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Item type:Publication, Access status: without files , Analysis of Temperature Effects in Heterogeneous Outdoor Wireless Sensor Networks(2022-10); ; ; Outdoor Wireless Sensor Networks introduce harsh conditions and challenges in terms of reliability. Previous work demonstrates a severe dependency on temperature within networks. However, such studies are limited as they only focus homogeneous networks. Extensive, systematic experiments are still missing, but are required to harden such deployments. In this paper, we conduct two experiments to analyse the effect of temperature. Our first, real-world deployment shows similar results and indicates a node-dependent behavior. For further investigation, a systematic experiment analyses the effects with focus on heterogeneous networks. To the best of our knowledge, we are the first, to analyse the effect in such a way. Our results indicate an even stronger relationship between pairs of nodes. We present key findings and believe that will serve as a starting point for other investigations in this direction, to enable reliable large-scale network deployments.Publicationtype: Conference Paper17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Towards Accurate Bit Error Simulation in Wireless Sensor Networks Including Environmental Influences(2020-07-01); ; ; Simulation is a common technique for the evaluation of new approaches and protocols in networked systems and provides many benefits. However, it is also well known that the relevance of the simulation results for real-world applications depends on the various models which are used within the simulation, e.g., for the characteristics of the radio communication. In this paper, we introduce the Extended Multipath Raytracing Model, an extension to the ray-tracing radio medium available in Cooja, to improve the modelling of wireless links in simulated Wireless Sensor Networks. Our extension allows the simulation of environmental influences onto links on a per node basis, allowing the analysis of various effects observed in experiments in a virtual environment. Furthermore, the packet-based modelling of transmission errors is extended to provide the simulation of bit errors, allowing new usage scenarios, like the simulation of error detection and Forward Error Correction codes in Cooja.Publicationtype: Journal Article20 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , DUO: Integration of dependable undervolting in operating systems(2019-11-10); ; ; DUO is a co-processor-based energy harvesting solution that integrates the existing undervolting approach IdealVolting into the RIOT operating system. By integrating the existing approach into an operating system, the benefits of undervolting can be used in regular applications. The user can use IdealVolting along with existing applications and take advantage of an active undervolting approach. Especially in energy harvesting applications, that already use an energy harvesting chip with adjustable output voltage, the approach can be easily integrated. Our evaluation compares a duty-cycle sample application within RIOT OS with and without IdealVolting. It shows that DUO can save up to 20 % compared to the plain application only by adding IdealVolting to the application. Our poster highlights important aspects of our implementation and motivates the benefits of a co-processor in such a system.Publicationtype: Conference Paper44 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Towards accurate bit error simulation in wireless sensor networks including environmental influences(2019-11); ; ; Simulation is a common technique for the evaluation of new approaches and protocols in networked systems and provides many benefits. However, it is also well known that the relevance of the simulation results for real-world applications depends on the various models which are used within the simulation, e.g., for the characteristics of the radio communication. In this paper, we introduce the EMRM, an extension to the ray-tracing radio medium available in Cooja, to improve the modelling of wireless links in simulated WSNs. Our extension allows the simulation of environmental influences onto links on a per node basis, allowing the analysis of various effects observed in experiments in a virtual environment. Furthermore, the packet-based modelling of transmission errors is extended to provide the simulation of bit errors, allowing new usage scenarios, like for instance the simulation of error detection and FEC codes in Cooja.Publicationtype: Conference Paper22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A feasibility study on energy harvesting from soil temperature differences(Association for Computing Machinery (ACM), 2018-11-04); ; ; With regard to the growing number of wireless sensor network (WSN) and IoT longterm applications, energy harvesting becomes more and more popular i.a. due to the economical advantages compared to classical energy sources. Outdoor deployments for e.g. smart farming applications usually rely on solar-powered harvesters but this is not sufficient in any case. During previous outdoor deployments we observed, that soiling or shadowing by plants makes solar cells infeasible for ground-level sensors. We also observed that thermoelectric generators (TEGs) might be an alternative when utilizing the temperature gradient between the ground and the soil. Hence, this paper presents a longterm measurement as well as a feasibility study whether a WSN could be supplied by this approach. We collected and analysed data of more than a year and show the total amount as well as the characteristics of harvestable energy. Finally a load model of a typical WSN application is used to evaluate its performance and, therefore, to prove that energy harvesting from soil temperature differences is a realistic solution to power nodes and networks.Publicationtype: Conference Paper33 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A flexible software framework for real-world experiments and temperature-controlled testbeds(Association for Computing Machinery (ACM), 2018-10-01); ; ; Both reliability and robustness are required for applications in the field of wireless sensor networks and the internet of things. Testbeds are a usefool tool to verify both hardware and software concepts under realistic conditions. However, existing testbeds often are fitted to specific use cases. This paper presents a software framework to build testbeds for various applications and scenarios. The module architecture of our framework approach is presented in detail. Communication is based on MQTT which fulfills both the need to be flexible, but also to scale well for larger testbeds. Key requirements are derived from our existing use cases, an outdoor scenario and an indoor, temperature-controlled testbed. We present our temperature-controlled chambers in detail and compare their performance to existing testbeds.Publicationtype: Conference Paper31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Poster abstract: Towards realistic lifetime estimation in battery-powered IoT devices(Association for Computing Machinery (ACM), 2017-11-06); ; ; ; We describe a testbed for studying battery discharge behavior and the lifetime of wireless devices under controlled temperature con ditions and present preliminary measurement results.Publicationtype: Conference Paper34 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the experiences with testbeds and applications in precision farming(Association for Computing Machinery (ACM), 2017-11-05); ; ; ; While success stories are likely to be reported, failures are rarely published - even if a lot can be learned from them. In this paper we present experiences and findings from our testbed and WSN deployments. Our PotatoNet has been deployed on an agricultural area in 2015 to perform several WSN outdoor experiments while measuring the stress of potato crops. It was extended a year later by the PotatoMesh, a solar panel-based mesh network of nodes. Throughout both of these deployments we experienced problems and failures at different stages of the projects. We derive key problems and some important concepts when it comes to outdoor WSN deployments.Publicationtype: Conference Paper22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Demo: PotatoScope - scalable and dependable distributed energy measurement for WSNsThis demo paper describes the usability and effectiveness of our distributed energy measurement system for WSNs. The system is composed of several micro-controller-based oscilloscopes - named PotatoScope. The intention of PotatoScope was to enable a scalable and dependable energy measurement for challenging environmental conditions, e.g., WSN outdoor deployments. We will present the general architecture by using two of our nodes and demonstrate how to measure energy consumption of nodes in our testbed. Certainly, the PotatoScope can be used standalone to measure energy comsumption of other devices, such as other micro controllers or single-board computers, e.g. Raspberry Pis. The demo will introduce a GUI, that displays information directly on a computer. Both the PotatoScope, including the hardware layout and the firmware, as well as the distributed energy measurement system is free to be used in own projects.Publicationtype: Conference Paper25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Distributed energy measurement in WSNs for outdoor applicationsEnergy is one of the most critical resources in Wireless Sensor Networks (WSN). For any WSN deployment, being it for a productive use case or for a testbed, the ability to perform energy measurements is of major importance, e.g., to estimate the status of the WSN, the need for maintenance, or for remaining lifetime. This paper presents a distributed energy measurement system for outdoor applications. An existing testbed has been extended by the micro controller unit (MCU)- based oscilloscope PotatoScope. Measuring voltage and current of the sensor node, undervolting effects and energy consumption of realtime applications can be observed. The PotatoScope is capable of capturing the power dissipation precisely at a high temperature range of 100 K. Using high sample rates with up to 500 kHz, the system needs to be capable of storing and archiving the measured data. A final evaluation shows a 0.9% drift for voltage measurements and a 1.6% drift for current measurements over the range of 100K. Using an SD card, long-term measurements can be made with up to 500 kHz. Nevertheless, a live mode allows sample rates up to 2 MHz when using the PotatoScope with a computer.Publicationtype: Conference Paper21