September 22-25, 2009. Revised Selected Papers; 01/2009
[show abstract][hide abstract] ABSTRACT: Today, even small residential buildings have a number of complex electrical devices that advocate the usage of automated control systems. But currently available systems are either hard to handle or expensive. This paper describes an automated house control system that has been in use for the last 4 years. It has been built using only freely available, inexpensive hardware and the open source operating system REFLEX.
Emerging Technologies and Factory Automation, 2008. ETFA 2008. IEEE International Conference on; 10/2008
[show abstract][hide abstract] ABSTRACT: typically cheap devices offering low bandwidth communication only. When physical events in the real world trigger spontaneous communication in many nodes the single communication channel is under heavy load and many messages are lost due to collisions. CSMA/CA schemes are well suited to spontaneous communica- tion, but do not provide a high channel utilization under heavy load. TDMA protocols have some conceptual advantage here, but in the case of mobile sensor nodes they need to be adaptive and establish TDMA schedules on demand. MLMAC is a novel TDMA based MAC protocol that can react on changing radio neighborhoods in mobile networks. In this paper we introduce the MLMAC protocol and present the results of real experiments with a group of mobile sensor nodes based on RCX robots.
Sensor Technologies and Applications, 2007. SensorComm 2007. International Conference on; 11/2007
[show abstract][hide abstract] ABSTRACT: COCOS (coordinated communicating sensors) is a lean middleware platform for wireless sensor networks. The major programming abstractions of Cocos are distributed sensor spaces. All objects in such a space can be collectively addressed. This way, high-level data-parallel programming concepts such as global reductions are possible. This paper introduces the spaces of Cocos and describes their usage.
[show abstract][hide abstract] ABSTRACT: Cocos (COordinated COmmunicating Sensors)1 is a lean middleware platform for wireless sensor and actuator net- works. The major programming abstractions of Cocos are distributed sensor spaces, which enable the collective con- trolling of sensors or actuators on remote nodes. Thus, Co- cos brings high-level data-parallel programming concepts such as global reductions into the world of small networked systems. In this paper we discuss the design rationale of Cocos as well as its in-network processing and aggregation capabilities.
Proceedings of the First ACM Workshop on Sensor and Actor Networks, SANET 2007, Montréal, Québec, Canada, September 10, 2007; 01/2007
[show abstract][hide abstract] ABSTRACT: Deeply embedded systems become more and more im- portant in everyday life. As the number of systems increases, the demand for programming platforms, which help with handling non-functional properties like synchronization, grows. Using the event-flow principle for programming leads to implicit synchro- nization for the application programmer's point of view and al- lows efficient explicit synchronization. We show the internals for implicit synchronization and propose efficient mechanisms for synchronization in event-driven systems. The implementation is written for our runtime environment for deeply embedded sys- tems REFLEX (Real-Time Event Flow Executive).
[show abstract][hide abstract] ABSTRACT: Reflex is a generic event driven OS for embedded devices. Event handlers and control functions are all represented by passive ob-jects that are scheduled preemptively according to an earliest deadline first (EDF) strategy. The synchronization of events is based on an event flow model similar to the data flow paradigm. In this paper we will present the design rationale of Reflex and particularly discuss the lan-guage level aspects of our approach.
[show abstract][hide abstract] ABSTRACT: Experiments have shown that unidirectional links are quite common in wireless sensor networks. Still, many MAC protocols ignore their existence, even though they have a tremendous impact on the performance of both TDMA-and contention based protocols. In contention based protocols the medium may be assumed free when it is indeed busy. In TDMA based protocols two neighboring nodes might get assigned the same slot even though there is an unidirectional link between them. In this paper we discuss the influence of unidirectional links on communication protocols in wireless sensor networks, focusing on MAC protocols. We also present two protocols that do not only eliminate the negative side effects of unidirectional links, but use them for message transmission as well.